Solid-state battery composite electrode, preparation method thereof, solid-state battery, preparation method thereof and application

Abstract

The present invention relates to the technical field of lithium-ion batteries, and discloses a solid-state battery composite electrode, a preparation method thereof, a solid-state battery, a preparation method and application of the solid-state battery. The composite electrode includes a current collector, an electrode coating disposed on the surface of the current collector, a solid electrolyte layer disposed on the surface of the electrode coating, and a mixed layer disposed between the electrode coating and the solid electrolyte layer; wherein, the electrode coating and the mixed layer contain electrode active materials, the solid electrolyte layer and the mixed layer contain solid electrolytes, and the particle size D50 of the solid electrolyte is smaller than the particle size D50 of the electrode active material. The solid-state battery prepared by using the composite electrode provided by the present invention has a low interfacial impedance and a significantly improved rate performance. The preparation method provided by the present invention is easy to implement and has a low cost.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium-ion batteries, and particularly to a composite electrode for a solid-state battery, a preparation method thereof, a solid-state battery, a preparation method of the solid-state battery, and an application thereof. Background Art

[0002] Lithium-ion batteries have advantages such as high energy density, long cycle life, and no memory effect, and have been widely used in fields such as consumer electronics, household appliances, and power tools. Especially in recent years, with the continuous growth of the production and sales scale of electric vehicles, the demand for lithium-ion batteries has been continuously increasing, and higher requirements have also been put forward for their performance such as energy density, safety, and stability.

[0003] Traditional lithium-ion batteries use liquid electrolytes, which contain volatile and flammable organic solvents such as ethylene carbonate and dimethyl carbonate. They have poor thermal stability and are prone to combustion and fire, which is an important factor for the safety hazards of lithium-ion batteries. In addition, conventional liquid electrolytes are limited by disadvantages such as narrow electrochemical windows and poor stability at the electrode-electrolyte interface, and it is difficult to cooperate with high-energy density electrode materials such as high-nickel oxide cathodes, high-voltage cathodes, and metallic lithium anodes for stable operation, resulting in limited improvement of the battery energy density.

[0004] Solid-state batteries use solid electrolytes and have advantages such as high stability, high safety, and high energy density, becoming a current research hotspot and being called the next-generation lithium-ion batteries. They have high mechanical strength to prevent the piercing of lithium dendrites, and at the same time have the characteristics of non-volatility, non-leakage, and non-flammability, eliminating the possibility of combustion from the root cause and having high safety performance. They have a wide electrochemical window and can match higher-energy density electrode materials to improve the energy density of the battery.

[0005] However, solid-state batteries currently face many technical difficulties, and their commercialization also faces many challenges. Among them, the high interfacial impedance between the solid electrolyte and the electrode is one of the technical difficulties that need to be overcome urgently. The contact mode between the solid electrolyte and the electrode is solid-solid contact, and there is no wettability at the interface, forming a large interfacial contact resistance, reducing the Li + migration kinetics at the interface, resulting in an increase in battery impedance and a decrease in rate performance.

[0006] CN111009682A and CN111834626A disclose using a first solid electrolyte and a second solid electrolyte with two different thicknesses, different roughnesses, or different ionic conductivities to improve the interfacial impedance, but it requires two layers or two solid electrolyte sheets, increasing the complexity of the manufacturing process.

[0007] By optimizing the interface treatment process, such as in-situ growth of an electrode layer on an electrolyte sheet, pulsed laser deposition, sol-gel method, co-sintering, etc., the interface structure between the solid electrolyte and the electrode can be effectively improved, and the interface impedance can be reduced. Among them, pulsed laser deposition can precisely control the deposition thickness, enhance the interface contact effect, effectively reduce the interface impedance, and optimize the battery performance. However, its cost is high and it is not suitable for large-scale production applications; it is difficult to control the composition, structure, and morphology of the interface layer in co-sintering, in-situ growth of the electrode layer, etc. In order to obtain a low-impedance interface with good contact and stable structure, a simple, low-cost, and easy-to-operate interface treatment process needs to be further developed. Summary of the Invention

[0008] The purpose of the present invention is to overcome the problems of high impedance and poor rate performance of solid-state batteries in the prior art, and provide a solid-state battery, a preparation method and application of the solid-state battery. The solid-state battery has the advantages of low interface impedance and good rate performance.

[0009] To achieve the above purpose, in the first aspect of the present invention, a solid-state battery composite electrode is provided. The composite electrode includes a current collector, an electrode coating provided on the surface of the current collector, a solid electrolyte layer provided on the surface of the electrode coating, and a mixed layer provided between the electrode coating and the solid electrolyte layer; wherein, the electrode coating and the mixed layer contain electrode active materials, the solid electrolyte layer and the mixed layer contain solid electrolytes, and the particle size D50 of the solid electrolyte is smaller than the particle size D50 of the electrode active material.

[0010] In the second aspect of the present invention, a method for preparing the solid-state battery composite electrode described in the first aspect is provided. The method includes:

[0011] Coating a slurry containing powder and a solvent on the surface of the current collector and drying it to obtain an electrode sheet, and then spreading a solid electrolyte on the surface of the electrode sheet and rolling it; wherein, the powder includes electrode active materials, optionally a conductive agent, and optionally a binder.

[0012] In the third aspect of the present invention, a solid-state battery is provided. The solid-state battery includes stacked battery units, and each battery unit includes a positive electrode, a negative electrode, and a solid electrolyte sheet provided between the positive electrode and the negative electrode. The positive electrode and the negative electrode are the solid-state battery composite electrodes described in the first aspect.

[0013] In the fourth aspect of the present invention, a method for preparing the solid-state battery described in the third aspect is provided. The method includes:

[0014] (1) Coating a first slurry containing a positive electrode material, a first solvent, an optional first conductive agent, and an optional first binder on the surface of a positive electrode current collector, and drying to obtain a positive electrode sheet. Then, spreading a first electrolyte on the surface of the positive electrode sheet and performing a first rolling to obtain a composite positive electrode;

[0015] (2) Coating a second slurry containing a negative electrode material, a second solvent, an optional second conductive agent, and an optional second binder on the surface of a negative electrode current collector, and drying to obtain a negative electrode sheet. Then, spreading a second electrolyte on the surface of the negative electrode sheet and performing a second rolling to obtain a composite negative electrode;

[0016] (3) Stacking the composite positive electrode, a solid electrolyte sheet containing a third electrolyte, and the composite negative electrode in sequence and performing pressing.

[0017] The fifth aspect of the present invention provides the application of the solid-state battery described in the third aspect in energy storage devices, electric vehicles, and electronic products.

[0018] Through the above technical solutions, the present invention has the following advantages:

[0019] (1) The solid-state battery composite electrode provided by the present invention can reduce the interfacial impedance between the electrode sheet and the solid electrolyte sheet;

[0020] (2) The preparation process of the method provided by the present invention is relatively easy to implement and has low cost;

[0021] (3) The solid-state battery prepared by using the solid-state battery composite electrode provided by the present invention has low impedance and good rate performance. Specific Embodiments

[0022] In the ranges disclosed herein, the endpoints and any values are not limited to the exact ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0023] The first aspect of the present invention provides a solid-state battery composite electrode, which includes a current collector, an electrode coating disposed on the surface of the current collector, a solid electrolyte layer disposed on the surface of the electrode coating, and a mixed layer disposed between the electrode coating and the solid electrolyte layer; wherein, the electrode coating and the mixed layer contain electrode active substances, the solid electrolyte layer and the mixed layer contain solid electrolytes, and the particle size D50 of the solid electrolyte is less than the particle size D50 of the electrode active substance.

[0024] According to some embodiments of the present invention, the particle size D50 of the solid electrolyte is smaller than the particle size D50 of the electrode active material. The smaller solid electrolyte powder can be filled into the gaps between the electrode active material particles, which is beneficial to improving the contact between the electrode active material and the solid electrolyte and the contact between the electrode sheet and the solid electrolyte sheet.

[0025] In order to further improve the contact effect between the electrode sheet and the solid electrolyte sheet, preferably, the difference between the particle size D50 of the electrode active material and the solid electrolyte is 3 - 25 μm, preferably 5 - 20 μm. In the present invention, the particle size D50 of the electrode active material and the solid electrolyte is measured by a laser particle size analyzer.

[0026] According to some embodiments of the present invention, preferably, the electrode coating is a positive electrode coating or a negative electrode coating, and the thicknesses of the positive electrode coating and the negative electrode coating are the same or different, and are independently 2 - 10 μm, preferably 3 - 8 μm.

[0027] According to some embodiments of the present invention, preferably, the solid electrolyte layer is a solid electrolyte layer I or a solid electrolyte layer II, and the thicknesses of the solid electrolyte layer I and the solid electrolyte layer II are the same or different, and are independently 0.3 - 5 μm, preferably 0.5 - 1.5 μm.

[0028] According to some embodiments of the present invention, preferably, the mixed layer is a positive electrode mixed layer or a negative electrode mixed layer, and the thicknesses of the positive electrode mixed layer and the negative electrode mixed layer are the same or different, and are independently 5 - 250 μm, preferably 10 - 150 μm. In the present invention, the thicknesses of the electrode coating, the solid electrolyte layer, and the mixed layer are measured by a scanning electron microscope and a micrometer. The thicknesses of the electrode coating, the solid electrolyte layer, and the mixed layer within the above - preferred ranges are beneficial to reducing the interfacial impedance.

[0029] According to some embodiments of the present invention, preferably, the solid electrolyte is a first electrolyte or a second electrolyte, and the first electrolyte and the second electrolyte are the same or different, and are independently selected from NASICON - type solid electrolytes (for example, it can be, including but not limited to, Li 1.3 Al 0.3 Ti 1.7 (PO4)3, lithium aluminum titanium phosphate), LISICON - type solid electrolytes (for example, it can be Li 3.6 Ge 0.6 V 0.4 O4), perovskite - type solid electrolytes (for example, it can be Li 0.33 La 0.557 TiO3), garnet - type solid electrolytes (for example, it can be Li7La3Zr2O 12) and at least one of a chalcogen-based solid electrolyte (for example, it can be Li 10 GeP2S 12 ), preferably at least one of a NASICON-type solid electrolyte, a perovskite-type solid electrolyte, and a garnet-type solid electrolyte, more preferably lithium aluminum titanium phosphate. Further preferably, the first electrolyte is the same as the second electrolyte. Adopting the above preferred embodiment is beneficial to reducing the battery impedance and is easy to process.

[0030] According to some embodiments of the present invention, preferably, the electrode active material is a positive electrode material or a negative electrode material, and the positive electrode material is selected from lithium cobalt oxide (LiCoO2), LiNiO2, LiNi x Co 1-x O2 (0 < x < 1), LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, LiNi 0.6 Co 0.2 Mn 0.2 O2, LiNi 0.8 Co 0.1 Mn 0.1 O2, LiNi 0.85 Co 0.1 Al 0.05 O2, LiMn2O4, LiNi 0.5 Mn 1.5 O4, lithium-rich manganese-based positive electrode materials (xLi2MnO3·(1 - x)LiMO2 (M = Ni, Co, Mn)), phosphates (LiMPO4 (M = Fe, Mn)), and at least one of sulfur electrodes, preferably at least one of LiCoO2, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, LiNi 0.6 Co 0.2 Mn 0.2 O2, and LiNi 0.8 Co 0.1 Mn 0.1 O2; the negative electrode material is selected from metallic lithium, lithium alloys (Li x M (M = In, B, Al, Ga, Sn, Si, Ge, Pb, As, Bi, Sb, Cu, Ag, Zn)), carbon-based materials (for example, it can include but is not limited to one or more of artificial graphite, natural graphite, amorphous carbon, and mesophase carbon microspheres), silicon-based materials (for example, it can include but is not limited to one or more of silicon-carbon materials, silicon-oxygen materials, and nanosilicon), tin-based materials, and lithium titanate (Li4Ti5O 12) at least one of them, preferably at least one of artificial graphite, silicon-carbon material and silicon-oxygen material, more preferably artificial graphite.

[0031] According to some embodiments of the present invention, preferably, the current collector is a positive current collector or a negative current collector, the positive current collector is aluminum foil; the negative current collector is copper foil.

[0032] According to some embodiments of the present invention, preferably, the electrode coating and the mixed layer further contain a conductive agent and / or a binder.

[0033] According to some embodiments of the present invention, preferably, the conductive agent is a first conductive agent or a second conductive agent, the first conductive agent and the second conductive agent are the same or different, and each independently selected from at least one of acetylene black, conductive carbon black, carbon nanotubes, graphene and carbon fiber, preferably conductive carbon black.

[0034] According to some embodiments of the present invention, preferably, the binder is a first binder or a second binder, the first binder and the second binder are the same or different, and each independently selected from at least one of polyvinylidene fluoride, sodium carboxymethyl cellulose, styrene-butadiene rubber and polyacrylic acid; more preferably, the first binder and the second binder are different; further preferably, the first binder is polyvinylidene fluoride; the second binder is a mixture of styrene-butadiene rubber and sodium carboxymethyl cellulose, and in the mixture, the weight ratio of styrene-butadiene rubber to sodium carboxymethyl cellulose is 1:(1 - 3).

[0035] According to some embodiments of the present invention, preferably, the weight ratio of the positive electrode material, the first conductive agent and the first binder is (80 - 95):(2 - 10):(3 - 10).

[0036] According to some embodiments of the present invention, preferably, the weight ratio of the negative electrode material, the second conductive agent and the second binder is (80 - 95):(1.5 - 10):(4.5 - 10).

[0037] According to a preferred embodiment of the present invention, the solid electrolyte layer I and the positive electrode mixed layer contain a first electrolyte, and the particle size D50 of the first electrolyte is smaller than the particle size D50 of the positive electrode material; the solid electrolyte layer II and the negative electrode mixed layer contain a second electrolyte, and the particle size D50 of the second electrolyte is smaller than the particle size D50 of the negative electrode material. Preferably, the difference between the particle size D50 of the positive electrode material and the first electrolyte is 3 - 25 μm, preferably 5 - 20 μm; and / or, the difference between the particle size D50 of the negative electrode material and the second electrolyte is 3 - 25 μm, preferably 5 - 20 μm. Adopting the above preferred embodiment is beneficial to further reducing the impedance of the solid-state battery and further improving the rate performance of the solid-state battery.

[0038] According to a particularly preferred embodiment of the present invention, when the composite electrode is a composite positive electrode, the composite positive electrode includes a positive current collector, a positive electrode coating provided on the surface of the positive current collector, a solid electrolyte layer I provided on the surface of the positive electrode coating, and a positive electrode mixed layer provided between the positive electrode coating and the solid electrolyte layer I; wherein, the positive electrode coating and the positive electrode mixed layer contain a positive electrode material, a first conductive agent, and a first binder, the solid electrolyte layer I and the positive electrode mixed layer contain a first electrolyte, and the particle size D50 of the first electrolyte is smaller than the particle size D50 of the positive electrode material; the thickness of the positive electrode coating is 2-10 μm; the thickness of the solid electrolyte layer I is 0.3-5 μm; the thickness of the positive electrode mixed layer is 5-250 μm; the positive current collector is aluminum foil; the positive electrode material is lithium cobaltate, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, LiNi 0.6 Co 0.2 Mn 0.2 O2 and LiNi 0.8 Co 0.1 Mn 0.1 O2, or at least one of them; the first electrolyte is lithium titanium aluminum phosphate; the first binder is polyvinylidene fluoride; the weight ratio of the positive electrode material, the first conductive agent, and the first binder is (80-95):(2-10):(3-10).

[0039] According to a particularly preferred embodiment of the present invention, when the composite electrode is a composite negative electrode, the composite negative electrode includes a negative current collector, a negative electrode coating provided on the surface of the negative current collector, a solid electrolyte layer II provided on the surface of the negative electrode coating, and a negative electrode mixed layer provided between the negative electrode coating and the solid electrolyte layer II; wherein, the negative electrode coating and the negative electrode mixed layer contain a negative electrode material, a second conductive agent, and a second binder, the solid electrolyte layer II and the negative electrode mixed layer contain a second electrolyte, and the particle size D50 of the second electrolyte is smaller than the particle size D50 of the negative electrode material; the thickness of the negative electrode coating is 2-10 μm; the thickness of the solid electrolyte layer II is 0.3-5 μm; the thickness of the negative electrode mixed layer is 5-250 μm; the negative current collector is copper foil; the negative electrode material is artificial graphite; the second electrolyte is lithium titanium aluminum phosphate; the second binder is a mixture of styrene-butadiene rubber and sodium carboxymethyl cellulose, and in the mixture, the weight ratio of styrene-butadiene rubber to sodium carboxymethyl cellulose is 1:(1-3); the weight ratio of the negative electrode material, the second conductive agent, and the second binder is (80-95):(1.5-10):(4.5-10).

[0040] Adopting the above particularly preferred embodiment can particularly enable the solid-state battery to obtain lower impedance and better rate performance.

[0041] In a second aspect of the present invention, there is provided a method for preparing the solid-state battery composite electrode described in the first aspect, the method comprising:

[0042] Coating a slurry containing powder and a solvent on the surface of a current collector and drying to obtain an electrode sheet, and then spreading a solid electrolyte on the surface of the electrode sheet and performing rolling; wherein, the powder comprises an electrode active material, an optional conductive agent, and an optional binder.

[0043] According to some embodiments of the present invention, the types and amounts of the solid electrolyte, the electrode active material, the current collector, the conductive agent, and the binder can all be selected with reference to the above, and will not be elaborated herein.

[0044] According to some embodiments of the present invention, preferably, the solvent is a first solvent or a second solvent, the first solvent and the second solvent are the same or different, and each independently is selected from at least one of water, N-methylpyrrolidone, and ethanol.

[0045] According to some embodiments of the present invention, preferably, the weight ratio of the amount of the powder to the amount of the solvent is 100:(30 - 50).

[0046] According to some embodiments of the present invention, preferably, the conditions of the rolling include: the rolling pressure is 20 - 100 kN / cm, preferably 30 - 60 kN / cm; and / or, the rolling temperature is 60 - 200 °C, preferably 100 - 200 °C; and / or, the number of rolling times is 1 - 5 times, preferably 2 - 3 times. At a higher rolling temperature, the solid electrolyte powder is more likely to fill into the gaps of the active material. In addition, using the rolling pressure and the number of rolling times within the above preferred ranges is more conducive to the filling of the solid electrolyte powder.

[0047] According to some embodiments of the present invention, preferably, the amount of the solid electrolyte is controlled in combination with the conditions of the rolling such that in the prepared solid-state battery composite electrode, the thickness of the solid electrolyte layer is 0.3 - 5 μm, preferably 0.5 - 1.5 μm; and the thickness of the mixed layer is 5 - 250 μm, preferably 10 - 150 μm.

[0048] The ionic conductivity of the electrode active material itself is relatively high, but its contact impedance with the solid electrolyte sheet is large. In order to improve the contact between the solid electrolyte sheet and the electrode and reduce the interfacial impedance between the two, the existing methods generally make the electrode into a composite electrode with a uniform concentration of the solid electrolyte, and the amount of the solid electrolyte used is relatively large. However, the inventors of the present invention found during the research process that by controlling the particle size D50 of the solid electrolyte to be smaller than the particle size D50 of the electrode active material, spreading the solid electrolyte with this specific particle size on the surface of the electrode sheet, and combining the rolling method to prepare the composite electrode, in the obtained solid-state battery composite electrode, the distribution of the solid electrolyte in the composite electrode has a concentration gradient, that is: electrode active material / (electrode active material + a small amount of solid electrolyte) / (electrode active material + a large amount of solid electrolyte), which can reduce the amount of the solid electrolyte used, and at the same time does not affect the performance, that is, it can improve the contact between the solid electrolyte sheet and the electrode sheet, reduce the interfacial impedance between the two, and improve the rate performance of the solid-state battery.

[0049] According to a preferred embodiment of the present invention, when the method is used to prepare a solid-state battery composite positive electrode, a first slurry containing a first powder material and a first solvent is coated on the surface of a positive electrode current collector and dried to obtain a positive electrode sheet, and then a first electrolyte is spread on the surface of the positive electrode sheet and first rolled to obtain a composite positive electrode; wherein, the first powder material includes a positive electrode material, a first conductive agent, and a first binder.

[0050] According to some embodiments of the present invention, the weight ratio of the positive electrode material, the first conductive agent, and the first binder can be selected with reference to the above, and will not be elaborated here.

[0051] According to some embodiments of the present invention, preferably, the weight ratio of the amount of the first powder material to the amount of the first solvent is 100:(30 - 50).

[0052] According to some embodiments of the present invention, preferably, the conditions of the first rolling include: the rolling pressure is 30 - 60 kN / cm; the rolling temperature is 100 - 200 °C; the number of rolling times is 2 - 3 times.

[0053] According to some embodiments of the present invention, the amount of the first electrolyte is controlled in combination with the conditions of the first rolling, so that in the obtained solid-state battery composite positive electrode, the thickness of the solid electrolyte layer I is 0.3 - 5 μm, preferably 0.5 - 1.5 μm; the thickness of the positive electrode mixed layer is 5 - 250 μm, preferably 10 - 150 μm.

[0054] According to a preferred embodiment of the present invention, when the method is used to prepare a solid-state battery composite negative electrode, a second slurry containing a second powder and a second solvent is coated on the surface of the negative electrode collector and dried to obtain a negative electrode sheet, and then a second electrolyte is spread on the surface of the negative electrode sheet, and a second rolling is performed to obtain a composite negative electrode; wherein the second powder includes a negative electrode material, a second conductive agent and a second binder.

[0055] According to some embodiments of the present invention, the weight ratio of the negative electrode material, the second conductive agent and the second binder can be selected with reference to the above, and will not be described in detail here.

[0056] According to some embodiments of the present invention, preferably, the weight ratio of the second powder to the second solvent is 100:(30-50).

[0057] According to some embodiments of the present invention, preferably, the second rolling conditions include: a rolling pressure of 30-60 kN / cm; a rolling temperature of 100-200° C.; and a rolling number of 2-3 times.

[0058] According to some embodiments of the present invention, the amount of the second electrolyte is combined with the control of the second rolling conditions so that in the prepared solid-state battery composite negative electrode, the thickness of the solid electrolyte layer II is 0.3-5μm, preferably 0.5-1.5μm; the thickness of the negative electrode mixed layer is 5-250μm, preferably 10-150μm.

[0059] A third aspect of the present invention provides a solid-state battery, comprising stacked battery cells, each battery cell comprising a positive electrode, a negative electrode and a solid electrolyte sheet arranged between the positive electrode and the negative electrode, and the positive electrode and the negative electrode are the solid-state battery composite electrodes described in the first aspect.

[0060] According to some embodiments of the present invention, preferably, the positive electrode comprises a positive electrode current collector, a positive electrode coating disposed on the surface of the positive electrode current collector, a solid electrolyte layer I disposed on the surface of the positive electrode coating, and a positive electrode mixed layer disposed between the positive electrode coating and the solid electrolyte layer I; wherein the positive electrode coating and the positive electrode mixed layer contain a positive electrode material, the solid electrolyte layer I and the positive electrode mixed layer contain a first electrolyte, and the particle size D50 of the first electrolyte is smaller than the particle size D50 of the positive electrode material;

[0061] The negative electrode includes a negative current collector, a negative electrode coating disposed on the surface of the negative current collector, a solid electrolyte layer II disposed on the surface of the negative electrode coating, and a negative electrode mixed layer disposed between the negative electrode coating and the solid electrolyte layer II; wherein, the negative electrode coating and the negative electrode mixed layer contain a negative electrode material, the solid electrolyte layer II and the negative electrode mixed layer contain a second electrolyte, and the particle size D50 of the second electrolyte is smaller than the particle size D50 of the negative electrode material;

[0062] The solid electrolyte sheet contains a third electrolyte, and the third electrolyte is the same as or different from the first electrolyte and the second electrolyte; the third electrolyte is selected from at least one of NASICON-type solid electrolytes, LISICON-type solid electrolytes, perovskite-type solid electrolytes, garnet-type solid electrolytes, and chalcogenide solid electrolytes, preferably at least one of NASICON-type solid electrolytes, perovskite-type solid electrolytes, and garnet-type solid electrolytes, more preferably lithium titanium aluminum phosphate; further preferably, the first electrolyte, the second electrolyte, and the third electrolyte are the same.

[0063] According to some embodiments of the present invention, preferably, the difference between the particle size D50 of the first electrolyte, the second electrolyte, and the third electrolyte is less than 20%. Adopting the above preferred embodiments is beneficial to the penetration and contact between particles.

[0064] According to some embodiments of the present invention, preferably, the thickness of the solid electrolyte sheet is 20 - 700 μm, preferably 50 - 500 μm.

[0065] The fourth aspect of the present invention provides a method for preparing the solid-state battery described in the third aspect, and the method includes:

[0066] (1) Coating a first slurry containing a positive electrode material, a first solvent, an optional first conductive agent, and an optional first binder on the surface of a positive current collector, and drying to obtain a positive electrode sheet, then spreading a first electrolyte on the surface of the positive electrode sheet, and performing a first rolling to obtain a composite positive electrode;

[0067] (2) Coating a second slurry containing a negative electrode material, a second solvent, an optional second conductive agent, and an optional second binder on the surface of a negative current collector, and drying to obtain a negative electrode sheet, then spreading a second electrolyte on the surface of the negative electrode sheet, and performing a second rolling to obtain a composite negative electrode;

[0068] (3) Stacking the composite positive electrode, the solid electrolyte sheet containing the third electrolyte, and the composite negative electrode in sequence and performing pressing.

[0069] According to some embodiments of the present invention, the selection of each raw material and the operating conditions can be selected with reference to the above, and will not be elaborated here.

[0070] According to some embodiments of the present invention, preferably, in step (3), the pressure of the pressing is 0.3 - 0.8 MPa.

[0071] The fifth aspect of the present invention provides the application of the solid-state battery described in the third aspect in energy storage devices, electric vehicles, and electronic products.

[0072] The present invention will be described in detail below through examples.

[0073] In the following examples and comparative examples, unless otherwise specified, the raw materials used are commercially available products.

[0074] The particle size D50 of the electrode active material and the solid electrolyte is measured by a laser particle size analyzer;

[0075] The thicknesses of the electrode coating, the solid electrolyte layer, and the mixed layer are measured by a scanning electron microscope and a micrometer.

[0076] Example 1

[0077] (1) Preparation of the composite positive electrode: Lithium cobaltate (particle size D50 is 12 μm), conductive agent conductive carbon black, binder polyvinylidene fluoride, and solvent N-methylpyrrolidone are stirred and mixed evenly according to a weight ratio of 92:3:5:40 to obtain a first slurry. The first slurry is coated on an aluminum foil with a thickness of 15 μm and vacuum dried to obtain a positive electrode sheet. The purchased lithium titanium aluminum phosphate solid electrolyte powder (particle size D50 is 1 μm) is sprinkled on the surface of the positive electrode sheet, and the excess powder is scraped off with a spatula. Then, it is roll-pressed twice at 120°C and 60 kN / cm with a roll press to obtain a composite positive electrode, which is cut into a disc with a diameter of 10 mm for standby. In this composite positive electrode, the thickness of the positive electrode coating is 5 μm, the thickness of the positive electrode mixed layer is 40 μm, and the thickness of the solid electrolyte layer is 1 μm.

[0078] (2) Preparation of the composite negative electrode: Artificial graphite (particle size D50 is 10 μm), conductive agent conductive carbon black, binder styrene-butadiene rubber, binder sodium carboxymethyl cellulose, and solvent water are stirred and mixed evenly according to a weight ratio of 94:1.5:1.5:3:40 to obtain a first slurry. The first slurry is coated on a copper foil with a thickness of 8 μm and vacuum dried to obtain a negative electrode sheet. The purchased lithium titanium aluminum phosphate solid electrolyte powder (particle size D50 is 1 μm) is sprinkled on the surface of the negative electrode sheet, and the excess powder is scraped off with a spatula. Then, it is roll-pressed twice at 120°C and 40 kN / cm with a roll press to obtain a composite negative electrode, which is cut into a disc with a diameter of 12 mm for standby. In this composite negative electrode, the thickness of the negative electrode coating is 3 μm, the thickness of the negative electrode mixed layer is 30 μm, and the thickness of the solid electrolyte layer is 1 μm.

[0079] (3) Preparation of solid electrolyte sheet: The purchased lithium titanium aluminum phosphate solid electrolyte powder (with a particle size D50 of 1 μm) was pressed into a sheet with a thickness of 1000 μm under 150 MPa, and then sintered and polished to obtain a solid electrolyte sheet with a thickness of 500 μm.

[0080] (4) Preparation of solid-state battery: In the order of composite cathode - solid electrolyte sheet - composite anode, the prepared composite cathode, solid electrolyte sheet and composite anode were stacked and placed into a coin cell housing, and then pressed and encapsulated at 0.5 MPa with a sealing machine to complete the assembly of the coin cell.

[0081] (5) Rate performance test: The above solid-state battery was charged at a constant current of 0.1C (current density of 0.15 mA / cm 2 ) to 4.2V in the working voltage range of 3V - 4.2V and then held at a constant voltage until cutoff at 0.01C, and then discharged to 3V at currents of 0.1C, 0.2C, 0.5C, and 1C respectively to obtain the specific capacity of the solid-state battery at discharge rates of 0.1C, 0.2C, 0.5C, and 1C. The results are shown in Table 1.

[0082] Example 2

[0083] (1) Preparation of composite cathode: The ternary material LiNi 0.6 Co 0.2 Mn 0.2 O2 (with a particle size D50 of 7.2 μm), conductive agent conductive carbon black, binder polyvinylidene fluoride, and solvent N-methylpyrrolidone were stirred and mixed evenly according to a weight ratio of 90:4:6:40 to obtain a first slurry, which was coated on an aluminum foil with a thickness of 15 μm and dried in vacuum to obtain a positive electrode sheet. The purchased lithium titanium aluminum phosphate solid electrolyte powder (with a particle size D50 of 1 μm) was sprinkled on the surface of the positive electrode sheet, and the excess powder was scraped off with a scraper, and then it was roll-pressed twice at 120°C and 40 kN / cm with a roll press to obtain a composite cathode, which was cut into circular pieces with a diameter of 10 mm for standby. In this composite cathode, the thickness of the positive electrode coating is 5 μm, the thickness of the positive electrode mixed layer is 40 μm, and the thickness of the solid electrolyte layer is 1 μm.

[0084] (2) Preparation of the composite negative electrode: Artificial graphite (with a D50 particle size of 10 μm), conductive agent conductive carbon black, binder styrene-butadiene rubber, binder sodium carboxymethyl cellulose, and solvent water were stirred and mixed evenly according to a weight ratio of 94:1.5:1.5:3:40 to obtain the first slurry. The slurry was coated on a copper foil with a thickness of 8 μm and vacuum dried to obtain the negative electrode sheet. The purchased lithium titanium aluminum phosphate solid electrolyte powder (with a D50 particle size of 1 μm) was sprinkled on the surface of the negative electrode sheet, and the excess powder was scraped off with a spatula. Then, it was roll-pressed twice at 120 °C and 40 kN / cm with a roll press to obtain the composite negative electrode, which was cut into circular pieces with a diameter of 12 mm for standby. In this composite negative electrode, the thickness of the negative electrode coating is 3 μm, the thickness of the negative electrode mixed layer is 30 μm, and the thickness of the solid electrolyte layer is 1 μm.

[0085] (3) Preparation of the solid electrolyte sheet: The purchased lithium titanium aluminum phosphate solid electrolyte powder (with a D50 particle size of 1 μm) was pressed into a sheet with a thickness of 1000 μm at 150 MPa, and then sintered and polished to obtain a solid electrolyte sheet with a thickness of 500 μm.

[0086] (4) Preparation of the solid-state battery: In the order of composite positive electrode - solid electrolyte sheet - composite negative electrode, the prepared composite positive electrode, solid electrolyte sheet, and composite negative electrode were stacked and placed into a button battery case, and then pressed and encapsulated at 0.5 MPa with a sealer to complete the assembly of the button battery.

[0087] (5) Rate performance test: The above solid-state battery was charged at a constant current of 0.1C (current density of 0.15 mA / cm 2 ) to 4.2V and then at a constant voltage until cutoff at 0.01C within the working voltage range of 3V - 4.2V. Then, it was discharged to 3V at currents of 0.1C, 0.2C, 0.5C, and 1C respectively, and the specific capacities of the solid-state battery at discharge rates of 0.1C, 0.2C, 0.5C, and 1C were obtained respectively. The results are shown in Table 1.

[0088] Example 3

[0089] The composite positive electrode was prepared according to the method of Example 1, except that the roll-pressing conditions of the composite positive electrode were 120 °C and 40 kN / cm, and the rest were the same as those in Example 1. The obtained composite positive electrode was cut into circular pieces with a diameter of 10 mm for standby. In this composite positive electrode, the thickness of the positive electrode coating is 8 μm, the thickness of the positive electrode mixed layer is 42 μm, and the thickness of the solid electrolyte layer is 1.5 μm.

[0090] The preparation of the composite negative electrode, solid electrolyte sheet, and the assembly and rate performance test of the solid-state battery were carried out according to the method of Example 1. The results are shown in Table 1.

[0091] Example 4

[0092] According to the method of Example 1, except that in the composite positive electrode, the particle size D50 of the lithium aluminum titanium phosphate solid electrolyte powder is 8 μm, and the rest are the same as in Example 1, a solid-state battery is obtained.

[0093] The rate performance of the solid-state battery was tested according to the method of Example 1, and the results are shown in Table 1.

[0094] Comparative Example 1

[0095] According to the method of Example 1, except that in the preparation processes of the composite positive electrode and the composite negative electrode, the lithium aluminum titanium phosphate solid electrolyte powder was not added, and the rest were the same as in Example 1, a solid-state battery was obtained.

[0096] The rate performance of the solid-state battery was tested according to the method of Example 1, and the results are shown in Table 1.

[0097] Comparative Example 2

[0098] According to the method of Example 1, except that in the composite positive electrode, the particle size D50 of the lithium aluminum titanium phosphate solid electrolyte powder is 15 μm, and the rest are the same as in Example 1, a solid-state battery was obtained.

[0099] The rate performance of the solid-state battery was tested according to the method of Example 1, and the results are shown in Table 1.

[0100] Table 1

[0101]

[0102] It can be seen from the above results that the solid-state battery prepared by using the composite electrode provided by the present invention has a low interfacial impedance and a significantly improved rate performance.

[0103] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the technical concept scope of the present invention, various simple modifications can be made to the technical solutions of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A solid-state battery composite electrode, characterized in that, The composite electrode includes a current collector, an electrode coating disposed on the surface of the current collector, a solid electrolyte layer disposed on the surface of the electrode coating, and a mixed layer disposed between the electrode coating and the solid electrolyte layer; wherein, the electrode coating and the mixed layer contain electrode active materials, the solid electrolytes contained in the solid electrolyte layer and the mixed layer are both lithium aluminum titanium phosphate, and the particle size D50 of the solid electrolyte is smaller than the particle size D50 of the electrode active material; The difference in particle size D50 between the electrode active material and the solid electrolyte is 5 - 20 μm.

2. The composite electrode of the solid-state battery according to claim 1, wherein The electrode coating is a positive electrode coating or a negative electrode coating, and the thicknesses of the positive electrode coating and the negative electrode coating are the same or different, and are independently 2 - 10 μm; and / or, the solid electrolyte layer is a solid electrolyte layer I or a solid electrolyte layer II, and the thicknesses of the solid electrolyte layer I and the solid electrolyte layer II are the same or different, and are independently 0.3 - 5 μm; and / or, the mixed layer is a positive electrode mixed layer or a negative electrode mixed layer, and the thicknesses of the positive electrode mixed layer and the negative electrode mixed layer are the same or different, and are independently 5 - 250 μm.

3. The solid-state battery composite electrode according to claim 2, wherein, The thicknesses of the positive electrode coating and the negative electrode coating are the same or different, and are independently 3 - 8 μm; and / or, the thicknesses of the solid electrolyte layer I and the solid electrolyte layer II are the same or different, and are independently 0.5 - 1.5 μm; and / or, the thicknesses of the positive electrode mixed layer and the negative electrode mixed layer are the same or different, and are independently 10 - 150 μm.

4. The solid-state battery composite electrode according to claim 2, wherein, The electrode active material is a positive electrode material or a negative electrode material, and the positive electrode material is selected from at least one of LiCoO2, LiNiO2, LiNi x Co 1-x O2, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, LiNi 0.6 Co 0.2 Mn 0.2 O2, LiNi 0.8 Co 0.1 Mn 0.1 O2, LiNi 0.85 Co 0.1 Al 0.05 O2, LiMn2O4, LiNi 0.5 Mn 1.5 O4, a lithium-rich manganese-based positive electrode material, LiMPO4, and a sulfur electrode; in the LiNi x Co 1-x O2, 0 < x < 1; M in the LiMPO4 is Fe or Mn; The negative electrode material is selected from at least one of metallic lithium, lithium alloy, carbon-based material, silicon-based material, tin-based material, and lithium titanate; and / or, the current collector is a positive electrode current collector or a negative electrode current collector, the positive electrode current collector is aluminum foil; the negative electrode current collector is copper foil.

5. The solid-state battery composite electrode according to claim 4, wherein The positive electrode material is selected from LiCoO2, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, LiNi 0.6 Co 0.2 Mn 0.2 O2 and LiNi 0.8 Co 0.1 Mn 0.1 O2, at least one of them; and / or, the negative electrode material is selected from at least one of artificial graphite, silicon-carbon material, and silicon-oxygen material.

6. The composite solid-state battery electrode according to any one of claims 1-5, characterized in that The electrode coating and the mixed layer also contain a conductive agent and / or a binder; and / or, the conductive agent is a first conductive agent or a second conductive agent, and the first conductive agent and the second conductive agent are the same or different, and are independently selected from at least one of acetylene black, conductive carbon black, carbon nanotubes, graphene, and carbon fiber; and / or, the binder is a first binder or a second binder, and the first binder and the second binder are the same or different, and are independently selected from at least one of polyvinylidene fluoride, sodium carboxymethyl cellulose, styrene-butadiene rubber, and polyacrylic acid; and / or, the weight ratio of the positive electrode material, the first conductive agent, and the first binder is (80 - 95):(2 - 10):(3 - 10); and / or, the weight ratio of the negative electrode material, the second conductive agent, and the second binder is (80 - 95):(1.5 - 10):(4.5 - 10).

7. The composite electrode of the solid-state battery according to claim 4 or 5, characterized in that, The solid electrolyte layer I and the positive electrode mixed layer contain a first electrolyte, and the particle size D50 of the first electrolyte is smaller than the particle size D50 of the positive electrode material; the solid electrolyte layer II and the negative electrode mixed layer contain a second electrolyte, and the particle size D50 of the second electrolyte is smaller than the particle size D50 of the negative electrode material; the difference between the particle size D50 of the positive electrode material and the particle size D50 of the first electrolyte is 5 - 20 μm; the difference between the particle size D50 of the negative electrode material and the particle size D50 of the second electrolyte is 5 - 20 μm; both the first electrolyte and the second electrolyte are lithium aluminum titanium phosphate.

8. A method for preparing the solid-state battery composite electrode according to any one of claims 1-7, characterized in that, This method includes: Coating a slurry containing powder and a solvent on the surface of a current collector and drying it to obtain an electrode sheet, and then sprinkling a solid electrolyte on the surface of the electrode sheet and performing roll pressing; wherein, the powder includes an electrode active material, an optional conductive agent, and an optional binder.

9. The method according to claim 8, wherein The solvent is a first solvent or a second solvent, and the first solvent and the second solvent are the same or different, and each independently is selected from at least one of water, N-methylpyrrolidone, and ethanol; And / or, the weight ratio of the powder to the solvent is 100:(30 - 50).

10. The method according to claim 8 or 9, characterized in that, The conditions of the roll pressing include: the roll pressing pressure is 20 - 100 kN / cm; the roll pressing temperature is 60 - 200 °C; the number of roll pressing times is 1 - 5 times.

11. The method according to claim 10, wherein The roll pressing pressure of the roll pressing is 30 - 60 kN / cm; And / or, the roll pressing temperature of the roll pressing is 100 - 200 °C; And / or, the number of roll pressing times of the roll pressing is 2 - 3 times.

12. A solid-state battery, the solid-state battery comprising battery elements stacked thereon, each battery element including a positive electrode, a negative electrode, and a solid electrolyte sheet disposed between the positive electrode and the negative electrode, characterized in that, The positive electrode and the negative electrode are the solid-state battery composite electrodes described in any one of claims 1 - 7.

13. The solid-state battery according to claim 12, characterized in that, The positive electrode includes a positive electrode current collector, a positive electrode coating provided on the surface of the positive electrode current collector, a solid electrolyte layer I provided on the surface of the positive electrode coating, and a positive electrode mixed layer provided between the positive electrode coating and the solid electrolyte layer I; wherein, the positive electrode coating and the positive electrode mixed layer contain a positive electrode material, the solid electrolyte layer I and the positive electrode mixed layer contain a first electrolyte, and the particle size D50 of the first electrolyte is smaller than the particle size D50 of the positive electrode material; the difference between the particle size D50 of the positive electrode material and the particle size D50 of the first electrolyte is 5 - 20 μm; The negative electrode includes a negative electrode current collector, a negative electrode coating provided on the surface of the negative electrode current collector, a solid electrolyte layer II provided on the surface of the negative electrode coating, and a negative electrode mixed layer provided between the negative electrode coating and the solid electrolyte layer II; wherein, the negative electrode coating and the negative electrode mixed layer contain a negative electrode material, the solid electrolyte layer II and the negative electrode mixed layer contain a second electrolyte, and the particle size D50 of the second electrolyte is smaller than the particle size D50 of the negative electrode material; the difference between the particle size D50 of the negative electrode material and the particle size D50 of the second electrolyte is 5 - 20 μm; Both the first electrolyte and the second electrolyte are lithium aluminum titanium phosphate; The solid electrolyte sheet contains a third electrolyte, which is the same as or different from the first electrolyte and the second electrolyte; the third electrolyte is selected from at least one of NASICON-type solid electrolytes, LISICON-type solid electrolytes, perovskite-type solid electrolytes, garnet-type solid electrolytes, and chalcogenide solid electrolytes.

14. The solid-state battery according to claim 13, wherein, The third electrolyte is selected from at least one of NASICON-type solid electrolytes, perovskite-type solid electrolytes, and garnet-type solid electrolytes; and / or, the first electrolyte, the second electrolyte, and the third electrolyte are the same.

15. The solid-state battery according to claim 14, characterized in that, The third electrolyte is selected from lithium aluminum titanium phosphate.

16. The solid-state battery according to any one of claims 12-15, characterized in that, The thickness of the solid electrolyte sheet is 20 - 700 μm.

17. The solid-state battery according to claim 16, characterized in that, The thickness of the solid electrolyte sheet is 50 - 500 μm.

18. A method for preparing a solid-state battery according to any one of claims 12-17, characterized in that, The method includes: (1) Coating a first slurry containing a positive electrode material, a first solvent, an optional first conductive agent, and an optional first binder on the surface of a positive electrode current collector, and drying to obtain a positive electrode sheet. Then, spreading a first electrolyte on the surface of the positive electrode sheet and performing a first rolling to obtain a composite positive electrode; (2) Coating a second slurry containing a negative electrode material, a second solvent, an optional second conductive agent, and an optional second binder on the surface of a negative electrode current collector, and drying to obtain a negative electrode sheet. Then, spreading a second electrolyte on the surface of the negative electrode sheet and performing a second rolling to obtain a composite negative electrode; (3) Stacking the composite positive electrode, the solid electrolyte sheet containing the third electrolyte, and the composite negative electrode in sequence and performing pressing.

19. Application of the solid-state battery according to any one of claims 12 - 17 in energy storage devices, electric vehicles, and electronic products.

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