Silicon Negative Electrode Coating for Battery Cycle Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Lithium-ion batteries face challenges with the cycle stability and rate performance of silicon-based negative electrodes due to the low conductivity of silicon and volume expansion, as well as the entanglement of carbon nanotubes with silicon particles, leading to inhomogeneous dispersion and increased electrolyte consumption.
Innovation Solution
A negative electrode is developed with a coating of a polymer layer containing carbon nanotubes on a silicon-containing substrate, which improves interface stability and ensures homogeneous dispersion of silicon particles in graphite, reducing volume change during charging and discharging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based particles are used in the negative electrode to increase capacity, then the battery capacity is improved, but the cycle stability deteriorates due to volume expansion and low conductivity
Solution Approach 1:
The patent uses composite materials by combining silicon-based particles with graphite particles and carbon nanotubes. The silicon-based particles provide high capacity while graphite and carbon nanotubes provide structural stability and conductivity, resolving the contradiction between capacity improvement and cycle stability maintenance.
Solution Approach 2:
The patent introduces polymer layers and carbon nanotubes as intermediary materials that coat the silicon-based particles. These intermediaries prevent direct contact between silicon and electrolyte, reduce volume expansion effects, and maintain electrical conductivity, thus improving cycle stability while preserving capacity benefits.
2Reliability
If carbon nanotubes are added to improve conductivity, then the electrical conductivity is improved, but the dispersion homogeneity deteriorates due to entanglement with silicon particles
Solution Approach 1:
The patent uses polymer layers as intermediary materials between carbon nanotubes and silicon particles. These polymer coatings prevent direct entanglement and aggregation, enabling homogeneous dispersion while maintaining the electrical conductivity benefits of carbon nanotubes.
Solution Approach 2:
The patent applies local quality by coating carbon nanotubes and polymers specifically on the surface of silicon-based particles rather than uniform mixing. This localized application ensures carbon nanotubes remain dispersed and functional without causing aggregation, achieving both conductivity improvement and dispersion homogeneity.
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
The solution results in higher cycle performance, higher rate performance, and improved strain-resistant capability, along with lower direct-current resistance in lithium-ion batteries.
Implementation Method 1
ensures homogeneous dispersion of silicon particles in graphite
Implementation Method 2
The polymer layer includes a polymer and carbon nanotubes
Data Source
AI summary
A negative electrode includes a current collector and a coating located on the current collector. The coating includes silicon-based particles and graphite particles. The silicon-based particles include a silicon-containing substrate and a polymer layer. The polymer layer includes a polymer and carbon nanotubes. The polymer layer is located on at least a part of a surface of the silicon-containing substrate. A minimum value of film resistances at different positions on a surface of the coating is R1, a maximum value of the film resistances is R2, an R1/R2 ratio is M, and a percentage of a weight of the silicon-based particles in a total weight of the silicon-based particles and the graphite particles is N, where M≥0.5, and N is 2 wt %-80 wt %.