LATP-CeO2 composite oxide electrolyte, composite positive plate, solid-state battery and preparation method of solid-state battery

Abstract

The invention provides an LATP-CeO2 composite oxide electrolyte, a composite positive plate, a solid-state battery and a preparation method of the solid-state battery. The LATP-CeO2 composite oxide electrolyte is connected through a covalent bond between LATP and CeO2 to replace weak interaction of physical mixing, so that interface debonding and phase separation are avoided, the density of the electrolyte is improved, the situation that interface stripping is likely to occur in a traditional composite coating, and consequently interface impedance is increased is improved, and the service life of the electrolyte is prolonged. And the composite oxide electrolyte constructs a'fast ion conduction-oxygen vacancy regulation 'dual-function layered coating, realizes fast ion transmission and inhibition of dissolution of transition metal ions, gives consideration to both the ion transmission efficiency and the interface stability, and improves the cycle performance and the safety performance of the battery.

Description

Technical Field

[0001] This invention relates to the field of solid-state battery materials technology, and in particular to an LATP-CeO2 composite oxide electrolyte, a composite cathode, a solid-state battery, and a method for preparing the same. Background Technology

[0002] Lithium-ion batteries, with their high energy density, long cycle life, and low self-discharge rate, have become the core power source for portable electronic devices, electric vehicles, and large-scale energy storage systems. As application areas continue to expand and market demand continues to grow, higher requirements are being placed on battery energy density, power output, and lifespan. However, battery safety is increasingly becoming a key bottleneck restricting its further development, attracting significant attention from both the industry and consumers.

[0003] Currently, commercially available lithium-ion batteries primarily employ liquid electrolyte systems, typically composed of lithium salts (such as lithium hexafluorophosphate) dissolved in carbonate-based organic solvents. These organic solvents are highly volatile, have low flash points, and are flammable. Under abnormal conditions such as overheating, overcharging, internal short circuits, or mechanical abuse, they are highly susceptible to thermal runaway, leading to smoke, fire, or even explosion, posing significant safety hazards. Furthermore, the interfacial side reactions between the liquid electrolyte and highly active positive and negative electrode materials (especially high-energy-density positive electrodes such as high-nickel and lithium-rich manganese-based electrodes) are quite severe, continuously consuming active lithium and increasing interfacial impedance, limiting the battery's cycle life and operating temperature window (typically -20°C to 60°C). To improve safety, the industry has attempted improvements such as adding electrolyte additives, using high-concentration salts, or flame-retardant solvents. However, these methods often involve trade-offs in terms of cost, ionic conductivity, or electrochemical stability, making it difficult to fundamentally eliminate the inherent flammability risks of organic solvents.

[0004] To completely solve the safety issues posed by flammable electrolytes, all-solid-state lithium batteries are considered a crucial development direction for next-generation battery technology. These batteries completely replace liquid electrolytes with non-flammable inorganic solid electrolytes (such as oxides, sulfides, and polymers), theoretically greatly improving the intrinsic safety of the battery. Among them, oxide solid electrolytes have been extensively studied due to their good chemical stability, wide electrochemical window, and high mechanical strength. However, when directly applying oxide solid electrolytes to batteries, a prominent technical challenge lies in the solid-solid contact between them and the positive electrode active material particles. This poor interfacial contact and high impedance result in low ion transport efficiency, severely limiting the battery's rate capability and cycle performance. This problem is particularly pronounced for thick-load positive electrode sheets. Traditional solutions, such as coating the solid electrolyte, are often complex and costly.

[0005] Therefore, how to effectively improve the interfacial contact between the cathode and the solid electrolyte without introducing flammable components, and construct a cathode-electrolyte interface with high ion transport efficiency and excellent chemical stability, has become the key to developing high-performance and high-safety solid-state lithium batteries. Summary of the Invention

[0006] In view of this, the present invention proposes an LATP-CeO2 composite oxide electrolyte, a composite cathode, a solid-state battery, and a method for preparing the same. In the LATP-CeO2 composite oxide electrolyte, LATP and CeO2 are connected by covalent bonds, replacing the weak interactions of physical mixing, avoiding interfacial debonding and phase separation, thus improving electrolyte density. This improves the interfacial peeling that easily occurs in traditional composite coatings, leading to increased interfacial impedance. Furthermore, this composite oxide electrolyte constructs a bifunctional layered coating of "fast ion conduction-oxygen vacancy regulation," achieving rapid ion transport and suppressing the dissolution of transition metal ions, while simultaneously balancing ion transport efficiency and interfacial stability, thereby improving battery cycle life and safety performance.

[0007] The technical solution of this invention is implemented as follows: In a first aspect, the present invention proposes an LATP-CeO2 composite oxide electrolyte, the raw materials of which include LATP and CeO2.

[0008] The LATP-CeO2 composite oxide electrolyte proposed in this invention is formed by ball milling and sintering LATP and CeO2, resulting in local atomic rearrangement at the interface and the formation of Ce-O-Ti covalent bonds. This creates a stable interfacial connection and can suppress side reactions between LATP and the electrolyte (such as Li). + With PO4 3- (This reduces the loss of ions), and also improves the situation where traditional composite coatings are prone to interface peeling, leading to increased interface impedance. Furthermore, this composite oxide electrolyte constructs a dual-functional layered coating of "fast ion conduction-oxygen vacancy regulation," which enables rapid ion transport and inhibits the dissolution of transition metal ions, while taking into account both ion transport efficiency and interface stability. The uniform dispersion of CeO2 particles in the LATP matrix enhances the mechanical strength of the LATP-CeO2 composite oxide electrolyte, and the high melting point of CeO2 also contributes to the improvement of overall thermal stability, which is beneficial to improving the cycle and safety performance of the battery.

[0009] Based on the above technical solution, the mass ratio of LATP to CeO2 is further (8~10):1.

[0010] If the CeO2 content is too low, the number of Ce-O-Ti covalent bonds formed will be insufficient, which will not be able to completely cover the LATP particle interface, resulting in insufficient interface optimization; if it is too high, it will block the ion transport path of LATP, resulting in a decrease in ionic conductivity.

[0011] Secondly, the present invention also proposes a method for preparing LATP-CeO2 composite oxide electrolyte, comprising the following steps: S1, mixing the mixture of LATP and CeO2 with anhydrous ethanol, adding a dispersant and grinding to obtain a slurry; S2. After drying the slurry, grind it and sieve it to obtain powder; S3. The powder is sintered under an inert atmosphere to obtain the LATP-CeO2 composite oxide electrolyte.

[0012] This invention proposes a LATP-CeO2 composite oxide electrolyte prepared by ball milling and high-temperature sintering. During the ball milling stage, high-energy mechanical action refines the LATP and CeO2 particles to the nanoscale, increasing the particle surface area and transforming the interfacial contact from "point contact" to "surface contact." CeO2 nanoparticles are uniformly attached to the LATP surface, creating the necessary space for atomic-level reactions. Mechanical force induces defects such as lattice distortion, dislocations, and stacking faults. The atomic binding energy in these defective regions decreases, and the oxygen vacancy concentration surges, becoming "active sites" for subsequent bonding. Atoms on the particle surface detach from their original lattice due to mechanical force, resulting in insufficient coordination numbers and the formation of numerous "dangling bonds" (such as Ti-O- and Ce-O-). These unsaturated bonds are highly reactive and spontaneously seek stable bonding states, providing a suitable environment for CeO2 bonding during sintering. 4+ With Ti 4+ The foundation is laid through oxygen ion bridging.

[0013] During the sintering stage, high temperature drives Ce 4+ Lattice diffusion occurs, with Ti unsaturatedly coordinated to the LATP surface. 4 +Ce-O-Ti covalent bonds are formed through "oxygen ion bridges".

[0014] The LATP-CeO2 composite oxide electrolyte proposed in this invention has the ability to inhibit Li + / PO4 3- Dual protection against leakage: (1) Physical barrier: The Ce-O-Ti cross-linked network forms a dense three-dimensional skeleton, which reduces the porosity of the coating and the pore size, and can physically block the penetration of HF molecules and water molecules in the electrolyte, reducing the acid etching reaction on the LATP surface. (2) CeO2 has abundant surface oxygen vacancies, which can chemically adsorb PO4. 3- , forming a stable complex to prevent it from dissolving from the crystal lattice. (3) Ce 4+ / Ce 3+ The reversible valence transition provides additional electronic buffering, suppressing Ti 4+ Excessive reduction maintains lattice stability, thus avoiding damage caused by Ti. 4+ Reduction-induced LATP structural collapse and Li + Loss.

[0015] The LATP-CeO2 composite oxide electrolyte proposed in this invention synergistically improves electrolyte performance through interface reconstruction, electronic regulation, and structural optimization. LATP and CeO2 exhibit a lattice-matched transition layer buffering effect, which, through Ce… 4+ Doping on the LATP surface forms a transition layer, which reduces the lattice mismatch between LATP and CeO2 and significantly reduces interfacial stress.

[0016] The Ce-O-Ti covalent bonds firmly connect LATP to CeO2 particles, replacing the physical adsorption of traditional composite coatings. Compared with pure LATP, the interfacial shear strength is improved, effectively suppressing the delamination of "coating-positive electrode substrate" and "particles inside the coating" during cycling.

[0017] Under high-temperature sintering, the grain boundaries of LATP and CeO2 particles undergo local fusion, forming a continuous "grain boundary bridge," eliminating voids between particles and reducing the source of interfacial impedance.

[0018] The LATP-CeO2 composite oxide electrolyte proposed in this invention constructs a bifunctional layered coating with "fast ion conduction-oxygen vacancy regulation". (1) Construction of continuous ion channels: LATP is used as the main body of the composite coating, and its own three-dimensional perovskite structure provides inherent Li + Transport channels; CeO2 nanoparticles are uniformly dispersed in the LATP matrix without disrupting the continuity of LATP channels, while filling the micropores between LATP particles to form a "bulk channel-grain boundary channel" interconnected network. (2) Oxygen vacancy-assisted Li + Transport: CeO2 has unique Ce 4+ / Ce 3+ Valence state cycle characteristics; during ball milling sintering, some Ce... 4+ Reduced to Ce 3+ To maintain electroneutrality, a large number of oxygen vacancies are formed in the CeO2 lattice. These oxygen vacancies can act as Li... + The "temporary storage site" makes Li + The migration path changes from "continuous jumps" in LATP to a relay transport of "LATP channel → CeO2 oxygen vacancy → LATP channel", thus improving the room temperature ionic conductivity. (3) Oxygen vacancy buffering stabilizes the positive electrode lattice oxygen and avoids transition metal valence state distortion: CeO2 has unique Ce 3+ / Ce 4+ Reversible redox pairs naturally contain a large number of oxygen vacancies in their lattice, which can act as "oxygen buffers." Under high voltage, lattice oxygen loss easily occurs at the cathode, leading to the disruption of the transition metal coordination environment and a decrease in valence state (e.g., Ni). 3+ →Ni 2+Low-valence transition metals are more easily dissolved. Oxygen vacancies in CeO2 can be quickly adsorbed and replenished, stabilizing the cathode lattice and inhibiting the dissolution of transition metals.

[0019] Based on the above technical solutions, the sintering temperature is further specified as 900~1000℃ and the sintering time is further specified as 4~6h.

[0020] If the sintering temperature is too low, the interfacial bonding will be insufficient, and Li + / PO4 3- It is prone to loss; excessively high sintering temperature may cause Li to be lost. + It volatilizes, and its ionic conductivity decreases.

[0021] Based on the above technical solution, the mass ratio of the mixture to anhydrous ethanol is further 1:(1.2~2).

[0022] Based on the above technical solution, the dispersant is further described as having a mass fraction of 0.5% PVP.

[0023] Based on the above technical solution, the inert atmosphere is further defined as an argon atmosphere.

[0024] Thirdly, the present invention proposes a composite positive electrode sheet, the raw materials of which include a positive electrode roll and the LATP-CeO2 composite oxide electrolyte coated on the surface of the positive electrode roll.

[0025] Fourthly, the present invention proposes a method for preparing the composite positive electrode, comprising the following steps: S1, dissolving the binder and dispersant in a solvent, adding LATP-CeO2 composite oxide electrolyte, mixing well, and sieving to obtain a composite oxide electrolyte slurry; S2. After mixing the positive electrode material, binder, conductive agent and solvent, coat it onto aluminum foil, dry it and roll it to obtain the positive electrode roll; S3. The composite oxide electrolyte slurry is coated onto the surface of the positive electrode roll, dried, rolled and die-cut to obtain the composite positive electrode sheet.

[0026] Based on the above technical solutions, further, the thickness of the composite oxide electrolyte slurry coated in step S3 is 10~20μm.

[0027] If the coating is too thin, the protection is insufficient. A thin LATP-CeO2 coating is difficult to form a defect-free continuous film and is prone to pinholes and microcracks. If it is too thick, it will increase the interfacial impedance. When it is too thick, the ion transport path becomes longer and the ion transport efficiency decreases. A thick coating is prone to internal stress during drying, which leads to micro-gap between the coating and the positive electrode interface, resulting in increased contact impedance.

[0028] Based on the above technical solutions, further, the thickness of the composite oxide electrolyte slurry coated in step S3 is 10~14μm.

[0029] Based on the above technical solutions, further, the binder in steps S1 and S2 includes PVDF, the dispersant includes PVP, and the solvent in steps S1 and S2 includes NMP.

[0030] Based on the above technical solution, further, in step S1, the mass ratio of LATP-CeO2 composite oxide electrolyte, binder, and dispersant is (85~95):(8.5~10):(0.2~1).

[0031] Based on the above technical solutions, the cathode material further includes one or more of lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium manganese oxide, lithium cobalt oxide, lithium nickel manganese oxide, lithium iron phosphate, lithium manganese iron phosphate, and lithium-rich manganese-based materials.

[0032] Based on the above technical solutions, the conductive agent further includes one or more of SP (conductive carbon black), single-walled carbon nanotubes, multi-walled carbon nanotubes, Ketjen black, and acetylene black.

[0033] Fifthly, the present invention also proposes a solid-state battery comprising the composite positive electrode.

[0034] Compared with the prior art, the present invention has the following beneficial effects: The LATP-CeO2 composite oxide electrolyte proposed in this invention forms a stable Ce-O-Ti bond between LATP and CeO2, which suppresses the side reactions between LATP and the electrolyte. This improves the situation where traditional composite coatings are prone to interfacial delamination, leading to increased interfacial impedance. Furthermore, this composite oxide electrolyte constructs a bifunctional layered coating of "fast ion conduction-oxygen vacancy regulation", which realizes rapid ion transport and inhibits the dissolution of transition metal ions, while taking into account both ion transport efficiency and interfacial stability, thereby improving battery cycle and safety performance. Detailed Implementation

[0035] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0036] In the following specific embodiments, the method for preparing the negative electrode sheet includes: preparing a uniform slurry by mixing graphite, binder, thickener, and conductive agent with deionized water at a mass ratio of 96:2:0.5:1.5, then coating the slurry onto copper foil, drying it, rolling it, and die-cutting it to obtain the negative electrode sheet. The binder is styrene-butadiene rubber (SBR), the thickener is sodium carboxymethyl cellulose (CMC), and the conductive agent is conductive carbon black.

[0037] Example 1 This embodiment proposes an LATP-CeO2 composite oxide electrolyte, a composite positive electrode, and a method for preparing the same, wherein the mass ratio of LATP to CeO2 is 9:1.

[0038] The preparation method of LATP-CeO2 composite oxide electrolyte includes the following steps: S1, Preparation of LATP-CeO2 composite oxide electrolyte: Weigh 90g of LATP powder and 10g of CeO2 to obtain a mixture; Add the mixture and anhydrous ethanol to a ball mill jar at a mass ratio of 1:1.5, then add 0.5wt% PVP (dispersant), and ball mill at 400rpm for 6h to ensure that the powder is initially mixed without lumps, and obtain a slurry.

[0039] S2. The ball-milled slurry was vacuum dried at 60℃ for 8 hours to obtain loose powder. After grinding, the powder was sieved and then cold-pressed into blocks. The blocks were then sintered at 950℃ for 5 hours under an argon atmosphere to obtain LATP-CeO2 composite oxide electrolyte.

[0040] The method for preparing the composite positive electrode includes the following steps: S1. Add PVDF and PVP to NMP and stir to dissolve. Then add the LATP-CeO2 composite oxide electrolyte. The mass ratio of the LATP-CeO2 composite oxide electrolyte, binder, and dispersant is 90:9.5:0.5. The amount of NMP is 1.5 times the sum of the masses of PVDF, PVP, and LATP-CeO2. After stirring evenly, add an appropriate amount of NMP and control the slurry viscosity to 1000~3000 mPa·s. Then sieve to obtain the composite oxide electrolyte slurry. S2. Lithium nickel cobalt manganese oxide, PVDF, and conductive carbon black are mixed in a mass ratio of 96.5:1.5:2 and then formulated with NMP to prepare a slurry with a solid content of 68%. The slurry is then coated onto aluminum foil, dried, and rolled to obtain a positive electrode roll.

[0041] S3. The composite oxide electrolyte slurry is coated on the surface of the positive electrode roll with a thickness of 13 μm, and then rolled and die-cut to obtain the composite positive electrode sheet.

[0042] Example 2 This embodiment proposes an LATP-CeO2 composite oxide electrolyte, a composite positive electrode, and a method for preparing the same, wherein the mass ratio of LATP to CeO2 is 8:1.

[0043] The preparation method of LATP-CeO2 composite oxide electrolyte includes the following steps: S1, Weigh 80g of LATP powder and 10g of CeO2 powder to obtain a mixture; The mixture and anhydrous ethanol were added to a ball mill jar at a mass ratio of 1:1.2, followed by the addition of 0.5 wt% PVP (dispersant). The mixture was ball milled at 400 rpm for 6 hours to ensure that the powder was initially mixed without clumping, thus obtaining a slurry.

[0044] S2. The ball-milled slurry was vacuum dried at 60℃ for 8 hours to obtain loose powder. After grinding, the powder was sieved and then cold-pressed into blocks. The blocks were then sintered at 900℃ for 4 hours under an argon atmosphere to obtain LATP-CeO2 composite oxide electrolyte.

[0045] The method for preparing the composite positive electrode includes the following steps: S1. Add PVDF and PVP to NMP and stir to dissolve. Then add the LATP-CeO2 composite oxide electrolyte. The mass ratio of the LATP-CeO2 composite oxide electrolyte, binder, and dispersant is 85:8.5:0.2. The amount of NMP is 1.5 times the sum of the weights of PVDF, PVP, and LATP-CeO2. After stirring evenly, add an appropriate amount of NMP and control the slurry viscosity to 1000~3000 mPa·s. Then sieve to obtain the composite oxide electrolyte slurry. The mass ratio of the LATP-CeO2 composite oxide electrolyte, binder, and dispersant is 85:8.5:0.2.

[0046] S2. Lithium nickel cobalt aluminum oxide, PVDF, and conductive carbon black are mixed in a mass ratio of 96.5:1.5:2 and then formulated with NMP to prepare a slurry with a solid content of 68%. The slurry is then coated onto aluminum foil, dried, and rolled to obtain a positive electrode roll.

[0047] S3. The composite oxide electrolyte slurry is coated on the surface of the positive electrode roll with a thickness of 10 μm, and then rolled and die-cut to obtain the composite positive electrode sheet.

[0048] Example 3 This embodiment proposes an LATP-CeO2 composite oxide electrolyte, a composite positive electrode, and a method for preparing the same, wherein the mass ratio of LATP to CeO2 is 10:1.

[0049] The preparation method of LATP-CeO2 composite oxide electrolyte includes the following steps: S1, Weigh 100g of LATP powder and 10g of CeO2 powder to obtain a mixture; Add the mixture and anhydrous ethanol to a ball mill jar at a mass ratio of 1:2, then add 0.5wt% PVP (dispersant), and ball mill at 400rpm for 6h to ensure that the powder is initially mixed without lumps, and obtain a slurry.

[0050] S2. The ball-milled slurry was vacuum dried at 60℃ for 8 hours to obtain loose powder. After grinding, the powder was sieved and then cold-pressed into blocks. The blocks were then sintered at 1000℃ under an argon atmosphere for 6 hours to obtain LATP-CeO2 composite oxide electrolyte.

[0051] The method for preparing the composite positive electrode includes the following steps: S1. Add PVDF and PVP to NMP and stir to dissolve. Then add the LATP-CeO2 composite oxide electrolyte. The mass ratio of the LATP-CeO2 composite oxide electrolyte, binder, and dispersant is 95:10:1. The amount of NMP is 1.5 times the sum of the weights of PVDF, PVP, and LATP-CeO2. After stirring evenly, add an appropriate amount of NMP and control the slurry viscosity to 1000~3000 mPa·s. Then sieve to obtain the composite oxide electrolyte slurry. S2. Lithium manganese oxide, PVDF, and conductive carbon black are mixed in a mass ratio of 96.5:1.5:2 and then mixed with NMP to form a uniform slurry with a solid content of 68%. The slurry is then coated onto aluminum foil, dried, and rolled to obtain a positive electrode roll.

[0052] S3. The composite oxide electrolyte slurry is coated on the surface of the positive electrode roll with a thickness of 14 μm, and then rolled and die-cut to obtain the composite positive electrode sheet.

[0053] Example 4 This embodiment proposes an LATP-CeO2 composite oxide electrolyte, a composite positive electrode sheet, and a method for preparing the same. The difference from Embodiment 1 is that in the method for preparing the composite positive electrode sheet in this embodiment, the thickness of the composite oxide electrolyte slurry coated on the surface of the positive electrode roll is 20 μm.

[0054] Comparative Example 1 The difference between this comparative example and Example 1 is that the oxide electrolyte is pure LATP.

[0055] Comparative Example 2 The difference between this comparative example and Example 1 is that the mass ratio of LATP to CeO2 is 5:1.

[0056] Comparative Example 3 The difference between this comparative example and Example 1 is that the mass ratio of LATP to CeO2 is 20:1.

[0057] Comparative Example 4 The difference between this comparative example and Example 1 is that it does not contain LATP-CeO2 complex oxide electrolyte.

[0058] Comparative Example 5 The difference between this comparative example and Example 1 is that in the preparation method of the LATP-CeO2 composite oxide electrolyte, the sintering temperature in step S2 is 800℃.

[0059] Comparative Example 6 The difference between this comparative example and Example 1 is that in the preparation method of the LATP-CeO2 composite oxide electrolyte, the sintering temperature in step S2 is 1100℃.

[0060] Comparative Example 7 The difference between this comparative example and Example 1 is that in the preparation method of the composite positive electrode, step S3 involves coating the composite oxide electrolyte slurry onto the surface of the positive electrode roll with a thickness of 1 μm.

[0061] Comparative Example 8 The difference between this comparative example and Example 1 is that in the preparation method of the composite positive electrode, step S3 involves coating the composite oxide electrolyte slurry onto the surface of the positive electrode roll with a thickness of 30 μm.

[0062] Performance testing The composite positive electrode, negative electrode, and separator prepared in Examples 1-4 and Comparative Examples 1-8 were assembled into a battery cell. After the moisture content was qualified by baking, a polymer electrolyte precursor solution was injected, followed by impregnation, curing, formation, secondary sealing, and capacity testing to obtain a solid-state battery. Battery performance tests were conducted on the solid-state battery according to GB+43854-2024. The test methods are shown below, and the test results are shown in Tables 1 and 2.

[0063] (1) Needle prick test: ① Charge at 0.5C constant current and constant voltage to the upper voltage limit, cut off current 0.05C, and let stand for 1 hour; ② Use a 5mm high-temperature resistant steel needle (the cone angle of the needle tip is 45°, the surface of the needle is smooth, free of rust, oxide layer and oil stains), and penetrate from the direction perpendicular to the battery cell plate at a speed of (25±5)mm / s. The penetration position should be close to the geometric center of the pierced surface. The steel needle stays in the battery cell for 1 hour for observation. (2) Cyclic performance test: Charge the battery at 0.5C constant current and constant voltage to the upper voltage limit, cut off the current at 0.05C, let it stand for 30 minutes, discharge at 1C constant current to the lower voltage limit, let it stand for 30 minutes, repeat 500 cycles, and calculate the discharge capacity retention rate.

[0064] Table 1. Needle prick test results of the examples and comparative examples.

[0065] Table 2 Cyclic performance test results of the examples and comparative examples

[0066] As shown in Tables 1 and 2, the LATP-CeO2 composite oxide electrolyte proposed in this invention greatly improves the stability of the positive electrode and the safety performance of the battery cell. The solid-state battery prepared has good cycle performance and does not catch fire or explode during the nail penetration test.

[0067] As can be seen from the comparison between Example 1 and Comparative Example 1, the absence of CeO2 leads to a significant decrease in cycle performance.

[0068] As can be seen from the comparison between Example 1 and Comparative Examples 2 and 3, an excessively high or low proportion of CeO2 will affect ion conduction, thereby leading to a decrease in cycle performance. A comparison of Example 1 and Comparative Example 4 shows that the oxide-free electrolyte coating results in insufficient safety protection. As can be seen from the comparison between Example 1 and Comparative Example 5, due to the insufficient bonding caused by the sintering temperature being too low, LATP and CeO2 are simply physically mixed, and the structure and performance do not meet the standards. A comparison of Example 1 and Comparative Example 6 shows that the excessively high sintering temperature led to structural damage and also caused Li... + Volatilization leads to a decrease in ionic conductivity and performance degradation. A comparison of Example 1 and Comparative Example 7 shows that the composite oxide electrolyte coating is too thin to form a safety protection. As can be seen from the comparison between Example 1 and Comparative Example 8, an excessively thick composite oxide electrolyte coating will lead to increased impedance, thereby reducing cycle performance.

[0069] In summary, by using the LATP-CeO2 composite oxide electrolyte proposed in this invention to coat the positive electrode, a composite positive electrode sheet was obtained. This constructed a composite coating in the solid-state battery that balances ion transport efficiency and interface stability, thereby improving the battery's cycle performance and safety performance.

[0070] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A LATP-CeO2 composite oxide electrolyte, characterized in that, The raw materials include LATP and CeO2.

2. The LATP-CeO2 composite oxide electrolyte as described in claim 1, characterized in that, The mass ratio of LATP to CeO2 is (8~10):

1.

3. The method for preparing the LATP-CeO2 composite oxide electrolyte according to any one of claims 1 to 2, characterized in that, The process includes the following steps: S1, mixing the mixture of LATP and CeO2 with anhydrous ethanol, adding a dispersant and grinding to obtain a slurry; S2. After drying the slurry, grind it and sieve it to obtain powder; S3. The powder is sintered under an inert atmosphere to obtain the LATP-CeO2 composite oxide electrolyte.

4. The preparation method of the LATP-CeO2 composite oxide electrolyte as described in claim 3, characterized in that, The sintering temperature is 900~1000℃ and the time is 4-6h.

5. A composite positive electrode, characterized in that, The raw materials include a positive electrode roll and an LATP-CeO2 composite oxide electrolyte as described in any one of claims 1 to 2 coated on the surface of the positive electrode roll.

6. The method for preparing the composite positive electrode sheet as described in claim 5, characterized in that, The process includes the following steps: S1, dissolving the binder and dispersant in a solvent, adding the LATP-CeO2 composite oxide electrolyte, mixing well, and then sieving to obtain a composite oxide electrolyte slurry; S2. After mixing the positive electrode material, binder, conductive agent and solvent, coat it onto aluminum foil, dry it and roll it to obtain the positive electrode roll; S3. The composite oxide electrolyte slurry is coated onto the surface of the positive electrode roll, dried, rolled and die-cut to obtain the composite positive electrode sheet.

7. The method for preparing the composite positive electrode sheet as described in claim 6, characterized in that, In step S3, the thickness of the composite oxide electrolyte slurry coated is 10-20 μm.

8. The method for preparing the composite positive electrode sheet as described in claim 6, characterized in that, The binder in steps S1 and S2 includes PVDF, the dispersant includes PVP, and the solvent in steps S1 and S2 includes NMP.

9. The method for preparing the composite positive electrode sheet as described in claim 8, characterized in that, In step S1, the mass ratio of LATP-CeO2 composite oxide electrolyte, binder, and dispersant is (85~95):(8.5~10):(0.2~1).

10. A solid-state battery, characterized in that, It includes the composite positive electrode sheet as described in claim 5.

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