Raman-Tuned Carbon-Coated Silicon Oxide Anodes for Cycle Stability
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Solution Overview
Problem
Current lithium-ion secondary batteries using silicon as a negative electrode active material face challenges in achieving cycle stability equivalent to those using carbon-based active materials, due to cracking and degradation of the negative electrode active material during charge-and-discharge.
Innovation Solution
A negative electrode active material is developed comprising silicon oxide particles coated with a carbon layer, where the carbon layer has a peak position attributed to the G band in a Raman spectrum between 1590 cm−1 and 1597 cm−1, reducing the number of graphene edges and suppressing the formation of a Solid Electrolyte Interphase (SEI) film.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon is used as a negative electrode active material to improve battery capacity, then the battery capacity increases significantly, but the negative electrode active material becomes prone to cracking during charge-and-discharge
Solution Approach 1:
The patent uses silicon oxide particles coated with a carbon layer to create a composite material structure. The carbon layer coating (with specific G band peak position indicating few graphene layers) protects the silicon oxide particles from cracking during charge-and-discharge cycles while maintaining high battery capacity. This composite structure resolves the contradiction between achieving high capacity and maintaining cycle stability.
2Reliability
If the negative electrode active material is coated with a carbon layer to prevent cracking, then cycle characteristics improve, but side reactions with electrolyte may increase
Solution Approach 1:
The patent carefully controls the parameters of the carbon layer coating, specifically the G band peak position in the Raman spectrum (1590-1597 cm⁻¹), which indicates the number of graphene layers. By optimizing this parameter to have few graphene layers, the patent reduces side reactions with electrolyte while maintaining the protective effect against cracking, thus resolving the contradiction between improving cycle characteristics and minimizing harmful side reactions.
3Strength
If more graphene layers are present in the carbon coating, then the coating provides better protection, but the number of graphene edges increases leading to more SEI film formation
Solution Approach 1:
The patent optimizes the graphene layer structure by controlling the G band peak position to indicate few graphene layers. This parameter optimization reduces the number of graphene edges that would otherwise generate excessive SEI film and consume electrolyte, while still providing sufficient mechanical protection. This resolves the contradiction between providing adequate protection and minimizing electrolyte consumption.
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 proposed negative electrode active material enhances cycle characteristics and maintains high battery capacity by reducing side reactions with the electrolyte and minimizing material degradation, thereby improving the overall performance of lithium-ion secondary batteries.
Implementation Method 1
a carbon layer having a peak position attributed to a G band in a range of more than 1590 cm−1 and 1597 cm−1 or less in a Raman spectrum
Data Source
AI summary
A negative electrode active material contains negative electrode active material particles, in which the negative electrode active material particles contain silicon oxide particles coated with a carbon layer, and the carbon layer has a peak position attributed to a G band in a range of more than 1590 cm−1 and 1597 cm−1 or less in a Raman spectrum obtained from Raman spectrometry for at least a part of the carbon layer. This can provide the negative electrode active material capable of improving cycle characteristics when used as the negative electrode active material of a secondary battery.