Sulfur-Cyclic Electrolyte for Silicon-Carbon Anode Cycle Stability
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Solution Overview
Problem
Silicon-containing materials in non-aqueous electrolyte secondary batteries undergo significant volume changes during lithium ion absorption and desorption, leading to capacity retention rate and cycle characteristic degradation due to surface reactions with the electrolyte.
Innovation Solution
Incorporating carbon composite particles with a silicon phase dispersed in a carbon phase in the negative electrode, combined with a non-aqueous electrolyte containing a 5- or 6-membered cyclic compound component with a sulfur element, which forms a protective coating on the surface to suppress side reactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If carbon composite particles with silicon phase dispersed in carbon phase are used as negative electrode active material, then discharge capacity and active material utilization rate are improved, but volume change during charge and discharge increases causing particle breakage and capacity retention rate decreases
Solution Approach 1:
The patent embeds silicon phase particles inside carbon composite particles, creating a nested structure where the silicon is protected by the carbon matrix. This nested configuration allows the silicon to undergo volume expansion and contraction during lithium ion absorption and desorption without causing the entire particle to break apart, thereby maintaining capacity retention rate while utilizing the high capacity of silicon.
Solution Approach 2:
The carbon phase surrounding the silicon phase acts as a flexible shell that can accommodate the volume changes of the silicon during charge and discharge cycles. This carbon shell prevents direct contact between the silicon surface and electrolyte solution, reducing side reactions and preventing particle breakage, thus improving capacity retention while maintaining high discharge capacity.
2Productivity
If silicon-containing material is used to increase discharge capacity, then active material utilization rate is improved, but new surfaces are formed during particle breakage increasing side reactions with electrolyte solution
Solution Approach 1:
The carbon phase serves as an intermediary layer between the silicon phase and the electrolyte solution. This intermediate carbon shell prevents direct interaction between the silicon surface and electrolyte, thereby suppressing side reactions that would otherwise occur on newly exposed silicon surfaces after particle breakage, while still allowing lithium ion transport to the silicon for high active material utilization.
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 configuration maintains high initial discharge capacity and improves cycle characteristics by reducing the negative impact of volume changes on the battery's performance.
Implementation Method 1
the non-aqueous electrolyte contains a 5- or 6-membered cyclic compound component that contains a sulfur element as a ring-constituting element
Implementation Method 2
a material capable of electrochemically absorbing and desorbing lithium ions is used
Data Source
AI summary
Disclosed is a non-aqueous electrolyte secondary battery including: a negative electrode that contains a negative electrode material mixture; a separator, a positive electrode that is provided to oppose the negative electrode via the separator, and a non-aqueous electrolyte. The negative electrode material mixture contains a negative electrode active material. The negative electrode active material contains 3 mass % or more of a silicon-containing material. The silicon-containing material contains carbon composite particles. The carbon composite particles have a carbon phase and a silicon phase dispersed in the carbon phase. The non-aqueous electrolyte contains a 5- or 6-membered cyclic compound component that contains a sulfur element as a ring-constituting element.