Silicon Composite Anode Coating for Volume-Stable Battery Capacity
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Solution Overview
Problem
Silicon-based negative electrode materials for rechargeable batteries face issues such as capacity deterioration due to crushing and poor contact with conductivity aids, volume expansion, and irreversible capacity formation during initial charging reactions.
Innovation Solution
A silicon composite material coated with a self-assembled monolayer containing amino groups and bonded to a carbon compound via amide bonds, using a carbon nanotube as the carbon compound, enhances the stability and conductivity of the electrode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon is used as a negative electrode material to increase specific capacity, then the specific capacity increases, but volume expansion occurs during lithium ion occlusion
Solution Approach 1:
The silicon compound particles are embedded within a carbon material matrix, creating a nested structure where the carbon material accommodates the silicon compound. This nesting approach allows the carbon material to constrain the volume expansion of silicon during lithium ion occlusion while maintaining the high specific capacity of silicon.
Solution Approach 2:
The invention uses a composite material consisting of a silicon compound and a carbon material. The carbon material serves as a stable framework that prevents excessive volume expansion of silicon, while the silicon compound provides high specific capacity. This composite structure resolves the contradiction between high capacity and volume stability.
2Quantity of substance
If silicon is used as a negative electrode material, then the specific capacity increases, but capacity deterioration occurs due to crushing of active material particles
Solution Approach 1:
The carbon material composite provides a robust framework that prevents crushing of silicon compound particles during charging and discharging cycles. This protective composite structure maintains particle integrity and prevents capacity deterioration while preserving the high specific capacity of silicon.
Solution Approach 2:
The carbon material acts as a protective cushion surrounding the silicon compound particles before any damage can occur. This pre-established protective structure prevents crushing during subsequent battery cycling, thereby preventing capacity deterioration.
3Reliability
If a coating is formed during initial charging reaction, then the coating prevents further reactions, but the amount of lithium ions in the positive electrode decreases and capacity deteriorates
Solution Approach 1:
The amino group-functionalized carbon material provides localized functional groups at the interface between the carbon matrix and electrolyte. These localized amino groups facilitate lithium ion insertion and extraction reactions, enabling controlled coating formation that does not consume excessive lithium ions from the positive electrode.
4Device complexity
If conventional carbon materials are used, then the structure is simple, but poor contact with conductivity aids occurs and capacity deteriorates
Solution Approach 1:
The invention modifies the chemical parameters of the carbon material by introducing amino groups through functionalization. This parameter change enhances the chemical reactivity and bonding capability of the carbon material with conductivity aids, improving contact quality and preventing capacity deterioration while maintaining structural simplicity.
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 specific capacity, prevents coating formation during charging, minimizes capacity deterioration, and maintains high discharging capacity over multiple cycles by stabilizing the silicon composite.
Implementation Method 1
a process of mixing the carbon compound and the silicon composite in a liquid and bonding the carboxylic groups and the amino groups
Implementation Method 2
a self-assembled monolayer which covers the surface of the silicon composite and has amino groups
Implementation Method 3
bonding the carboxylic groups and the amino groups
Data Source
AI summary
A negative electrode active material for a rechargeable battery of the present invention includes a silicon composite composed of a silicon compound and at least one carbon material of graphite, non-graphitizable carbon, and soft carbon, a self-assembled monolayer which covers the surface of the silicon composite and has amino groups, and a carbon compound that is bonded to the self-assembled monolayer via the amino groups and contains carbon atoms as a main component.