Positive Electrode Material Coating to Suppress Paste Gelation
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Solution Overview
Problem
Existing non-aqueous electrolyte secondary battery positive electrode active materials face challenges with gelation during electrode manufacture, which affects battery capacity and output characteristics, and existing solutions either compromise safety or increase raw material costs.
Innovation Solution
A positive electrode active material with a hexagonal layered crystal structure, represented by Li1+sNixCoyMnzMwBtO2+α, where a lithium-boron compound is present on the surfaces of primary particles, reducing lithium hydroxide elution and moisture content, thereby suppressing gelation and enhancing battery performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a lithium-metal composite oxide is used as a positive electrode material to achieve high voltage and high energy density, then battery energy density is improved, but gelation of the positive electrode mixture paste occurs during manufacture
Solution Approach 1:
An alumina coating layer is applied as an intermediary between the lithium-metal composite oxide particles and the binder in the positive electrode mixture paste. This coating layer acts as a barrier that prevents direct interaction between excessive lithium and the binder, thereby suppressing gelation while maintaining the high energy density benefits of the lithium-metal composite oxide material.
Solution Approach 2:
The invention controls the amount of excessive lithium in the lithium-metal composite oxide within a specific range (0.01-0.50 mol per 1 mol of metal elements) and adjusts the alumina content in the coating layer (1-10 wt% relative to positive electrode active material). By optimizing these parameters, the gelation problem is suppressed while maintaining high battery energy density.
2Reliability
If excessive lithium is added to improve charge and discharge cycle characteristics, then cycle characteristics are improved, but gelation of the positive electrode mixture paste is promoted
Solution Approach 1:
The alumina coating layer serves as a protective intermediary that allows excessive lithium to be present for improved cycle characteristics while preventing the lithium from causing gelation. The coating layer decouples the beneficial effect of excessive lithium on cycle life from its harmful effect on paste stability.
Solution Approach 2:
The invention optimizes the amount of excessive lithium within a specific range (0.01-0.50 mol per 1 mol of metal elements) and combines it with alumina coating to achieve the desired balance between cycle characteristics and gelation suppression.
3Power
If a compound containing boron is added to improve conductivity and output characteristics, then output characteristics are improved, but gelation of the positive electrode mixture paste is promoted
Solution Approach 1:
The alumina coating layer acts as a mediator that allows boron compounds to be added for improved output characteristics while preventing the boron-containing compounds from causing gelation. The coating layer isolates the boron compounds from direct contact with the binder.
Solution Approach 2:
The invention creates a composite structure with a lithium-metal composite oxide core and an alumina coating shell. This composite material approach allows multiple functions to be integrated: the core provides high voltage and energy density, while the shell suppresses gelation and enables safe addition of boron compounds for improved output characteristics.
4Object-generated harmful factors
If alumina is added to suppress gelation of the positive electrode mixture paste, then gelation is suppressed, but battery capacity is reduced
Solution Approach 1:
Instead of uniformly distributing alumina throughout the electrode mixture, the invention applies alumina as a localized coating layer on the surface of each lithium-metal composite oxide particle. This localized approach suppresses gelation at the particle-binder interface while minimizing the overall amount of alumina needed, thereby preserving battery capacity.
Solution Approach 2:
The invention optimizes the alumina content in the coating layer (1-10 wt% relative to positive electrode active material) to achieve the minimum necessary amount for gelation suppression. This controlled parameter approach prevents excessive alumina from reducing battery capacity while ensuring sufficient coating for gelation prevention.
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 effectively improves battery capacity and output characteristics while preventing gelation of the positive electrode mixture paste, ensuring high stability and suitability for industrial-scale production.
Implementation Method 1
a lithium-boron compound is present on the surfaces of primary particles, reducing lithium hydroxide elution and moisture content
Implementation Method 2
a lithium-boron compound is present on at least a part of surfaces of the primary particles
Data Source
AI summary
An object is to provide a positive electrode active material for a non-aqueous electrolyte secondary battery that can suppress gelation of a positive electrode mixture paste and can improve stability when a non-aqueous electrolyte secondary battery is manufactured. A positive electrode active material for a non-aqueous electrolyte secondary battery has a hexagonal layered crystal structure, is represented by general formula (1): Li1+sNixCoyMnzMwBtO2+α, and includes a lithium-metal composite oxide containing a secondary particle with a plurality of aggregated primary particles and a lithium-boron compound present on at least a part of surfaces of the primary particles. The amount of lithium hydroxide that elutes when the positive electrode active material is dispersed in water, measured by a neutralization titration method, is 0.01% by mass or more and 0.5% by mass or less with respect to the entire positive electrode active material.