Phosphate-modified positive electrode material and preparation method and application thereof

Abstract

The application provides a phosphate-modified positive electrode material and a preparation method and application thereof. The preparation method comprises the following steps: 1) dissolving a metal salt and a phosphorus source in deionized water, reacting, and forming a mixed solution; 2) dispersing a coated substrate material in the mixed solution formed in the step 1) to obtain a turbid solution; 3) stirring and reacting a reverse solvent with the turbid solution formed in the step 2), and then centrifuging, washing and drying to obtain a substrate powder coated with a metal phosphorus-containing species; and 4) calcining the substrate powder formed in the step 3) to obtain the phosphate-modified positive electrode material. The positive electrode material particle with the metal phosphate modification obtained by the application can be used to realize a stable high-specific-energy energy storage lithium ion battery.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of chemistry and energy materials, and particularly relates to a phosphate-modified positive electrode material and a preparation method and application thereof. BACKGROUND

[0002] Surface coating has important application value in the fields of materials and chemistry. Uniform modifier species can be controllably constructed on the surface of different base materials, which can endow the materials with new properties and uses. In the field of lithium ion batteries, it is well known that the positive electrode material of lithium ion batteries is prone to side reactions with flammable organic electrolyte during charging and discharging, which leads to serious damage to the interface structure of the material and an increase in the interface impedance of the battery, thereby sharply reducing the capacity and cycle life of the battery. As a modification strategy, surface coating can effectively block the direct contact between the positive electrode active material and the organic electrolyte, thereby protecting the positive electrode material from the corrosion of the electrolyte and improving the structural stability and cycle stability of the positive electrode material.

[0003] Metal phosphate is a coating species that attracts much attention, and has excellent structural stability and obvious advantages in stabilizing the interface structure of the positive electrode material of the battery. At present, the coating methods based on phosphate are very limited, mainly including solid-phase ball milling mixing, liquid-phase solvent evaporation, atomic layer deposition and the like. The recent invention patent CN111916702B, etc. obtains a lithium ion battery positive electrode material coated with phosphate by using a solid-phase mixing combined with calcination method, and the invention patent CN110190254A, etc. forms a lithium phosphate-coated ternary positive electrode material by directly mixing a phosphate source with the electrode material and evaporating the solvent, which all show improved battery cycle performance. However, the high-energy-consumption methods such as solid-phase ball milling mixing and liquid-phase solvent evaporation cannot guarantee the uniformity and controllability of the coating species, so that an accurate relationship cannot be established between the final coating structure and performance. Although atomic layer deposition and the like can realize uniform coating of the surface phosphate species, they cannot be applied on a large scale due to the reasons such as expensive equipment and complicated operation process. Therefore, it is urgent to develop a new method with low cost, low energy consumption and easy industrial scaling to realize uniform coating of the surface phosphate. SUMMARY

[0004] The purpose of the present application is to provide a phosphate-modified positive electrode material and a preparation method and application thereof.

[0005] To solve the above problems, the present application provides the following technical solutions:

[0006] The preparation method of the phosphate-modified positive electrode material comprises:

[0007] 1) dissolving a metal salt and a phosphorus source in deionized water, reacting to form a mixed solution;

[0008] 2) dispersing the coated substrate material in the mixed solution formed in step 1) to obtain a turbid solution;

[0009] 3) stirring the anti-solvent with the turbid solution formed in step 2) to obtain a substrate powder coated with metal-containing phosphorus species after centrifugation, washing and drying;

[0010] 4) calcining the substrate powder formed in step 3) to obtain a phosphate-modified positive electrode material.

[0011] According to an embodiment of the present application, the metal salt is selected from one or more of chloride, sulfate, nitrate, acetate and alcoholate of the metal element, preferably the sulfate of the metal element. Preferably, the metal element is selected from at least one of aluminum, nickel, manganese, cobalt, iron, copper, zinc, titanium, zirconium, niobium, tantalum, magnesium, preferably aluminum, nickel, manganese, cobalt.

[0012] According to an embodiment of the present application, the concentration of the metal salt in the mixed solution of step 1) is 0.001-1 mol / L.

[0013] According to an embodiment of the present application, the phosphorus source is selected from one or more of ammonium dihydrogen phosphate, diammonium hydrogen phosphate, ammonium phosphate, sodium dihydrogen phosphate, sodium hydrogen phosphate, sodium phosphate, potassium dihydrogen phosphate, potassium hydrogen phosphate, potassium phosphate, preferably ammonium dihydrogen phosphate.

[0014] According to an embodiment of the present application, the concentration of the phosphorus source in the mixed solution of step 1) is 0.001-1 mol / L.

[0015] According to an embodiment of the present application, the reaction conditions for forming the mixed solution in the mixed solution of step 1) include that the reaction temperature is room temperature to 60°C, preferably room temperature; and the reaction time is 1 h-72 h, preferably 12 h.

[0016] According to an embodiment of the present application, the molar ratio of the metal salt to the phosphorus source in the mixed solution of step 1) is 0.001-1:0.001-1.

[0017] According to an embodiment of the present application, the coated substrate material is selected from at least one of metal material, non-metal material, oxide, sulfide, carbide, nitride, phosphide, lithium salt positive electrode material, sodium salt positive electrode material, potassium salt positive electrode material, organic particle.

[0018] According to an embodiment of the present application, the metal in the coated substrate material is selected from at least one of gold, silver, ruthenium, rhodium, palladium, platinum, germanium, tin, antimony and alloys thereof.

[0019] According to an embodiment of the present application, the non-metal in the coated substrate material is selected from at least one of carbon, silicon, sulfur, phosphorus, selenium.

[0020] According to embodiments of the present application, the oxide in the coated substrate material is selected from at least one of silicon dioxide, titanium dioxide, aluminum trioxide, zinc oxide, magnesium oxide, calcium oxide, manganese dioxide, trimanganese tetraoxide, iron trioxide, iron trioxide, cobalt trioxide, nickel oxide, vanadium pentoxide, zirconium oxide, molybdenum oxide, indium tin oxide, tin oxide, lithium lanthanum zirconium oxide.

[0021] According to embodiments of the present application, the sulfide in the coated substrate material is selected from at least one of zinc sulfide, tungsten sulfide, bismuth sulfide, titanium disulfide, iron sulfide, cobalt sulfide, nickel sulfide, molybdenum sulfide, tin sulfide, antimony sulfide.

[0022] According to embodiments of the present application, the carbide in the coated substrate material is selected from at least one of silicon carbide, titanium carbide, calcium carbide, vanadium carbide, chromium carbide, tantalum carbide, tungsten carbide, boron carbide.

[0023] According to embodiments of the present application, the nitride in the coated substrate material is selected from at least one of boron nitride, gallium nitride, silicon nitride, titanium nitride, vanadium nitride, niobium nitride, tungsten nitride, phosphorus nitride.

[0024] According to embodiments of the present application, the phosphide in the coated substrate material is selected from at least one of iron phosphide, cobalt phosphide, nickel phosphide, titanium phosphide, molybdenum phosphide, tin phosphide.

[0025] According to embodiments of the present application, the lithium salt cathode material in the coated substrate material includes, but is not limited to, at least one of lithium titanate, lithium cobaltate, lithium nickelate, lithium manganate, lithium nickel manganate, lithium nickel cobalt manganate, lithium nickel cobalt aluminum, lithium-rich lithium nickel cobalt manganate, lithium titanium phosphate, lithium titanium aluminum phosphate, lithium vanadium phosphate, lithium iron phosphate, lithium manganese phosphate, lithium cobalt phosphate, lithium iron manganese phosphate, lithium manganese cobalt phosphate.

[0026] According to embodiments of the present application, the sodium salt cathode material in the coated substrate material includes, but is not limited to, at least one of oxide-based sodium salt cathode material, polyanion-based sodium salt cathode material, Prussian blue-based sodium salt cathode material, fluoride-based sodium salt cathode material, organic compound-based sodium salt cathode material.

[0027] According to embodiments of the present application, the potassium salt cathode material in the coated substrate material includes, but is not limited to, at least one of Prussian blue-based potassium salt cathode material, layered oxide-based potassium salt cathode material, polyanion-based potassium salt cathode material, organic material-based potassium salt cathode material.

[0028] According to embodiments of the present application, the organic particles in the coated substrate material are selected from at least one of phenol formaldehyde resin, urea formaldehyde resin, melamine resin, polystyrene, polydopamine, polyvinylpyrrolidone.

[0029] According to an embodiment of the present application, in step 2), the turbid solution is further dispersed by ultrasonic and / or stirring.

[0030] According to an embodiment of the present application, the concentration of the coated substrate in the turbid solution of step 2) is 0.001-1000 g / L.

[0031] According to an embodiment of the present application, the anti-solvent includes, but is not limited to, at least one of methanol, ethanol, propanol, butanol, pentanol, hexanol, acetone, butanone, furfural, acetonitrile, dioxane, and preferably ethanol.

[0032] According to an embodiment of the present application, in step 3), the volume ratio of the turbid solution to the anti-solvent is 1-30:30-100, for example, 15:45.

[0033] According to an embodiment of the present application, the method for mixing the turbid solution with the anti-solvent includes directly pouring, slowly dripping, or dripping by controlling the dripping speed through a peristaltic pump, the turbid solution into the anti-solvent; or, directly pouring, slowly dripping, or dripping by controlling the dripping speed through a peristaltic pump, the anti-solvent into the turbid solution.

[0034] According to an embodiment of the present application, the stirring temperature of the turbid solution and the anti-solvent is room temperature to 80°C, and preferably room temperature.

[0035] According to an embodiment of the present application, the stirring speed of the turbid solution and the anti-solvent is between 100 r / min and 1000 r / min, and preferably 600 r / min.

[0036] According to an embodiment of the present application, the stirring reaction time is 5-240 min.

[0037] According to an embodiment of the present application, the atmosphere for calcination is at least one of oxygen, air, nitrogen, and argon.

[0038] According to an embodiment of the present application, the calcination conditions include a calcination temperature of 300-900°C and a calcination time of 1-10 h.

[0039] The present application also provides a phosphate-modified positive electrode material, which is prepared by the above preparation method.

[0040] According to an embodiment of the present application, the phosphate-modified positive electrode material is a particle with a core-shell structure.

[0041] According to an embodiment of the present application, the phosphate-modified positive electrode material comprises a nanocoating shell and a coated substrate material, wherein the nanocoating shell is modified on the surface of the coated substrate material; the coated substrate material has the meaning as described above; the nanocoating shell comprises phosphate. Preferably, the nanocoating shell partially or completely coats the surface of the coated substrate material, preferably completely coats the surface of the coated substrate material. Further, the nanocoating shell is uniformly and continuously distributed on the surface of the coated substrate material.

[0042] According to an embodiment of the present application, the nanocoating shell comprises a phosphate of a metal element, such as at least one of, but not limited to, aluminum phosphate, nickel phosphate, manganese phosphate, cobalt phosphate, iron phosphate, copper phosphate, zinc phosphate, titanium phosphate, zirconium phosphate, niobium phosphate, tantalum phosphate, magnesium phosphate, preferably aluminum phosphate, nickel phosphate, manganese phosphate, cobalt phosphate.

[0043] According to an embodiment of the present application, the thickness of the nanocoating shell is 0 nm to 500 nm, such as 1 nm, 1.5 nm, 5 nm, 10 nm, 50 nm, 100 nm, 200 nm, 300 nm, 400 nm.

[0044] The present application also provides the use of the above-mentioned phosphate-modified positive electrode material in an energy storage battery.

[0045] The present application has the advantages of, for example, constructing a high specific energy energy storage battery.

[0046] Advantages:

[0047] The method of the present application can be used as a modification strategy for constructing a nanoscale phosphate coating layer on the interface of a positive electrode material of a lithium ion battery or a lithium battery.

[0048] The obtained metal phosphate-coated particles with core-shell structure can be used as a substrate for controllable and uniform coating of a positive electrode material of a lithium ion battery or a lithium battery.

[0049] The obtained positive electrode material particles modified by metal phosphate can be used to realize a stable high specific energy energy storage lithium ion battery.

[0050] The application provides a surface phosphate-modified positive electrode material and a preparation method and application thereof. The metal salt and ammonium dihydrogen phosphate are fully dissolved and reacted in an aqueous solution, a counter solvent is gradually introduced into the mixed system, the reaction product metal phosphorus-containing substance is slowly deposited on the surface of the existing substrate seed, and a continuous and uniform coating layer is gradually formed on the surface. By controlling the concentration of the metal salt and the phosphorus source, the amount of the counter solvent, the substrate concentration, the feeding mixing mode and the like, the reaction rate of the growth of the substance can be controlled, so that the uniform and controllable deposition of the coating substance is ensured, and the thickness of the interface coating layer can also be conveniently controlled. The method adopts a mild liquid phase method to introduce a metal phosphate nanolayer on the surface of different substrates, has low cost and strong controllability, and the formed coated material has very wide application prospect.

[0051] The application provides a new method which is convenient, efficient and green, and is used for constructing a metal phosphate coating layer on the surface of a substrate. The method adopts a mild liquid phase strategy to control the controllable deposition of a metal phosphorus-containing substance on the surface of a substrate, fully reacts a metal salt and a phosphorus source in water to form a clear solution, utilizes the interaction between the reaction product and a new solvent, realizes the uniform and continuous coating of the metal phosphorus-containing substance on the surface of the substrate by controlling the feeding mixing mode, the feeding speed, the reactant concentration, the pH value and the like, and constructs a uniform metal phosphate on the surface of the substrate after heat treatment. The method is suitable for different substrate materials, especially suitable for various positive electrode materials of lithium ion batteries, can design and form a uniform phosphate nanolayer on the surface of the positive electrode material, is used for inhibiting the interface side reaction of the battery, and significantly improves the electrochemical cycle stability of the battery. The method provides a control strategy suitable for mass processing of modified positive electrode materials of lithium ion batteries, and has very wide application value.

[0052] The application utilizes the interaction between a metal salt, a phosphorus source, water and a counter solvent, constructs a coating layer of a metal phosphorus-containing substance on the interface of a positive electrode material of a lithium ion battery, and converts the coating layer into a metal phosphate interface modification layer by calcination. The strategy can effectively block the direct contact between the positive electrode active material and the electrolyte, greatly reduces the interface impedance of the battery in the cycle process, and thus improves the structural stability of the positive electrode material in the electrochemical cycle, especially at a high cut-off voltage. The thickness of the coating layer on the surface of the positive electrode material can be conveniently controlled by changing the amount of the positive electrode substrate or the concentration of the metal salt and the phosphorus source, so that the cycle stability and the rate performance of the positive electrode material can be significantly improved without losing the capacity of the battery. BRIEF DESCRIPTION OF DRAWINGS

[0053] Figure 1 A transmission electron microscope photo of the aluminum phosphate coated ternary single-crystal lithium nickel cobalt manganese oxide particles in Example 1.

[0054] Figure 2Transmission electron microscope photograph of aluminum phosphate-coated single-crystal lithium cobaltate particles of Example 2.

[0055] Figure 3 Low-magnification transmission electron microscope photograph of aluminum phosphate-coated high-pressure lithium nickel manganese oxide particles of Example 3.

[0056] Figure 4 Transmission electron microscope photograph of 20 nm aluminum phosphate-coated high-pressure lithium nickel manganese oxide particles of Example 3 at a magnification.

[0057] Figure 5 X-ray energy dispersive spectroscopy (EDS) image of 20 nm aluminum phosphate-coated high-pressure lithium nickel manganese oxide particles of Example 3.

[0058] Figure 6 Transmission electron microscope photograph of 4 nm aluminum phosphate-coated high-pressure lithium nickel manganese oxide particles of Example 4.

[0059] Figure 7 Transmission electron microscope photograph of 9 nm aluminum phosphate-coated high-pressure lithium nickel manganese oxide particles of Example 5.

[0060] Figure 8 Cycling performance of the positive electrode materials corresponding to Example 5 and Comparative Examples 1-2 at a charge-discharge current of 140 mA / g. DETAILED DESCRIPTION

[0061] The technical solutions of the present application will be further described in detail below in combination with specific examples. It should be understood that the following examples are only illustrative and explanatory of the present application, and should not be interpreted as limiting the scope of protection of the present application. Any technology realized based on the above description of the present application is encompassed within the scope intended to be protected by the present application.

[0062] Unless otherwise specified, the raw materials and reagents used in the following examples are commercially available or can be prepared by known methods.

[0063] The present application will be further described below using aluminum phosphate as an example, and other metal phosphate coating methods are similar. According to the specific reaction system, the corresponding metal salt, anti-solvent, and coated substrate are selected, and the interaction between the precursor mixed solution and the anti-solvent is controlled by using appropriate feeding methods to achieve the deposition of different metal phosphates on the surface of the substrate. The thickness and size of the surface coating layer can be conveniently adjusted by changing the concentration of the metal salt and the phosphorus source, the amount of the coated substrate, the feeding method, and other methods. Finally, the surface layer containing the phosphorus metal salt is modified to the interface of the positive electrode material by calcination. However, the present application is not limited to the following examples. The methods are conventional methods unless otherwise specified. The raw materials can be obtained from public commercial channels unless otherwise specified.

[0064] Example 1

[0065] Preparation of aluminum phosphate modified ternary single-crystal lithium nickel cobalt manganese oxide particles with core-shell structure

[0066] 1) 0.067 g of aluminum sulfate octadecahydrate and 0.012 g of ammonium dihydrogen phosphate were sequentially dissolved in 15 ml of deionized water, continuously stirred to dissolve and reacted for 12 h to form a mixed solution;

[0067] 2) 0.98 g of ternary single-crystal lithium nickel cobalt manganese oxide powder was dispersed in the mixed solution formed in step 1), ultrasonically dispersed and stirred to obtain a turbid solution;

[0068] 3) 45 ml of anhydrous ethanol was slowly added to the turbid solution formed in step 2) and continuously stirred to react, and after centrifugation, washing and drying, a substrate powder uniformly coated with metal aluminum phosphorus species was obtained;

[0069] 4) The substrate powder formed in step 3) was calcined at 700°C for 2 h to obtain an aluminum phosphate modified lithium nickel cobalt manganese oxide material.

[0070] The aluminum phosphate modified ternary single-crystal lithium nickel cobalt manganese oxide particles were of a typical core-shell structure, and a transmission electron micrograph thereof is shown in Figure 1 The average size of the substrate lithium nickel cobalt manganese oxide single-crystal particles was about 3 μm, the surface shell thickness was 28 nm, and the aluminum phosphate was continuously and uniformly distributed on the surface of the ternary positive electrode substrate.

[0071] Example 2

[0072] Preparation of aluminum phosphate modified single-crystal lithium cobalt oxide particles with core-shell structure

[0073] 1) 0.134 g of aluminum sulfate octadecahydrate and 0.024 g of ammonium dihydrogen phosphate were sequentially dissolved in 15 ml of deionized water, continuously stirred to dissolve and reacted for 12 h to form a mixed solution;

[0074] 2) 0.98 g of single-crystal lithium cobalt oxide powder was dispersed in the mixed solution formed in step 1), ultrasonically dispersed and stirred to obtain a turbid solution;

[0075] 3) 45 ml of anhydrous ethanol was slowly added to the turbid solution formed in step 2) and continuously stirred to react, and after centrifugation, washing and drying, a substrate powder uniformly coated with metal aluminum phosphorus species was obtained;

[0076] 4) The substrate powder formed in step 3) was calcined at 700°C for 2 h to obtain an aluminum phosphate modified lithium cobalt oxide material.

[0077] The aluminum phosphate modified ternary single-crystal lithium cobalt oxide particles were of a typical core-shell structure, and a transmission electron micrograph thereof is shown in Figure 2The TEM image of the spinel nickel-manganese oxide particles with aluminum phosphate modification is shown in FIG. 3. The average size of the substrate spinel nickel-manganese oxide particles is about 1-10 μm, and the TEM image at a higher magnification is shown in FIG. 4. The surface shell thickness is about 20 nm, and the EDS image (FIG. 5) shows that phosphorus and aluminum are continuously and uniformly distributed on the surface of the substrate spinel nickel-manganese oxide particles.

[0078] Example 3

[0079] Preparation of high-voltage nickel-manganese oxide particles with core-shell structure and aluminum phosphate modification

[0080] 1) 0.067 g of aluminum sulfate octadecahydrate and 0.012 g of ammonium dihydrogen phosphate were sequentially dissolved in 15 ml of deionized water, and the solution was continuously stirred and reacted for 12 h to form a mixed solution;

[0081] 2) 1.83 g of spinel nickel-manganese oxide powder was dispersed in the mixed solution formed in step 1), and ultrasonic dispersion and stirring were performed to obtain a turbid solution;

[0082] 3) 45 ml of anhydrous ethanol was slowly added to the turbid solution formed in step 2), and the reaction was continuously stirred. After centrifugation, washing, and drying, a substrate powder uniformly coated with metal aluminum and phosphorus-containing species was obtained;

[0083] 4) The substrate powder formed in step 3) was calcined at 700°C for 2 h to obtain a nickel-manganese oxide material with aluminum phosphate modification.

[0084] The spinel nickel-manganese oxide particles with aluminum phosphate modification had a typical core-shell structure, and the TEM image thereof is shown in FIG. 3. The average size of the substrate spinel nickel-manganese oxide particles was about 1-10 μm, and the TEM image at a higher magnification is shown in FIG. 4. The surface shell thickness was about 20 nm, and the EDS image (FIG. 5) showed that phosphorus and aluminum were continuously and uniformly distributed on the surface of the substrate spinel nickel-manganese oxide particles. Figure 3 Figure 4 Figure 5

[0085] Example 4

[0086] Preparation of high-voltage nickel-manganese oxide particles with a 4 nm aluminum phosphate coating

[0087] 1) 0.134 g of aluminum sulfate octadecahydrate and 0.024 g of ammonium dihydrogen phosphate were sequentially dissolved in 15 ml of deionized water, and the solution was continuously stirred and reacted for 12 h to form a mixed solution;

[0088] 2) 7.30 g of spinel nickel-manganese oxide powder was dispersed in the mixed solution formed in step 1), and ultrasonic dispersion and stirring were performed to obtain a turbid solution;

[0089] 3) 45 ml of anhydrous ethanol was slowly added to the turbid solution formed in step 2), and the reaction was continuously stirred. After centrifugation, washing, and drying, a substrate powder uniformly coated with metal aluminum and phosphorus-containing species was obtained;

[0090] ​​​4) The substrate powder formed in step 3) is calcined at a high temperature of 700°C for 2h to obtain the aluminum phosphate modified lithium nickel manganese oxide material.

[0091] The aluminum phosphate modified spinel lithium nickel manganese oxide particles have a typical core-shell structure, and a transmission electron micrograph thereof is shown in Figure 6 The average size of the substrate lithium nickel manganese oxide particles is about 1-10 μm, the surface shell thickness is 4 nm, and the aluminum phosphate is continuously and uniformly distributed on the surface of the lithium nickel manganese oxide anode substrate.

[0092] Example 5

[0093] I. Preparation of high-pressure lithium nickel manganese oxide particles with a 9 nm aluminum phosphate coating

[0094] 1) 0.134 g of aluminum sulfate octadecahydrate and 0.024 g of ammonium dihydrogen phosphate are sequentially dissolved in 15 ml of deionized water, continuously stirred to dissolve and fully reacted for 12 h to form a mixed solution;

[0095] 2) 3.65 g of spinel lithium nickel manganese oxide powder is dispersed in the mixed solution formed in step 1), ultrasonically dispersed and stirred to obtain a turbid solution;

[0096] 3) 45 ml of anhydrous ethanol is slowly added to the turbid solution formed in step 2) and continuously stirred to react, and after centrifugation, washing and drying, a substrate powder with a uniform coating of metal aluminum containing phosphorus species is obtained;

[0097] 4) The substrate powder formed in step 3) is calcined at a high temperature of 700°C for 2h to obtain the aluminum phosphate modified lithium nickel manganese oxide material.

[0098] The aluminum phosphate modified spinel lithium nickel manganese oxide particles have a typical core-shell structure, and a transmission electron micrograph thereof is shown in Figure 7 The average size of the substrate lithium nickel manganese oxide particles is about 1-10 μm, the surface shell thickness is 9 nm, and the aluminum phosphate is continuously and uniformly distributed on the surface of the lithium nickel manganese oxide anode substrate. By conveniently changing the content of the coated substrate, the controllable coating of aluminum phosphate with different thicknesses on the surface of the lithium nickel manganese oxide substrate can be directly realized, and the regulation and matching between the synthesis conditions and the coating thickness are established.

[0099] II. Preparation of aluminum phosphate modified lithium nickel manganese oxide electrode

[0100] The modified lithium nickel manganese oxide anode powder 0.24 g in the above example 5, conductive additive acetylene black 0.03 g, binder PVDF with a mass concentration of 5% 0.6 g and a small amount of solvent NMP are mixed, and after slurry preparation, sheet coating (aluminum sheet as current collector), drying, an aluminum phosphate modified lithium nickel manganese oxide electrode sheet is obtained.

[0101] III. Assembly of battery

[0102] The aluminum phosphate modified lithium nickel manganese oxide electrode prepared above was used as a positive electrode, lithium metal was used as a negative electrode, a polypropylene microporous membrane (Celgard 2400) was used as a separator, and 1 mol / L LiPF6 was used as an electrolyte. A button cell was assembled in a glove box under the protection of argon.

[0103] Four, battery test

[0104] The above battery was subjected to constant current charge and discharge test using a charge and discharge instrument, the test voltage interval was 3-5 V, and the test temperature was 25°C. The specific capacity and charge and discharge current of the battery were calculated based on the mass of lithium nickel manganese oxide.

[0105] Comparative Example 1

[0106] One, preparation of uncoated lithium nickel manganese oxide electrode

[0107] Three, assembling a battery, the specific steps are the same as those in step three of Example 5.

[0108] Four, battery test, the specific steps are the same as those in step four of Example 5.

[0109] Comparative Example 2

[0110] One, preparation of partially aluminum phosphate coated lithium nickel manganese oxide positive electrode material

[0111] 1) 0.134 g of aluminum sulfate octadecahydrate and 0.024 g of ammonium dihydrogen phosphate were sequentially dissolved in 15 ml of deionized water, continuously stirred to dissolve and fully reacted for 12 h to form a mixed solution;

[0112] 2) 3.65 g of spinel lithium nickel manganese oxide powder was dispersed in the mixed solution formed in step 1), ultrasonic dispersion and stirring to obtain a turbid solution, and the turbid solution was centrifuged, washed and dried to obtain a partially aluminum phosphate coated base powder;

[0113] 3) The base powder formed in step 2) was calcined at 700°C for 2 h to obtain a partially aluminum phosphate coated lithium nickel manganese oxide positive electrode material.

[0114] Two, preparation of partially coated lithium nickel manganese oxide electrode, the specific steps are the same as those in step two of Example 5.

[0115] Three, assembling a battery, the specific steps are the same as those in step three of Example 5.

[0116] Four, battery test, the specific steps are the same as those in step four of Example 5.

[0117] Figure 8The cycle performance of the positive electrode material corresponding to Example 5 and Comparative Example 1, Comparative Example 2 at a charge-discharge current of 1C (140 mA / g). After nearly 400 cycles, the discharge capacity of the sample in Example 5 was 121 mAh / g, which exhibited a capacity retention rate of up to 98%, which was significantly higher than 60 mAh / g (capacity retention rate 52%) of the uncoated sample and 103 mAh / g (capacity retention rate 84%) of the partially coated sample, significantly improving the cycle stability and life of the battery, and reflecting that the uniform and controllable interface modification structure has outstanding significance for stabilizing the battery interface and achieving long cycle performance.

[0118] The above describes the exemplary embodiments of the present application. However, the protection scope of the present application is not limited to the above-described embodiments. Any modification, equivalent replacement, improvement, etc. made by those skilled in the art within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing a phosphate-modified positive electrode material, the method comprising: 1) dissolving a metal salt and a phosphorus source in deionized water, reacting to form a mixed solution; 2) dispersing a coated substrate material in the mixed solution formed in step 1) to obtain a turbid solution; the coated substrate material is selected from at least one of lithium salt positive electrode materials, sodium salt positive electrode materials, and potassium salt positive electrode materials; 3) stirring the turbid solution formed in step 2) with an anti-solvent, and then centrifuging, washing, and drying to obtain a substrate powder coated with a metal phosphate; 4) calcining the substrate powder formed in step 3) to obtain a phosphate-modified positive electrode material.

2. The production method according to claim 1, characterized by, The metal salt is selected from one or more of chloride salts, sulfate salts, nitrate salts, acetate salts, and alcoholates of metal elements; the metal elements are selected from at least one of aluminum, nickel, manganese, cobalt, iron, copper, zinc, titanium, zirconium, niobium, tantalum, and magnesium; In the mixed solution of step 1), the concentration of the metal salt is 0.001-1 mol / L; The phosphorus source is selected from one or more of ammonium dihydrogen phosphate, diammonium hydrogen phosphate, ammonium phosphate, sodium dihydrogen phosphate, disodium hydrogen phosphate, sodium phosphate, potassium dihydrogen phosphate, dipotassium hydrogen phosphate, and potassium phosphate; In the mixed solution of step 1), the concentration of the phosphorus source is 0.001-1 mol / L; In the mixed solution of step 1), the reaction conditions for forming the mixed solution include a reaction temperature of room temperature to 60 ℃ and a reaction time of 1 h-72 h; In the mixed solution of step 1), the molar ratio of the metal salt to the phosphorus source is 0.001-1:0.001-1.

3. The preparation method according to claim 1, characterized in that, The lithium salt positive electrode material includes at least one of lithium titanate, lithium cobaltate, lithium nickelate, lithium manganate, lithium nickel manganate, lithium nickel cobalt manganate, lithium nickel cobalt aluminum, lithium-rich lithium nickel cobalt manganate, lithium titanium phosphate, lithium titanium aluminum phosphate, lithium vanadium phosphate, lithium iron phosphate, lithium manganese phosphate, lithium cobalt phosphate, lithium iron manganese phosphate, and lithium manganese cobalt phosphate; The sodium salt positive electrode material is selected from at least one of oxide-based sodium salt positive electrode materials, polyanion-based sodium salt positive electrode materials, Prussian blue-based sodium salt positive electrode materials, fluoride-based sodium salt positive electrode materials, and organic compound-based sodium salt positive electrode materials; The potassium salt positive electrode material in the coated substrate material is selected from at least one of Prussian blue-based potassium salt positive electrode materials, layered oxide-based potassium salt positive electrode materials, polyanion-based potassium salt positive electrode materials, and organic material-based potassium salt positive electrode materials.

4. The method of claim 1, wherein, In the turbid solution of step 2), the concentration of the coated substrate is 0.001-1000 g / L; The anti-solvent includes at least one of methanol, ethanol, propanol, butanol, pentanol, hexanol, acetone, butanone, furfural, acetonitrile, and dioxane; In step 3), the volume ratio of the turbid solution to the anti-solvent is 1-30:30-100.

5. The preparation method according to claim 1, characterized in that, The method for mixing the turbid solution and the anti-solvent includes directly pouring, slowly dripping, or dropping at a controlled rate by a peristaltic pump into the anti-solvent; or, directly pouring, slowly dripping, or dropping at a controlled rate by a peristaltic pump into the turbid solution; The stirring temperature of the turbid solution and the anti-solvent is room temperature to 80 ℃. The stirring speed of the turbid solution and the anti-solvent is between 100 r / min and 1000 r / min. The stirring reaction time is 5-240 min.

6. The method of claim 1, wherein, The atmosphere of the calcination is at least one of oxygen, air, nitrogen, and argon. The conditions of the calcination include: the calcination temperature is 300-900 ℃, and the calcination time is 1-10 h. 7.A phosphate modified positive electrode material, which is prepared by the preparation method of any one of claims 1-6.

8. The positive electrode material according to claim 7, characterized in that, The phosphate modified positive electrode material is a particle with a core-shell structure. The phosphate modified positive electrode material comprises a nano-coating shell layer and a coated substrate material, wherein the nano-coating shell layer is modified on the surface of the coated substrate material; and the nano-coating shell layer comprises a phosphate.

9. The cathode material of claim 8, wherein, The nano-coating shell layer partially or completely coats the surface of the coated substrate material.

10. The positive electrode material of claim 8, wherein, The nano-coating shell layer is continuously and uniformly distributed on the surface of the coated substrate material.

11. The cathode material of claim 8, wherein, The nano-coating shell layer comprises a phosphate of the metal element. The thickness of the nano-coating shell layer is 0 nm-500 nm. 12.The application of the positive electrode material of any one of claims 7-11 in an energy storage battery.

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