SiO Coated Silicon Anode for Battery Cycle Life
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Lithium ion secondary batteries using silicon as the negative electrode active material face challenges such as cracking due to expansion and shrinkage during charge and discharge, leading to degradation of battery characteristics like cycle performance and safety.
Innovation Solution
A lithium ion secondary battery negative electrode configuration featuring a core portion capable of occluding and releasing lithium ions, with an amorphous or low-crystalline coating portion containing Si and O, and a fibrous carbon portion on the surface of the coating, where the atomic ratio of O to Si ranges from 0.5 to 1.8, enhancing the battery's cycle and discharge characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If Si is used as the negative electrode active material to increase battery capacity, then the theoretical capacity increases significantly (4.199 mAh/g vs graphite's 372 mAh/g), but cracking occurs easily due to significant expansion and shrinkage during charge and discharge
Solution Approach 1:
The negative electrode active material is divided into multiple particles with specific size distribution (D10≥5 μm, D50≥10 μm, D90≥20 μm). This segmentation reduces internal stress during expansion and shrinkage, preventing cracking while maintaining high capacity
Solution Approach 2:
A coating layer is formed on the surface of Si particles before use. This preliminary coating prevents direct exposure of fresh surfaces during cracking, reducing electrolytic solution decomposition and maintaining cycle characteristics
2Quantity of substance
If Si is used as the negative electrode active material, then battery capacity increases, but the surface area (reaction area) increases when cracked, leading to electrolytic solution consumption and coating film formation
Solution Approach 1:
A coating layer is pre-formed on Si particle surfaces to prevent electrolytic solution contact with fresh surfaces generated during cracking, thereby reducing solution consumption and unwanted coating film formation
Solution Approach 2:
The cracking phenomenon is converted into a benefit by controlling particle size distribution, which reduces the severity of cracking and minimizes harmful electrolytic solution decomposition while maintaining high capacity
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 proposed configuration improves the battery's cycle characteristics, initial charge and discharge characteristics, and load characteristics by preventing cracking and maintaining smooth lithium ion occlusion and release, while reducing electrical resistance and enhancing the battery's overall performance.
Implementation Method 1
cracking occurs mainly in the vicinity of the surface layer of the negative electrode active material easily because of significant expansion and shrinkage of the negative electrode active material during charge and discharge
Implementation Method 2
a fibrous carbon portion disposed on at least a part of the surface of the coating portion
Implementation Method 3
the negative electrode contains a negative electrode active material capable of occluding and releasing lithium ions
Data Source
AI summary
A lithium ion secondary battery is provided with a positive electrode, a negative electrode containing an active material, and an electrolytic solution, wherein the active material includes a core portion capable of occluding and releasing lithium ions, an amorphous or low-crystalline coating portion disposed on at least a part of the surface of the core portion, and a fibrous carbon portion disposed on at least a part of the surface of the coating portion, and the coating portion contains Si and O as constituent elements, while the atomic ratio y (O/Si) of O relative to Si satisfies 0.5≦y≦1.8.