Preparation method of li-ion battery cathode material coated with li-deficient material

Abstract

The invention discloses a method for preparing a lithium ion battery cathode material wrapped and modified by a Li-lacked material. The method includes the following steps that NiaCobMnc(OH)2, a lithium source and a compound of an M element are mixed evenly according to the proportion and then sintered under the condition of 700 DEG C or above, and a cathode active substance matrix is prepared; a cobalt-containing compound and the lithium source are evenly mixed according to the proportion and then sintered under the condition of 700 DEG C or above, and the Li-lacked active material is prepared; the prepared Li-lacked active material and the cathode active substance matrix are evenly mixed and sintered under the condition of 600 DEG C or above, and the lithium ion battery cathode material wrapped and modified by the Li-lacked material is obtained. The preparation method is simple, and the prepared product is low in lithium-nickel mixed typeset degree, stable in layered structure and excellent in electrical property.

Description

technical field [0001] The invention relates to a lithium ion battery cathode material and a preparation method thereof, in particular to an active material coated and modified lithium ion battery cathode material and a preparation method thereof. Background technique [0002] Lithium nickel cobalt manganese (NCM) ternary material integrated LiCoO 2 , LiNiO 2 and LiMnO 2 The advantages of the three materials, due to the obvious synergistic effect among Ni, Co, and Mn, the performance of the ternary material is better than that of the single-component layered cathode material, and it is considered to be one of the most promising new cathode materials. [0003] Thanks to Li + with you 2+ The radii are similar, and Li-Ni mixing is very easy to occur during the sintering process of ternary materials. The influence of Li-Ni mixing: (1) when Ni 2+ Occupied Li + After the position is set, it will hinder the transmission of lithium ions, so that a part of lithium cannot be in...

AI Technical Summary

Problems solved by technology

The influence of Li-Ni mixing: (1) when Ni 2+ Occupied Li + After the position, it will hinder the transmission of lithium ions, so that a part of lithium cannot be inserted into the crystal lattice smoothly.

During the first charge and discharge process, Li in the lithium layer and the transition metal layer + All can be extracted, but when the first discharge, due to the mixed arrangement of cations, part of the lithium cannot return to the positive electrode lattice, so the first coulombic efficiency of the material is reduced.

(2) The degree of polarization of the battery during charging and discharging is closely related to the conductivity of the material and the diffusion coefficient of lithium ions, and the diffusion coefficient of lithium ions is affected by the transmission space of lithium ions. When lithium ions enter the transition metal layer, due to the The radius of the ion is larger than the radius of the transition metal ion, the transition metal layer will expand accordingly, the interlayer distance will expand and the adjacent lithium ion layer will be squeezed, resulting in a decrease in the diffusion space of lithium ions, and a decrease in the diffusion coefficient of lithium ions, so the mixed arrangement of lithium ions will Causes the polarization of the battery to increase

(3) Lithium occupies the nickel site, which will also lead to an increase in the average bond length of the metal-oxygen bond and an unstable layered structure. Therefore, during the cycle, the dissolution of metal ions is serious, especially the dissolution of manganese, which leads to the serious dissolution of ternary materials. Faster decay during cycling

Synthesis process optimization is mainly by increasing O 2 atmosphere to reduce Li / Ni mixing, but the cost is high and it is not suitable for industrial production

Doping is mainly by mixing the precursor, doping compound and lithium salt, and then improving the material by solid-state sintering. Although this method can also improve the effect to a certain extent, because the sintering temperature cannot reach the metal oxide It is difficult to embed the metal oxide into the NCM matrix, so the obtained NCM doped material is basically a mixed material of metal oxide and NCM in terms of crystal structure, rather than a solid solution, so that an ideal dopant cannot be formed. , cannot structurally suppress Li / Ni mixing

The currently commonly used substances for coating are mostly metal or non-metal oxides, which can improve the performance of the material to a certain extent, but these substances are generally not electrochemically active, which will hinder the deintercalation of lithium ions during the charge and discharge process, resulting in high capacity. decline

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