Battery Electrolyte Additives for Stable Low-Impedance SEI Films
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Solution Overview
Problem
Existing electrolyte systems in secondary batteries exhibit high impedance, failing to form a uniform, dense, and stable solid electrolyte interphase (SEI) film, which affects the electrochemical performance and power performance of the battery.
Innovation Solution
An electrolyte comprising a cyclic sulfate compound and a metal ion additive is introduced, facilitating the formation of a stable SEI film with a mixture of organic and inorganic components, enhancing the interface stability and reducing impedance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional electrolyte systems are used, then the battery can operate, but the SEI film formed has high impedance and poor stability
Solution Approach 1:
The patent introduces a cyclic sulfate compound containing both inorganic sulfate groups and organic R groups, which forms a composite SEI film with dual characteristics: the inorganic sulfate component provides low electron conductivity and chemical stability, while the organic component provides flexibility and adaptability to volume changes. This composite structure simultaneously achieves low impedance and high stability.
Solution Approach 2:
The cyclic sulfate compound structure allows different parts of the molecule to serve different functions: the sulfate group (OSO2O) forms the inorganic film matrix that blocks electrons, while the R groups (alkyl, alkoxy, fluorinated, or nitrile-substituted) form organic components that provide mechanical flexibility. This local differentiation of material properties within the same compound enables the SEI film to exhibit both low impedance and high stability simultaneously.
2Reliability
If the SEI film is made denser to improve stability, then electron tunneling is prevented, but the rate performance deteriorates due to higher impedance
Solution Approach 1:
The patent modifies the chemical composition parameters of the SEI film by introducing cyclic sulfate compounds with specific molecular structures. The sulfate group concentration controls the electron-blocking capability, while the R group composition (including fluorinated and nitrile-substituted groups) adjusts the mechanical properties and ion transport characteristics. By optimizing these compositional parameters, the film achieves both density for stability and appropriate porosity for ion transport.
Solution Approach 2:
The organic R groups in the cyclic sulfate compound form flexible organic components within the SEI film structure. These flexible organic segments can accommodate volume changes of the negative electrode during cycling while maintaining film integrity. The flexibility prevents film cracking and detachment, ensuring long-term stability without requiring excessive film density that would impede ion transport.
3Reliability
If various compounds are added to form passivation layer, then side reactions are reduced, but the electrolyte system becomes more complex
Solution Approach 1:
The cyclic sulfate compound serves multiple functions simultaneously: the sulfate group forms the inorganic film matrix for electron blocking, the R groups provide organic components for flexibility, and specific substituents (fluorine, nitrile) enhance film stability and adhesion. This single compound performs what would traditionally require multiple different additives, simplifying the electrolyte composition while achieving comprehensive SEI film formation.
Solution Approach 2:
The patent merges the functions of multiple traditional additives into a single cyclic sulfate compound structure. Instead of adding separate inorganic film-forming agents and organic additives, the invention combines both functionalities into one molecular structure where the sulfate group and organic R groups work synergistically to form the complete SEI film, reducing the number of components and simplifying the electrolyte system.
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 electrolyte improves the rate performance and stability of the battery by forming a stable SEI film that copes with volume changes and prevents electron tunneling, thereby improving the battery's mechanical strength and reducing interface impedance.
Implementation Method 1
During a charging process of a battery, an electrolyte continuously undergoes reduction at a negative electrode
Implementation Method 2
the cyclic sulfate group contributes to the formation of an inorganic sulfite-based film between the electrolyte and a negative electrode plate
Implementation Method 3
further preventing electron tunneling, reducing interface impedance
Data Source
Figure 1~3
Figure 4~6
AI summary
This application provides an electrolyte, a secondary battery, and an electric apparatus. The electrolyte includes a cyclic sulfate compound represented by Formula I and a metal ion additive. The cyclic sulfate compound and the metal ion additive contribute to the formation of a stable SEI film, thereby facilitating an improvement in the rate performance of the battery.