Overlithiated Lithium Transition Metal Oxide Coated with Polymer for Battery Stability
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Solution Overview
Problem
Current positive active materials for lithium batteries, such as LiNiO2, LiCoO2, and LiMn2O4, have limited electrical capacity and suffer from capacity degradation during charge and discharge cycles due to structural changes, making them unsuitable for high-capacity applications.
Innovation Solution
A positive active material comprising an overlithiated lithium transition metal oxide core coated with a polymer layer having an oxidation potential of 4.4 to 4.7 volts versus lithium metal, which stabilizes the structure and improves lifetime characteristics during high voltage operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional positive active materials (LiNiO2, LiCoO2, LiMn2O4) are used, then the battery can operate with simple material composition, but the electrical capacity is limited and structural instability occurs during charge-discharge cycles
Solution Approach 1:
The patent applies composite materials by combining overlithiated lithium transition metal oxide core with a protective coating layer. The core material (xLi2MO3-(1-x)LiM′O2 where 0<x<0.5) provides high electrical capacity through dual-phase structure, while the coating layer protects against structural degradation. This composite structure resolves the contradiction by enabling both high capacity and structural stability during charge-discharge cycles.
Solution Approach 2:
The patent utilizes parameter changes by controlling the composition ratio parameter x in the formula xLi2MO3-(1-x)LiM′O2. By optimizing this parameter within the range 0<x<0.5, the material achieves optimal balance between capacity and stability. Additionally, the oxidation state parameter of transition metals is controlled to maintain structural integrity while enabling high capacity operation.
2Quantity of substance
If high voltage operation is implemented to increase capacity, then electrical capacity improves, but oxidation and structural degradation occur reducing lifetime
Solution Approach 1:
The patent introduces a coating layer as an intermediary between the positive active material and the electrolyte. This coating layer acts as a protective barrier that prevents direct contact and chemical reactions at high voltages, thereby preventing oxidation and structural degradation. The intermediary layer enables high voltage operation for increased capacity while protecting the underlying material, thus improving lifetime characteristics.
3Quantity of substance
If overlithiated lithium transition metal oxide is used to increase capacity, then electrical capacity improves, but structural changes occur during cycling reducing reliability
Solution Approach 1:
The patent employs composite materials structure where overlithiated lithium transition metal oxide (xLi2MO3-(1-x)LiM′O2) serves as the core providing high capacity, while an outer coating layer provides structural protection. The dual-phase core structure itself also contributes to stability by distributing mechanical stress during lithium insertion/extraction. This composite approach enables the material to achieve high capacity while maintaining structural stability during charge-discharge cycling.
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 coated positive active material enhances the lithium battery's capacity and stability, maintaining high performance over multiple charge and discharge cycles by preventing structural instability and oxidation at high voltages.
Implementation Method 1
a coating layer which is disposed on at least a portion of a surface of the core, the coating layer including a polymer having an oxidation potential of about 4.4 volts to about 4.7 volts versus lithium metal
Data Source
AI summary
A positive active material including: a core including an overlithiated lithium transition metal oxide, and a coating layer which is disposed on at least a portion of a surface of the core, the coating layer including a polymer having an oxidation potential of about 4.4 volts to about 4.7 volts versus lithium metal. Also a manufacturing method thereof, and a positive electrode and a lithium battery including the positive active material.