Positive Electrode Layer With LixMnO2 for LiMn2O4 Capacity Fade
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Solution Overview
Problem
Conventional lithium-ion batteries using LiMn2O4 as a positive active material suffer from loss of specific discharge capacity due to the formation and repair of the SEI film, leading to rapid fading of cycle capacity.
Innovation Solution
Incorporating LixMnO2 material in the positive active material layer, which provides active lithium for SEI film formation and repair, and suppresses excessive deintercalation of lithium ions in spinel-type lithium manganese oxide, thereby enhancing cycle performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If LiMn2O4 is used as a positive active material, then the battery has low cost and high first-cycle Coulombic efficiency, but the specific discharge capacity fades rapidly due to SEI film formation and manganese ion dissolution
Solution Approach 1:
The patent introduces a lithium-rich material (Li4Ti5O12 or LiCoO3) as a preliminary lithium source that releases lithium ions during initial cycles. This preliminary action ensures sufficient lithium is available for SEI film formation, preventing subsequent lithium depletion that would otherwise cause capacity fading in LiMn2O4-based batteries
Solution Approach 2:
The lithium-rich material acts as an intermediary component between the lithium ion battery system and the SEI film formation process. It provides a controlled lithium release mechanism that mediates the interaction between active lithium and the electrolyte, ensuring proper SEI formation without excessive lithium consumption from the LiMn2O4
2Stability of the object's composition
If LiMn2O4 is used as a positive active material, then the battery has low cost, but the structural stability deteriorates due to manganese ion dissolution during cycling
Solution Approach 1:
The patent converts the harmful effect of manganese ion dissolution into a beneficial process by using the released manganese ions to form a protective coating on the LiMn2O4 surface. This coating, formed through controlled dissolution and reprecipitation, actually protects the bulk material from further degradation 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
The presence of LixMnO2 material improves the structural stability of spinel-type lithium manganese oxide, reduces manganese ion dissolution, and enhances the cycle performance and safety of lithium-ion batteries.
Implementation Method 1
The existence of the LixMnO2 material in the positive active material layer can provide active lithium for the formation and repair of the SEI film
Implementation Method 2
suppress the excessive deintercalation of lithium ions in the spinel-type lithium manganese oxide, thereby suppressing the decline in the structural stability of the spinel-type lithium manganese oxide
Implementation Method 3
suppressing the decline in the structural stability of the spinel-type lithium manganese oxide and the excessive dissolution of manganese ions
Data Source
AI summary
An electrochemical device, including a positive electrode plate. The positive electrode plate includes a positive active material layer. When the electrochemical device is in a fully discharged state, an X-ray diffraction pattern of the positive active material layer exhibits a first diffraction peak and a second diffraction peak in a range of 17.8° to 19.2°. A diffraction angle of the first diffraction peak is smaller than a diffraction angle of the second diffraction peak. The electrochemical device achieves an increased energy density and improved cycle performance.