Lithium-Rich Positive Electrode Coating for High-Voltage Stability
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Solution Overview
Problem
Lithium-rich manganese-based materials exhibit low initial charge-discharge efficiency, cycling performance, and rate performance due to the formation of oxygen vacancies, which leads to structural instability and poor electronic conductivity, especially under high voltage conditions.
Innovation Solution
A lithium-rich manganese-based positive electrode material is coated with a composite material of transition metal oxoacid salt and carbon, which includes oxygen vacancies, promoting structural stability and electronic conductivity, thereby enhancing energy density, charge-discharge efficiency, and cycling performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If high voltage charging (4.5V or more) is applied to lithium-rich manganese-based material, then high energy density is achieved, but oxygen vacancies form causing structural instability and reduced cycling performance
Solution Approach 1:
A coating layer comprising transition metal oxide and carbon is introduced as an intermediary between the lithium-rich manganese-based material and the electrolyte. This coating layer mediates the high voltage charging process, preventing direct harmful interactions that cause oxygen vacancy formation while allowing efficient charge transfer, thus enabling high energy density without compromising cycling performance
Solution Approach 2:
The surface properties of the material are modified by coating with transition metal oxide and carbon, changing the electrochemical parameters at the material surface. This parameter change stabilizes the material structure during high voltage charging, suppressing oxygen vacancy formation and improving cycling performance while maintaining high energy density
2Quantity of substance
If lithium ions are extracted from transition metal layer during high voltage charging, then high discharge capacity is achieved, but crystal vacancies form leading to lower initial charge-discharge efficiency
Solution Approach 1:
The transition metal oxide and carbon coating acts as an intermediary that facilitates reversible lithium ion extraction and insertion. The coating maintains structural integrity during lithium extraction, preventing crystal vacancy formation and ensuring high initial charge-discharge efficiency while achieving high discharge capacity
Solution Approach 2:
The coating layer is applied beforehand to cushion and protect the crystal structure during lithium ion extraction. This prior protection prevents structural degradation and crystal vacancy formation, maintaining high charge-discharge efficiency throughout the battery's operational life
3Adaptability or versatility
If transition metal ions migrate and crystal structure rearranges due to oxygen vacancies, then material adapts to high voltage, but structural stability deteriorates
Solution Approach 1:
The transition metal oxide and carbon coating serves as a stable intermediary layer that prevents transition metal ion migration and crystal structure rearrangement. The coating maintains structural stability while allowing the material to adapt to high voltage conditions, resolving the contradiction between adaptability and stability
4Reliability
If surface coating is applied to improve stability, then cycling performance is enhanced, but electronic conductivity may be reduced
Solution Approach 1:
A composite coating material consisting of transition metal oxide and carbon is used. The carbon component provides excellent electronic conductivity, while the transition metal oxide provides structural stability and protects against oxygen vacancy formation. This composite structure simultaneously improves cycling performance and maintains high electronic conductivity
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 coating with a composite material of transition metal oxoacid salt and carbon improves the material's energy density, initial charge-discharge efficiency, and rate performance by stabilizing the structure and enhancing electronic conductivity, while maintaining oxygen vacancies within a suitable range.
Implementation Method 1
coating the surface of the lithium-rich manganese-based material with an oxygen vacancy-rich material will not cause the structure of the surface layer of the material to be reconstructed or destroyed
Implementation Method 2
through the synergistic effect of carbon coating, not only the formation and protection of oxygen vacancies are promoted, but also the problem of low electronic conductivity of the material itself is alleviated
Implementation Method 3
coating the surface of the lithium-rich manganese-based material with an oxygen vacancy-rich material will not cause the structure of the surface layer of the material to be reconstructed or destroyed
Data Source
AI summary
A positive electrode material includes a core including a lithium-rich manganese-based positive electrode material, and a coating layer enveloping outer surface of the core and including a composite material of a transition metal oxoacid salt and carbon. The transition metal in the transition metal oxoacid salt is selected from at least one of Ti, Mo, W, V, Ta, Nb or Nd and the composite material has a mesh structure.