Lithium-rich manganese positive electrode material coated with spinel phase lithium manganate and preparation method thereof

Abstract

The invention discloses a lithium-rich manganese positive electrode material coated with spinel phase lithium manganate and a preparation method thereof. The method comprises the following steps of: uniformly mixing the lithium-rich manganese positive electrode material, a positive electrode conductive agent and a positive electrode binder in N-methyl pyrrolidone, coating an aluminum foil with themixture and drying the aluminum foil to prepare a positive electrode sheet; uniformly mixing a negative electrode material, a negative electrode conductive agent and a negative electrode binder in deionized water, coating a copper foil with the mixture and drying the copper foil so as to prepare a negative electrode sheet; assembling the positive and negative electrode sheets, and adding an electrolyte to prepare a lithium ion battery; connecting the lithium ion battery to a charging instrument for charging the lithium ion battery, and stopping charging when the charging capacity reaches a threshold value, wherein the threshold value is equal to the lithium-rich manganese gram * lithium-rich manganese theoretical gram volume * preset coefficient A; disassembling the lithium ion battery, taking out the lithium-rich manganese with lithium deintercalated on the upper surface of the positive electrode sheet, and performing a high-temperature annealing process to obtain the lithium-rich manganese positive electrode material coated with the spinel phase lithium manganate and having graded structure. The method of the invention ensures the consistency and the repeatability of materials,can inhibit the cracking and pulverization of the materials during charging and discharging, and improves the first efficiency and the cycle stability.

Description

technical field [0001] The invention relates to a lithium ion battery, in particular to a positive electrode material for a lithium ion battery and a preparation method thereof, in particular to a lithium-rich manganese positive electrode material coated with spinel phase lithium manganese oxide. Background technique [0002] The specific capacity of cathode materials is the most important factor affecting the energy density and application of lithium-ion batteries. Lithium-rich manganese cathode materials have a gram capacity of more than 250mAh / g, and the battery energy density can reach 350Wh / kg, which has broad application potential. However, during the first charging process of lithium-rich manganese cathode materials, part of the Li ions are replaced by Li 2 The deactivation of the form of O leads to the low charge and discharge efficiency of the material for the first time, and at the same time, the Li 2 The release of O will change the surface composition and struct...

AI Technical Summary

Problems solved by technology

The Chinese invention patent with the publication number CN107215900A discloses a method for constructing a spinel structure on the surface of a lithium-rich manganese-based positive electrode material. By adding the lithium-rich manganese-based positive electrode material to a weak acid aqueous solution, Li + with H + Ion exchange, and then heat-treat the ion-exchanged cathode material to transform the lithium-deficient surface structure into a spinel structure, and obtain a lithium-rich manganese-based cathode material with a spinel structure on the surface. This method is simple and low in cost, but difficult Control the number of ion exchange in each batch, the repeatability is poor

The Chinese invention patent application with the publication number CN108511710A discloses a lithium-rich manganese-based lithium-ion battery positive electrode material and its preparation method. Ammonium fluoride and lithium carbonate are added to the lithium-rich manganese, and the mixed powder is obtained by grinding and mixing evenly. Under airtight conditions, low-temperature firing heat treatment is carried out to obtain a lithium-rich manganese material with spinel phase lithium manganate on the surface and coated with lithium fluoride layer. The first cycle efficiency, rate performance and cycle stability of the material are all improved. , but the raw materials are all solid powders, it is difficult to fully mix evenly, and the product consistency is poor

The Chinese invention patent application with the publication number CN108615875A discloses a lithium-rich manganese-based positive electrode material and its preparation method. First, a solution containing phosphate is prepared, added to the suspension of lithium-rich manganese-based positive electrode material, and reacted and dried to obtain The intermediate product is calcined at a high temperature in a tube furnace to obtain a lithium-rich manganese-based positive electrode material coated with phosphate on the surface and a spinel structure on the surface. The lithium-rich manganese-based positive electrode material prepared by this method improves the first Coulombic efficiency, rate performance, Cycle stability and high temperature performance, but this method needs to prepare two different solutions first and then dry and sinter at high temperature, which consumes a lot of energy and makes mass production difficult

The Chinese invention patent application with the publication number CN109585833A discloses a lithium-rich manganese-based modified material and its preparation method and positive electrode material, by preparing a gel on the surface of the lithium-rich manganese-based material, drying and calcining to obtain a spinel structure The lithium-rich manganese-based modified material of the coating layer improves the rate performance of lithium-ion batteries and reduces the voltage drop, but the gel method has high requirements for raw materials and high energy consumption, so it is rarely used in industry