SiOx Negative Electrode With Silicon Dioxide Covering Layer
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Solution Overview
Problem
The decomposition of the electrolytic solution caused by the negative-electrode active material in lithium-ion secondary batteries leads to a high-resistance coating on the surface of the negative electrode, resulting in decreased charge-discharge capacity and deteriorated cycle characteristics.
Innovation Solution
A negative electrode with a current collector, a negative-electrode active material body of SiOx (0.1≦x≦1.2), and a covering layer of silicon dioxide with a thickness between 1 nm and 10 nm is used to suppress the decomposition reaction of the electrolytic solution, minimizing polarization and improving charge-discharge cycle characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If SiOx is used as the negative-electrode active material to achieve high capacity, then the charge-discharge capacity is improved, but the electrolytic solution decomposes due to contact between SiOx and the electrolytic solution, forming a high-resistance coating that deteriorates cycle characteristics
Solution Approach 1:
A covering layer composed of silicon oxide (SiOy, where 1.5 < y ≤ 2) is introduced as an intermediary between the SiOx active material body and the electrolytic solution. This covering layer prevents direct contact between the active material and electrolyte, suppressing decomposition reactions while maintaining lithium ion permeability, thus resolving the contradiction between high capacity and cycle stability
Solution Approach 2:
The negative electrode is constructed as a composite structure combining SiOx active material body with a silicon oxide covering layer. This composite design leverages the high capacity of SiOx while the silicon oxide layer provides protective functions, achieving both high charge-discharge capacity and improved cycle characteristics
2Reliability
If a covering layer is formed on the negative-electrode active material body to suppress electrolytic solution decomposition, then cycle characteristics are improved, but the charge-discharge capacity decreases due to increased resistance
Solution Approach 1:
The covering layer thickness is precisely controlled within the range of 1 nm to 10 nm, and the silicon oxide composition ratio (y value where 1.5 < y ≤ 2) is optimized to balance protective function and ion conductivity. This parameter optimization ensures the covering layer suppresses decomposition while minimizing resistance increase, maintaining high charge-discharge 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 solution effectively suppresses the decomposition reaction, maintaining high charge-discharge capacity and improving the cycle characteristics of lithium-ion secondary batteries by preventing the formation of a high-resistance coating on the negative electrode.
Implementation Method 1
a covering layer which is composed of silicon dioxide and has a thickness which is greater than 1 nm and no more than 10 nm... the decomposition reaction of an electrolytic solution can be suppressed
Data Source
AI summary
A negative electrode 100 for a lithium secondary battery includes: a current collector 11; a negative-electrode active material body 12 supported by the current collector 11, the negative-electrode active material body 12 having a chemical composition represented as SiOx (0.1≦x≦1.2); and a covering layer 14 formed on the negative-electrode active material body 12, the covering layer 14 having a chemical composition composed of silicon dioxide. The covering layer 12 has a thickness which is greater than 1 nm and no more than 10 nm.