Lithium-Ion Cathode Coating for Transition Metal Dissolution Control
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Solution Overview
Problem
Lithium-ion positive electrode materials experience surface structural abnormalities under high voltage and high temperature conditions, leading to significant performance degradation due to the dissolution of active transition metal elements and the inability of traditional oxide coatings to stabilize these elements.
Innovation Solution
A coating layer comprising an anchoring layer and a stabilizing layer is applied to lithium transition metal oxide particles, where the anchoring layer is formed by inducing sulfur elements with lower average valence to anchor active elements, and the stabilizing layer is formed by inducing sulfur elements with higher average valence to enhance electrochemical activity and stability, thereby reducing transition metal dissolution to ≤4000ppm.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If traditional oxide coating is applied to lithium transition metal oxide particles, then surface structural stability is improved, but transition metal dissolution is not effectively prevented under high voltage and high temperature conditions
Solution Approach 1:
The coating layer is divided into two distinct functional layers: an anchoring layer containing sulfur elements with lower average valence to bond with transition metals, and a stabilizing layer containing sulfur elements with higher average valence to protect the anchoring layer and provide electrochemical stability. This segmentation allows each layer to specialize in its function, effectively preventing transition metal dissolution while maintaining surface stability.
Solution Approach 2:
The invention uses a composite coating structure combining different sulfur-valence layers on the lithium transition metal oxide surface. The anchoring layer and stabilizing layer form a composite material system where the lower valence sulfur anchors transition metals through chemical bonding, while the higher valence sulfur provides protective coverage and electrochemical stability, achieving synergistic effect against dissolution.
2Loss of substance
If coating layer thickness is increased to improve transition metal anchoring, then dissolution resistance is improved, but ionic and electronic conductivity may be reduced
Solution Approach 1:
Different regions of the coating layer are designed with different sulfur valences and thicknesses optimized for their specific functions. The anchoring layer has sufficient thickness to effectively bond with transition metals, while the stabilizing layer provides protective coverage. This local optimization ensures adequate dissolution resistance without excessive thickness that would harm conductivity.
Solution Approach 2:
The invention optimizes the thickness parameters of each coating layer and controls the sulfur element valence distribution to achieve the right balance. By adjusting these parameters, the coating provides adequate transition metal anchoring and protection while maintaining sufficient ionic and electronic conductivity for electrochemical performance.
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 coated positive electrode active material exhibits improved ionic and electronic conductivity, higher capacity, lower internal resistance, and enhanced cycle stability, with reduced transition metal dissolution and better structural stability under extreme conditions.
Implementation Method 1
the anchoring layer is configured to anchor active elements in the lithium transition metal oxide particles
Implementation Method 2
the anchoring layer and the stabilizing layer comprise sulfur elements, an average valence of the sulfur elements contained in the stabilizing layer is greater than an average valence of the sulfur elements contained in the anchoring layer
Data Source
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AI summary
The present application relates to a positive electrode active material and a method for preparing thereof, a positive electrode, a lithium-ion battery, and an electrical device. In the positive electrode active material provided by the present application, an anchoring layer is coated on the surface of the substrate, wherein sulfur elements with lower average valence may be chemically bonded with active elements (transition metals, B, or the like) in lithium transition metal oxide particles, thereby effectively stabilizing metal active sites on the surface of the positive electrode active material, and weakening the dissolution of the transition metal on the surface caused by the reaction between surface active transition metal elements with electrolyte solution. The stabilizing layer laminated on the anchoring layer can protect the anchoring layer, and the stabilizing layer has higher electrochemical activity, which can effectively inhibit the polarization of the material, and the stabilizing layer cooperates with the anchoring layer to make the positive electrode active material provided in the present application have both higher ionic conductivity and electronic conductivity, and can significantly improve electrochemical performances of the positive electrode active material, including high capacity, low internal resistance and high cycle stability.