Silicon Anode Material Surface Chemistry for Stable Battery Cycling
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Solution Overview
Problem
Lithium ion secondary batteries using silicon as a negative electrode material face challenges in achieving initial charge/discharge characteristics and cycle stability comparable to those using carbon-based active materials, with issues related to expansion, surface degradation, and electrolyte consumption.
Innovation Solution
A negative electrode active material is developed containing silicon compounds with specific lithium silicates (Li2SiO3 and Li4SiO4) and surface modifications with Li2CO3 and LiOH, optimized in concentration and pH, along with a carbon-based active material, to enhance electronic conductivity and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon is used as the negative electrode active material to improve battery capacity, then the theoretical capacity increases 10 times or more compared to graphite, but the superficial layer becomes easily broken due to expansion and contraction during charge/discharge
Solution Approach 1:
The patent applies preliminary action by forming a protective coating layer on the silicon surface before it undergoes expansion and contraction during charge/discharge. The coating is applied in advance to prevent surface breakdown, addressing the structural weakness before it occurs during battery operation.
Solution Approach 2:
The patent uses composite materials by combining silicon with a protective coating material to create a core-shell structure. The silicon core provides high capacity while the outer coating layer provides mechanical strength and surface stability, resolving the contradiction between capacity and structural integrity.
2Quantity of substance
If the superficial layer of the negative electrode active material is broken, then a new surface is generated and the reaction area increases, but the electrolytic solution is consumed due to decomposition reactions on the new surface
Solution Approach 1:
The patent applies preliminary anti-action by pre-forming a stable surface coating that prevents the harmful decomposition reactions between the electrolytic solution and the silicon surface. This coating acts in advance to counteract the electrolyte consumption that would otherwise occur when new surfaces are exposed.
Solution Approach 2:
The patent converts the potentially harmful interaction between electrolyte and silicon surface into a beneficial stable coating layer. The controlled formation of this layer during initial cycles creates a protective interface that prevents further electrolyte decomposition while maintaining electrochemical activity.
3Quantity of substance
If the superficial layer of the negative electrode active material is broken, then a new surface is generated, but the cycle characteristics become easily degraded due to electrolytic solution decomposition
Solution Approach 1:
The patent applies preliminary action by pre-forming a stable surface coating that prevents the harmful decomposition reactions between the electrolytic solution and the silicon surface. This coating acts in advance to counteract the electrolyte consumption that would otherwise occur when new surfaces are exposed.
Solution Approach 2:
The patent converts the potentially harmful interaction between electrolyte and silicon surface into a beneficial stable coating layer. The controlled formation of this layer during initial cycles creates a protective interface that prevents further electrolyte decomposition while maintaining electrochemical activity.
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 improves the battery's capacity, initial efficiency, and cycle characteristics by stabilizing the surface and reducing irreversible capacity, while maintaining excellent electronic conductivity.
Implementation Method 1
inserting lithium into the particles of silicon compound such that the particles contain Li2SiO3 and Li4SiO4
Implementation Method 2
generating Li2CO3 and LiOH on a surface of the particles of negative electrode active material by washing the particles of negative electrode active material on the surface of which lithium nitride is generated with a solution containing water
Data Source
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AI summary
The present invention is a negative electrode active material including: particles of negative electrode active material, wherein the particles of negative electrode active material contain particles of silicon compound containing a silicon compound (SiOx:0.5≤x≤1.6); the particles of silicon compound contain at least one kind or more of Li2SiO3 and Li4SiO4; the particles of negative electrode active material contain Li2CO3 and LiOH on a surface thereof; and a content of the Li2CO3 is 0.01% by mass or more and 5.00% by mass or less relative to a mass of the particles of negative electrode active material and a content of the LiOH is 0.01% by mass or more and 5.00% by mass or less relative to the mass of the particles of negative electrode active material. Thus a negative electrode active material capable of improving initial charge/discharge characteristics and the cycle characteristics when used as a negative electrode active material of the secondary battery is provided.