Coated High-Nickel Cathode Material for Rate and Hot-Cycle Stability
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Solution Overview
Problem
The reduction of cobalt content in cathode materials to increase nickel content for higher energy density leads to deterioration in rate performance and high-temperature cycle performance.
Innovation Solution
A cathode material with an inner core of LiNi a Co b Mn c Q d O 2 and a coating layer of Li m Co n X (1-n) O 2, where Q and X elements enhance oxygen-fixation and interface stability, respectively, improving structural stability and Li+ transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If nickel content is increased to maximize specific capacity, then energy density is improved, but rate performance and high-temperature cycle performance deteriorate
Solution Approach 1:
The cathode material is divided into an inner core region with high nickel content (0.89≤a≤0.98) for maximizing specific capacity and energy density, and an outer shell region with reduced nickel content and added protective elements (Al, W, Ti, B, La) for improving rate performance and high-temperature cycle performance. This spatial segmentation allows each region to fulfill its specific function without compromising the other.
Solution Approach 2:
Different regions of the cathode particles are given different chemical compositions and properties: the inner core has high nickel content for capacity, while the outer shell has enhanced stability and protective elements for performance under stress conditions. This local quality differentiation resolves the contradiction by optimizing each region for its specific role.
2Use of energy by moving object
If cobalt content is reduced to increase nickel content, then energy density is improved, but structural stability and Li+ transmission deteriorate
Solution Approach 1:
The patent modifies the chemical composition parameters by introducing protective elements (Al, W, Ti, B, La) into the outer shell region while maintaining high nickel content in the inner core. This parameter change allows the material to achieve both high specific capacity and improved structural stability with enhanced Li+ transmission, particularly under high-temperature conditions.
Solution Approach 2:
The cathode material is designed as a composite structure combining high-nickel layered oxide in the core with a protective shell containing stabilizing elements. This composite approach allows the material to simultaneously achieve high specific capacity from the nickel-rich core and improved structural stability and ion transmission from the protective shell composition.
Data Source
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AI summary
The present application relates to a cathode material and a preparation method therefor, a cathode plate and a secondary battery. The cathode material includes an inner core and a coating layer coated on at least part of a surface of the inner core, wherein the inner core includes a material with a chemical formula LiNiaCobMncQdO2, where Q element includes at least one of Zr and Al, 0.89≤a≤0.98, 0≤b≤0.06, 0≤c<0.11, d>0, and a+b+c+d=1, and the coating layer includes a material with a chemical formula LimConX(1-n)O2, where X element includes at least one of Al, W, Ti, B and La, 0<m≤1, and 0<n≤1. With such design, rate performance and cycle performance of the cathode material are effectively improved.