Composite positive electrode material and preparation method and application thereof

Abstract

This invention relates to the field of solid-state battery technology, and particularly to a composite cathode material, its preparation method, and its application. The composite cathode material provided by this invention, by mass fraction, comprises 97wt%-99% active material and 1wt%-3wt% binder; the active material includes a cathode active material, a solid electrolyte material, and a conductive agent; the mass fraction of the cathode active material in the active material is 60wt%-70wt%; the mass fraction of the solid electrolyte material in the active material is 28wt%-30wt%; the solid electrolyte is selected from chloride-based solid electrolytes. The composite cathode material provided by this invention, by selecting a chloride-based solid electrolyte with high ionic conductivity as a component of the active material and optimizing the proportion of the active material, enables lithium-ion solid-state batteries containing this composite cathode material to exhibit high capacity and cycle stability under low stacking pressure and high current density.

Description

Technical Field

[0001] This invention relates to the field of solid-state battery technology, and in particular to a composite cathode material, its preparation method, and its application. Background Technology

[0002] With the continuous development of new energy technologies, the demand for energy storage batteries that improve safety, reduce costs, increase energy density, and extend cycle life has become increasingly apparent. Solid-state batteries, due to their high energy density and safety, are considered the core of next-generation energy storage technology.

[0003] The core of solid-state batteries lies in replacing the liquid electrolyte and separator in traditional liquid batteries with a solid electrolyte. This structural change aims to improve battery safety and energy density. Solid-state batteries achieve the storage and release of electrochemical energy through the transport of lithium ions via the solid electrolyte between the positive and negative electrodes. However, the contact problem at the solid-solid interface in solid-state batteries, especially the interface stability within the composite cathode, is a key challenge limiting their performance. To address this issue, current research focuses on optimizing the electrode-electrolyte interface design, enhancing interfacial bonding and ionic conductivity through material composites, surface modification, or the introduction of flexible interface layers, thereby promoting the practical application of solid-state battery technology.

[0004] In existing technologies, to obtain high cathode capacity, extremely high stacking pressures (typically exceeding 250 MPa) are usually required to maintain interparticle contact, severely limiting the practical applications of solid-state batteries. When solid-state batteries operate at lower stacking pressures (e.g., 2 MPa-10 MPa) and higher current densities (e.g., 1 mA / cm²) closer to practical applications… 2 When working under certain conditions, the performance of the composite cathode will decrease significantly, mainly manifested as follows: (1) Ion transport is limited, which restricts the capacity of the cathode material at high rates; (2) The cathode material undergoes volume change during charging and discharging. Without high external pressure to maintain contact, this volume change is very likely to cause the cathode material and solid electrolyte particles to lose contact, forming pores, which in turn increases the internal resistance of the battery and causes rapid capacity decay, thereby reducing the capacity and cycle life of the solid battery.

[0005] Therefore, how to achieve high capacity and long cycle life of solid-state battery composite cathodes under low stacking pressure and high current density is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] This invention provides a composite cathode material, its preparation method, and its application to solve the problems of low capacity and poor cycle stability of solid-state batteries under low stacking pressure in the prior art.

[0007] In a first aspect, the present invention provides a composite cathode material, comprising, by mass fraction, 97wt%-99% of an active material and 1wt%-3wt% of a binder; the active material comprises a cathode active material, a solid electrolyte material, and a conductive agent; the cathode active material comprises 60wt%-70wt% of the active material; the solid electrolyte material comprises 28wt%-30wt% of the active material; the conductive agent comprises 2wt%-10wt% of the active material; and the solid electrolyte is selected from chloride-based solid electrolytes.

[0008] In some alternative embodiments, the positive electrode active material includes LiNi. 0.83 Mn 0.06 Co 0.11 O2, LiNi 0.8 Mn 0.1 Co 0.1 O2, LiNi 0.5 Mn 0.3 Co 0.2 At least one of O2.

[0009] In some alternative embodiments, the solid electrolyte material includes at least one of Li3InCl6, Li3YCl6, or LiAlCl3.

[0010] In some alternative embodiments, the conductive agent comprises carbon nanofibers.

[0011] In some alternative embodiments, the mass ratio of the positive electrode active material to the solid electrolyte material is (12-13):6.

[0012] In some alternative embodiments, the adhesive includes at least one of polyvinylidene fluoride, polytetrafluoroethylene, and styrene-butadiene rubber.

[0013] Secondly, the present invention provides a method for preparing a composite positive electrode material, comprising the following steps: S1, mixing and stirring a positive electrode active material, a solid electrolyte material, and a conductive agent to obtain an active material; S2, mixing the active material and a binder, stirring, and drying to obtain the positive electrode active material.

[0014] In some alternative embodiments, the positive electrode active material includes LiNi. 0.83 Mn 0.06 Co 0.11 O2, LiNi 0.8 Mn 0.1 Co 0.1 O2, LiCoO2, LiNi 0.5 Mn 0.3 Co 0.2 At least one of O2.

[0015] In some alternative embodiments, the solid electrolyte material includes at least one of Li3InCl6, Li3YCl6, or LiAlCl3.

[0016] In some alternative embodiments, the conductive agent comprises carbon nanofibers.

[0017] In some optional embodiments, in step S2, the mass ratio of the positive electrode active material, the solid electrolyte material, and the conductive agent is (60-70):(25-30):(2-10).

[0018] In some optional embodiments, in step S2, the mixing and stirring atmosphere is an argon atmosphere or a nitrogen atmosphere.

[0019] In some optional embodiments, in step S2, the mixing speed is 150 rpm to 300 rpm; the mixing time is 20 min to 40 min.

[0020] In some alternative embodiments, in step S3, the adhesive includes at least one of polyvinylidene fluoride, polytetrafluoroethylene, and styrene-butadiene rubber.

[0021] In some optional embodiments, in step S3, the binder accounts for 1%-3% of the mass fraction of the active material.

[0022] In some optional embodiments, in step S3, the stirring speed is 150 rpm to 300 rpm; the stirring time is 0.3 h to 0.6 h.

[0023] In some alternative embodiments, in step S3, the stirring atmosphere is an argon atmosphere or a nitrogen atmosphere.

[0024] Thirdly, the present invention provides a positive electrode sheet, the positive electrode sheet comprising the composite positive electrode material described in the first aspect or the composite positive electrode material prepared by the preparation method described in the second aspect.

[0025] Fourthly, the present invention provides a lithium-ion solid-state battery, the lithium-ion solid-state battery comprising the composite cathode material described in the first aspect, the composite cathode material prepared by the preparation method described in the second aspect, or the cathode sheet described in the third aspect.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows: The composite cathode material provided by this invention comprises, by mass fraction, 97wt%-99% active material and 1wt%-3wt% binder; the active material includes a cathode active material, a solid electrolyte material, and a conductive agent; the cathode active material comprises 60wt%-70wt% of the active material; the solid electrolyte material comprises 28wt%-30wt% of the active material; the conductive agent comprises 2wt%-10wt% of the active material; and the solid electrolyte is selected from chloride-based solid electrolytes. This invention improves the active material loading, utilization rate, and energy density of the cathode sheet under low stacking pressure by selecting a chloride-based solid electrolyte with high ionic conductivity as a component of the active material and optimizing the proportion of the active material. This enhances the ionic conductivity of the composite cathode material and reduces the negative impact of volume changes in the cathode sheet, thereby enabling lithium-ion solid-state batteries containing this composite cathode material to operate at low stacking pressure (10MPa) and high current density (1 mA / cm²). 2 It exhibits high capacity and cycle stability under certain conditions. Detailed Implementation

[0027] The following embodiments are provided to better understand the present invention, but the following embodiments do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the scope of protection of the present invention.

[0028] Unless otherwise specified, all experimental steps or conditions in the examples were performed according to conventional experimental procedures and conditions in the art. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0029] Example 1 This embodiment provides a method for preparing a positive electrode sheet, including the following steps: (1) Mix LiCl and InCl3 in a molar ratio of 3:1, ball mill for 20 h under an argon atmosphere, then anneal at 500 °C for 5 h, and sieve (200 mesh) to obtain Li3InCl6 solid electrolyte material; (2) The positive electrode active material (LiNi) with a particle size of 1-5 μm is used. 0.83 Mn 0.06 Co 0.11 O2), the solid electrolyte material (Li3InCl6) obtained in step (1) and the conductive agent (CNF) are mixed in a mass ratio of 65:30:5 and stirred under an argon atmosphere to obtain an active material. The stirring speed is 200 rpm and the stirring time is 30 min. (3) The active material and a 3 wt% N-methylpyrrolidone solution of polytetrafluoroethylene were stirred at 200 rpm for 2 h under an argon atmosphere, then allowed to stand at 50 °C for 1 h, and then vacuum dried at 90 °C for 6 h to obtain the composite cathode material; wherein, the mass of polytetrafluoroethylene was 3% of the active material. (4) The positive electrode composite positive electrode material is pressed into shape under an argon atmosphere with a pressure of 10 MPa to obtain a positive electrode sheet with a thickness of 70 μm and a diameter of 10 mm.

[0030] Example 2 This embodiment provides a method for preparing a positive electrode sheet, including the following steps: (1) Mix LiCl and InCl3 in a molar ratio of 3:1, ball mill for 20 h under an argon atmosphere, then anneal at 500 °C for 5 h, and sieve (200 mesh) to obtain Li3InCl6 solid electrolyte material; (2) The positive electrode active material (LiNi) with a particle size of 1-5 μm is used. 0.83 Mn 0.06 Co 0.11 O2), the solid electrolyte material (Li3InCl6) obtained in step (1) and the conductive agent (CNF) are mixed at a mass ratio of 70:28:2 and stirred under an argon atmosphere to obtain the active material; wherein, the stirring speed is 200 rpm and the stirring time is 30 min; (3) The active material and a 3 wt% N-methylpyrrolidone solution of polytetrafluoroethylene were stirred at 200 rpm for 2 h under an argon atmosphere, then allowed to stand at 50 °C for 1 h, and then vacuum dried at 90 °C for 6 h to obtain the composite cathode material; wherein, the mass of polytetrafluoroethylene was 3% of the active material. (4) The positive electrode composite positive electrode material is pressed into shape under an argon atmosphere with a pressure of 10 MPa to obtain a positive electrode sheet with a thickness of 70 μm and a diameter of 10 mm.

[0031] Example 3 This embodiment provides a method for preparing a positive electrode sheet, including the following steps: (1) Mix LiCl and InCl3 in a molar ratio of 3:1, ball mill for 20 h under an argon atmosphere, then anneal at 500 °C for 5 h, and sieve (200 mesh) to obtain Li3InCl6 solid electrolyte material; (2) The positive electrode active material (LiNi) with a particle size of 1-5 μm is used. 0.83 Mn 0.06 Co 0.11O2), the solid electrolyte material (Li3InCl6) obtained in step (1) and the conductive agent (CNF) are mixed in a mass ratio of 60:30:10 and stirred under an argon atmosphere to obtain an active material; wherein, the stirring speed is 200 rpm and the stirring time is 30 min; (3) The active material and a 3 wt% N-methylpyrrolidone solution of polytetrafluoroethylene were stirred at 200 rpm for 2 h under an argon atmosphere, then allowed to stand at 50 °C for 1 h, and then vacuum dried at 90 °C for 6 h to obtain the composite cathode material; wherein, the mass of polytetrafluoroethylene was 3% of the active material. (4) The positive electrode composite positive electrode material is pressed into shape under an argon atmosphere with a pressure of 10 MPa to obtain a positive electrode sheet with a thickness of 70 μm and a diameter of 10 mm.

[0032] Example 4 This embodiment provides a method for preparing a positive electrode sheet, including the following steps: (1) Mix LiCl and YCl3 in a molar ratio of 3:1, ball mill for 20 h under an argon atmosphere, then anneal at 500 °C for 5 h, and sieve (200 mesh) to obtain Li3YCl6 solid electrolyte material; (2) The positive electrode active material (LiNi) with a particle size of 1-5 μm is used. 0.83 Mn 0.06 Co 0.11 O2), the solid electrolyte material (Li3YCl6) obtained in step (1) and the conductive agent (CNF) are mixed in a mass ratio of 65:30:5 and stirred under an argon atmosphere to obtain the active material; wherein, the stirring speed is 200 rpm and the stirring time is 30 min; (3) The active material and a 3 wt% N-methylpyrrolidone solution of polytetrafluoroethylene were stirred at 200 rpm for 2 h under an argon atmosphere, then allowed to stand at 50 °C for 1 h, and then vacuum dried at 90 °C for 6 h to obtain the composite cathode material; wherein, the mass of polytetrafluoroethylene was 3% of the active material. (4) The positive electrode composite positive electrode material is pressed into shape under an argon atmosphere with a pressure of 10 MPa to obtain a positive electrode sheet with a thickness of 70 μm and a diameter of 10 mm.

[0033] Example 5 This embodiment provides a method for preparing a positive electrode sheet, including the following steps: (1) Mix LiCl and AlCl3 in a molar ratio of 1:1, ball mill for 20 h under an argon atmosphere, then anneal at 500 °C for 5 h, and sieve (200 mesh) to obtain LiAlCl3 solid electrolyte material. (2) The positive electrode active material (LiNi) with a particle size of 1-5 μm is used. 0.83 Mn 0.06 Co 0.11 O2), the solid electrolyte material (LiAlCl3) obtained in step (1) and the conductive agent (CNF) are mixed in a mass ratio of 65:30:5 and stirred under an argon atmosphere to obtain the active material; wherein, the stirring speed is 200 rpm and the stirring time is 30 min; (3) The active material and a 3 wt% N-methylpyrrolidone solution of polytetrafluoroethylene were stirred at 200 rpm for 2 h under an argon atmosphere, then allowed to stand at 50 °C for 1 h, and then vacuum dried at 90 °C for 6 h to obtain the composite cathode material; wherein, the mass of polytetrafluoroethylene was 3% of the active material. (4) The positive electrode composite positive electrode material is pressed into shape under an argon atmosphere with a pressure of 10 MPa to obtain a positive electrode sheet with a thickness of 70 μm and a diameter of 10 mm.

[0034] Example 6 This embodiment provides a method for preparing a positive electrode sheet, including the following steps: (1) Mix LiCl and InCl3 in a molar ratio of 3:1, ball mill for 20 h under an argon atmosphere, then anneal at 500 °C for 5 h, and sieve (200 mesh) to obtain Li3InCl6 solid electrolyte material; (2) The positive electrode active material LiNi8Mn with a particle size of 1-5 μm 0.1 Co 0.1 O2, the solid electrolyte material (Li3InCl6) obtained in step (1) and the conductive agent (CNF) are mixed in a mass ratio of 65:30:5 and stirred under an argon atmosphere to obtain the active material; wherein, the stirring speed is 200 rpm and the stirring time is 30 min; (3) The active material and a 3 wt% N-methylpyrrolidone solution of polytetrafluoroethylene were stirred at 200 rpm for 2 h under an argon atmosphere, then allowed to stand at 50 °C for 1 h, and then vacuum dried at 90 °C for 6 h to obtain the composite cathode material; wherein, the mass of polytetrafluoroethylene was 3% of the active material. (4) The positive electrode composite positive electrode material is pressed into shape under an argon atmosphere with a pressure of 10 MPa to obtain a positive electrode sheet with a thickness of 70 μm and a diameter of 10 mm.

[0035] Comparative Example 1 This comparative example provides a method for preparing a positive electrode sheet, including the following steps: (1) Mix LiCl and InCl3 in a molar ratio of 3:1, ball mill for 20 h under an argon atmosphere, then anneal at 500 °C for 5 h, and sieve (200 mesh) to obtain Li3InCl6 solid electrolyte material; (2) The positive electrode active material (LiNi) with a particle size of 1-5 μm is used. 0.83 Mn 0.06 Co 0.11 O2), the solid electrolyte material (Li3InCl6) obtained in step (1) and the conductive agent (CNF) are mixed in a mass ratio of 75:20:2 and stirred under an argon atmosphere to obtain the active material; wherein, the stirring speed is 200 rpm and the stirring time is 30 min; (3) The active material and a 3 wt% N-methylpyrrolidone solution of polytetrafluoroethylene were stirred at 200 rpm for 2 h under an argon atmosphere, then allowed to stand at 50 °C for 1 h, and then vacuum dried at 90 °C for 6 h to obtain the composite cathode material; wherein, the mass of polytetrafluoroethylene was 3% of the active material. (4) The positive electrode composite positive electrode material is pressed into shape under an argon atmosphere with a pressure of 10 MPa to obtain a positive electrode sheet with a thickness of 70 μm and a diameter of 10 mm.

[0036] Comparative Example 2 This comparative example provides a method for preparing a positive electrode sheet, including the following steps: (1) Mix LiCl and InCl3 in a molar ratio of 3:1, ball mill for 20 h under an argon atmosphere, then anneal at 500 °C for 5 h, and sieve (200 mesh) to obtain Li3InCl6 solid electrolyte material; (2) The positive electrode active material (LiNi) with a particle size of 1-5 μm is used. 0.83 Mn 0.06 Co 0.11 O2), the solid electrolyte material (Li3InCl6) obtained in step (1) and the conductive agent (CNF) are mixed in a mass ratio of 55:40:5 and stirred under an argon atmosphere to obtain an active material; wherein, the stirring speed is 200 rpm and the stirring time is 30 min; (3) The active material and a 3 wt% N-methylpyrrolidone solution of polytetrafluoroethylene were stirred at 200 rpm for 2 h under an argon atmosphere, then allowed to stand at 50 °C for 1 h, and then vacuum dried at 90 °C for 6 h to obtain the composite cathode material; wherein, the mass of polytetrafluoroethylene was 3% of the active material. (4) The positive electrode composite positive electrode material is pressed into shape under an argon atmosphere with a pressure of 10 MPa to obtain a positive electrode sheet with a thickness of 70 μm and a diameter of 10 mm.

[0037] Performance testing The positive electrode sheets prepared in Examples 1-6 and Comparative Examples 1-2 were respectively coated onto the surface of a carbon-coated aluminum foil current collector and pressed under a pressure of 10 MPa to obtain a positive electrode plate with a thickness of 70 μm.

[0038] Solid-state battery fabrication: The positive electrode, the first solid electrolyte layer, the second solid electrolyte layer, and the negative electrode are stacked in the order of composite positive electrode plate and Li3InCl6 / Li6PS5Cl / Li-In alloy in a battery mold. The stacking pressure of 10 MPa is applied under an anhydrous and oxygen-free argon atmosphere to obtain the solid-state battery. The thickness of the first electrolyte layer is 50 μm, the thickness of the second electrolyte layer is 50 μm, and the thickness of the negative electrode is 100 μm.

[0039] The electrochemical performance of the assembled solid-state battery was tested using the LAND CT2001A battery testing system. The testing method is as follows: At 80℃, with a current of 0.5mA / cm 2 and 1.0 mA / cm 2 The battery is charged at a constant current density with an upper limit of 4.2V. After reaching the upper limit of the voltage, it is discharged at the same current density to the lower limit of 2.6V, thus completing the first charge-discharge cycle. Among them, the first discharge areal specific capacity (mA / cm) 2 = (discharge current (mA) × discharge time (h)) / mass of positive electrode active material (g).

[0040] Cyclic performance test: At 80℃ and a constant stacking pressure of 10MPa, at a rate of 1.0mA / cm 2 After charging to 4.2V under constant current and constant voltage, let it stand for 5 minutes, then charge at 1.0mA / cm. 2 A constant current discharge to the lower voltage limit of 2.6V constitutes one cycle. The discharge capacity of the first cycle is C1, and the discharge capacity after 50 cycles is C2. The capacity retention rate is C2 / C1×100%.

[0041] Table 1 Performance test results of each embodiment and comparative example

[0042] As shown in Table 1, the solid-state batteries prepared from the positive electrode sheets of Examples 1-6 have a performance of 0.5 mA / cm². 2 The initial charge specific capacity at the given current density is 184.1 mAh g. -1 -215.1mAh g -1 Within the range, all were higher than the 175.3 mAh g of Comparative Examples 1-2.-1 -183.5mAh g -1 The solid-state batteries prepared from the positive electrode sheets in Examples 1-6 achieve an efficiency of 1.0 mA / cm². 2 The initial charge specific capacity at the given current density is 176.3 mAh g. -1 -210.2mAh g -1 Within the range, all were higher than the 167.7 mAh g of Comparative Examples 1-2. -1 -178.9mAh g -1 The solid-state batteries prepared from the positive electrode sheets in Examples 1-6 exhibited a 50-cycle retention rate of 88.3%-94.5%, which is significantly higher than the 80.5%-85.9% of Comparative Examples 1-2. This demonstrates that the composite positive electrode material provided by this invention, by selecting a chloride-based solid electrolyte with high ionic conductivity as a component of the active material and optimizing the proportions of each active material, significantly improves the capacity and cycle stability of lithium-ion solid-state batteries containing this composite positive electrode material.

[0043] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A composite cathode material, characterized in that, By mass fraction, it includes 97wt%-99% active materials and 1wt%-3wt% binder; The active material includes a positive electrode active material, a solid electrolyte material, and a conductive agent; The positive electrode active material comprises 60wt%-70wt% of the active material; The solid electrolyte material has a mass fraction of 28wt%-30wt% in the active material; The conductive agent has a mass fraction of 2wt%-10wt% in the active material; The solid electrolyte is selected from chloride-based solid electrolytes.

2. The composite cathode material of claim 1, wherein, The positive electrode active material includes LiNi. 0.83 Mn 0.06 Co 0.11 O2, LiNi 0.8 Mn 0.1 Co 0.1 O2, LiNi 0.5 Mn 0.3 Co 0.2 At least one of O2; Preferably, the solid electrolyte material includes at least one of Li3InCl6, Li3YCl6, or LiAlCl3; Preferably, the conductive agent comprises carbon nanofibers; Preferably, the mass ratio of the positive electrode active material to the solid electrolyte material is (12-13):

6.

3. The composite cathode material of claim 1, wherein, The adhesive includes at least one of polyvinylidene fluoride, polytetrafluoroethylene, and styrene-butadiene rubber.

4. The method of producing a composite cathode material according to any one of claims 1 to 3, characterized in that, Includes the following steps: S1. Mix and stir the positive electrode active material, solid electrolyte material, and conductive agent to obtain the active material; S2. The active material and binder are mixed, stirred and dried to obtain the positive electrode active material.

5. The production method according to claim 4, characterized by, The positive electrode active material includes LiNi. 0.83 Mn 0.06 Co 0.11 O2, LiNi 0.8 Mn 0.1 Co 0.1 O2, LiCoO2, LiNi 0.5 Mn 0.3 Co 0.2 At least one of O2; Preferably, the solid electrolyte material includes at least one of Li3InCl6, Li3YCl6, or LiAlCl3; Preferably, the conductive agent comprises carbon nanofibers.

6. The preparation method according to claim 4, characterized in that, In step S2, the mass ratio of the positive electrode active material, the solid electrolyte material, and the conductive agent is (60-70):(25-30):(2-10). In step S2, the atmosphere for mixing and stirring is an argon atmosphere or a nitrogen atmosphere; In step S2, the mixing speed is 150 rpm to 300 rpm; the mixing time is 20 min to 40 min.

7. The preparation method according to claim 4, characterized in that, In step S3, the adhesive includes at least one of polyvinylidene fluoride, polytetrafluoroethylene, and styrene-butadiene rubber.

8. The preparation method according to claim 4, characterized in that, In step S3, the binder accounts for 1%-3% of the mass fraction of the active material; In step S3, the stirring speed is 150 rpm-300 rpm; the stirring time is 0.3 h-0.6 h. In step S3, the stirring atmosphere is an argon atmosphere or a nitrogen atmosphere.

9. A positive electrode sheet characterized by comprising: The positive electrode sheet includes the composite positive electrode material according to any one of claims 1-3 or the composite positive electrode material prepared by the preparation method according to any one of claims 4-8.

10. A lithium-ion solid-state battery, characterized by, The lithium-ion solid-state battery includes the composite cathode material according to any one of claims 1-3, the composite cathode material prepared by the preparation method according to any one of claims 4-8, or the cathode sheet according to claim 9.

Images