All-solid-state battery and manufacturing method thereof

Abstract

The invention provides an all-solid-state battery and a manufacturing method thereof, belonging to the technical field of solid-state batteries. The all-solid-state battery comprises a positive electrode, a negative electrode and a solid electrolyte, the positive electrode comprises a positive current collector and a positive active slurry, the negative electrode comprises a negative current collector and a negative active slurry, the solid electrolyte is prepared from an electrolyte slurry, the positive active slurry, the negative active slurry and the electrolyte slurry all comprise lithium titanate intercalation graphite, a binder, a conductive agent and a solvent, and the mass proportion of the lithium titanate intercalation graphite in the three is 4.5-5.5%; the preparation method of the lithium titanate intercalation graphite is as follows: adding graphite to an ammonium sulfate aqueous solution with a mass fraction of 45-50%, then sequentially adding potassium permanganate and lithium titanate, stirring in a constant temperature water bath for 60 minutes, first washing with water and then soaking for 2-3 hours until the pH value is 6.0-7.0, filtering, drying in an oven at 60-70°C, and then calcining and expanding in a muffle furnace at 550-600°C to obtain the battery. The present invention can effectively improve the capacity retention rate of the prepared all-solid-state battery and extend the cycle service life of the all-solid-state battery.

Description

Technical Field

[0001] The present invention belongs to the technical field of solid-state batteries, and specifically relates to an all-solid-state battery and a manufacturing method thereof. Background Art

[0002] Solid-state batteries are a type of battery technology that uses solid electrolytes instead of traditional liquid electrolytes. The core of this technology is to use solid materials as ion-conducting media, thereby providing higher safety and energy density. Since there is no liquid electrolyte, solid-state batteries will not leak when physically damaged, greatly reducing the risk of thermal runaway and fire. The high energy density and safety of solid-state batteries make them an ideal choice for electric vehicles, which is expected to significantly increase the vehicle's range and safety. The miniaturization and flexibility of solid-state batteries make them widely used in portable electronic products such as smartphones and wearable devices.

[0003] However, the solid-solid contact between ordinary solid electrolytes and electrode materials leads to large interface impedance, which hinders the transmission of lithium ions during the electrochemical reaction, resulting in the inability of active substances to fully participate in the reaction, thereby accelerating the decay of capacity and reducing the cycle stability and cycle life of the battery. Summary of the invention

[0004] In order to solve the problems existing in the background technology, the present invention provides an all-solid-state battery and a method for manufacturing the same, which can reduce the capacity decay rate of the all-solid-state battery, thereby improving the capacity retention rate of the all-solid-state battery and extending the cycle service life of the all-solid-state battery.

[0005] In order to achieve the above-mentioned purpose, in a first aspect, the present invention provides an all-solid-state battery, comprising a positive electrode, a negative electrode and a solid electrolyte, wherein the positive electrode comprises a positive current collector and a positive active slurry disposed on the positive current collector, the negative electrode comprises a negative current collector and a negative active slurry disposed on the negative current collector, the solid electrolyte is made of an electrolyte slurry, the positive active slurry, the negative active slurry and the electrolyte slurry all comprise lithium titanate intercalated graphite, a binder, a conductive agent and a solvent, and the mass proportion of the lithium titanate intercalated graphite in the three is 4.5-5.5%;

[0006] The preparation method of the lithium titanate intercalated graphite is as follows: adding graphite to an ammonium sulfate aqueous solution with a mass fraction of 45-50%, then adding potassium permanganate and lithium titanate in sequence, stirring in a constant temperature water bath for 60 minutes, first washing with water and then soaking for 2-3 hours until the pH value is 6.0-7.0, filtering, drying in an oven at 60-70°C, and then calcining and expanding in a muffle furnace at 550-600°C to obtain the lithium titanate intercalated graphite;

[0007] The positive active slurry further includes a positive active material, the negative active slurry further includes a negative active material, and the electrolyte slurry further includes an electrolyte active material.

[0008] Furthermore, in the preparation of the lithium titanate intercalated graphite, the mass ratio of graphite, potassium permanganate, aqueous ammonium sulfate solution and lithium titanate is 1:(0.4-0.6):(3.0-3.5):(0.32-0.36).

[0009] Furthermore, the temperature of the constant temperature water bath is 40-50°C.

[0010] Furthermore, the binder includes polyvinylidene fluoride and / or sodium carboxymethyl cellulose.

[0011] Furthermore, the conductive agent includes carbon black.

[0012] Furthermore, the positive current collector is aluminum foil, and the negative current collector is copper foil.

[0013] Furthermore, the positive active material includes one of lithium cobalt oxide, lithium manganese oxide, and lithium nickel oxide, or a mixture of at least two of them.

[0014] Furthermore, the negative active material includes silicon carbon.

[0015] Furthermore, the electrolyte active material includes β-aluminum oxide and lithium tetrafluoroborate, and the mass ratio of the two is 2:(1-2).

[0016] In a second aspect, the present invention provides a method for manufacturing the above-mentioned all-solid-state battery, comprising the following steps:

[0017] S1, preparing positive active slurry;

[0018] 4.5-5.5% of lithium titanate intercalated graphite, 40-47% of positive active material, 4-5% of binder, 2-3% of conductive agent and the remainder of solvent are uniformly dispersed by mass to obtain positive active slurry;

[0019] S2, preparing negative active slurry;

[0020] 4.5-5.5% of lithium titanate intercalated graphite, 37-40% of negative active material, 4-5% of binder, 2-3% of conductive agent and the rest of solvent are uniformly dispersed by mass to obtain negative active slurry;

[0021] S3, preparing electrolyte slurry;

[0022] By mass percentage, 4.5-5.5% of lithium titanate intercalated graphite, 32-36% of electrolyte active material, 9-11% of binder, 0.5-1% of conductive agent and the remainder of solvent are uniformly dispersed to obtain electrolyte slurry;

[0023] S4, preparing a battery cell;

[0024] Coat the negative active slurry on the negative current collector with a surface loading of 20-30 mg / cm 2 , baked to semi-dry state, and coated with electrolyte slurry on its surface, with a surface loading of 10-15 mg / cm 2 , baked to semi-dry state, and coated with positive active slurry on its surface, with a surface loading of 20-30mg / cm 2 , cover the positive current collector on its surface, and pressurize the surface with a pressure of 400-700N / m 2 , heat treatment at 80-100℃ in an oven in an inert environment for 12-15h to obtain a battery cell;

[0025] S5, packaging;

[0026] The battery cell is encapsulated with an aluminum-plastic film and sealed by exhausting and compacting in a vacuum environment to obtain an all-solid-state battery.

[0027] This application has the following beneficial effects:

[0028] 1. The positive active slurry, negative active slurry and electrolyte slurry used in the preparation of the all-solid-state battery of the present invention all include lithium titanate intercalation graphite. On the one hand, the lithium titanate intercalation graphite can improve the interface contact between the positive and negative electrodes and the solid electrolyte, reduce the interface impedance, weaken the transmission resistance of lithium ions in the electrochemical reaction process, weaken the capacity decay rate, and extend the cycle life of the all-solid-state battery; on the other hand, the lithium titanate intercalation graphite itself has excellent structural stability and can maintain its crystal structure without significant changes during the insertion and extraction of lithium ions. This characteristic helps to reduce the volume expansion and contraction of the battery during the charge and discharge cycle, thereby extending the service life of the battery.

[0029] 2. In the preparation of lithium titanate intercalated graphite, the use of 45-50% ammonium sulfate aqueous solution is conducive to the expansion volume of expanded graphite reaching a large degree required by the present invention; lithium titanate itself has good chemical stability, and lithium titanate has good hydrophilicity and oleophobicity, and can form a uniform film on the surface of the electrode material, reducing the direct contact between the electrode and the electrolyte, thereby reducing the interface impedance, and there is a large interlayer spacing and a weak interlayer interaction force in the lithium titanate crystal structure. This characteristic enables it to deform to a certain extent when subjected to external force, thereby showing a certain elasticity; sufficient lithium titanate inserted into expanded graphite with sufficient expansion volume can provide sufficient chemical stability, structural support and elasticity, which can not only reduce the capacity decay of the battery during the cycle process, but also reduce the interface impedance, and can also effectively prevent deformation or rupture during the battery charging and discharging process, the effect is synergistic, and the service life of the battery is significantly extended. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 , one of the comparative trend graphs of the capacity retention rate test data of the all-solid-state batteries obtained by Examples 1-5 of the present invention and Comparative Examples 1-6 after 100, 200 and 300 cycles;

[0031] Figure 2 2. The second comparison trend graph of the capacity retention rate test data of all-solid-state batteries obtained from Examples 1-5 of the present invention and Comparative Examples 1-6 after 100, 200 and 300 cycles. DETAILED DESCRIPTION

[0032] The present application is further described in detail below with reference to the embodiments.

[0033] Unless otherwise specified, the raw materials used in the examples and comparative examples of the present application are all commercially available.

[0034] Example 1: (1) Preparation of lithium titanate intercalated graphite, the preparation method of which is as follows: adding graphite to an aqueous solution of ammonium sulfate with a mass fraction of 48%, then adding potassium permanganate and lithium titanate in sequence, stirring for 60 minutes at a stirring speed of 220 r / min in a constant temperature water bath at 45°C, first washing with water and then soaking for 2.5 hours to a pH value of 6.8, filtering, drying in an oven at 65°C for 2 hours, and then calcining and expanding in a muffle furnace at 580°C for 1 hour to obtain lithium titanate intercalated graphite.

[0035] Among them, the mass ratio of graphite, potassium permanganate, ammonium sulfate aqueous solution and lithium titanate is 1:0.5:3.2:0.35.

[0036] The graphite is 50 mesh flake graphite (fixed carbon content ≥ 99%, flake size 0.2 mm) purchased from Qingdao Risheng Graphite Co., Ltd. Potassium permanganate (reagent grade analytical pure) purchased from Guangdong Xiaoda Chemical Co., Ltd. The 48% mass fraction of ammonium sulfate aqueous solution is prepared by dissolving ammonium sulfate in water, and the ammonium sulfate is purchased from Henan Qida Chemical Raw Materials Co., Ltd. Lithium titanate (99%) is directly purchased from Hubei Jusheng Technology Co., Ltd.

[0037] (2) Prepare an all-solid-state battery, the preparation method of which is as follows:

[0038] S1, preparing positive active slurry;

[0039] Calculated by mass percentage, 5% of lithium titanate intercalated graphite, 45% of positive active material lithium cobaltate, 4.5% of binder polyvinylidene fluoride, 2.5% of conductive agent carbon black and 43% of solvent N-methylpyrrolidone are evenly dispersed to obtain a positive active slurry.

[0040] Specifically, lithium titanate intercalated graphite, lithium cobaltate, polyvinylidene fluoride and carbon black are gradually added to N-methylpyrrolidone, stirred using a disperser, and stirred at 350r / min for 30min to fully wet the solid powder and form a uniform slurry. Then, the slurry is transferred to a ball mill, and the slurry is ball milled using a ball mill to ensure that all components are evenly dispersed in the solvent to avoid agglomeration. The dispersed slurry is subjected to vacuum degassing treatment to remove bubbles in the slurry and ensure the uniformity and stability of the slurry, thereby obtaining a positive active slurry.

[0041] Among them, lithium cobalt oxide (content 98%) was purchased from Henan Shuangjie Chemical Co., Ltd. Polyvinylidene fluoride (US Solvay 6008) was purchased from Shanghai Henghangmai Plastics Co., Ltd. Carbon black is conductive carbon black XC72 (CABOT), purchased from Tianjin Tianyi Century Chemical Products Technology Development Co., Ltd. N-methylpyrrolidone (content 99.9%) was purchased from Jinan Xinke Chemical Co., Ltd.

[0042] S2, preparing negative active slurry;

[0043] Calculated by mass percentage, 5% of lithium titanate intercalated graphite, 38% of negative active material silicon carbon, 4.5% of binder polyvinylidene fluoride, 2.5% of conductive agent carbon black and 50% of solvent N-methylpyrrolidone are evenly dispersed to obtain negative active slurry.

[0044] Among them, silicon carbon is purchased from Fujian Xinsen Carbon Industry Co., Ltd.

[0045] S3, preparing electrolyte slurry;

[0046] By mass percentage, 5% of lithium titanate intercalated graphite, 35% of electrolyte active material, 10% of binder polyvinylidene fluoride, 0.8% of conductive agent carbon black and 49.2% of solvent N-methylpyrrolidone are evenly dispersed to obtain electrolyte slurry.

[0047] The electrolyte active materials include β-alumina and lithium tetrafluoroborate, and the mass ratio of the two is 2:1.5.

[0048] β-alumina was obtained by self-production: 0.5g of graphene oxide slurry was ultrasonically dispersed in 500ml of water, and then 52g of aluminum nitrate nonahydrate and 22g of sodium sulfate were added. After continuous ultrasonic dispersion, stirring was continued at 200°C for 3.5h, and then filtered, vacuum dried at 60°C for 5h, and then ground into powder, and calcined at 600°C for 2.5h to obtain β-alumina. Among them, graphene oxide slurry (KYHLGOW-2) was purchased from Sichuan Kenye Technology Development Co., Ltd. Aluminum nitrate nonahydrate was purchased from Beijing Huaye Huanyu Chemical Co., Ltd. Sodium sulfate (content 99%) was purchased from Shandong Lujiu Chemical Co., Ltd.

[0049] Lithium tetrafluoroborate (content 99.9%) was purchased from Jinan Yunuo Chemical Co., Ltd.

[0050] S4, preparing a battery cell;

[0051] The negative active slurry was evenly coated on the negative current collector copper foil (thickness 8 μm) with a surface loading of 26 mg / cm 2 , baked to semi-dry state, and evenly coated with electrolyte slurry on its surface, with a surface loading of 12 mg / cm 2 , baked to semi-dry state, and evenly coated with positive active slurry on its surface, with a surface loading of 25mg / cm 2 The positive current collector aluminum foil (thickness 8 μm) was covered on its surface and the surface was pressurized at a pressure of 550 N / m 2 , and heat treated at 90°C in an oven in an inert (argon) environment for 14 hours to obtain a battery cell.

[0052] S5, packaging;

[0053] The battery cell is encapsulated with an aluminum-plastic film and sealed by exhausting and compacting in a vacuum environment to obtain an all-solid-state battery.

[0054] Example 2: The difference between this example and Example 1 is that: (1) lithium titanate intercalated graphite is prepared by the following preparation method: graphite is added to a 45% by mass aqueous solution of ammonium sulfate, followed by the addition of potassium permanganate and lithium titanate, stirred in a constant temperature water bath at 40°C for 60 min, then washed with water and then soaked for 2 h to a pH value of 6.6, filtered, dried in an oven at 60°C for 2.5 h, and then calcined and expanded in a muffle furnace at 550°C for 1 h to obtain lithium titanate intercalated graphite.

[0055] Among them, the mass ratio of graphite, potassium permanganate, ammonium sulfate aqueous solution and lithium titanate is 1:0.4:3.5:0.32.

[0056] Example 3: The difference between this example and Example 1 is that: (1) lithium titanate intercalated graphite is prepared by the following preparation method: graphite is added to a 50% by mass aqueous solution of ammonium sulfate, followed by the addition of potassium permanganate and lithium titanate, stirred in a constant temperature water bath at 50°C for 60 min, then washed with water and then soaked for 3 h to a pH value of 6.9, filtered, dried in an oven at 70°C for 2 h, and then calcined and expanded in a muffle furnace at 600°C for 1 h to obtain lithium titanate intercalated graphite.

[0057] Among them, the mass ratio of graphite, potassium permanganate, ammonium sulfate aqueous solution and lithium titanate is 1:0.6:3.0:0.36.

[0058] Example 4: The difference between this example and Example 1 is that: (2) an all-solid-state battery is prepared, and the preparation method thereof is as follows:

[0059] S1, preparing positive active slurry;

[0060] Calculated by mass percentage, 4.5% of lithium titanate intercalated graphite, 40% of positive active material lithium cobaltate, 4% of binder polyvinylidene fluoride, 2% of conductive agent carbon black and 49.5% of solvent N-methylpyrrolidone are evenly dispersed to obtain a positive active slurry.

[0061] S2, preparing negative active slurry;

[0062] Calculated by mass percentage, 4.5% of lithium titanate intercalated graphite, 37% of negative active material silicon carbon, 4% of binder polyvinylidene fluoride, 2% of conductive agent carbon black and 52.5% of solvent N-methylpyrrolidone are evenly dispersed to obtain a negative active slurry.

[0063] S3, preparing electrolyte slurry;

[0064] By mass percentage, 4.5% of lithium titanate intercalated graphite, 32% of electrolyte active material, 9% of binder polyvinylidene fluoride, 0.5% of conductive agent carbon black and 54% of solvent N-methylpyrrolidone are uniformly dispersed to obtain electrolyte slurry.

[0065] The electrolyte active material includes β-alumina and lithium tetrafluoroborate, and the mass ratio of the two is 2:1.

[0066] S4, preparing a battery cell;

[0067] The negative active slurry was evenly coated on the negative current collector copper foil (thickness 8 μm) with a surface loading of 30 mg / cm 2 , baked to semi-dry state, and evenly coated with electrolyte slurry on its surface, with a surface loading of 15 mg / cm 2 , baked to semi-dry state, and evenly coated with positive active slurry on its surface, with a surface loading of 30mg / cm 2 The positive current collector aluminum foil (thickness 8 μm) was covered on its surface and the surface was pressurized to a pressure of 660 N / m 2 , and heat treated at 95°C in an inert (argon) oven environment for 14 hours to obtain a battery cell.

[0068] S5, packaging;

[0069] The battery cell is encapsulated with an aluminum-plastic film and sealed by exhausting and compacting in a vacuum environment to obtain an all-solid-state battery.

[0070] Example 5: The difference between this example and Example 1 is that: (2) an all-solid-state battery is prepared, and the preparation method thereof is as follows:

[0071] S1, preparing positive active slurry;

[0072] Calculated by mass percentage, 5.5% of lithium titanate intercalated graphite, 47% of positive active material lithium cobaltate, 5% of binder polyvinylidene fluoride, 3% of conductive agent carbon black and 39.5% of solvent N-methylpyrrolidone are evenly dispersed to obtain a positive active slurry.

[0073] S2, preparing negative active slurry;

[0074] Calculated by mass percentage, 5.5% of lithium titanate intercalated graphite, 40% of negative active material silicon carbon, 5% of binder polyvinylidene fluoride, 3% of conductive agent carbon black and 46.5% of solvent N-methylpyrrolidone are evenly dispersed to obtain negative active slurry.

[0075] S3, preparing electrolyte slurry;

[0076] By mass percentage, 5.5% of lithium titanate intercalated graphite, 36% of electrolyte active material, 11% of binder polyvinylidene fluoride, 1% of conductive agent carbon black and 46.5% of solvent N-methylpyrrolidone are evenly dispersed to obtain electrolyte slurry.

[0077] The electrolyte active material includes β-alumina and lithium tetrafluoroborate, and the mass ratio of the two is 1:1.

[0078] S4, preparing a battery cell;

[0079] The negative active slurry was evenly coated on the negative current collector copper foil (thickness 8 μm) with a surface loading of 20 mg / cm 2 , baked to semi-dry state, and evenly coated with electrolyte slurry on its surface, with a surface loading of 10 mg / cm 2 , baked to semi-dry state, and evenly coated with positive active slurry on its surface, with a surface loading of 20mg / cm 2 The positive current collector aluminum foil (thickness 8 μm) was covered on its surface and the surface was pressurized at a pressure of 550 N / m 2 , and heat-treat at 80°C in an inert (argon) oven environment for 15 h to obtain a battery cell.

[0080] S5, packaging;

[0081] The battery cell is encapsulated with an aluminum-plastic film and sealed by exhausting and compacting in a vacuum environment to obtain an all-solid-state battery.

[0082] Comparative Example 1: The difference between this comparative example and Example 1 is that lithium titanate is deleted; that is, the lithium titanate intercalated graphite is replaced by expanded graphite (still using an ammonium sulfate aqueous solution with a mass fraction of 48%).

[0083] Specifically, the preparation method of expanded graphite is as follows: adding graphite to an aqueous solution of ammonium sulfate with a mass fraction of 48%, then adding potassium permanganate, stirring for 60 minutes at a stirring speed of 220r / min in a constant temperature water bath at 45°C, first washing with water and then soaking for 2.5 hours until the pH value is about 6.8, filtering, drying in an oven at 65°C for 2 hours, and then calcining in a muffle furnace at 580°C for 1 hour to obtain expanded graphite. The mass ratio of graphite, potassium permanganate, and aqueous solution of ammonium sulfate is 1:0.5:3.2.

[0084] Comparative Example 2: The difference between this comparative example and Example 1 is that lithium titanate is deleted and an aqueous solution of ammonium sulfate with a mass fraction of 30% is used; that is, the lithium titanate intercalated graphite is replaced by expanded graphite.

[0085] Specifically, the preparation method of expanded graphite is as follows: adding graphite to a 30% ammonium sulfate aqueous solution by mass, then adding potassium permanganate, stirring for 60 minutes at a stirring speed of 220r / min in a constant temperature water bath at 45°C, first washing with water and then soaking for 2.5 hours until the pH value is about 6.8, filtering, drying in an oven at 65°C for 2 hours, and then calcining in a muffle furnace at 580°C for 1 hour to obtain expanded graphite. Among them, the mass ratio of graphite, potassium permanganate, and ammonium sulfate aqueous solution is 1:0.5:3.2.

[0086] Comparative Example 3: The difference between this comparative example and Example 1 is that in the preparation of lithium titanate intercalated graphite, an ammonium sulfate aqueous solution with a mass fraction of 30% is used.

[0087] Specifically, lithium titanate intercalated graphite is prepared by the following method: adding graphite to a 30% ammonium sulfate aqueous solution by mass, then adding potassium permanganate and lithium titanate in sequence, stirring for 60 minutes at a stirring speed of 220r / min in a constant temperature water bath at 45°C, first washing with water and then soaking for 2.5 hours until the pH value is 6.8, filtering, drying in an oven at 65°C for 2 hours, and then calcining and expanding in a muffle furnace at 580°C for 1 hour to obtain lithium titanate intercalated graphite. The mass ratio of graphite, potassium permanganate, ammonium sulfate aqueous solution and lithium titanate is 1:0.5:3.2:0.35.

[0088] Comparative Example 4: The difference between this comparative example and Example 1 is that in the preparation of the all-solid-state battery, the lithium titanate intercalated graphite is deleted.

[0089] Specifically, an all-solid-state battery is prepared, and the preparation method thereof is as follows:

[0090] S1, preparing positive active slurry;

[0091] Calculated by mass percentage, 47% of lithium cobalt oxide as a positive active material, 5% of polyvinylidene fluoride as a binder, 3% of carbon black as a conductive agent and 45% of N-methylpyrrolidone as a solvent are uniformly dispersed to obtain a positive active slurry.

[0092] S2, preparing negative active slurry;

[0093] Calculated by mass percentage, 40% of negative active material silicon carbon, 5% of binder polyvinylidene fluoride, 3% of conductive agent carbon black and 52% of solvent N-methylpyrrolidone are evenly dispersed to obtain negative active slurry.

[0094] S3, preparing electrolyte slurry;

[0095] By mass percentage, 36% of electrolyte active material, 11% of binder polyvinylidene fluoride, 1% of conductive agent carbon black and 52% of solvent N-methylpyrrolidone are uniformly dispersed to obtain electrolyte slurry. The electrolyte active material includes β-alumina and lithium tetrafluoroborate, and the mass ratio of the two is 1:1.

[0096] S4, preparing a battery cell;

[0097] The negative active slurry was evenly coated on the negative current collector copper foil (thickness 8 μm) with a surface loading of 20 mg / cm 2 , baked to semi-dry state, and evenly coated with electrolyte slurry on its surface, with a surface loading of 10 mg / cm 2 , baked to semi-dry state, and evenly coated with positive active slurry on its surface, with a surface loading of 20mg / cm 2 The positive current collector aluminum foil (thickness 8 μm) was covered on its surface and the surface was pressurized at a pressure of 550 N / m 2 , and heat-treat at 80°C in an inert (argon) oven environment for 15 h to obtain a battery cell.

[0098] S5, packaging;

[0099] The battery cell is encapsulated with an aluminum-plastic film and sealed by exhausting and compacting in a vacuum environment to obtain an all-solid-state battery.

[0100] Comparative Example 5: The difference between this comparative example and Example 1 is that in the preparation of the all-solid-state battery, β-alumina is replaced by commercially available α-alumina (purchased from Hangzhou Jikang New Materials Co., Ltd.).

[0101] Comparative Example 6: The difference between this comparative example and Example 1 is that in the preparation of the all-solid-state battery, the lithium titanate intercalated graphite is deleted, and the β-alumina is replaced by commercially available α-alumina.

[0102] Test example: Test object: Batteries were prepared according to Examples 1-5 and Comparative Examples 1-6.

[0103] Test content: At 25°C, charge the battery to 100% SOC at a charge rate of 0.33C, let it stand for 100s, then discharge it to 0% SOC at 0.33C and let it stand for 100s. After n cycles, record the discharge capacity of the first week as C1, and the discharge capacity of the nth week as Cn. Then, the capacity retention rate after n cycles = (Cn / C1)×100%.

[0104] Test results: See Table 1.

[0105] Table 1. Test data of the experimental example

[0106]

[0107]

[0108] Result analysis: Analyze examples 1-5 and combine the data in Table 1 and Figure 1-2 It can be seen that the capacity decay rate of the all-solid-state battery prepared by the present invention is slow, the cycle service life is long, the capacity retention rate after 100 cycles is as high as over 95.8%, the capacity retention rate after 200 cycles is as high as over 91.5%, and the capacity retention rate after 300 cycles is as high as over 86.9%.

[0109] Analyze Example 1 and Comparative Examples 1-4 and combine the data in Table 1 and Figure 1-2 By comparing Comparative Example 4 with Comparative Example 2, it can be seen that the capacity retention rate of the all-solid-state battery prepared in Comparative Example 2 after 100, 200 and 300 cycles is greater than that of Comparative Example 4, indicating that using the expanded graphite prepared using an aqueous solution of ammonium sulfate with a mass fraction of 30% to prepare an all-solid-state battery can reduce the capacity attenuation rate of the all-solid-state battery and extend the cycle service life of the all-solid-state battery.

[0110] By comparing Comparative Example 4 with Comparative Example 1, it can be seen that the capacity retention rate of the all-solid-state battery prepared in Comparative Example 1 after 100, 200 and 300 cycles is lower than that of Comparative Example 4, indicating that using expanded graphite prepared using an aqueous solution of ammonium sulfate with a mass fraction of 48% for the preparation of an all-solid-state battery will lead to an accelerated capacity decay rate of the all-solid-state battery, resulting in a shortened cycle life of the all-solid-state battery.

[0111] From the comparison between Comparative Example 2 and Comparative Example 3 and between Comparative Example 1 and Example 1, it can be seen that the capacity retention rates of the all-solid-state battery obtained in Comparative Example 3 after 100, 200 and 300 cycles are greater than those of Comparative Example 2, and the capacity retention rates of the all-solid-state battery obtained in Example 1 after 100, 200 and 300 cycles are greater than those of Comparative Example 1, indicating that lithium titanate intercalated graphite obtained by inserting lithium titanate into expanded graphite is used to prepare all-solid-state batteries, which can reduce the capacity decay rate of the all-solid-state batteries and extend the cycle life of the all-solid-state batteries.

[0112] By comparing Comparative Example 3 with Example 1, it can be seen that the capacity retention rate of the all-solid-state battery prepared in Example 1 after 100, 200 and 300 cycles is greater than that of Comparative Example 3, indicating that the effect of inserting lithium titanate into the expanded graphite prepared using an aqueous solution of ammonium sulfate having a mass fraction of 48% on the cycle life of the prepared all-solid-state battery is to stop falling and rebound, and the increase is greater than that of inserting lithium titanate into the expanded graphite prepared using an aqueous solution of ammonium sulfate having a mass fraction of 30%.

[0113] Analyze Example 1 and Comparative Examples 4-6 and combine the data in Table 1 and Figure 1-2 It can be seen that the use of lithium titanate intercalated graphite is beneficial to reducing the capacity decay rate of the all-solid-state battery and extending the cycle service life of the all-solid-state battery; the addition of β-alumina in the solid electrolyte is also beneficial to reducing the capacity decay rate of the all-solid-state battery and extending the cycle service life of the all-solid-state battery; and there is a synergistic effect between the two, which can work synergistically to synergistically reduce the capacity decay rate of the all-solid-state battery.

[0114] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0115] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. An all-solid-state battery, comprising a positive electrode, a negative electrode and a solid electrolyte, wherein the positive electrode comprises a positive current collector and a positive active slurry disposed on the positive current collector, the negative electrode comprises a negative current collector and a negative active slurry disposed on the negative current collector, and the solid electrolyte is made of an electrolyte slurry, characterized in that: The positive active slurry, the negative active slurry and the electrolyte slurry all include lithium titanate intercalated graphite, a binder, a conductive agent and a solvent, and the mass proportion of the lithium titanate intercalated graphite in the three is 4.5-5.5%; The preparation method of the lithium titanate intercalated graphite is as follows: adding graphite to an ammonium sulfate aqueous solution with a mass fraction of 45-50%, then adding potassium permanganate and lithium titanate in sequence, stirring in a constant temperature water bath for 60 minutes, first washing with water and then soaking for 2-3 hours until the pH value is 6.0-7.0, filtering, drying in an oven at 60-70°C, and then calcining and expanding in a muffle furnace at 550-600°C to obtain the lithium titanate intercalated graphite; The positive active slurry further includes a positive active material, the negative active slurry further includes a negative active material, and the electrolyte slurry further includes an electrolyte active material.

2. The all-solid-state battery according to claim 1, characterized in that: In the preparation of the lithium titanate intercalated graphite, the mass ratio of graphite, potassium permanganate, aqueous ammonium sulfate solution and lithium titanate is 1:(0.4-0.6):(3.0-3.5):(0.32-0.36).

3. The all-solid-state battery according to claim 1, characterized in that: The temperature of the constant temperature water bath is 40-50°C.

4. The all-solid-state battery according to claim 1, characterized in that: The binder includes polyvinylidene fluoride and / or sodium carboxymethyl cellulose.

5. The all-solid-state battery according to claim 1, characterized in that: The conductive agent includes carbon black.

6. The all-solid-state battery according to claim 1, characterized in that: The positive current collector is aluminum foil, and the negative current collector is copper foil.

7. The all-solid-state battery according to claim 1, characterized in that: The positive active material includes one of lithium cobalt oxide, lithium manganese oxide, and lithium nickel oxide, or a mixture of at least two of them.

8. The all-solid-state battery according to claim 1, characterized in that: The negative active material includes silicon carbon.

9. The all-solid-state battery according to claim 1, characterized in that: The electrolyte active material includes β-aluminum oxide and lithium tetrafluoroborate, and the mass ratio of the two is 2:(1-2).

10. A method for manufacturing an all-solid-state battery according to any one of claims 1 to 9, characterized in that: The steps include: S1. By mass percentage, 4.5-5.5% of lithium titanate intercalated graphite, 40-47% of positive active material, 4-5% of binder, 2-3% of conductive agent and the remainder of solvent are uniformly dispersed to obtain a positive active slurry; S2. By mass percentage, 4.5-5.5% of lithium titanate intercalated graphite, 37-40% of negative active material, 4-5% of binder, 2-3% of conductive agent and the remainder of solvent are uniformly dispersed to obtain negative active slurry; S3, by mass percentage, 4.5-5.5% of lithium titanate intercalated graphite, 32-36% of electrolyte active material, 9-11% of binder, 0.5-1% of conductive agent and the remainder of solvent are uniformly dispersed to obtain electrolyte slurry; S4, coating the negative active slurry on the negative current collector, with a surface loading of 20-30 mg / cm 2 , baked to semi-dry state, and coated with electrolyte slurry on its surface, with a surface loading of 10-15 mg / cm 2 , baked to semi-dry state, and coated with positive active slurry on its surface, with a surface loading of 20-30mg / cm 2 , cover the positive current collector on its surface, and pressurize the surface with a pressure of 400-700N / m 2 , heat treatment at 80-100℃ in an oven in an inert environment for 12-15h to obtain a battery cell; S5. The battery cell is encapsulated with an aluminum-plastic film, and the vacuum environment is used to exhaust, compact and seal the battery to obtain an all-solid-state battery.

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