CN106099061A - A kind of porous graphene/silicon composite, its preparation method and lithium ion battery - Google Patents

Abstract

The invention provides a method for preparing a porous graphene/silicon composite material. Firstly, the graphene/silicon composite gel is prepared by hydrothermal treatment, and then dried to regulate the internal pore size of the graphene/silicon composite gel, and finally freeze-dried 1. Heat treatment to prepare porous graphene/silicon composite materials. This method can also enhance the bonding strength between silicon and graphene sheets while regulating the pore size of graphene/silicon composite materials, and prevent silicon and graphene from forming during charging and discharging. The exfoliation occurs between them, which ensures that the prepared porous graphene/silicon composite has high reversible capacity, good cycle performance and rate performance. Experiments show that the first discharge specific capacity of the lithium ion battery prepared by the invention is 1325-1785mAh/g at a rate of 0.5C, and after 200 cycles, the discharge specific capacity is 940-1600mAh/g.

Description

A kind of porous graphene/silicon composite material, its preparation method and lithium ion battery

technical field

The invention relates to the technical field of lithium ion batteries, in particular to a porous graphene/silicon composite material, a preparation method thereof and a lithium ion battery.

Background technique

Lithium-ion batteries have the advantages of high operating voltage, high specific energy, wide operating temperature range, stable discharge, small size, light weight, no memory effect, and environmental friendliness. Therefore, they are widely used in portable electronic devices, electric vehicles, space technology, and defense industries. and other fields have shown broad application prospects.

With the increasing demand for high-capacity and long-life batteries in mobile electronic devices, people have put forward higher requirements for the performance of lithium-ion batteries. As an important factor to improve the energy and cycle life of lithium-ion batteries, negative electrode materials are in the world. has been extensively studied.

In the early 1990s, Sony Corporation of Japan took the lead in developing carbon anode materials, which significantly improved the safety performance and charge-discharge cycle life of lithium-ion batteries. However, the theoretical specific capacity of carbon anode materials is only 372mAh/g, and its energy density can no longer meet the energy density requirements of various consumer electronic devices, especially energy storage devices and electric vehicles. Therefore, it is urgent to find a substitute for High energy density anode material of carbon material.

Among them, silicon-based anode materials have attracted much attention due to their huge lithium storage capacity (4200mAh/g), a slightly higher discharge platform than carbon materials, and abundant reserves in the earth's crust. However, during the charge and discharge process, the lithium-deintercalation reaction of silicon will be accompanied by a volume change of 310%, which will easily cause the cracking of the electrode and the shedding of the active material, and the formation of an unstable solid electrolyte interfacial film (SEI film), resulting in electrode Deterioration of cycle performance and rate performance. In addition, the lower electronic conductivity and lithium ion migration rate of silicon materials also seriously affect the electrochemical performance of silicon anode materials.

One of the approaches to solve the above problems is to synthesize silicon-based composites to buffer the volume expansion of the electrodes and improve the cycling stability of the electrodes. Carbon materials have become the most widely selected materials due to their excellent electrical conductivity and mechanical properties. Synthesizing carbon materials and silicon composite materials can not only effectively buffer the volume expansion and prevent the aggregation of silicon nanoparticles, but also improve the conductivity of the electrode and obtain a stable SEI film, thereby greatly improving the cycle performance and Coulombic efficiency of the silicon anode. Among them, graphene has become the best active matrix for silicon-carbon anode materials due to its excellent flexibility, good electronic conductivity, low density, and appropriate lithium intercalation ability.

Chinese patent CN201010256875.X mixes different proportions of graphene oxide and nano-silicon powder, ultrasonically disperses, and finally suction-filters or directly dries into a cake/film to prepare a graphene/silicon composite film material with a self-supporting structure. Although silicon particles can be uniformly dispersed in the graphene flakes, it has a certain buffering effect on the volume expansion of silicon. However, the bonding strength between silicon and graphene is not high, the interstitial space is small, and the structure separation is easy to occur during the volume expansion and contraction of silicon, making it difficult to obtain better cycle performance.

Contents of the invention

In view of this, the technical problem to be solved in the present invention is to provide a kind of porous graphene/silicon composite material, its preparation method and lithium ion battery, the porous graphene/silicon composite material made by this preparation method has better cycle performance.

The invention provides a kind of preparation method of porous graphene/silicon composite material, comprises the following steps:

A1) mixing the aqueous solution of graphene oxide, nano silicon powder, deionized water, surfactant and organic solvent to obtain a mixed solution;

B) the mixed solution is subjected to a hydrothermal reaction to obtain a graphene/silicon composite gel;

C1) drying the graphene/silicon composite gel at normal pressure, 30°C-90°C for 0.5-7h, then freeze-drying and heat-treating to obtain a porous graphene/silicon composite material;

or

A2) mixing the aqueous solution of graphene oxide, nano silicon powder, deionized water and surfactant to obtain a mixed solution;

B) the mixed solution is subjected to a hydrothermal reaction to obtain a graphene/silicon composite gel;

C2) drying the graphene/silicon composite gel at 0.5 to 5 atmospheres at 30° C. to 90° C. for 0.5 to 7 hours, and then performing freeze drying and heat treatment to obtain a porous graphene/silicon composite material.

Preferably, the mass concentration of the graphene oxide aqueous solution is 0.5 mg/mL˜7 mg/mL.

Preferably, the mass ratio of nano-silica powder to graphene oxide is 1:6-5:1, the mass ratio of nano-silica powder to surfactant is 1:10-10:1, and the deionized water The volume ratio of the organic solvent to the organic solvent is 1:6˜6:1, and the volume ratio of the organic solvent to the aqueous solution of graphene oxide is 1:6˜6:1.

Preferably, the organic solvent is selected from one of ethanol, ethylene glycol or glycerol.

Preferably, in step A2), the mass ratio of nano silicon powder to graphene oxide is 1:6 to 5:1, and the mass ratio of nano silicon powder to surfactant is 1:10 to 10:1, so The volume ratio of the deionized water to the aqueous solution of graphene oxide is 1:6˜6:1.

Preferably, the temperature of the hydrothermal reaction is 100°C-200°C, and the time of the hydrothermal reaction is 2h-15h.

Preferably, in step C2), the graphene/silicon composite gel is dried at 30° C. to 90° C. for 0.5 to 7 hours at 0.7 to 0.9 atmospheres or 1.5 to 3 atmospheres, and then freeze-dried and heat-treated. A porous graphene/silicon composite material is obtained.

Preferably, the temperature of the heat treatment is 300°C-1000°C, and the time of the heat treatment is 1h-8h.

The invention provides a porous graphene/silicon composite material prepared by the above preparation method.

The present invention also provides a lithium ion battery, comprising a positive electrode, a negative electrode, a diaphragm and an electrolyte, and the negative electrode includes the porous graphene/silicon composite material mentioned above.

The invention provides a kind of preparation method of porous graphene/silicon composite material, comprises the following steps:

A1) mixing an aqueous solution of graphene oxide, nano-silica powder, deionized water, a surfactant and an organic solvent to obtain a mixed solution; B) subjecting the mixed solution to a hydrothermal reaction to obtain a graphene/silicon composite gel; C1) drying the graphene/silicon composite gel at normal pressure, 30°C-90°C for 0.5-7h, then freeze-drying and heat-treating to obtain a porous graphene/silicon composite material;

or

A2) mixing the aqueous solution of graphene oxide, nano silicon powder, deionized water and surfactant to obtain a mixed solution; B) carrying out a hydrothermal reaction to the mixed solution to obtain a graphene/silicon composite gel; C2) mixing The graphene/silicon composite gel is dried at 30° C. to 90° C. for 0.5 to 7 hours under 0.5 to 5 atmospheres, and then freeze-dried and heat-treated to obtain a porous graphene/silicon composite material.

When the present invention prepares the graphene/silicon composite gel, by adding an organic solvent in the raw material, then carry out the drying treatment at a specific temperature under normal pressure; or by controlling the air pressure and temperature of drying to control the graphene/silicon composite gel. The shrinkage rate of the silicon composite gel can be adjusted to obtain a graphene/silicon composite gel material with adjustable porosity and pore size, and then freeze-dried to solidify the structure of the graphene/silicon composite gel. The pore size of the porous graphene/silicon composite material prepared by the above method is controllable, the bonding strength between silicon and graphene is high, and the composite material with a porous structure has a large number of gaps, which can effectively accommodate the volume expansion of silicon without causing the composite material to be larger. volume change, and at the same time, a relatively stable SEI film can be obtained. In addition, the existence of pores can increase the reaction rate of deintercalating lithium, which is beneficial to improve the cycle performance and rate performance of the composite material, thereby ensuring that the prepared porous graphene/silicon composite material has better cycle performance and rate performance. Experiments show that the lithium-ion battery prepared by the present invention has a first discharge specific capacity of 1325-1785mAh/g at a rate of 0.5C, and after 200 cycles, a discharge specific capacity of 940-1600mAh/g, and a capacity retention rate of not less than 71 %.

Description of drawings

Fig. 1 is the SEM figure of the porous graphene/silicon composite material prepared by the embodiment of the present invention 1;

Fig. 2 is the SEM figure of the porous graphene/silicon composite material after grinding and pulverizing prepared by Example 1 of the present invention;

Fig. 3 is the cycle graph of the lithium ion battery prepared by the embodiment of the present invention 1～3;

Fig. 4 is the discharge specific capacity curve graph of the lithium-ion battery prepared in Examples 1-3 of the present invention at different rates;

Fig. 5 is the SEM picture of the porous graphene/silicon composite material that the embodiment of the present invention 2 prepares;

Fig. 6 is the SEM picture of the porous graphene/silicon composite material after grinding and pulverizing prepared by Example 2 of the present invention;

Fig. 7 is the SEM picture of the porous graphene/silicon composite material prepared by the embodiment of the present invention 3;

Fig. 8 is the SEM picture of the porous graphene/silicon composite material prepared in Example 3 of the present invention after being ground and pulverized;

Fig. 9 is the cycle graph of the lithium-ion battery prepared by Examples 9-11 of the present invention;

FIG. 10 is a graph showing specific discharge capacity curves of lithium-ion batteries prepared in Examples 9-11 of the present invention at different rates.

detailed description

The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

The invention provides a kind of preparation method of porous graphene/silicon composite material, comprises the following steps:

A1) mixing the aqueous solution of graphene oxide, nano silicon powder, deionized water, surfactant and organic solvent to obtain a mixed solution;

B) the mixed solution is subjected to a hydrothermal reaction to obtain a graphene/silicon composite gel;

C1) drying the graphene/silicon composite gel at normal pressure, 30°C-90°C for 0.5-7h, then freeze-drying and heat-treating to obtain a porous graphene/silicon composite material;

or

A2) mixing the aqueous solution of graphene oxide, nano silicon powder, deionized water and surfactant to obtain a mixed solution;

B) the mixed solution is subjected to a hydrothermal reaction to obtain a graphene/silicon composite gel;

C2) drying the graphene/silicon composite gel at 0.5 to 5 atmospheres at 30° C. to 90° C. for 0.5 to 7 hours, and then performing freeze drying and heat treatment to obtain a porous graphene/silicon composite material.

The preparation method of the porous graphene/silicon composite material provided by the present invention includes two schemes, by adding an organic solvent in the raw material to prepare a graphene/silicon composite gel, and then compounding the graphene/silicon at a specific temperature Gel drying; or by adjusting the drying pressure and temperature to control the shrinkage rate of the graphene/silicon composite gel, and then regulate the pore size of the composite gel and the thickness of the graphene sheet to improve the performance of silicon and graphene. degree of combination. Finally, a graphene/silicon composite material with a porous structure was obtained by freeze-drying and heat treatment. This composite material has a stable structure, excellent mechanical properties and electrical conductivity, and has good cycle performance and rate performance when used in lithium-ion batteries.

The above-mentioned first solution includes the following steps:

A1) mixing the aqueous solution of graphene oxide, nano silicon powder, deionized water, surfactant and organic solvent to obtain a mixed solution;

B) the mixed solution is subjected to a hydrothermal reaction to obtain a graphene/silicon composite gel;

C1) drying the graphene/silicon composite gel under normal pressure at 30° C. to 90° C. for 0.5 to 7 hours, then performing freeze drying and heat treatment to obtain a porous graphene/silicon composite material.

In the present invention, the graphene oxide is preferably prepared according to the Hummers method. After the graphene oxide is obtained, the present invention prepares it to obtain an aqueous solution of graphene oxide. The present invention has no special limitation on the preparation method of the aqueous solution of graphene oxide, and the preparation method of the aqueous solution well known to those skilled in the art can be used. In the present invention, the mass concentration of the aqueous solution of graphene oxide is preferably 0.5 mg/mL-7 mg/mL, more preferably 1 mg/mL-6 mg/mL.

After obtaining the aqueous solution of graphene oxide, the present invention mixes the aqueous solution of graphene oxide with nano silicon powder, deionized water, surfactant and organic solvent to obtain a mixed solution.

In the present invention, the surfactant is preferably a nonionic surfactant, more preferably polyvinylpyrrolidone (PVP), polydiene dimethyl ammonium chloride (PDDA) and polystyrene sulfonate sodium (PSS ) in one. The organic solvent is preferably ethanol, ethylene glycol or glycerol. The present invention uses ethanol as an organic solvent, and when drying at a specific temperature, the shrinkage rate of the graphene/silicon composite gel is relatively fast. The present invention uses ethylene glycol or glycerol as an organic solvent, and when drying at a specific temperature, the shrinkage rate of the graphene/silicon composite gel is relatively slow, and it is easier to control the pore size of the composite gel and the size of the graphene sheet. thickness.

The mass ratio of the nano-silica powder to graphene oxide is 1:6-5:1, preferably 1:5-3:1, more preferably 1:1; the mass ratio of the nano-silica powder to the surfactant 1:10-10:1, preferably 1:5-5:1, more preferably 2:1; the volume ratio of deionized water to organic solvent is 1:6-6:1, preferably 1: 5-5:1, more preferably 1:1; the volume ratio of the organic solvent to the aqueous solution of graphene oxide is 1:6-6:1, preferably 1:5-5:1, more preferably 1: 1.

The source of the raw material components used in the present invention is not particularly limited, and may be generally commercially available.

After the mixed solution is obtained, the present invention performs a hydrothermal reaction on the mixed solution to obtain a graphene/silicon composite gel. In the present invention, the temperature of the hydrothermal reaction is preferably 100°C-200°C; the time of the hydrothermal reaction is preferably 2h-15h.

In the present invention, the obtained graphene/silicon composite gel is dried under normal pressure at 30° C. to 90° C. for 0.5 to 7 hours to obtain the dried composite material. The drying time should not be too long, because if the drying time is too long, the graphene will be seriously agglomerated, thereby losing the spatial network structure. The present invention has no special limitation on the drying method, and the drying method known to those skilled in the art can be used.

Specifically, when the organic solvent used in the raw material is ethanol, the preferred drying temperature is 30°C to 70°C, and the drying time is 0.5 to 5 hours, and the more preferred drying temperature is 50°C to 60°C, and the drying time is 2 to 3.5 hours. When the selected organic solvent in the raw material is ethylene glycol or glycerol, the preferred drying temperature is 40°C-90°C, the drying time is 1-7h, and the more preferred drying temperature is 60°C-70°C. The drying time is 3-6 hours.

The dried composite material is freeze-dried to solidify the structure of the graphene/silicon composite gel. The freeze-drying temperature is preferably -70° C. to -10° C., and the freeze-drying time is preferably 1 h to 60 h.

The freeze-dried composite material is subjected to heat treatment to obtain a porous graphene/silicon composite material, preferably under an inert atmosphere. In the present invention, there is no special limitation on the heat treatment method, and the heat treatment method well known to those skilled in the art can be used, and the annealing treatment is preferably used in the present invention. The temperature of the heat treatment is preferably 300° C. to 1000° C., and the time of the heat treatment is preferably 1 h to 8 h. The present invention has no special limitation on the inert gas used to obtain the inert atmosphere, and the inert gas well known to those skilled in the art can be used. Argon is preferably used in the present invention.

The second option above includes the following steps:

A2) mixing the aqueous solution of graphene oxide, nano silicon powder, deionized water and surfactant to obtain a mixed solution;

B) the mixed solution is subjected to a hydrothermal reaction to obtain a graphene/silicon composite gel;

C2) drying the graphene/silicon composite gel at 0.5 to 5 atmospheres at 30° C. to 90° C. for 0.5 to 7 hours, and then performing freeze drying and heat treatment to obtain a porous graphene/silicon composite material.

In the present invention, the graphene oxide is preferably prepared according to the Hummers method. After the graphene oxide is obtained, the present invention prepares it to obtain an aqueous solution of graphene oxide. The present invention has no special limitation on the preparation method of the aqueous solution of graphene oxide, and the preparation method of the aqueous solution well known to those skilled in the art can be used. In the present invention, the mass concentration of the aqueous solution of graphene oxide is preferably 0.5 mg/mL-7 mg/mL, more preferably 1 mg/mL-6 mg/mL.

After obtaining the aqueous solution of graphene oxide, the present invention mixes the aqueous solution of graphene oxide with nano silicon powder, deionized water and surfactant to obtain a mixed solution.

In the present invention, the surfactant is preferably a nonionic surfactant, preferably polyvinylpyrrolidone (PVP), polydiene dimethyl ammonium chloride (PDDA), polystyrene sodium sulfonate (PSS) .

The mass ratio of the nano silicon powder to graphene oxide is 1:6 to 5:1, preferably 1:5 to 3:1, more preferably 1:1; the mass ratio of the nano silicon powder to the surfactant is 1:10-10:1, preferably 1:5-5:1, more preferably 2:1; the volume ratio of the deionized water to the aqueous solution of graphene oxide is 1:6-6:1, preferably 1:5 to 5:1, more preferably 1:1.

The source of the raw material components used in the present invention is not particularly limited, and may be generally commercially available.

After the mixed solution is obtained, the present invention performs a hydrothermal reaction on the mixed solution to obtain a graphene/silicon composite gel. In the present invention, the temperature of the hydrothermal reaction is preferably 100°C-200°C; the time of the hydrothermal reaction is preferably 2h-15h.

In the present invention, the obtained graphene/silicon composite gel is dried at a pressure greater than or equal to 0.5 and less than 1 atmosphere, or greater than or equal to 1 and less than or equal to 5 atmospheres, to obtain a dried composite material. The present invention has no special limitation on the drying method, and the drying method known to those skilled in the art can be used. The drying temperature is 30°C-90°C, and the drying time is 0.5h-7h.

Specifically, in the present invention, the obtained graphene/silicon composite gel is dried at a pressure greater than or equal to 0.5 and less than 1 atmosphere, preferably at a pressure of 0.7 to 0.9 atmospheres, and the shrinkage rate of the graphene/silicon composite gel is relatively fast. , the preferred drying temperature is 30°C-70°C, and the drying time is 0.5-5h; the more preferred drying temperature is 50°C-60°C, and the drying time is 2-3.5h. In the present invention, drying is carried out at a pressure greater than 1 and less than or equal to 5 atmospheres, preferably at a pressure of 1.5 to 3 atmospheres. The shrinkage rate of the graphene/silicon composite gel is relatively slow, and it is easier to control the pore size of the composite gel and graphene For the thickness of the sheet, the preferred drying temperature is 40°C-90°C, and the drying time is 1-7h; the more preferred drying temperature is 60°C-70°C, and the drying time is 3-6h.

The invention controls the shrinkage rate of the graphene/silicon composite gel by adjusting the drying air pressure and temperature, thereby regulating the pore size of the composite gel and the thickness of the graphene sheet, and improving the combination degree of silicon and graphene.

The dried composite material is freeze-dried to solidify the structure of the graphene/silicon composite gel. The freeze-drying temperature is preferably -70° C. to -10° C., and the freeze-drying time is preferably 1 h to 60 h.

The freeze-dried composite material is subjected to heat treatment to obtain a porous graphene/silicon composite material, preferably under an inert atmosphere. In the present invention, there is no special limitation on the heat treatment method, and the heat treatment method well known to those skilled in the art can be used, and the annealing treatment is preferably used in the present invention. The temperature of the heat treatment is preferably 300° C. to 1000° C., and the time of the heat treatment is preferably 1 h to 8 h. The present invention has no special limitation on the inert gas used to obtain the inert atmosphere, and the inert gas well known to those skilled in the art can be used. Argon is preferably used in the present invention.

The invention provides a porous graphene/silicon composite material prepared by the above preparation method. The porous graphene/silicon composite material provided by the present invention includes nano-silicon particles and graphene, and the nano-silicon particles are embedded between sheets of the graphene to form a composite material with a porous structure. The particle size of the nano-silicon particles is preferably 100nm-120nm. The present invention has no special limitation on the source of the nano-silicon, it can be made by itself or purchased from the market, and it only needs to meet the nano-size. The present invention preferably adopts the nano silicon powder of Aladdin Reagent Company.

In the porous graphene/silicon composite material provided by the present invention, the combination degree of nano-silicon particles and graphene is relatively high, and the pore diameter of graphene is not easy to be damaged in the later stage mixing process, which ensures the obtained negative electrode of lithium ion battery The cycle performance of the material makes the lithium-ion battery have better cycle performance.

The present invention also provides a lithium ion battery, comprising a positive electrode, a negative electrode, a diaphragm and an electrolyte, and the negative electrode includes the porous graphene/silicon composite material mentioned above.

The present invention does not have special limitation to the kind of described positive electrode, separator and electrolyte, as, described positive electrode can adopt lithium sheet; Described separator can adopt polypropylene microporous membrane; Described electrolyte can adopt ethylene carbonate (EC ) and dimethyl carbonate (DMC) mixture. Specifically, the present invention combines the above-mentioned porous graphene/silicon composite material with a binder (styrene-butadiene rubber (SBR): sodium carboxymethyl cellulose (CMC) = 3: 7 mass ratio), conductive agent Super P according to 80: Mix at a weight ratio of 10:10, add an appropriate amount of water as a dispersant to make a slurry, and then evenly coat it on the copper foil current collector, and vacuum-dry and roll to prepare a negative electrode sheet; use metal lithium as the counter electrode, A mixed solvent of 1 mol/L LiPF ₆ (EC:DMC=1:1 volume ratio) was used as the electrolyte, and a polypropylene microporous membrane (Celgard 2400) was used as the separator, and a simulated battery was assembled in an argon-protected glove box.

The present invention carries out constant current charging and discharging experiments on the obtained simulated battery to test the cycle performance of the lithium ion battery, the charging and discharging voltage is limited to 0.001-1.5 volts, and the charging and discharging current density is 500mA/g. The electrochemical performance of the battery was tested by a Land tester, and the test condition was room temperature. The experimental results show that the lithium-ion battery prepared by the present invention has a first discharge specific capacity of 1325-1785mAh/g at a rate of 0.5C, and after 200 cycles, the discharge specific capacity is 940-1600mAh/g, and the capacity retention rate is not less than 71%, with good cycle performance.

At the same time, the present invention also investigates the cycle performance of the obtained lithium-ion battery at different rates. The experimental results show that the lithium-ion battery provided by the present invention has relatively high performance at 0.1C, 0.2C, 0.5C, 1C and 2C. High specific capacity, good rate performance.

The invention provides a kind of preparation method of porous graphene/silicon composite material, comprises the following steps:

A1) mixing the aqueous solution of graphene oxide, nano silicon powder, deionized water, surfactant and organic solvent to obtain a mixed solution;

B) the mixed solution is subjected to a hydrothermal reaction to obtain a graphene/silicon composite gel;

C1) drying the graphene/silicon composite gel at normal pressure, 30°C-90°C for 0.5-7h, then freeze-drying and heat-treating to obtain a porous graphene/silicon composite material;

or

A2) mixing the aqueous solution of graphene oxide, nano silicon powder, deionized water and surfactant to obtain a mixed solution;

B) the mixed solution is subjected to a hydrothermal reaction to obtain a graphene/silicon composite gel;

C2) drying the graphene/silicon composite gel at 0.5 to 5 atmospheres at 30° C. to 90° C. for 0.5 to 7 hours, and then performing freeze drying and heat treatment to obtain a porous graphene/silicon composite material.

The present invention prepares the graphene/silicon composite gel by adding an alcoholic solvent to the raw material, and then dries the graphene/silicon composite gel at a specific temperature and normal pressure; or by adjusting the drying Air pressure and temperature control the shrinkage rate of the graphene/silicon composite gel to obtain a composite gel with adjustable pore size, and obtain a porous graphene/silicon composite material after subsequent freeze-drying and heat treatment. The composite material has a stable structure, excellent mechanical properties and electrical conductivity, high bonding strength between graphene and silicon, and has good cycle performance and rate performance when applied to lithium-ion batteries. The experimental results show that the lithium-ion battery prepared by the present invention has a first discharge specific capacity of 1325-1785mAh/g at a rate of 0.5C, and after 200 cycles, the discharge specific capacity is 940-1600mAh/g, and the capacity retention rate is not less than 71%, with good cycle performance.

In order to further illustrate the present invention, a kind of porous graphene/silicon composite material provided by the present invention, its preparation method and lithium ion battery are described in detail below in conjunction with the examples, but it should not be understood as limiting the protection scope of the present invention.

Example 1

The aqueous solution of graphene oxide is mixed with nano silicon powder, deionized water, polyvinylpyrrolidone and ethylene glycol (or glycerol) to obtain a mixed solution. Wherein, the mass concentration of the aqueous solution of graphene oxide is 6mg/mL, the mass ratio of described nano silicon powder and graphene oxide is 1: 1, the mass ratio of nano silicon powder and polyvinylpyrrolidone is 2: 1, deionized water The volume ratio with ethylene glycol (or glycerol) is 1:1, and the volume ratio of ethylene glycol (or glycerol) to the aqueous solution of graphene oxide is 1:1;

Put the mixed solution in a reaction kettle, and conduct a hydrothermal reaction at 180°C for 12 hours to obtain a graphene/silicon composite gel;

The graphene/silicon composite gel was dried at normal pressure at 60°C for 5 hours, then freeze-dried at (-60)°C for 48 hours, and finally annealed at 800°C for 4 hours under an inert atmosphere to obtain porous graphene/silicon composite material.

In the present invention, the obtained porous graphene/silicon composite material is subjected to scanning electron microscope scanning analysis, and the results are shown in FIGS. 1 and 2 . Fig. 1 is the SEM image of the porous graphene/silicon composite material prepared in Example 1 of the present invention, as can be seen from Fig. 1, the porous graphene/silicon composite material provided by the present invention has a porous structure. Fig. 2 is the SEM image of the sample after the porous graphene/silicon composite material obtained by the present invention is ground and pulverized, as can be seen from Fig. 2, the porous graphene/silicon composite material after grinding and pulverizing has a porous structure.

In the present invention, the above-mentioned porous graphene/silicon composite material is mixed with a binder (SBR:CMC=3:7 mass ratio), and a conductive agent Super P is mixed according to a weight ratio of 80:10:10, and an appropriate amount of water is added as a dispersant. The slurry is then evenly coated on the copper foil current collector, and is prepared into a negative electrode sheet through vacuum drying and rolling; with metal lithium as the counter electrode, the mixed solvent of 1mol/L LiPF ₆ (EC:DMC=1: 1 volume ratio) as the electrolyte, polypropylene microporous membrane (Celgard 2400) as the separator, and assembled into a simulated battery in an argon-protected glove box. The assembled simulated battery was subjected to a constant current charge and discharge test on a Land tester (Wuhan ^Xinnuo Electronics Co., Ltd.). The performance curve is shown in Figure 3.

Experimental results show that the first discharge specific capacity of the lithium ion battery provided by the invention is not less than 1785mAh/g at a rate of 0.5C, and after 200 cycles of charge and discharge, the capacity retention rate is not less than 89%, and has good cycle performance . It has good cycle performance.

At the same time, the present invention also investigates the discharge cycle performance of the obtained lithium ion battery at different rates, as shown in FIG. 4 . Experimental results show that the lithium ion battery provided by the present invention has higher specific capacity at 0.1C, 0.2C, 0.5C, 1C and 2C, and the capacity is 2124mAh/g after 10 cycles at 0.1C, and 10 cycles at 0.2C The capacity after 10 cycles at 0.5C is 1934mAh/g, 1734mAh/g after 10 cycles at 0.5C, 1509mAh/g after 10 cycles at 1C, and still not less than 1244mAh/g after 10 cycles at 2C. The rate performance is good.

Example 2

The aqueous solution of graphene oxide is mixed with nano silicon powder, deionized water, polydiene dimethyl ammonium chloride and ethylene glycol (or glycerol) to obtain a mixed solution. Wherein, the mass concentration of the aqueous solution of graphene oxide is 0.5mg/mL, the mass ratio of described nano silicon powder and graphene oxide is 5: 1, the mass ratio of nano silicon powder and polydiene dimethyl ammonium chloride is 10:1, the volume ratio of deionized water to ethylene glycol (or glycerol) is 1:6, and the volume ratio of ethylene glycol (or glycerol) to graphene oxide aqueous solution is 6:1;

Put the mixed solution in a reaction kettle, and conduct a hydrothermal reaction at 200°C for 2 hours to obtain a graphene/silicon composite gel;

The graphene/silicon composite gel was dried at normal pressure at 90°C for 0.5h, then freeze-dried at (-70)°C for 1h, and finally annealed at 1000°C for 1h under an inert atmosphere to obtain porous graphene/silicon composite gel. Silicon composite.

In the present invention, the obtained porous graphene/silicon composite material is subjected to scanning electron microscope scanning analysis, and the results are shown in FIGS. 5 and 6 . Fig. 5 is an SEM image of the porous graphene/silicon composite material prepared in Example 2 of the present invention. It can be seen from Fig. 5 that the porous graphene/silicon composite material provided by the present invention has a porous structure. Fig. 6 is an SEM image of the sample after grinding and pulverizing the porous graphene/silicon composite material obtained in Example 2 of the present invention. It can be seen from Fig. 6 that the pulverized porous graphene/silicon composite material has a porous structure.

In the present invention, the porous graphene/silicon composite material is mixed with the binder (SBR:CMC=3:7 mass ratio) and the conductive agent Super P according to the weight ratio of 80:10:10, and an appropriate amount of water is added as a dispersant. The slurry is evenly coated on the copper foil current collector, and is vacuum-dried and rolled to prepare a negative electrode sheet; with lithium metal as the counter electrode, the LiPF of 1mol/L mixed solvent (EC: DMC= ₁ : 1 volume ratio) as the electrolyte, polypropylene microporous membrane (Celgard 2400) as the separator, and assembled into a simulated battery in an argon-protected glove box. The assembled simulated battery was subjected to a constant current charge and discharge test on a Land tester (Wuhan ^Xinnuo Electronics Co., Ltd.). The performance curve is shown in Figure 3.

Experimental results show that the lithium-ion battery provided by the invention has a specific capacity of 1330mAh/g for the first discharge at a rate of 0.5C, and after 200 cycles of charge and discharge, the capacity retention rate is not less than 72%, and has good cycle performance.

At the same time, the present invention also investigates the discharge cycle performance of the obtained lithium ion battery at different rates, as shown in FIG. 4 . Experimental results show that the lithium ion battery provided by the present invention has higher specific capacity at 0.1C, 0.2C, 0.5C, 1C and 2C, and the capacity is 1613mAh/g after 10 cycles at 0.1C, and 10 times at 0.2C After 10 cycles at 0.5C, the capacity is 1501mAh/g. After 10 cycles at 0.5C, the capacity is 1328mAh/g. After 10 cycles at 1C, the capacity is 1214mAh/g. After 10 cycles at 2C, the capacity is still not less than 1030mAh/g. The rate performance is good.

Example 3

The aqueous solution of graphene oxide is mixed with nano silicon powder, deionized water, sodium polystyrene sulfonate and ethylene glycol (or glycerol) to obtain a mixed solution. Wherein, the mass concentration of the aqueous solution of graphene oxide is 7mg/mL, the mass ratio of described nano silicon powder and graphene oxide is 1:6, the mass ratio of nano silicon powder and sodium polystyrene sulfonate is 1:10, The volume ratio of deionized water to ethylene glycol (or glycerol) is 6:1, and the volume ratio of ethylene glycol (or glycerol) to the aqueous solution of graphene oxide is 1:6;

Put the mixed solution in a reaction kettle, and conduct a hydrothermal reaction at 100°C for 15 hours to obtain a graphene/silicon composite gel;

The graphene/silicon composite gel was dried at normal pressure at 30°C for 7h, then freeze-dried at (-10)°C for 60h, and finally annealed at 300°C for 8h under an inert atmosphere to obtain porous graphene/silicon composite material.

In the present invention, the obtained porous graphene/silicon composite material is subjected to scanning electron microscope scanning analysis, and the results are shown in FIGS. 7 and 8 . Fig. 7 is an SEM image of the porous graphene/silicon composite material prepared in Example 3 of the present invention. It can be seen from Fig. 7 that the porous graphene/silicon composite material provided by the present invention has a porous structure. Fig. 8 is an SEM image of the sample after grinding and pulverizing the porous graphene/silicon composite material obtained in Example 3 of the present invention. It can be seen from Fig. 8 that the pulverized porous graphene/silicon composite material has a porous structure.

In the present invention, the porous graphene/silicon composite material is mixed with the binder (SBR:CMC=3:7 mass ratio) and the conductive agent Super P according to the weight ratio of 80:10:10, and an appropriate amount of water is added as a dispersant. The slurry is evenly coated on the copper foil current collector, and is vacuum-dried and rolled to prepare a negative electrode sheet; with lithium metal as the counter electrode, the LiPF of 1mol/L mixed solvent (EC: DMC= ₁ : 1 volume ratio) as the electrolyte, polypropylene microporous membrane (Celgard 2400) as the separator, and assembled into a simulated battery in an argon-protected glove box. The assembled simulated battery was subjected to a constant current charge and discharge test on a Land tester (Wuhan ^Xinnuo Electronics Co., Ltd.). The performance curve is shown in Figure 3.

Experimental results show that the lithium ion battery provided by the invention has a specific capacity of 1590mAh/g for the first discharge at a rate of 0.5C, and after 200 cycles of charge and discharge, the capacity retention rate is not less than 76%, and has good cycle performance.

At the same time, the present invention also investigates the discharge cycle performance of the obtained lithium ion battery at different rates, as shown in FIG. 4 . Experimental results show that the lithium ion battery provided by the present invention has higher specific capacity at 0.1C, 0.2C, 0.5C, 1C and 2C, and the capacity is 1892mAh/g after 10 cycles at 0.1C, and 10 times at 0.2C After 10 cycles at 0.5C, the capacity is 1748mAh/g. After 10 cycles at 0.5C, the capacity is 1560mAh/g. After 10 cycles at 1C, the capacity is 1358mAh/g. After 10 cycles at 2C, the capacity is still not less than 1157mAh/g. The rate performance is good.

Example 4

The aqueous solution of graphene oxide is mixed with nano silicon powder, deionized water, polyvinylpyrrolidone and ethylene glycol (or glycerol) to obtain a mixed solution. Wherein, the mass concentration of the aqueous solution of graphene oxide is 1mg/mL, the mass ratio of described nano silicon powder and graphene oxide is 1:5, the mass ratio of nano silicon powder and polyvinylpyrrolidone is 1:5, deionized water The volume ratio of ethylene glycol (or glycerol) to ethylene glycol (or glycerol) is 5:1, and the volume ratio of ethylene glycol (or glycerol) to the aqueous solution of graphene oxide is 1:5;

Put the mixed solution in a reaction kettle, and conduct a hydrothermal reaction at 120°C for 8 hours to obtain a graphene/silicon composite gel;

The graphene/silicon composite gel was dried at normal pressure at 70°C for 4 hours, then freeze-dried at (-40)°C for 36 hours, and finally annealed at 500°C for 6 hours under an inert atmosphere to obtain porous graphene/silicon composite material.

In the present invention, the porous graphene/silicon composite material is mixed with the binder (SBR:CMC=3:7 mass ratio) and the conductive agent Super P according to the weight ratio of 80:10:10, and an appropriate amount of water is added as a dispersant. The slurry is evenly coated on the copper foil current collector, and is vacuum-dried and rolled to prepare a negative electrode sheet; with lithium metal as the counter electrode, the LiPF of 1mol/L mixed solvent (EC: DMC= ₁ : 1 volume ratio) as the electrolyte, polypropylene microporous membrane (Celgard 2400) as the separator, and assembled into a simulated battery in an argon-protected glove box. The assembled simulated battery was subjected to a constant current charge and discharge test on a Land tester (Wuhan Xinnuo Electronics Co., Ltd.), the charge and discharge voltage range was 0.001-1.5V, and the charge and discharge current density was 500mA g ^-1 .

Experimental results show that the first discharge specific capacity of the lithium-ion battery provided by the invention is 1750mAh/g at a rate of 0.5C, and after 200 cycles of charging and discharging, the capacity retention rate is not less than 82%.

At the same time, the present invention also investigates the discharge cycle performance of the obtained lithium ion battery at different rates. Experimental results show that the lithium ion battery provided by the present invention has higher specific capacity at 0.1C, 0.2C, 0.5C, 1C and 2C, and the capacity is 1922mAh/g after 10 cycles at 0.1C, and 10 times at 0.2C The final capacity is 1835mAh/g, the capacity after 10 cycles at 0.5C is 1660mAh/g, the capacity after 10 cycles at 1C is 1485mAh/g, and it is still not less than 1250mAh/g after 10 cycles at 2C.

Example 5

The aqueous solution of graphene oxide is mixed with nano silicon powder, deionized water, polyvinylpyrrolidone and ethanol to obtain a mixed solution. Wherein, the mass concentration of the aqueous solution of graphene oxide is 6mg/mL, the mass ratio of described nano silicon powder and graphene oxide is 1:1, the mass ratio of nano silicon powder and polyvinylpyrrolidone is 2:1, deionized water The volume ratio of ethanol to ethanol is 1:1, and the volume ratio of ethanol to graphene oxide aqueous solution is 1:1;

Put the mixed solution in a reaction kettle, and conduct a hydrothermal reaction at 180°C for 12 hours to obtain a graphene/silicon composite gel;

The graphene/silicon composite gel was dried at normal pressure at 60°C for 2h, then freeze-dried at (-60)°C for 48h, and finally annealed at 800°C for 4h under an inert atmosphere to obtain porous graphene/silicon composite material.

In the present invention, the porous graphene/silicon composite material is mixed with the binder (SBR:CMC=3:7 mass ratio) and the conductive agent Super P according to the weight ratio of 80:10:10, and an appropriate amount of water is added as a dispersant. The slurry is evenly coated on the copper foil current collector, and is vacuum-dried and rolled to prepare a negative electrode sheet; with lithium metal as the counter electrode, the LiPF of 1mol/L mixed solvent (EC: DMC= ₁ : 1 volume ratio) as the electrolyte, polypropylene microporous membrane (Celgard 2400) as the separator, and assembled into a simulated battery in an argon-protected glove box. The assembled simulated battery was subjected to a constant current charge and discharge test on a Land tester (Wuhan Xinnuo Electronics Co., Ltd.), the charge and discharge voltage range was 0.001-1.5V, and the charge and discharge current density was 500mA g ^-1 .

Experimental results show that the first discharge specific capacity of the lithium ion battery provided by the invention is 1630mAh/g at a rate of 0.5C, and after 200 cycles of charge and discharge, the capacity retention rate is not less than 80%, and has good cycle performance.

At the same time, the present invention also investigates the discharge cycle performance of the obtained lithium ion battery at different rates. Experimental results show that the lithium ion battery provided by the present invention has higher specific capacity at 0.1C, 0.2C, 0.5C, 1C and 2C, and the capacity is 2010mAh/g after 10 cycles at 0.1C, and 10 cycles at 0.2C The capacity is 1825mAh/g after 10 cycles at 0.5C, 1621mAh/g after 10 cycles at 1C, 1486mAh/g after 10 cycles at 1C, and still not less than 1124mAh/g after 10 cycles at 2C. The rate performance is good.

Example 6

The aqueous solution of graphene oxide is mixed with nano silicon powder, deionized water, polydiene dimethyl ammonium chloride and ethanol to obtain a mixed solution. Wherein, the mass concentration of the aqueous solution of graphene oxide is 0.5mg/mL, the mass ratio of described nano silicon powder and graphene oxide is 5: 1, the mass ratio of nano silicon powder and polydiene dimethyl ammonium chloride is 10:1, the volume ratio of deionized water to ethanol is 1:6, and the volume ratio of ethanol to graphene oxide aqueous solution is 6:1;

Put the mixed solution in a reaction kettle, and conduct a hydrothermal reaction at 200°C for 2 hours to obtain a graphene/silicon composite gel;

The graphene/silicon composite gel was dried at normal pressure at 90°C for 0.5h, then freeze-dried at (-70)°C for 1h, and finally annealed at 1000°C for 1h under an inert atmosphere to obtain porous graphene/silicon composite gel. Silicon composite.

In the present invention, the porous graphene/silicon composite material is mixed with the binder (SBR:CMC=3:7 mass ratio) and the conductive agent Super P according to the weight ratio of 80:10:10, and an appropriate amount of water is added as a dispersant. The slurry is evenly coated on the copper foil current collector, and is vacuum-dried and rolled to prepare a negative electrode sheet; with lithium metal as the counter electrode, the LiPF of 1mol/L mixed solvent (EC: DMC= ₁ : 1 volume ratio) as the electrolyte, polypropylene microporous membrane (Celgard 2400) as the separator, and assembled into a simulated battery in an argon-protected glove box. The assembled simulated battery was subjected to a constant current charge and discharge test on a Land tester (Wuhan Xinnuo Electronics Co., Ltd.), the charge and discharge voltage range was 0.001-1.5V, and the charge and discharge current density was 500mA g ^-1 .

Experimental results show that the first discharge specific capacity of the lithium ion battery provided by the invention is 1325mAh/g at a rate of 0.5C, and after 200 cycles of charge and discharge, the capacity retention rate is not less than 71%, which has good cycle performance.

At the same time, the present invention also investigates the discharge cycle performance of the obtained lithium ion battery at different rates. Experimental results show that the lithium ion battery provided by the present invention has higher specific capacity at 0.1C, 0.2C, 0.5C, 1C and 2C, and the capacity is 1612mAh/g after 10 cycles at 0.1C, and 10 times at 0.2C The final capacity is 1500mAh/g, 1322mAh/g after 10 cycles at 0.5C, 1212mAh/g after 10 cycles at 1C, not less than 1025mAh/g after 10 cycles at 2C.

Example 7

The aqueous solution of graphene oxide is mixed with nano silicon powder, deionized water, sodium polystyrene sulfonate and ethanol to obtain a mixed solution. Wherein, the mass concentration of the aqueous solution of graphene oxide is 7mg/mL, the mass ratio of described nano silicon powder and graphene oxide is 1:6, the mass ratio of nano silicon powder and sodium polystyrene sulfonate is 1:10, The volume ratio of deionized water to ethanol is 6:1, and the volume ratio of ethanol to graphene oxide aqueous solution is 1:6;

Put the mixed solution in a reaction kettle, and conduct a hydrothermal reaction at 100°C for 15 hours to obtain a graphene/silicon composite gel;

The graphene/silicon composite gel was dried at normal pressure at 30°C for 7h, then freeze-dried at (-10)°C for 60h, and finally annealed at 300°C for 8h under an inert atmosphere to obtain porous graphene/silicon composite material.

In the present invention, the porous graphene/silicon composite material is mixed with the binder (SBR:CMC=3:7 mass ratio) and the conductive agent Super P according to the weight ratio of 80:10:10, and an appropriate amount of water is added as a dispersant. The slurry is evenly coated on the copper foil current collector, and is vacuum-dried and rolled to prepare a negative electrode sheet; with lithium metal as the counter electrode, the LiPF of 1mol/L mixed solvent (EC: DMC= ₁ : 1 volume ratio) as the electrolyte, polypropylene microporous membrane (Celgard 2400) as the separator, and assembled into a simulated battery in an argon-protected glove box. The assembled simulated battery was subjected to a constant current charge and discharge test on a Land tester (Wuhan Xinnuo Electronics Co., Ltd.), the charge and discharge voltage range was 0.001-1.5V, and the charge and discharge current density was 500mA g ^-1 .

Experimental results show that the first discharge specific capacity of the lithium ion battery provided by the invention is 1585mAh/g at a rate of 0.5C, and after 200 cycles of charging and discharging, the capacity retention rate is not less than 75%.

At the same time, the present invention also investigates the discharge cycle performance of the obtained lithium ion battery at different rates. Experimental results show that the lithium ion battery provided by the present invention has higher specific capacity at 0.1C, 0.2C, 0.5C, 1C and 2C, and the capacity is 1885mAh/g after 10 cycles at 0.1C, and 10 times at 0.2C The capacity is 1710mAh/g after 10 cycles at 0.5C, 1510mAh/g after 10 cycles at 1C, 1330mAh/g after 10 cycles at 1C, and not less than 1123mAh/g after 10 cycles at 2C.

Example 8

The aqueous solution of graphene oxide is mixed with nano silicon powder, deionized water, polyvinylpyrrolidone and ethanol to obtain a mixed solution. Wherein, the mass concentration of the aqueous solution of graphene oxide is 1mg/mL, the mass ratio of described nano silicon powder and graphene oxide is 1:5, the mass ratio of nano silicon powder and polyvinylpyrrolidone is 1:5, deionized water The volume ratio of ethanol to ethanol is 5:1, and the volume ratio of ethanol to graphene oxide aqueous solution is 1:5;

Put the mixed solution in a reaction kettle, and conduct a hydrothermal reaction at 120°C for 8 hours to obtain a graphene/silicon composite gel;

The graphene/silicon composite gel was dried at normal pressure at 50°C for 3.5h, then freeze-dried at (-40)°C for 36h, and finally annealed at 500°C for 6h under an inert atmosphere to obtain porous graphene/silicon Silicon composite.

In the present invention, the porous graphene/silicon composite material is mixed with the binder (SBR:CMC=3:7 mass ratio) and the conductive agent Super P according to the weight ratio of 80:10:10, and an appropriate amount of water is added as a dispersant. The slurry is evenly coated on the copper foil current collector, and is vacuum-dried and rolled to prepare a negative electrode sheet; with lithium metal as the counter electrode, the LiPF of 1mol/L mixed solvent (EC: DMC= ₁ : 1 volume ratio) as the electrolyte, polypropylene microporous membrane (Celgard 2400) as the separator, and assembled into a simulated battery in an argon-protected glove box. The assembled simulated battery was subjected to a constant current charge and discharge test on a Land tester (Wuhan Xinnuo Electronics Co., Ltd.), the charge and discharge voltage range was 0.001-1.5V, and the charge and discharge current density was 500mA g ^-1 .

Experimental results show that the first discharge specific capacity of the lithium ion battery provided by the invention is 1610mAh/g at a rate of 0.5C, and after 200 cycles of charging and discharging, the capacity retention rate is not less than 79%.

At the same time, the present invention also investigates the discharge cycle performance of the obtained lithium ion battery at different rates. Experimental results show that the lithium ion battery provided by the present invention has higher specific capacity at 0.1C, 0.2C, 0.5C, 1C and 2C, and the capacity is 1900mAh/g after 10 cycles at 0.1C, and 10 times at 0.2C The capacity is 1695mAh/g after 10 cycles at 0.5C, 1489mAh/g after 10 cycles at 1C, 1296mAh/g after 10 cycles at 1C, and not less than 1220mAh/g after 10 cycles at 2C.

Example 9

The aqueous solution of graphene oxide is mixed with nano silicon powder, deionized water and polyvinylpyrrolidone to obtain a mixed solution. Wherein, the mass concentration of the aqueous solution of graphene oxide is 6mg/mL, the mass ratio of described nano silicon powder and graphene oxide is 1:1, the mass ratio of nano silicon powder and polyvinylpyrrolidone is 2:1, deionized water The volume ratio to the aqueous solution of graphene oxide is 1:1;

Put the mixed solution in a reaction kettle, and conduct a hydrothermal reaction at 180°C for 12 hours to obtain a graphene/silicon composite gel;

The graphene/silicon composite gel was dried at 65°C for 3 hours under 2 atmospheres, then freeze-dried at (-60)°C for 48 hours, and finally annealed at 800°C for 4 hours under an inert atmosphere to obtain porous graphene / silicon composite.

In the present invention, the porous graphene/silicon composite material is mixed with the binder (SBR:CMC=3:7 mass ratio) and the conductive agent Super P according to the weight ratio of 80:10:10, and an appropriate amount of water is added as a dispersant. The slurry is evenly coated on the copper foil current collector, and is vacuum-dried and rolled to prepare a negative electrode sheet; with lithium metal as the counter electrode, the LiPF of 1mol/L mixed solvent (EC: DMC= ₁ : 1 volume ratio) as the electrolyte, polypropylene microporous membrane (Celgard 2400) as the separator, and assembled into a simulated battery in an argon-protected glove box. The assembled simulated battery was subjected to a constant current charge and discharge test on a Land tester (Wuhan ^Xinnuo Electronics Co., Ltd.). The performance curve is shown in Figure 9.

Experimental results show that the first discharge specific capacity of the lithium-ion battery provided by the invention is 1715mAh/g at a rate of 0.5C, and the capacity retention rate is not less than 90% after 200 cycles of charging and discharging.

At the same time, the present invention also investigated the discharge cycle performance of the obtained lithium ion battery at different rates, as shown in FIG. 10 . Experimental results show that the lithium ion battery provided by the present invention has higher specific capacity at 0.1C, 0.2C, 0.5C, 1C and 2C, and the capacity is 2203mAh/g after 10 cycles at 0.1C, and 10 cycles at 0.2C After 10 cycles at 0.5C, the capacity is 1941mAh/g. After 10 cycles at 0.5C, the capacity is 1710mAh/g. After 10 cycles at 1C, the capacity is 1514mAh/g. After 10 cycles at 2C, the capacity is still not less than 1230mAh/g.

Example 10

The aqueous solution of graphene oxide is mixed with nano silicon powder, deionized water and polydiene dimethyl ammonium chloride to obtain a mixed solution. Wherein, the mass concentration of the aqueous solution of graphene oxide is 0.5mg/mL, the mass ratio of described nano silicon powder and graphene oxide is 5: 1, the mass ratio of nano silicon powder and polydiene dimethyl ammonium chloride is 10:1, the volume ratio of deionized water to graphene oxide aqueous solution is 6:1;

Put the mixed solution in a reaction kettle, and conduct a hydrothermal reaction at 200°C for 2 hours to obtain a graphene/silicon composite gel;

The graphene/silicon composite gel was dried at 30°C for 7 hours at 5 atmospheres, then freeze-dried at (-70)°C for 1 hour, and finally annealed at 1000°C for 1 hour under an inert atmosphere to obtain porous graphene / silicon composite.

In the present invention, the porous graphene/silicon composite material is mixed with the binder (SBR:CMC=3:7 mass ratio) and the conductive agent Super P according to the weight ratio of 80:10:10, and an appropriate amount of water is added as a dispersant. The slurry is evenly coated on the copper foil current collector, and is vacuum-dried and rolled to prepare a negative electrode sheet; with lithium metal as the counter electrode, the LiPF of 1mol/L mixed solvent (EC: DMC= ₁ : 1 volume ratio) as the electrolyte, polypropylene microporous membrane (Celgard 2400) as the separator, and assembled into a simulated battery in an argon-protected glove box. The assembled simulated battery was subjected to a constant current charge and discharge test on a Land tester (Wuhan ^Xinnuo Electronics Co., Ltd.). The performance curve is shown in Figure 9.

Experimental results show that the first discharge specific capacity of the lithium ion battery provided by the invention is 1335mAh/g at a rate of 0.5C, and after 200 cycles of charging and discharging, the capacity retention rate is not less than 72%.

At the same time, the present invention also investigated the discharge cycle performance of the obtained lithium ion battery at different rates, as shown in FIG. 10 . Experimental results show that the lithium ion battery provided by the present invention has higher specific capacity at 0.1C, 0.2C, 0.5C, 1C and 2C, and the capacity is 1568mAh/g after 10 cycles at 0.1C, and 10 times at 0.2C The capacity is 1507mAh/g after 10 cycles at 0.5C, 1330mAh/g after 10 cycles at 1C, 1222mAh/g after 10 cycles at 1C, and not less than 1028mAh/g after 10 cycles at 2C.

Example 11

The aqueous solution of graphene oxide is mixed with nano silicon powder, deionized water and sodium polystyrene sulfonate to obtain a mixed solution. Wherein, the mass concentration of the aqueous solution of graphene oxide is 7mg/mL, the mass ratio of described nano silicon powder and graphene oxide is 1:6, the mass ratio of nano silicon powder and sodium polystyrene sulfonate is 1:10, The volume ratio of deionized water to graphene oxide aqueous solution is 1:6;

Put the mixed solution in a reaction kettle, and conduct a hydrothermal reaction at 100°C for 15 hours to obtain a graphene/silicon composite gel;

The graphene/silicon composite gel was dried at 90°C for 0.5h at 3 atmospheres, then freeze-dried at (-10)°C for 60h, and finally annealed at 300°C for 8h under an inert atmosphere to obtain porous graphite olefin/silicon composites.

In the present invention, the porous graphene/silicon composite material is mixed with the binder (SBR:CMC=3:7 mass ratio) and the conductive agent Super P according to the weight ratio of 80:10:10, and an appropriate amount of water is added as a dispersant. The slurry is evenly coated on the copper foil current collector, and is vacuum-dried and rolled to prepare a negative electrode sheet; with lithium metal as the counter electrode, the LiPF of 1mol/L mixed solvent (EC: DMC= ₁ : 1 volume ratio) as the electrolyte, polypropylene microporous membrane (Celgard 2400) as the separator, and assembled into a simulated battery in an argon-protected glove box. The assembled simulated battery was subjected to a constant current charge and discharge test on a Land tester (Wuhan ^Xinnuo Electronics Co., Ltd.). The performance curve is shown in Figure 9.

Experimental results show that the first discharge specific capacity of the lithium-ion battery provided by the invention is 1554mAh/g at a rate of 0.5C, and after 200 cycles of charging and discharging, the capacity retention rate is not less than 78%.

At the same time, the present invention also investigated the discharge cycle performance of the obtained lithium ion battery at different rates, as shown in FIG. 10 . The experimental results show that the lithium ion battery provided by the present invention has a higher specific capacity at 0.1C, 0.2C, 0.5C, 1C and 2C, and the capacity is 1855mAh/g after 10 cycles at 0.1C, and 10 times at 0.2C The capacity is 1683mAh/g after 10 cycles at 0.5C, 1530mAh/g after 10 cycles at 1C, 1342mAh/g after 10 cycles at 1C, and not less than 1157mAh/g after 10 cycles at 2C.

Example 12

The aqueous solution of graphene oxide is mixed with nano silicon powder, deionized water and polyvinylpyrrolidone to obtain a mixed solution. Wherein, the mass concentration of the aqueous solution of graphene oxide is 1mg/mL, the mass ratio of described nano silicon powder and graphene oxide is 1:5, the mass ratio of nano silicon powder and polyvinylpyrrolidone is 1:5, deionized water The volume ratio to the aqueous solution of graphene oxide is 1:5;

Put the mixed solution in a reaction kettle, and conduct a hydrothermal reaction at 120°C for 8 hours to obtain a graphene/silicon composite gel;

The graphene/silicon composite gel was dried at 1.5 atmospheres at 70°C for 2 hours, then freeze-dried at (-40)°C for 36 hours, and finally annealed at 500°C for 6 hours under an inert atmosphere to obtain porous graphene / silicon composite.

In the present invention, the porous graphene/silicon composite material is mixed with the binder (SBR:CMC=3:7 mass ratio) and the conductive agent Super P according to the weight ratio of 80:10:10, and an appropriate amount of water is added as a dispersant. The slurry is evenly coated on the copper foil current collector, and is vacuum-dried and rolled to prepare a negative electrode sheet; with lithium metal as the counter electrode, the LiPF of 1mol/L mixed solvent (EC: DMC= ₁ : 1 volume ratio) as the electrolyte, polypropylene microporous membrane (Celgard 2400) as the separator, and assembled into a simulated battery in an argon-protected glove box. The assembled simulated battery was subjected to a constant current charge and discharge test on a Land tester (Wuhan Xinnuo Electronics Co., Ltd.), the charge and discharge voltage range was 0.001-1.5V, and the charge and discharge current density was 500mA g ^-1 .

Experimental results show that the first discharge specific capacity of the lithium ion battery provided by the invention is 1700mAh/g at a rate of 0.5C, and after 200 cycles of charging and discharging, the capacity retention rate is not less than 88%.

At the same time, the present invention also investigates the discharge cycle performance of the obtained lithium ion battery at different rates. Experimental results show that the lithium ion battery provided by the present invention has higher specific capacity at 0.1C, 0.2C, 0.5C, 1C and 2C, and the capacity is 2085mAh/g after 10 cycles at 0.1C, and 10 cycles at 0.2C After 10 cycles at 0.5C, the capacity is 1802mAh/g. After 10 cycles at 0.5C, the capacity is 1662mAh/g. After 10 cycles at 1C, the capacity is 1406mAh/g. After 10 cycles at 2C, the capacity is still not less than 1227mAh/g.

Example 13

The aqueous solution of graphene oxide is mixed with nano silicon powder, deionized water and polyvinylpyrrolidone to obtain a mixed solution. Wherein, the mass concentration of the aqueous solution of graphene oxide is 6mg/mL, the mass ratio of described nano silicon powder and graphene oxide is 1:1, the mass ratio of nano silicon powder and polyvinylpyrrolidone is 2:1, deionized water The volume ratio to the aqueous solution of graphene oxide is 1:1;

Put the mixed solution in a reaction kettle, and conduct a hydrothermal reaction at 180°C for 12 hours to obtain a graphene/silicon composite gel;

The graphene/silicon composite gel was dried at 50°C for 3 hours at 0.7 atmospheres, then freeze-dried at (-60)°C for 48 hours, and finally annealed at 800°C for 4 hours under an inert atmosphere to obtain porous graphene / silicon composite.

In the present invention, the porous graphene/silicon composite material is mixed with the binder (SBR:CMC=3:7 mass ratio) and the conductive agent Super P according to the weight ratio of 80:10:10, and an appropriate amount of water is added as a dispersant. The slurry is evenly coated on the copper foil current collector, and is vacuum-dried and rolled to prepare a negative electrode sheet; with lithium metal as the counter electrode, the LiPF of 1mol/L mixed solvent (EC: DMC= ₁ : 1 volume ratio) as the electrolyte, polypropylene microporous membrane (Celgard 2400) as the separator, and assembled into a simulated battery in an argon-protected glove box. The assembled simulated battery was subjected to a constant current charge and discharge test on a Land tester (Wuhan Xinnuo Electronics Co., Ltd.), the charge and discharge voltage range was 0.001-1.5V, and the charge and discharge current density was 500mA g ^-1 .

Experimental results show that the first discharge specific capacity of the lithium ion battery provided by the invention is 1735mAh/g at a rate of 0.5C, and after 200 cycles of charging and discharging, the capacity retention rate is not less than 90%.

At the same time, the present invention also investigates the discharge cycle performance of the obtained lithium ion battery at different rates. Experimental results show that the lithium ion battery provided by the present invention has higher specific capacity at 0.1C, 0.2C, 0.5C, 1C and 2C, and the capacity is 2203mAh/g after 10 cycles at 0.1C, and 10 cycles at 0.2C The capacity after 10 cycles at 0.5C is 1941mAh/g, 1732mAh/g after 10 cycles at 0.5C, 1514mAh/g after 10 cycles at 1C, and not less than 1230mAh/g after 10 cycles at 2C.

Example 14

The aqueous solution of graphene oxide is mixed with nano silicon powder, deionized water and polydiene dimethyl ammonium chloride to obtain a mixed solution. Wherein, the mass concentration of the aqueous solution of graphene oxide is 0.5mg/mL, the mass ratio of described nano silicon powder and graphene oxide is 5: 1, the mass ratio of nano silicon powder and polydiene dimethyl ammonium chloride is 10:1, the volume ratio of deionized water to graphene oxide aqueous solution is 6:1;

Put the mixed solution in a reaction kettle, and conduct a hydrothermal reaction at 200°C for 2 hours to obtain a graphene/silicon composite gel;

The graphene/silicon composite gel was dried at 60°C under 0.6 atmospheres for 1 hour, then freeze-dried at (-70)°C for 1 hour, and finally annealed at 1000°C for 1 hour under an inert atmosphere to obtain porous graphene / silicon composite.

In the present invention, the porous graphene/silicon composite material is mixed with the binder (SBR:CMC=3:7 mass ratio) and the conductive agent Super P according to the weight ratio of 80:10:10, and an appropriate amount of water is added as a dispersant. The slurry is evenly coated on the copper foil current collector, and is vacuum-dried and rolled to prepare a negative electrode sheet; with lithium metal as the counter electrode, the LiPF of 1mol/L mixed solvent (EC: DMC= ₁ : 1 volume ratio) as the electrolyte, polypropylene microporous membrane (Celgard 2400) as the separator, and assembled into a simulated battery in an argon-protected glove box. The assembled simulated battery was subjected to a constant current charge and discharge test on a Land tester (Wuhan Xinnuo Electronics Co., Ltd.), the charge and discharge voltage range was 0.001-1.5V, and the charge and discharge current density was 500mA g ^-1 .

Experimental results show that the first discharge specific capacity of the lithium ion battery provided by the invention is 1335mAh/g at a rate of 0.5C, and after 200 cycles of charging and discharging, the capacity retention rate is not less than 72%.

At the same time, the present invention also investigates the discharge cycle performance of the obtained lithium ion battery at different rates. Experimental results show that the lithium ion battery provided by the present invention has higher specific capacity at 0.1C, 0.2C, 0.5C, 1C and 2C, and the capacity is 1568mAh/g after 10 cycles at 0.1C, and 10 times at 0.2C The capacity is 1507mAh/g after 10 cycles at 0.5C, 1328mAh/g after 10 cycles at 1C, 1222mAh/g after 10 cycles at 1C, and not less than 1028mAh/g after 10 cycles at 2C.

Example 15

The aqueous solution of graphene oxide is mixed with nano silicon powder, deionized water and sodium polystyrene sulfonate to obtain a mixed solution. Wherein, the mass concentration of the aqueous solution of graphene oxide is 7mg/mL, the mass ratio of described nano silicon powder and graphene oxide is 1:6, the mass ratio of nano silicon powder and sodium polystyrene sulfonate is 1:10, The volume ratio of deionized water to graphene oxide aqueous solution is 1:6;

Put the mixed solution in a reaction kettle, and conduct a hydrothermal reaction at 100°C for 15 hours to obtain a graphene/silicon composite gel;

The graphene/silicon composite gel was dried at 30°C for 2 hours at 0.5 atmospheric pressure, then freeze-dried at (-10)°C for 60 hours, and finally annealed at 300°C for 8 hours under an inert atmosphere to obtain porous graphene / silicon composite.

In the present invention, the porous graphene/silicon composite material is mixed with the binder (SBR:CMC=3:7 mass ratio) and the conductive agent Super P according to the weight ratio of 80:10:10, and an appropriate amount of water is added as a dispersant. The slurry is evenly coated on the copper foil current collector, and is vacuum-dried and rolled to prepare a negative electrode sheet; with lithium metal as the counter electrode, the LiPF of 1mol/L mixed solvent (EC: DMC= ₁ : 1 volume ratio) as the electrolyte, polypropylene microporous membrane (Celgard 2400) as the separator, and assembled into a simulated battery in an argon-protected glove box. The assembled simulated battery was subjected to a constant current charge and discharge test on a Land tester (Wuhan Xinnuo Electronics Co., Ltd.), the charge and discharge voltage range was 0.001-1.5V, and the charge and discharge current density was 500mA g ^-1 .

Experimental results show that the first discharge specific capacity of the lithium-ion battery provided by the invention is 1554mAh/g at a rate of 0.5C, and after 200 cycles of charging and discharging, the capacity retention rate is not less than 78%.

At the same time, the present invention also investigates the discharge cycle performance of the obtained lithium ion battery at different rates. The experimental results show that the lithium ion battery provided by the present invention has a higher specific capacity at 0.1C, 0.2C, 0.5C, 1C and 2C, and the capacity is 1855mAh/g after 10 cycles at 0.1C, and 10 times at 0.2C The capacity is 1683mAh/g after 10 cycles at 0.5C, 1530mAh/g after 10 cycles at 1C, 1342mAh/g after 10 cycles at 1C, and not less than 1157mAh/g after 10 cycles at 2C.

Example 16

The aqueous solution of graphene oxide is mixed with nano silicon powder, deionized water and polyvinylpyrrolidone to obtain a mixed solution. Wherein, the mass concentration of the aqueous solution of graphene oxide is 1mg/mL, the mass ratio of described nano silicon powder and graphene oxide is 1:5, the mass ratio of nano silicon powder and polyvinylpyrrolidone is 1:5, deionized water The volume ratio to the aqueous solution of graphene oxide is 1:5;

Put the mixed solution in a reaction kettle, and conduct a hydrothermal reaction at 120°C for 8 hours to obtain a graphene/silicon composite gel;

The graphene/silicon composite gel was dried at 90°C for 0.5h at 0.9 atmospheric pressure, then freeze-dried at (-40)°C for 36h, and finally annealed at 500°C for 6h under an inert atmosphere to obtain porous graphite olefin/silicon composites.

In the present invention, the porous graphene/silicon composite material is mixed with the binder (SBR:CMC=3:7 mass ratio) and the conductive agent Super P according to the weight ratio of 80:10:10, and an appropriate amount of water is added as a dispersant. The slurry is evenly coated on the copper foil current collector, and is vacuum-dried and rolled to prepare a negative electrode sheet; with lithium metal as the counter electrode, the LiPF of 1mol/L mixed solvent (EC: DMC= ₁ : 1 volume ratio) as the electrolyte, polypropylene microporous membrane (Celgard 2400) as the separator, and assembled into a simulated battery in an argon-protected glove box. The assembled simulated battery was subjected to a constant current charge and discharge test on a Land tester (Wuhan Xinnuo Electronics Co., Ltd.), the charge and discharge voltage range was 0.001-1.5V, and the charge and discharge current density was 500mA g ^-1 .

Experimental results show that the first discharge specific capacity of the lithium ion battery provided by the invention is 1700mAh/g at a rate of 0.5C, and after 200 cycles of charging and discharging, the capacity retention rate is not less than 88%.

At the same time, the present invention also investigates the discharge cycle performance of the obtained lithium ion battery at different rates. Experimental results show that the lithium ion battery provided by the present invention has higher specific capacity at 0.1C, 0.2C, 0.5C, 1C and 2C, and the capacity is 2085mAh/g after 10 cycles at 0.1C, and 10 cycles at 0.2C After 10 cycles at 0.5C, the capacity is 1802mAh/g. After 10 cycles at 0.5C, the capacity is 1662mAh/g. After 10 cycles at 1C, the capacity is 1406mAh/g. After 10 cycles at 2C, the capacity is still not less than 1227mAh/g.

The above description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention will not be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (10)

1. the preparation method of porous graphene/silicon composite, it is characterised in that comprise the following steps:

A1) aqueous solution of graphene oxide, nano silica fume, deionized water, surfactant and organic solvent are mixed, mixed Close solution；

B) described mixed solution is carried out hydro-thermal reaction, obtain graphene/silicon pluralgel；

C1) described graphene/silicon pluralgel is dried at normal pressure, 30 DEG C～90 DEG C 0.5～7h, then carries out freezing dry Dry, be thermally treated resulting in porous graphene/silicon composite；

Or

A2) aqueous solution of graphene oxide, nano silica fume, deionized water and surfactant are mixed, obtain mixed solution；

B) described mixed solution is carried out hydro-thermal reaction, obtain graphene/silicon pluralgel；

C2) by described graphene/silicon pluralgel under 0.5～5 atmospheric pressure, dry 0.5～7h, then enter for 30 DEG C～90 DEG C Row lyophilization, heat treatment, obtain porous graphene/silicon composite.

Preparation method the most according to claim 1, it is characterised in that the mass concentration of the aqueous solution of described graphene oxide For 0.5mg/mL～7mg/mL.

Preparation method the most according to claim 1, it is characterised in that step A1) in, described nano silica fume and graphite oxide The mass ratio of alkene is 1:6～5:1, and described nano silica fume is 1:10～10:1 with the mass ratio of surfactant, described deionization Water is 1:6～6:1 with the volume ratio of organic solvent, and described organic solvent is 1:6 with the volume ratio of the aqueous solution of graphene oxide ～6:1.

Preparation method the most according to claim 1, it is characterised in that described organic solvent is selected from ethanol, ethylene glycol or third One in triol.

Preparation method the most according to claim 1, it is characterised in that step A2) in, described nano silica fume and graphite oxide Alkene mass ratio is 1:6～5:1, and described nano silica fume is 1:10～10:1 with the mass ratio of surfactant, described deionized water It is 1:6～6:1 with the volume ratio of the aqueous solution of graphene oxide.

Preparation method the most according to claim 1, it is characterised in that the temperature of described hydro-thermal reaction is 100 DEG C～200 DEG C, the time of described hydro-thermal reaction is 2h～15h.

Preparation method the most according to claim 1, it is characterised in that step C2) in, by compound for described graphene/silicon solidifying Glue, under 0.7～0.9 atmospheric pressure or 1.5～3 atmospheric pressure, dries 0.5～7h for 30 DEG C～90 DEG C, then carries out freezing dry Dry, heat treatment, obtains porous graphene/silicon composite.

Preparation method the most according to claim 1, it is characterised in that the temperature of described heat treatment is 300 DEG C～1000 DEG C, The time of described heat treatment is 1h～8h.

9. porous graphene/silicon composite that prepared by claim 1～8 any one preparation method.

10. a lithium ion battery, including positive pole, negative pole, barrier film and electrolyte, it is characterised in that described negative pole includes right Require the porous graphene/silicon composite described in 9.