LiCoO2-LiMn2O4 Core-Shell Coating for Battery Stability
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Solution Overview
Problem
Current rechargeable lithium batteries face challenges in achieving a balance between cost-effectiveness, stability, high capacity, and electrical conductivity, particularly with manganese-based and nickel-based positive active materials, which have limitations in cycle life, thermal stability, and synthesis difficulties.
Innovation Solution
A positive active material for lithium batteries is developed by incorporating a coating particle with an embedded and protruding portion into the active material compound, where the coating particle is a metal oxide with specific volume and diameter ratios, enhancing structural stability and conductivity, and is heat-treated at a controlled temperature to optimize performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If manganese-based positive active materials are used, then cost is reduced and thermal stability is improved, but capacity is relatively low
Solution Approach 1:
The patent applies composite materials by combining LiCoO2 (providing high capacity and voltage) with LiMn2O4 (providing thermal stability and cost-effectiveness) to create a composite positive active material that achieves synergistic effects, simultaneously improving capacity, cycle life, and thermal stability
Solution Approach 2:
The patent applies local quality by creating a core-shell structure where LiMn2O4 forms an outer shell layer around LiCoO2 core particles. This localized arrangement allows the inner core to provide high capacity while the outer shell provides thermal stability and structural support, with each material performing its optimal function in its designated region
2Quantity of substance
If LiCoO2 is used, then electrical conductivity and discharge capacity are improved, but cost increases significantly
Solution Approach 1:
The patent creates a composite material system where LiCoO2 particles are coated with LiMn2O4, allowing the expensive LiCoO2 to provide high discharge capacity and conductivity in a smaller volume, while the cheaper LiMn2O4 forms the bulk of the material structure, reducing overall cost while maintaining performance
Solution Approach 2:
The patent uses LiMn2O4, a more cost-effective material, as the outer shell that can be synthesized more easily and at lower cost, reducing the amount of expensive LiCoO2 needed while still achieving high discharge capacity through the LiCoO2 core
3Quantity of substance
If LiNiO2 is used, then discharge capacity characteristics are improved, but synthesis difficulty and stability problems increase
Solution Approach 1:
The patent replaces the difficult-to-synthesize LiNiO2 with LiCoO2 as the core material, which has more established and easier synthesis routes. The LiCoO2 core provides comparable high discharge capacity while being more stable and easier to manufacture with controlled oxidation states
Solution Approach 2:
The patent creates a composite structure where the LiCoO2 core provides stable, easy-to-synthesize high-capacity performance, while the LiMn2O4 shell enhances overall stability and provides a more manageable synthesis process with lower oxidation state requirements
4Reliability
If coating particle volume is increased to improve stability, then electrical conductivity may decrease
Solution Approach 1:
The patent applies local quality by creating a thin outer shell structure where LiMn2O4 forms a coating layer with controlled thickness (5-50 nm) on the LiCoO2 core. This localized coating provides stability and structural support at the surface while minimizing the volume fraction of the coating material, thereby preserving the high electrical conductivity of the LiCoO2 core
Solution Approach 2:
The patent optimizes the coating particle volume fraction and shell thickness as critical parameters, maintaining the coating volume at 5-50 nm to achieve the optimal balance where sufficient stability is provided by the coating while electrical conductivity is preserved by limiting the coating's volume fraction and maintaining intimate contact between core particles
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 results in a positive active material with improved stability, high capacity, and enhanced electrical conductivity, leading to increased cycle life and thermal stability of lithium batteries without a significant decrease in initial capacity.
Implementation Method 1
heat-treated at a controlled temperature to optimize performance
Data Source
AI summary
A positive active material for a rechargeable lithium battery includes a positive active material compound including a metal compound for intercalating and deintercalating lithium, a coating particle having an embedded portion embedded into the active material compound and a protruding portion protruding from the surface of the active material, and a rechargeable lithium battery including the positive active material.