Battery Electrolyte Additives for Layered SEI and Low Impedance
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Solution Overview
Problem
Existing lithium-ion batteries face safety issues due to flammable organic solvents, leading to thermal shock failures and reduced performance, and current additives compromise impedance, fast-charging, and cycle life.
Innovation Solution
An electrolyte solution forming a 'hamburger-like' layered SEI film with specific additives to inhibit interface reactions, enhance ionic conductivity, and generate polymers to cover short-circuit points, improving thermal stability and safety.
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 introduces a fluorinated cyclic carbonate additive as an intermediary substance that mediates between safety requirements and performance maintenance. This additive forms a stable SEI film that acts as a protective interface, preventing direct contact between the electrolyte and electrode while maintaining ionic conductivity, thus achieving both safety improvement and impedance control
Solution Approach 2:
The patent modifies the chemical composition parameters of the electrolyte by incorporating fluorinated cyclic carbonate with specific molecular structure characteristics. This parameter change enables the formation of SEI films with different physical and chemical properties compared to conventional additives, achieving lower impedance and better fast-charging performance while maintaining safety
2Reliability
If conventional carbonate-based organic solvent system is used, then ionic conductivity is maintained, but flash point is low and flammability increases
Solution Approach 1:
The patent creates a composite electrolyte system by combining fluorinated cyclic carbonate additive with conventional carbonate solvents. This composite approach leverages the high ionic conductivity of carbonate solvents while the fluorinated additive contributes flame-retardant properties and forms protective SEI films, achieving both conductivity maintenance and flammability reduction
3Duration of action of stationary object
If interface film stability is improved to reduce impedance, then long-time cycling performance is enhanced, but interface side reactions increase without proper additives
Solution Approach 1:
The fluorinated cyclic carbonate additive performs preliminary action by preferentially reacting with electrode surfaces during initial cycles to form a stable SEI film. This preliminary film formation prevents subsequent interface side reactions and maintains film stability throughout long-term cycling, thereby enhancing both safety and performance durability
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 reduces impedance, enhances long-time cycling stability, and ensures high safety performance by stabilizing the interface film and preventing short circuits.
Implementation Method 1
the electrolyte solution of the present disclosure can form an SEI film with a 'hamburger-like' layered structure
Implementation Method 2
This SEI film can inhibit an interface side reaction
Implementation Method 3
easily generate a polymer that can cover an active material and a short-circuit point under a thermal shock condition
Implementation Method 4
improve stability and ionic conductivity of the interface film, reduce an increase in interface film impedance
Implementation Method 5
improve stability and ionic conductivity of the interface film
Data Source
AI summary
A electrolyte solution includes a first additive having a structure represented by formula (I) and a second additive having a structure represented by formula (II): where R1, R2, R3 each are independently selected fromand R4, R5, and R6 each are independently selected from a C1-C10 alkyl group, a C2-C10 alkenyl group, or a C1-C10 alkoxy group; and X is selected from hydrogen, halogen, the C1-C10 alkyl group, the C2-C10 alkenyl group, a C2-C10 alkynyl group, or a C1-C4 cyano group, and n is 1, 2, 3, or 4.