Alloy-Graphite Composite Negative Electrode for Lithium-Ion Batteries
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Solution Overview
Problem
Alloy-based negative electrode active materials in lithium-ion batteries undergo significant volume change during charge and discharge, leading to electrode collapse and low utilization rates due to limited contact points with the electrolyte solution and graphite, resulting in decreased capacity and conductivity.
Innovation Solution
A composite particle configuration is developed, where an alloy-based negative electrode active material is encapsulated within graphite, with an electronic conductor and solid electrolyte film, enhancing Li-ion and electron conduction paths, and potentially including an amorphous carbon film for improved cycling performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If alloy-based negative electrode active material is used to achieve large specific capacity, then battery capacity is improved, but volume change during charge and discharge causes electrode collapse and low utilization rate
Solution Approach 1:
The alloy-based negative electrode active material particles are embedded within the graphite particle interior, forming a nested structure where the alloy material is contained inside the graphite matrix. This nesting approach allows the graphite to constrain the alloy material during volume changes while maintaining close contact for efficient Li-ion transfer, thereby improving utilization rate without sacrificing capacity.
Solution Approach 2:
The invention creates a composite particle consisting of graphite as the base material with alloy-based negative electrode active material dispersed and embedded within it. This composite structure combines the advantages of both materials: graphite provides structural stability and cushions volume changes, while the alloy material contributes high specific capacity, resolving the contradiction between capacity and reliability.
2Stability of the object's composition
If alloy-based negative electrode active material is enclosed within graphite to suppress volume change, then electrode stability is improved, but contact points with electrolyte solution are limited causing low utilization rate
Solution Approach 1:
The alloy-based negative electrode active material is distributed as discrete particles or regions within the graphite matrix, creating local contact points between the alloy material and electrolyte solution through the graphite's conductive network. This local distribution ensures that while the overall structure is stabilized by graphite, sufficient local interfaces remain for efficient Li-ion transfer, maintaining high utilization rate.
3Stability of the object's composition
If alloy-based negative electrode active material is enclosed within graphite to suppress volume change, then electrode stability is improved, but conduction paths are limited causing decreased capacity and conductivity
Solution Approach 1:
The graphite particle acts as an intermediary medium that facilitates Li-ion transfer between the electrolyte solution and the embedded alloy-based negative electrode active material. The graphite's high Li-ion conductivity compensates for the reduced direct contact between alloy material and electrolyte, ensuring that sufficient conduction paths are maintained for high capacity while the graphite matrix simultaneously suppresses volume changes.
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 increases the utilization rate of the alloy-based negative electrode active material by stabilizing electron and ion conduction paths, reducing volume change-induced failures, and enhancing battery capacity and cycling performance.
Implementation Method 1
The solid electrolyte film covers the first active material particle. At least part of the electronic conductor is embedded in the solid electrolyte film
Implementation Method 2
The electronic conductor is placed on a surface of the first active material particle. At least part of the electronic conductor is embedded in the solid electrolyte film
Implementation Method 3
An alloy-based negative electrode active material tends to undergo a great extent of volume change during charge and discharge
Implementation Method 4
Graphite is a widely used negative electrode active material. It is expected that the graphite can function as a cushioning material in the composite particles to suppress the volume change of the alloy-based negative electrode active material
Data Source
AI summary
The negative electrode active material includes a first composite particle. The first composite particle includes a first active material particle, a second active material particle, an electronic conductor, and a solid electrolyte film. The first active material particle includes an alloy-based negative electrode active material. The second active material particle includes graphite. The electronic conductor is placed on a surface of the first active material particle. The solid electrolyte film covers the first active material particle. At least part of the electronic conductor is embedded in the solid electrolyte film. The second active material particle supports the first active material particle, the solid electrolyte film, and the electronic conductor.