Positive Electrode Composition With Dual Coating for Mn Dissolution Control
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Solution Overview
Problem
Lithium manganese iron phosphate materials exhibit poor electrochemical performance due to their insulating nature and are prone to lattice deformation and Mn2+ ion dissolution, leading to degraded cycling and storage performance in batteries.
Innovation Solution
A positive electrode active material composition combining a first and second positive electrode material, with a defined ratio of coating layer thickness to particle size and controlled Mn content, enhances conductivity and suppresses Mn2+ ion dissolution, thereby improving cycling and storage performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If lithium manganese iron phosphate material is used as positive electrode active material, then high voltage plateau and energy density are achieved, but the material is almost an insulator and electrochemical performance is poor
Solution Approach 1:
The patent uses composite materials by combining lithium manganese iron phosphate core with a dual-layer coating system (phosphate layer and carbon layer). The phosphate layer provides chemical stability and suppresses Mn2+ dissolution, while the carbon layer provides electrical conductivity. This composite structure resolves the contradiction by maintaining the high energy density of the LMFP core while adding functional layers that enable electrochemical performance.
2Reliability
If coating layer is applied to increase electronic conductivity and suppress Mn2+ ion dissolution, then cycling performance is improved, but the coating layer reacts with electrolyte in high-SOC storage stage, deteriorating storage performance
Solution Approach 1:
The patent applies local quality by creating a dual-layer coating structure where each layer has different properties and functions. The inner phosphate layer (0.5-2 nm) provides chemical stability and Mn2+ suppression, while the outer carbon layer (1-5 nm) provides electrical conductivity and acts as a barrier to electrolyte reaction. This localized functional differentiation allows the coating to simultaneously improve cycling performance while reducing harmful reactions during storage.
Solution Approach 2:
The patent optimizes the thickness parameters of both coating layers to achieve the desired balance. By controlling the phosphate layer thickness at 0.5-2 nm and carbon layer thickness at 1-5 nm, the patent achieves sufficient protection against Mn2+ dissolution and electrolyte reaction while minimizing the total coating thickness that could react with electrolyte. This parameter optimization resolves the contradiction between cycling performance improvement and storage performance preservation.
3Reliability
If coating layer thickness is increased to suppress Mn2+ ion dissolution, then cycling performance improves, but storage performance deteriorates due to increased reaction with electrolyte
Solution Approach 1:
The patent uses composite materials by combining lithium manganese iron phosphate core with a dual-layer coating system (phosphate layer and carbon layer). The phosphate layer provides chemical stability and suppresses Mn2+ dissolution, while the carbon layer provides electrical conductivity. This composite structure resolves the contradiction by maintaining the high energy density of the LMFP core while adding functional layers that enable electrochemical performance.
4Reliability
If the ratio of coating layer thickness to particle size is increased, then Mn2+ ion dissolution is suppressed, but the material becomes more insulating
Solution Approach 1:
The patent applies local quality by creating a dual-layer coating structure where each layer has different properties and functions. The inner phosphate layer (0.5-2 nm) provides chemical stability and Mn2+ suppression, while the outer carbon layer (1-5 nm) provides electrical conductivity and acts as a barrier to electrolyte reaction. This localized functional differentiation allows the coating to simultaneously improve cycling performance while reducing harmful reactions during storage.
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 proposed composition effectively reduces reactions with the electrolyte, suppresses Mn2+ ion dissolution, and enhances the voltage plateau, resulting in improved battery cycling and storage performance.
Implementation Method 1
Coated lithium manganese iron phosphate is conducive to increasing the electronic conductivity of the material
Implementation Method 2
suppressing the dissolution of Mn2+ ions
Data Source
AI summary
A positive electrode active material composition, a positive electrode plate, a battery, and an electric apparatus are described. The positive electrode active material composition includes a first positive electrode active material and a second positive electrode active material, where the first positive electrode active material includes a core LiaAbMnfB1-fP1-dRdO4-nDn and a coating layer covering the core. The coating layer comprises one or more of pyrophosphate, phosphate, and carbon. The second positive electrode active material includes a compound LiNixCoyM1-x-yO2; and 0.018m+0.003f≤z≤0.02m+0.02f is satisfied.