Silicon-Carbon Anode Layer With Glutamic Acid Binder for Expansion Control
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Solution Overview
Problem
Lithium-ion secondary batteries face challenges in charge and discharge capacity, cycle performance, reliability, safety, and cost, particularly due to issues with silicon-based negative electrodes experiencing particle expansion and contraction during charging and discharging.
Innovation Solution
A negative electrode active material layer is formed using a mixture of carbon particles and silicon-based materials, with a binder containing glutamic acid, which helps in improving the charge and discharge capacity and cycle performance while maintaining safety and reducing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based material is used as negative electrode active material to increase capacity, then charge and discharge capacity is improved, but particle expansion and contraction occurs during charging and discharging leading to poor cycle performance
Solution Approach 1:
The patent uses a composite material system consisting of silicon-based particles (5-50 nm), carbon particles (5-50 μm), and conductive carbon material (1-10 μm) to create a negative electrode that combines the high capacity of silicon with the structural stability and conductivity of carbon. This composite structure prevents particle expansion and contraction while maintaining high charge and discharge capacity.
Solution Approach 2:
The patent applies different materials to different regions of the negative electrode structure: silicon-based particles (5-50 nm) are distributed throughout to provide high capacity, carbon particles (5-50 μm) form a matrix structure to prevent expansion/contraction, and conductive carbon material (1-10 μm) is added to ensure electrical conductivity. This local differentiation of material functions resolves the contradiction between capacity and cycle performance.
2Quantity of substance
If carbon particles and silicon particles are mixed and used as negative electrode active material, then charge and discharge capacity is improved, but manufacturing process complexity increases
Solution Approach 1:
The patent combines multiple materials (silicon-based particles, carbon particles, and conductive carbon material) into a single mixed powder composition that can be directly used to form the negative electrode active material layer. This merging of materials into a unified mixture simplifies the manufacturing process by eliminating the need for separate application steps for each material.
Solution Approach 2:
The mixed powder composition serves multiple functions simultaneously: silicon-based particles provide high capacity, carbon particles prevent expansion/contraction, and conductive carbon material ensures electrical conductivity. This multi-functional powder mixture can be directly applied to the current collector, reducing manufacturing complexity while achieving multiple performance goals.
Data Source
AI summary
A negative electrode active material, a negative electrode active material layer, and a secondary battery including them, or a formation method thereof are provided. In one embodiment of the present invention, carbon particles and a silicon-based material are mixed and used as a negative electrode active material. A polymer including a polar substituent such as a carboxy group is used as a binder. Specifically, as the binder for the carbon particles and the silicon-based material, a polymer containing glutamic acid is used. As the silicon-based material, nanosilicon particles each having a particle diameter less than 1 μm is used.