Layered Silicon-Graphite Negative Electrode for Battery Durability
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Solution Overview
Problem
There is a demand for improving the durability of batteries with SiO mixed in the active material layer of the negative electrode to enhance capacity.
Innovation Solution
The negative electrode comprises a current collector layer, a first active material layer with a first graphite and a first silicon simple substance or compound, and a second active material layer with a second graphite and a second silicon simple substance or compound, where the first graphite has a larger average particle diameter than the second graphite, and the second silicon compound is present in minimal amounts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If SiO is mixed in the active material layer to increase battery capacity, then the energy density improves, but the durability deteriorates due to repeated expansion and contraction
Solution Approach 1:
The negative electrode is divided into multiple active material layers with different compositions and functions. The first layer contains SiO for high capacity, while the second layer contains graphite with smaller particles for structural stability. This segmentation allows each layer to perform its specific function, resolving the contradiction between capacity and durability.
Solution Approach 2:
The patent uses composite material structure by combining different active materials (SiO and graphite) in separate layers. The SiO provides high capacity while the graphite provides structural stability during cycling. This composite approach allows the battery to achieve both high capacity and good durability simultaneously.
2Speed
If graphite particle size is reduced to improve rate capability, then rapid charging performance improves, but the mechanical strength decreases
Solution Approach 1:
Different regions of the negative electrode have different graphite particle sizes tailored to their specific functions. The second active material layer contains fine graphite particles (smaller average diameter) optimized for rapid lithium insertion/extraction, providing high rate capability. This local optimization of particle size resolves the contradiction between rate capability and mechanical strength.
Data Source
AI summary
The present disclosure relates to a negative electrode including a current collector layer, a first active material layer bonded to the current collector layer, and a second active material layer bonded to the first active material layer, and a battery including the negative electrode. In the negative electrode, the first active material layer includes a first graphite; and a first silicon simple substance or silicon compound of 1 wt % or more and 90 wt % or less with respect to the total weight of the first active material layer. Further, in the negative electrode, the second active material layer includes a second graphite having an average particle diameter smaller than that of the first graphite; and a second silicon simple substance or silicon compound having an average particle diameter of 0 wt % or more and less than 1 wt % with respect to the total weight of the second active material layer. Thus, the durability of the battery can be improved.