Si-Graphite Anode Composition for Stable Battery Cycling
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Solution Overview
Problem
Secondary batteries with high Si content face issues of increased resistance leading to decreased input-output characteristics and capacity due to expansion and shrinkage during charging and discharging, which can result in disconnection of the conduction path and reduced cycle characteristics.
Innovation Solution
Incorporating graphite particles and Si-containing particles doped with elements from Group 15 and Group 16 into the negative electrode active material layer, with a specific weight ratio of 9:1 to 4:6, to suppress expansion and shrinkage, thereby improving input-output characteristics and cycle performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If high Si content is used as negative electrode active material, then battery capacity increases, but resistance increases and input-output characteristic decreases
Solution Approach 1:
The patent uses a composite material consisting of Si-containing particles (with Si content of 20-80 wt%) and graphite particles (98-20 wt%) as the negative electrode active material. This composite structure combines the high capacity advantage of Si with the stability and conductivity of graphite, resolving the contradiction between increasing capacity and maintaining input-output characteristic.
2Quantity of substance
If high Si content is used as negative electrode active material, then battery capacity increases, but expansion and shrinkage increase causing conduction path disconnection
Solution Approach 1:
The composite of Si-containing particles and graphite particles creates a stable structural framework. Graphite has excellent structural stability and maintains the conduction path during expansion and shrinkage, while Si provides high capacity. This resolves the contradiction between capacity and conduction path stability.
Solution Approach 2:
The patent optimizes the Si content within 20-80 wt% and graphite content within 98-20 wt% to achieve a balance between capacity and structural stability. By controlling these compositional parameters, the expansion and shrinkage are managed while maintaining conduction path integrity.
3Quantity of substance
If Si-based material is used as negative electrode active material, then battery capacity increases, but cycle characteristic decreases due to side reaction increase
Solution Approach 1:
The graphite component in the composite material provides structural stability and reduces side reactions during cycling. It forms a protective matrix around Si particles, preventing excessive side reactions while maintaining high capacity from Si, thus improving cycle characteristic.
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 combination of graphite and Si-containing particles with doped elements enhances conductivity and reduces path disconnection, achieving improved input-output and cycle characteristics in secondary batteries.
Implementation Method 1
Si of the Si-containing particle is doped with an element M. The element M is at least one kind of element among elements belonging to Group 15 and Group 16 in the periodic table.
Implementation Method 2
The negative electrode active material layer includes graphite particles and Si-containing particles as a negative electrode active material
Data Source
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AI summary
A secondary battery (100) disclosed herein includes an electrode body (20) including a positive electrode (50) and a negative electrode (60). The negative electrode (60) includes a negative electrode active material layer (64). The negative electrode active material layer (64) includes graphite particles (66) and Si-containing particles (68). The Si-containing particle (68) is a complex of Si and C, and Si is doped with an element M. The element M is at least one kind of element among elements belonging to Group 15 and Group 16 in the periodic table. The doping amount of the element M in the Si-containing particle (68) is 0.1 at% or more and 5 at% or less. The weight ratio between the graphite particles (66) and the Si-containing particles (68) is 9:1 to 4:6.