Carbon-Silicon Composite Negative Electrode for High-Capacity Batteries
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Solution Overview
Problem
Existing carbon-silicon composite materials for lithium ion batteries face challenges in achieving high Si content, long cycle life, and low irreversible capacity due to limitations in production methods and material properties, such as the need for catalysts and complications in producing high-capacity negative electrodes.
Innovation Solution
A carbon-silicon composite material is developed, comprising carbon black and silicon particles bound by a resin thermolysis product, with specific particle sizes and resin compositions, such as polyvinyl alcohol, to enhance conductivity and cycle characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If Si particle simple substance is added as negative electrode active material, then capacity is improved, but volume change (about 300%) occurs during lithium ion insertion/separation, causing particle disintegration and short cycle life
Solution Approach 1:
The silicon particles are embedded within a carbon matrix structure, where the carbon material acts as a protective shell or container that accommodates the silicon particles. This nested configuration allows the silicon to expand and contract during lithium insertion/extraction while being constrained by the carbon matrix, preventing particle disintegration and maintaining structural integrity over multiple cycles.
Solution Approach 2:
The invention creates a composite material system combining silicon particles with carbon matrix and resin thermolysis product. This composite structure leverages the high capacity of silicon while the carbon matrix provides structural stability and the resin thermolysis product enhances binding, achieving both high capacity and long cycle life simultaneously.
2Quantity of substance
If Si negative electrode is mechanically disrupted during alloying/dealloying process, then volume change occurs, but immediate and irreversible reduction in amount occurs, followed by lowering of coulombic efficiency
Solution Approach 1:
The carbon matrix and resin thermolysis product are introduced beforehand to cushion and absorb the mechanical stress generated during silicon alloying and dealloying processes. This protective layer prevents direct mechanical disruption of silicon particles, reducing irreversible capacity loss and maintaining coulombic efficiency.
3Quantity of substance
If high Si content is targeted, then capacity increases, but production complexity increases due to need for catalysts and complicated production methods
Solution Approach 1:
The invention extracts and eliminates the need for catalysts and complicated production processes by using a straightforward approach: mixing silicon particles with carbon matrix and resin thermolysis product, followed by simple thermal treatment. This simplifies the production method while achieving high silicon content composite materials.
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 composite material achieves a high Si content, long cycle life, and low irreversible capacity, making it suitable for high-capacity negative electrodes in lithium ion batteries.
Implementation Method 1
the carbon black and the silicon particle are bound via a resin thermolysis product
Implementation Method 2
with specific particle sizes and resin compositions, such as polyvinyl alcohol, to enhance conductivity
Data Source
AI summary
The present invention provides a carbon-silicon composite material suitable (e.g., high capacity; small irreversible capacity; long cycle life) to be used as a negative electrode material for battery. The carbon-silicon composite material comprises a carbon black and a silicon particle, wherein the carbon black and the silicon particle are bound via a resin thermolysis product.