Lithium Manganese Battery Phosphite Protective Layer
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Solution Overview
Problem
Spinel-type manganese-based positive active materials in rechargeable lithium batteries suffer from low capacity and deteriorated cycle life due to manganese ion elution and disproportionation reactions, especially at high temperatures, which affect thermal stability and storage safety.
Innovation Solution
A rechargeable lithium battery design incorporating a lithium manganese-based positive active material with a phosphite-based protective layer and an additive that forms a solid electrolyte interface layer, enhancing thermal stability and cycle life by suppressing manganese ion elution and improving electrode stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If spinel-type manganese-based positive active material is used, then thermal stability and environmental safety are improved, but capacity and cycle life deteriorate due to manganese ion elution
Solution Approach 1:
The patent applies composite materials by combining spinel-type manganese-based positive active material with a protective layer made of lithium cobalt oxide or lithium nickel cobalt oxide. This composite structure maintains the thermal stability benefits of manganese-based materials while the protective layer prevents manganese ion elution, thereby improving cycle life and reliability without sacrificing thermal safety
Solution Approach 2:
The protective layer acts as an intermediary between the manganese-based positive active material and the electrolyte. This intermediary layer blocks the direct contact that causes manganese ion elution and disproportionation reactions, while still allowing lithium ion transport, thus resolving the contradiction between maintaining thermal stability and improving cycle life
2Reliability
If manganese substitution with nickel or cobalt is performed, then manganese elution is reduced, but manufacturing cost increases
Solution Approach 1:
Instead of substituting manganese with expensive nickel or cobalt throughout the bulk material, the patent uses a protective layer as an intermediary that selectively blocks manganese elution at the surface-electrolyte interface. This approach achieves the same protective effect as full substitution but at lower manufacturing cost by treating only the surface region
3Reliability
If HF neutralizing materials are added to electrolyte, then manganese elution is suppressed, but battery performance deteriorates
Solution Approach 1:
The patent replaces HF neutralizing electrolyte additives with a solid protective layer intermediary on the positive electrode surface. This protective layer directly blocks manganese ion elution at the source without introducing HF-neutralizing chemicals that can deteriorate battery performance, thus achieving manganese suppression while maintaining high productivity and performance
4Reliability
If lithium cobalt oxide coating is applied, then manganese elution is reduced, but manufacturing complexity increases
Solution Approach 1:
The patent uses composite materials formed through a simple co-precipitation process that simultaneously creates the protective layer and incorporates it with the manganese-based positive active material. This approach achieves manganese elution reduction without requiring complex multi-step coating processes, thereby reducing manufacturing complexity while maintaining reliability
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 improves the thermal stability and cycle life of the battery by forming a protective layer that reduces manganese ion elution and maintains high capacity retention even at elevated temperatures, thereby enhancing storage safety and performance.
Implementation Method 1
the protective layer includes a decomposition product of a phosphite-based compound
Implementation Method 2
an additive that forms a solid electrolyte interface layer
Implementation Method 3
Rechargeable lithium batteries have recently drawn attention as a power source for small portable electronic devices
Data Source
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AI summary
A rechargeable lithium battery includes a positive electrode including a current collector, a positive active material layer on the current collector and including a lithium manganese-based positive active material, and a protective layer on the positive active material layer and including a phosphite-based compound; a negative electrode; and an electrolyte coupled with the positive electrode and the negative electrode and including a lithium salt, a non-aqueous solvent, and an additive.