Lithium Manganese Phosphate Cathode Shells to Limit Mn Leaching
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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 gas production, limiting their commercialization.
Innovation Solution
A secondary battery with a core-shell structure positive electrode active material, where the core has a chemical formula of Li1+xMn1-yAyP1-zRzO4 and is clad with multiple layers of crystalline pyrophosphate and phosphate salts, along with a carbon layer, and the non-aqueous electrolyte contains specific additives to form a sulfur-containing polymer, enhancing lithium ion conductivity and reducing manganese ion leaching.
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 combined with a protective shell layer. The shell layer, composed of lithium phosphate and lithium pyrophosphate, forms a composite material system that prevents manganese ion leaching while maintaining the high capacity characteristics of the original lithium manganese phosphate material.
Solution Approach 2:
The patent uses a thin film shell structure to protect the lithium manganese phosphate core. The shell layer, with controlled thickness and composition, acts as a flexible barrier that prevents harmful manganese ion leaching during charging cycles while allowing lithium ion transport, thus resolving the contradiction between maintaining capacity and preventing capacity decay.
2Quantity of substance
If lithium manganese phosphate is used as positive electrode active material, then high capacity is achieved, but interfacial side reactions and gas production occur resulting in safety concerns
Solution Approach 1:
The patent employs a protective shell film that acts as a physical barrier between the lithium manganese phosphate core and the electrolyte. This shell prevents interfacial side reactions and suppresses gas production by eliminating direct contact between the reactive lithium manganese phosphate and the electrolyte, thereby improving safety performance while preserving capacity.
Solution Approach 2:
The shell layer serves as an intermediary between the lithium manganese phosphate core and the electrolyte. It mediates the interaction by providing a stable interface that prevents harmful side reactions and gas generation, allowing the system to maintain high capacity without safety concerns.
3Reliability
If multiple cladding layers are applied to reduce manganese ion leaching, then cycle performance and safety are improved, but manufacturing complexity increases
Solution Approach 1:
The patent segments the protective shell into multiple functional layers: an inner shell layer of lithium phosphate and an outer shell layer of lithium pyrophosphate. Each layer performs specific functions - the inner layer provides primary protection against manganese ion leaching, while the outer layer enhances stability and prevents side reactions. This segmentation improves cycle performance and safety while keeping the manufacturing process manageable through clear functional division.
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
This configuration improves the battery's energy density, rate performance, cycle performance, and safety by reducing manganese ion leaching and interfacial side reactions, while maintaining high capacity and stability over long charge and discharge cycles.
Implementation Method 1
lithium manganese phosphate is prone to manganese ion leaching out during charging, resulting in rapid capacity decay
Implementation Method 2
the non-aqueous electrolytic solution contains specific additives to form a sulfur-containing polymer, enhancing lithium ion conductivity
Implementation Method 3
safety concerns due to interfacial side reactions and gas production
Data Source
AI summary
The present application provides a secondary battery and a battery module, battery pack and electrical device containing the same. The secondary battery comprises a positive electrode plate and an non-aqueous electrolytic solution, wherein the positive electrode plate comprises a positive electrode active material with a core-shell structure, said positive electrode active material comprising an core and a shell covering said core, said core has a chemical formula of Li1+xMn1-yAyP1-zRzO4; said shell comprises a first cladding layer covering said core, a second cladding layer covering said first cladding layer and a third cladding layer covering said second cladding layer, said non-aqueous electrolytic solution comprises a first additive, said first additive comprises one or more of compounds as shown by Formula 1, Formula 2 and Formula 3.