Silicon Negative Electrode with Porous Carbon Matrix
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Lithium-ion secondary batteries using silicon as a negative electrode active material face challenges with cycle life due to volume changes during lithium insertion and desorption, leading to active material pulverization and safety issues like internal short circuits and heat generation during overcharge.
Innovation Solution
A negative electrode structure with a silicon oxide phase dispersed in a carbonaceous material, where microcrystalline silicon is finely bound and uniformly distributed, alleviates volume expansion and ensures conductivity, while a specific binder distribution and current collector interface design facilitate separation and prevent overheating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon is used as a negative electrode active material to increase energy density, then the capacity per mass increases significantly, but volume expansion and pulverization occur during lithium insertion and desorption
Solution Approach 1:
The patent embeds microcrystalline silicon particles inside a porous carbonaceous material matrix, creating a nested structure where the silicon is contained within the carbon framework. This nesting approach allows the silicon to expand and contract during lithium insertion and desorption while being constrained by the carbon matrix, preventing pulverization and maintaining structural stability.
Solution Approach 2:
The patent creates a composite material consisting of silicon particles combined with a porous carbonaceous material. The composite structure combines the high lithium occlusion capacity of silicon with the structural stability and conductivity of carbon, resolving the contradiction between capacity and stability.
2Quantity of substance
If metal lithium is used as a negative electrode active material to achieve high energy density, then the energy density increases, but dendrite formation occurs causing safety problems
Solution Approach 1:
The patent uses microcrystalline silicon as a consumable active material that can be replaced or regenerated. The silicon particles are designed to undergo volume changes during cycling without permanent damage, effectively making them disposable in the sense that they can be replaced if degraded, while maintaining safety unlike metal lithium.
Solution Approach 2:
The porous carbonaceous material acts as an intermediary between the silicon particles and the electrolyte, mediating the lithium insertion and desorption processes. This intermediary structure prevents direct contact between metal lithium and the electrolyte, eliminating dendrite formation while still enabling high capacity through the silicon's lithium occlusion capability.
3Strength
If the binder concentration is increased to improve adhesion, then the binding strength increases, but the conductivity of the electrode mixture decreases
Solution Approach 1:
The patent applies local quality by concentrating the binder primarily at the interface between the electrode mixture and the current collector, rather than uniformly distributing it throughout the electrode. This localized binder placement provides strong adhesion where needed while maintaining conductivity in the bulk electrode material.
Solution Approach 2:
The patent optimizes the binder concentration parameter to a specific range (0.1-5 mass%) that balances adhesion and conductivity requirements. By precisely controlling this parameter, the patent achieves sufficient binding strength without excessive binder that would compromise conductivity.
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 enhances the cycle life and safety of lithium-ion batteries by stabilizing the silicon phase, preventing pulverization and reducing the risk of overheating during overcharge, thereby improving discharge characteristics and maintaining battery integrity.
Implementation Method 1
silicon makes a large change in volume which accompanies insertion and desorption of lithium in a charge and discharge cycle
Implementation Method 2
a specific binder distribution and current collector interface design facilitate separation
Data Source
AI summary
An electrode for battery has an electrode mixture containing a binder and an active material particle selected from at least one of a carbonaceous material, a metal particle and a metal oxide particle formed on a current collector. When cutting strength of an interface between the current collector and the electrode mixture is represented by “a” and cutting strength in a horizontal direction within the electrode mixture is represented by “b”, the “a” and “b” satisfy a relation of a/b<1.