CN114242989B - A kind of composite electrode material and its preparation method and application - Google Patents

Abstract

The invention provides a composite electrode material and a preparation method and application thereof, the composite electrode material comprises a pole piece substrate and an artificial solid electrolyte layer coated on the surface of the pole piece substrate, the artificial solid electrolyte layer is composed of a first polymer, and the structure of the first polymer is shown as formula I:

(formula I); wherein n = 10-1000; the pole piece substrate is at least one of lithium metal or a composite material containing metal lithium. According to the invention, the ether side group-containing copolymer is coated on the surface of the electrode substrate as the artificial solid electrolyte layer to protect the electrode substrate, the interface of the solid electrolyte layer has high ion conductivity and strong lithium affinity, lithium ions are induced to be uniformly deposited while the electrolyte is prevented from reacting with the electrode substrate, the interface of the electrode substrate is stabilized, and further the consumption of the electrolyte is reduced.

Description

A composite electrode material and its preparation method and application

technical field

The invention relates to the field of composite electrode preparation, and more particularly, to a composite electrode material and a preparation method and application thereof.

Background technique

With the rapid development of society, the demand for electric vehicles and consumer electronic products is increasing day by day, and finding new energy materials to replace the original petrochemical materials has become an important issue in the development of the new era. Lithium metal as a battery anode material can provide extremely high specific capacity (3860mAh/g) and a larger operating voltage window (reduction electrode potential -3.04V), which is an effective next-generation new energy material. However, the high activity of metal lithium itself, large volume deformation and lithium dendrite problems have always been obstacles that limit the application of metal lithium anodes. At present, the main problems of metal lithium as the negative electrode of lithium batteries are as follows: (1) the volume deformation of metal lithium is very large during the charging and discharging process, resulting in large expansion and contraction of the battery; (2) the metal lithium is deposited due to the power Due to chemical and thermodynamic reasons, lithium dendrites are easy to grow, which will not only form dead lithium, reduce the negative electrode capacity and increase the polarization of the battery, but also may cause internal short circuit, which may lead to battery failure or even fire and explosion. In addition, the low reduction potential of lithium makes it unstable in conventional electrolytes, causing the electrolyte to reduce on the lithium metal surface to form a passivation layer (often referred to as the "solid electrolyte interface (SEI)"). Defects and cracks in SEI can lead to local Li-ion enrichment and dendrite growth, while increasing the surface area of Li anode, leading to irreversible consumption of active Li, forming new SEI on its surface. The vicious cycle of these two behaviors leads to the continuous reduction of battery capacity and low Coulomb efficiency, which seriously hinders the application and development of lithium batteries.

Therefore, the dynamic stability of SEI is crucial for obtaining excellent energy storage performance and long cycle life. At present, there are few reports on obtaining energy storage performance and stable cycle life by maintaining the dynamic stability of SEI.

SUMMARY OF THE INVENTION

Based on the above technical problems existing in the prior art, one of the objectives of the present invention is to provide a composite electrode material, which protects the electrode substrate by covering the surface of the electrode substrate with the ether side group-containing copolymer as an artificial solid electrolyte layer. The interface of the solid electrolyte layer has high ionic conductivity and strong lithiophilicity, which induces uniform deposition of lithium ions and prevents the electrolyte from reacting with the electrode matrix, thereby stabilizing the electrode matrix interface, thereby reducing the consumption of electrolyte.

In order to achieve the above object, technical scheme of the present invention is as follows:

A composite electrode material, comprising a pole piece base body and an artificial solid state electrolyte layer coated on the surface of the pole piece base body, the artificial solid state electrolyte layer is composed of a first polymer, and the first polymer structure is as shown in formula I Show:

（式I）；其中，n=10~1000；所述极片基体为锂金属或者含金属锂的复合材料中的至少一种。具体为由锂金属和/或含金属锂的复合材料制备的极片。

(Formula I); wherein, n=10~1000; the pole piece substrate is at least one of lithium metal or a composite material containing metallic lithium. Specifically, the pole pieces are prepared from lithium metal and/or metal lithium-containing composite materials.

In some embodiments, the first polymer is prepared by reacting a second polymer of formula II with lithium metal,

（式II）。

(Formula II).

In some embodiments, the thickness of the artificial solid electrolyte layer is 5-100 nm; and/or the thickness of the pole piece base body is 5 μm-1.5 mm.

In some embodiments, the metal lithium-containing composite material includes at least one of lithium alloy, lithium-boron composite material, porous framework lithium-filled metal, porous framework lithium-filled alloy, and porous framework lithium-boron composite material.

In some embodiments, the lithium alloy has the formula Li _{x My} , and M is selected from sodium, carbon, silicon, magnesium, aluminum, indium, silver, gold, scandium, titanium, vanadium, chromium, manganese, iron, cobalt, Nickel, copper, zinc, gallium, germanium, tin, yttrium, zirconium, niobium, molybdenum, technetium, ruthenium, rhodium, palladium, cadmium, antimony, hafnium, tantalum, tungsten, rhenium, iridium, platinum, mercury, thallium, lead, At least one of bismuth and polonium; x is 0.65~0.95, y is 0.05~0.35.

In some embodiments, the lithium-boron composite material includes a composite material with a content of lithium and boron elements of more than 70% by mass. Specifically, in terms of mass percentage, the lithium-boron composite material is composed of 65%-95% lithium , 5%~35% boron and 0~30% N, the N is selected from sodium, carbon, silicon, magnesium, aluminum, indium, silver, gold, scandium, titanium, vanadium, chromium, manganese, iron, cobalt, Nickel, copper, zinc, gallium, germanium, tin, yttrium, zirconium, niobium, molybdenum, technetium, ruthenium, rhodium, palladium, cadmium, antimony, hafnium, tantalum, tungsten, rhenium, iridium, platinum, mercury, thallium, lead, At least one of bismuth and polonium.

In some embodiments, the porous framework is at least one of foamed copper, foamed nickel, copper mesh, nickel mesh, carbon cloth, carbon paper powder metallurgy porous copper, powder metallurgy porous nickel, porous stainless steel, and porous polymer fibers .

Another object of the present invention is to provide a method for preparing the composite electrode material according to any of the above embodiments, the method comprising the following steps:

S1. Preparation of the second polymer: ring-opening the styrene maleic anhydride copolymer with (R)-(2,2-dimethyl-1,3-dioxolan-4-yl)methylamine reaction to obtain a second polymer;

S2, mixing the second polymer with an organic solvent, heating and dissolving to obtain a homogeneous solution;

S3, soaking the pole piece substrate in the solution for reaction, taking it out, drying to remove the solvent, and obtaining a composite electrode material whose surface is coated with the first polymer.

In some embodiments, the organic solvent is N,N-dimethylformamide; preferably, the concentration of the solution is 0.005-100 g/L.

In some embodiments, in step S3, the soaking time is 1-120 min.

In some embodiments, in step S3, the drying temperature is 20-80° C., and the time is 0.5-30 h.

The third object of the present invention is to provide a battery comprising the composite electrode material of any of the above embodiments or the composite electrode material obtained by the preparation method of any of the above embodiments.

Compared with the prior art, the beneficial effects of the present invention are as follows:

(1) The present invention protects the lithium negative electrode by covering the surface of the electrode substrate with a copolymer material containing ether side groups as an artificial solid-state electrolyte interface. The copolymer has high lithium ion conductivity and strong lithiophilicity, and can induce lithium ions. The uniform deposition keeps the surface of the negative electrode dynamically stable; at the same time, the reaction between the electrolyte and the lithium negative electrode is prevented, and the interface of the lithium negative electrode is stabilized, which not only reduces the consumption and loss of the electrolyte, but also effectively improves the cycle of the composite electrode material in the ester electrolyte. life, thereby improving the cycle life of the energy storage device.

(2) The composite electrode material obtained by the method of the present invention is used in lithium batteries, and the symmetrical battery can reach 700 hours under the conditions of a current density of 1 mA/cm ² and an area specific capacity of 1 mAh/cm ² It can maintain a low polarization voltage (less than 30 mV) for a long time cycle; the charge-discharge specific capacity of the Li|LiFePO ₄ full battery paired with lithium iron phosphate is 156 mAh/g at the initial rate of 1 C. , after stable cycling to 200 cycles, there is still no attenuation, and the Coulomb efficiency remains 100%, which has a good effect on improving the performance of lithium metal batteries.

(3) The preparation method provided by the present invention has the advantages of simple process and convenient preparation, and is suitable for industrial production.

Description of drawings

Fig. 1 is the voltage-time curve of the pure lithium metal symmetrical battery made in Example 1 and Comparative Example 1;

Fig. 2 is the rate performance of pure lithium metal full battery obtained in Example 1 and Comparative Example 1;

Fig. 3 is the voltage-time curve of the lithium-boron alloy symmetrical battery prepared in Example 2 and Comparative Example 2;

Fig. 4 is the voltage-time curve of the Li-B-Ag alloy symmetric battery prepared in Example 3 and Comparative Example 3;

Fig. 5 is the voltage-time curve of the Li-B-Zn alloy symmetrical battery obtained in Example 4 and Comparative Example 4;

FIG. 6 is the voltage-time curves of the Li-B-Cu alloy symmetric cells prepared in Example 5 and Comparative Example 5. FIG.

Detailed ways

In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific implementation disclosed below.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terms used herein in the description of the present invention are for the purpose of describing specific embodiments only, and are not intended to limit the present invention.

In the embodiments of the present invention, unless otherwise specified, the chemical reagents used can be obtained through purchase or prepared by existing preparation methods, and the used instruments and equipment are conventional equipment in the prior art.

In the following examples of the present invention, the reaction of the first polymer and the second polymer is shown in the following reaction formula: styrene maleic anhydride copolymer (SMA) with (R)-(2,2-dimethyl- 1,3-dioxolane-4-yl)methylamine (DMDOL) undergoes a ring-opening reaction to obtain the second polymer; the obtained product is dissolved in DMF (N,N-dimethylformamide) and reacted with the negative electrode. The lithium metal reacts to generate an artificial solid-state electrolyte membrane in situ, and the intermediate is dried in a vacuum oven to obtain a modified negative electrode:

。

.

Example 1

SMA and (R)-(2,2-dimethyl-1,3-dioxolan-4-yl)methylamine (DMDOL) were added to DMF in a ratio of 1:2 (MAn units:DMDOL), Under vacuum conditions, it was placed in an oil bath at 60 °C for 24 h. The product was recrystallized from toluene, and the filtrate was dried to obtain (R)-(2,2-dimethyl-1,3dioxolane-4). - group) methylamine pendant styrene ring-opening maleic anhydride (SMA-DMDOL), the product molecular weight M _n =4319, M _w =7769.

The prepared SMA-DMDOL was dissolved in anhydrous DMF, configured into a 5 M solution, and the thick lithium sheet was soaked in the solution for 30 minutes, then taken out and dried in a vacuum oven to obtain a solution containing (R)- (2,2-Dimethyl-1,3dioxolan-4-yl)methylamine pendant polystyrene ring-opened maleic anhydride for artificial solid-state electrolyte interface modification of lithium metal anode.

All the above operations were performed in the glove box.

The modified lithium metal anode was electrochemically tested with commercial pure lithium in electrolyte (1M LiPF ₆ , EC:EMC:FEC=3:7:1 (v/v)) at a current density of 1 mA/cm ² , under the condition of 1 mAh/cm ² area specific capacity, the symmetrical battery can achieve long-term cycling of 700 hours and still maintain a low polarization voltage (less than 30 mV).

The Li|LiFePO ₄ full battery composed of the modified lithium metal negative electrode paired with lithium iron phosphate has a charge-discharge specific capacity of 156 mAh/g at the initial rate of 1 C, and there is still no attenuation after stable cycling to 200 cycles. Efficiency is always 100%. Good performance in rate galvanostatic charge-discharge cycle tests at 0.1 C, 0.2 C, 0.5 C, 1 C, 2 C, 5 C, 0.1 C: the specific capacity remains above 150 mAh/g during low current cycling, even if It can maintain a stable specific capacity of 135 mAh/g under the condition of high current 5 C, and reach more than 99% of the first cycle capacity when returning to a rate of 0.1 C, fully demonstrating the good performance of the negative electrode after surface modification. performance; the test results are shown in Figure 1.

Example 2

Similar parallel experiments were carried out in this example and Example 1. The difference is that the lithium metal was changed to 84Li-B alloy, and the other preparation methods were exactly the same as those in Example 1. -1,3-dioxolane-4-yl) methylamine pendant polystyrene ring-opening maleic anhydride artificial solid-state electrolyte modified lithium boron alloy negative electrode.

The modified lithium-boron alloy anode and the bare lithium-boron alloy anode were electrochemically tested in electrolyte (1M LiPF ₆ , EC:EMC:FEC=3:7:1 (v/v)) at 1 mA/cm ² At the current density of 1 mAh/cm ² , the symmetric cell can achieve a long-term cycle of 400 hours and still maintain a low polarization voltage (less than 50 mV). The test results are shown in Figure 2.

Example 3

Similar parallel experiments were carried out in this example and Example 1, the difference is that the lithium metal was changed to Li-B-Ag alloy, and the other preparation methods were exactly the same as those in Example 1. Artificial solid-state electrolyte interface modification of Li-B-Ag alloy anode with methyl-1,3dioxolan-4-yl)methylamine pendant polystyrene ring-opening maleic anhydride.

The modified Li-B-Ag alloy anode and bare Li-B-Ag alloy anode were electrochemically tested in electrolyte (1M LiPF ₆ , EC:EMC:FEC=3:7:1 (v/v)), At a current density of 1 mA/cm ² and an areal specific capacity of 10 mAh/cm ² , the symmetric cell can achieve a long cycle of 800 hours and still maintain a low polarization voltage (less than 40 mV). The test results are shown in Figure 3.

Example 4

Similar parallel experiments were carried out in this example and Example 1, the difference is that the lithium metal was changed to Li-B-Zn alloy, and the other preparation methods were exactly the same as those in Example 1. Artificial solid-state electrolyte interfacial modification of Li-B-Zn alloy anode with polystyrene ring-opening maleic anhydride with methyl-1,3-dioxolan-4-yl)methylamine side groups.

The modified Li-B-Zn alloy anode and bare Li-B-Zn alloy anode were electrochemically tested in electrolyte (1M LiPF ₆ , EC:EMC:FEC=3:7:1 (v/v)), At a current density of 1 mA/cm ² and an areal specific capacity of 5 mAh/cm ² , the symmetric cell can achieve long-term cycling of 1000 hours and still maintain a low polarization voltage (less than 100 mV). The test results are shown in Figure 4.

Example 5

Similar parallel experiments were carried out in this example and Example 1. The difference is that the lithium metal is changed to Li-B-Cu alloy, and the other preparation methods are exactly the same as those in Example 1. Artificial solid-state electrolyte interface modification of Li-B-Cu alloy anode with methyl-1,3-dioxolan-4-yl)methylamine pendant polystyrene ring-opening maleic anhydride.

The modified Li-B-Cu alloy anode and bare Li-B-Cu alloy anode were electrochemically tested in electrolyte (1M LiPF ₆ , EC:EMC:FEC=3:7:1 (v/v)), At a current density of 1 mA/cm ² and an areal specific capacity of 5 mAh/cm ² , the symmetric cell can achieve a long cycle of 1100 hours and still maintain a low polarization voltage (less than 50 mV). The test results are shown in Figure 5.

Comparative Example 1

The difference between Comparative Example 1 and Example 1 is that the lithium metal used is not modified, and the test results are shown in FIG. 1 .

Comparative Example 2

The difference between Comparative Example 2 and Example 2 is that the lithium-boron alloy used is unmodified, and the test results are shown in Figure 2 .

Comparative Example 3

The difference between Comparative Example 3 and Example 3 is that the Li-B-Ag alloy used is unmodified, and the test results are shown in FIG. 3 .

Comparative Example 4

The difference between Comparative Example 4 and Example 4 is that the Li-B-Zn alloy used is unmodified, and the test results are shown in FIG. 4 .

Comparative Example 5

The difference between Comparative Example 5 and Example 5 is that the Li-B-Cu alloy used is not modified, and the test results are shown in FIG. 5 .

The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity, all possible combinations of the technical features in the above-described embodiments are not described. However, as long as there is no contradiction between the combinations of these technical features, All should be regarded as the scope described in this specification.

The above-mentioned embodiments only represent several embodiments of the present invention, and the descriptions thereof are specific and detailed, but should not be construed as a limitation on the scope of the invention patent. It should be pointed out that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can also be made, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention should be subject to the appended claims.

Claims (10)

1. The composite electrode material is characterized by comprising a pole piece substrate and an artificial solid electrolyte layer coated on the surface of the pole piece substrate, wherein the artificial solid electrolyte layer is composed of a first polymer, and the structure of the first polymer is as shown in formula I:

(formula I); wherein n = 10-1000; the pole piece substrate is at least one of lithium metal or a composite material containing metal lithium.

2. The composite electrode material of claim 1, wherein the first polymer is prepared by reacting a second polymer having a structure of formula II with lithium metal,

(formula II).

3. The composite electrode material according to claim 1, wherein the artificial solid electrolyte layer has a thickness of 5 to 100 nm; and/or the thickness of the pole piece substrate is 5 micrometers-1.5 mm.

4. The composite electrode material of claim 1, wherein the lithium metal-containing composite material comprises at least one of a lithium alloy, a lithium boron composite material, a porous framework lithium-filled metal, a porous framework lithium-filled alloy, and a porous framework lithium boron-filled composite material.

5. A composite electrode material according to claim 4, characterized in that the lithium is alloyedHas a chemical formula of Li_xM_yM is selected from at least one of sodium, carbon, silicon, magnesium, aluminum, indium, silver, gold, scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, gallium, germanium, tin, yttrium, zirconium, niobium, molybdenum, technetium, ruthenium, rhodium, palladium, cadmium, antimony, hafnium, tantalum, tungsten, rhenium, iridium, platinum, mercury, thallium, lead, bismuth, polonium; x is 0.65 to 0.95, and y is 0.05 to 0.35.

6. The composite electrode material of claim 4, wherein the lithium boron composite material consists of, in mass percent, 65% to 95% lithium, 5% to 35% boron, and 0 to 30% N selected from at least one of sodium, carbon, silicon, magnesium, aluminum, indium, silver, gold, scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, gallium, germanium, tin, yttrium, zirconium, niobium, molybdenum, technetium, ruthenium, rhodium, palladium, cadmium, antimony, hafnium, tantalum, tungsten, rhenium, iridium, platinum, mercury, thallium, lead, bismuth, and polonium.

7. The composite electrode material of claim 4, wherein the porous framework is at least one of copper foam, nickel foam, copper mesh, nickel mesh, carbon cloth, carbon paper, powder metallurgy porous copper, powder metallurgy porous nickel, porous stainless steel, and porous polymer fiber.

8. A method of preparing a composite electrode material according to any one of claims 1 to 7, comprising the steps of:

s1, preparation of second polymer: carrying out ring-opening reaction on the styrene maleic anhydride copolymer and (R) - (2, 2-dimethyl-1, 3-dioxolane-4-yl) methylamine to obtain a second polymer;

s2, mixing the second polymer with an organic solvent, and heating for dissolving to obtain a uniform solution;

and S3, soaking the pole piece substrate in the solution for reaction, taking out, drying and removing the solvent to obtain the composite electrode material with the surface coated with the first polymer.

9. The method for preparing the composite electrode material according to claim 8, wherein the organic solvent is N, N-dimethylformamide, and the solution concentration is 0.005 to 100 g/L.

10. A battery comprising the composite electrode material according to any one of claims 1 to 7.

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