Lithium Complex Oxide Crystal Spacing for Low-Residual Cathodes
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Solution Overview
Problem
Lithium complex oxides for secondary batteries face issues with residual lithium, leading to high temperature stability problems and degradation of capacity and efficiency due to unreacted LiOH and Li2CO3 on the surface of positive active materials, which are exacerbated by the washing process used to remove residual lithium.
Innovation Solution
A lithium complex oxide secondary particle is formed through a process where primary particles on the surface have a Co-coated layer with varying Co concentration, creating different interplanar distances in the crystalline structure, reducing residual lithium and improving battery characteristics by controlling the thickness and distribution of the Co-coated layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a washing process is executed to remove unreacted Li from the surface of positive active material, then residual lithium is reduced, but the surface of the positive active material is damaged and characteristics of capacity and efficiency are degraded
Solution Approach 1:
The harmful unreacted Li is selectively removed through washing, while the beneficial LiCoO2 crystalline structure is preserved through controlled washing conditions and subsequent drying processes that prevent surface damage
Solution Approach 2:
The positive active material undergoes preliminary sintering and surface treatment before washing to strengthen the surface structure, making it more resistant to damage during the subsequent washing process while still allowing effective removal of residual lithium
2Ease of manufacture
If unreacted LiOH and Li2CO3 remain on the surface of positive active material, then manufacturing process is simplified, but high temperature stability is seriously worsened due to gas generation and swelling effect
Solution Approach 1:
The sintering temperature and time parameters are optimized to ensure complete reaction of LiOH and Li2CO3, transforming them into stable LiCoO2 structure. The washing process then removes any remaining unreacted lithium compounds, achieving both complete reaction and surface cleanliness
Solution Approach 2:
The washing process, which could potentially damage the surface, is converted into a beneficial step by controlling it to selectively remove harmful residual lithium compounds while preserving the beneficial LiCoO2 crystalline structure through optimized washing conditions
3Ease of manufacture
If unreacted LiOH remains on the surface, then manufacturing process is simpler, but gelation occurs due to high viscosity when mixing slurry before manufacturing electrode plates
Solution Approach 1:
Unreacted LiOH is extracted from the surface of the positive active material through the washing process, eliminating the source of gelation and ensuring smooth slurry mixing without viscosity-related operational difficulties
4Stability of the object's composition
If washing process is executed to reduce residual lithium, then high temperature stability is improved, but resistance increases in high temperature storage
Solution Approach 1:
The washing parameters (temperature, duration, solution composition) are precisely controlled to remove residual lithium that causes high temperature instability, while the drying and surface treatment parameters are optimized to prevent formation of surface structures that would increase resistance during high temperature storage
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 approach enhances the capacity, resistance, and battery lifetime by reducing residual lithium, improving the thermal stability and efficiency of lithium complex oxide secondary batteries, while maintaining the structural integrity of the active material.
Implementation Method 1
a primary particle locating on a surface part of the secondary particle includes a Co-coated layer at a part that is in contact with a surface of the secondary particle
Data Source
AI summary
Disclosed is a lithium complex oxide and method of manufacturing the same, more particularly, a lithium complex oxide effective in improving the characteristics of capacity, resistance, and lifetime with reduced residual lithium and with different interplanar distances of crystalline structure between a primary particle locating in a internal part of secondary particle and a primary particle locating on the surface part of the secondary particle, and a method of preparing the same.