Lithium Silicate-Silicon Anode Composite for Crack-Suppressed Cycling
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Solution Overview
Problem
The use of silicon-based negative electrode active materials in non-aqueous electrolyte secondary batteries is hindered by significant irreversible capacity and poor cycle characteristics due to cracking of the lithium silicate phase during lithium absorption and release, leading to deteriorated cycle performance.
Innovation Solution
Incorporating a composite particle structure with a lithium silicate phase, a silicon phase dispersed within, and a crystalline silicon dioxide phase containing β-cristobalite and quartz, which enhances the flexibility and rigidity of the silicate phase, allowing it to better accommodate the expansion and contraction of the silicon phase, thereby reducing cracking and maintaining lithium-ion conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon particles are used as negative electrode active material to achieve high theoretical capacity density, then battery energy density is improved, but irreversible capacity increases and initial charge-discharge efficiency deteriorates
Solution Approach 1:
A lithium silicate phase is introduced as an intermediary matrix to hold silicon particles. This mediator allows the silicon to provide high capacity while the lithium silicate phase manages the irreversible capacity loss, enabling both high energy density and acceptable initial efficiency
Solution Approach 2:
Composite particles comprising silicon particles dispersed in a lithium silicate phase are used. This composite structure combines the high capacity of silicon with the stabilizing properties of lithium silicate, achieving both high energy density and improved charge-discharge efficiency
2Quantity of substance
If silicon phase expands and contracts during charge and discharge to enable lithium absorption and release, then reversible capacity is improved, but stress is generated in the silicate phase causing cracking and cycle characteristics deteriorate
Solution Approach 1:
The crystalline phase composition of silicon dioxide is specifically controlled to contain both β-cristobalite and quartz. This parameter change in the material structure provides a balance between flexibility and rigidity, allowing the silicate phase to accommodate silicon expansion/contraction while maintaining structural integrity
Solution Approach 2:
The silicate phase is designed as a composite containing lithium silicate, silicon particles, and crystalline silicon dioxide with specific phases. This composite structure provides both the flexibility needed to accommodate volume changes and the rigidity to prevent cracking during cycling
3Strength
If element Q is introduced in the lithium silicate phase to provide hardness, then structural strength is improved, but suppression of cracking in the silicate phase remains insufficient
Solution Approach 1:
The crystalline phase composition of silicon dioxide is specifically controlled to contain both β-cristobalite and quartz in the lithium silicate phase. This parameter change provides an optimal balance between hardness and flexibility, enabling the phase to resist cracking while accommodating silicon expansion and contraction
Solution Approach 2:
Different regions of the silicate phase have different properties: the lithium silicate matrix provides flexibility to accommodate volume changes, while the crystalline silicon dioxide phases (β-cristobalite and quartz) provide localized hardness and structural support to prevent cracking
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 significantly improves the cycle characteristics and capacity of the battery by suppressing cracking in the silicate phase, ensuring effective lithium-ion conductivity and maintaining high capacity throughout charge-discharge cycles.
Implementation Method 1
a material containing silicon (Si) that forms an alloy with lithium has been expected to be utilized as a negative electrode active material
Implementation Method 2
a crystalline phase of silicon dioxide dispersed in the lithium silicate phase, wherein the crystalline phase of silicon dioxide contains β-cristobalite and quartz
Data Source
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AI summary
A negative electrode active material for a non-aqueous electrolyte secondary battery includes composite particles containing a lithium silicate phase, a silicon phase dispersed in the lithium silicate phase, and a crystalline phase of silicon dioxide dispersed in the lithium silicate phase. The crystalline phase of silicon dioxide contains β-cristobalite and quartz.