Lithium Complex Oxide Surface Coating for Residual Lithium Reduction
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Solution Overview
Problem
Lithium-rich nickel systems in lithium secondary batteries face issues with residual lithium on the surface of positive active materials, leading to high temperature stability problems and capacity degradation due to unreacted lithium compounds, which are exacerbated by washing processes that damage the material.
Innovation Solution
A lithium complex oxide secondary particle structure is developed with distinct interplanar distances between surface and internal primary particles, achieved by coating elements like Co, Mg, Al, and Ti, and a controlled thermal treatment process to reduce residual lithium and enhance battery performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
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 patent applies preliminary action by coating the surface of the positive active material with a protective layer before the washing process. This protective coating prevents surface damage during washing while still allowing the removal of residual lithium, thus resolving the contradiction between reducing residual lithium and maintaining surface integrity
Solution Approach 2:
The patent introduces an intermediary substance (protective coating material) that mediates between the washing process and the positive active material surface. This intermediary layer enables effective lithium removal while protecting the underlying material from damage, addressing both concerns simultaneously
2Ease of manufacture
If LiOH is used as lithium compound for nickel rich system (Ni content ≥ 65%), then reactivity at low temperature is improved, but much residual lithium remains on the surface in the form of LiOH and Li2CO3
Solution Approach 1:
The patent extracts the harmful residual lithium compounds from the surface through a controlled washing process that selectively removes LiOH and Li2CO3 while preserving the underlying active material. This extraction approach maintains the manufacturing advantages of using LiOH while eliminating the detrimental effects of residual lithium
Solution Approach 2:
The patent changes the parameters of the washing process (such as pH, temperature, and washing solution composition) to optimize the removal of residual lithium while preventing surface damage. By carefully controlling these parameters, the process achieves effective lithium removal without compromising the material structure
3Quantity of substance
If unreacted LiOH and Li2CO3 remain on the surface, then gas and swelling effect are generated by reacting with electrolyte, but high temperature stability is seriously worsened
Solution Approach 1:
The patent applies preliminary anti-action by removing residual lithium compounds before they can react with the electrolyte to generate gas and swelling effects. By eliminating these harmful substances in advance, the patent prevents the subsequent degradation of high temperature stability that would otherwise occur
4Reliability
If unreacted LiOH remains on the surface, then gelation occurs due to high viscosity when mixing slurry, but manufacturing process is affected
Solution Approach 1:
The patent applies preliminary action by removing unreacted LiOH from the surface before the slurry mixing process. This preliminary removal prevents the high viscosity gelation that would otherwise occur during mixing, ensuring smooth manufacturing operations
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 improves battery capacity, resistance, and lifetime by maintaining a hexagonal structure with specific interplanar distances, reducing residual lithium, and ensuring uniform Co concentration grading, thereby enhancing the battery's thermal stability and efficiency.
Implementation Method 1
a lithium complex oxide secondary particle... configured to satisfy a relation that is d1 > d2 wherein d1 is an interplanar distance of a crystalline structure... and d2 is an interplanar distance of a crystalline structure... the lithium complex oxide secondary particle has a hexagonal structure
Data Source
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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.