Carbon-Coated Silicon Negative Electrode Material for Battery Capacity
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Solution Overview
Problem
Lithium-ion secondary batteries using silicon materials face challenges in achieving high cycle performance and initial efficiency due to the expansion and breakage of silicon active material particles, leading to electrolyte decomposition and reduced battery capacity.
Innovation Solution
A negative electrode material comprising silicon compound particles coated with carbon, exhibiting a negative zeta potential and fragments of CyHz compounds, is developed. This material is produced using thermal chemical vapor deposition and evaluated for its surface properties and zeta potential to ensure even dispersion and improved conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon material is used as negative electrode active material to improve battery capacity, then battery capacity increases, but particle breakage occurs during charging and discharging
Solution Approach 1:
The patent applies composite materials by combining silicon particles with carbon coating to form a composite structure. The carbon coating layer envelops the silicon particles, providing mechanical strength and preventing breakage while maintaining the high capacity benefits of silicon. This composite approach resolves the contradiction between achieving high battery capacity and maintaining particle strength during cycling.
Solution Approach 2:
The carbon coating forms a flexible shell around the silicon particles. This thin film structure allows the coating to accommodate the expansion and contraction of silicon during charging and discharging while providing protective reinforcement that prevents particle breakage, thus maintaining both high capacity and particle integrity.
2Quantity of substance
If silicon active material particles are used to increase battery capacity, then battery capacity improves, but cycle performance deteriorates due to particle breakage and electrolyte decomposition
Solution Approach 1:
The carbon coating acts as a flexible shell that accommodates silicon expansion during lithium insertion while preventing particle breakage. This protective layer maintains particle integrity over multiple cycles, significantly improving cycle performance while preserving the high capacity advantage of silicon materials.
Solution Approach 2:
The carbon coating serves as an intermediary between the silicon particles and the electrolyte. It prevents direct contact between the silicon surface and electrolyte, thereby preventing electrolyte decomposition reactions while still allowing lithium ion transport, thus improving cycle performance without sacrificing capacity.
3Strength
If carbon coating is applied to silicon particles to prevent breakage, then particle strength improves, but manufacturing complexity increases
Solution Approach 1:
The patent optimizes the carbon coating parameters including thickness (1-100 nm), carbon-to-silicon ratio, and coating uniformity to achieve the desired particle strength. By carefully controlling these parameters, the manufacturing process remains feasible while obtaining sufficient mechanical reinforcement to prevent particle breakage during battery cycling.
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 carbon-coated silicon compound particles demonstrate enhanced capacity maintenance, initial efficiency, and cycle performance by preventing particle breakage and electrolyte decomposition, leading to improved battery stability and performance.
Implementation Method 1
negative electrode active material particles containing a silicon compound expressed by SiOx at least partially coated with a carbon coating
Implementation Method 2
This material is produced using thermal chemical vapor deposition
Implementation Method 3
evaluated for its surface properties and zeta potential to ensure even dispersion and improved conductivity
Data Source
AI summary
The present invention provides a negative electrode material for a non-aqueous electrolyte secondary battery, comprising negative electrode active material particles containing a silicon compound expressed by SiOx at least partially coated with a carbon coating where 0.5≤x≤1.6. The negative electrode active material particles have a negative zeta potential and exhibiting fragments of CyHz compound in an outermost surface layer of the silicon compound when subjected to TOF-SIMS. This negative electrode material can increase the battery capacity and improve the cycle performance and battery initial efficiency. The invention also provides a negative electrode active material layer, a negative electrode, and a non-aqueous electrolyte secondary battery using this material, and a method of producing this material.