Graphene-Wrapped Silicon-Graphite Negative Electrode Against Pulverization
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Solution Overview
Problem
Secondary batteries used in electric vehicles and portable terminals face challenges with capacity, stability, and durability due to volume changes in alloy-based materials during charging and discharging, leading to issues like pulverization and detachment of active materials, which affect cycle performance and energy density.
Innovation Solution
The use of a composite electrode structure featuring a sheet-like graphene compound that clings to active materials through hydrogen bonds, providing mechanical strength and preventing separation, combined with a mixture of silicon and graphite to enhance conductivity and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If alloy-based materials are used as active material to increase capacity, then charge and discharge capacity is improved, but pulverization and detachment of active material occur due to volume change
Solution Approach 1:
The active material is divided into particles with specific size ranges (first particles: 3 μm to 30 μm, second particles: 0.3 μm to 3 μm) to reduce volume expansion stress and prevent pulverization while maintaining high capacity
Solution Approach 2:
A composite structure is formed where silicon-based particles (high capacity) are combined with graphite particles (stable structure) in specific ratios, creating a material that achieves both high charge/discharge capacity and excellent cycle performance through complementary properties
2Quantity of substance
If proportion of active material in electrode is increased to increase capacity, then energy density is improved, but conductivity decreases and output characteristics worsen
Solution Approach 1:
Conductive agents are selectively placed in specific regions between active material particles rather than uniformly distributed, ensuring adequate conductivity in high-capacity electrode regions while minimizing the overall proportion of non-active materials
Solution Approach 2:
The electrode design optimizes the proportion of conductive agents and binders as adjustable parameters to achieve the balance point where capacity is maximized while maintaining sufficient conductivity for required output characteristics
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
This configuration results in a secondary battery with improved mechanical strength, high energy density, and stable cycle performance, reducing deterioration and increasing driving range for electric vehicles while enabling faster charging and smaller form factors for portable devices.
Implementation Method 1
a material having a sheet-like shape (a graphene compound) which clings to the active material by hydrogen bonds
Data Source
AI summary
A negative electrode with little deterioration is provided. A novel negative electrode is provided. A power storage device with little deterioration is provided. A novel power storage device is provided. The electrode contains silicon, graphite, and a graphene compound. A silicon particle with a particle diameter of less than or equal to 1 µm is attached to a graphite particle with a particle diameter 10 times or more that of the silicon particle. The graphene compound is in contact with the graphite particle so as to cover the silicon particle.