Composite electrode material and method for producing the same

Abstract

The application discloses a kind of composite electrode material and preparation method thereof, which belong to lithium-free negative electrode battery technical field.The composite electrode material of the application includes electrode current collector, conductive carbon layer and polymer layer, 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 particle size not less than 50 μm.The composite layer of polymer layer and conductive carbon layer is used as the modification layer of current collector, the polymer layer can effectively improve the lithium affinity of material, and optimize the deposition behavior of lithium ion;The conductive carbon layer of large particle porous carbon introduced between polymer layer and current collector can significantly improve the stability of polymer layer to prevent the structure collapse of polymer layer, improve the stability of electrode structure, and also can improve the conductive area of electrode conductive interface, effectively improve the wetting performance of electrolyte and reduce the surface current density of battery, and then enhance the stability and cycle life of battery.

Description

Technical Field

[0001] This invention belongs to the field of lithium-free anode battery technology, and specifically relates to a composite electrode material and its preparation method. Background Technology

[0002] Lithium-free anode batteries are a novel lithium battery technology that significantly reduces the lithium content in the battery system, greatly improving safety. Lithium-free anode batteries do not have a separate lithium anode; all active lithium is initially stored within the cathode material. During charging, active lithium is released from the cathode material and directly electroplated onto the current collector of the anode in situ. During discharging, the lithium on the anode is stripped and converted into lithium ions, which migrate from the anode to the cathode, returning to the cathode material structure, restoring the state of lithium-free anode and lithium-stored cathode, completing one cycle.

[0003] Copper is widely used as a current collector on the anode side of batteries due to its excellent electrical conductivity, good ductility, and stability at low potentials. However, commercially available copper current collectors suffer from microcracks and pitting defects at the micro- and nano-scale. These defects lead to uneven lithium deposition, resulting in uneven local current density distribution, increasing the battery's internal resistance, and ultimately causing irreversible lithium deposition and a significant reduction in battery cycle life. Furthermore, the large contact angle between the copper surface and the electrolyte increases the adsorption and deposition barriers for lithium ions, causing polarization of the battery under high current.

[0004] To address the aforementioned issues, researchers have employed polymer coating on the surface of copper current collectors. For example, patent CN114597421A discloses a negative electrode current collector for a lithium metal battery without a negative electrode, comprising a copper foil and a conductive polymer modification layer disposed on the surface of the copper foil. 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. While this approach creates uniform nucleation sites on the surface, suppressing dendrite growth and improving deposition uniformity, the polymer modification layer may gradually detach or break during battery cycling due to mechanical stress, volume changes, or electrochemical reactions, leading to functional failure and affecting the overall stability of the electrode. Furthermore, this polymer modification layer does not increase the area of ​​the conductive interface of the electrode; simply applying the polymer to a flat copper foil surface easily results in non-uniform lithium deposition under high current, leading to lithium dendrite formation. Summary of the Invention

[0005] To address the problems of uneven lithium deposition at the current collector interface, poor wettability between the current collector and electrolyte, and poor structural stability during battery cycling in existing lithium-free anode batteries, the main objective of this invention is to provide a composite electrode material and its preparation method. This material employs a composite layer of polymer and conductive carbon as a current collector modification layer. The polymer layer effectively improves the material's lithium affinity and optimizes lithium-ion deposition behavior. The conductive carbon layer, consisting of large-particle porous carbon introduced between the polymer layer and the current collector, significantly enhances the stability of the polymer layer, preventing structural collapse and improving electrode structural stability. Simultaneously, it increases the conductive area of ​​the electrode's conductive interface, effectively improving the electrolyte's wettability and reducing the battery's surface current density, thereby enhancing battery stability and cycle life.

[0006] To achieve the above objectives, the present invention provides a composite electrode material comprising 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 comprises large porous carbon particles with a particle size of not less than 50 μm.

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

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

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

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

[0011] In another aspect, the present invention provides a method for preparing the aforementioned composite electrode material, comprising the following steps:

[0012] Large-particle porous carbon, binder and solvent are mixed to obtain conductive carbon layer slurry;

[0013] The conductive carbon layer slurry is coated onto the surface of the electrode current collector, and then dried and rolled to obtain the conductive carbon layer / electrode current collector.

[0014] A polymer solution is coated onto the conductive carbon layer of the conductive carbon layer / electrode current collector to obtain a composite electrode material.

[0015] Furthermore, the mass ratio of large-particle porous carbon, binder, and solvent is 5:1:10~20.

[0016] Furthermore, the coating thickness of the conductive carbon layer slurry is 60~120μm.

[0017] Furthermore, the drying process is carried out at a temperature of 60~100℃ for a time of 6~24h.

[0018] Furthermore, the pressure of the rolling process is 4~8 MPa.

[0019] Furthermore, the large-particle porous carbon is obtained by carbonization treatment of a carbon source.

[0020] Furthermore, the carbonization process is carried out under a protective atmosphere, and the temperature of the carbonization process is 700~900℃, with a heating rate of 1~10℃ / min.

[0021] Furthermore, the polymer solution contains a polymer mass fraction of 10% to 30%.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] (1) In the composite electrode material of the present invention, the conductive carbon layer of large-particle porous carbon can significantly improve the wettability of the electrolyte and achieve a low curvature of the lithium-ion transport path, effectively avoiding the generation of polarization. At the same time, the high specific surface area of ​​large-particle porous carbon helps to reduce the surface current density, thereby enhancing the stability of the battery and extending its service life.

[0024] 2. The polymer layer of the present invention can significantly improve the lithiophilicity of large porous carbon particles. At the same time, the present invention also specially designs functional groups in the polymer layer. The introduction of polymers containing sulfonic acid and cyano bifunctional groups can further enhance the lithiophilic performance and film-forming performance of the polymer layer, and optimize the composition of the solid electrolyte interface (SEI), thereby improving the overall performance of the battery.

[0025] 3. The electrode current collector of the present invention uses a composite layer of conductive carbon layer with large-particle porous carbon and polymer layer as a modification layer. The two work together, and the polymer layer can completely fill and cover the surface of large-particle porous carbon, which significantly enhances the structural stability of the existing modification layer and ensures that the polymer layer is not easy to collapse during cycling, thereby further improving the cycle life of the battery. Attached Figure Description

[0026] Figure 1 The SEM characterization image of the electrode material surface of Comparative Example 1 of the present invention is shown.

[0027] Figure 2 The SEM characterization image of the electrode material surface of Embodiment 1 of the present invention is shown;

[0028] Figure 3 The diagram shows a comparison of the cycle stability of the electrode materials of Embodiment 1 and Comparative Examples 1-3 of the present invention. Detailed Implementation

[0029] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. Furthermore, regarding the numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included within this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range. The invention will now be described in detail with reference to embodiments.

[0030] To achieve the above objectives, a first aspect of the present invention provides a composite electrode material comprising 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 comprises large porous carbon particles with a particle size of not less than 50 μm.

[0031] The composite electrode material of this invention uses a composite layer of polymer layer and conductive carbon layer as a modification layer. The two layers work together to improve the uneven lithium deposition at the current collector interface and the poor wettability between the current collector and the electrolyte, thereby enhancing the stability and cycle life of the battery.

[0032] A conductive carbon layer disposed between the electrode current collector and the polymer layer effectively reduces the interfacial resistance between the current collector and the electrode material, significantly improving the conductivity and oxidation resistance of the current collector. The conductive carbon layer of this invention consists of large-particle porous carbon with a particle size of at least 50 μm. Compared to small-particle dense carbon layers, this significantly improves electrolyte wettability. Furthermore, the construction of large-particle porous carbon enables a low curvature of the lithium-ion transport path, preventing polarization. In addition, the high specific surface area of ​​the large-particle porous carbon helps reduce the surface current density, improves the uniformity of lithium plating under high current, suppresses lithium dendrite formation, and enhances battery stability and extends its lifespan.

[0033] A polymer layer is set on the surface of the conductive carbon layer. The polymer layer can completely fill and cover the surface of large porous carbon particles, which solves the problem that the existing pure polymer modified layer has weak bonding force with the current collector and the polymer layer structure is easy to fall off during battery cycling. This ensures that the performance of the polymer layer can be effectively exerted, significantly improves the lithium affinity of the material, optimizes the lithium ion deposition behavior, improves the uniformity of lithium deposition, and alleviates the volume expansion problem caused by lithium deposition.

[0034] In a preferred embodiment of the present invention, the particle size of the large porous carbon particles is 50-100 μm. For example, it can be 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, 75 μm, 80 μm, 85 μm, 90 μm, 95 μm, or 100 μm. Through extensive research and experimentation, the inventors of this application have found that large porous carbon particles within this particle size range can achieve optimal battery stability and cycle stability. If the particle size is too high, it is difficult to uniformly 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 interfacial resistance between the current collector and the electrode material is not significant.

[0035] In a preferred embodiment of the present invention, the specific surface area of ​​the large-particle porous carbon is 500~1200 m². 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 / g. 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 on the electrode under high current, suppress lithium dendrite formation, and thus enhance the stability of the battery and extend its service life.

[0036] To further improve the lithiophilic and film-forming properties of the polymer layer, in a preferred embodiment of the present invention, the polymer of the polymer layer is a polymer containing sulfonic acid and cyano bifunctional groups. These sulfonic acid and cyano bifunctional groups can coordinate and bond with lithium ions, exhibiting strong lithiophilic properties. Their synergistic effect can effectively capture Li- ions. + Ions are incorporated to ensure their uniform distribution and deposition in the current collector and to optimize the composition of the solid electrolyte interface (SEI), thereby improving the overall performance of the battery. In some preferred embodiments of the present invention, polymers include, but are not limited to, sulfonated polyarylene ether nitrile, acrylonitrile-sodium styrene sulfonate copolymer, and sulfonated polyacrylonitrile.

[0037] In some preferred embodiments of the present invention, the thickness of the conductive carbon layer is 70-150 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 100-120 μm. If the thickness of the conductive carbon layer is too low, it cannot accommodate lithium deposition; if it is too high, the coating will be uneven and prone to cracking. The thickness of the polymer layer is 15-25 μm. If the thickness of the polymer layer is too low, it cannot uniformly cover the conductive carbon layer; if it is too high, it hinders ion transport.

[0038] To achieve the above objectives, a second aspect of the present invention provides a method for preparing the aforementioned composite electrode material, comprising the following steps:

[0039] Large-particle porous carbon, binder and solvent are mixed to obtain conductive carbon layer slurry;

[0040] The conductive carbon layer slurry is coated onto the surface of the electrode current collector, and then dried and rolled to obtain the conductive carbon layer / electrode current collector.

[0041] A polymer solution is coated onto the conductive carbon layer of the conductive carbon layer / electrode current collector to obtain a composite electrode material.

[0042] This invention first coats the surface of the electrode current collector with a conductive carbon slurry, ensuring the formation of a complete porous conductive network on the surface of the current collector. Then, a polymer layer is applied to fill the gaps, thus not damaging the conductive network of the conductive carbon layer. If large-particle porous carbon and polymer are mixed to form a coating, the polymer will isolate the contact and electron transport between the porous carbon particles, causing an electronic break between the surface layer and the underlying current collector.

[0043] To further improve the coating uniformity of the conductive carbon layer, in some preferred embodiments of the present invention, the mass ratio of large-particle porous carbon to solvent is 1:2~4, and the mass ratio of large-particle porous carbon to binder is 1:0.1~0.5.

[0044] Furthermore, the solvent may be selected from one or more of N-methylpyrrolidone (NMP), N,N-dimethylacetamide, or dimethyl sulfoxide. The adhesive may be selected from polyvinylidene fluoride (PVDF).

[0045] In a preferred embodiment of the present invention, the polymer solution contains 10% to 30% by mass. For example, it can be 10%, 15%, 20%, 25%, or 30%.

[0046] To further improve the coating uniformity and structural stability of the conductive carbon layer, in some preferred embodiments of the present invention, the coating thickness of the conductive carbon slurry is 60~120μm. The drying temperature is 60~100℃, and the time is 6~24h. The rolling pressure is 4~8MPa. Rolling ensures that the large porous carbon particles are tightly and uniformly stacked, and the pressure should not be too high to prevent the coating from cracking.

[0047] In a preferred embodiment of the present invention, the large-particle porous carbon is obtained by carbonization treatment of a carbon source. Further, the carbon source is selected from carbon black, gluconate, carbonate, or agarose. The carbonization treatment is carried out under a protective atmosphere, at a temperature of 700-900°C, and at a heating rate of 1-10°C / min. The protective atmosphere is a nitrogen atmosphere or an argon atmosphere. By precisely controlling the temperature and heating rate of the carbonization treatment, the carbon source can be carbonized to form large-particle porous carbon with a large particle size and high specific surface area.

[0048] In an optional embodiment of the present invention, the large-particle porous carbon is obtained by carbon black through carbonization treatment. Specifically, carbon black powder is stirred with an amino polymer (such as polymelamine formaldehyde (PMF)) at room temperature to form a viscous black dispersion, which is then vacuum dried at 70-90°C to obtain a dried powder. The dried powder is then calcined in a protective atmosphere. After calcination, the powder is cooled to obtain large-particle porous carbon. The use of an amino polymer allows the carbon black powder to be mixed and linked to form larger particles. The carbonization process releases ammonia gas, thereby forming 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.

[0049] In an optional embodiment of the present invention, large-particle porous carbon is obtained by carbonization treatment of gluconate. Specifically, the gluconate is heated under a protective atmosphere, the heated sample is then ground into powder and soaked in hydrochloric acid. After soaking, it is washed with ultrapure water until neutral, and finally the washed product is dried 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.

[0050] In an optional embodiment of the present invention, the large-particle porous carbon is obtained by carbonization of carbonate. Specifically, the carbonate and ion exchange resin are dried and pulverized to obtain a mixture. The mixture is then carbonized at high temperature under a protective atmosphere. After natural cooling, the carbonized product is pulverized, washed, and dried 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.

[0051] In an optional embodiment of the present invention, the large-particle porous carbon is obtained by carbonization of agarose, specifically: agarose is dissolved and mixed with potassium oxalate or potassium chloride and ultrapure water to obtain a gel mixture; the gel mixture is then freeze-dried under vacuum to obtain an aerogel; the aerogel is carbonized under a protective atmosphere, and after cooling to room temperature, the carbonized product is washed and vacuum-dried to obtain the large-particle porous carbon. The carbonization temperature is 800~900℃, the holding time is 2~5h, and the heating rate is 1~5℃ / min.

[0052] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0053] Example 1

[0054] A composite electrode material includes 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 polyarylene ether nitrile). The thickness of the conductive carbon layer is 100 μm, and the thickness of the polymer layer is 20 μm. The large porous carbon particles in the conductive carbon layer have a particle size of 50 μm and a specific surface area of ​​600 m². 2 / g. Its preparation method is as follows:

[0055] (1) Preparation of sulfonated polyarylene ether nitrile

[0056] A mixture of bisphenol A (50 mmol), potassium hydroquinone monosulfonate (50 mmol), potassium carbonate (160 mmol), and 2,6-difluorobenzonitrile (105 mmol) was dissolved in a mixed solvent of N-methylpyrrolidone and toluene. The solution was heated to 120 °C and held for 2 h for dehydration, then heated to 145 °C and held for 3 h to promote oligomerization. The solution was then gradually heated to 175 °C at a rate of 10 °C per hour, and held for 1 hour at each step to complete the polycondensation reaction, yielding the polycondensation product. The polycondensation product was precipitated in ethanol, and the precipitate was ground into powder. Impurities were removed by reflux of ethanol and washing with water three times. The purified product was dried in a vacuum oven at 80 °C for 24 h to obtain sulfonated polyarylene ether nitrile.

[0057] (2) Synthesis of large-particle porous carbon

[0058] 1g of Ketjen Black 600J (carbon black) powder and 4g of PMF (polymelamine formaldehyde) were mixed uniformly at room temperature (1:4) to form a viscous black dispersion. The mixture was then vacuum dried at 80°C for 12 hours. The dried powder was then calcined in an argon atmosphere (heated to 900°C at a rate of 10°C per minute) for 10 hours. After cooling, large-particle porous carbon was obtained.

[0059] (3) Preparation of conductive carbon layer / electrode current collector

[0060] The large-particle porous carbon, PVDF, and NMP obtained in the previous step are mixed at a mass ratio of 5:1:10 and stirred for 15 minutes to obtain a slurry. The slurry is coated on the surface of a copper foil with a thickness of 90 μm, and then dried in an oven at 80°C. After drying, it is rolled at a pressure of 4 MPa to obtain a conductive carbon layer / electrode current collector.

[0061] (4) Preparation of composite electrodes

[0062] The sulfonated polyarylene 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 allowed to stand at room temperature for 6 hours to ensure that the air bubbles in the solution were completely eliminated. Finally, the polymer solution was uniformly coated on the conductive carbon layer / electrode current collector conductive carbon layer to obtain a composite electrode. The mass fraction of the polymer solution was 20%.

[0063] Example 2

[0064] The only difference between this embodiment and embodiment 1 is that the roller pressure in step (3) is 8 MPa.

[0065] Example 3

[0066] The only difference between this embodiment and Example 1 is that the mass fraction of the polymer solution in step (4) is 10%.

[0067] Example 4

[0068] The only difference between this embodiment and Example 1 is that in step (2), the synthesis process of the large-particle porous carbon is carried out using gluconate. Specifically, 2g of zinc gluconate is heated to 700°C at a heating rate of 8°C / min under a nitrogen atmosphere and held for 2 hours. The carbonized sample is then ground into powder and soaked in hydrochloric acid for 24 hours. After washing with ultrapure water until neutral, the washed product is dried in a 60°C oven to obtain large-particle porous carbon (particle size of 80μm and specific area of ​​1000m²). 2 / g).

[0069] Example 5

[0070] The only difference between this embodiment and Embodiment 1 is the synthesis process of the large-particle porous carbon in step (2). In this embodiment, carbonate is used for carbonization. Specifically, the ion exchange resin and sodium carbonate are completely dried and pulverized into a mixed powder. The mixed powder is placed in a pilot carbonization furnace and carbonized at high temperature under a nitrogen atmosphere. The temperature is increased to 850°C at a heating rate of 5°C / min, and held for 2 hours. After natural cooling, the resulting blocky porous sample is pulverized. The pulverized sample is placed in deionized water, stirred thoroughly, and washed at 60°C. Finally, it is 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, thus obtaining large-particle porous carbon (particle size of 60 μm and specific area of ​​800 m²). 2 / g).

[0071] Example 6

[0072] The only difference between this embodiment and embodiment 1 is that in the synthesis process of large porous carbon in step (2), agarose is used for carbonization in this embodiment. Specifically, 0.18g of agarose, an appropriate amount of potassium oxalate, and 4.3ml of ultrapure water are mixed to obtain a mixture. The mixture is sonicated for 1min to promote dissolution. Then, it is heated to 115°C in an oven for 15min. After that, the mixture is taken out and sonicated again for 1min to make the solution fully mixed and uniform. After naturally cooling to room temperature, a gel mixture is formed.

[0073] The gel mixture was placed in a vacuum freeze dryer and dried for two days to obtain an aerogel. The aerogel was then transferred to an alumina crucible, which was then placed in a quartz tube and placed in a tube furnace. The sample was then placed under a dynamic vacuum (approximately 10 °C). - 3 The air on the material surface was removed by 1 hour in Torr, and then under Ar (100 sccm gas flow rate), the temperature was increased at a rate of 2℃ / min according to the preset program, and held at the highest temperature (850℃) for 3 hours to obtain carbonized powder.

[0074] After cooling the carbonized powder to room temperature, it was placed in a Buchner funnel. A layer of polytetrafluoroethylene microporous filter membrane was placed under the funnel, and a suction flask was connected. The powder was washed with hot ultrapure water (80°C) until the filtrate was neutral. The washed powder was then dried in a vacuum oven at 110°C for 12 hours to obtain large-particle porous carbon (particle size 80 μm, specific area 550 m²). 2 / g).

[0075] Example 7

[0076] 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.

[0077] Example 8

[0078] 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.

[0079] Comparative Example 1

[0080] An electrode material 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 polymer layer coating in step (4) is not performed.

[0081] Comparative Example 2

[0082] An electrode material, which differs from Example 1 only in that it does not contain a conductive carbon layer, that is, the polymer solution of Example 1 is directly coated onto the surface of copper foil.

[0083] Comparative Example 3

[0084] An electrode material differs from Example 1 only in the material of the conductive carbon layer. The conductive carbon layer in this comparative example is made of carbon black (ECP600) with a particle size of 30 μm.

[0085] Morphology characterization: The electrode material prepared in Comparative Example 1 was characterized by SEM, and its morphology is as follows. Figure 1 As shown, the electrode surface without the polymer layer mainly exhibits a porous structure of large carbon particles. The electrode material prepared in Example 1 was characterized by SEM, and its morphology is shown below. Figure 2 As shown, the polymer layer completely fills and covers the porous carbon surface, forming a uniform and flat structure.

[0086] Cyclic stability testing: The cyclic stability of the electrode materials in the above examples and comparative examples was compared, and the test results are shown in Table 1. A comparison graph of the cyclic stability performance of Comparative Examples 1-3 and Example 1 is shown below. Figure 3 As shown, the test method is as follows: using an asymmetric battery, with lithium metal as the counter electrode, and applying 1 mA / cm to the working electrode. 2 Lithium plating at a current density of 1 hour yielded a lithium plating amount of 1 mAh / cm³. 2 Then, lithium is stripped at the same current density until the voltage rises to a relative voltage of 1V between the two electrodes. Coulombic efficiency = (lithium stripping amount / lithium plating amount) × 100%.

[0087] Table 1

[0088]

[0089] As shown in Table 1, Example 1 exhibits the best initial and average coulombic efficiencies compared to the composite electrode materials in other examples and comparative examples. This is because Example 1 uses polymer and conductive carbon layers with optimal parameters to modify the current collector electrode. The two layers work together to improve the uneven lithium deposition at the current collector interface and the poor wettability between the current collector and the electrolyte, thus enhancing battery stability and cycle life. Other examples, within the scope of this invention, modify parameters such as coating thickness, particle size, and specific surface area, achieving initial coulombic efficiencies of approximately 94%-97% and average coulombic efficiencies of approximately 97%-99%, all demonstrating superior cycle performance. Example 4, compared to Example 1, uses larger particles and a larger specific surface area, resulting in an initial coulombic efficiency below 95% and an average coulombic efficiency below 99%, indicating that particle size and specific surface area should not be too large. Example 7 uses a thicker polymer layer than Example 1; the increased thickness affects ion transport, leading to a decrease in coulombic efficiency.

[0090] The average coulombic efficiency data of Comparative Examples 1 and 2 after 100 cycles showed a significant decrease compared to the examples, indicating that the carbon coating and polymer coating alone were not ideal. Comparative Example 3 used carbon particles with smaller diameters. Although it employed a design combining carbon and polymer coatings, the small particle size resulted in uneven lithium deposition and insufficient improvement in the interfacial resistance between the current collector and the electrode material, leading to poor performance.

[0091] The embodiments described above are merely illustrative of implementation methods of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. The present invention can also be implemented in other specific ways or forms without departing from its spirit or essential characteristics. Therefore, the described embodiments should be considered illustrative rather than limiting in any respect. The scope of the present invention should be defined 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 for a lithium-free anode battery, characterized in that, The composite electrode material includes 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 includes large porous carbon particles with a particle size of not less than 50 μm. The polymer in the polymer layer is a polymer containing bifunctional groups of sulfonic acid and cyano groups.

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

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

4. A method for preparing a composite electrode material as described in any one of claims 1 to 3, characterized in that, Includes the following steps: Large-particle porous carbon, binder and solvent are mixed to obtain conductive carbon layer slurry; The conductive carbon layer slurry is coated onto the surface of the electrode current collector, and then dried and rolled to obtain the conductive carbon layer / electrode current collector. A polymer solution is coated onto the conductive carbon layer of the conductive carbon layer / electrode current collector to obtain a composite electrode material.

5. The method for preparing the composite electrode material according to claim 4, characterized in that, The mass ratio of the large porous carbon particles to the solvent is 1:2~4; And / or, the coating thickness of the conductive carbon layer slurry is 100~200μm; And / or, the drying process is carried out at a temperature of 60~100℃ for a time of 6~24h; And / or, the pressure of the rolling process is 4~8MPa.

6. The method for preparing the composite electrode material according to claim 4, characterized in that, The large-particle porous carbon is obtained by carbonization treatment of a carbon source.

7. The method for preparing the composite electrode material according to claim 6, characterized in that, The carbon source is selected from one of carbon black, gluconate, carbonate or agarose.

8. The method for preparing the composite electrode material according to claim 6, characterized in that, The carbonization process is carried out under a protective atmosphere, and the temperature of the carbonization process is 700~900℃, with a heating rate of 1~10℃ / min.

9. The method for preparing the composite electrode material according to claim 4, characterized in that, The polymer solution contains 10% to 30% polymer by mass.

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