SiOx Negative Electrode Silicon Coating for Battery Capacity Retention
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Solution Overview
Problem
Lithium-ion secondary batteries with silicon oxide particles as negative electrode active material experience low cycle capacity retention and post-high-temperature-storage capacity retention due to the presence of fluoroethylene carbonate in the electrolyte solution, which causes irreversible capacity loss and volume changes leading to battery degradation.
Innovation Solution
A lithium-ion secondary battery design featuring negative electrode active material particles with a silicon layer of specific thickness (10 nm to 100 nm) covering silicon oxide particles, and optionally a carbon layer, to mitigate the adverse effects of fluoroethylene carbonate, thereby reducing irreversible capacity loss and improving cycle and post-high-temperature-storage capacity retention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon oxide particles are used as negative electrode active material, then specific capacity increases, but cycle capacity retention decreases
Solution Approach 1:
The invention applies local quality modification by covering only the surface of silicon oxide particles with a silicon layer, rather than changing the bulk properties of the entire electrode. The core silicon oxide particles retain their high specific capacity characteristics, while the surface silicon layer provides protective functionality. This localized modification allows the material to simultaneously exhibit both high capacity and good cycle retention.
Solution Approach 2:
The negative electrode active material becomes a composite structure consisting of silicon oxide particles coated with a silicon layer. This composite material combines the advantages of both components: silicon oxide provides high specific capacity, while the silicon coating provides stability and prevents degradation. The composite structure enables the electrode to achieve both high capacity and good cycle retention simultaneously.
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 silicon layer prevents the formation of lithium orthosilicate, reducing irreversible capacity loss, while the carbon layer enhances electrical conductivity, leading to improved cycle and post-high-temperature-storage capacity retention by minimizing battery degradation.
Implementation Method 1
Each of the negative electrode active material particles contains at least a silicon oxide particle and a silicon layer. The silicon layer covers a surface of the silicon oxide particle.
Implementation Method 2
FEC and/or the like contained in the electrolyte solution may break down on surfaces of the SiOx particles. As a result of the breakdown of FEC and/or the like, a film may be formed. The film is also called solid electrolyte interface (SEI) film.
Implementation Method 3
The negative electrode active material particle may further contain a carbon layer. The carbon layer may cover a surface of the silicon layer.
Data Source
AI summary
A lithium-ion secondary battery includes at least a negative electrode, a positive electrode, and an electrolyte solution. The negative electrode includes at least negative electrode active material particles. Each of the negative electrode active material particles contains at least a SiOx particle and a Si layer. The Si layer covers a surface of the SiOx particle. The Si layer has a thickness not smaller than 10 nm and not greater than 100 nm. The electrolyte solution contains at least one selected from the group consisting of FEC and VC.