Lithium battery positive electrode material and preparation method thereof

Abstract

The invention discloses a lithium battery positive electrode material and a preparation method thereof, and belongs to the technical field of lithium batteries. The technical scheme is as follows: (1) the lithium battery positive electrode material comprises a lithium active material and a composite conductive layer, and the composite conductive layer coats the outer surface of the lithium active material; the composite conductive layer is formed by compounding a conductive polymer adhesive and conductive carbon according to a mass ratio of 1: (0.4-2); (2) sequentially carrying out dialysis treatment and freeze drying on the composite gel prepared in the step (1), and then calcining in inert gas to obtain a calcined product; and (3) carrying out hydrothermal reaction on the calcined product obtained in the step (2), a lithium source, a ferrophosphorus source and a graphene suspension under a water-containing condition to obtain the composite lithium battery positive electrode material. According to the preparation method, dialysis treatment and freeze drying are performed on the composite gel, so that the volatilization temperature of a solvent is reduced, meanwhile, the volume change of the gel in the solvent volatilization process is reduced, and the stability of a three-dimensional space network structure is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of lithium ions, and in particular relates to a positive electrode material for a lithium battery. Background Art

[0002] The cathode material of lithium batteries is generally lithium oxide. The main cathode materials on the market are lithium cobalt oxide, lithium manganese oxide with spinel structure and lithium iron phosphate with olivine structure. The main advantages of lithium cobalt oxide are high conductivity, simple production process and easy preparation, but its high preparation cost and large environmental pollution restrict its development. Lithium manganese oxide has a spinel structure. Its main advantages are low price, high safety and easy preparation. Its disadvantages are low theoretical capacity and poor high temperature performance. Lithium iron phosphate material is one of the popular cathode materials studied in recent years. It has the advantages of high stability, safety, environmental protection and low price. Its disadvantages are low energy density and room temperature conductivity, and poor stability of metal oxide cathode materials. After long-term charging and discharging, the capacity of the battery will be significantly reduced, which is increasingly unable to meet people's demand for high-capacity and high-energy-density electronic products.

[0003] At present, people are combining carbon materials with excellent cycle performance with positive electrode active materials to improve the cycle stability of the positive electrode materials. However, most of the carbon composite materials reported so far are still a simple mixture of carbon materials and active materials. After multiple charges and discharges, the active materials may fall off the carbon materials, resulting in a decrease in the performance of the lithium battery. Summary of the invention

[0004] The present invention provides a lithium battery positive electrode material and a preparation method thereof to solve the above problems.

[0005] The technical solution of the present invention is: A method for preparing a positive electrode material for a lithium battery comprises the following steps: (1) The lithium battery positive electrode material comprises a lithium active material and a composite conductive layer, wherein the composite conductive layer is coated on the outer surface of the lithium active material; the composite conductive layer is composed of a conductive polymer glue and a conductive carbon in a mass ratio of 1:(0.4-2); (2) subjecting the composite gel prepared in step (1) to dialysis treatment, freeze drying, and then calcining in an inert gas to obtain a calcined product; (3) The calcined product obtained in step (2) is subjected to a hydrothermal reaction with a lithium source, a phosphorus iron source, and a graphene suspension under aqueous conditions to obtain a composite lithium battery positive electrode material.

[0006] Preferably, the metal cation is obtained by dissolving a metal salt in a solvent, and the acid radical ion in the metal salt may be SO4 2- 、NO3- , Cl - Br - ,I - 、F - 、ClO3 - 、MnO4 - 、MnO4 2 -, PO4 3- , HS - , S 2- 、HSO4 - 、HPO4 2- 、H2PO4 - 、MoO4 2- At least one of the above.

[0007] Preferably, the ligand is an inorganic ligand and may be NH3, CO, CN - 、F - , Cl - 、SCN - 、NO3 - and OH - or at least one of an organic ligand oxalate ion, 2-methylimidazole, pyridine, 2,2-bipyridine, ethylenediamine, acetonitrile and 1,10-phenanthroline.

[0008] Preferably, S1: weighing a certain mass of nickel salt material, manganese salt material and lithium salt material according to the metering ratio of nickel ions, manganese ions and lithium ions in the final nickel manganese oxide lithium product; S2: dissolving a nickel salt material, a manganese salt material and a lithium salt material into deionized water to prepare a nickel salt solution, a manganese salt solution and a lithium salt solution respectively, mixing the nickel salt solution and the manganese salt solution to obtain a nickel-manganese mixed solution, and the lithium salt solution is reserved; S3: adding a precipitant to the nickel-manganese mixed solution of step 2, slowly adding the precipitant, controlling the pH value to be between 11 and 12, gradually forming a nickel-manganese precipitate during the stirring process, and obtaining a solution containing a nickel-manganese precipitate; S4: washing and filtering the solution containing nickel and manganese precipitates prepared in step 3, collecting the precipitates, placing the precipitates in a drying oven, and drying them at 80-260° C. for 2-10 hours; S5: uniformly mixing the dried nickel manganese precipitate with the lithium salt solution prepared in step 2 to obtain a lithium nickel manganese oxide mixed solution; Preferably, the organic gelator can be at least one of cyclodextrin derivatives, cholesteryl anthraquinone-2-carboxylic acid, benzyl urea derivatives, 2-octyldodecyl 4-[(1-naphthylamine)carboxylamine] benzoate, polyvinyl pyrrolidone, 1,4-di[(3,4-dioctyloxybenzene)-bis(amide)]benzene, N-(3,4-alkoxybenzoyl)-N'-(4'-nitrobenzoyl)hydrazine, N-(3,5-alkoxybenzoyl)-N'-(4'-cyanobenzoyl)hydrazine and phenazine derivative organic gelators.

[0009] Preferably, the organic solvent is at least one of C1-C7 alcohols, C5-C12 alkanes, C6-C9 aromatic hydrocarbons, C3-C7 ketones, and amides. More specifically, it can be at least one of n-butanol, ethanol, N-methylpyrrolidone, hexamethylphosphinate, dimethylacetamide, xylene, nitrobenzene, N,N-dimethylformamide, N,N-dimethylacetamide, cyclohexanone and dimethyl sulfoxide.

[0010] Preferably, the organic solvent is at least one of C1-C7 alcohols, C5-C12 alkanes, C6-C9 aromatic hydrocarbons, C3-C7 ketones, and amides. More specifically, it can be at least one of n-butanol, ethanol, N-methylpyrrolidone, hexamethylphosphinate, dimethylacetamide, xylene, nitrobenzene, N,N-dimethylformamide, N,N-dimethylacetamide, cyclohexanone and dimethyl sulfoxide.

[0011] Compared with the prior art, the present invention has the following beneficial effects: The three-dimensional carbon skeleton can effectively improve the volume expansion of the electrode material during the charging and discharging process. The holes can also provide channels for the migration of electrons and ions. Its large specific surface area can provide attachment points for lithium iron phosphate, thereby increasing the loading capacity of lithium iron phosphate, reducing the loss of active substances due to the shuttle effect, and improving the coulombic efficiency and cycle stability of the battery. DETAILED DESCRIPTION

[0012] Example 1 The positive electrode material of the lithium battery includes a lithium active material and a composite conductive layer, and the composite conductive layer is coated on the outer surface of the lithium active material. The composite conductive layer is composed of polypyrrole and its derivatives: copper oxide = 1: 0.4; the lithium active material is a nickel salt material, a manganese salt material and a lithium salt material.

[0013] The technical solution of the present invention is: a method for preparing a positive electrode material for a lithium battery, comprising the following steps: (1) Fe 2+and oxalate ions to form a metal complex, and the metal complex and the cyclodextrin derivative are uniformly mixed in n-butanol, and aged to obtain a composite gel; (2) subjecting the composite gel prepared in step (1) to dialysis treatment and freeze drying in sequence, and then calcining at 400° C. in an inert gas to obtain a calcined product; (3) The calcined product obtained in step (2) is subjected to a hydrothermal reaction with lithium hydroxide, a phosphorus iron source, and a graphene suspension under aqueous conditions, wherein the molar ratio of the lithium source to the phosphorus iron source is 1:1.5, to obtain a composite lithium battery positive electrode material.

[0014] Example 2 The positive electrode material of the lithium battery includes a lithium active material and a composite conductive layer, and the composite conductive layer is coated on the outer surface of the lithium active material. The composite conductive layer is composed of polypyrrole and its derivatives: copper oxide = 1: 0.4; the lithium active material is a nickel salt material, a manganese salt material and a lithium salt material.

[0015] The technical solution of the present invention is: a method for preparing a positive electrode material for a lithium battery, comprising the following steps: (1) Co 2+ and 2-methylimidazole to form a metal complex, and the metal complex and 2-octyldodecyl 4-[(1-naphthylamine)carboxylamine]benzoate are uniformly mixed in hexamethylphosphinyltriamide, and aged to obtain a composite gel; (2) subjecting the composite gel prepared in step (1) to dialysis treatment, freeze drying, and then calcining in an inert gas to obtain a calcined product; (3) The calcined product obtained in step (2) is subjected to a hydrothermal reaction with lithium acetate, a phosphorus iron source, and a graphene suspension under aqueous conditions, wherein the molar ratio of the lithium source to the phosphorus iron source is 1:0.8, to obtain a composite lithium battery positive electrode material.

[0016] Example 3 The technical solution of the present invention is: a method for preparing a positive electrode material for a lithium battery, comprising the following steps: The positive electrode material of the lithium battery includes a lithium active material and a composite conductive layer, and the composite conductive layer is coated on the outer surface of the lithium active material. The composite conductive layer is composed of a conductive polymer glue and a conductive carbon in a mass ratio of 1: (0.4-2); the conductive polymer glue is selected from one or more of polypyrrole and its derivatives, polythiophene and its derivatives, polyphenylene ether and its derivatives, polyaniline and its derivatives; the conductive carbon is selected from one or more of copper oxide, carbon black, carbon fiber, carbon nanotubes and graphene; the lithium active material is a nickel-cobalt-manganese ternary material.

[0017] The method for preparing the positive electrode material of a lithium battery is characterized by comprising the following steps: S1: Weigh a certain mass of nickel salt material, manganese salt material and lithium salt material according to the metering ratio of nickel ions, manganese ions and lithium ions in the final nickel manganese oxide lithium product; S2: dissolving a nickel salt material, a manganese salt material and a lithium salt material into deionized water to prepare a nickel salt solution, a manganese salt solution and a lithium salt solution respectively, mixing the nickel salt solution and the manganese salt solution to obtain a nickel-manganese mixed solution, and the lithium salt solution is reserved; S3: adding a precipitant to the nickel-manganese mixed solution of step 2, slowly adding the precipitant, controlling the pH value at 11, gradually forming a nickel-manganese precipitate during stirring, and obtaining a solution containing a nickel-manganese precipitate; S4: washing and filtering the solution containing nickel and manganese precipitates prepared in step 3, collecting the precipitates, placing the precipitates in a drying oven, and drying them at 100° C. for 4 hours; S5: uniformly mixing the dried nickel manganese precipitate with the lithium salt solution prepared in step 2 to obtain a lithium nickel manganese oxide mixed solution; S6: heating and concentrating the lithium nickel manganese oxide mixed solution in step 5 to a thick state, placing it in a drying oven, and drying it at 100° C. for 7 hours; Although the present invention has been described in detail by combining the preferred embodiments, the present invention is not limited thereto. Without departing from the spirit and essence of the present invention, a person skilled in the art may make various equivalent modifications or substitutions to the embodiments of the present invention, and these modifications or substitutions shall be within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. A method for preparing a positive electrode material for a lithium battery, characterized in that: The following steps are involved: (1) The lithium battery positive electrode material comprises a lithium active material and a composite conductive layer, wherein the composite conductive layer is coated on the outer surface of the lithium active material; the composite conductive layer is composed of a conductive polymer glue and a conductive carbon in a mass ratio of 1:(0.4-2); (2) subjecting the composite gel prepared in step (1) to dialysis treatment, freeze drying, and then calcining in an inert gas to obtain a calcined product; (3) The calcined product obtained in step (2) is subjected to a hydrothermal reaction with a lithium source, a phosphorus iron source, and a graphene suspension under aqueous conditions to obtain a composite lithium battery positive electrode material.

2. The method for preparing a positive electrode material for a lithium battery according to claim 1, wherein: The metal cation is obtained by dissolving a metal salt in a solvent, and the acid radical ion in the metal salt can be SO4 2- 、NO3 - , Cl - Br - ,I - 、F - 、ClO3 - 、MnO4 - 、MnO4 2 -, PO4 3- , HS - , S 2- 、HSO4 - 、HPO4 2- 、 H2PO4 - 、MoO4 2- At least one of the above.

3. The method for preparing a positive electrode material for a lithium battery according to claim 1, characterized in that: The ligand is an inorganic ligand and can be NH3, CO, CN - 、F - , Cl - 、SCN - 、NO3 - and OH - or at least one of an organic ligand oxalate ion, 2-methylimidazole, pyridine, 2,2-bipyridine, ethylenediamine, acetonitrile and 1,10-phenanthroline.

4. The method for preparing a positive electrode material for a lithium battery according to claim 1, wherein: S1: Weigh a certain mass of nickel salt material, manganese salt material and lithium salt material according to the metering ratio of nickel ions, manganese ions and lithium ions in the final nickel manganese oxide lithium product; S2: dissolving a nickel salt material, a manganese salt material and a lithium salt material into deionized water to prepare a nickel salt solution, a manganese salt solution and a lithium salt solution respectively, mixing the nickel salt solution and the manganese salt solution to obtain a nickel-manganese mixed solution, and the lithium salt solution is reserved; S3: adding a precipitant to the nickel-manganese mixed solution of step 2, slowly adding the precipitant, controlling the pH value to be between 11 and 12, gradually forming a nickel-manganese precipitate during the stirring process, and obtaining a solution containing a nickel-manganese precipitate; S4: washing and filtering the solution containing nickel and manganese precipitates prepared in step 3, collecting the precipitates, placing the precipitates in a drying oven, and drying them at 80-260° C. for 2-10 hours; S5: uniformly mixing the dried nickel manganese precipitate with the lithium salt solution prepared in step 2 to obtain a lithium nickel manganese oxide mixed solution; The method for preparing a positive electrode material for a lithium battery as claimed in claim 1, characterized in that: the organic gel factor can be at least one of a cyclodextrin derivative, a cholesteryl anthraquinone-2-carboxylic acid, a benzyl urea derivative, 2-octyldodecyl 4-[(1-naphthylamine)carboxylamine]benzoate, polyvinyl pyrrolidone, 1,4-di[(3,4-dioctyloxybenzene)-biamide]benzene, N-(3,4-alkoxybenzoyl)-N'-(4'-nitrobenzoyl)hydrazine, N-(3,5-alkoxybenzoyl)-N'-(4'-cyanobenzoyl)hydrazine and a phenazine derivative organic gel factor.

5. The method for preparing a positive electrode material for a lithium battery according to claim 1, characterized in that: The organic solvent is at least one of C1-C7 alcohols, C5-C12 alkanes, C6-C9 aromatic hydrocarbons, C3-C7 ketones, and amides. More specifically, it can be at least one of n-butanol, ethanol, N-methylpyrrolidone, hexamethylphosphinate, dimethylacetamide, xylene, nitrobenzene, N,N-dimethylformamide, N,N-dimethylacetamide, cyclohexanone, and dimethyl sulfoxide.

6. The method for preparing a positive electrode material for a lithium battery according to claim 1, characterized in that: The organic solvent is at least one of C1-C7 alcohols, C5-C12 alkanes, C6-C9 aromatic hydrocarbons, C3-C7 ketones, and amides. More specifically, it can be at least one of n-butanol, ethanol, N-methylpyrrolidone, hexamethylphosphinate, dimethylacetamide, xylene, nitrobenzene, N,N-dimethylformamide, N,N-dimethylacetamide, cyclohexanone, and dimethyl sulfoxide.