Preparation method of a non-separator all-solid-state battery

Abstract

The present invention provides a method for preparing a non-separator all-solid-state battery, belonging to the technical field of solid-state batteries, comprising the steps of: S1. Coating a positive electrode slurry on the surface of a positive current collector to obtain a positive electrode sheet; S2. Coating a functional slurry on the surface of the positive electrode sheet to form a functional layer; the functional slurry comprises, by mass percentage, 15-18% of lithium niobate, 5-6% of nano-aluminum oxide, 3-5% of a binder and the balance of a solvent; S3. Coating an electrolyte slurry on the surface of the functional layer to form a semi-solid electrolyte; the electrolyte slurry comprises, by mass percentage, 5-7% of porous carbon-coated alumina particles, 7-9% of a binder and the balance of an electrolyte solution; S4. Coating a negative electrode slurry on the surface of the semi-solid electrolyte, then covering with a negative current collector, applying a surface pressure of 450-650 N / m<supgt;2< / supgt>, and heat-treating at 80-100 °C for 12-15 h in an inert environment to obtain an electrode core body; S5. Encapsulating, compacting and sealing the electrode core body to obtain a non-separator all-solid-state battery. The present invention can improve the cycle life of the prepared non-separator all-solid-state battery.

Description

Technical Field

[0001] The present invention belongs to the technical field of solid-state batteries, and particularly relates to a method for preparing a non-separator all-solid-state battery. Background Art

[0002] Traditional liquid lithium batteries are also vividly called "rocking chair batteries" by scientists. The two ends of the rocking chair are the positive and negative electrodes of the battery, and the middle is the electrolyte (liquid). And lithium ions are like excellent athletes, running back and forth at both ends of the rocking chair. During the movement of lithium ions from the positive electrode to the negative electrode and then back to the positive electrode, the charging and discharging process of the battery is completed. The principle of solid-state batteries is the same, except that their electrolyte is solid, and the density and structure thereof can allow more charged ions to gather at one end, conduct a larger current, and thus improve the battery capacity. Therefore, for the same amount of electricity, the volume of the solid-state battery will become smaller.

[0003] In solid-state batteries, the solid-solid interface between the solid electrolyte and the electrode material is one of the key factors affecting battery performance. Research shows that during the curing process of the solid electrolyte, lithium ions will concentrate on the surface layer, and this phenomenon plays an important role in improving the interface stability and conductivity of the battery. When lithium ions are enriched at the interface, a stable lithium ion conduction layer can be formed, which helps to reduce the interface resistance and improve the charging and discharging efficiency of the battery.

[0004] However, this concentration effect will cause problems such as excessive local current density, local overheating, aggravated dendrite growth or interface failure, affecting the cycle life of the battery. Summary of the Invention

[0005] To solve the problems in the background art, the present invention provides a method for preparing a non-separator all-solid-state battery, which can improve the cycle life of the obtained non-separator all-solid-state battery.

[0006] To achieve the above object, the present invention provides a method for preparing a non-separator all-solid-state battery, including the following steps:

[0007] S1. Coating a positive electrode paste on the surface of a positive current collector with a surface loading of 25-30 mg / cm 2 , and baking to a semi-dry state to obtain a positive electrode sheet;

[0008] S2. Coating a functional paste on the surface of the positive electrode sheet with a surface loading of 4-5 mg / cm 2 , and baking to a semi-dry state to form a functional layer; the components of the functional paste are calculated by mass percentage and include 15-18% of lithium niobate, 5-6% of nano-aluminum oxide, 3-5% of a binder, and the balance of a solvent;

[0009] S3. Coating an electrolyte paste on the surface of the functional layer with a surface loading of 15-18 mg / cm 2, bake until it reaches a semi-dry state to form a semi-solid electrolyte; the components of the electrolyte slurry are calculated by mass percentage, including 5-7% of porous carbon-coated alumina particles, 7-9% of binder, and the balance of electrolyte;

[0010] S4. Coat the surface of the semi-solid electrolyte with a negative electrode slurry, with a surface loading of 25-30 mg / cm 2 , then cover the surface with a negative current collector and apply pressure on the surface, with the pressure being 450-650 N / m 2 , heat-treat in an inert environment of an oven at 80-100 °C for 12-15 h to obtain the cell body;

[0011] S5. Package, compact, and seal the cell body to obtain a non-separator all-solid-state battery.

[0012] Furthermore, in S3, the preparation method of the porous carbon-coated alumina particles is as follows:

[0013] A1. By weight, disperse 1 part of nano-alumina in 10-15 parts of absolute ethanol, then add 0.02-0.04 part of silane coupling agent, stir for 20-30 min, and filter to obtain activated alumina;

[0014] A2. Mix the activated alumina obtained in A1 with oleic acid at a mass ratio of 1:3, then perform ball milling for 0.5-1.5 h, and filter to obtain modified alumina;

[0015] A3. Put the modified alumina, fine-grained asphalt, and graphite into a high-speed mixer at a mass ratio of 5:1:1, stir for 2-3 h, and mix evenly to obtain a mixture;

[0016] A4. Place the mixture in a tubular furnace, under nitrogen protection, heat it to 1000-1200 °C at a rate of 3-5 °C / min, keep it warm for 4-6 h, then naturally cool to room temperature, grind it, and pass through a 500-mesh sieve to obtain porous carbon-coated alumina particles.

[0017] Furthermore, in A1, the silane coupling agent is KH550.

[0018] Furthermore, in S3, the electrolyte is lithium iron manganese phosphate electrolyte KLD-LMFP03A.

[0019] Furthermore, in S1, the components of the positive electrode slurry are calculated by mass percentage, including 45-50% of lithium cobaltate, 4-5% of binder, 2-3% of carbon black, and the balance of solvent.

[0020] Furthermore, in S4, the components of the negative electrode slurry are calculated by mass percentage, including 35-40% of silicon carbon, 4-5% of binder, 2-3% of carbon black, and the balance of solvent.

[0021] Further, the binder includes polyvinylidene fluoride and / or sodium carboxymethyl cellulose.

[0022] Further, the solvent includes N-methylpyrrolidone and / or ethyl methyl carbonate.

[0023] Further, the positive current collector is aluminum foil and the negative current collector is copper foil.

[0024] This application has the following beneficial effects:

[0025] 1. In the preparation of the non-separator all-solid-state battery of the present invention, a functional slurry is coated on the surface of the positive electrode sheet to form a functional layer. The functional slurry contains 15-18% of lithium niobate; an electrolyte slurry is coated on the surface of the functional layer to form a semi-solid electrolyte. The electrolyte slurry contains alumina microparticles coated with porous carbon; when the functional slurry contains 15-18% of lithium niobate, the alumina microparticles coated with porous carbon contained in the electrolyte slurry can produce a synergistic effect with it, synergistically improving the cycle life of the prepared battery, so that the cycle times of the prepared battery until the capacity retention rate drops to 80% during 0.5C charging / 0.5C discharging are up to more than 1691 times.

[0026] 2. The lithium niobate contained in the functional slurry coated on the surface of the positive electrode sheet can effectively inhibit the chemical / electrochemical side reactions and interface creep at the positive electrode side interface. This interface modification layer can have a certain repulsive effect on lithium ions, thus affecting their distribution and migration at the interface.

[0027] At the same time, the alumina microparticles coated with porous carbon contained in the electrolyte slurry, as a kind of porous microparticles, not only have more surface areas to contact with lithium ions, thus increasing the adsorption and transmission opportunities of lithium ions, but also provide effective diffusion channels for lithium ions, shortening the diffusion distance of lithium ions, thereby improving the transmission efficiency of lithium ions, and further being able to have a certain traction effect on lithium ions, affecting their distribution and migration. Description of the Drawings

[0028] Figure 1 、Comparison trend chart of the cycle times test data of the batteries prepared in Example 1-Example 5 and Comparative Example 1-Comparative Example 6 of the present invention until the capacity retention rate drops to 80% during 0.5C charging / 0.5C discharging. Detailed Embodiments

[0029] The following further describes this application in detail with reference to the embodiments.

[0030] The raw materials of the embodiments and comparative examples of this application are all commercially available as usual unless otherwise specified.

[0031] Example 1: (1) Prepare alumina microparticles coated with porous carbon, and its preparation method is as follows:

[0032] A1. Disperse 1 part of nano-aluminum oxide in 12 parts of absolute ethanol by weight, then add 0.03 part of KH550, and stir evenly at a stirring speed of 240 r / min for 25 min, and then filter to obtain activated aluminum oxide.

[0033] A2. Mix the activated aluminum oxide obtained in A1 with oleic acid at a mass ratio of 1:3, then carry out ball milling for 1 h, and filter to obtain modified aluminum oxide.

[0034] A3. Put the modified aluminum oxide, fine-grained asphalt and graphite into a high-speed mixer at a mass ratio of 5:1:1, stir for 2.5 h, and mix evenly to obtain a mixture.

[0035] A4. Place the mixture in a tubular furnace, under the protection of nitrogen, heat it to 1100 °C at a rate of 4 °C / min, keep it warm for 5 h, then naturally cool it to room temperature, grind it, and pass through a 500-mesh sieve to obtain porous carbon-coated aluminum oxide particles.

[0036] Among them, the nano-aluminum oxide (99.9%) is 50 nm grade and is purchased from Hangzhou Jiupeng New Materials Co., Ltd. The fine-grained asphalt (AC-10) is purchased from Shenzhen Huafa Asphalt Engineering Co., Ltd. The graphite is colloidal graphite (S-0) and is purchased from Qingdao Risheng Graphite Co., Ltd.

[0037] (2) A preparation method of a non-separator all-solid-state battery, comprising the following steps:

[0038] S1. Coat the positive electrode slurry on the surface of the positive current collector with a surface loading of 27.3 mg / cm 2 , and bake it to a semi-dry state to obtain a positive electrode sheet. The positive current collector is aluminum foil. The components of the positive electrode slurry are calculated by mass percentage, including 48% of lithium cobaltate, 4.5% of binder polyvinylidene fluoride, 2.5% of carbon black, and 45% of solvent N-methylpyrrolidone.

[0039] Among them, the lithium cobaltate (with a content of 98%) is purchased from Henan Shuangjie Chemical Co., Ltd. The polyvinylidene fluoride (Solvay 6008 from the United States) is purchased from Shanghai Henghang Maosu Plastic Co., Ltd. The carbon black is conductive carbon black XC72 (CABOT Cabot) and is purchased from Tianjin Tianyi Century Chemical Products Technology Development Co., Ltd. The N-methylpyrrolidone (with a content of 99.9%) is purchased from Jinan Xinke Chemical Co., Ltd.

[0040] S2. Coat the functional slurry on the surface of the positive electrode sheet with a surface loading of 4.5 mg / cm 2 , and bake it to a semi-dry state to form a functional layer; the components of the functional slurry are calculated by mass percentage, including 16% of lithium niobate, 5.5% of nano-aluminum oxide, 4% of binder polyvinylidene fluoride, and 74.5% of solvent N-methylpyrrolidone.

[0041] Among them, lithium niobate (99%, industrial grade) was purchased from Hubei Jusheng Technology Co., Ltd.

[0042] S3. The surface of the functional layer is coated with an electrolyte slurry with a surface loading of 16.2 mg / cm 2 , and baked to a semi-dry state to form a semi-solid electrolyte; the components of the electrolyte slurry are calculated by mass percentage, including 6% of porous carbon-coated alumina particles, 8% of the binder polyvinylidene fluoride, and 86% of the electrolyte solution.

[0043] Among them, the electrolyte solution is lithium iron manganese phosphate electrolyte KLD-LMFP03A, which was purchased from Dongguan Kelude New Energy Technology Co., Ltd.

[0044] S4. The surface of the semi-solid electrolyte is coated with a negative electrode slurry with a surface loading of 26.8 mg / cm 2 , and then a negative current collector is covered on its surface, and the surface is pressurized with a pressure of 550 N / m 2 , and heat-treated at 90 °C for 13 h in an inert environment of an oven to obtain a battery cell body. The components of the negative electrode slurry are calculated by mass percentage, including 38% of silicon carbon, 4.5% of the binder polyvinylidene fluoride, 2.5% of carbon black, and 55% of the solvent N-methylpyrrolidone. The negative current collector is copper foil.

[0045] Among them, silicon carbon was purchased from Fujian Xinsen Carbon Industry Co., Ltd.

[0046] S5. The battery cell body is encapsulated with an aluminum-plastic film, and evacuated, compacted, and sealed in a vacuum environment to obtain a non-separator all-solid-state battery.

[0047] Example 2: The difference between this example and Example 1 is: (1) Preparation of porous carbon-coated alumina particles, and the preparation method is as follows:

[0048] A1. By weight, disperse 1 part of nano-alumina in 10 parts of absolute ethanol, then add 0.02 part of KH550, and stir evenly at a stirring speed of 240 r / min for 20 min, and filter to obtain activated alumina.

[0049] A2. Mix the activated alumina obtained in A1 with oleic acid in a mass ratio of 1:3, then carry out ball milling for 0.5 h, and filter to obtain modified alumina.

[0050] A3. Put the modified alumina, fine-grained asphalt, and graphite into a high-speed mixer in a mass ratio of 5:1:1, stir for 2 h, and mix evenly to obtain a mixture.

[0051] A4. Place the mixture in a tube furnace, under nitrogen protection, heat it to 1000 °C at a rate of 3 °C / min, keep it warm for 4 h, then naturally cool to room temperature, grind it, and pass through a 500-mesh sieve to obtain porous carbon-coated alumina particles.

[0052] Example 3: The difference between this example and Example 1 is as follows: (1) Preparation of porous carbon-coated alumina particles, and the preparation method is as follows:

[0053] A1. By weight, disperse 1 part of nano-alumina in 15 parts of absolute ethanol, then add 0.04 part of KH550, and stir evenly at a stirring speed of 240 r / min for 30 min, and filter to obtain activated alumina.

[0054] A2. Mix the activated alumina obtained in A1 with oleic acid at a mass ratio of 1:3, then carry out ball milling for 1.5 h, and filter to obtain modified alumina.

[0055] A3. Put the modified alumina, fine-grained asphalt and graphite into a high-speed mixer at a mass ratio of 5:1:1, stir for 3 h, and mix evenly to obtain a mixture.

[0056] A4. Place the mixture in a tubular furnace, under nitrogen protection, heat it to 1200 °C at a rate of 5 °C / min, keep it warm for 6 h, then naturally cool it to room temperature, grind it, and pass through a 500-mesh sieve to obtain porous carbon-coated alumina particles.

[0057] Example 4: The difference between this example and Example 1 is as follows: (2) A preparation method of a non-separating all-solid-state battery, including the following steps:

[0058] S1. Coat the positive electrode slurry on the surface of the positive current collector, with a surface loading of 25.3 mg / cm 2 , bake it to a semi-dry state to obtain a positive electrode sheet. The positive current collector is aluminum foil. By mass percentage, the components of the positive electrode slurry include 45% of lithium cobaltate, 4% of binder polyvinylidene fluoride, 2% of carbon black, and 49% of solvent N-methylpyrrolidone.

[0059] S2. Coat the functional slurry on the surface of the positive electrode sheet, with a surface loading of 4.1 mg / cm 2 , bake it to a semi-dry state to form a functional layer; by mass percentage, the components of the functional slurry include 15% of lithium niobate, 5% of nano-alumina, 3% of binder polyvinylidene fluoride, and 77% of solvent N-methylpyrrolidone.

[0060] S3. Coat the electrolyte slurry on the surface of the functional layer, with a surface loading of 15.5 mg / cm 2 , bake it to a semi-dry state to form a semi-solid electrolyte; by mass percentage, the components of the electrolyte slurry include 5% of porous carbon-coated alumina particles, 7% of binder polyvinylidene fluoride, and 88% of electrolyte solution. Among them, the electrolyte solution is lithium iron phosphate manganese electrolyte KLD-LMFP03A.

[0061] S4. Coat the negative electrode slurry on the surface of the semi-solid electrolyte, with a surface loading of 25.9 mg / cm 2, and then a negative current collector is covered on its surface, and pressure is applied to the surface, with the pressure being 450 N / m 2 , and it is heat-treated at 80 °C for 15 h in an inert environment of an oven to obtain the battery cell body. The components of the negative electrode paste are calculated by mass percentage and include 35% of silicon carbide, 4% of binder polyvinylidene fluoride, 2% of carbon black, and 59% of solvent N-methylpyrrolidone. The negative current collector is copper foil.

[0062] S5. The battery cell body is encapsulated, compacted, and sealed to obtain the non-separator all-solid-state battery.

[0063] Example 5: The difference between this example and Example 1 lies in: (2) A preparation method of a non-separator all-solid-state battery, including the following steps:

[0064] S1. A positive electrode paste is coated on the surface of the positive current collector, with a surface loading of 29.4 mg / cm 2 , and it is baked to a semi-dry state to obtain the positive electrode sheet. The positive current collector is aluminum foil. The components of the positive electrode paste are calculated by mass percentage and include 50% of lithium cobaltate, 5% of binder polyvinylidene fluoride, 3% of carbon black, and 42% of solvent N-methylpyrrolidone.

[0065] S2. A functional paste is coated on the surface of the positive electrode sheet, with a surface loading of 4.7 mg / cm 2 , and it is baked to a semi-dry state to form a functional layer; the components of the functional paste are calculated by mass percentage and include 18% of lithium niobate, 6% of nano-aluminum oxide, 5% of binder polyvinylidene fluoride, and 71% of solvent N-methylpyrrolidone.

[0066] S3. An electrolyte paste is coated on the surface of the functional layer, with a surface loading of 17.2 mg / cm 2 , and it is baked to a semi-dry state to form a semi-solid electrolyte; the components of the electrolyte paste are calculated by mass percentage and include 7% of porous carbon-coated alumina particles, 9% of binder polyvinylidene fluoride, and 84% of electrolyte solution. Among them, the electrolyte solution is lithium iron phosphate manganese electrolyte KLD-LMFP03A.

[0067] S4. A negative electrode paste is coated on the surface of the semi-solid electrolyte, with a surface loading of 29.7 mg / cm 2 , and then a negative current collector is covered on its surface, and pressure is applied to the surface, with the pressure being 650 N / m 2 , and it is heat-treated at 100 °C for 12 h in an inert environment of an oven to obtain the battery cell body. The components of the negative electrode paste are calculated by mass percentage and include 40% of silicon carbide, 5% of binder polyvinylidene fluoride, 3% of carbon black, and 52% of solvent N-methylpyrrolidone. The negative current collector is copper foil.

[0068] S5. The battery cell body is encapsulated, compacted, and sealed to obtain the non-separator all-solid-state battery.

[0069] Comparative Example 1: The difference between this comparative example and Example 1 is that in the functional slurry, lithium niobate is replaced by nano-aluminum oxide; and in the electrolyte slurry, the porous carbon-coated alumina particles are replaced by a mixture of nano-aluminum oxide and graphite, and the mass ratio of nano-aluminum oxide to graphite is 5:2.

[0070] Specifically, the components of the functional slurry are in mass percentage, including 21.5% of nano-aluminum oxide, 4% of the binder polyvinylidene fluoride, and 74.5% of the solvent N-methylpyrrolidone.

[0071] The components of the electrolyte slurry are in mass percentage, including 6% of the mixture of nano-aluminum oxide and graphite, 8% of the binder polyvinylidene fluoride, and 86% of the electrolyte.

[0072] Comparative Example 2: The difference between this comparative example and Example 1 is that in the functional slurry, the content of lithium niobate is 5%; and in the electrolyte slurry, the porous carbon-coated alumina particles are replaced by a mixture of nano-aluminum oxide and graphite, and the mass ratio of nano-aluminum oxide to graphite is 5:2.

[0073] Specifically, the components of the functional slurry are in mass percentage, including 5% of lithium niobate, 16.5% of nano-aluminum oxide, 4% of the binder polyvinylidene fluoride, and 74.5% of the solvent N-methylpyrrolidone.

[0074] The components of the electrolyte slurry are in mass percentage, including 6% of the mixture of nano-aluminum oxide and graphite, 8% of the binder polyvinylidene fluoride, and 86% of the electrolyte.

[0075] Comparative Example 3: The difference between this comparative example and Example 1 is that in the functional slurry, the content of lithium niobate is 5%.

[0076] Specifically, the components of the functional slurry are in mass percentage, including 5% of lithium niobate, 16.5% of nano-aluminum oxide, 4% of the binder polyvinylidene fluoride, and 74.5% of the solvent N-methylpyrrolidone.

[0077] Comparative Example 4: The difference between this comparative example and Example 1 is that in the functional slurry, the content of lithium niobate is 10%; and in the electrolyte slurry, the porous carbon-coated alumina particles are replaced by a mixture of nano-aluminum oxide and graphite, and the mass ratio of nano-aluminum oxide to graphite is 5:2.

[0078] Specifically, the components of the functional slurry are in mass percentage, including 10% of lithium niobate, 11.5% of nano-aluminum oxide, 4% of the binder polyvinylidene fluoride, and 74.5% of the solvent N-methylpyrrolidone.

[0079] The components of the electrolyte slurry are in mass percentage, including 6% of the mixture of nano-aluminum oxide and graphite, 8% of the binder polyvinylidene fluoride, and 86% of the electrolyte.

[0080] Comparative Example 5: The difference between this comparative example and Example 1 is that in the functional slurry, the content of lithium niobate is 10%.

[0081] Specifically, the components of the functional slurry are calculated by mass percentage, including 10% of lithium niobate, 11.5% of nano-aluminum oxide, 4% of the binder polyvinylidene fluoride, and 74.5% of the solvent N-methylpyrrolidone.

[0082] Comparative Example 6: The difference between this comparative example and Example 1 is that in the electrolyte slurry, the porous carbon-coated alumina particles are replaced by a mixture of nano-aluminum oxide and graphite, and the mass ratio of nano-aluminum oxide to graphite is 5:2.

[0083] Specifically, the components of the electrolyte slurry are calculated by mass percentage, including 6% of the mixture of nano-aluminum oxide and graphite, 8% of the binder polyvinylidene fluoride, and 86% of the electrolyte.

[0084] Test Example: Test Object: The batteries prepared in Examples 1-5 and Comparative Examples 1-6.

[0085] Test Item: Cycle Life - The number of cycles of 0.5C charge / 0.5C discharge until the capacity retention rate drops to 80%.

[0086] Test Results: See Table 1.

[0087] Table 1. Test Data of Test Examples

[0088]

[0089]

[0090] Result Analysis: Analyze Examples 1-5 and combine with the data in Table 1 and Figure 1 It can be seen that the battery prepared by the present invention has a cycle life of up to more than 1691 times for 0.5C charge / 0.5C discharge until the capacity retention rate drops to 80%.

[0091] Analyze Example 1 and Comparative Examples 1-6 and combine with the data in Table 1 and Figure 1 , by comparing Comparative Example 1 and Comparative Example 2, compared with Comparative Example 1, the functional slurry in Comparative Example 2 contains 5% of lithium niobate, and the cycle life of the prepared battery is 1518 times, which is significantly greater than the cycle life of 1469 times of the battery prepared in Comparative Example 1, indicating that adding 5% of lithium niobate to the functional slurry can improve the cycle life of the prepared battery.

[0092] Comparing Comparative Example 2 and Comparative Example 3, compared with Comparative Example 2, the electrolyte slurry in Comparative Example 3 contains porous carbon-coated alumina particles. As a result, the cycle life of the battery prepared is 1525 times, which is very close to the cycle life of 1518 times of the battery prepared in Comparative Example 2. This indicates that when the working slurry contains 5% lithium niobate, the presence of porous carbon-coated alumina particles in the electrolyte slurry has no obvious effect on the cycle life of the battery prepared.

[0093] Comparing Comparative Example 1 and Comparative Example 4, compared with Comparative Example 1, the working slurry in Comparative Example 4 contains 10% lithium niobate. As a result, the cycle life of the battery prepared is 1624 times, which is significantly greater than the cycle life of 1469 times of the battery prepared in Comparative Example 1. Moreover, it is significantly greater than the cycle life of 1518 times of the battery prepared in Comparative Example 2. This indicates that increasing the content of lithium niobate in the working slurry from 5% to 10% can further improve the cycle life of the battery prepared.

[0094] Comparing Comparative Example 4 and Comparative Example 5, compared with Comparative Example 4, the electrolyte slurry in Comparative Example 5 contains porous carbon-coated alumina particles. As a result, the cycle life of the battery prepared is 1671 times, which is greater than the cycle life of 1624 times of the battery prepared in Comparative Example 4. This indicates that when the working slurry contains 10% lithium niobate, the presence of porous carbon-coated alumina particles in the electrolyte slurry can slightly improve the cycle life of the battery prepared.

[0095] Comparing Comparative Example 1 and Comparative Example 6, compared with Comparative Example 1, the working slurry in Comparative Example 6 contains 16% lithium niobate. As a result, the cycle life of the battery prepared is 1598 times, which is significantly greater than the cycle life of 1469 times of the battery prepared in Comparative Example 1; however, it is less than the cycle life of 1624 times of the battery prepared in Comparative Example 4. This indicates that increasing the content of lithium niobate in the working slurry from 10% to 16% will instead cause a decrease in the cycle life of the battery prepared. This is because when the content of lithium niobate is too high, the repulsive effect on lithium ions is too strong, which has too great an impact on the distribution and reverse migration of lithium ions, resulting in a negative effect.

[0096] Comparing Comparative Example 6 and Example 1, compared with Comparative Example 6, the electrolyte slurry in Example 1 contains porous carbon-coated alumina particles. As a result, the cycle life of the battery prepared is 1708 times, which is significantly greater than the cycle life of 1598 times of the battery prepared in Comparative Example 6. Moreover, it is also significantly greater than the cycle life of 1671 times of the battery prepared in Comparative Example 5. This indicates that when the working slurry contains 16% lithium niobate, the porous carbon-coated alumina particles contained in the electrolyte slurry can have a synergistic effect with it, synergistically improving the cycle life of the battery prepared.

[0097] This is because the traction effect of the porous carbon-coated alumina particles on lithium ions will be amplified under the repulsive effect of lithium niobate on lithium ions. Although the repulsive effect of 16% lithium niobate on lithium ions is too strong to some extent and will cause a reverse effect, at the same time, it can also stimulate the traction effect of the porous carbon-coated alumina particles on lithium ions to be more prominent, and then work synergistically to make the final effect better.

[0098] In addition, it should be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present invention will not separately describe various possible combination methods.

[0099] In addition, any combination can be made between different embodiments of the present invention as long as it does not violate the idea of the present invention, and it should also be regarded as the content disclosed by the present invention.

Claims

1. A method for preparing a diaphragm-free all-solid-state battery, characterized in that: The steps include: S1. The positive current collector surface is coated with positive electrode slurry, with a surface loading of 25-30 mg / cm 2 , bake to a semi-dry state to obtain a positive electrode sheet; S2, positive electrode surface coating slurry, surface loading 4-5mg / cm 2 , baked to a semi-dry state to form an active layer; the components of the active slurry, by mass percentage, include 15-18% lithium niobate, 5-6% nano-aluminum oxide, 3-5% binder and the remainder solvent; S3, the surface of the active layer is coated with electrolyte slurry, with a surface loading of 15-18 mg / cm 2 , baked to a semi-dry state to form a semi-solid electrolyte; the components of the electrolyte slurry, by mass percentage, include 5-7% porous carbon-coated alumina particles, 7-9% binder and the remainder of electrolyte; S4, the surface of the semi-solid electrolyte is coated with negative electrode slurry, with a surface loading of 25-30 mg / cm 2 Then, a negative current collector is placed on the surface and the surface is pressurized to a pressure of 450-650 N / m 2 , heating treatment at 80-100° C. in an inert environment of an oven for 12-15 hours to obtain a battery cell; S5. Encapsulate, compact and seal the battery cell to obtain a diaphragm-free all-solid-state battery.

2. The method for preparing a diaphragm-free all-solid-state battery according to claim 1, characterized in that: In S3, the preparation method of the porous carbon-coated alumina particles is as follows: A1. Disperse 1 part of nano-alumina in 10-15 parts of anhydrous ethanol by weight, add 0.02-0.04 parts of silane coupling agent, stir for 20-30 minutes, filter, and obtain activated alumina; A2, mixing the activated alumina obtained in A1 with oleic acid in a mass ratio of 1:3, and ball milling for 0.5-1.5 h, filtering, and obtaining modified alumina; A3. Add modified alumina, fine-grained asphalt and graphite in a mass ratio of 5:1:1 into a high-speed mixer, stir for 2-3 hours, mix evenly, and obtain a mixture; A4. Place the mixture in a tube furnace, and under nitrogen protection, heat it to 1000-1200°C at 3-5°C / min, keep it warm for 4-6 hours, and then naturally cool it to room temperature. Grind it, and pass it through a 500-mesh screen to obtain porous carbon-coated alumina particles.

3. The method for preparing a diaphragm-free all-solid-state battery according to claim 2, characterized in that: In A1, the silane coupling agent is KH550.

4. The method for preparing a diaphragm-free all-solid-state battery according to claim 1, characterized in that: In S3, the electrolyte is lithium manganese iron phosphate electrolyte KLD-LMFP03A.

5. The method for preparing a diaphragm-free all-solid-state battery according to claim 1, characterized in that: In S1, the components of the positive electrode slurry include, by mass percentage, 45-50% lithium cobalt oxide, 4-5% binder, 2-3% carbon black and the remainder solvent.

6. The method for preparing a diaphragm-free all-solid-state battery according to claim 1, characterized in that: In S4, the components of the negative electrode slurry include, by mass percentage, 35-40% silicon carbon, 4-5% binder, 2-3% carbon black and the remainder solvent.

7. The method for preparing a diaphragm-free all-solid-state battery according to any one of claims 1 to 6, characterized in that: The solvent includes N-methylpyrrolidone and / or ethyl methyl carbonate.

8. The method for preparing a diaphragm-free all-solid-state battery according to any one of claims 1 to 6, characterized in that: The positive current collector is aluminum foil, and the negative current collector is copper foil.

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