CN103794754B - Composite negative electrode and preparation method thereof as well as electrochemical power source and application thereof - Google Patents

Abstract

The invention provides a composite negative electrode, a preparation method thereof and a lithium battery. The composite negative electrode comprises one or more layers of porous current collectors laminated and bonded, the pores of the porous current collectors are filled with active fillers, and the active fillers contain binders, conductive agents and have the ability to intercalate lithium ions The active substance accounts for 80-98% of the total weight of the active filler. The preparation method includes the steps of preparing slurry containing active substances and injecting the slurry. The lithium battery contains the composite negative electrode. The invention has stable volume, high capacity, simple preparation process, easy control of conditions, high production efficiency and reduced production cost. The lithium battery has high-current charging and discharging characteristics, taking into account high specific energy and power characteristics.

Description

Composite negative electrode and preparation method thereof, electrochemical power source and application thereof

technical field

The invention belongs to the technical field of batteries, and in particular relates to a composite negative electrode, a preparation method thereof, an electrochemical power source and an application thereof.

Background technique

Most of the existing lithium-ion batteries use graphite-based negative electrode materials, and the active material is coated on a flat copper foil current collector. Although the volume expansion of graphite material due to charging is only about 10%, even after hundreds of cycles of charging and discharging, the active material and the current collector can still maintain good electrical contact. However, in order to pursue high specific energy density, the coating of the pole piece The thickness is as high as tens of microns or even more than one hundred microns. In this way, the distance between the active material on the surface of the pole piece and the current collector is long, and the electron transmission path is long, so that the battery can only be charged and discharged with a small current, the power density of the battery is relatively low, and the charging time takes several hours.

In addition, after two decades of development, the actual capacity of existing graphite materials (about 350~360mAh/g) is close to its theoretical capacity (372mAh/g), and the room for capacity improvement is very limited. With the emergence of emerging electronic products such as smart phones, traditional lithium-ion batteries can no longer meet the backup power requirements of these electronic products. Human beings urgently need to develop backup battery products with higher specific energy to meet the human dream of using smart phones to surf the Internet .

Si, Sn, Al, Sb, Ge, Zn, Pb, Mg, Na and other materials have become high specific energy negative electrodes due to their higher specific capacity (for example, the theoretical capacity of Si negative electrode is as high as 4200mAh/g, which is 10 times that of graphite). The first choice of active materials, however, they will have a huge volume expansion effect due to the intercalation of lithium ions (such as the volume expansion rate of the silicon negative electrode exceeds 300%). This volume expansion effect must be overcome or suppressed to make these new high specific energy electrodes Materials get real application.

In order to slow down the volume expansion effect of these materials, researchers and material manufacturers have prepared materials such as Si, Sn, Al, Sb, Ge, Zn, Pb, Mg, Na, etc. into nanoparticles, nanowires, nanofibers, etc. material, and then coated on a flat copper foil current collector. Nanoscale materials have a relatively high specific capacity. However, due to the agglomeration of nanomaterials and the volume expansion of materials, the active material will be pulverized and fall off from the existing flat copper foil current collector, and the cycle life of the battery cannot meet the application requirements.

Another scholar used acetylene black flexible current collectors to prepare composite electrodes for silicon negative electrodes. The specific preparation method is as follows: firstly, carbon-coated silicon, conductive carbon black and binder are prepared into a slurry, coated on the surface of the diaphragm and dried to obtain a carbon-coated silicon layer, and then the slurry containing acetylene black and binder The material is coated or sprayed on the surface of the carbon-coated silicon layer, and dried to obtain a lithium-ion battery negative electrode. For silicon-based materials with large volume changes during charge and discharge, the anode with acetylene black as a flexible current collector has significantly improved cycle stability compared with the traditional anode with copper foil as a current collector. However, the strength of this flexible current collector is relatively poor. If it is prepared into a battery, it cannot be mechanically wound during the preparation process. Moreover, due to the poor strength, deformation of the pole pieces is prone to occur inside the battery, which will cause deformation of the battery appearance and even damage the appearance of the mobile phone.

There are also companies in the industry that use the hydrogen bubble template method to prepare porous current collectors, and then deposit tin on site to prepare composite electrodes. The preparation method includes the following steps: firstly, a porous current collector is prepared by a hydrogen bubble template method; then, a tin-based alloy and carbon nanotubes are deposited on the porous current collector by a composite electrodeposition method to obtain a porous current collector/tin-based alloy/ Carbon nanotube integrated electrode. However, the preparation process of this method is relatively complicated, and it requires on-site electrodeposition of tin alloy and carbon nanotubes, the electrode deposition thickness is small, the specific energy of the battery is not greatly improved, and the electrode preparation efficiency is low.

Contents of the invention

The purpose of the embodiments of the present invention is to overcome the above-mentioned shortcomings of the prior art, and provide a composite negative electrode with stable volume and high capacity.

Another object of the embodiments of the present invention is to provide a method for preparing a composite negative electrode with a simple process.

Another object of the embodiments of the present invention is to provide an electrochemical power source capable of charging and discharging with a large current, taking into account high specific energy and power, and its application.

In order to realize the above-mentioned purpose of the invention, the technical scheme of the present invention is as follows:

A composite negative electrode, comprising one or more layers of porous current collectors laminated and bonded, the pores of the porous current collectors are filled with active fillers, the active fillers contain binders, conductive agents and intercalated lithium Active material with ionic capacity, the active material accounts for 80-98% of the total weight of the active filler.

Preferably, the above-mentioned active substance is at least one of nano elemental particles, nanowires, nanotubes, nanofibers, nanofilms, nano-oxide particles, and nano-alloy particles of M element, or the active substance is a nanometer particle of M element. A composite of at least one of elemental particles, nanowires, nanotubes, nanofibers, nanofilms, nano-oxide particles, and nano-alloy particles with carbon; wherein, the M element is Si, Sn, Al, Sb, Ge , Zn, Pb, Mg, Na at least one.

Specifically, when the above-mentioned active substance is a composite of at least one of elemental nanometer particles, nanowires, nanotubes, nanofibers, nanofilms, nanooxide particles, and nanoalloy particles of M element with carbon, the composite In the composite of at least one of nano elemental particles, nanowires, nanotubes, nanofibers, nanofilms, nano-oxide particles, nano-alloy particles and carbon in the M element, the active material of the M element is in the The weight content in the compound is 10-98%.

Specifically, the particle size of the above nano elemental particles, nano oxide particles or nano alloy particles is 1-800 nm.

Preferably, the number of layers of the above-mentioned porous current collector is 1-20 layers.

Specifically, the above-mentioned porous current collector is nickel foam, copper foam, aluminum foam, carbon foam, stainless steel mesh, nickel mesh, copper mesh or aluminum mesh.

And, the preparation method of above-mentioned composite negative electrode, comprises the following steps:

The conductive agent, the binder and the active material with the ability to intercalate lithium ions are dispersed in an aqueous or oily solvent to prepare a slurry containing the active material; wherein the active material, the conductive agent, and the binder are The weight ratio is 100:(0-15):(1-15), and the content of the active substance in the slurry is 20%-70%;

Inject the slurry into the pores of a porous current collector and dry to obtain the composite negative electrode; or inject the slurry into the pores of at least two porous current collectors and dry, and then the dried porous The current collectors are stacked and combined by hot pressing, rolling or/and sintering to obtain the composite negative electrode.

Preferably, the above-mentioned slurry is injected into the pores of the porous current collector by one or a combination of two or more of pouring, deposition, coating, spraying, soaking, and printing.

Preferably, the aqueous solvent is at least one of pure water, distilled water, and tap water; the oily solvent is at least one of N-methylpyrrolidone, ethanol, propanol, and cyclohexane.

An embodiment of the present invention also provides an electrochemical power source, including the above composite negative electrode.

Preferably, the above-mentioned electrochemical power source is a chemical lithium battery for electrochemical reaction or a composite lithium capacitor for electrochemical reaction.

Specifically, the chemical lithium battery mentioned above is a lithium ion battery, a lithium polymer battery, a lithium sulfur battery or a lithium air battery; the composite lithium capacitor is a lithium ion capacitor.

And, the application of the above electrochemical power source in mobile terminal products, electric vehicles, power grids, communication equipment and/or electric tools.

Specifically, the above-mentioned communication device includes a working module and a power supply module, the power supply module includes the electrochemical power supply, and the electrochemical power supply is a chemical lithium battery for electrochemical reaction; the power supply module provides electrical energy for the working module, The working module runs with the electric energy provided by the power supply module.

The above-mentioned composite negative electrode embeds the active material capable of intercalating lithium ions into the porous structure (pores) of the porous current collector. In this way, the porous structure can effectively inhibit the volume expansion of the active material due to intercalation of lithium ions, thereby avoiding pulverization. fall off, thereby enhancing the electrical contact between the active material and the current collector and the capacity of the composite negative electrode. At the same time, the active material is dispersed in the porous structure of the current collector, which can effectively avoid the pulverization phenomenon caused by the agglomeration of the particles of the active material, and enhance the strength of the combination of the active material and the current collector, thus ensuring the high efficiency of the active material. The specific capacity prolongs the cycle life and capacity of the composite negative electrode. In addition, the above-mentioned composite negative electrode adopts a porous current collector with a porous structure, which enhances its mechanical strength, facilitates its mechanical winding, and enhances its shape stability.

The preparation method of the above-mentioned composite negative electrode only needs to prepare the active material capable of intercalating lithium ions into a slurry, and then directly inject it into the porous structure of the current collector for drying, or further heat-press and grind the dried current collector. The composite negative electrode can be obtained by pressing or/and sintering. The preparation method has the advantages of simple process, easy control of conditions, high production efficiency, reduced production cost, and effectively avoids the shortcomings of complex process, low production efficiency, high cost and low specific energy of the battery in the existing electrodeposition method for producing composite electrodes. .

The above-mentioned electrochemical power source contains the above-mentioned composite negative electrode, and it is precisely because of the high capacity of the composite negative electrode that the electrochemical power source, such as a lithium battery, is endowed with a high specific energy. In addition, the volume of the above-mentioned composite negative electrode is stable during the charging and discharging process, thus endowing the electrochemical power source with excellent cycle stability performance, prolonging the cycle life of the electrochemical power source, and enhancing the safety of the electrochemical power source. At the same time, because the above-mentioned active material in the above-mentioned composite negative electrode is embedded in the porous structure of the current collector, the distance between the active material and the current collector is short, the electron transmission path is shortened, and the electrochemical power supply has high-current charge and discharge characteristics and high power. It is precisely because the electrochemical power source has this excellent performance that the application range of the electrochemical power source is expanded.

Description of drawings

The present invention will be further described below in conjunction with accompanying drawing and embodiment, in the accompanying drawing:

Fig. 1 is the structural representation of composite negative electrode of the embodiment of the present invention;

Fig. 2 is the schematic diagram of the cross-sectional structure of the composite negative electrode described in Fig. 1;

3 is a schematic diagram of a preferred structure of a composite negative electrode according to an embodiment of the present invention;

Fig. 4 is another preferred structural schematic diagram of the composite negative electrode of the embodiment of the present invention;

Fig. 5 is another preferred structural schematic diagram of the composite negative electrode of the embodiment of the present invention;

6 is a process flow diagram of a method for preparing a composite negative electrode according to an embodiment of the present invention;

FIG. 7 is a comparison chart of cycle performance data of batteries in Examples 1-3 and Comparative Examples.

detailed description

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention.

The example of the present invention provides a composite negative electrode with stable volume and high capacity, the structure of which is shown in Figures 1 and 2 . The composite negative electrode includes n (n is an integer, and 1≤n≤20) layers of porous current collectors 1 , and the pores 2 of each layer of porous current collectors 1 are filled with active fillers 3 . Wherein, the active filler 3 contains a binder, a conductive agent and an active material capable of intercalating lithium ions, and the active material accounts for 80-98% of the total weight of the active filler 3 . In this way, the porous current collector 1 can be one layer, or more than two layers. Therefore, the composite negative electrode can at least have the following structure:

As an embodiment of the present invention, the composite negative electrode contains a layer (ie, n=1) of a porous current collector 1 , the structure of which is shown in FIG. 3 . The above-mentioned active filler 3 is filled in the hole 2 of the porous current collector 1 , as shown in FIG. 2 .

As another embodiment of the present invention, the composite negative electrode contains two layers (that is, n=2) of porous current collectors 1, namely, porous current collectors 11 and porous current collectors 12, and the porous current collectors 11 and porous current collectors 12 are stacked and combined as As a whole, its structure is shown in Figure 4. The structure of the porous current collectors 11 and 12 is as shown in FIG. 2 , that is, the pores 2 of the porous current collectors 11 and 12 are filled with the above-mentioned active fillers 3 . Wherein, the lamination bonding method between the porous current collector 11 and the porous current collector 12 refers to the bonding method described in the preparation method of the composite negative electrode below, such as hot pressing, rolling, sintering and other bonding methods.

As yet another embodiment of the present invention, the composite negative electrode contains three layers (n=3) of porous current collectors 1, namely porous current collectors 11, porous current collectors 12, and porous current collectors 13. The porous current collectors 11, porous current collectors 12 and the porous current collector 13 are stacked and integrated with each other, and its structure is shown in FIG. 5 . The structures of the porous current collectors 11 , 12 and 13 are as shown in FIG. 2 , that is, the pores 2 of the porous current collectors 11 , 12 and 13 are all filled with active fillers 3 . Wherein, the active filler 3 is as described above, and the lamination bonding method among the porous current collectors 11 , 12 and 13 refers to the bonding method described in the preparation method of the composite negative electrode below.

When 4≤n≤20, the structure of the above-mentioned composite negative electrode can refer to the structure of the above-mentioned composite negative electrode when n=2 or 3, and the porous current collectors 1 of each layer are stacked and integrated. Wherein, the structure of the porous current collector 1 of each layer is as shown in Figure 2, the holes 2 of the porous current collector 1 are filled with active fillers 3, and the active fillers 3 contain 80-98% of the total weight of the active fillers 3. % of the active material with the ability to intercalate lithium ions. In addition, for the lamination bonding method between the porous current collector 11 and the porous current collector 12, please refer to the bonding method described in the preparation method of the composite negative electrode below, such as hot pressing, rolling, sintering and other bonding methods.

Preferably, the aforementioned n is 3-5. The number of layers of the preferred current collector 1 can enable the active filler 3 to be better injected into the hole 2 of the current collector 1 during the preparation of the composite negative electrode, so that the hole 2 is filled with the active filler 3 as much as possible, and at the same time It is also beneficial to the lamination and bonding of current collectors of various layers during the preparation process of the above-mentioned composite negative electrode.

Specifically, the porous current collector 1 in the above embodiments is preferably nickel foam, copper foam, aluminum foam, carbon foam, stainless steel mesh, nickel mesh, copper mesh or aluminum mesh. The preferred current collector 1 has a porous structure, which is convenient for embedding the above-mentioned active filler 3 into the pores of the porous structure. For example, nickel foam, copper foam, aluminum foam, and carbon foam have a rich three-dimensional porous structure. After the active filler 3 is embedded in it, the active filler 3 is more tightly combined with foamed nickel, copper foam, aluminum foam, and carbon foam. , firm, thereby effectively inhibiting the volume expansion of the active material due to the intercalation of lithium ions and causing pulverization and falling off, thereby enhancing the electrical contact between the active material and the porous current collector 1 .

As mentioned above, the active filler 3 in each of the above embodiments contains an active material capable of intercalating lithium ions in an amount of preferably 80-98% by weight. In a further preferred embodiment, the content of the active substance accounts for 88-95% of the total weight percentage of the active filler 3 . The inventors have found in research that appropriately changing the content of the active material in the active filler 3 can significantly change the capacity of the composite negative electrodes of the above-mentioned embodiments.

Specifically, as an embodiment of the present invention, the above-mentioned active material is preferably at least one of elemental nano-particles, nanowires, nanotubes, nanofibers, nanofilms, nano-oxide particles, and nano-alloy particles of M element; or The active substance is preferably a compound of at least one of elemental nano particles, nanowires, nanotubes, nanofibers, nanofilms, nano oxide particles, and nanoalloy particles of M element and carbon; wherein, the M element is At least one of Si, Sn, Al, Sb, Ge, Zn, Pb, Mg, Na; when the active material is nano elemental particles, nanowires, nanotubes, nanofibers, nanofilms, nano oxide particles of M element , at least one of nano-alloy particles and carbon composites, at least one of nano-element particles, nano-wires, nano-tubes, nano-fibers, nano-films, nano-oxide particles, and nano-alloy particles of the M element The weight content in the compound is preferably 10-98%. The preferred active material has a high specific capacity. After being embedded in the pores 2 of the porous current collector 1, the porous current collector 1 can effectively suppress the volume expansion of the preferred active material due to intercalation of lithium ions, and endow the composite Higher specific capacity of the negative electrode.

Furthermore, the inventors also found in the research that the specific capacity of the active material can be further improved by controlling the particle size of the above-mentioned active material capable of intercalating lithium ions within a certain range. In a preferred embodiment, the above-mentioned elemental nano particles, nano oxide particles, and nano alloy particles have a particle diameter of 1-800 nm, more preferably 80-200 nm. Nanowires, nanotubes, nanofibers, and nanofilms can all be selected from conventional models in the field.

Certainly, the above-mentioned active filler 3 also contains a binder and a conductive agent in addition to the above-mentioned active material capable of intercalating lithium ions. As a preferred embodiment, the weight ratio between the adhesive, the conductive agent and the above-mentioned active material capable of intercalating lithium ions is (1~15):(0~15):100 where the addition of the conductive agent can Together with the active material, the charge-discharge performance of the above composite negative electrode is enhanced; the addition of the binder enhances the bonding strength between the active fillers 3 and between the active filler 3 and the porous current collector 1, avoiding the active filler 3 It falls out of the hole 2 of the porous current collector 1. The binder is preferably at least one of sodium carboxymethylcellulose (CMC), styrene-butadiene rubber (SBR), and polyvinylidene fluoride (PVDF); the conductive agent is preferably SP conductive agent, vapor-phase grown carbon fiber ( VGCF), carbon nanotubes (CNTs), and graphene (Graphene). Of course, other adhesives and conductive agents commonly used in the art can also be used as the type of adhesive and conductive agent.

From the above, the composite negative electrode in the above embodiment embeds the active material capable of intercalating lithium ions into the porous structure of the porous current collector, so that the porous structure can effectively inhibit the volume expansion of the active material due to intercalation of lithium ions. , thereby avoiding pulverization and falling off, thereby enhancing the electrical contact between the active material and the current collector and the capacity of the composite negative electrode. At the same time, the active material is dispersed in the porous structure of the current collector, which can effectively avoid the pulverization phenomenon caused by the agglomeration of the particles of the active material, and enhance the strength of the combination of the active material and the current collector, thus ensuring the high efficiency of the active material. The specific capacity prolongs the cycle life and capacity of the composite negative electrode. In addition, the above-mentioned composite negative electrode adopts a porous current collector with a porous structure, which enhances its mechanical strength, facilitates its mechanical winding, and enhances its shape stability.

The example of the present invention also provides a method for preparing the above-mentioned composite negative electrode with a simple process. Please refer to Figure 5 for the process flow of the method for preparing the composite negative electrode, and refer to Figures 1 and 2 at the same time. The method for preparing the composite negative electrode includes the following steps:

S01. Prepare active material-containing slurry: disperse conductive agent, binder, and the above-mentioned active material capable of intercalating lithium ions in an aqueous or oily solvent, and prepare active material-containing slurry; wherein, the adhesive, The weight ratio of conductive agent to active material is (1~15):(0~15):100, and the content of active material in the slurry is 20~70%;

S02. Inject slurry: inject the slurry prepared in step S01 into the hole 2 of a porous current collector 1 and dry to obtain the composite negative electrode; or inject the slurry prepared in step S01 into at least two porous current collectors 1 The holes 2 are dried, and then the porous current collector 1 is laminated and integrated by hot pressing, rolling or/and sintering to obtain the composite negative electrode.

Specifically, as a preferred embodiment, in the above step S01, the method of dispersing the conductive agent, the binder and the active material in the water-based or oily solvent is: first dispersing the conductive agent, the binder in the water-based or oily solvent, Form the conductive adhesive, and then disperse the active material in the conductive adhesive to prepare a uniformly dispersed and stable slurry. After the uniformly dispersed and stable slurry is injected into the pores 2 of the porous current collector 1, the active material can be evenly distributed in the porous current collector 1, thereby improving the capacity of the composite negative electrode of the embodiment of the present invention.

Of course, the method of dispersing the conductive agent, binder and active material in the above step S01 in an aqueous or oily solvent can also be to mix the conductive agent, binder and active material first, and then disperse the mixture to an aqueous or oily solvent. Solvent, so that each component is uniformly dispersed, and formulated into an emulsion. It is also possible to add the conductive agent, the binder and the active material together into the water-based or oil-based solvent, and then disperse evenly to form an emulsion.

In this step S01 , the types of the conductive agent, the binder, and the active material capable of intercalating lithium ions are as described above, and will not be repeated here in order to save space. The aqueous solvent is preferably at least one of purified water, deionized water, and tap water, and the oily solvent is preferably at least one of N-methylpyrrolidone, ethanol, propanol, and cyclohexane.

In the above-mentioned step S02, the way of injecting the above-mentioned slurry into the holes 2 of the porous current collector 1 is preferably one or a combination of two or more of pouring, deposition, coating, spraying, and soaking. This preferred injection method can uniformly inject the slurry into the pores 2 of the porous current collector 1, so that the active material can be evenly distributed in the porous current collector 1, thereby improving the capacity of the composite negative electrode of the embodiment of the present invention. The injection amount should make the slurry fill the pores 2 of the porous current collector 1 to the greatest extent.

In this step S02 , the drying treatment process is to dry the slurry coated in the pores 2 of the porous current collector 1 to form active fillers 3 . The drying process can be carried out by conventional drying methods in the art, such as drying under vacuum conditions, or air drying, air drying or drying in the air.

In this step S02, when there are more than two hole collectors 1, the slurry is injected into the holes 2 of each hole collector 1, after drying, the dried hole collectors 1 are stacked, and then heated Combination of pressing, rolling or/and sintering. The hot pressing, rolling and sintering can be carried out by conventional methods in the field. In order to make the laminated porous current collectors 1 more closely combined without causing damage to the porous current collectors 1 and active fillers 3, the conditions of hot pressing, rolling or/and sintering treatment can be adjusted according to the material selection of the porous current collectors 1. Flexible adjustment.

From the above, the preparation method of the composite negative electrode in the above embodiment only needs to prepare the active material with the ability to intercalate lithium ions into a slurry, and then directly inject it into the porous structure of the current collector for drying, or further dry the The composite negative electrode can be obtained by hot pressing, rolling or/and sintering the final current collector. The preparation method has the advantages of simple process, easy control of conditions, high production efficiency, reduced production cost, and effectively avoids the shortcomings of complex process, low production efficiency, high cost and low specific energy of the battery in the existing electrodeposition method for producing composite electrodes. .

The embodiment of the present invention also improves an electrochemical power source capable of charging and discharging with a large current and taking into account high specific energy and power. Preferably, the electrochemical power source in the above embodiment is preferably a chemical lithium battery for electrochemical reaction or a composite lithium capacitor for electrochemical reaction. Specifically, the chemical lithium battery for the electrochemical reaction is a lithium-ion battery, lithium polymer battery, lithium-sulfur battery or lithium-air battery; the composite lithium capacitor for the electrochemical reaction is a lithium-ion capacitor.

As an embodiment of the present invention, the above-mentioned electrochemical power source is a lithium battery, including components such as a casing, an electrolyte, and a battery cell, wherein the battery cell includes a positive electrode/diaphragm/negative electrode stacked in sequence, and the negative electrode is the above-mentioned The composite negative electrode described above, in order to save space, the structure and performance of the composite negative electrode will not be repeated here. The positive electrode and separator in the lithium battery can be those commonly used in the art. Wherein, the structure of the positive electrode can also adopt the structure of the composite negative electrode in the above-mentioned embodiments, the difference is that the pores of the porous current collector of the positive electrode are filled with active fillers, and the active fillers contain adhesive agent, conductive agent and positive electrode active material capable of intercalating lithium ions.

As another embodiment of the present invention, the above-mentioned electrochemical power supply is a composite lithium capacitor, including components such as a housing, an electrolyte, and a battery cell, wherein the battery cell includes sequentially stacked electrodes/diaphragms/electrodes, and the electrodes are the above-mentioned For the composite negative electrode, in order to save space, the structure and performance of the composite negative electrode will not be repeated here. The diaphragm can be commonly used in this field.

The electrochemical power source of the above embodiment contains the above-mentioned composite negative electrode, and it is precisely because of the high capacity of the composite negative electrode that the electrochemical power source, such as a lithium battery, is endowed with a high specific energy. In addition, the volume of the above-mentioned composite negative electrode is stable during the charging and discharging process, thus endowing the electrochemical power source with excellent cycle stability performance, prolonging the cycle life of the electrochemical power source, and enhancing the safety of the electrochemical power source. At the same time, because the above-mentioned active material in the above-mentioned composite negative electrode is embedded in the porous structure of the current collector, the distance between the active material and the current collector is short, the electron transmission path is shortened, and the electrochemical power supply has high-current charge and discharge characteristics and high power.

The following examples illustrate the composite negative electrode, its preparation method, lithium battery, and its performance.

Example 1

A composite negative electrode and its preparation method:

The structure of the composite negative electrode is shown in FIGS. 2 and 3 , which includes a nickel foam current collector 1 and its meshes 2 are filled with active fillers 3 . The thickness of the nickel foam 1 is 150 μm, and the active filler 3 contains a binder, a conductive agent and an active material capable of intercalating lithium ions in a weight ratio of 8:3:89. Among them, the binder is CMC, the conductive agent is SP, and the active material capable of intercalating lithium ions is a nano-powder mixture of Si, SiO ₂ and graphite in a weight ratio of 40:10:50.

The method of the composite negative electrode:

S11. Preparation of slurry containing active substances: Add active substance powder (active substance is not a simple powder mixture, but sintered by a certain process, and it is already a uniformly dispersed compound) into pure water, and disperse by ultrasonic waves Uniform; disperse CMC and SP in pure water to prepare conductive adhesive; mix the solution dispersed with active material with conductive adhesive to prepare a uniform slurry; among them, the weight ratio of SP, CMC and active material is 3: 8:89, the concentration of the active substance in the slurry is 35%;

S12. Preparation of slurry containing active substances: Soak the nickel foam 1 in the slurry prepared in step S11 to absorb sufficient slurry in the pores of the nickel foam, take it out and dry it, and obtain a composite negative electrode sheet.

The composite negative electrode sheet prepared in Example 1 is used to prepare a polymer lithium battery: the composite negative electrode sheet prepared in Example 1, the diaphragm material, and the positive electrode sheet of nickel cobalt aluminate (NCA) are wound The method is prepared into a prismatic polymer battery.

Example 2

A composite negative electrode and its preparation method:

The composite negative electrode structure is shown in Figures 2 and 4, which includes two layers of copper mesh collectors 11 and 12 that are laminated and integrated into one, and active fillers that fill the holes 2 of the copper mesh collectors 11 and 12. 3. The thickness of the copper mesh current collectors 11 and 12 is 50 μm, and the active filler 3 contains a binder, a conductive agent and an active material capable of intercalating lithium ions in a weight ratio of 6:3:91. Among them, the binder is PVDF, the conductive agent is VGCF, and the active material capable of intercalating lithium ions is nano-scale stannous oxide powder.

The method of the composite negative electrode:

S21. Preparation of slurry containing active substances: Add PVDF to NMP solvent to prepare a gel solution, then add the mixture of nano-stannous oxide powder and VGCF conductive agent mixed uniformly in advance to the glue liquid and make a uniform slurry ; Among them, the weight ratio of PVDF, VGCF and nano stannous oxide powder is 6:3:91, and the concentration of nano stannous oxide powder in the slurry is 30%;

S22. Preparation of slurry containing active substances: pour the slurry prepared in step S21 into the holes 2 of the two copper mesh current collectors 11, 12, dry to make two single-layer electrode pole pieces, and then put the two pieces together The single-layer electrode pole pieces are stacked, and the two stacked single-layer electrode pole pieces are combined into one body through high-temperature hot pressing at 150°C to obtain a composite negative electrode pole piece.

The composite negative electrode pole piece prepared in this embodiment 2 is used to prepare a polymer lithium battery: the composite negative electrode pole piece prepared in this embodiment 2 is cut into small pieces, and the separator material, nickel cobalt lithium manganate ternary positive electrode The small pole pieces are prepared into a square flexible packaging battery by Z-shaped lamination.

Example 3

A composite negative electrode and its preparation method:

The composite negative electrode structure is shown in Figures 2 and 5, which includes three layers of stainless steel mesh collectors 11, 12 and 13 that are stacked together and integrated into one, and filled in the holes 2 of the stainless steel mesh collectors 11, 12 and 13 active filler3. The stainless steel mesh collectors 11, 12 and 13 have a thickness of 40 μm, and the active filler 3 contains a binder, a conductive agent and an active material capable of intercalating lithium ions in a weight ratio of 6:2:92. Among them, the binder is CMC+SBR (weight ratio 1:1), the conductive agent is CNTs, and the active material capable of intercalating lithium ions is nano-scale silicon-carbon composite powder (the content of Si in the composite is 40%) .

The method of the composite negative electrode:

S31. Prepare slurry containing active substances: add SP to CMC+SBR solvent to prepare conductive adhesive, then add nano-scale silicon powder to conductive adhesive and make uniform slurry; wherein, CMC+SBR, CNTs The weight ratio of the nano-scale silicon-carbon compound to the three is 6:2:92, and the concentration of the nano-scale silicon-carbon compound in the slurry is 42%;

S32. Preparation of slurry containing active substances: pour the slurry prepared in step S31 into the holes 2 of three stainless steel mesh collector fluids 11, 12 and 13, and dry to make three single-layer electrode sheets, and then put Three single-layer electrode sheets are laminated, and the laminated three single-layer electrode sheets are pressed into one body by hot pressing at 120° C. to obtain a composite negative electrode sheet.

The composite negative electrode pole piece prepared in this Example 3 is used to prepare a polymer lithium battery: the composite negative electrode pole piece prepared in this Example 3, the diaphragm material, and the lithium cobaltate positive pole piece are prepared into a square aluminum shell battery.

Lithium battery performance test:

The rate discharge performance and cycle performance tests were performed according to the above-mentioned Examples 1 to 3 and the existing lithium battery (battery model 454261P) as a comparative example, and the rate discharge performance and cycle performance tests can be tested according to methods known in the art. The results are shown in Table 1. Among them, the cycle performance test results are shown in Figure 7, and the rate discharge performance test is shown in Table 1 below:

Table 1

As can be seen from Table 1, the lithium ion battery prepared using the composite negative electrode prepared by the present invention has a higher capacity, which is more than 20% higher than the capacity of conventional graphite electrodes; The battery has better rate performance.

It can be seen from Figure 7 that the lithium ion battery prepared by using the composite negative electrode prepared by the present invention has relatively good cycle stability, and the capacity retention rate is still greater than 75% after 200 cycles. If converted into capacity, after 200 cycles Its discharge capacity is superior to lithium-ion batteries composed of graphite electrodes.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention should be included in the protection of the present invention. within range.

Claims (12)

1. A composite negative electrode, comprising 3 to 5 layers of laminated porous current collectors and active fillers, the active fillers are filled in the holes of the porous current collectors, and the active fillers contain binders, Conductive agent and active material with the ability to intercalate lithium ions, the active material accounts for 80-98% of the total weight of the active filler; the porous current collector is foamed nickel, foamed copper, foamed aluminum, foamed carbon, not Embroidered steel mesh, nickel mesh, copper mesh or aluminum mesh; the active substance is at least one of elemental nanometer particles, nanowires, nanotubes, nanofibers, nanofilms, nanoscale oxide particles, and nanoalloy particles ,or The active substance is a composite of at least one of elemental nanoparticle, nanowire, nanotube, nanofiber, nanofilm, nanooxide particle, and nanoalloy particle of M element with carbon; Wherein, the M element is at least one of Si, Sn, Al, Sb, Ge, Zn, Pb, Mg, and Na. 2. composite negative electrode as claimed in claim 1, is characterized in that, at least one in the nano element particle of described M element, nanowire, nanotube, nanofiber, nanofilm, nano oxide particle, nanoalloy particle In the composite of species and carbon, the weight content of the M element active material in the composite is 10-98%. 3. The composite negative electrode according to claim 1 or 2, characterized in that the particle size of the nano elemental particles, nano oxide particles or nano alloy particles is 1-800 nm. 4. The preparation method of the composite negative electrode as described in any one of claims 1 to 3, comprising the steps of: The conductive agent, the binder and the active material with the ability to intercalate lithium ions are dispersed in an aqueous or oily solvent to prepare a slurry containing the active material; wherein the active material, the conductive agent, and the binder are The weight ratio is 100:(0-15):(1-15), and the content of the active substance in the slurry is 20%-70%; The slurry is injected into the holes of at least two porous current collectors, dried, and then the dried porous current collectors are stacked and combined by hot pressing, rolling or/and sintering to obtain the composite negative electrode. 5. the preparation method of composite negative electrode as claimed in claim 4 is characterized in that, the mode that described slurry is injected in the hole of porous current collector is one of pouring, depositing, coating, spraying, soaking, printing. one or a combination of two or more. 6. the preparation method of composite negative electrode as claimed in claim 4 is characterized in that, described aqueous solvent is at least one of pure water, distilled water, tap water; The oily solvent is at least one of N-methylpyrrolidone, ethanol, propanol, and cyclohexane. 7. An electrochemical power source, comprising the composite negative electrode according to any one of claims 1-3. 8. The electrochemical power supply according to claim 7, characterized in that, the electrochemical power supply is a chemical lithium battery of electrochemical reaction or a composite lithium capacitor of electrochemical reaction. 9. The electrochemical power supply according to claim 8, wherein the chemical lithium battery of the electrochemical reaction is a liquid lithium ion battery, a lithium polymer battery, a lithium sulfur battery or a lithium air battery. 10. The electrochemical power supply according to claim 9, wherein the composite lithium capacitor is a lithium ion capacitor. 11. The application of the electrochemical power source according to any one of claims 7 to 10 in mobile terminal products, power grids, communication equipment and/or electric tools. 12. The application of electrochemical power supply as claimed in claim 11, characterized in that: said communication device comprises a working module and a power supply module, said power supply module comprises said electrochemical power supply, and said electrochemical power supply is an electrochemical reaction The chemical lithium battery; the power supply module provides electric energy for the working module, and the working module uses the electric energy provided by the power supply module to run.