Preparation method and application of nickel-rich cobalt-free single crystal positive electrode material of lithium ion battery

Abstract

The invention discloses a preparation method of a nickel-rich cobalt-free single crystal positive electrode material of a lithium ion battery, and belongs to the field of positive electrode materials of lithium ion batteries. The preparation method comprises the steps of preparing a nickel-rich cobalt-free hydroxide precursor through coprecipitation; uniformly mixing the precursor, molten salt and lithium salt according to a certain stoichiometric ratio, then calcining at high temperature, washing the obtained mixture with deionized water for multiple times, and drying to obtain lithium-deficient single-crystal-morphology spinel-like nickel-rich primary particles; and then supplementing a certain amount of lithium salt into the primary particles, uniformly mixing, and sintering at high temperature to obtain the single-crystal nickel-rich cobalt-free layered positive electrode material. The method is suitable for preparing the single crystal nickel-rich positive electrode material, lithium is added in the first step, the molar ratio Li/(Ni + Mg + Fe + Ti) of the lithium element to the sum of nickel, magnesium, iron and titanium is 0.8-1.0, micron-sized lithium-deficient spinel type nickel-rich single crystal particles are formed after sintering, the micron-sized large-size nickel-rich layered single crystal positive electrode material can be formed in the low-temperature range of 650-800 DEG C after water washing and lithium supplementation, the tap density is high, the lithium-nickel mixed arrangement is low, and the layered structure is good, so that the specific capacity is higher, and the cycle performance is good.

Description

technical field [0001] The invention belongs to the technical field of lithium ion batteries, and in particular relates to a nickel-rich cobalt-free single crystal positive electrode material and a preparation method thereof. Background technique [0002] In order to meet the needs of fast electric vehicles and grid storage markets, the demand for lithium-ion batteries is also growing exponentially, and lithium-ion batteries propose higher energy density, longer cycle life and lower price requirements. Compared with negative electrode materials with excellent comprehensive performance, positive electrode materials have lower specific energy, and the cost is nearly 40% of the cost of lithium-ion batteries. It is of great significance to develop cathode materials with high energy density, long cycle life and low price. [0003] The ternary materials NCM and NCA with high energy density are currently the mainstream cathode materials in the market. Cobalt resources are scarce,...

AI Technical Summary

Problems solved by technology

[0005] However, the difficulty in the synthesis of large-scale dispersed Ni-rich layered single crystals lies in the contradiction between the high temperature required for micron-sized Ni-rich layered single crystals and the low temperature required for Ni-rich materials to form a good layered structure with low lithium-nickel mixing.

If the sintering temperature is low, single crystal nickel-rich layered materials cannot be formed; if the sintering temperature is high, large-sized nickel-rich layered single crystals can be formed, but lithium-nickel mixing is high, there are many oxygen vacancy defects, and the grains are agglomerated and agglomerated seriously. poor chemical properties

[0006] In the current method for preparing nickel-rich single crystals, the sintering temperature required by the high-temperature solid-phase method is too high, and the layered structure of the sintered single crystal material is poor, the agglomeration is serious, and the electrochemical performance is not good; the two-step sintering method, Due to the lack of lithium source in the first step of sintering, a higher temperature is required to form a single crystal, resulting in a large number of defects, and the layered structure is extremely poor. After the second step of lithium replenishment sintering, there are still a large number of defects, and the agglomeration is serious; the molten salt method can Reducing the single crystal sintering temperature can easily form large-sized monodisperse single crystals, but limited by the melting point and solubility of molten salt, the single crystal sintering temperature of the molten salt method is still high, and water washing is required, which deteriorates the surface structure of nickel-rich layered materials , poor electrochemical performance

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