Amine Oxide Additive for Lithium Battery Electrolyte Stability
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Solution Overview
Problem
Nonaqueous electrolytic solutions used in lithium and lithium-ion batteries face issues with thermal decomposition and hydrolysis due to the instability of lithium hexafluorophosphate (LiPF6), leading to the formation of harmful byproducts like hydrogen fluoride, which corrodes the solid electrolyte interface and reduces battery performance.
Innovation Solution
Incorporating an amine oxide into the nonaqueous electrolytic solution, which acts as a scavenger for moisture and free acid, and a surfactant to improve wetting of separator membranes, thereby stabilizing lithium salts and enhancing battery performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If LiPF6 is used as the lithium salt in nonaqueous electrolytic solution, then electrochemical stability and conductivity are improved, but thermal stability deteriorates leading to decomposition and hydrolysis
Solution Approach 1:
The patent introduces LiFSO3 as an intermediary substance that mediates between LiPF6 and water. LiFSO3 acts as a buffer that reacts with water to form HF and LiF, preventing direct hydrolysis of LiPF6. This intermediary approach allows the system to maintain high conductivity from LiPF6 while reducing thermal decomposition through the presence of LiFSO3
Solution Approach 2:
The patent employs a composite electrolytic solution containing both LiPF6 and LiFSO3 salts together with cyclic carbonate and chain carbonate solvents. This composite formulation combines the high conductivity benefit of LiPF6 with the thermal stability and hydrolysis resistance of LiFSO3, creating a synergistic electrolyte system that addresses both electrochemical performance and thermal stability requirements
2Reliability
If cyclic esters with high polarity are used as solvents, then electrochemical stability is improved, but wetting of polypropylene and polyethylene separator membranes deteriorates
Solution Approach 1:
The patent applies local quality by using different carbonate solvents with different polarity characteristics in specific proportions. Cyclic carbonates (EC, PC, GVL) provide electrochemical stability at the electrode interfaces, while chain carbonates (DMC, DEC, EMC) provide better wetting of the separator membrane. This spatial and functional differentiation of solvent roles resolves the contradiction between electrochemical stability and wetting performance
Solution Approach 2:
The patent creates a composite solvent system combining cyclic carbonates and chain carbonates in specific weight ratios (cyclic carbonate 20-80 wt%, chain carbonate 20-80 wt%). This composite approach allows the electrolyte to simultaneously achieve good electrochemical stability from the cyclic components and adequate separator wetting from the chain components, resolving the polarity-wetting contradiction
3Ease of manufacture
If moisture and free acid are present in the electrolytic solution, then manufacturing simplicity is improved, but battery performance deteriorates due to corrosion of SEI
Solution Approach 1:
The patent introduces LiFSO3 as a protective intermediary that preferentially reacts with water and free acid impurities. This buffer substance acts as a sacrificial component that protects the LiPF6 from hydrolysis and prevents HF generation that would otherwise corrode the SEI. The presence of LiFSO3 allows simpler manufacturing tolerances while maintaining battery performance
Solution Approach 2:
The patent converts the potentially harmful presence of moisture and free acid into a beneficial effect by using LiFSO3 to react with these impurities. The reaction products (HF and LiF from LiFSO3 hydrolysis) are less harmful than direct LiPF6 hydrolysis, and the LiFSO3 itself forms protective films that stabilize the SEI. Thus, the impurities are transformed from harmful factors into a mechanism for forming protective interfaces
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 use of amine oxides in nonaqueous electrolytic solutions results in a stable battery with long cycle life and high discharge capacity retention by reducing decomposition and hydrolysis, thus improving the overall performance of lithium and lithium-ion batteries.
Implementation Method 1
Amine oxides, which are electrically neutral, act as a scavenger for moisture and free acid
Implementation Method 2
Amine oxides, which are electrically neutral, act as a scavenger for moisture and free acid and as a surfactant for wetting the polypropylene and/or polyethylene separator membrane
Implementation Method 3
Thermal decomposition of LiPF6 occurs at elevated temperatures (Reaction 1)
Implementation Method 4
Hydrolysis (Reaction 2) generally occurs due to moisture and acidic impurities in the lithium salt and electrolytic solution
Data Source
AI summary
The invention relates to the use of an amine oxide as an additive in a nonaqueous electrolytic solution. The electrolytic solution is suitable for use in electrochemical cells such as lithium batteries and lithium ion batteries. Batteries using this electrolyte solution have long life and high capacity retention.