Lithium-Sulfur Positive Electrode With Niobium Tungsten Oxide
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Solution Overview
Problem
Lithium-sulfur secondary batteries suffer from polysulfide shuttling, leading to irreversible loss of positive electrode active material and reduced lifetime characteristics.
Innovation Solution
Incorporating a metal oxide-based additive, specifically niobium tungsten oxide, into the positive electrode active material layer to enhance polysulfide adsorption and desorption, thereby suppressing the shuttling phenomenon and improving discharge capacity and lifetime.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional positive electrode is used, then the battery can operate, but it generates harmful gases (CO, CO2, CF4, C2F6) during charging that reduce battery life and performance
Solution Approach 1:
The patent applies the principle of converting harmful factors into beneficial ones by using the generated fluorocarbon gases (CF4, C2F6) as a self-healing mechanism. These gases deposit on the electrode surface to form a protective film that prevents further harmful reactions, thus converting the harmful gas generation into a beneficial protective effect that extends battery life.
Solution Approach 2:
The patent introduces an intermediary substance (the fluorocarbon-containing compound) that mediates between the positive electrode and the electrolyte. This intermediary forms a protective interface layer that prevents direct harmful interactions while allowing beneficial ion transport, thus reducing harmful gas generation and improving battery reliability.
2Use of energy by moving object
If the battery is charged at high voltage (above 4.3V), then energy density is improved, but oxygen is released from the positive electrode which reduces battery life
Solution Approach 1:
The patent applies beforehand cushioning by pre-forming a protective film on the positive electrode surface before high-voltage charging occurs. This protective film acts as a cushion that prevents oxygen release during high-voltage operation, allowing the battery to achieve high energy density while maintaining reliability and extended battery life.
3Reliability
If battery life is extended through various measures, then reliability improves, but the battery weight increases
Solution Approach 1:
The patent applies parameter changes by modifying the chemical composition and concentration of the electrolyte (adding fluorocarbon-containing compounds at specific concentrations of 0.01-5 wt%). This parameter modification enables the formation of a protective film that extends battery life without requiring additional heavy structural components, thus improving reliability while maintaining lightweight design.
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 niobium tungsten oxide improves the discharge capacity and extends the battery's lifetime by promoting the conversion of long-chain polysulfides to short-chain polysulfides, minimizing capacity degradation and enhancing overall battery performance.
Implementation Method 1
When a lithium secondary battery using a specific positive electrode is charged, oxygen is released from the positive electrode
Implementation Method 2
it is an extremely important issue to prevent release of harmful gases such as carbon monoxide (CO), carbon dioxide (CO2), tetrafluoromethane (CF4), and perfluorocyclobutane (C2F6)
Data Source
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AI summary
The present invention relates to a positive electrode for a lithium secondary battery and to a lithium secondary battery comprising same. More specifically, by adding a predetermined amount of a metal oxide-based additive to the positive electrode, it is possible to improve discharge capacity and lifespan characteristics of the lithium secondary battery.