Nonaqueous Battery Electrolyte with Tungsten-Silicon Coating
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Solution Overview
Problem
Nonaqueous electrolyte secondary batteries using lithium transition metal oxides with tungsten as a positive electrode active material face challenges in achieving good low-temperature regeneration characteristics due to the elution of tungsten and formation of high-resistance coating films on the negative electrode.
Innovation Solution
Incorporating silicon into the lithium transition metal oxide to suppress tungsten elution and form a low-resistance coating film containing both tungsten and silicon on the negative electrode, with a molar ratio of tungsten to silicon on the surface of the carbon material being 2 times or less, thereby improving low-temperature regeneration characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a lithium transition metal oxide containing W is used as a positive electrode active material, then output characteristics are improved, but low-temperature regeneration characteristics deteriorate due to W elution and formation of high-resistance coating films on the negative electrode
Solution Approach 1:
Si acts as an intermediary substance that mediates between the W-containing positive electrode material and the carbon negative electrode. The Si adheres to the carbon material surface along with W, forming a composite coating film where Si prevents W from forming high-resistance compounds, thereby maintaining low resistance while allowing W to provide its output-enhancing effects
Solution Approach 2:
The invention creates a composite coating film on the negative electrode surface containing both W and Si, with a controlled molar ratio (W/Si ≤ 2). This composite material combines the beneficial effects of W (improved output characteristics) with the protective effects of Si (prevention of high-resistance film formation), resolving the contradiction between power and low-temperature regeneration characteristics
2Power
If W is present on the negative electrode surface, then output characteristics are enhanced, but resistance increases due to formation of high-resistance coating films, deteriorating low-temperature regeneration characteristics
Solution Approach 1:
Si serves as a protective intermediary on the negative electrode surface, forming a low-resistance coating that prevents W from forming high-resistance compounds. The Si coating maintains electrical conductivity while allowing W to remain present for its beneficial effects on output characteristics
Solution Approach 2:
The invention changes the compositional parameters of the coating film by controlling the molar ratio of W to Si (W/Si ≤ 2). By adjusting this parameter, the film's resistance is optimized to be low, while still maintaining sufficient W content to provide enhanced output 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 addition of silicon to the lithium transition metal oxide effectively enhances the low-temperature regeneration characteristics of the battery by forming a low-resistance coating film, which improves the battery's performance and retention rate.
Implementation Method 1
W and Si adhering to the carbon material
Implementation Method 2
the amount of W adhering to the surface of the carbon material is 2 times or less in terms of a molar ratio to the amount of Si adhering to the surface of the carbon material... form a low-resistance coating film
Data Source
AI summary
A nonaqueous electrolyte secondary battery includes a positive electrode containing a lithium transition metal oxide as a positive electrode active material, a negative electrode containing a carbon material as a negative electrode active material, and a nonaqueous electrolyte. The lithium transition metal oxide contains W and Si, and W and Si adhere to the surface of the carbon material constituting the negative electrode active material. The amount of W adhering to the surface of the carbon material is 2 times or less in terms of a molar ratio to the amount of Si adhering to the surface of the carbon material.