Core-Shell Cathode Material Coating to Suppress Manganese Leaching
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Solution Overview
Problem
Lithium manganese phosphate positive electrode materials suffer from manganese ion leaching during charging, leading to rapid capacity decay and reduced safety and performance in secondary batteries.
Innovation Solution
A core-shell structured positive electrode active material is developed, comprising a core with specific doping elements and coated with electron-withdrawing polymers and polysaccharides, which reduces manganese leaching and enhances stability and performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If LiCoO2 is used as the positive electrode active material to achieve high output, then the battery capacity can reach theoretical limits, but structural instability occurs at potentials above 4.3V versus Li/Li+, leading to poor cycle characteristics
Solution Approach 1:
The patent uses a composite coating structure where a spinel compound layer (containing Co, Mn, and Al) is formed on the surface of LiCoO2 particles, and an oxide layer is formed on the spinel compound. This multi-layer composite structure provides both high capacity utilization and structural stability during cycling, resolving the contradiction between achieving theoretical capacity and maintaining cycle life.
Solution Approach 2:
The patent controls the potential range during charging to be 4.2V or lower versus Li/Li+, avoiding the unstable region above 4.3V. By changing the operating potential parameter and forming a protective coating, the material maintains structural stability while still achieving high battery capacity through optimized charge-discharge protocols.
2Quantity of substance
If LiNi0.8Co0.1Mn0.1O2 is used as the positive electrode active material to achieve high output, then battery capacity increases, but the material becomes unstable in air and exhibits poor cycle characteristics
Solution Approach 1:
The patent applies a dual-layer coating to LiNi0.8Co0.1Mn0.1O2 particles: a spinel compound layer (Co, Mn, Al) and an outer oxide layer. This composite structure protects the unstable NCM material from air exposure while enabling high capacity utilization and improving cycle stability through the protective barrier.
Solution Approach 2:
The oxide layer formed on the outer surface acts as a protective barrier that creates an inert environment for the underlying NCM material, preventing degradation from air exposure and electrolyte contact, thereby improving both air stability and cycle characteristics.
3Reliability
If conventional coating methods are used to improve cycle characteristics, then battery assembly costs increase, but the patent's method increases production complexity
Solution Approach 1:
The patent combines the coating formation and sintering steps into a single integrated process. The coating slurry is applied to the positive electrode precursor, and both coating formation and sintering are performed in one heat treatment step, simplifying the overall production process while achieving the desired protective coating and high cycle characteristics.
Solution Approach 2:
The coating slurry composition is designed to form the protective spinel and oxide layers during the sintering process itself, without requiring separate coating and firing steps. The materials in the slurry self-organize and react during sintering to create the desired multi-layer structure.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution significantly improves rate performance, cycling performance, and high-temperature stability of secondary batteries by minimizing manganese leaching and electrolyte erosion, while maintaining high energy density.
Implementation Method 1
a positive electrode active material for secondary batteries having a specific oxidation-reduction reaction
Implementation Method 2
when a spinel compound coating layer is formed on a surface of the positive electrode active material, it is considered that a period of time required until the positive electrode active material is degraded can be extended
Data Source
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AI summary
A positive electrode active material, a method for preparation thereof and a positive electrode plate, a secondary battery and an electrical device containing the same are provided. The positive electrode active material has a core-shell structure, comprising a core, a first cladding layer covering the core, a second cladding layer covering the first cladding layer, wherein the core has a chemical formula of LiaAxMn1-yByP1-zCzO4-nDn, the first cladding layer comprises a first polymer containing an electron withdrawing group, the second cladding layer comprises a second polymer, and wherein the second polymer comprises one or more of plant polysaccharides, marine polysaccharides and the derivatives thereof. The positive electrode active material of the present application enables a secondary battery to have a relatively high energy density, while further having a significantly improved rate performance, cycling performance and/or high-temperature stability.