Tungsten-Doped Cathode Coating to Suppress Doping Loss During Washing
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Solution Overview
Problem
Lithium secondary batteries face limitations in life characteristics and stability due to the loss of doping compounds during the washing process, which affects the removal of residual lithium impurities and leads to reduced electrochemical performance and cycle characteristics.
Innovation Solution
A method involving the formation of tungsten-doped lithium transition metal oxide, followed by washing with a hydroxide-based compound to prevent the loss of doping tungsten and improve battery performance by forming a stable coating on the surface, thereby enhancing life characteristics and safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a washing process is used to remove residual lithium impurities, then battery stability and safety are improved, but doping compounds are lost during washing
Solution Approach 1:
A coating layer comprising metal hydroxide or metal oxide is introduced as an intermediary substance between the positive electrode active material and the washing liquid. This coating layer acts as a protective barrier that prevents direct contact between the washing liquid and the doping compounds embedded in the positive electrode active material, thereby preventing doping compound loss while allowing the washing process to remove lithium impurities effectively
2Stability of the object's composition
If positive electrode active material is prepared at low temperature to suppress cation mixing, then cation mixing ratio is reduced, but residual lithium impurities increase
Solution Approach 1:
The synthesis process is segmented into two distinct stages: (1) low-temperature synthesis to suppress cation mixing and maintain compositional stability, and (2) subsequent washing process to remove residual lithium impurities. The coating layer is then applied to protect the synthesized material during washing, enabling separation of the conflicting requirements of low-temperature synthesis and thorough cleaning
3Quantity of substance
If nickel-rich system is used to achieve high capacity, then battery capacity increases, but cation mixing ratio increases at high temperature
Solution Approach 1:
The synthesis temperature parameter is changed and optimized to a lower range (700-900°C) specifically for nickel-rich positive electrode active materials. This parameter change suppresses cation mixing that would otherwise occur at higher temperatures, while the subsequent washing process with coating protection ensures thorough removal of lithium impurities, thereby maintaining both high capacity and compositional stability
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 method effectively suppresses the loss of doping compounds, improving the battery's life characteristics, safety, and electrochemical performance by stabilizing the tungsten doping and reducing lithium impurities, resulting in enhanced cycle and discharge capabilities.
Implementation Method 1
a hydroxide-based compound is added to the washing liquid during the washing
Implementation Method 2
forming a stable coating on the surface, thereby enhancing life characteristics and safety
Implementation Method 3
washing the lithium transition metal oxide with a washing liquid, wherein, in the washing, a hydroxide-based compound is added to the washing liquid during the washing
Data Source
AI summary
A method of preparing a positive electrode active material includes forming a tungsten-doped lithium transition metal oxide, and washing the lithium transition metal oxide, wherein, in the washing, a hydroxide-based compound is added to a washing liquid during the washing, a positive electrode including a positive electrode active material prepared according to the method, and a lithium secondary battery including the positive electrode.