Silicon Oxide Anode Composition for Volume-Stable Secondary Batteries
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Solution Overview
Problem
Silicon-based particles used in negative electrodes of secondary batteries suffer from low initial efficiency and reduced mechanical stability due to excessive volume changes during charge and discharge cycles, leading to degraded battery life.
Innovation Solution
A negative electrode comprising a mixture of SiO x particles with a D 50 of 0.1 µm to 0.6 µm and SiO y particles with a D 50 of 3 µm to 8 µm, in a specific weight ratio, combined with single-walled carbon nanotubes as a conductive agent, enhances electron movement and connectivity between particles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based particles are used as negative electrode active material, then discharge capacity is improved, but volume changes excessively during charge and discharge process
Solution Approach 1:
The patent embeds silicon-based particles inside hollow carbon spheres, creating a nested structure where the silicon is contained within the carbon shell. This nesting approach allows the silicon to undergo volume changes during charge-discharge cycles while the outer carbon shell maintains the overall structural integrity and prevents electrode disintegration.
Solution Approach 2:
The hollow carbon spheres act as flexible shells that can accommodate the volume expansion and contraction of the silicon-based particles during lithium insertion and extraction. The carbon shell provides a buffer that absorbs mechanical stress while maintaining electrode structure.
2Quantity of substance
If silicon-based particles are used as negative electrode active material, then discharge capacity is improved, but cracks occur and mechanical stability degrades
Solution Approach 1:
By nesting silicon particles within hollow carbon spheres, the patent prevents direct exposure of silicon to mechanical stress from electrode assembly and battery operation. The carbon shell protects the brittle silicon particles from cracking while maintaining electrical conductivity.
Solution Approach 2:
The patent creates a composite structure combining silicon-based particles with carbon material. The composite hollow carbon spheres integrate the high capacity of silicon with the mechanical strength and flexibility of carbon, achieving both high discharge capacity and improved mechanical stability.
3Strength
If carbon coating layer is formed on silicon-based particles, then surface protection is improved, but initial efficiency and lifetime are not significantly improved
Solution Approach 1:
Instead of a simple surface coating, the patent uses hollow carbon spheres that completely enclose the silicon particles, providing three-dimensional protection from all directions. This nested structure offers superior mechanical support and structural stability compared to conventional surface coatings.
Solution Approach 2:
The hollow carbon spheres function as flexible protective shells that can dynamically accommodate silicon volume changes during charge-discharge cycles. This flexible enclosure provides continuous structural support and prevents particle aggregation, significantly improving battery lifetime.
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
The solution increases the contact area between silicon-based particles, improving battery life characteristics by facilitating electron movement and maintaining connectivity despite volume changes, thus enhancing the battery's life and performance.
Implementation Method 1
since single-walled carbon nanotubes electrically and physically connect the silicon-based particles to each other, the life characteristics of the battery may be further improved
Data Source
AI summary
The present invention relates to a negative electrode, which includes a negative electrode active material layer comprising a negative electrode active material and a conductive agent, wherein the negative electrode active material includes a first active material and a second active material, wherein the first active material includes SiOx particles (0<x<2), and the second active material includes SiOy particles (0<y<2), wherein the SiOx particles have a D50 of 0.1 um to 0.6 um, the SiOy particles have a D50 of 3 um to 8 µm, a weight ratio of the SiOx particles to the SiOy particles is in a range of 1:2 to 1:100, and the conductive agent includes single-walled carbon nanotubes, and a secondary battery comprising the same.