Composite electrode material and preparation method thereof

Abstract

The invention discloses a composite electrode material and a preparation method thereof, and belongs to the technical field of lithium-free negative electrode batteries. The composite electrode material comprises an electrode current collector, a conductive carbon layer and a polymer layer, the conductive carbon layer is located between the electrode current collector and the polymer layer, and the conductive carbon layer comprises large-particle porous carbon with the particle size not smaller than 50 microns. A composite layer of a polymer layer and a conductive carbon layer is adopted as a current collector modification layer, and the polymer layer can effectively improve the lithium affinity of the material and optimize the deposition behavior of lithium ions; the conductive carbon layer of large-particle porous carbon introduced between the polymer layer and the current collector can significantly improve the stability of the polymer layer, prevent the structure of the polymer layer from collapsing, improve the structural stability of the electrode, increase the conductive area of the conductive interface of the electrode, effectively improve the wettability of the electrolyte and reduce the surface current density of the battery. And the stability and the cycle life of the battery are enhanced.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium-free negative electrode batteries, and in particular relates to a composite electrode material and a preparation method thereof. Background Art

[0002] Lithium-free negative electrode batteries are a new type of lithium battery technology that greatly reduces the proportion of lithium content in the battery system and greatly improves safety. Lithium-free negative electrode batteries do not have an independent lithium negative electrode, and all the active lithium of the battery is initially stored in the positive electrode material. During the charging stage, the active lithium is released from the positive electrode material and directly electroplated in situ on the negative electrode current collector. During the discharge stage, the negative electrode lithium is stripped and converted into lithium ions. The lithium ions migrate from the negative electrode to the positive electrode and return to the positive electrode material structure, restoring the state of no lithium at the negative electrode and storing lithium at the positive electrode, completing a cycle.

[0003] Copper is widely used as a current collector on the anode side of batteries due to its excellent conductivity, good ductility, and stability at low potentials. However, commercially available copper current collectors contain microcracks and pits at the micro- and nanoscale. These defects lead to uneven lithium deposition, which in turn causes uneven local current density distribution, increases the internal resistance of the battery, and ultimately leads to irreversible lithium deposition and a significant shortening of the battery cycle life. In addition, the copper surface has a large contact angle with the electrolyte, which increases the adsorption and deposition barrier of lithium ions, causing polarization of the battery under high current.

[0004] In order to improve the above problems, researchers have coated a polymer on the surface of a copper current collector. For example, patent number CN114597421A discloses a negative electrode current collector for a lithium metal battery without a negative electrode, which includes a copper foil and a conductive polymer modification layer arranged on the surface of the copper foil, wherein the conductive polymer modification layer includes a binder and a conductive polymer. The conductive polymer includes any one or a combination of at least two of polypyrrole and / or polyaniline. Although this solution forms a uniform nucleation position on its surface, inhibits dendrite growth, and improves deposition uniformity. However, during the battery cycle, due to mechanical stress, volume change or electrochemical reaction, the polymer modification layer may gradually fall off or break, resulting in its functional failure and affecting the overall stability of the electrode. In addition, the polymer modification layer cannot increase the area of ​​the electrode conductive interface. Simply coating the polymer on the flat copper foil surface easily produces non-uniform lithium deposition under high current, thereby generating lithium dendrites. Summary of the Invention

[0005] In order to solve the problems of uneven lithium deposition at the current collector interface, poor wettability between the current collector and the electrolyte, and poor structural stability during battery cycling in existing lithium-free negative electrode batteries, the main purpose of the present invention is to provide a composite electrode material and a preparation method thereof, which uses a composite layer of a polymer layer and a conductive carbon layer as a current collector modification layer. The polymer layer can effectively improve the lithium affinity of the material and optimize the deposition behavior of lithium ions; the conductive carbon layer of large-particle porous carbon introduced between the polymer layer and the current collector can significantly improve the stability of the polymer layer, prevent the collapse of the polymer layer structure, improve the stability of the electrode structure, and at the same time increase the conductive area of ​​the electrode conductive interface, effectively improve the wettability of the electrolyte and reduce the surface current density of the battery, thereby enhancing the stability and cycle life of the battery.

[0006] In order to achieve the above-mentioned purpose, the present invention provides a composite electrode material, which includes an electrode current collector, a conductive carbon layer and a polymer layer, wherein the conductive carbon layer is located between the electrode current collector and the polymer layer, and the conductive carbon layer includes large-particle porous carbon with a particle size of not less than 50 μm.

[0007] Furthermore, the particle size of the large-particle porous carbon is 50-100 μm.

[0008] Furthermore, the polymer of the polymer layer is a polymer containing bifunctional groups of sulfonic acid group and cyano group.

[0009] Furthermore, the thickness of the conductive carbon layer is 70-150 μm.

[0010] Furthermore, the thickness of the polymer layer is 15-25 μm.

[0011] Another aspect of the present invention provides a method for preparing the aforementioned composite electrode material, comprising the following steps: mixing large-particle porous carbon, a binder, and a solvent to obtain a conductive carbon layer slurry; The conductive carbon layer slurry is applied to the surface of the electrode current collector, and then dried and rolled to obtain a conductive carbon layer / electrode current collector; The polymer solution is coated on the conductive carbon layer / the conductive carbon layer of the electrode current collector to obtain a composite electrode material.

[0012] Furthermore, the mass ratio of the large-particle porous carbon, the binder, and the solvent is 5:1:10-20.

[0013] Furthermore, the coating thickness of the conductive carbon layer slurry is 60-120 μm.

[0014] Furthermore, the drying process is carried out at a temperature of 60-100° C. and for a time of 6-24 hours.

[0015] Furthermore, the pressure of the roller pressing treatment is 4-8 MPa.

[0016] Furthermore, the large-particle porous carbon is prepared by carbonizing a carbon source.

[0017] Furthermore, the carbonization treatment is carried out under a protective atmosphere, the temperature of the carbonization treatment is 700-900° C., and the heating rate is 1-10° C. / min.

[0018] Furthermore, the mass fraction of the polymer in the polymer solution is 10% to 30%.

[0019] Compared with the prior art, the present invention has the following beneficial effects: (1) In the composite electrode material of the present invention, the conductive carbon layer of the large-particle porous carbon can significantly improve the wettability of the electrolyte and achieve a low curvature of the lithium ion transmission path, effectively avoiding the occurrence of polarization. At the same time, the high specific surface area of ​​the large-particle porous carbon helps to reduce the surface current density, thereby enhancing the stability of the battery and extending its service life.

[0020] 2. The polymer layer of the present invention can significantly improve the lithium affinity of large-particle porous carbon. At the same time, the present invention also specially designs the functional groups of the polymer layer. The introduction of polymers containing sulfonic acid and cyano bifunctional groups can further enhance the lithium affinity and film-forming properties of the polymer layer, and can optimize the composition of the solid electrolyte interface (SEI), thereby improving the overall performance of the battery.

[0021] 3. The electrode current collector of the present invention adopts a composite layer of a conductive carbon layer of large-particle porous carbon and a polymer layer as a modified layer. The two work together, and the polymer layer can completely fill and cover the surface of the large-particle porous carbon, significantly enhancing the structural stability of the existing modified layer, ensuring that the polymer layer is not prone to collapse during the cycle process, and further improving the cycle life of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The SEM characterization image of the surface of the electrode material of Comparative Example 1 of the present invention is shown; Figure 2 The SEM characterization image of the surface of the electrode material of Example 1 of the present invention is shown; Figure 3 A comparison chart of the cycle stability performance of the electrode materials of Example 1 of the present invention and Comparative Examples 1 to 3 is shown. DETAILED DESCRIPTION

[0023] It should be noted that, in the case of no conflict, the embodiments in this application and the features in the embodiments can be combined with each other. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope. The present invention will be described in detail below in conjunction with the embodiments.

[0024] In order to achieve the above-mentioned purpose, the first aspect of an embodiment of the present invention provides a composite electrode material, which includes an electrode current collector, a conductive carbon layer and a polymer layer, wherein the conductive carbon layer is located between the electrode current collector and the polymer layer, and the conductive carbon layer includes large-particle porous carbon with a particle size of not less than 50 μm.

[0025] The composite electrode material of the present invention adopts a composite layer of a polymer layer and a conductive carbon layer as a modified layer. The two layers cooperate with each other to improve the problems of uneven lithium deposition at the current collector interface and poor wettability between the current collector and the electrolyte, thereby enhancing the stability and cycle life of the battery.

[0026] The conductive carbon layer provided between the electrode current collector and the polymer layer effectively reduces the interfacial resistance between the current collector and the electrode material, and can significantly improve the conductivity and antioxidant properties of the current collector. The conductive carbon layer of the present invention is a large-particle porous carbon with a particle size of not less than 50 μm. Compared with the small-particle dense carbon layer, it can significantly improve the wettability of the electrolyte. At the same time, the construction of the large-particle porous carbon can achieve a low curvature of the lithium ion transmission path and avoid the occurrence of polarization. In addition, the high specific surface area of ​​the large-particle porous carbon helps to reduce the surface current density, improve the uniformity of lithium plating of the electrode under high current, inhibit the production of lithium dendrites, and can enhance the stability of the battery and extend its service life.

[0027] The polymer layer is set on the surface of the conductive carbon layer. The polymer layer can completely fill and cover the surface of the large-particle porous carbon, solving the problem that the existing pure polymer modified layer has weak direct contact with the current collector and the polymer layer structure is easy to fall off during the battery cycle, thereby ensuring that the performance of the polymer layer is effectively exerted, significantly improving the lithium affinity of the material, optimizing the deposition behavior of lithium ions, improving the uniformity of lithium deposition, and alleviating the volume expansion problem caused by lithium deposition.

[0028] In a preferred embodiment of the present invention, the particle size of the large-particle porous carbon is 50~100μm. For example, it can be 50μm, 55μm, 60μm, 65μm, 70μm, 75μm, 80μm, 85μm, 90μm, 95μm, 100μm. After a lot of research and experiments, the inventors of this application found that large-particle porous carbon with a particle size in this range can achieve optimal battery stability and cycle stability. If the particle size is too high, it will be difficult to evenly coat the conductive carbon layer, affecting the performance of the conductive carbon layer. If the particle size is too low, the effect of improving the interface resistance between the current collector and the electrode material is not obvious.

[0029] In a preferred embodiment of the present invention, the specific surface area of ​​the large-particle porous carbon is 500-1200 m 2 / g. For example, it can be 500m 2 / g、600m 2 / g、700m 2 / g、800m 2 / g、900m 2 / g、1000m 2 / g、1100m 2 / g、1200m 2 The large-particle porous carbon of the present invention has a high specific area, which helps to reduce the surface current density, improve the uniformity of lithium plating of the electrode under high current, inhibit the production of lithium dendrites, and thus enhance the stability of the battery and extend its service life.

[0030] In order to further improve the lithium affinity and film forming performance of the polymer layer, in a preferred embodiment of the present invention, the polymer of the polymer layer is a polymer containing a sulfonic acid group and a cyano group. The sulfonic acid group and the cyano group can coordinate and bond with lithium ions and have strong lithium affinity. The synergistic effect of the two can effectively capture Li + ions, ensuring their uniform distribution and deposition in the current collector, and optimizing the composition of the solid electrolyte interface (SEI), thereby improving the overall performance of the battery. In some preferred embodiments of the present invention, for example, the polymer includes but is not limited to sulfonated poly (arylene ether nitrile), acrylonitrile-sodium styrene sulfonate copolymer, and sulfonated polyacrylonitrile.

[0031] In some preferred embodiments of the present invention, the thickness of the conductive carbon layer is 70 to 150 μm. For example, it can be 70 μm, 80 μm, 90 μm, 100 μm, 110 μm, 120 μm, 130 μm, 140 μm, or 150 μm. More preferably, it is 100 to 120 μm. If the thickness of the conductive carbon layer is too low, it cannot accommodate lithium deposition; if it is too high, the coating is uneven and prone to cracking. The thickness of the polymer layer is 15 to 25 μm. If the thickness of the polymer layer is too low, it cannot evenly cover the conductive carbon layer; if it is too high, it hinders ion transmission.

[0032] In order to achieve the above object, a second aspect of an embodiment of the present invention provides a method for preparing the aforementioned composite electrode material, comprising the following steps: mixing large-particle porous carbon, a binder, and a solvent to obtain a conductive carbon layer slurry; The conductive carbon layer slurry is applied to the surface of the electrode current collector, and then dried and rolled to obtain a conductive carbon layer / electrode current collector; The polymer solution is coated on the conductive carbon layer / the conductive carbon layer of the electrode current collector to obtain a composite electrode material.

[0033] The present invention first coats the surface of the electrode current collector with a conductive carbon layer slurry, ensuring the formation of a complete porous conductive network on the surface of the electrode current collector. A polymer layer is then applied to fill the gaps, thus preserving the conductive network of the conductive carbon layer. If large porous carbon particles and polymer are mixed to form the coating, the polymer will isolate the porous carbon particles from contact and electron transport, resulting in an electronic disconnection between the surface layer and the underlying current collector.

[0034] In order to further improve the coating uniformity of the conductive carbon layer, in some preferred embodiments of the present invention, the mass ratio of the large-particle porous carbon to the solvent is 1:2~4, and the mass ratio of the large-particle porous carbon to the binder is 1:0.1~0.5.

[0035] Furthermore, the solvent may be selected from one or more of N-methylpyrrolidone (NMP), N,N-dimethylacetamide, or dimethyl sulfoxide. The binder may be selected from polyvinylidene fluoride (PVDF).

[0036] In a preferred embodiment of the present invention, the mass fraction of the polymer in the polymer solution is 10% to 30%, for example, 10%, 15%, 20%, 25%, or 30%.

[0037] To further improve the coating uniformity and structural stability of the conductive carbon layer, in some preferred embodiments of the present invention, the conductive carbon layer slurry has a coating thickness of 60-120 μm. The drying process is performed at a temperature of 60-100°C for 6-24 hours. The roller pressing process is performed at a pressure of 4-8 MPa. Rolling ensures that the large porous carbon particles are densely and evenly stacked, while the pressure should not be too high to prevent the coating from cracking.

[0038] In a preferred embodiment of the present invention, the large-particle porous carbon is prepared by carbonizing a carbon source. Furthermore, the carbon source is selected from one of carbon black, gluconate, carbonate or agarose. The carbonization treatment is carried out under a protective atmosphere, the temperature of the carbonization treatment is 700~900℃, and the heating rate is 1~10℃ / min. The protective atmosphere is a nitrogen atmosphere or an argon atmosphere. By precisely controlling the temperature and heating rate of the carbonization treatment, large-particle porous carbon with large particle size and high specific area can be formed after the carbonization of the carbon source.

[0039] In an optional embodiment of the present invention, large-particle porous carbon is produced by carbonizing carbon black. Specifically, carbon black powder and an amino polymer (such as polymelamine formaldehyde (PMF)) are stirred uniformly at room temperature to form a viscous black dispersion. The dispersion is then vacuum-dried at 70-90°C to obtain a dry powder. The dry powder is then calcined in a protective atmosphere. After calcination, the powder is cooled to obtain large-particle porous carbon. The amino polymer can be used to mix and connect the carbon black powder to form larger particles. The carbonization process releases ammonia gas, which further forms the porous carbon. The mass ratio of carbon black to PMF is 1:1-5, and the vacuum drying time is 12-36 hours. The calcination temperature is 800-950°C, the holding time is 5-15 hours, and the heating rate is 2-10°C / min.

[0040] In an optional embodiment of the present invention, large-particle porous carbon is prepared by carbonization treatment of gluconate, specifically: heating the gluconate under a protective atmosphere, grinding the heated sample into a powder and soaking it in hydrochloric acid, washing it with ultrapure water until it is neutral, and finally drying the washed product to obtain large-particle porous carbon. The heating temperature is 650~750℃, the holding time is 1~5h, and the heating rate is 5~10℃ / min. The soaking time is 12~48h. The drying time is 12~24h.

[0041] In an optional embodiment of the present invention, large-particle porous carbon is produced by carbonizing carbonate, specifically by drying and pulverizing carbonate and ion exchange resin to obtain a mixture, carbonizing the mixture at high temperature under a protective atmosphere, and then naturally cooling the carbonized product, pulverizing, washing, and drying the mixture to obtain large-particle porous carbon. The high-temperature carbonization temperature is 800-900°C, the holding time is 1-5 hours, and the heating rate is 1-5°C / min.

[0042] In an optional embodiment of the present invention, large-particle porous carbon is prepared by carbonizing agarose, specifically by: dissolving and mixing agarose with potassium oxalate or potassium chloride and ultrapure water to obtain a gel mixture; vacuum freeze-drying the gel mixture to obtain an aerogel; carbonizing the aerogel under a protective atmosphere, cooling to room temperature, washing the carbonized product, and vacuum drying to obtain large-particle porous carbon. The carbonization temperature is 800-900°C, the holding time is 2-5 hours, and the heating rate is 1-5°C / min.

[0043] The present application is further described in detail below with reference to specific embodiments. These embodiments should not be construed as limiting the scope of protection claimed in this application.

[0044] Example 1 A composite electrode material, comprising a copper foil, a conductive carbon layer and a polymer layer. The conductive carbon layer is located between the copper foil and the polymer layer (the polymer is sulfonated polyarylethernitrile). The thickness of the conductive carbon layer is 100 μm, the thickness of the polymer layer is 20 μm, and the particle size of the large-particle porous carbon in the conductive carbon layer is 50 μm, with a specific surface area of ​​600 m 2 / g. Its preparation method is as follows: (1) Preparation of sulfonated poly (arylene ether nitrile) Mixed bisphenol A (50 mmol), potassium hydroquinone monosulfonate (50 mmol), potassium carbonate (160 mmol) and 2,6-difluorobenzonitrile (105 mmol) were dissolved in a mixed solvent of N-methylpyrrolidone and toluene, heated to 120°C and maintained for 2 hours for dehydration, then heated to 145°C and maintained for 3 hours to promote oligomerization, and then gradually heated to 175°C, increasing by 10°C per hour and maintaining for 1 hour at each step to complete the polycondensation reaction to obtain a polycondensation product; the polycondensation product was precipitated in ethanol, the precipitate was ground into powder, and then impurities were removed by ethanol reflux and water washing three times. The purified product was dried in a vacuum oven at 80°C for 24 hours to obtain a sulfonated polyarylene ether nitrile.

[0045] (2) Synthesis of large-particle porous carbon 1g Ketjen Black 600J (carbon black) powder and 4g PMF (polymelamine formaldehyde) were uniformly mixed in a ratio of (1:4) at room temperature to form a viscous black dispersion, which was then vacuum dried at 80°C for 12 hours. The resulting dry powder was then calcined in an argon atmosphere (heating to 900°C at a rate of 10°C per minute) for 10 hours. After the powder cooled, large-particle porous carbon was obtained.

[0046] (3) Preparation of conductive carbon layer / electrode current collector The large-particle porous carbon, PVDF, and NMP obtained in the previous step were mixed in a mass ratio of 5:1:10 and stirred for 15 minutes to obtain a slurry; the slurry was coated on the surface of the copper foil with a thickness of 90 μm, and then dried in an oven at 80°C. After drying, it was rolled at a pressure of 4 MPa to obtain a conductive carbon layer / electrode current collector.

[0047] (4) Preparation of composite electrodes The sulfonated poly(arylene ether nitrile) obtained in step (1) was mixed with N,N-dimethylformamide (DMF) to obtain a polymer solution. The polymer solution was stirred at a constant temperature of 50°C for 12 hours, and then the solution was allowed to stand at room temperature for 6 hours to ensure that bubbles in the solution were completely eliminated. Finally, the polymer solution was evenly coated on the conductive carbon layer of the conductive carbon layer / electrode current collector to obtain a composite electrode. The mass fraction of the polymer solution was 20%.

[0048] Example 2 The only difference between this embodiment and embodiment 1 is that the rolling pressure in step (3) is 8 MPa.

[0049] Example 3 The only difference between this embodiment and embodiment 1 is that the mass fraction of the polymer solution in step (4) is 10%.

[0050] Example 4 The only difference between this embodiment and embodiment 1 is that in step (2), the synthesis process of large-particle porous carbon is carried out by using gluconate for carbonization. Specifically, 2 g of zinc gluconate is heated to 700°C at a heating rate of 8°C / min under a nitrogen atmosphere and kept warm for 2 hours. The carbonized sample is ground into powder and then soaked in hydrochloric acid for 24 hours. It is then washed with ultrapure water until neutral. Finally, the washed product is dried in an oven at 60°C to obtain large-particle porous carbon (particle size of 80 μm and specific area of ​​1000 m 2 / g).

[0051] Example 5 The only difference between this embodiment and embodiment 1 is that the synthesis process of large-particle porous carbon in step (2) is carried out by carbonization using carbonate. Specifically, the mixed powder of ion exchange resin and sodium carbonate is completely dried and crushed, and the mixed powder is placed in a pilot carbonization furnace for high-temperature carbonization under a nitrogen atmosphere. When the temperature is increased to 850°C at a heating rate of 5°C / min, the temperature is kept for 2 hours, and after natural cooling, the obtained block porous sample is crushed, and the crushed sample is placed in deionized water, fully stirred and washed at 60°C, and finally filtered with filter paper. The same process is repeated 8 to 10 times to fully remove the alkali until the pH value of the deionized water is 7, thereby obtaining large-particle porous carbon (particle size of 60 μm, specific area of ​​800 m 2 / g).

[0052] Example 6 The only difference between this embodiment and embodiment 1 is that in the synthesis process of large-particle porous carbon in step (2), agarose is used for carbonization in this embodiment, specifically: 0.18 g of agarose, an appropriate amount of potassium oxalate, and 4.3 ml of ultrapure water are mixed to obtain a mixture, the mixture is ultrasonicated for 1 minute to promote dissolution, and then heated in an oven to 115° C. and then heated for 15 minutes, the mixture is taken out, ultrasonicated again for 1 minute to fully mix the solution, and then naturally cooled to room temperature to form a gel mixture; The gel mixture was placed in a vacuum freeze dryer and dried for two days to obtain aerogel; the aerogel was then transferred to an alumina crucible, and the crucible was placed in a quartz tube and placed in a tube furnace. The sample was placed in a dynamic vacuum (about 10 - 3 The air on the surface of the material was removed in an atmosphere of 400 Torr for 1 hour, and then the temperature was raised at a rate of 2°C / min under Ar (100 sccm gas flow rate) according to a preset program, and the maximum temperature (850°C) was maintained for 3 hours to obtain carbonized powder. After the carbonized powder is cooled to room temperature, it is placed in a Buchner funnel, and a layer of polytetrafluoroethylene microporous filter membrane is placed under the front funnel. Then, a suction filtration bottle is connected and washed with hot ultrapure water (80°C) until the filtrate is neutral. The washed powder is then dried in a vacuum oven at 110°C for 12 hours to obtain large-particle porous carbon (particle size of 80 μm, specific area of ​​550 m 2 / g).

[0053] Example 7 The only difference between this embodiment and embodiment 1 is that the thickness of the conductive carbon layer is 80 μm and the thickness of the polymer layer is 25 μm.

[0054] Example 8 The only difference between this embodiment and embodiment 1 is that the thickness of the conductive carbon layer is 150 μm and the thickness of the polymer layer is 15 μm.

[0055] Comparative Example 1 An electrode material, which differs from Example 1 only in that it does not contain a polymer layer, that is, after preparing the conductive carbon layer / electrode current collector, the coating of the polymer layer in step (4) is not performed.

[0056] Comparative Example 2 An electrode material, which differs from Example 1 only in that it does not contain a conductive carbon layer, is obtained by directly coating the polymer solution of Example 1 on the surface of a copper foil.

[0057] Comparative Example 3 An electrode material, which is different from Example 1 only in the material of the conductive carbon layer. The material of the conductive carbon layer in this comparative example is carbon black material (the carbon black is ECP600), and the particle size of the carbon black is 30 μm.

[0058] Morphology characterization: The electrode material prepared in Comparative Example 1 was subjected to SEM characterization, and its morphology is as follows Figure 1 As shown in FIG. 1 , it can be seen that the surface morphology of the electrode without the polymer layer mainly presents a porous structure of large carbon particles. The electrode material prepared in Example 1 was characterized by SEM, and its morphology is as follows: Figure 2 As shown, it can be seen that the polymer layer completely fills and covers the porous carbon surface, forming a uniform and flat structure.

[0059] Cyclic stability test: The cycling stability of the electrode materials of the above examples and comparative examples was compared, and the test results are shown in Table 1. The cycling stability performance comparison of comparative examples 1 to 3 and example 1 is shown in the figure below. Figure 3 As shown, the test method is: using an asymmetric cell, lithium metal as the counter electrode, and 1 mA / cm 2 The current density of lithium plating is 1h, and the amount of lithium plating is 1mAh / cm 2 , and then strip lithium at the same current density until the voltage rises to a relative voltage of 1V between the two electrodes. Coulomb efficiency = (lithium stripping amount / lithium plating amount) × 100%.

[0060] Table 1

[0061] As can be seen from Table 1, the initial coulombic efficiency and average coulombic efficiency of the composite electrode material of Example 1 are the best compared to those of the other examples and comparative examples. This is because Example 1 uses a polymer layer and a conductive carbon layer with the most suitable parameters to modify the current collector electrode. The two work together to improve the uneven lithium deposition at the current collector interface and the poor wettability of the current collector and the electrolyte, thereby enhancing the stability and cycle life of the battery. Other examples change parameters such as coating thickness, particle size, and specific surface area within the scope of protection of the present invention. Their initial coulombic efficiency is approximately in the range of 94%-97%, and the average coulombic efficiency is approximately in the range of 97%-99%, all of which have better cycle performance. Example 4 uses larger particles and a larger specific surface area than Example 1, resulting in an initial coulombic efficiency of less than 95% and an average coulombic efficiency of less than 99%, indicating that the particles and specific surface area should not be too large. The polymer layer thickness of Example 7 uses a thicker polymer layer than Example 1. The high thickness affects ion transport, resulting in a decrease in coulombic efficiency.

[0062] The 100-time average coulombic efficiency data for Comparative Examples 1 and 2 show significant decreases compared to the examples, indicating that the carbon coating and polymer coating alone are not ideal. Comparative Example 3 uses smaller carbon particles. Although the carbon coating and polymer coating design are adopted, the small carbon particle size leads to uneven lithium deposition, which does not significantly improve the interface resistance between the current collector and the electrode material, resulting in poor performance.

[0063] The embodiments described above are merely illustrative of embodiments of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the present invention. The present invention may also be implemented in other specific ways or in other specific forms without departing from the gist or essential features of the present invention. Therefore, the embodiments described should be considered in all respects as illustrative and not restrictive. The scope of the present invention should be described by the appended claims, and any variations equivalent to the intent and scope of the claims should also be included within the scope of the present invention.

Claims

1. A composite electrode material, characterized in that The composite electrode material comprises an electrode current collector, a conductive carbon layer and a polymer layer. The conductive carbon layer is located between the electrode current collector and the polymer layer. The conductive carbon layer comprises large-particle porous carbon with a particle size of not less than 50 μm.

2. The composite electrode material according to claim 1, characterized in that The particle size of the large-particle porous carbon is 50-100 μm.

3. The composite electrode material according to claim 1, characterized in that The polymer of the polymer layer is a polymer containing a sulfonic acid group and a cyano group.

4. The composite electrode material according to claim 1, characterized in that The thickness of the conductive carbon layer is 70-150 μm; And / or, the thickness of the polymer layer is 15-25 μm.

5. A method for preparing a composite electrode material according to any one of claims 1 to 4, characterized in that: The following steps are involved: mixing large-particle porous carbon, a binder, and a solvent to obtain a conductive carbon layer slurry; The conductive carbon layer slurry is applied to the surface of the electrode current collector, and then dried and rolled to obtain a conductive carbon layer / electrode current collector; The polymer solution is coated on the conductive carbon layer / the conductive carbon layer of the electrode current collector to obtain a composite electrode material.

6. The method for preparing a composite electrode material according to claim 5, characterized in that: The mass ratio of the large-particle porous carbon to the solvent is 1:2-4; and / or, the coating thickness of the conductive carbon layer slurry is 100-200 μm; And / or, the drying process is performed at a temperature of 60-100° C. for a time of 6-24 hours; And / or, the pressure of the roller pressing treatment is 4-8 MPa.

7. The method for preparing a composite electrode material according to claim 5, characterized in that: The large-particle porous carbon is prepared by carbonizing a carbon source.

8. The method for preparing a composite electrode material according to claim 7, wherein: The carbon source is selected from one of carbon black, gluconate, carbonate or agarose.

9. The method for preparing a composite electrode material according to claim 7, wherein: The carbonization treatment is carried out under a protective atmosphere, the temperature of the carbonization treatment is 700-900° C., and the heating rate is 1-10° C. / min.

10. The method for preparing a composite electrode material according to claim 5, characterized in that: The mass fraction of the polymer in the polymer solution is 10% to 30%.

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