Positive Electrode Coating to Limit Residual Lithium Without Washing
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Solution Overview
Problem
Conventional lithium secondary battery positive electrode active materials face issues with electrochemical characteristics and stability due to Li impurities on their surface, which are exacerbated by the washing process used to remove these impurities, leading to reduced capacity and lifespan.
Innovation Solution
A positive electrode active material is developed with a first compound enabling lithium intercalation/deintercalation, coated with a second compound that reduces residual Li impurities on its surface, and optionally includes a third compound in the coating layer to enhance stability and electrochemical performance without the need for a washing process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a washing process is used to remove Li impurities from the surface of the positive electrode active material, then the content of residual lithium is reduced, but damage is generated on the surface of the positive electrode active material leading to deterioration of electrochemical characteristics and stability
Solution Approach 1:
The harmful Li impurities (LiOH and Li2CO3) are selectively removed from the surface of the positive electrode active material through a washing process using dilute acid solution, separating the impurities from the valuable active material particles
Solution Approach 2:
The washing process is optimized to selectively remove Li impurities from the surface while preserving the integrity of the active material particles, achieving different treatment intensities for impurities versus the main material
2Quantity of substance
If the Ni content of the positive electrode active material is increased to improve capacity characteristics, then the discharge capacity is improved, but the content of Li impurities on the surface increases proportionally
Solution Approach 1:
The washing conditions are optimized based on the Ni content of the active material, adjusting the acid concentration and washing parameters to effectively remove the increased Li impurities that come with higher Ni content while maintaining particle integrity
3Reliability
If a washing process is applied to reduce residual lithium, then the electrochemical characteristics are improved, but the production process becomes more complex and time-consuming
Solution Approach 1:
The washing process parameters (acid concentration, temperature, time, agitation speed) are optimized to achieve effective Li impurity removal in a single step, minimizing process complexity while maintaining electrochemical performance
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
This approach effectively maintains electrochemical characteristics and stability by reducing surface Li impurities, improving capacity, lifetime, and rate characteristics of the lithium secondary battery.
Implementation Method 1
a coating layer which contains at least one type of lithium metal oxide and/or lithium metal phosphate is formed in the surface of the positive electrode active material without a washing process to reduce the amount of residual lithium present on the surface of the positive electrode active material
Data Source
AI summary
The present invention relates to a positive electrode active material having improved electrochemical characteristics and improved stability, and a lithium secondary battery using a positive electrode including the positive electrode active material, and more particularly, to a positive electrode active material which may prevent decreases in electrochemical characteristics and stability of the positive electrode active material, which are caused by Li impurities, in advance by controlling the content of the Li impurities remaining on the surface of the positive electrode active material without a washing process to reduce the amount of residual lithium present on the surface thereof, and a lithium secondary battery using a positive electrode containing the positive electrode active material.