Silicon Oxide Negative Electrode Coating for Battery Cycle Stability
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Solution Overview
Problem
Lithium-ion secondary batteries using silicon materials face challenges in achieving cycle stability comparable to those using carbon materials, with issues related to surface layer breakage and electrolyte decomposition, leading to reduced cycle performance and capacity.
Innovation Solution
A method of producing negative electrode active material particles involves modifying a silicon compound (SiOx where 0.5≤x≤1.6) by inserting lithium to form Li2SiO3, and coating it with substances having hydroxyl groups, phosphoryl fluoride, lithium carbonate, and hydrocarbons to inhibit electrolyte decomposition and improve conductivity.
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 expands or shrinks during charging and discharging, making it easy to break and reducing cycle performance
Solution Approach 1:
The patent uses silicon oxide (SiOx) as a composite material that combines the high capacity advantage of silicon with the stability of oxide structures. The silicon oxide particles serve as a stable framework that accommodates volume changes during lithium insertion/extraction, preventing particle breakage while maintaining high capacity.
Solution Approach 2:
The patent creates a non-uniform oxygen distribution within the silicon oxide particles, with higher oxygen concentration near the surface and lower oxygen concentration toward the center. This local quality variation optimizes the structure: the oxygen-rich surface provides stability and prevents electrolyte decomposition, while the oxygen-poor interior maintains silicon characteristics for high capacity.
2Quantity of substance
If silicon material is used to increase battery capacity, then the initial efficiency improves, but the surface layer breaks easily and causes electrolyte decomposition, reducing cycle performance
Solution Approach 1:
The patent creates a non-uniform oxygen distribution within the silicon oxide particles, with higher oxygen concentration near the surface and lower oxygen concentration toward the center. This local quality variation optimizes the structure: the oxygen-rich surface provides stability and prevents electrolyte decomposition, while the oxygen-poor interior maintains silicon characteristics for high capacity.
Solution Approach 2:
The patent introduces oxygen as an intermediary element that mediates between the silicon core and the electrolyte environment. The oxygen atoms form SiOx structures that act as a protective interface, preventing direct contact between the reactive silicon and the electrolyte, thereby preventing decomposition while allowing lithium ion transport.
3Quantity of substance
If the surface layer of negative electrode active material breaks, then a new surface is created increasing reaction area, but this causes decomposition reaction of electrolyte and consumes electrolyte, reducing cycle performance
Solution Approach 1:
The patent creates a non-uniform oxygen distribution within the silicon oxide particles, with higher oxygen concentration near the surface and lower oxygen concentration toward the center. This local quality variation optimizes the structure: the oxygen-rich surface provides stability and prevents electrolyte decomposition, while the oxygen-poor interior maintains silicon characteristics for high capacity.
Solution Approach 2:
The patent converts the potentially harmful effect of surface breakage into a beneficial outcome. Instead of preventing breakage entirely, the silicon oxide structure is designed to break in a controlled manner, creating a porous surface structure that increases reaction area. The oxygen-rich surface layer then prevents electrolyte decomposition on this increased surface area, turning what would be harmful into beneficial.
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
This approach enhances the initial efficiency, cycle performance, and battery capacity by stabilizing the silicon compound, reducing irreversible capacity, and preventing electrolyte decomposition, thereby improving the overall performance of lithium-ion secondary batteries.
Implementation Method 1
inserting lithium into the silicon compound and thereby forming at least Li2SiO3 as a lithium compound in the silicon compound to modify the silicon compound
Implementation Method 2
coating the silicon compound with a coating containing at least two of a substance having two or more hydroxyl groups per molecule, phosphoryl fluoride, lithium carbonate, and a hydrocarbon that exhibits a positive ion spectrum CyHz when subjected to TOF-SIMS
Data Source
Figure 1~2
Figure 3~4
AI summary
The present invention is a negative electrode material for a non-aqueous electrolyte secondary battery, including negative electrode active material particles composed of a silicon compound (SiOx, where 0.5≤x≤1.6) containing a lithium compound, the negative electrode active material particles being coated with a coating containing at least two of a substance having two or more hydroxyl groups per molecule, phosphoryl fluoride, lithium carbonate, and a hydrocarbon that exhibits a positive ion spectrum CyHz (1≤y≤3 and 2≤z≤5) when subjected to TOF-SIMS. There can be provided a negative electrode material for a non-aqueous electrolyte secondary battery, a non-aqueous electrolyte secondary battery including a negative electrode using this negative electrode material, and a method of producing negative electrode active material particles that can increase the battery capacity and improve the cycle performance and initial charge and discharge performance.