LMFP Core-Shell Cathode Material for Conductivity and Cycle Stability
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Solution Overview
Problem
Lithium manganese iron phosphate (LMFP) materials face challenges with low electrical conductivity, manganese dissolution, and hygroscopicity, which hinder the achievement of high energy density and cycle stability in lithium-ion batteries.
Innovation Solution
A core-shell structured positive electrode material is developed, comprising a lithium manganese iron phosphate core coated with a manganese-free polyanionic shell layer and a hydrophobic conductive shell layer, enhancing electrical conductivity and reducing manganese dissolution and water content.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If lithium manganese iron phosphate material is used to achieve higher energy density, then energy density is improved, but electrical conductivity deteriorates
Solution Approach 1:
The patent applies composite materials by coating the lithium manganese iron phosphate core with a polyanionic material shell layer. This composite structure combines the high energy density advantage of LMFP with the high electrical conductivity and stability of polyanionic materials, effectively resolving the contradiction between energy density and electrical conductivity.
Solution Approach 2:
The patent implements local quality by creating a core-shell structure where the surface region (shell layer) has different properties from the core. The polyanionic shell layer provides high conductivity and stability at the surface, while the LMFP core maintains high energy density, thus resolving the conductivity issue locally without sacrificing overall energy density.
2Use of energy by moving object
If lithium manganese iron phosphate material is used to achieve higher energy density, then energy density is improved, but cycle stability deteriorates due to manganese dissolution
Solution Approach 1:
The patent uses composite materials by forming a core-shell structure where the polyanionic shell layer acts as a protective barrier. This composite structure prevents manganese dissolution into the electrolyte while maintaining the high energy density of the LMFP core, thereby improving cycle stability without sacrificing energy density.
Solution Approach 2:
The patent converts the harmful effect of manganese dissolution into a benefit by using the polyanionic shell layer to capture and stabilize manganese ions. The shell layer transforms the potential harm of manganese dissolution into a protective mechanism that enhances cycle stability while preserving the high energy density advantage.
3Use of energy by moving object
If lithium manganese iron phosphate material is used, then energy density is improved, but hygroscopicity increases leading to high water content
Solution Approach 1:
The patent applies composite materials by coating the hygroscopic LMFP core with a hydrophobic polyanionic shell layer. This composite structure creates a hydrophobic barrier that prevents water absorption, thereby eliminating the hygroscopicity problem while maintaining the high energy density of the underlying LMFP material.
Solution Approach 2:
The patent implements local quality by modifying only the surface region with a hydrophobic polyanionic shell layer. This local modification creates a water-repellent surface that prevents hygroscopicity, while the bulk LMFP core retains its high energy density properties, thus resolving the contradiction between energy density and hygroscopicity.
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 improves the electrical conductivity, cycle stability, and C-rate performance of lithium manganese iron phosphate materials, while maintaining low water content, thereby addressing the limitations of LMFP in lithium-ion batteries.
Implementation Method 1
The second shell layer includes a hydrophobic conductive material... is hydrophobic and conductive to a relatively high degree... alleviates the problem of high hygroscopicity
Implementation Method 2
The first shell layer includes a polyanionic positive electrode material... improves the electrical conductivity of the lithium manganese iron phosphate material
Data Source
AI summary
Provided are a positive electrode material and a preparation method thereof, a composite positive electrode material, a positive electrode plate, and a secondary battery. The positive electrode material includes: a core, a first shell layer, and a second shell layer. The first shell layer wraps around a surface of the core. The second shell layer wraps around a surface of the first shell layer. The core includes a lithium manganese iron phosphate material. The first shell layer includes a polyanionic positive electrode material. The polyanionic positive electrode material contains no manganese. The second shell layer includes a hydrophobic conductive material. When ensuring a relatively high energy density of the lithium manganese iron phosphate material, the positive electrode material improves the electrical conductivity of the lithium manganese iron phosphate material, alleviates the problem of hygroscopicity, and reduces manganese dissolution during cycling.