Silicon Anode Coating for Lithium-Ion Battery Cycle Life
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Solution Overview
Problem
Lithium-ion secondary batteries face challenges in improving cycle characteristics and initial charge-discharge characteristics due to the swelling and shrinking of silicon-based anode active materials, which lead to surface cracking and electrolyte decomposition, reducing battery performance.
Innovation Solution
An anode configuration featuring a core section with a silicon-based material (SiO x : 0≤x<0.5) coated with an amorphous or low-crystalline silicon-based material (SiO y : 0.5≤y≤1.8) to prevent surface exposure during charge and discharge, ensuring smooth lithium ion insertion and extraction while protecting the core section from electrolyte decomposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon is used as the anode active material to increase battery capacity, then the theoretical capacity increases significantly (4199 mAh/g vs 372 mAh/g for graphite), but the anode active material swells and shrinks severely causing surface cracking
Solution Approach 1:
The patent applies the nesting principle by placing the silicon-based anode active material particles inside a protective coating layer formed from electrolyte solution decomposition products. This nested structure allows the high-capacity silicon core to be protected from direct exposure to the electrolyte, preventing surface cracking while maintaining the high capacity benefit. The coating layer acts as a protective shell surrounding the silicon core, similar to a nested doll structure.
Solution Approach 2:
The patent employs composite materials by creating a core-shell structure where the core consists of silicon-based anode active material particles and the shell consists of a coating layer formed from electrolyte solution decomposition products. This composite structure combines the high capacity advantage of silicon with the protective benefits of the coating layer, resolving the contradiction between capacity improvement and structural stability.
2Quantity of substance
If the anode active material surface is cracked due to swelling and shrinking, then a high-reactive newly-formed surface is formed increasing surface area, but the decomposition reaction of electrolytic solution occurs consuming the electrolyte
Solution Approach 1:
The patent applies preliminary anti-action by forming a protective coating layer on the surface of the silicon-based anode active material particles before they can undergo severe cracking and expose high-reactive surfaces. This pre-formed coating prevents direct contact between the electrolyte and the silicon surface, thereby preventing electrolyte decomposition and consumption while still allowing lithium ion insertion and extraction.
Solution Approach 2:
The coating layer formed from electrolyte solution decomposition products acts as an intermediary between the silicon-based anode active material and the electrolyte solution. This intermediary layer allows lithium ions to pass through while preventing direct contact between the electrolyte and the silicon surface, thereby preventing harmful decomposition reactions while maintaining electrochemical functionality.
3Reliability
If the anode active material is coated with a protective layer to prevent cracking, then cycle characteristics improve, but the initial charge-discharge characteristics may be affected due to additional resistance
Solution Approach 1:
The patent applies parameter changes by controlling the thickness and composition of the protective coating layer to optimize the balance between protection and conductivity. The coating layer is formed with specific properties that allow it to provide structural support and prevent cracking while maintaining sufficient lithium ion conductivity, thus improving cycle characteristics without significantly compromising initial charge-discharge performance.
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 configuration enhances cycle characteristics and initial charge-discharge characteristics by preventing electrolyte decomposition and maintaining the integrity of the anode active material, leading to improved battery performance in lithium-ion secondary batteries.
Implementation Method 1
a coating section applied to a part or a whole of a surface of the core section... protecting the core section from electrolyte decomposition
Implementation Method 2
an anode for lithium-ion secondary battery including an anode active material layer allowed to insert and extract lithium ions
Data Source
AI summary
A lithium-ion secondary battery allowed to improve cycle characteristics and initial charge-discharge characteristics is provided. The lithium-ion secondary battery includes a cathode; an anode; and an electrolytic solution. The anode includes an anode active material layer including a plurality of anode active material particles. The anode active material particles each include a core section and a coating section applied to a part or a whole of a surface of the core section, and the core section includes a silicon-based material (SiOx: 0≤x<0.5) and the coating section includes an amorphous or low-crystalline silicon-based material (SiOy: 0.5≤y≤1.8).