Core-Shell Lithium Manganese Phosphate Cathode With Stable Interface Film
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Solution Overview
Problem
Lithium manganese phosphate secondary batteries face issues with manganese ion leaching during charging, leading to rapid capacity decay and safety concerns due to interfacial side reactions and non-aqueous electrolyte consumption.
Innovation Solution
A secondary battery with a core-shell positive electrode active material structure, comprising a lithium manganese phosphate core doped with elements like Zn, Al, and Si, coated with multiple layers of crystalline pyrophosphate and phosphate, and a carbon layer, along with specific additives in the non-aqueous electrolyte to form a stable interface film, reducing manganese ion dissolution and enhancing cycling and storage performance.
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 patent applies composite materials by creating a core-shell structure where lithium manganese phosphate core is coated with lithium iron phosphate shell. This composite structure combines the high capacity advantage of lithium manganese phosphate with the structural stability and low manganese leaching characteristics of lithium iron phosphate, thereby resolving the contradiction between high capacity and rapid capacity decay
Solution Approach 2:
The patent applies local quality by doping specific elements (Al, Si, Zn) at particular locations within the lithium manganese phosphate crystal structure. This localized modification enhances structural stability and suppresses manganese ion leaching in critical regions while maintaining the overall high capacity characteristics of the material
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 interfacial side reactions and non-aqueous electrolyte consumption
Solution Approach 1:
The patent applies the intermediary principle by introducing lithium iron phosphate as a protective coating layer between the lithium manganese phosphate active material and the non-aqueous electrolyte. This intermediary layer acts as a barrier that prevents direct contact and harmful interfacial side reactions, thereby improving safety performance while maintaining high capacity
Solution Approach 2:
The patent applies preliminary anti-action by pre-forming a stable solid electrolyte interface (SEI) film through electrolyte additives (sulfonic acid lactone and cyclic sulfate) before harmful reactions can occur. This preliminary protective action prevents subsequent decomposition reactions and improves safety performance
3Reliability
If multi-layer coating structure is applied to reduce manganese ion leaching, then cycling performance is improved, but device complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the protective coating into multiple functional layers: an inner layer of lithium iron phosphate for structural stability and manganese leaching prevention, and an outer layer with carbon coating for conductivity enhancement. This segmented structure addresses cycling performance requirements while keeping each layer relatively simple in composition
4Reliability
If electrolyte additives are used to form stable interface film, then storage performance and safety are improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent applies parameter changes by optimizing the concentration ratios of electrolyte additives (sulfonic acid lactone and cyclic sulfate) to achieve stable interface film formation. By carefully controlling the additive parameters within specific ranges, the patent improves storage performance while managing manufacturing precision requirements
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 reduces manganese ion leaching, improves rate and cycling performance, and enhances safety by forming a stable interface film, thereby maintaining high energy density and capacity retention.
Implementation Method 1
reduces the dissolution of the first and second coating layers, reduces the leaching-out of manganese ions
Implementation Method 2
it can form a dense and stable interface film on the surface of the positive active material during the secondary battery charging process
Implementation Method 3
reduce the catalytic oxidation of the third coating layer under high voltage
Data Source
AI summary
This application provides a secondary battery, and providing a battery module, a battery pack, and a powder device comprising the same. The secondary battery includes a positive electrode plate and a non-aqueous electrolytic solution, in which the positive electrode plate includes a positive electrode active material having a core-shell structure, said positive electrode active material includes an inner core and a shell covering the core, said core has a chemical formula of Li1+xMn1-yAyP1-zRzO4, said shell includes a first coating layer covering said core, a second coating layer covering said first coating layer, and a third coating layer covering said second coating layer. The secondary battery of the present application can have a relatively high energy density, and also a good rate performance, cycling performance, storage performance and safety performance.