SiOx Surface Layer Atomic Ratio for Battery Cycle Stability
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Solution Overview
Problem
Rechargeable batteries using lithium ions face challenges in maintaining battery characteristics such as cycle and initial charging and discharging performance due to the expansion and contraction of silicon-based negative electrode active materials, leading to surface degradation and increased electrical resistance.
Innovation Solution
The use of a negative electrode active material with a specific atomic ratio of Si to O (30-75 atomic %) in the surface layer, combined with a non-crystalline or low crystalline coating portion, helps in maintaining lithium ion occlusion and release efficiency while reducing surface degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If Si is used as negative electrode active material to increase battery capacity, then the theoretical capacity increases significantly (4199 mAh/g vs 372 mAh/g for graphite), but the material vigorously expands and contracts during charge and discharge causing surface cracking and degradation
Solution Approach 1:
The patent applies parameter changes by precisely controlling the atomic ratio of Si to O in the surface layer within 30-75 atomic % Si. This specific compositional parameter optimization reduces surface degradation and cracking during expansion-contraction cycles while maintaining high capacity, directly resolving the contradiction between capacity and cycle stability
Solution Approach 2:
The patent employs composite materials by creating a Si-SiOx surface layer structure where silicon is combined with silicon oxide in specific ratios. This composite structure provides both the high capacity of Si and the stability of SiOx, preventing surface cracking while maintaining lithium ion occlusion and release efficiency
2Productivity
If the negative electrode active material surface area is increased to improve reaction efficiency, then the initial charging and discharging characteristics improve, but the electrolytic solution is consumed more rapidly due to increased decomposition reactions
Solution Approach 1:
The patent optimizes the atomic ratio parameter of Si to O (30-75 atomic % Si) in the surface layer to achieve a balance where sufficient surface area is available for efficient lithium ion reaction without excessive electrolytic solution decomposition. This parameter control reduces harmful side reactions while maintaining high productivity
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 the battery's capacity, initial charging and discharging characteristics, and cycle stability by optimizing the atomic ratio and crystallinity of the negative electrode active material, thereby improving overall battery performance.
Implementation Method 1
a negative electrode active material capable of occluding and releasing lithium ions or the like
Implementation Method 2
since Si vigorously expands and contracts during charge and discharge
Data Source
AI summary
A rechargeable battery including: a positive electrode; a negative electrode including active material; and an electrolytic solution, in which the active material is capable of occluding and releasing lithium ions and includes Si and O as constituent elements, and an atomic ratio (Si/(Si+O)) of Si with respect to Si and O is 30 atomic % to 75 atomic % in a surface of the active material.