Lithium manganese nickel oxide cathode material having nickel manganese concentration gradient and preparation method thereof

Abstract

The invention discloses a lithium manganese nickel oxide cathode material having nickel manganese concentration gradient and a preparation method thereof. The average chemical composition of the lithium manganese nickel oxide cathode material can be shown as a molecular formula of LiNi<0.5-x>Mn<1.5+x>O<4>, wherein x is more than or equal to 0.1 and less than or equal to 0.35, the concentration of Ni is gradually reduced in a gradient distribution manner from the particle center to the particle surface of the lithium manganese nickel oxide cathode material, and the concentration of Mn is gradually reduced in a gradient distribution manner from the particle center to the particle surface of the lithium manganese nickel oxide cathode material. The preparation method comprises the following steps of firstly, synthesizing a spherical-like particle having a core-shell structure by a co-precipitation process; and finally, preparing the lithium manganese nickel oxide cathode material with change on the nickel and manganese concentration by element diffusion during the high-temperature roasting process. The cathode material disclosed by the invention has excellent high-temperature cycle stability and rate performance, high reversible capacity, high chemical stability, long cycle life, and excellent comprehensive electrochemical performance.

Description

technical field [0001] The invention belongs to the technical field of lithium-ion battery electrode materials, and in particular relates to a lithium-nickel-manganese oxide cathode material with a nickel-manganese concentration gradient and a preparation method thereof. Background technique [0002] The large-scale application of lithium-ion batteries in electric vehicles and large-scale energy storage devices has put forward higher requirements for their energy density, power, service life and safety. Compared with other cathode materials, the cathode material LiNi with spinel structure 0.5 mn 1.5 o 4 The discharge platform is as high as 4.7V, which is comparable to the current commercial cathode material LiCoO 2 Compared with the energy density increased by 20%, so LiNi 0.5 mn 1.5 o 4 It has become a candidate cathode material for high energy density lithium-ion batteries. However, the high voltage cathode material LiNi 0.5 mn 1.5 o 4 The poor cycle stability, e...

AI Technical Summary

Problems solved by technology

However, the core-shell structure design has brought many limitations to the improvement of the comprehensive chemical properties of high-voltage lithium nickel manganese oxide cathode materials.

In particular, in order to highlight the advantages of structural compatibility of core-shell materials and meet the requirements for material stability during cycling, the chemical compositions of the core and shell materials must be similar, that is, the core component LiNi 0.5-x mn 1.5+x o 4 with shell component LiNi 0.5 mn 1.5 o 4 The difference cannot be large, which limits the design of core components and overall materials, and limits the screening and optimization of material core components for higher capacity and excellent rate performance

At the same time, the core-shell material has an obvious core-shell interface. Although the core and shell materials belong to the cubic spinel phase, the disordered structure of the core Fd-3m With the phase transition between the two phases that occurs during charge and discharge, the ordered structure of the shell P4 3 32 A phase transition occurs between the three phases, and the stability of the core-shell structure faces a great challenge under long-term cycling conditions. The cracking or even falling off of the shell layer will lead to an increase in interface impedance and even material damage.

Images