LCO Cathode Powder Composition for Capacity Fade and Discharge Balance
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Solution Overview
Problem
Existing lithium cobalt-based oxide (LCO) cathode active materials for lithium-ion secondary batteries suffer from low discharge capacity and high capacity fading rates, particularly when the content of the LiNaSO4 secondary phase is outside the optimal range.
Innovation Solution
A lithium cobalt-based oxide cathode active material powder with a specific S/Na atomic ratio of 0.80 to 1.20 and a LiNaSO4 content of 0.4 to 1.1 wt% is developed, along with a manufacturing process involving sintering and milling, to enhance discharge capacity and reduce capacity fading.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the content of LiNaSO4 secondary phase is increased to improve capacity fading rate, then cycle life is improved, but first discharge capacity decreases when content exceeds optimal range
Solution Approach 1:
The patent optimizes the content of LiNaSO4 secondary phase within a specific range (0.5-5 wt%) to achieve the best balance between cycle life and first discharge capacity. This parameter optimization resolves the contradiction by identifying the optimal concentration that simultaneously improves reliability while maintaining adequate capacity.
Solution Approach 2:
The patent creates a composite cathode active material consisting of primary phase (LiCoO2 with transition metals) and secondary phase (LiNaSO4). This composite structure allows the secondary phase to improve cycle life while the primary phase maintains high discharge capacity, resolving the contradiction through synergistic material design.
2Quantity of substance
If washing process is applied to remove LiNaSO4 to improve first discharge capacity, then capacity is increased, but cycle life deteriorates due to poor stability
Solution Approach 1:
The patent maintains the LiNaSO4 content within an optimized range (0.5-5 wt%) rather than removing it completely through washing. This parameter control approach preserves the beneficial stabilizing effect of LiNaSO4 on cycle life while avoiding excessive content that would harm discharge capacity.
Solution Approach 2:
The patent deliberately retains the composite structure with both primary and secondary phases, recognizing that the LiNaSO4 secondary phase provides structural stability that enhances cycle life, while the overall composite design maintains high discharge capacity.
3Reliability
If S/Na atomic ratio is optimized to form proper LiNaSO4 phase, then capacity fading rate is reduced, but manufacturing precision requirements increase
Solution Approach 1:
The patent specifies an optimal S/Na atomic ratio range (0.80-1.20) to ensure proper formation of LiNaSO4 secondary phase. This parameter specification balances the need for reliable capacity fading rate improvement with achievable manufacturing precision.
Data Source
AI summary
A lithium cobalt-based oxide cathode active material powder having: —a primary phase comprising Li, Co, and O, and—a secondary phase comprising LiNaSO4, wherein the content of said LiNaSO4 secondary phase in said powder is of at least 0.4 wt. % and inferior or equal to 1.1 wt. % with respect to a total weight of the cathode active material powder, said cathode active material powder being characterized in that it has a S/Na atomic ratio superior or equal to 0.80 and inferior or equal to 1.20.