Core-Shell Lithium Manganese Phosphate Cathode for Capacity Retention
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Solution Overview
Problem
Lithium manganese phosphate secondary batteries suffer from rapid capacity decay due to manganese ion leaching during charging, which limits their commercialization and requires improved safety and performance.
Innovation Solution
A secondary battery with a positive electrode plate featuring a core-shell structure, where the core has a chemical formula of Li1+xMn1-yAyP1-zRzO4 and is clad with multiple layers of crystalline pyrophosphates, phosphates, and carbon, along with a non-aqueous electrolytic solution containing specific additives to reduce manganese ion leaching and enhance interfacial film formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If lithium manganese phosphate is used as positive electrode active material, then high capacity and abundant raw material sources are achieved, but manganese ion leaching occurs during charging resulting in rapid capacity decay
Solution Approach 1:
The positive electrode active material is segmented into a core-shell structure where the core contains lithium manganese phosphate particles and the shell contains aluminum oxide coating. This segmentation prevents manganese ion leaching from the core while maintaining the high capacity of lithium manganese phosphate, thereby resolving the contradiction between capacity and capacity decay.
Solution Approach 2:
A composite material is formed by combining lithium manganese phosphate core with aluminum oxide shell. The aluminum oxide acts as a protective barrier that prevents manganese ion dissolution into the electrolyte while allowing lithium ion transport, thus maintaining both high capacity and preventing rapid capacity decay.
2Quantity of substance
If lithium manganese phosphate is used as positive electrode active material, then high capacity is achieved, but safety performance deteriorates due to manganese ion leaching
Solution Approach 1:
The aluminum oxide shell acts as an intermediary layer between the lithium manganese phosphate core and the electrolyte. It mediates by preventing direct contact between manganese ions and the electrolyte, thereby eliminating the harmful effect of manganese ion leaching while preserving the high capacity of the active material.
Solution Approach 2:
The composite structure of lithium manganese phosphate core with aluminum oxide shell creates a safe configuration where the aluminum oxide provides protective function against manganese ion dissolution, thus achieving both high capacity and improved safety performance.
3Reliability
If multi-layer cladding structure is applied to reduce manganese ion leaching, then cycling performance and safety are improved, but device complexity increases
Solution Approach 1:
The protective shell is segmented into multiple functional layers: an inner aluminum oxide layer for manganese ion blocking and an outer carbon coating layer for conductivity enhancement. This segmentation achieves improved cycling performance and safety while keeping the overall structure relatively simple through functional differentiation.
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 achieves high energy density, good rate performance, cycling performance, storage performance, and safety performance by reducing manganese ion leaching and lattice change rates, thereby extending battery life and ensuring safety.
Implementation Method 1
the first additive can react with a trace amount of water in the non-aqueous electrolytic solution to form —NHCOOH, reduce the generation of HF, reduce the acidity of the non-aqueous electrolytic solution
Implementation Method 2
the first additive shown in Formula 1 is also capable of generating a uniform and dense interfacial film on the surface of the negative electrode active material, reducing the reduction reaction of the leached manganese ions at the negative electrode
Data Source
AI summary
The present application provides a secondary battery, a battery module, a battery pack and an electrical device containing the same. The secondary battery comprises a positive electrode plate, and a non-aqueous electrolytic solution, wherein the positive electrode plate comprises a positive electrode active material with a core-shell structure, which comprises a core and a shell covering the core, in which the core has a chemical formula of Li1+xMn1-yAyP1-zRzO4, and the shell comprises a first cladding layer covering the core, a second cladding layer covering the first cladding layer and a third cladding layer covering the second cladding layer, and the non-aqueous electrolytic solution comprises a first additive comprising one or more of the compounds shown in Formula 1. The present application enables the secondary battery to simultaneously have high energy density with good rate performance, cycling performance, storage performance and safety performance.