SiOx Negative Electrode Active Material with Carbon Surface Layer
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Solution Overview
Problem
Lithium ion secondary batteries using silicon as a negative electrode material face challenges in achieving cycle stability equivalent to those using carbon materials, with issues such as expansion and contraction leading to breakage and electrolyte consumption, which deteriorate cycle characteristics.
Innovation Solution
A silicon-based negative electrode active material with a composition of SiOx (0.5≤x≤1.6) and two or more peaks in the O 1s peak shape in X-ray photoelectron spectroscopy, along with specific peak intensity ratios and crystallinity, is used, combined with an electrochemical method for reforming, to enhance battery capacity and charge/discharge characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon is used as a negative electrode active material to improve battery capacity, then the battery capacity increases significantly, but the negative electrode active material expands and contracts during charge/discharge leading to breakage and deteriorated cycle characteristics
Solution Approach 1:
The patent uses a composite structure consisting of a silicon-based negative electrode active material core surrounded by a carbon-containing surface layer. This composite design allows the silicon core to provide high battery capacity while the carbon surface layer prevents breakage during expansion and contraction, thereby maintaining good cycle characteristics.
2Quantity of substance
If the surface layer of negative electrode active material breaks during charge/discharge, then the reaction area increases, but electrolytic solution is consumed and cycle characteristics deteriorate
Solution Approach 1:
The patent applies a carbon-containing surface layer to the silicon-based negative electrode active material before use. This preliminary protective coating prevents the surface from breaking during charge/discharge cycles, avoiding unnecessary electrolytic solution consumption while still allowing lithium ion insertion and extraction.
3Reliability
If carbon materials are used as negative electrode active material to ensure cycle stability, then cycle characteristics are maintained, but battery capacity is limited compared to silicon
Solution Approach 1:
The patent creates a composite negative electrode active material where silicon provides high battery capacity (theoretical capacity of 4199 mAh/g) and a carbon-containing surface layer provides cycle stability. This composite structure combines the advantages of both materials, achieving high capacity while maintaining good cycle characteristics.
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 solution results in improved battery capacity, cycle stability, and initial charge/discharge characteristics, achieving high energy density and extended cycle life for lithium ion secondary batteries.
Implementation Method 1
a negative electrode active material which can absorb and emit a lithium ion
Data Source
AI summary
The present invention is a negative electrode active material for a negative electrode active material layer of a lithium ion secondary battery, wherein: the negative electrode active material comprises silicon-based material consisting of SiOx (0.5≤x≤1.6); and the negative electrode active material has two or more peaks in a region of a bond energy ranging from 520 eV to 537 eV in an O 1s peak shape given in an X-ray photoelectron spectroscopy. As a result, it is possible to provide a negative electrode active material in which a battery capacity can be increased and cycle characteristics and initial charge/discharge characteristics can be improved when used as a negative electrode active material for a lithium ion secondary battery.