Silicon Negative Electrode Composition for Volume-Stable Battery Cycling
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Solution Overview
Problem
The capacity of carbon-based negative electrode materials in secondary batteries is limited by their theoretical capacity, and silicon-based materials, despite their high theoretical specific capacity, suffer from large volume changes and instability during charge-discharge cycles, leading to poor cycle stability and limited use.
Innovation Solution
A negative electrode plate composition comprising 30%-70% silicon-based material, 15%-40% binder, and 15%-40% conductive agent forms a porous conductive network that wraps the silicon-based material, controlling volume expansion and improving electrical conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based material is used as negative electrode active material, then theoretical specific capacity is improved (4200 mAh/g), but volume change during charge-discharge cycle increases significantly
Solution Approach 1:
The patent applies a flexible binder system that can accommodate the volume expansion of silicon-based material during lithiation. The binder forms a matrix that flexibly surrounds silicon particles, allowing volume change while maintaining structural integrity and preventing particle detachment from the current collector.
Solution Approach 2:
The patent creates a composite negative electrode structure combining silicon-based material with conductive carbon materials and binder. This composite approach allows the silicon to provide high capacity while the carbon matrix and binder constrain volume expansion and maintain electrical conductivity throughout charge-discharge cycles.
2Quantity of substance
If silicon-based material is used as negative electrode active material, then theoretical specific capacity is improved (4200 mAh/g), but cycle stability deteriorates due to unstable solid electrolyte film
Solution Approach 1:
The patent introduces a binder as an intermediary between the silicon-based material and the electrolyte. This binder layer mediates the formation of a stable solid electrolyte interface (SEI) film, preventing direct contact between electrolyte and silicon surface, thereby reducing unstable SEI formation and improving cycle stability.
Solution Approach 2:
The patent optimizes the chemical composition and physical properties of the binder to control SEI formation. By adjusting binder molecular weight, functional groups, and crosslinking density, the patent creates conditions for forming a stable, protective SEI layer that maintains electrode integrity over multiple cycles.
3Quantity of substance
If silicon-based material is used as negative electrode active material, then theoretical specific capacity is improved (4200 mAh/g), but mechanical integrity is lost due to volume expansion
Solution Approach 1:
The patent employs a flexible binder matrix that acts as a protective shell around silicon particles. This flexible shell accommodates volume expansion during charging while maintaining mechanical connectivity, preventing particle pulverization and electrode disintegration.
Solution Approach 2:
The patent creates a composite structure where silicon-based material is embedded in a continuous matrix of binder and conductive carbon. This composite architecture distributes mechanical stress during volume change, maintaining overall electrode integrity and preventing catastrophic failure.
4Use of energy by moving object
If high content of silicon-based material is used in negative electrode active material layer, then energy density is improved, but electrical conductivity decreases
Solution Approach 1:
The patent creates a composite structure where conductive carbon materials form a continuous network matrix that surrounds and connects silicon-based particles. This carbon matrix provides percolation pathways for electron transport, maintaining electrical conductivity even at high silicon content, while silicon particles provide high capacity.
Solution Approach 2:
The patent creates local conductive zones around each silicon particle using conductive carbon and binder, ensuring that electrical conductivity is maintained at the particle level. This local quality approach ensures that even with high silicon content, each region of the electrode maintains sufficient conductivity for efficient electron transport.
Data Source
AI summary
Provided is a negative electrode plate, comprising: a negative electrode current collector and a first negative electrode active material layer. The first negative electrode active material layer is arranged on at least one surface of the negative electrode current collector, wherein, components of the first negative electrode active material layer comprise, by mass: 30%-70% of a silicon-based material, 15%-40% of a binder and 15%-40% of a conductive agent.