Electrolyte Additives for Stable SEI Film Formation
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Solution Overview
Problem
Existing lithium-ion batteries face safety issues due to flammability and increased impedance, leading to defects such as reduced fast-charging performance and cycle life, necessitating improved thermal shock and cycling stability.
Innovation Solution
An electrolyte solution with specific additives forming a 'hamburger-like' layered SEI film to inhibit interface reactions, enhance ionic conductivity, and generate a polymer to cover short-circuit points, thereby improving structural and thermal stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If flame-retardant additives are added to improve thermal shock performance, then safety performance is improved, but system impedance increases and fast-charging performance deteriorates
Solution Approach 1:
The patent changes the chemical composition parameters of the electrolyte by introducing a specific fluorinated cyclic carbonate additive with unique molecular structure (formula I), which has different electrochemical properties from conventional additives. This parameter change enables the formation of an interface film with superior ionic conductivity while maintaining flame retardancy, thus reducing system impedance compared to traditional flame-retardant additives
Solution Approach 2:
The patent creates a composite interface film structure on the electrode surface through the fluorinated cyclic carbonate additive, combining multiple functional components (fluorinated cyclic carbonate decomposition products, lithium fluoride, and other electrolyte components) into a layered composite structure. This composite film simultaneously provides flame retardancy, low impedance, and high ionic conductivity, resolving the contradiction between safety and fast-charging performance
2Use of energy by moving object
If conventional carbonate-based organic solvent system is used, then high energy density is achieved, but flash point is low and flammability increases
Solution Approach 1:
The fluorinated cyclic carbonate additive acts as an intermediary substance that mediates between the electrode and the carbonate-based organic solvent. It forms a protective interface film that prevents direct contact and harmful reactions between the electrode and flammable carbonate solvents, while still allowing ionic transport. This intermediary layer enables the use of high-energy-density carbonate solvents without their associated flammability risks
Solution Approach 2:
The patent converts the potential harm of flammable carbonate solvents into a benefit by using the fluorinated cyclic carbonate additive to control and manage the flammability risk. The additive decomposes first to form a protective film, preventing the carbonate solvents from coming into contact with electrodes and potential ignition sources. Thus, the harmful flammability characteristic is converted into a controlled safety feature while maintaining high energy density
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 solution reduces impedance, enhances safety performance, and ensures stable long-time cycling by forming a stable interface film with improved ionic conductivity and thermal stability.
Implementation Method 1
The electrolyte solution of the present disclosure can form an SEI film with a 'hamburger-like' layered structure. This SEI film can inhibit an interface side reaction, improve stability and ionic conductivity of the interface film
Implementation Method 2
easily generate a polymer that can cover an active material and a short-circuit point under a thermal shock condition
Data Source
AI summary
The present disclosure relates to the technical field of batteries, in particlular to an eclectroyte and a battery comprising the electrolyte. The electrolyte comprises a first additive having a structure as represented by formula (I) and a second additive having a structure represented by formula (II), where R1, R2, and R3 are each independently selected from formula (a), formula (b), formula (c), and formula (d); R4, R5, and R6 are each independently selected from C1-C10 alkyl, C2-C10 alkenyl, and C1-C10 alkoxy; X is selected from hydrogen, halogen, C1-C10 alkyl, C2-C10 alkenyl, C2-C10 alkynyl, C1-C4 cyano; and n is 1, 2, 3, or 4. A SEI film formed by the electrolyte of the present disclosure can improve the stability and the ionic conductivity of an interface film, and has higher safety. The battery of the present disclosure has higher safety performance and more stable long cycle performance.