Silicon-Graphite Negative Electrode for Stable Conductive Paths
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Solution Overview
Problem
The challenge in creating a stable and efficient conductive path in negative electrodes for secondary batteries, particularly lithium-ion batteries, using a combination of carbonaceous and silicon-based materials, is exacerbated by differences in powder properties, conductivity, and swelling ratios, leading to reduced capacity utilization and electrode degradation.
Innovation Solution
A negative electrode composition is developed using a granulated product of artificial graphite and natural graphite, where part of the natural graphite is exfoliated to form an exfoliated portion, enhancing contact and forming a high-level, firm conductive path with the silicon-based material, along with the use of carbon black as a conductive material, to ensure stable charge/discharge cycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If carbonaceous materials and silicon-based materials are combined to improve capacity density, then the theoretical capacity increases, but the conductive path becomes unstable due to different swelling ratios and powder properties
Solution Approach 1:
The patent uses a composite structure where silicon-based material particles are embedded within cavities of carbonaceous material particles. This composite design allows the carbonaceous material to provide a stable conductive network while accommodating the silicon-based material's volume changes during charge/discharge cycles, thus maintaining conductive path stability despite the different swelling ratios of the two materials.
Solution Approach 2:
The carbonaceous material particles are designed with internal cavities that can accommodate silicon-based material particles. These porous structures allow the carbonaceous material to maintain its structural integrity while providing space for the silicon-based material to expand and contract, ensuring stable electrical contact throughout charge/discharge cycles.
2Stability of the object's composition
If artificial graphite is used as carbonaceous material to reduce swelling ratio, then swelling is reduced, but the material becomes hard and forms voids easily, isolating silicon-based material particles
Solution Approach 1:
The patent combines artificial graphite with natural graphite to create a composite carbonaceous material. The artificial graphite provides low swelling ratio and structural stability, while the natural graphite components provide softer characteristics that prevent void formation and maintain good contact with silicon-based material particles during charge/discharge cycles.
Solution Approach 2:
The carbonaceous material is designed with heterogeneous local properties: the artificial graphite portions provide structural stability and low swelling, while the natural graphite portions provide softer contact surfaces that adapt to silicon-based material volume changes. This local quality differentiation resolves the contradiction between low swelling and good particle contact.
3Ease of operation
If natural graphite is used to improve deformability, then particle contact is improved, but swelling ratio increases
Solution Approach 1:
The patent creates a composite carbonaceous material where natural graphite and artificial graphite are combined. The natural graphite provides the necessary deformability and softness for good particle contact, while the artificial graphite component limits the overall swelling ratio. The synergistic combination allows both properties to coexist.
4Reliability
If nanocarbon material is added as conductive material to ensure conductive path, then conductivity is improved, but homogeneous dispersion becomes difficult and cost increases
Solution Approach 1:
The patent extracts the conductive function from separate nanocarbon additives and integrates it into the carbonaceous material particles themselves. By forming silicon-based material particles within cavities of carbonaceous material, the conductive network is built into the structural framework, eliminating the need for separate conductive additives and their associated dispersion challenges.
Data Source
AI summary
Provided are a negative electrode for a secondary battery having improved life characteristics, a negative electrode slurry and a method for manufacturing a negative electrode. The negative electrode for a secondary battery includes at least a graphite-based material and a silicon-based material, as a negative electrode active material, and a conductive material, wherein the graphite-based material includes a granulated product of artificial graphite with natural graphite, at least a part of natural graphite in the granulated product is exfoliated partially to form an exfoliated portion, and the exfoliated portion is in contact with the silicon-based material or another granulated product of artificial graphite with natural graphite, or forms a composite with the silicon-based material.