Solid-state lithium-ion battery and method for preparing the same

Abstract

Disclosed are a solid-state lithium-ion battery and a preparation method thereof. The battery includes a composite positive electrode sheet and a negative electrode sheet. The composite positive electrode sheet includes: a positive electrode current collector; a positive electrode active material layer disposed on the surface of the positive electrode current collector with a width and a thickness of D1 and L1 respectively; and a solid electrolyte layer disposed on the surface of the positive electrode active material layer with a width and a thickness of D2 and L2 respectively, and satisfying: D2 (μm) = D1 (μm) + 25000 / L2 (μm), and 10 μm ≤ L2 ≤ 100 μm. The solid-state lithium-ion battery of the present invention can effectively avoid internal short circuit caused by the contact between the positive and negative electrodes. In particular, the solid electrolyte layer with a certain ductility is suitable for existing production lines, can greatly save production costs, improve production efficiency at the same time, and is conducive to industrial application in the lamination process of all-solid-state batteries.

Description

Technical Field

[0001] The present invention relates to the field of lithium-ion batteries, and more particularly, to a solid-state lithium-ion battery and a method for preparing the same. Background Art

[0002] Lithium-ion batteries have been widely used in various fields such as electronic products, new energy vehicles, and energy storage due to their advantages of high energy density, long cycle life, small size, and environmental friendliness. For various applications, the volumetric energy density, fast charging ability, safety, and service life of lithium-ion batteries are the most critical performance indicators. Traditional lithium-ion batteries use liquid electrolytes containing flammable organic solvents, which have safety hazards such as heating and explosion. In recent years, all-solid-state lithium batteries have replaced organic electrolytes with solid electrolytes as ion conductors, making the products safer and having a longer service life.

[0003] A solid-state lithium-ion battery is composed of a positive and negative electrode layer and a solid electrolyte layer disposed therebetween, which are stacked and encapsulated. Since reducing the thickness of the solid electrolyte layer can improve the energy density of the battery, currently, all-solid-state battery systems tend to further reduce the thickness of this layer. However, the thinner the solid electrolyte layer, the more likely it is to have positive and negative extreme contacts during lamination and encapsulation, resulting in short circuits due to the smaller gap between the positive and negative electrode layers. In addition, the thinner the solid electrolyte layer, the more likely it is to rupture under external impact and vibration, leading to internal short circuits between the positive and negative electrodes of the battery.

[0004] Therefore, it is still necessary to further improve the structure of the electrode sheets of solid-state lithium-ion batteries and their preparation methods. While reducing the thickness of the solid electrolyte layer and improving the energy density of the battery, the occurrence of positive and negative contact short circuits is avoided or reduced, and the safety and reliability of battery products are further improved. Summary of the Invention

[0005] To solve the problem of positive and negative contact short circuits in the above-mentioned solid-state lithium-ion batteries, the applicant of the present application has conducted a large number of experiments and found that coating a solid electrolyte layer on the positive electrode active material layer to completely cover the positive electrode active material layer can avoid short circuits caused by direct contact between the positive electrode active material layer and the negative electrode active material layer. Among them, by selecting appropriate solid electrolytes and binders, and by adjusting the binder content, the solid electrolyte layer coated on the positive electrode active material layer has a certain ductility. Then, during the rolling / static pressing process of battery assembly, the coated solid electrolyte layer has a thinner thickness due to rolling, and at the same time, it extends beyond the periphery of the positive electrode active material layer due to rolling, so that the coated solid electrolyte layer covers the entire positive electrode active material layer, thereby preventing or reducing short circuits caused by direct positive and negative contact.

[0006] As an alternative, a solid electrolyte layer may also be coated on the negative electrode active material layer to completely cover the negative electrode active material layer, which can also avoid short circuit caused by direct contact between the positive electrode active material layer and the negative electrode active material layer.

[0007] Therefore, on the one hand, the present invention provides a solid-state lithium-ion battery, comprising a composite positive electrode sheet and a negative electrode sheet, wherein the composite positive electrode sheet includes:

[0008] A positive electrode current collector;

[0009] A positive electrode active material layer disposed on the surface of the positive electrode current collector with a width and a thickness of D1 and L1 respectively; and

[0010] A solid electrolyte layer disposed on the surface of the positive electrode active material layer with a width and a thickness of D2 and L2 respectively, and satisfying: D2 (μm) = D1 (μm) + 25000 / L2 (μm), and 10 μm ≤ L2 ≤ 100 μm.

[0011] On the other hand, the present invention provides a method for preparing the aforementioned solid-state lithium-ion battery, comprising the following steps:

[0012] (1) Forming a positive electrode active material layer with a width and a thickness of D1 and L1 respectively on the positive electrode current collector, and forming a solid electrolyte layer with a width and a thickness of D2 and L2 respectively on the surface of the positive electrode active material layer, such that D2 (μm) = D1 (μm) + 25000 / L2 (μm), and 10 μm ≤ L2 ≤ 100 μm, to obtain a composite positive electrode sheet;

[0013] (2) Preparing a negative electrode sheet; and

[0014] (3) Assembling the composite positive electrode sheet and the negative electrode sheet into the solid-state lithium-ion battery.

[0015] According to the present invention, by controlling the selection and content of the binder when preparing the positive electrode active material layer and the solid electrolyte layer, the obtained solid electrolyte layer has better ductility during subsequent rolling or static pressing in the lamination process. Thus, on the one hand, a thinner solid electrolyte layer can be obtained, improving the battery energy density; on the other hand, the rolling rate of the solid electrolyte layer is greater than that of the positive electrode active material layer, so that the outer periphery of the solid electrolyte layer can exceed the periphery of the positive electrode active material layer, effectively avoiding internal short circuit caused by direct contact between the positive electrode active material layer and the negative electrode.

[0016] In particular, the solid electrolyte layer with certain ductility is suitable for existing production lines, which can greatly save production costs, improve production efficiency at the same time, and is conducive to industrial application in the lamination process of all-solid-state batteries. Description of the Drawings

[0017] Figure 1Schematic diagram of a composite positive electrode of an all-solid-state lithium-ion battery according to the present invention, where the meanings of the reference numerals are as follows:

[0018] 1 - Current collector;

[0019] 2 - Positive electrode active material layer;

[0020] 3 - Solid electrolyte layer. Detailed implementation manners

[0021] The present application will be further described in detail below in conjunction with the accompanying drawings and embodiments. Through these descriptions, the features and advantages of the present application will become clearer and more definite.

[0022] In addition, the technical features involved in different implementation manners of the present application described below can be combined with each other as long as they do not conflict with each other.

[0023] Figure 1 Showing a composite positive electrode of an all-solid-state lithium-ion battery according to the present invention. In the figure, for the sake of illustration, a part of the positive electrode active material layer is deliberately exposed. In the actual composite positive electrode, the uppermost solid electrolyte film completely covers the positive electrode active material layer. Similarly, in the embodiment where a solid electrolyte film is coated on the negative electrode active material layer, only the Figure 1 positive electrode active material layer in it needs to be changed to a negative electrode active material layer, and at the same time, a negative electrode current collector can be used.

[0024] The all-solid-state lithium-ion battery according to the present invention includes a composite positive electrode sheet and a negative electrode sheet, where the composite positive electrode sheet includes:

[0025] Positive electrode current collector;

[0026] A positive electrode active material layer with a width and thickness of D1 and L1 respectively provided on the surface of the positive electrode current collector; and

[0027] A solid electrolyte layer with a width and thickness of D2 and L2 respectively provided on the surface of the positive electrode active material layer, and satisfying: D2 (μm) = D1 (μm) + 25000 / L2 (μm), and 10 μm ≤ L2 ≤ 100 μm.

[0028] In an embodiment of the all-solid-state lithium-ion battery according to the present invention, the positive electrode active material layer contains a positive electrode active material, a conductive agent, a first solid electrolyte, and a first binder, and by the mass of the positive electrode active material layer, the percentage content N1 of the first binder satisfies: 0.5 ≤ N1 ≤ 5; the solid electrolyte layer contains a second solid electrolyte and a second binder, and by the mass of the solid electrolyte layer, the percentage content N2 of the second binder satisfies: 0.55 ≤ N2 ≤ 5.5.

[0029] It should be noted that the percentage contents N1 and N2 described in this article refer to the values before the percent sign. For example, N1 = 0.5 represents a percentage content of 0.5%, and N2 = 5 represents a percentage content of 5%, and so on.

[0030] In another embodiment of the solid-state lithium-ion battery according to the present invention, 0.05 ≤ N2 - N1 ≤ 5.

[0031] In another embodiment of the solid-state lithium-ion battery according to the present invention, the positive electrode active material is selected from LiCoO2; LiMn x O2, where x = 1 or 2; LiNi 1-x Mn x O2, 0 < x < 1; LiNi 1-x-y Co x Mn y O2, 0 ≤ x ≤ 0.5, 0 ≤ y ≤ 0.5; LiFePO4; and one or more of sulfur-containing composite positive electrode active materials.

[0032] In another embodiment of the solid-state lithium-ion battery according to the present invention, the first solid electrolyte and the second solid electrolyte are each independently one or more selected from the following: perovskite-type solid electrolytes; NASICON-type solid electrolytes; LISICON-type solid electrolytes; garnet-type oxide solid electrolytes; vitreous Li2S - P2S5; crystalline Li x M y PS z , where M is one or more selected from Si, Ge, Sn, x + 4y + 5 = 2z, 0 ≤ y ≤ 1; glass-ceramic Li2S - P2S5; and Li 6-y PS 5-y X y , where X is one or more of Cl, Br, I, 0 ≤ y ≤ 1.8.

[0033] In another embodiment of the solid-state lithium-ion battery according to the present invention, the first solid electrolyte and the second solid electrolyte are each independently one or more selected from Li6PS5Cl and Li 5.5 PS 4.5 Cl 1.5 among others.

[0034] In another embodiment of the solid-state lithium-ion battery according to the present invention, the first binder and the second binder are each independently one or more selected from styrene-butadiene rubber (SBR), nitrile butadiene rubber (NBR), hydrogenated styrene-butadiene rubber, hydrogenated nitrile butadiene rubber, sodium carboxymethyl cellulose (CMC), polyacrylic acid (PAA), polyacrylonitrile (PAN), polyimide (PI), polyvinylidene fluoride (PVDF), preferably hydrogenated styrene-butadiene rubber; the conductive agent is one or more selected from carbon black conductive agent, graphite conductive agent and graphene conductive agent, wherein the carbon black conductive agent includes acetylene black, 350G, carbon fiber (VGCF), carbon nanotube (CNT), Ketjen black or a combination thereof, the graphite conductive agent includes KS-6, KS-15, SFG-6, SFG-15 or a combination thereof, and the graphene conductive agent includes single-layer, multi-layer graphene or a combination thereof.

[0035] In another embodiment of the solid-state lithium-ion battery according to the present invention, the negative electrode sheet contains one or more negative electrode active materials selected from the following: artificial graphite, natural graphite, silicon monoxide, silicon carbide, ferrosilicon alloy, mesophase carbon microspheres, nano-silicon, lithium metal or lithium alloy, preferably artificial graphite, natural graphite, silicon carbide or lithium alloy.

[0036] On the other hand, the present invention also provides a method for preparing a solid-state lithium-ion battery according to the foregoing embodiments, including the following steps:

[0037] (1) Form a positive electrode active material layer with a width and thickness of D1 and L1 respectively on the positive electrode current collector, and form a solid electrolyte layer with a width and thickness of D2 and L2 respectively on the surface of the positive electrode active material layer, such that D2 (μm) = D1 (μm) + 25000 / L2 (μm), and 10 μm ≤ L2 ≤ 100 μm, to obtain a composite positive electrode sheet;

[0038] (2) Prepare a negative electrode sheet; and

[0039] (3) Assemble the composite positive electrode sheet and the negative electrode sheet into the solid-state lithium-ion battery.

[0040] According to an embodiment of the method for preparing a solid-state lithium-ion battery of the present invention, in the formation of the positive electrode active material layer, the positive electrode active material, the conductive agent, the first solid electrolyte and the first binder are mixed, such that by the mass of the positive electrode active material layer, the percentage content N1 of the first binder satisfies: 0.5 ≤ N1 ≤ 5; in the formation of the solid electrolyte layer, the second solid electrolyte and the second binder are mixed, such that by the mass of the solid electrolyte layer, the percentage content N2 of the second binder satisfies: 0.55 ≤ N2 ≤ 5.5.

[0041] In another embodiment of the method for preparing a solid-state lithium-ion battery according to the present invention, the first binder and the second binder are each independently one or more selected from styrene-butadiene rubber (SBR), nitrile butadiene rubber (NBR), hydrogenated styrene-butadiene rubber, hydrogenated nitrile butadiene rubber, sodium carboxymethyl cellulose (CMC), polyacrylic acid (PAA), polyacrylonitrile (PAN), polyimide (PI), and polyvinylidene fluoride (PVDF), preferably hydrogenated styrene-butadiene rubber; the conductive agent is one or more selected from carbon black conductive agents, graphite conductive agents, and graphene conductive agents. The carbon black conductive agent includes acetylene black, 350G, vapor grown carbon fiber (VGCF), carbon nanotube (CNT), Ketjen black, or a combination thereof. The graphite conductive agent includes KS-6, KS-15, SFG-6, SFG-15, or a combination thereof. The graphene conductive agent includes single-layer, multi-layer graphene, or a combination thereof.

[0042] In another embodiment of the method for preparing a solid-state lithium-ion battery according to the present invention, it is preferred that the first binder and the second binder are the same binder, more preferably they are styrene-butadiene rubber (SBR), nitrile butadiene rubber (NBR), hydrogenated styrene-butadiene rubber, or hydrogenated nitrile butadiene rubber, and most preferably hydrogenated styrene-butadiene rubber.

[0043] In another embodiment of the method for preparing a solid-state lithium-ion battery according to the present invention, 0.05 ≤ N2 - N1 ≤ 5.

[0044] In another embodiment of the method for preparing a solid-state lithium-ion battery according to the present invention, the particle sizes of the first or second solid electrolyte are each independently 0.5 - 5 μm, preferably 0.5 - 3 μm, and more preferably 1 - 3 μm.

[0045] More specifically, when forming the positive electrode active material layer on the positive electrode current collector, the positive electrode active material, the conductive agent, the first solid electrolyte, and the first binder are mixed, and then a solvent is added to prepare a positive electrode active material layer slurry, which is coated on the current collector; wherein the first solid electrolyte, the positive electrode active material, the conductive agent, and the first binder can be mixed in a mass ratio of 5 - 60:45 - 99:1 - 10:1 - 10, preferably 5 - 45:55 - 95:1 - 5:1 - 5.

[0046] More specifically, when forming the solid electrolyte layer on the surface of the positive electrode active material layer, the second solid electrolyte and the second binder are mixed, and then a solvent is added to prepare a solid electrolyte layer slurry, which is coated on the positive electrode active material layer; wherein the second solid electrolyte and the second binder are mixed in a mass ratio of 90 - 99:1 - 10, preferably 90 - 95:1 - 5.

[0047] In another embodiment of the method for preparing a solid-state lithium-ion battery according to the present invention, when forming the positive electrode active material layer and the solid electrolyte layer, the solvents used are preferably each independently a non-polar solvent, such as n-hexane, butyl butyrate, n-heptane, xylene, preferably xylene.

[0048] In another embodiment of the method for preparing a solid-state lithium-ion battery according to the present invention, when forming the positive electrode active material layer and the solid electrolyte layer, the solid contents of the positive electrode active material layer slurry and the solid electrolyte layer slurry are each independently 20% to 60 wt%, preferably 30 to 55 wt%.

[0049] In another embodiment of the method for preparing a solid-state lithium-ion battery according to the present invention, the coating thickness of the positive electrode active material layer is 10 to 150 μm, preferably 50 to 120 μm.

[0050] In another embodiment of the method for preparing a solid-state lithium-ion battery according to the present invention, the coating thickness of the solid electrolyte layer is 10 to 100 μm, preferably 20 to 80 μm, more preferably 25 to 45 μm.

[0051] In addition, in the present invention, the current collector can be, for example, aluminum foil.

[0052] It should be noted that in the foregoing embodiments of the present invention, the solid electrolyte layer is formed on the positive electrode active material layer, mainly considering that the area of the active material layer of the positive electrode in the battery cell is generally smaller than that of the active material layer of the negative electrode. Therefore, forming the solid electrolyte layer on the positive electrode active material layer is more conducive to cost savings. Those skilled in the art can understand that by adopting a similar method, the solid electrolyte layer can be formed on the negative electrode active material layer, and it is also possible to avoid short circuit between the positive and negative electrodes.

[0053] The method for preparing a solid-state lithium-ion battery according to the present invention controls the content of the binder in the positive electrode active material layer and the solid electrolyte layer, such that the rolling ratio of the solid electrolyte layer is greater than that of the positive electrode active material layer. When the composite positive electrode undergoes roll pressing / static pressing in the lamination process under a pressure of 10 to 600 MPa, preferably 50 to 450 MPa, the solid electrolyte layer not only has good rollability, enabling a thinner solid electrolyte layer to be obtained, which is beneficial to improving the energy density of the battery; at the same time, due to the larger rolling ratio of the solid electrolyte layer, the outer periphery of the solid electrolyte layer can exceed the periphery of the positive electrode active material layer, completely covering the positive electrode active material layer, thereby effectively avoiding the occurrence of positive-negative contact short circuit. Additionally, according to the present invention, in accordance with the thickness-width relationship in the formula D2 = D1 + 25000 / L2, when the thickness L2 of the solid electrolyte layer is thinner, the width D2 after rolling is larger, that is, its outer periphery extends beyond the periphery of the positive / negative electrode active material layer more, so that better protection can be obtained when the thickness of the solid electrolyte layer is thinner to avoid positive-negative contact short circuit.

[0054] The present invention will be further described below through examples.

[0055] Example 1

[0056] Weigh 8 g of NCM562, 1.5 g of solid electrolyte Li6PS5Cl, 0.2 g of styrene-butadiene rubber, and 0.3 g of conductive agent SP, add them to a ball mill jar, and ball mill at a speed of 200 rpm for 30 min. Subsequently, place the ball-milled and mixed powder in a 100 mL slurry mixing jar, add xylene to it to make the solid-liquid ratio 50%, and slurry for a total of 5 min to obtain a uniform slurry for the positive electrode active material layer. Then, using the blade coating method, uniformly coat the obtained slurry for the positive electrode active material layer on the surface of the current collector aluminum foil with a coating thickness of 80 μm, and then place it in a vacuum drying oven at 60 °C for 48 h for drying.

[0057] Weigh 9.5 g of Li 5.5 PS 4.5 Cl 1.5 and 0.5 g of styrene-butadiene rubber, mix them evenly, add them to a ball mill jar, and ball mill at a speed of 200 rpm for 30 min. Subsequently, place the ball-milled and mixed powder in a 100 mL slurry mixing jar, add xylene to it to make the solid-liquid ratio 50%, and slurry for a total of 5 min to obtain a uniform slurry for the solid electrolyte. Then, using the blade coating method, uniformly coat the obtained slurry for the solid electrolyte on the surface of the above-mentioned electrode sheet coated with the positive electrode material with a coating thickness of 35 μm, and then place it in a vacuum drying oven at 60 °C for 12 h for drying to obtain a positive electrode material + solid electrolyte laminated composite electrode sheet according to the present invention.

[0058] Example 2

[0059] Weigh 8 g of NCM811, 1.6 g of solid electrolyte Li 5.5 PS 4.5 Cl 1.5 , 0.1 g of nitrile rubber, and 0.3 g of conductive agent Ketjenblack. Add them to a ball mill jar and ball mill at a speed of 300 rpm for 45 min. Then, place the ball-milled and mixed powder in a 100 mL slurry mixing jar, add xylene to it to make the solid-liquid ratio 50%, and slurry for a total of 5 min to obtain a uniform slurry of the positive electrode active material layer. Then, using the doctor blade coating method, uniformly scrape the slurry of the positive electrode active material layer onto the surface of the current collector aluminum foil with a coating thickness of 100 μm, and then place it in a vacuum drying oven at 45 °C for drying for 48 h.

[0060] Weigh 9.7 g of Li 5.4 PS 4.4 Cl 1.6 , 0.3 g of styrene-butadiene rubber, mix them evenly and add them to a ball mill jar, ball mill at a speed of 150 rpm for 15 min. Then, place the ball-milled and mixed powder in a 100 mL slurry mixing jar, add xylene to it to make the solid-liquid ratio 50%, and slurry for a total of 10 min to obtain a uniform solid electrolyte slurry. Then, using the doctor blade coating method, uniformly scrape the obtained solid electrolyte slurry onto the surface of the above-mentioned electrode sheet coated with the positive electrode material with a coating thickness of 45 μm, and then place it in a vacuum drying oven at 60 °C for drying for 24 h to obtain the positive electrode material + solid electrolyte laminated composite electrode sheet according to the present invention.

[0061] Example 3

[0062] Weigh 8 g of LiCoO2, 1.65 g of solid electrolyte Li 5.5 PS 4.5 Cl 1.5 , 0.5 g of hydrogenated styrene-butadiene rubber, 0.3 g of conductive agent SP, add them to a ball mill jar and ball mill at a speed of 450 rpm for 30 min. Then, place the ball-milled and mixed powder in a 100 mL slurry mixing jar, add xylene to it to make the solid-liquid ratio 50%, and slurry for a total of 5 min to obtain a uniform slurry of the positive electrode active material layer. Then, using the doctor blade coating method, uniformly scrape the slurry of the positive electrode active material layer onto the surface of the current collector aluminum foil with a coating thickness of 120 μm, and then place it in a vacuum drying oven at 60 °C for drying for 48 h.

[0063] Weigh 9.45 g of Li 5.5 PS 4.5 Cl 1.5, 0.55 g of hydrogenated styrene-butadiene rubber was added, mixed evenly and put into a ball mill jar, and ball milled at a speed of 100 rpm for 30 min. Subsequently, the ball milled and mixed powder was placed in a 100 mL slurry mixing jar, and xylene was added thereto to make the solid-liquid ratio 50%. The slurry mixing was carried out for a total of 5 min to obtain a uniform solid electrolyte slurry. Then, by means of blade coating, the obtained solid electrolyte slurry was evenly coated on the surface of the above-mentioned electrode sheet coated with the positive electrode material, with a coating thickness of 35 μm, and then placed in a vacuum drying oven at 60 °C for drying for 48 h to obtain the positive electrode material + solid electrolyte laminated composite electrode sheet according to the present invention.

[0064] Example 4

[0065] Weigh 8 g of LiFePO4, 1.65 g of solid electrolyte Li6PS5Cl, 0.05 g of styrene-butadiene rubber, and 0.3 g of conductive agent SP, add them to a ball mill jar, and ball mill at a speed of 200 rpm for 30 min. Subsequently, the ball milled and mixed powder was placed in a 100 mL slurry mixing jar, and xylene was added thereto to make the solid-liquid ratio 50%. The slurry mixing was carried out for a total of 5 min to obtain a uniform positive electrode active material layer slurry. Then, by means of blade coating, the positive electrode active material layer slurry was evenly coated on the surface of the current collector aluminum foil, with a coating thickness of 50 μm, and then placed in a vacuum drying oven at 50 °C for drying for 24 h.

[0066] Weigh 9.945 g of Li6PS5Cl and 0.055 g of styrene-butadiene rubber, mix evenly, add them to a ball mill jar, and ball mill at a speed of 300 rpm for 30 min. Subsequently, the ball milled and mixed powder was placed in a 100 mL slurry mixing jar, and xylene was added thereto to make the solid-liquid ratio 50%. The slurry mixing was carried out for a total of 5 min to obtain a uniform solid electrolyte slurry. Then, by means of blade coating, the obtained solid electrolyte slurry was evenly coated on the surface of the above-mentioned electrode sheet coated with the positive electrode material, with a coating thickness of 35 μm, and then placed in a vacuum drying oven at 55 °C for drying for 48 h to obtain the positive electrode material + solid electrolyte laminated composite electrode sheet according to the present invention.

[0067] Example 5

[0068] Weigh 8 g of NCM95, 1.65 g of solid electrolyte Li6PS5Cl, 0.05 g of styrene-butadiene rubber, and 0.3 g of conductive agent SP, add them to a ball mill jar, and ball mill at a speed of 200 rpm for 30 min. Subsequently, the ball milled and mixed powder was placed in a 100 mL slurry mixing jar, and xylene was added thereto to make the solid-liquid ratio 50%. The slurry mixing was carried out for a total of 5 min to obtain a uniform positive electrode active material layer slurry. Then, by means of blade coating, the positive electrode active material layer slurry was evenly coated on the surface of the current collector aluminum foil, with a coating thickness of 80 μm, and then placed in a vacuum drying oven at 60 °C for drying for 48 h.

[0069] Weigh 9.9 g of Li5.3 PS 4.3 Cl 1.7 、 0.1 g of styrene-butadiene rubber was added, mixed evenly and put into a ball mill jar, and ball milled at a speed of 200 rpm for 30 min. Subsequently, the powder mixture after ball milling was placed in a 100 mL slurry mixing jar, and xylene was added thereto to make the solid-liquid ratio 50%. The slurry mixing was carried out for a total of 5 min to obtain a uniform solid electrolyte slurry. Then, by means of blade coating, the obtained solid electrolyte slurry was evenly coated on the surface of the above-mentioned electrode sheet coated with the positive electrode material, and the coating thickness was 35 μm. Subsequently, it was placed in a vacuum drying oven at 55 °C and dried for 48 h to obtain a positive electrode material + solid electrolyte laminated composite electrode sheet according to the present invention.

[0070] Example 6

[0071] Weigh 8 g of NCM811, 1.6 g of solid electrolyte Li6PS5Cl, 0.1 g of styrene-butadiene rubber, and 0.3 g of conductive agent SP, add them to a ball mill jar, and ball mill at a speed of 200 rpm for 30 min. Subsequently, the powder mixture after ball milling was placed in a 100 mL slurry mixing jar, and xylene was added thereto to make the solid-liquid ratio 50%. The slurry mixing was carried out for a total of 5 min to obtain a uniform positive electrode active material layer slurry. Then, by means of blade coating, the positive electrode active material layer slurry was evenly coated on the surface of the current collector aluminum foil, and the coating thickness was 80 μm. Subsequently, it was placed in a vacuum drying oven at 60 °C and dried for 48 h.

[0072] Weigh 9.89 g of Li 5.5 PS 4.5 Cl 1.5 、 0.11 g of styrene-butadiene rubber was added, mixed evenly and put into a ball mill jar, and ball milled at a speed of 200 rpm for 30 min. Subsequently, the powder mixture after ball milling was placed in a 100 mL slurry mixing jar, and xylene was added thereto to make the solid-liquid ratio 50%. The slurry mixing was carried out for a total of 5 min to obtain a uniform solid electrolyte slurry. Then, by means of blade coating, the obtained solid electrolyte slurry was evenly coated on the surface of the above-mentioned electrode sheet coated with the positive electrode material, and the coating thickness was 35 μm. Subsequently, it was placed in a vacuum drying oven at 60 °C and dried for 24 h to obtain a positive electrode material + solid electrolyte laminated composite electrode sheet according to the present invention.

[0073] Comparative Example 1

[0074] Weigh 8 g of NCM562, 1.6 g of solid electrolyte Li6PS5Cl, 0.1 g of styrene-butadiene rubber, and 0.3 g of conductive agent SP. Add them to a ball-milling jar and ball-mill at a speed of 200 rpm for 30 min. Then, place the ball-milled and mixed powder in a 100 mL slurry mixing jar, add xylene to it to make the solid-liquid ratio 50%, and slurry for a total of 5 min to obtain a uniform slurry of the positive electrode active material layer. Then, using the doctor blade coating method, uniformly coat the slurry of the positive electrode active material layer on the surface of the current collector aluminum foil with a coating thickness of 80 μm, and then place it in a vacuum drying oven at 60 °C for drying for 48 h.

[0075] Weigh 9.95 g of Li 5.5 PS 4.5 Cl 1.5 and 0.05 g of styrene-butadiene rubber, mix them evenly, add them to a ball-milling jar and ball-mill at a speed of 200 rpm for 30 min. Then, place the ball-milled and mixed powder in a 100 mL slurry mixing jar, add xylene to it to make the solid-liquid ratio 50%, and slurry for a total of 5 min to obtain a uniform slurry of the solid electrolyte. Then, using the doctor blade coating method, uniformly coat the obtained solid electrolyte slurry on the surface of the above-mentioned electrode sheet coated with the positive electrode material with a coating thickness of 35 μm, and then place it in a vacuum drying oven at 60 °C for drying for 48 h to obtain a positive electrode material + solid electrolyte laminated composite electrode sheet.

[0076] Comparative Example 2

[0077] Weigh 8 g of NCM562, 1.6 g of solid electrolyte Li6PS5Cl, 0.2 g of styrene-butadiene rubber, and 0.3 g of conductive agent SP. Add them to a ball-milling jar and ball-mill at a speed of 200 rpm for 30 min. Then, place the ball-milled and mixed powder in a 100 mL slurry mixing jar, add xylene to it to make the solid-liquid ratio 50%, and slurry for a total of 5 min to obtain a uniform slurry of the positive electrode active material layer. Then, using the doctor blade coating method, uniformly coat the positive electrode active material layer slurry on the surface of the current collector aluminum foil with a coating thickness of 80 μm, and then place it in a vacuum drying oven at 60 °C for drying for 48 h.

[0078] Weigh 9.9 g of Li 5.5 PS 4.5 Cl 1.5, 0.1 g of styrene-butadiene rubber was added, mixed evenly and put into a ball mill jar, and ball milled at a speed of 200 rpm for 30 min. Subsequently, the ball milled and mixed powder was placed in a 100 mL slurry mixing jar, and xylene was added thereto to make the solid-liquid ratio 50%, and the slurry mixing was carried out for a total of 5 min to obtain a uniform solid electrolyte slurry. Then, by means of blade coating, the obtained solid electrolyte slurry was evenly coated on the surface of the above-mentioned electrode sheet coated with the positive electrode material, the coating thickness was 35 μm, and then it was placed in a vacuum drying oven at 60 °C and dried for 48 h to obtain a positive electrode material + solid electrolyte laminated composite electrode sheet.

[0079] Comparative Example 3

[0080] Weigh 8 g of NCM562, 1.2 g of solid electrolyte Li6PS5Cl, 0.5 g of styrene-butadiene rubber, and 0.3 g of conductive agent SP, add them to a ball mill jar, and ball mill at a speed of 200 rpm for 30 min. Subsequently, the ball milled and mixed powder was placed in a 100 mL slurry mixing jar, and xylene was added thereto to make the solid-liquid ratio 50%, and the slurry mixing was carried out for a total of 5 min to obtain a uniform positive electrode active material layer slurry. Then, by means of blade coating, the positive electrode active material layer slurry was evenly coated on the surface of the current collector aluminum foil, the coating thickness was 80 μm, and then it was placed in a vacuum drying oven at 60 °C and dried for 48 h.

[0081] Weigh 9.9 g of Li 5.5 PS 4.5 Cl 1.5 , 0.1 g of styrene-butadiene rubber was added, mixed evenly and put into a ball mill jar, and ball milled at a speed of 200 rpm for 30 min. Subsequently, the ball milled and mixed powder was placed in a 100 mL slurry mixing jar, and xylene was added thereto to make the solid-liquid ratio 50%, and the slurry mixing was carried out for a total of 5 min to obtain a uniform solid electrolyte slurry. Then, by means of blade coating, the obtained solid electrolyte slurry was evenly coated on the surface of the above-mentioned electrode sheet coated with the positive electrode material, the coating thickness was 35 μm, and then it was placed in a vacuum drying oven at 60 °C and dried for 48 h to obtain a positive electrode material + solid electrolyte laminated composite electrode sheet.

[0082] Using a 2T double-roll rolling press, at a rolling environment temperature of 25 °C, the laminated composite electrode sheets prepared in Examples 1-6 and Comparative Examples 1-3 above were subjected to a rolling rate test, where:

[0083] Rolling rate = (width after rolling / width before rolling) × 100%.

[0084] The obtained rolling rate test results are shown in Table 1 below.

[0085] Table 1

[0086]

[0087] The laminated composite electrodes prepared in Examples 1-6 and Comparative Examples 1-3 were assembled into batteries. At a test temperature of 25 °C, a voltmeter was used to measure the short-circuit rate of every 100 solid-state batteries. The results are shown in Table 2 below.

[0088] Table 2

[0089] Number of solid-state batteries prepared y - x Short-circuit rate % Example 1 100 pieces 3 0 Example 2 100 pieces 2 0 Example 3 100 pieces 0.5 1 Example 4 100 pieces 0.5 2 Example 5 100 pieces 0.5 1 Example 6 100 pieces 0.1 3 Comparative Example 1 100 pieces -0.5 50 Comparative Example 2 100 pieces -1 45 Comparative Example 3 100 pieces -4 60

[0090] As can be seen from Table 1 and Table 2, compared with the comparative examples, in the examples according to the present invention, when ensuring that the binder content in the solid electrolyte layer is greater than the binder content in the positive electrode active material layer, after rolling under the same conditions and then performing the rolling rate test, the rolling rate of the solid electrolyte layer always remains greater than that of the positive electrode active material layer. Thus, it is ensured that the solid electrolyte layer completely coats the positive electrode active material layer. Therefore, when using the laminated composite electrode sheets prepared by the method according to the present invention for stacking to prepare a battery, the occurrence of contact short circuit between the positive and negative electrodes is effectively reduced, and the preparation success rate of the all-solid-state battery is greatly improved.

[0091] The present application has been described in conjunction with preferred embodiments. However, these embodiments are only exemplary and illustrative. On this basis, various substitutions and improvements can be made to the present application and all fall within the protection scope of the present application.

Claims

1. A solid-state lithium-ion battery, comprising a composite positive electrode sheet and a negative electrode sheet, wherein the composite positive electrode sheet includes: A positive current collector; A positive active material layer disposed on the surface of the positive current collector with a width and a thickness of D1 and L1, respectively; And A solid electrolyte layer disposed on the surface of the positive active material layer with a width and a thickness of D2 and L2, respectively, and satisfying: D2 (μm) = D1 (μm) + 25000 / L2 (μm), and 10 μm ≤ L2 ≤ 100 μm; The binder content in the solid electrolyte layer is greater than the binder content in the positive active material layer; Wherein the positive active material layer includes a positive active material, a conductive agent, a first solid electrolyte, and a first binder, and by mass of the positive active material layer, the percentage content N1 of the first binder satisfies: 0.5 ≤ N1 ≤ 5; the solid electrolyte layer includes a second solid electrolyte and a second binder, and by mass of the solid electrolyte layer, the percentage content N2 of the second binder satisfies: 0.55 ≤ N2 ≤ 5.5; and 2 ≤ N2 - N1 ≤ 3.

2. The solid-state lithium-ion battery according to claim 1, wherein the positive electrode active material is selected from LiCoO2; LiMn x O2, x = 1; LiNi 1-x Mn x O2, 0 < x < 1; LiNi 1-x-y Co x Mn y O2, 0 ≤ x ≤ 0.5, 0 ≤ y ≤ 0.5; LiFePO4; and one or more of sulfur-containing composite positive electrode active materials.

3. The solid-state lithium-ion battery according to claim 1 or 2, wherein the first solid electrolyte and the second solid electrolyte are each independently one or more selected from the following: perovskite-type solid electrolytes; NASICON-type solid electrolytes; LISICON-type solid electrolytes; garnet-type oxide solid electrolytes; crystalline Li x M y PS z , where M is one or more selected from Si, Ge, Sn, x + 4y + 5 = 2z, 0 ≤ y ≤ 1; glass-ceramic Li2S-P2S5; and Li 6-y PS 5-y X y , where X is one or more selected from Cl, Br, I, 0 ≤ y ≤ 1.

8.

4. The solid-state lithium-ion battery according to claim 3, wherein the first solid electrolyte and the second solid electrolyte are each independently selected from one or more of Li6PS5Cl and Li 5.5 PS 4.5 Cl 1.5 among others.

5. The solid-state lithium-ion battery according to claim 1, wherein the first binder and the second binder are each independently one or more selected from styrene-butadiene rubber (SBR), nitrile-butadiene rubber (NBR), hydrogenated styrene-butadiene rubber, hydrogenated nitrile-butadiene rubber, sodium carboxymethyl cellulose (CMC), polyacrylic acid (PAA), polyacrylonitrile (PAN), polyimide (PI), polyvinylidene fluoride (PVDF); the conductive agent is one or more selected from carbon black conductive agents, graphite conductive agents, and graphene conductive agents, the carbon black conductive agent includes acetylene black, 350G, Ketjen black, or a combination thereof, the graphite conductive agent includes KS-6, KS-15, SFG-6, SFG-15, or a combination thereof, and the graphene conductive agent includes single-layer, multi-layer graphene, or a combination thereof.

6. The solid-state lithium-ion battery according to claim 5, wherein the first binder and the second binder are each independently hydrogenated styrene-butadiene rubber.

7. The solid-state lithium-ion battery according to claim 5, wherein the negative electrode sheet includes one or more negative active materials selected from the following: artificial graphite, natural graphite, silicon monoxide, silicon carbide, ferrosilicon alloy, mesocarbon microbeads, nanosilicon, lithium metal, or lithium alloy.

8. The solid-state lithium-ion battery according to claim 7, wherein the negative electrode sheet includes one or more negative active materials selected from the following: artificial graphite, natural graphite, silicon carbide, or lithium alloy.

9. A method for preparing a solid-state lithium-ion battery according to any one of claims 1 to 8, comprising the following steps: (1) Form a positive active material layer with a width and a thickness of D1 and L1, respectively, on the positive current collector, and form a solid electrolyte layer with a width and a thickness of D2 and L2, respectively, on the surface of the positive active material layer, such that D2 (μm) = D1 (μm) + 25000 / L2 (μm), and 10 μm ≤ L2 ≤ 100 μm, to obtain a composite positive electrode sheet; the binder content in the solid electrolyte layer is greater than the binder content in the positive active material layer; (2) Prepare a negative electrode sheet; and (3) Assemble the composite positive electrode sheet and the negative electrode sheet into the solid-state lithium-ion battery; Wherein, in the formation of the positive electrode active material layer, a positive electrode active material, a conductive agent, a first solid electrolyte, and a first binder are mixed so that, based on the mass of the positive electrode active material layer, the percentage content N1 of the first binder satisfies: 0.5 ≤ N1 ≤ 5; in the formation of the solid electrolyte layer, a second solid electrolyte and a second binder are mixed so that, based on the mass of the solid electrolyte layer, the percentage content N2 of the second binder satisfies: 0.55 ≤ N2 ≤ 5.5; and 2 ≤ N2−N1 ≤ 3.

10. The method according to claim 9, wherein the first binder and the second binder are each independently one or more selected from styrene-butadiene rubber (SBR), nitrile rubber (NBR), hydrogenated styrene-butadiene rubber, hydrogenated nitrile rubber, sodium carboxymethyl cellulose (CMC), polyacrylic acid (PAA), polyacrylonitrile (PAN), polyimide (PI), polyvinylidene fluoride (PVDF); the conductive agent is one or more selected from carbon black conductive agent, graphite conductive agent, and graphene conductive agent, the carbon black conductive agent includes acetylene black, 350G, Ketjen black, or a combination thereof, the graphite conductive agent includes KS-6, KS-15, SFG-6, SFG-15, or a combination thereof, and the graphene conductive agent includes single-layer, multi-layer graphene, or a combination thereof.

11. The method according to claim 10, wherein the first binder and the second binder are each independently hydrogenated styrene-butadiene rubber.

12. The method according to claim 10, wherein the particle size of the first or second solid electrolyte is independently 0.5 to 5 μm.

13. The method according to claim 12, wherein the particle size of the first or second solid electrolyte is independently 0.5 to 3 μm.

14. The method according to claim 10, wherein the particle size of the first or second solid electrolyte is independently 1 to 3 μm.

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