Si-Composite Negative Electrode Balancing Capacity and Cycle Life
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Solution Overview
Problem
Si-containing materials in non-aqueous electrolyte secondary batteries face challenges with deterioration of charge/discharge cycle characteristics, despite increasing capacity, and existing technologies do not adequately address this issue.
Innovation Solution
A non-aqueous electrolyte secondary battery design incorporating a negative electrode with a first Si-containing material having a silicate phase and silicon particles dispersed within, and a second Si-containing material with a carbon phase and silicon particles, where the initial charge/discharge efficiency difference between the positive and negative electrodes is maintained between 1% and 8%, selectively using the second material for discharge in regions of large potential increase to restrict deterioration of the first material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If Si-containing material is used as negative electrode active substance, then battery capacity is increased, but charge/discharge cycle characteristics deteriorate
Solution Approach 1:
The negative electrode active substance is segmented into two distinct Si-containing materials: a first Si-containing material and a second Si-containing material. Each material serves a specific function - the first material provides high capacity while the second material suppresses potential increase and restricts deterioration. This segmentation allows the battery to achieve both high capacity and good cycle characteristics by combining the advantages of different Si-containing materials.
Solution Approach 2:
Different regions of the negative electrode are assigned different materials with specific local qualities. The first Si-containing material is used in regions where high capacity is needed, while the second Si-containing material is used in regions where potential increase is large to restrict deterioration. This local quality assignment optimizes both capacity and cycle stability throughout the electrode structure.
2Quantity of substance
If only first Si-containing material is used, then battery capacity is maximized, but deterioration of charge/discharge cycle characteristics occurs
Solution Approach 1:
The second Si-containing material acts as an intermediary that mediates between the first Si-containing material and the electrolyte/solid electrolyte interface. It suppresses the potential increase that occurs during charging, thereby protecting the first Si-containing material from excessive stress and restriction of deterioration. This intermediary role extends the cycle life while maintaining the high capacity provided by the first material.
Solution Approach 2:
The negative electrode active substance is designed as a composite material system comprising both the first Si-containing material and the second Si-containing material. This composite structure combines the high capacity characteristics of silicon-based materials with the stability provided by the second material, achieving both high capacity and extended cycle life through synergistic interaction between the two components.
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 effectively suppresses the deterioration of charge/discharge cycle characteristics and maintains battery capacity, as evidenced by capacity retention rates, compared to batteries using only the first Si-containing material alone.
Implementation Method 1
Each Si-containing material is a material capable of electrochemically storing and releasing lithium ions
Implementation Method 2
a first Si-containing material including a silicate phase and silicon particles dispersed in the silicate phase, and a second Si-containing material including a carbon phase and silicon particles dispersed in the carbon phase
Data Source
AI summary
A nonaqueous electrolyte secondary battery according to one embodiment of the present disclosure is provided with a positive electrode, a negative electrode and a nonaqueous electrolyte, while being characterized in that: the negative electrode comprises a negative electrode active material that contains an Si-containing material; the Si-containing material contains a first Si-containing material which comprises a silicate phase and silicon particles that are dispersed in the silicate phase, and a second Si-containing material which comprises a carbon phase and silicon particles that are dispersed in the carbon phase; and the difference between the initial charge/discharge efficiency (Efc) of the positive electrode and the initial charge/discharge efficiency (Efa) of the negative electrode, namely (Efc−Efa) satisfies 1%<(Efc−Efa)<8%.