Silicon Oxide Anode Material With Carbon Coating for Cycle Stability
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Solution Overview
Problem
Lithium-ion secondary batteries using silicon as a negative electrode material face challenges in maintaining high battery capacity, cycle characteristics, and initial efficiency due to the expansion and instability of silicon-based active materials, leading to electrolyte decomposition and reduced cycle life.
Innovation Solution
A negative electrode active material comprising a silicon compound particle (SiO x : 0.5 ≤ x ≤ 1.6) coated with a carbon material, containing Li 4 SiO 4, Li 2 SiO 3, and Li 2 Si 2 O 5, with a specific ratio of O-component to CH-component fragments detected by TOF-SIMS, and optimized for volume resistivity and crystallite size, enhancing electric conductivity and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silane-coated natural graphite is used as negative electrode active material, then capacity near theoretical limit can be achieved, but coarse intra-particle voids cause electrolyte infiltration and particle disintegration during charging-discharging cycles
Solution Approach 1:
The invention utilizes a porous coating layer formed by pyrolyzing a polysiloxane-based organic substance on the natural graphite particle surface. This porous structure fills the coarse intra-particle voids while maintaining electrolyte access, preventing particle disintegration during charging-discharging cycles and improving overall electrode reliability.
Solution Approach 2:
The invention creates a composite structure by coating natural graphite particles with a silane-based porous layer. The composite material combines the high capacity of natural graphite with the structural stability and electrolyte management benefits of the porous silane coating, achieving both high capacity and particle stability.
2Reliability
If fine porous coating layer is formed on natural graphite particles, then particle disintegration is prevented, but Li ion permeation may be hindered
Solution Approach 1:
The porous structure of the silane coating layer allows Li ions to permeate through the coating while maintaining particle stability. The porosity ensures that the coating does not act as a barrier to ion transport, thus preventing the hindrance of Li ion permeation despite the presence of the protective layer.
Solution Approach 2:
The coating layer is designed with specific local properties - porous structure with controlled thickness - that allow different functions in different aspects: structural stability where needed and ion permeation where required. The local quality of the porous coating enables simultaneous achievement of particle stability and fast Li ion permeation.
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 improved battery capacity, cycle retention rate, and initial efficiency, with reduced irreversible capacity and suppressed side reactions, enabling industrial production of high-performance lithium-ion batteries.
Implementation Method 1
it has gradually come to light by experimentation that high-temperature treatment (pyrolysis) of an organic substance containing Si-O-Si bonds forms a porous coating layer
Implementation Method 2
the porous coating layer allows Li ions to permeate through it
Data Source
Figure 1~3
AI summary
The present invention is a negative electrode active material for a non-aqueous electrolyte secondary battery, containing a negative electrode active material particle, wherein the negative electrode active material particle comprises a silicon compound particle containing a silicon compound (SiOx: 0.5 ≤ x ≤ 1.6), the silicon compound particle contains a Li compound, at least a part of the silicon compound particle is coated with a carbon material, and an O-component fragment and a CH-component fragment are detected from the negative electrode active material particle in a measurement by TOF-SIMS, and a ratio of a peak intensity A of the O-component fragment to a peak intensity B of the CH-component fragment is 0.5 ≤ A/B ≤ 100. This provides a negative electrode active material for a non-aqueous electrolyte secondary battery capable of increasing battery capacity and improving the cycle characteristics and battery initial efficiency.