Disulfonyl Additive for Stable SEI in Non-Aqueous Electrolytes
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Solution Overview
Problem
Conventional additives for non-aqueous electrolyte solutions in electrical storage devices, such as lithium-ion batteries and electric double layer capacitors, face challenges in forming a stable solid electrolyte interface (SEI) that maintains performance over time, particularly due to high LUMO energy levels and chemical instability, leading to reduced cycle performance, discharge/charge capacity, and increased internal resistance.
Innovation Solution
A disulfonyl compound with a specific molecular structure, represented by formulas (1-1) and (1-2), is introduced, which has a lowest unoccupied molecular orbital energy of -3.0 to 0.4 eV, a standard enthalpy of formation between -921 to -167 kJ/mol, and an enthalpy change with hydrolysis reaction of -21 to 21 kJ/mol, forming a stable SEI on the electrode surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional additives are used in non-aqueous electrolyte solutions, then initial SEI formation occurs, but the SEI is unstable and decomposes over time leading to reduced cycle performance and increased internal resistance
Solution Approach 1:
The patent changes the chemical parameters of the additive by introducing a disulfonyl compound with specific LUMO energy levels (-3.0 to 0.4 eV) and enthalpy of formation (-921 to -167 kJ/mol). These parameter changes enable the formation of a stable SEI film that maintains its integrity over repeated charge/discharge cycles, resolving the contradiction between initial SEI formation and long-term SEI stability.
Solution Approach 2:
The patent employs a composite molecular structure consisting of disulfonyl groups combined with specific substituents (alkyl, silyl, phosphonic acid ester, acyl, cyano, or nitro groups). This composite structure creates an SEI film with enhanced stability and durability, preventing decomposition over time while maintaining good cycle performance.
2Reliability
If additives with high LUMO energy are used, then SEI formation occurs, but the additive is chemically unstable and degrades easily leading to reduced discharge/charge capacity
Solution Approach 1:
The patent optimizes the LUMO energy parameter to a specific range (-3.0 to 0.4 eV) that balances chemical stability and electrochemical activity. This parameter optimization ensures the additive forms a stable SEI film while maintaining good ion transport properties, thereby achieving both chemical stability and high discharge/charge capacity without mutual compromise.
3Duration of action of stationary object
If conventional electrolyte additives are used, then initial cell performance is achieved, but storage stability is poor and performance degrades with temperature changes and moisture exposure
Solution Approach 1:
The disulfonyl compound creates an inert-like protective SEI film on the electrode surface that acts as a barrier against moisture and temperature-induced degradation. This SEI film stabilizes the electrode-electrolyte interface, protecting the cell performance during long-term storage and under varying environmental conditions, thereby achieving both storage stability and performance consistency.
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 disulfonyl compound enhances cycle performance, discharge/charge capacity, and reduces internal resistance in electrical storage devices by forming a stable SEI, while providing excellent storage stability and resistance to moisture and temperature changes, allowing for long-term storage and use of the non-aqueous electrolyte solution.
Implementation Method 1
For an indicator of the adaptability of an additive for a non-aqueous electrolyte solution for electrochemical reduction on an electrode of non-aqueous electrolyte solution secondary cells
Implementation Method 2
a compound having a low LUMO energy is an excellent electron acceptor, and is used as an additive for a non-aqueous electrolyte solution capable of forming a stable SEI on the surface of an electrode
Data Source
Figure 1
AI summary
The present invention aims to provide an additive for a non-aqueous electrolyte solution with excellent storage stability capable of forming a stable SEI on the surface of an electrode to improve cell performance such as a cycle performance, a discharge/charge capacity, and internal resistance, when the additive is used for electrical storage devices such as non-aqueous electrolyte solution secondary cells and electric double layer capacitors. The present invention also aims to provide a non-aqueous electrolyte solution containing the additive for a non-aqueous electrolyte solution and to provide an electrical storage device using the non-aqueous electrolyte solution. The present invention is an additive for a non-aqueous electrolyte solution, comprising a compound that has a structure represented by the formula (1-1) or (1-2): in which A represents CmH(2m-n)Zn, m being an integer of 1 to 6, n being an integer of 0 to 12, and Z representing a substituted or unsubstituted alkyl group, a silyl group, a phosphonic acid ester group, an acyl group, a cyano group, or a nitro group, the compound having a lowest unoccupied molecular orbital energy of -3.0 to 0.4 eV, a standard enthalpy of formation of -220 to -40 kcal/mol, and an enthalpy change with hydrolysis reaction of -5 to 5 kcal/mol.