Silicon-Graphite Composite Negative Electrode Material for Li-Ion Batteries
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The challenge is to enhance the charge-discharge cycle characteristics of lithium ion batteries by improving the dispersion of silicon ultrafine particles on graphite surfaces, as existing methods fail to fully disperse these particles, leading to aggregation and increased internal resistance.
Innovation Solution
A negative electrode material comprising silicon-containing particles with a SiOx layer, artificial graphite particles, and a carbonaceous material, where the silicon-containing particles have a specific oxygen content and primary particle diameter, and the artificial graphite particles have defined structural and morphological characteristics, forming composite particles to improve dispersion and cycle life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon ultrafine particles are used to increase theoretical capacity, then battery capacity is improved, but particle aggregation occurs leading to increased internal resistance
Solution Approach 1:
The patent uses graphite particles as an intermediary carrier to disperse silicon ultrafine particles. The graphite particles prevent direct aggregation of silicon particles by providing a separate support structure, while still allowing electrical contact and lithium ion transfer between silicon particles and the electrolyte.
Solution Approach 2:
The patent creates a composite material structure where silicon ultrafine particles are combined with graphite particles and binder resin. This composite structure leverages the high capacity of silicon while using graphite's stable structure to prevent aggregation, achieving both high capacity and low internal resistance.
2Quantity of substance
If silicon particles are used for high theoretical capacity, then battery capacity is improved, but expansion and contraction cause particle breakage and capacity loss
Solution Approach 1:
The patent applies binder resin beforehand to coat and bind silicon ultrafine particles together, forming a resilient network structure. This pre-established binding structure cushions the mechanical stress of expansion and contraction during cycling, preventing particle breakage and maintaining electrical contact over many cycles.
Solution Approach 2:
The binder resin forms a flexible matrix around silicon particles that can accommodate volume changes during lithium insertion and extraction. This flexible binding structure maintains particle integrity and electrical connectivity despite the mechanical stress of repeated expansion and contraction.
3Quantity of substance
If ultrafine particles are dispersed to improve capacity, then battery capacity is improved, but surface activity causes aggregation
Solution Approach 1:
The graphite particles serve as an intermediary that reduces the surface activity of silicon ultrafine particles. By providing a separate support structure, graphite prevents direct particle-particle interactions that lead to aggregation, while still enabling functional contact with the electrolyte.
Solution Approach 2:
The patent creates different local environments: silicon particles are dispersed on graphite surfaces rather than freely in the electrolyte. This localized placement on graphite carriers reduces the effective surface activity and prevents aggregation while maintaining the high surface area needed for capacity.
4Duration of action of stationary object
If graphite is used for excellent cycle characteristics, then cycle life is improved, but theoretical capacity is limited to 372 mAh/g
Solution Approach 1:
The patent merges graphite's excellent cycle characteristics with silicon's high theoretical capacity. By combining these two materials in a composite structure where silicon particles are dispersed on graphite, the system achieves both the stability of graphite and the high capacity of silicon.
Solution Approach 2:
The patent creates a composite material system combining graphite and silicon ultrafine particles. This composite leverages the complementary strengths of both materials: graphite provides structural stability and long cycle life, while silicon provides high theoretical capacity, achieving performance superior to either material alone.
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 a lithium ion battery with a large discharge capacity and excellent charge-discharge cycle characteristics, reducing expansion and contraction strain and enhancing electrode stability.
Implementation Method 1
intercalation and deintercalation (occlusion and release) of lithium ions
Implementation Method 2
graphite exhibits excellent cycle characteristics
Data Source
AI summary
A negative electrode material for a lithium ion battery, including silicon-containing particles, artificial graphite particles and a carbonaceous material, wherein at least part of the silicon-containing particles, the artificial graphite particles and the carbonaceous material form composite particles; wherein the silicon-containing particles are silicon particles having a SiOx (0<x≤2) layer on the particle surface, having an oxygen content of 1.0 mass % or more and 18.0 mass % or less, and mainly containing particles having a primary particle diameter of 200 nm or less; wherein the artificial graphite particles are non-flaky artificial graphite particles and have a 50% particle diameter in a volume-based cumulative particle size distribution, D50, of 1.0 μm or more and 15.0 μm or less. Also disclosed is a lithium-ion battery including a negative electrode using the negative electrode material.