High-rate, long-cycle, and high-safety positive electrode plate for lithium batteries, its manufacturing method, and use.

Abstract

The present invention discloses a positive electrode plate for a lithium battery and a method for manufacturing the same. The positive electrode plate of the present invention includes a positive electrode material layer and a functional layer located directly on the positive electrode material layer, the functional layer material including component 1, and component 1 is Li 1-x1 Ti 1-x1 A x1 OPO4, Li 1-x1 Ti 1-x1 A x1 PO5, Li 2-y1 Ti 1-y1 A y1 OM1O4, Li 2-y1 Ti 1-y1 A y1 M1O5, where 0≦x1≦0.7, 0≦y1≦1, A is at least one selected from Nb, Ta, and Sb, and M1 is at least one selected from Si and Ge. The functional layer material further includes component 2, which is LiM22(PO4)3, Li 1+x2 Al x2 M2 2-x2 (PO4)3, M2O2, Li 16-4y2 M2 y2 M2 is at least one selected from Ti, Ge, Zr, and Hf, or a combination of at least one selected from O8, M2P2O7, M3PO4, M32SiO5, M43(PO4)2, and M42SiO4, where M2 is at least one selected from Ti, Ge, Zr, and Hf,

Description

Cross-reference to related applications

[0001] This application claims the benefit of Chinese Patent Application No. 202210113785.8 filed on January 30, 2022, the content of which is incorporated herein by reference.

Technical Field

[0002] The present invention relates to the technical field of lithium batteries, and particularly relates to a positive electrode plate for a lithium battery with high rate, long cycle, and high safety, a manufacturing method thereof, and its use.

Background Art

[0003] Lithium-ion batteries have advantages such as high energy density, good cycle characteristics, long service life, low self-discharge, and no memory effect. In energy storage, power batteries, 3C electronics, etc., the application market is gradually becoming wider, and the future of the application can be expected.

[0004] Lithium batteries are gradually increasing in energy density and providing better endurance for power electronics products such as electric vehicles and digital products. Increasing the loading amount and compression density of the electrode plate, especially the positive electrode plate, is an effective method to increase the energy density of the battery. However, with the improvement of the loading amount and compression density of the positive electrode plate, the positive electrode active material layer becomes thicker and the porosity decreases, making it difficult for lithium ions to transport in the positive electrode plate, resulting in serious polarization of the battery, a decrease in the discharge specific capacity and rate characteristics of the battery, and a decrease in cycle stability. Also, as the energy density of the battery increases, it tends to be difficult to ensure the safety of the battery. There has been no technology that can solve these problems simultaneously.

[0005] Existing methods for improving the rate characteristics of batteries are as follows.

[0006] Positive electrode surface doping: The invention application with publication number CN113224287A discloses a strontium-doped ternary lithium-ion battery positive electrode material (Li 1-x Sr x[Ni 1-y-z Co y M z O₂, where M is one of the metals Mn and Al, 0 < x ≤ 0.1, 0 < y ≤ 1, 0 < z ≤ 1), its manufacturing method, and its use are disclosed. By doping strontium metal ions to replace lithium sites, the degree of cation mixing is reduced, the lithium ion channels are expanded, the layered structure is stabilized, and the rate performance of the lithium battery is effectively improved. However, this method often brings the problem of accelerating the capacity decay of the material while improving the rate performance.

[0007] Existing methods to improve the safety of the battery are as follows.

[0008] Positive electrode coating: The invention application with publication number CN113809280A discloses a positive electrode material, its manufacturing, and its use, which manufactures a positive electrode material having a substantially planar coating effect by changing sintering technical means and utilizing the interaction of coating agents. The positive electrode material manufactured by this method has a wide coating range of the surface coating layer, greatly reduces the degree of erosion of material particles by the electrolyte, effectively reduces the occurrence probability of side reactions, and improves the safety of the material. However, it has the disadvantages that the process of the method is complex and it affects the rate performance of the battery.

[0009] Use of electrolyte additives: The invention application with publication number CN113690490A discloses a phosphite-based electrolyte additive for lithium-ion batteries that can effectively prevent the combustion and explosion of organic solvents, enhance the thermal stability of the electrolyte itself, enhance the stability of the positive electrode, and improve the cycle stability and safety of the battery. It has the disadvantage of impairing the electrical properties of the battery such as cycle characteristics and rate characteristics.

[0010] Adhesive application to separator: The invention application, publication number CN108963153B, discloses a separator for lithium-ion batteries and a method for manufacturing the same. By coating at least one surface of a base film layer with an aqueous ceramic slurry coating, and then coating the aqueous ceramic slurry coating and / or the surface of the base film layer with a composite adhesive layer of polyethylene glycol and polymethyl methacrylate, the resulting lithium-ion battery separator has good adhesive properties, prevents short circuits due to electrode misalignment, improves battery hardness, and significantly enhances battery safety. However, it has the disadvantage of impairing the battery's rate characteristics.

[0011] Existing methods to improve both the electrical characteristics and safety of batteries are as follows:

[0012] CN108365260B discloses a semi-solid electrolyte comprising a polymer, a ceramic electrolyte, a lithium salt, and an ionic liquid as raw material components. The ceramic electrolyte comprises a main phase of lithium titanium aluminum phosphate and a heterophase of TiP2O7 / TiO2. Preferably, the heterophase content in the ceramic electrolyte is 2-7%, and the mass ratio of TiP2O7 to TiO2 is 1.5-2.5:1. The overall properties of a semi-solid electrolyte manufactured using a ceramic electrolyte with the heterophase content described above are optimal. The heterophase having the special composition and content has lithium storage properties and can improve lithium ion transportability, as well as reduce contact between the main phase of lithium titanium aluminum phosphate and metallic lithium, thereby improving interfacial stability with metallic lithium. However, this patent does not improve the electrical properties and safety of the positive electrode, and the method is incompatible with existing mainstream manufacturing processes for lithium-ion battery positive electrode plates and is not suitable for large-scale applications.

[0013] CN113707880A relates to a positive electrode plate containing a solid electrolyte, a method for manufacturing the same, and its use, aiming to improve the rate characteristics of a battery and enhance the cycle characteristics and safety. The solid electrolyte contained in the positive electrode slurry facilitates the permeation and infiltration of the electrolyte in the lateral and longitudinal directions of the electrode plate, and also facilitates the storage and infiltration of the electrolyte. Therefore, during the cycling of the cell, it alleviates the expansion of the electrode plate, reduces the amount of electrolyte extruded under pressure during the expansion process of the electrode plate, enables the electrode plate to contain a rich electrolyte even after long-term cycling, ensures the normal transport of lithium ions, and can improve the cycle characteristics. However, judging from the data of the examples, there is only a slight increase in battery capacity and safety, and the effect on rate characteristics lacks data support. It has been found that adding conventional solid electrolytes cannot achieve the goal of comprehensively improving the electrical characteristics and safety of the battery.

[0014] Therefore, it is necessary to find a method with simple steps and low cost while improving the electrical characteristics and safety of the battery.

Summary of the Invention

[0015] In view of the limitations existing in the above prior art, the present invention provides a positive electrode plate for a lithium battery with high rate, long cycle, and high safety, a method for manufacturing the same, and its use. The positive electrode plate of the present invention includes a positive electrode material layer and a functional layer located directly above the positive electrode material layer.

[0016] The functional layer material contains Component 1, and Component 1 is at least one selected from Li 1-x1 Ti 1-x1 A x1 OPO4, Li 1-x1 Ti 1-x1 A x1 PO5, Li 2-y1 Ti 1-y1 A y1 OM1O4, Li 2-y1 Ti 1-y1 A y1 M1O5, where 0 ≤ x1 ≤ 0.7, 0 ≤ y1 ≤ 1, A is at least one selected from Nb, Ta, Sb, and M1 is at least one selected from Si and Ge. Component 1 is preferably at least one of LiTiOPO4, Li 0.9 Nb 0.1 Ti 0.9 OPO4, Li 0.9 Ta 0.1 Ti 0.9 OPO4, Li2TiOSiO4, LiTaOGeO4.

[0017] The functional layer material contains Component 2, and Component 2 is at least one or a combination of a plurality of selected from LiM22(PO4)3, Li 1+x2 Al x2 M2 2-x2 (PO4)3, M2O2, Li 16-4y2 M2 y2 O8, M2P2O7, M3PO4, M32SiO5, M43(PO4)2, M42SiO4, where M2 is one selected from Ti, Ge, Zr, and Hf, where 0 < x2 < 0.6, and M3 and M4 are one of Al, Ga, Sc, Y, Ca, Sr, Zn, Si, In, Lu, La, Fe, Cr, Ge, where 3 < y2 < 4. Component 2 is preferably one of InPO4, LATP, AlPO4, LAGP, LATP + AlPO4, LAGP + Al2SiO5, InPO4 + LATP, Al2SiO5, TiO2 + LiTi2(PO4)3, TiP2O7 + LiGe2(PO4)3.

[0018] In the functional layer, the form of the mixed component composed of Component 1 and Component 2 is such that the particles of Component 1 and the particles of Component 2 are uniformly mixed with each other, or each primary particle contains the crystal form of Component 1 and the crystal form of Component 2.

[0019] The functional layer has a porous structure with a porosity of p (20% ≤ p ≤ 80%) and a thickness of h (0 μm < h ≤ 10 μm).

[0020] The particle size of Component 1 is 10 nm to 10 μm. Preferably, it is 50 nm to 1 μm.

[0021] The particle size of component 2 is 10 nm to 10 μm. Preferably, it is 50 nm to 1 μm.

[0022] Preferably, the positive electrode active material particles are at least one selected from lithium cobalt oxide positive electrode and its modified material, NCM ternary positive electrode and its modified material, NCA ternary positive electrode and its modified material, lithium nickel manganate positive electrode and its modified material, lithium-rich positive electrode and its modified material, lithium iron phosphate positive electrode and its modified material. The conductive agent is at least one selected from Super-P, KS-6, carbon black, nanocarbon fiber, carbon nanotube, acetylene black, or graphene. The binder is selected from polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polytetrafluoroethylene, homopolymers, copolymers, modified compounds of the above polymers, or mixtures of the above polymers with other polymers or small molecules.

[0023] A second object of the present invention is to provide a method for manufacturing a positive electrode plate for a lithium battery according to the first object of the present invention, wherein the component 1 or a mixed component of component 1 and component 2 is coated onto the positive electrode surface to form a functional layer on the surface of the positive electrode material layer. The surface coating of the positive electrode plate includes a slurry of component 1 or a mixed component of component 1 and component 2, and since the electrode plate has a porous structure, when component 1 or a mixed component of component 1 and component 2 is coated onto the positive electrode surface by the coating process, in addition to forming a coating on the surface of the positive electrode, some particles penetrate and disperse between the positive electrode active material particles.

[0024] Preferably, the manufacturing method is Step 1 for manufacturing the positive electrode active layer, Step 2 involves uniformly mixing component 1 or a mixture of component 1 and component 2 with a solvent and grinding it to form a slurry of 10 nm to 10 μm, Step 3 involves adding a binder to the slurry obtained in Step 2 and mixing it uniformly to produce a coating slurry. Step 4 includes applying the slurry obtained in Step 3 onto the positive electrode active layer and drying it to obtain a positive electrode plate.

[0025] Preferably, In step 2, the solvent in the slurry is at least one of the following: deionized water, ethanol, NMP, alcohol, isopropanol, and acetone. The mass ratio of the solvent to the positive electrode material is (2000~10):100.

[0026] In step 4, The aforementioned forced-air drying is performed at a temperature of 80-180°C for 10 minutes to 9 hours, while the vacuum drying is performed at a temperature of 80-180°C for 3 to 100 hours.

[0027] A third object of the present invention is to provide the use of the positive electrode plate described in the first object of the present invention in a lithium battery.

[0028] The lithium battery is either a liquid battery or a solid battery.

[0029] In this invention, by coating the surface of the positive electrode plate with a functional layer containing component 1 or a mixture of component 1 and component 2 with a particle size D50 of 0.01 to 10 μm, the rate characteristics, cycle characteristics, and safety of the battery can be improved. In the prior art, component 1 is a heterophase generated during the sintering process of the solid electrolyte, and the presence of such a heterophase reduces the ionic conductivity of the solid electrolyte, so it needs to be removed when manufacturing the solid electrolyte. In other words, it is generally thought that such a component cannot be used in solid electrolytes due to its extremely low ionic conductivity. However, through a large number of tests, the inventors have found that the ionic conductivity of such a component is relatively low, and is 10 μm, which is the ionic conductivity of a typical solid electrolyte. -4 It is much smaller than S / cm, and even smaller than the ionic conductivity of electrolytes, which is 10 -2We discovered that although component 1, which is smaller than S / cm, does not directly contribute to ionic conductivity after mixing with the electrolyte, adding it to the positive electrode can significantly improve the positive electrode's rate characteristics, cycle characteristics, and safety. Since component 1's specific chemical composition can contribute to the formation of surface CEI on the positive electrode material, we believe it can alter the CEI composition to make it more stable, avoiding CEI rupture and the resulting battery polarization and thermal runaway, and further improving the positive electrode plate's rate characteristics, cycle characteristics, and safety during actual battery operation. Furthermore, since component 2 can suppress the decomposition of the electrolyte and the formation of insulating components on the positive electrode material surface, using components 2 and 1 simultaneously produces a synergistic effect, creating a superior CEI and simultaneously and comprehensively improving the battery's electrical characteristics and safety. In particular, when component 1 or a mixture of component 1 and component 2 forms a coating on the electrode plate surface, the coating not only separates the positive and negative electrodes and prevents short circuits inside the battery, but also improves the CEI of the positive electrode surface layer, thereby improving lithium ion conduction in the direction parallel to the positive electrode surface and reducing electrolyte decomposition on the positive electrode surface. Since the positive electrode surface is the area with the most sufficient contact with the electrolyte, protecting the positive electrode surface can improve the overall and most effective characteristics of the battery. Introducing additives to the positive electrode through surface coating helps to improve the battery's rate characteristics without changing the current mainstream manufacturing processes for positive electrodes, separators, and batteries, and offers the advantages of high stability and low cost, making it suitable for large-scale applications.

[0030] The present invention has the following advantages and remarkable effects compared to the prior art.

[0031] The component 1 or mixed component particles of component 1 and component 2 in the surface functional layer of the lithium battery positive electrode of the present invention have high chemical stability and can be added to the positive electrode by surface coating after the manufacturing of the positive electrode plate. This does not change the mainstream manufacturing processes of conventional positive electrode plates, separators, and batteries, and is compatible with the mainstream manufacturing processes of existing lithium-ion battery positive electrode plates. It does not affect the manufacturing processes of the positive electrode and cell, and has the advantages of high stability and low cost, making it suitable for large-scale applications. On the other hand, methods of doping positive electrode materials or coating positive electrode surfaces both require changes to the manufacturing technology of existing positive electrode materials, and it is difficult to improve the discharge ratio capacity and rate characteristics. Component 1, added to the positive electrode plate for lithium batteries in this invention, differs from conventional solid electrolytes in its low lithium ion conductivity. In the prior art, it was common to select additive components with high lithium ion conductivity to improve the electrical characteristics of batteries. However, we have discovered that creatively adding particles with low lithium ion conductivity, such as component 1, to the positive electrode can significantly improve the battery's rate characteristics, cycle characteristics, and safety by improving the surface CEI of the positive electrode particles, thereby overcoming existing technical biases.

[0032] The mixed component particles of component 1 and component 2, simultaneously added to the positive electrode plate for lithium batteries according to the present invention, improve the stability of the positive electrode particle surface CEI, suppress oxygen release from the positive electrode and reaction with the electrolyte during thermal runaway, suppress electrolyte decomposition, and improve the electrical characteristics and safety of the battery. Experiments have demonstrated that the synergistic effect is better when component 1 and component 2 are used simultaneously.

[0033] Component 1, or a mixture of Component 1 and Component 2, forms a safety coating on the surface of the positive electrode plate, separating the positive and negative electrodes and enhancing the safety of the battery. Batteries with this safety coating have been experimentally proven not to ignite or explode in hot box tests because the safety coating separates the positive and negative electrodes and prevents short circuits. The safety coating not only separates the positive and negative electrodes and prevents short circuits inside the battery, but also improves the CEI of the positive electrode plate surface layer, thereby improving lithium ion conduction in the direction parallel to the positive electrode plate surface and reducing electrolyte decomposition on the positive electrode plate surface. This is because the positive electrode plate surface is the area with the most sufficient contact with the electrolyte, and protecting the positive electrode plate surface can most effectively improve battery characteristics.

[0034] The porosity of the functional layer of the positive electrode plate for lithium batteries of the present invention is specially designed; if the porosity is less than 20%, it is detrimental to the battery's rate characteristics, and if the porosity exceeds 80%, it is detrimental to the battery's cycle characteristics. The thickness of the functional layer is also specially designed; if the coating thickness is greater than 10 μm, it is detrimental to the battery's rate characteristics.

[0035] The positive electrode exhibits excellent rate characteristics, cycle characteristics, and safety. [Brief explanation of the drawing]

[0036] [Figure 1] This is a schematic diagram of the structure of the positive electrode plate for the lithium battery in Example 1. [Figure 2] This is a schematic diagram of the structure of the positive electrode plate for the lithium battery in Example 2. [Figure 3] This is a schematic diagram of the heavy impact test according to the present invention. [Figure 4] This is a schematic diagram of the structure of the positive electrode plate for the lithium battery in Example 9. [Modes for carrying out the invention]

[0037] The present invention will be described in detail below with reference to specific drawings and embodiments. The following embodiments are for further explanation of the present invention and should not be understood as limiting the scope of protection of the present invention. Non-essential improvements and modifications of the present invention made by those skilled in the art based on the content of the present invention also fall within the scope of protection of the present invention. Example 1

[0038] Step 1: A NCM cathode active layer was manufactured, and the mass of the active material was set to 100g. Step 2: Component 1 LiTiOPO4 and Component 2 Li 1.4 Al 0.4 Ti 1.6 A mixture of 25 kg of (PO4)3 and 500 kg of NMP was uniformly mixed and pulverized to obtain a slurry with a D50:300 nm. The ratio of component 1 to component 2 was 1:4. Step 3: 1 kg of PVDF was added to the slurry obtained in Step 2 and mixed uniformly to produce a coating slurry with a viscosity of 200 mPa·S. Step 4: The slurry obtained in Step 3 was applied to the NCM90 cathode active layer and baked to obtain a cathode plate with a coating thickness of 1 μm and a porosity of 40%. The positive electrode plate for the lithium battery manufactured by the above method, as shown in the schematic structural diagram of Figure 1, includes a current collector 5, a positive electrode material layer located on the current collector 5, and a functional layer 3 located directly above the positive electrode material layer. The positive electrode material layer includes a positive electrode active material 4, a conductive agent, and a binder. The functional layer 3 includes particles 1 of component 1 and particles 2 of component 2. Here, the particles of component 1 and component 2 in the functional layer 3 are uniformly distributed, and some of the particles of component 1 and component 2 are diffused within the positive electrode material layer and distributed among the particles of the positive electrode active material 4. The positive electrode plate and the SiOC650 negative electrode were combined to assemble a soft pack lithium battery. After processes such as liquid injection, chemical conversion, and capacity grading were performed on the lithium battery manufactured as described above, electrochemical tests and safety tests were conducted, respectively. The specific test results for electrochemical properties are shown in Table 1, and the safety test results are shown in Table 2. The test method for the electrochemical properties of the lithium battery used in this invention is as follows. 1. Testing cycle characteristics a) At 23℃±2℃, charge with a constant current of 1C until the charging termination voltage is reached, then switch to constant voltage charging. When the charging current rate drops to 0.05C, stop charging and leave for 1 hour. b) Discharge the battery at a constant current of 1C until it reaches the discharge termination voltage, then stop the discharge, record the discharge capacity, and this completes one cycle. c) Repeat steps a and b until the discharge capacity falls below 80% of the discharge capacity of the first cycle, and record the total number of battery cycles at that point. 2. Rate Test a) Charge the batteries at 23℃±2℃ at rates of 0.1C, 0.2C, 0.33C, 1C, 2C, and 3C, respectively, until they reach the charging termination voltage. Then discharge them at the same rate current until they reach the discharge termination voltage, performing four cycles at each rate. b) Record the discharge capacity at each rate. c) Calculate the ratio of the 2C or 3C discharge capacity to the 0.33C discharge capacity, express it as 2C / 0.33C or 3C / 0.33C, and evaluate the rate characteristics. 3. High-temperature cycle a) At 45°C, constant current charging is performed at a current of 1C until the charging termination voltage is reached, then the system switches to constant voltage charging, and charging stops when the charging current rate drops to 0.05C. b) Leave the battery undisturbed at 45°C for 5 hours. c) Under high temperature conditions of 45°C, discharge the battery at a constant current of 1C until the discharge termination voltage is reached, then stop the discharge, record the discharge capacity, and this completes one cycle. d) Repeat steps a to c until the discharge capacity falls below 80% of the discharge capacity of the first cycle, and record the battery's discharge capacity and the total number of cycles at that point. The safety testing methods for lithium-ion batteries are as follows: 1. Overcharging a) At 23℃±2℃, charge with a constant current of 1C until the charging termination voltage is reached, then switch to constant voltage charging. When the charging current rate drops to 0.05C, stop charging and leave for 1 hour. b) Continue charging the battery with a constant current of 1C until thermal runaway occurs, and record the voltage value of the battery when thermal runaway begins. 2. Hotbox a) At 23℃±2℃, charge with a constant current of 1C until the charging termination voltage is reached, then switch to constant voltage charging. When the charging current rate drops to 0.05C, stop charging and leave for 1 hour. b) Place the battery in the test box. Heat the test box at a rate of 5°C / min until the temperature inside the box reaches 160°C ± 2°C, then maintain a constant temperature for 1 hour. The battery will pass if it does not emit smoke, catch fire, or explode; otherwise, it will fail. 3.Falling a) At 23℃±2℃, charge with a constant current of 1C until the charging termination voltage is reached, then switch to constant voltage charging. When the charging current rate drops to 0.05C, stop charging and leave for 1 hour. b) A sample is dropped from a height of 1 meter onto a concrete slab. Each side of the soft pack battery will be dropped once, for a total of six tests. After six experiments, the battery will pass if it does not smoke, catch fire, or explode; otherwise, it will fail. 4. Impact from heavy objects a) At 23℃±2℃, charge with a constant current of 1C until the charging termination voltage is reached, then switch to constant voltage charging. When the charging current rate drops to 0.05C, stop charging and leave for 1 hour. b) A battery 8 is placed on the surface of the platform, a metal rod 9 with a diameter of 15.8 mm ± 0.2 mm is placed horizontally on the top surface of the geometric center of the battery, and a heavy object with a mass of 9.1 kg ± 0.1 kg is dropped from a height of 610 mm ± 25 mm into the surface of the battery on which the metal rod is placed, and the test is observed for 6 hours. A schematic diagram of the heavy object impact test is shown in Figure 3, where 5 is a towing rope, 6 is a guide pipe, and 7 is a steel impact box (hinged door is not shown). The impact test will be performed only on a wide surface of the soft pack battery, and each sample will be subjected to only one impact test. The battery will pass if it does not emit smoke, catch fire, or explode; otherwise, it will fail. 5. Piercing a) At 23℃±2℃, charge with a constant current of 1C until the charging termination voltage is reached, then switch to constant voltage charging. When the charging current rate drops to 0.05C, stop charging and leave for 1 hour. b) Using a φ8mm high-temperature resistant steel needle (with a conical angle of 45° at the tip, a glossy surface, and no rust, oxide layer, or oil stains), the needle is inserted at a speed of 25 mm / s from a direction perpendicular to the battery plates, at the geometric center of the surface into which the battery is inserted, leaving the steel needle inside the battery. c) Observe for 1 hour. The battery will pass if it does not emit smoke, catch fire, or explode; otherwise, it will fail. Example 2

[0039] Except for changing the 25 kg mixed component, which consists of component 1 and component 2, to one containing only 25 kg of component 1 and excluding component 2, changing the positive electrode active material to NCM83, and changing the battery structure to NCM83||SiOC650, all other parameters were kept the same as in Example 1. The manufactured lithium battery positive electrode plate, as shown in the schematic structural diagram in Figure 2, includes a current collector 5, a positive electrode material layer located on the current collector 5, and a functional layer 3 located directly above the positive electrode material layer. The positive electrode material layer includes a positive electrode active material 4, a conductive agent, and a binder, and the functional layer 3 includes particles 1 of component 1, where the particles of component 1 in the functional layer 3 are uniformly distributed, with some of the particles of component 1 diffused within the positive electrode material layer and distributed among the particles of the positive electrode active material 4. After processes such as liquid injection, chemical conversion, and capacity grading were performed on the lithium battery manufactured as described above, electrochemical tests and safety tests were conducted, respectively. Table 1 shows the specific test results for the electrochemical properties of lithium batteries manufactured using this positive electrode plate, and Table 2 shows the safety test results. Example 3

[0040] Except for changing component 2 to AlPO4, the positive electrode active material to NCM83, the negative electrode to SiOC450, and the battery structure to NCM83||SiOC450, all other parameters were the same as in Example 1. After processes such as liquid injection, chemical conversion, and capacity grading were carried out on the lithium batteries manufactured as described above, electrochemical tests and safety tests were performed, respectively. The specific test results for the electrochemical properties of the manufactured lithium batteries are shown in Table 1, and the safety test results are shown in Table 2. Example 4

[0041] Component 2 is Li 1.4 Al 0.4 Ti 1.6 (PO4)3 and AlPO4 are changed, and the Li in component 1 and component 2 is changed. 1.4 Al 0.4 Ti 1.6 Except for setting the mass ratio of (PO4)3 and AlPO4 to 1:8:1, changing the positive electrode active material to LCO, changing the negative electrode to SiOC450, and setting the battery structure to LCO||SiOC450, all other parameters were the same as in Example 1. After performing processes such as liquid injection, chemical conversion, and capacity grading on the lithium batteries manufactured as described above, electrochemical tests and safety tests were performed, respectively. The specific test results for the electrochemical properties of the manufactured lithium batteries are shown in Table 1, and the safety test results are shown in Table 2. Example 5

[0042] Except for changing the 25 kg mixed component, which consists of component 1 and component 2, to one containing only component 1 LiTaOSiO4 25 kg and excluding component 2, changing the positive electrode active material to LFP, changing the negative electrode to graphite, and changing the battery structure to LFP||graphite, all other parameters were kept the same as in Example 1. After processes such as liquid injection, chemical conversion, and capacity grading were carried out on the lithium battery manufactured as described above, electrochemical tests and safety tests were performed, respectively. The specific test results for the electrochemical properties of the manufactured lithium battery are shown in Table 1, and the safety test results are shown in Table 2. Example 6

[0043] Change component 1 to LiTaOGeO4 and component 2 to Li 1.4 Al0.4 Ge 1.6 Except for changing the material to (PO4)3, changing the positive electrode active material to NCM83, changing the negative electrode to graphite, and changing the battery structure to NCM83||graphite, all other parameters were the same as in Example 1. After processes such as liquid injection, chemical conversion, and capacity grading were carried out on the lithium batteries manufactured as described above, electrochemical tests and safety tests were performed, respectively. The specific test results for the electrochemical properties of the manufactured lithium batteries are shown in Table 1, and the safety test results are shown in Table 2. Example 7

[0044] Component 2 is Li 1.4 Al 0.4 Ti 1.6 (PO4)3 and AlPO4 are changed, and the Li in component 1 and component 2 is changed. 1.4 Al 0.4 Ti 1.6 Except for changing the mass ratio of (PO4)3 and AlPO4 to 1:8:1 and the porosity to 80%, all other parameters were the same as in Example 1. After the lithium batteries manufactured as described above underwent processes such as liquid injection, chemical conversion, and capacity grading, electrochemical tests and safety tests were performed, respectively. The specific test results for the electrochemical properties of the manufactured lithium batteries are shown in Table 1, and the safety test results are shown in Table 2. Example 8

[0045] Component 2 is Li 1.4 Al 0.4 Ti 1.6 (PO4)3 and AlPO4 are changed, and the Li in component 1 and component 2 is changed. 1.4 Al 0.4 Ti 1.6 Except for changing the mass ratio of (PO4)3 and AlPO4 to 1:8:1 and the porosity to 20%, all other parameters were the same as in Example 1. After the lithium batteries manufactured as described above underwent processes such as liquid injection, chemical conversion, and capacity grading, electrochemical tests and safety tests were performed, respectively. The specific test results for the electrochemical properties of the manufactured lithium batteries are shown in Table 1, and the safety test results are shown in Table 2. Example 9

[0046] Component 2 is Li1.4 Al 0.4 Ti 1.6 (PO4)3 and AlPO4 are changed, and the Li in component 1 and component 2 is changed. 1.4 Al 0.4 Ti 1.6 The mass ratio of (PO4)3 and AlPO4 was set to 1:8:1, and the coating thickness was changed to 500 nm. Each primary particle of the mixed component contained crystalline particles of component 1 and component 2, and the particle size D50 of the primary particles of the mixed component was 300 nm. The morphology of the mixed component of component 1 and component 2 is shown in Figure 4, where 1 is the mixed component of component 1 and component 2 in one particle, 2 is the coating, 3 is the active material, and 4 is the current collector. Other parameters were the same as in Example 1. After processes such as liquid injection, chemical conversion, and capacity grading were performed on the lithium batteries manufactured as described above, electrochemical tests and safety tests were performed, respectively. The specific test results of the electrochemical properties of the manufactured lithium batteries are shown in Table 1, and the safety test results are shown in Table 2. Example 10

[0047] Component 2 is Li 1.4 Al 0.4 Ti 1.6 (PO4)3 and AlPO4 are changed, and the Li in component 1 and component 2 is changed. 1.4 Al 0.4 Ti 1.6 Except for changing the mass ratio of (PO4)3 and AlPO4 to 1:8:1 and the coating thickness to 10 μm, all other parameters were the same as in Example 1. After the lithium batteries manufactured as described above underwent processes such as liquid injection, chemical conversion, and capacity grading, electrochemical tests and safety tests were performed, respectively. The specific test results for the electrochemical properties of the manufactured lithium batteries are shown in Table 1, and the safety test results are shown in Table 2. Example 11

[0048] Component 2 is Li 1.4 Al 0.4 Ti 1.6 (PO4)3 and AlPO4 are changed, and the Li in component 1 and component 2 is changed. 1.4 Al 0.4 Ti 1.6Except for setting the mass ratio of (PO4)3 and AlPO4 to 1:8:1, changing the porosity to 20%, and setting the D50 of the mixed component composed of component 1 and component 2 to 50 nm, the remaining parameters were the same as in Example 9. After performing processes such as liquid injection, chemical conversion, and capacity grading on the lithium batteries manufactured as described above, electrochemical tests and safety tests were performed, respectively. The specific test results for the electrochemical properties of the manufactured lithium batteries are shown in Table 1, and the safety test results are shown in Table 2. Example 12

[0049] Component 2 is Li 1.4 Al 0.4 Ti 1.6 (PO4)3 and AlPO4 are changed, and the Li in component 1 and component 2 is changed. 1.4 Al 0.4 Ti 1.6 Except for changing the mass ratio of (PO4)3 and AlPO4 to 1:8:1 and changing the D50 of the mixed component composed of component 1 and component 2 to 1 μm, the remaining parameters were the same as in Example 9. After the lithium batteries manufactured as described above underwent processes such as liquid injection, chemical conversion, and capacity grading, electrochemical tests and safety tests were performed, respectively. The specific test results for the electrochemical properties of the manufactured lithium batteries are shown in Table 1, and the safety test results are shown in Table 2. Example 13

[0050] Component 2 is Li 1.4 Al 0.4 Ti 1.6 (PO4)3 and AlPO4 are changed, and the Li in component 1 and component 2 is changed. 1.4 Al 0.4 Ti 1.6 The mass ratio of (PO4)3 and AlPO4 was set to 1:8:1, the D50 of the mixed component composed of component 1 and component 2 was changed to 50 nm, and the coating thickness was changed to 10 nm. The remaining parameters were the same as in Example 9. After the lithium batteries manufactured as described above underwent processes such as liquid injection, chemical conversion, and capacity grading, electrochemical tests and safety tests were performed, respectively. The specific test results for the electrochemical properties of the manufactured lithium batteries are shown in Table 1, and the safety test results are shown in Table 2. Comparative Example 1

[0051] Except for the absence of components 1 and 2, all other parameters were the same as in Example 1. After the lithium batteries manufactured as described above underwent processes such as liquid injection, chemical conversion, and capacity grading, electrochemical tests and safety tests were performed, respectively. The specific test results for the electrochemical properties of the manufactured lithium batteries are shown in Table 1, and the safety test results are shown in Table 2. Comparative Example 2

[0052] Except for omitting components 1 and 2, changing the positive electrode active material to NCM83, and using NCM83||SiOC650 for the battery structure, all other parameters were the same as in Example 1. After processes such as liquid injection, chemical conversion, and capacity grading were performed on the lithium batteries manufactured as described above, electrochemical tests and safety tests were conducted, respectively. The specific test results for the electrochemical properties of the manufactured lithium batteries are shown in Table 1, and the safety test results are shown in Table 2. Comparative Example 3

[0053] Except for omitting components 1 and 2, changing the positive electrode active material to NCM83, the negative electrode to SiOC450, and the battery structure to NCM83||SiOC450, all other parameters were the same as in Example 1. After processes such as liquid injection, chemical conversion, and capacity grading were carried out on the lithium batteries manufactured as described above, electrochemical tests and safety tests were performed, respectively. The specific test results for the electrochemical properties of the manufactured lithium batteries are shown in Table 1, and the safety test results are shown in Table 2. Comparative Example 4

[0054] Except for omitting components 1 and 2, changing the positive electrode active material to LCO, the negative electrode to SiOC450, and the battery structure to LCO||SiOC450, all other parameters were the same as in Example 1. After processes such as liquid injection, chemical conversion, and capacity grading were carried out on the lithium batteries manufactured as described above, electrochemical tests and safety tests were performed, respectively. The specific test results for the electrochemical properties of the manufactured lithium batteries are shown in Table 1, and the safety test results are shown in Table 2. Comparative Example 5

[0055] Except for omitting components 1 and 2, changing the positive electrode active material to LFP, using graphite for the negative electrode, and using an LFP||graphite battery structure, all other parameters were the same as in Example 1. After processes such as liquid injection, chemical conversion, and capacity grading were carried out on the lithium batteries manufactured as described above, electrochemical tests and safety tests were performed, respectively. The specific test results for the electrochemical properties of the manufactured lithium batteries are shown in Table 1, and the safety test results are shown in Table 2. Comparative Example 6

[0056] Except for omitting components 1 and 2, changing the positive electrode active material to NCM83, using graphite for the negative electrode, and using an NCM83||graphite battery structure, all other parameters were the same as in Example 1. After processes such as electrolyte injection, chemical conversion, and capacity grading were performed on the lithium batteries manufactured as described above, electrochemical tests and safety tests were conducted, respectively. The specific test results for the electrochemical properties of the manufactured lithium batteries are shown in Table 1, and the safety test results are shown in Table 2. Comparative Example 7

[0057] Except for replacing 25 kg of the mixed component consisting of component 1 and component 2 with 25 kg of Al2O3, all other parameters were the same as in Example 1. After the lithium batteries manufactured as described above underwent processes such as liquid injection, chemical conversion, and capacity grading, electrochemical tests and safety tests were performed, respectively. The specific test results for the electrochemical properties of the manufactured lithium batteries are shown in Table 1, and the safety test results are shown in Table 2. Comparative Example 8

[0058] Except for replacing 25 kg of the mixed component, which consists of component 1 and component 2, with 25 kg of ZnO, changing the positive electrode active material to NCM83, and changing the battery structure to NCM83||SiOC650, all other parameters were the same as in Example 1. After processes such as liquid injection, chemical conversion, and capacity grading were carried out on the lithium batteries manufactured as described above, electrochemical tests and safety tests were performed, respectively. The specific test results for the electrochemical properties of the manufactured lithium batteries are shown in Table 1, and the safety test results are shown in Table 2. Comparative Example 9

[0059] After changing 25 kg of the mixed component composed of Component 1 and Component 2 to 25 kg of Li 1.4 Al 0.4 Ti 1.6 (PO4)3, changing the cathode active material to NCM83, changing the anode to SiOC450, and changing the battery structure to NCM83||SiOC450, other parameters were the same as in Example 1. For the lithium battery manufactured as described above, after processes such as liquid injection, formation, and capacity grading, electrochemical tests and safety tests were respectively conducted. The specific test results of the electrochemical characteristics of the manufactured lithium battery are shown in Table 1, and the safety test results are shown in Table 2. Comparative Example 10

[0060] After changing 25 kg of the mixed component composed of Component 1 and Component 2 to 25 kg of AlPO4, changing the cathode active material to LCO, changing the anode to SiOC450, and changing the battery structure to LCO||SiOC450, other parameters were the same as in Example 1. For the lithium battery manufactured as described above, after processes such as liquid injection, formation, and capacity grading, electrochemical tests and safety tests were respectively conducted. The specific test results of the electrochemical characteristics of the manufactured lithium battery are shown in Table 1, and the safety test results are shown in Table 2. Comparative Example 11

[0061] After changing 25 kg of the mixed component composed of Component 1 and Component 2 to Li 0.5 La 0.5 TiO3, changing the cathode active material to LFP, changing the anode to graphite, and changing the battery structure to LFP||graphite, other parameters were the same as in Example 1. For the lithium battery manufactured as described above, after processes such as liquid injection, formation, and capacity grading, electrochemical tests and safety tests were respectively conducted. The specific test results of the electrochemical characteristics of the manufactured lithium battery are shown in Table 1, and the safety test results are shown in Table 2. Comparative Example 12

[0062] After changing 25 kg of the mixed component composed of Component 1 and Component 2 to Li7La3Zr2O 12Except for changing the weight to 25 kg, changing the positive electrode active material to NCM83, changing the negative electrode to graphite, and changing the battery structure to NCM83||graphite, all other parameters were the same as in Example 1. After processes such as electrolyte injection, chemical conversion, and capacity grading were carried out on the lithium batteries manufactured as described above, electrochemical tests and safety tests were performed, respectively. The specific test results for the electrochemical properties of the manufactured lithium batteries are shown in Table 1, and the safety test results are shown in Table 2. Table 1 shows the electrochemical properties data for the examples.

[0063] [Table 1] Table 2 shows the safety data for the examples.

[0064] [Table 2]

[0065] From the data in Tables 1 and 2, it can be seen that coating the positive electrode surface with a functional layer containing component 1 or a mixture of component 1 and component 2 can significantly improve the battery's rate characteristics, cycle characteristics, and safety. Comparing Example 5 with Comparative Example 11, it was found that since constructing a high-efficiency CEI is key to improving the electrical characteristics and safety of liquid and solid batteries, coating the positive electrode with component 1 is far more effective in improving battery rate characteristics, cycle characteristics, and safety than coating with a solid electrolyte with high lithium ion conductivity. From a comparison of Example 1 with Examples 7 and 8, it was found that there is an optimal design for the porosity of the functional layer on the positive electrode plate of the lithium battery of the present invention. If the porosity is too small, it is detrimental to the battery's rate characteristics, and if the porosity is too large, it is detrimental to the battery's cycle characteristics. From a comparison of Example 1 with Examples 9, 10, and 13, it was found that there is an optimal thickness for the functional layer. If the thickness is too small, it is detrimental to safety, and if the thickness is too large, it is detrimental to the rate characteristics. A comparison of Example 1 with Examples 11 and 12 shows that there is an optimal particle size for Component 1 and Component 2. Optimizing the particle size can improve the electrical characteristics and safety of the battery. If the particle size is too small, the additive particles tend to aggregate, affecting the rate characteristics. If the particle size is too large, the additive particles cannot adequately contact the surface of the active material particles, particularly affecting the rate characteristics and safety. Both excessively small and excessively large particle sizes are detrimental to the construction of a stable CEI.

[0066] The embodiments described above are merely exemplary embodiments used to illustrate the principles of the present invention, but it should be understood that the present invention is not limited thereto. Those skilled in the art can make various modifications and improvements without departing from the spirit and essence of the present invention, and such modifications and improvements are considered to be within the scope of the protection of the present invention.

Claims

1. A positive electrode plate for a liquid lithium battery, comprising a positive electrode material layer and a functional layer located directly above the positive electrode material layer, The material of the functional layer comprises component 1, and component 1 is LiTiOPO ４ LiTaOSIO ４ LiTaOGeO ４ A positive electrode plate for a liquid lithium battery, characterized by being at least one of the following.

2. The material of the functional layer further contains Component 2, and Component 2 is LiM2 ２ (PO ４ ) ３ , Li １＋ｘ２ Al ｘ２ M2 ２－ｘ２ (PO ４ ) ３ , M2O ２ , Li １６－４ｙ２ M2 ｙ２ O ８ , M2P ２ O ７ , M3PO ４ , M3 ２ SiO ５ , M4 ３ (PO ４ ) ２ , M4 ２ SiO ４ and is at least one or a combination of a plurality of species selected therefrom, where M2 is one species selected from Ti, Ge, Zr, and Hf, where 0 < x2 < 0.6, and M3 and M4 are each independently any one species selected from Al, Ga, Sc, Y, Ca, Sr, Zn, Si, In, Lu, La, Fe, Cr, Ge, and 3 < y2 < 4. The positive electrode plate according to claim 1, characterized in that.

3. The aforementioned component 2 is InPO ４ , LATP, AlPO ４ , LAGP, LATP+AlPO ４ LAGP+Al ２ SiO ５ InPO ４ +LATP, Al ２ SiO ５ , TiO ２ +LiTi ２ (PO ４ ) ３ , TiP ２ O ７ +LiGe ２ (PO ４ ) ３ A positive electrode plate according to claim 2, characterized in that it is one of the types of positive electrodes.

4. The positive electrode plate according to claim 2, characterized in that, in the material of the functional layer, the form of the mixed component composed of component 1 and component 2 is a uniform mixture of particles of component 1 and particles of component 2, or each primary particle contains a crystalline form of component 1 and a crystalline form of component 2.

5. The positive electrode plate according to claim 1, characterized in that the functional layer has a three-dimensional porous structure with a porosity of p (20% ≤ p ≤ 80%) and a thickness of h (0 μm < h ≤ 10 μm).

6. The positive electrode plate according to claim 1, characterized in that the particle size of component 1 in the functional layer is 10 nm to 10 μm.

7. The positive electrode plate according to claim 6, characterized in that the particle size of component 1 in the functional layer is 50 nm to 1 μm.

8. The positive electrode plate according to claim 2, characterized in that the particle size of component 2 in the functional layer is 10 nm to 10 μm.

9. The positive electrode plate according to claim 8, characterized in that the particle size of component 2 in the functional layer is 50 nm to 1 μm.

10. The positive electrode plate according to claim 1, characterized in that the positive electrode active material in the positive electrode material layer includes at least one of the following: lithium cobalt oxide positive electrode and its modified material, NCM ternary positive electrode and its modified material, NCA ternary positive electrode and its modified material, lithium nickel manganate positive electrode and its modified material, lithium-rich positive electrode and its modified material, and lithium iron phosphate positive electrode and its modified material.

11. Step 1 for manufacturing the positive electrode active layer, Step 2 involves uniformly mixing component 1 or a mixture of component 1 and component 2 with a solvent and grinding it to form a slurry of 10 nm to 10 μm, Step 3 involves adding a binder to the slurry obtained in Step 2 and mixing it uniformly to produce a coating slurry. A method for manufacturing a positive electrode plate for a liquid lithium battery according to any one of claims 1 to 10, comprising step 4, which involves coating the slurry obtained in step 3 onto a positive electrode active layer and drying it to obtain a positive electrode plate.

12. The manufacturing method according to claim 11, characterized in that the solvent includes at least one of deionized water, ethanol, NMP, alcohol, isopropanol, and acetone.

13. A lithium battery cell comprising a positive electrode plate, a negative electrode plate, a separator, an electrolyte, and a case, wherein the positive electrode plate is the positive electrode plate described in any one of claims 1 to 10.

14. The lithium battery cell according to claim 13, characterized in that the lithium battery is a liquid battery.

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