Silicon Core Hard Carbon Coating Negative Electrode
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Solution Overview
Problem
Lithium-based batteries face issues with mechanical degradation and poor cycling performance due to large volume changes in silicon-based negative electrode active materials, leading to capacity fade and reduced lifespan, while lithium-sulfur batteries are limited by polysulfide shuttle effects and transition metal cations migration.
Innovation Solution
A negative electrode material is developed with a silicon core coated in hard carbon and paired with a non-fluorinated binder, which enhances mechanical stability, prevents electrolyte interaction, and mitigates polysulfide and cation migration, allowing for higher silicon loading and improved battery efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based negative electrode active material is used to increase capacity, then battery energy density is improved, but mechanical degradation occurs due to large volume changes during charging/discharging
Solution Approach 1:
The patent encapsulates silicon-based active material particles within a porous carbon matrix, creating a nested structure where the silicon particles are contained within the carbon framework. This nested configuration allows the silicon to undergo volume expansion and contraction during lithium insertion/extraction while the porous carbon matrix provides structural support and prevents mechanical degradation, thereby maintaining cycling performance while utilizing high-capacity silicon material.
Solution Approach 2:
The patent employs a porous carbon matrix that acts as a flexible shell surrounding the silicon particles. This carbon shell is designed with appropriate porosity and mechanical properties to accommodate the large volume changes of silicon during charging and discharging cycles. The flexible carbon shell prevents direct mechanical stress on the silicon particles, reducing fragmentation and maintaining electrode integrity over extended cycling.
2Quantity of substance
If higher silicon loading is applied to increase capacity, then energy density is improved, but mechanical degradation and capacity fade increase
Solution Approach 1:
The patent creates a localized porous carbon matrix structure that surrounds and supports each silicon particle individually. This local quality approach ensures that each silicon particle has its own dedicated carbon shell with appropriate mechanical and porosity properties, allowing high silicon loading throughout the electrode while maintaining local mechanical stability at each particle-matrix interface to prevent aggregation and degradation.
3Quantity of substance
If silicon-based material is used to increase capacity, then battery performance is improved, but electrolyte interaction causes parasitic reactions and capacity loss
Solution Approach 1:
The patent introduces a porous carbon matrix as an intermediary layer between the silicon-based active material and the electrolyte. This carbon matrix serves as a protective mediator that allows lithium ion transport while preventing direct contact between the electrolyte and silicon particles. By acting as an intermediary, the carbon shell eliminates parasitic reactions between the electrolyte and silicon, reducing capacity loss and improving battery performance.
Data Source
AI summary
A negative electrode material includes an active material. The active material includes a silicon core selected from the group consisting of Si, SiO2, SiOx (0<x<2), a silicon alloy, and a combination thereof. The active material also includes a hard carbon coating formed on the silicon core. The negative electrode material further includes a non-fluorinated binder. The negative electrode material also includes a conductive filler. The loading of the active material in the negative electrode material is greater than 2 mg/cm2.