Acetonitrile Electrolyte Additive Suppresses Complex Cations
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Solution Overview
Problem
Lithium ion secondary batteries using acetonitrile-based electrolyte solutions exhibit inferior high-temperature durability performance compared to those using carbonate solvents, leading to increased internal resistance and degradation issues due to the formation of complex cations with transition metals, which affect electrode stability and protective films.
Innovation Solution
Incorporating a specific nitrogen-containing cyclic compound as an additive in a non-aqueous electrolyte solution containing acetonitrile and a fluorine-containing inorganic lithium salt, which suppresses the generation of complex cations and maintains excellent load characteristics and cycling performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If acetonitrile-based electrolyte solution is used, then viscosity and dielectric constant balance is improved, but high-temperature durability performance deteriorates due to complex cation formation
Solution Approach 1:
A nitrogen-containing cyclic compound is introduced as an intermediary substance between acetonitrile and transition metals. This additive preferentially coordinates with transition metals to form stable complexes, preventing acetonitrile from forming harmful complex cations. The intermediary substance thus mediates the interaction between acetonitrile and transition metals, eliminating the harmful effect while preserving the beneficial properties of acetonitrile.
Solution Approach 2:
The harmful reductive decomposition of acetonitrile at the negative electrode is converted into a beneficial effect by controlling the decomposition products to form protective films. The nitrogen-containing cyclic compound guides the decomposition process to create stable protective layers on the negative electrode, transforming the harmful decomposition into a protective mechanism that enhances battery durability.
2Power
If acetonitrile is used as solvent, then load characteristics are improved, but internal resistance increases due to complex cation generation at high temperature
Solution Approach 1:
The nitrogen-containing cyclic compound acts as an intermediary that binds to transition metals, preventing them from forming complex cations with acetonitrile. This intermediary mechanism eliminates the source of internal resistance increase while preserving the excellent load characteristics provided by acetonitrile's superior viscosity-dielectric constant balance.
3Stability of the object's composition
If high concentration of electrolyte salt is dissolved in acetonitrile, then liquid state stability is maintained, but reductive decomposition at negative electrode is suppressed insufficiently
Solution Approach 1:
The nitrogen-containing cyclic compound serves as an intermediary that preferentially coordinates with transition metals, preventing them from catalyzing the reductive decomposition of acetonitrile at the negative electrode. This intermediary action provides superior protection compared to simply increasing electrolyte salt concentration, as it directly addresses the root cause of decomposition through transition metal complexation.
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 enhances the high-temperature durability and cycling performance of lithium ion secondary batteries by preventing the formation of complex cations, thereby reducing internal resistance and maintaining superior load characteristics.
Implementation Method 1
Incorporating a specific nitrogen-containing cyclic compound as an additive in a non-aqueous electrolyte solution containing acetonitrile and a fluorine-containing inorganic lithium salt, which suppresses the generation of complex cations
Implementation Method 2
a non-aqueous electrolyte solution comprising: a non-aqueous solvent containing acetonitrile, a fluorine-containing inorganic lithium salt
Data Source
AI summary
The purpose of the present invention is to provide a nonaqueous electrolyte that contains acetonitrile having an excellent balance between viscosity and the dielectric constant and a fluorine-containing inorganic lithium salt, wherein the generation of complex cations comprising a transition metal and acetonitrile is suppressed, excellent load characteristics are exhibited, and increases in internal resistance upon repeated charge/discharge cycles are suppressed; a further purpose of the present invention is to provide a nonaqueous secondary battery. The present invention relates to a nonaqueous electrolyte which contains: a nonaqueous solvent comprising acetonitrile; a fluorine-containing inorganic lithium salt; and a specific nitrogenous cyclic compound typified by benzotriazole.