Lithium Secondary Battery Discharge Control for Silicon Anodes
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Solution Overview
Problem
Existing lithium secondary batteries using silicon-based negative electrode active materials face issues with rapid volume expansion during charging, leading to disconnection of conductive paths and reduced cycle life, especially when using a full profile of the negative electrode.
Innovation Solution
Control the depth of discharge of the negative electrode to be between 0 V and 1.5 V (vs Li/Li+) and maintain a residual negative electrode capacity of 2.5% or greater, with a cut-off potential lower than the discharge potential, avoiding the full profile of the negative electrode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based compound is used as negative electrode active material to increase capacity, then discharge capacity is improved, but volume expansion occurs during charging leading to conductive path disconnection and capacity deterioration
Solution Approach 1:
A thin film coating layer is applied on the surface of silicon-based particles to suppress volume expansion and prevent conductive path disconnection during charging-discharging cycles, thereby maintaining reliability while preserving high discharge capacity
Solution Approach 2:
Silicon-based compounds are combined with other materials (such as carbon materials or oxides) to form composite structures that suppress volume expansion and maintain conductive paths, enabling both high capacity and reliability
2Productivity
If full profile of negative electrode is used to ensure no residual negative electrode remains, then capacity utilization is improved, but life performance deteriorates due to volume expansion
Solution Approach 1:
Instead of using the full profile of the negative electrode, a controlled partial utilization approach is adopted by setting specific discharge potential ranges (e.g., 0.01 V to 1.5 V vs. Li/Li+), which prevents excessive volume expansion while maintaining sufficient capacity utilization
Solution Approach 2:
The discharge potential parameters are optimized and controlled within specific ranges to balance capacity utilization and cycle life, preventing the harmful effects of full profile usage while maximizing battery performance
3Quantity of substance
If silicon-based compound with high capacity is used, then initial capacity is improved, but surface degradation accelerates during repeated charging and discharging cycles
Solution Approach 1:
A protective thin film coating is applied on silicon-based particles to suppress surface degradation during repeated charging-discharging cycles, maintaining both high initial capacity and long-term surface stability
Solution Approach 2:
The thin film coating acts as a protective barrier that cushions the silicon-based particles against mechanical stress and chemical degradation before surface damage can occur, preserving surface integrity throughout the battery lifecycle
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 improves the life characteristics of the lithium secondary battery by maintaining a residual negative electrode capacity within a specific range, enhancing the battery's performance and cycle life without using the full profile of the negative electrode.
Implementation Method 1
The negative electrode includes a negative electrode active material for intercalating and deintercalating lithium ions coming out from the positive electrode
Data Source
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AI summary
The present application relates to a lithium secondary battery.