Localized Superconcentrated Electrolyte for Low Flammability
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Solution Overview
Problem
Conventional superconcentrated electrolytes used in electrochemical devices are flammable, leading to safety risks, and suffer from high cost, high viscosity, and poor wetting issues, while fire-retarded solvents often react with lithium metal or fail to form a stable solid electrolyte interphase (SEI) layer on anodes.
Innovation Solution
Development of low flammability and nonflammable localized superconcentrated electrolytes (LSEs) comprising an active salt, a solvent with a flame retardant compound, and a diluent where the active salt is soluble in the solvent but poorly soluble in the diluent, forming a stable SEI layer enriched in inorganic components like LiF, Li2CO3, and Li2O, enhancing anode stability and cycling performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional superconcentrated electrolytes are used, then high salt concentration is achieved, but flammability increases and safety risks arise
Solution Approach 1:
The patent changes the chemical composition parameters of the electrolyte by introducing fluorinated carbonates with specific molecular structures (FEC, DFEC, TFEC) and controlling their concentration ratios. This parameter change achieves both high salt concentration compatibility and reduced flammability, resolving the contradiction between quantity of substance and harmful factors
Solution Approach 2:
The patent creates a composite electrolyte system combining fluorinated cyclic carbonates, linear carbonates, and lithium salts. This composite material approach allows the electrolyte to simultaneously achieve high ion conductivity, reduced flammability, and stable SEI formation, addressing both the high concentration requirement and safety concerns
2Object-affected harmful factors
If fire-retarded solvents are used, then flammability is reduced, but reactivity with lithium metal increases and SEI stability decreases
Solution Approach 1:
The patent applies local quality by creating a specialized SEI layer through fluorinated carbonate additives that specifically protect the lithium metal surface. The fluorinated compounds concentrate at the electrode interface to form a stable, low-flammability SEI layer, while the bulk electrolyte maintains good ionic conductivity. This localized action resolves the contradiction between flammability reduction and SEI stability
Solution Approach 2:
The fluorinated cyclic carbonates act as intermediary substances that mediate between the lithium metal and the bulk electrolyte. They form a protective interface layer that prevents direct contact between lithium and flammable components, while also providing stable SEI formation. This intermediary approach simultaneously reduces flammability and enhances reliability
3Quantity of substance
If high concentration electrolytes are used, then salt solubility is improved, but viscosity increases and wetting performance deteriorates
Solution Approach 1:
The patent employs a composite solvent system combining fluorinated cyclic carbonates (high dielectric constant for salt dissolution) with linear carbonates (low viscosity for good wetting). This composite approach allows the electrolyte to maintain high salt concentration while preserving excellent wetting performance and low viscosity, resolving the contradiction between quantity of substance and ease of operation
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 LSEs provide enhanced cycling stability and coulombic efficiency comparable to flammable electrolytes, with reduced flammability and viscosity, and improved wetting properties, while maintaining or exceeding the performance of conventional electrolytes, making them suitable for carbon- and silicon-based anodes.
Implementation Method 1
a solvent comprising (i) a flame retardant compound and (ii) a cosolvent... wherein the active salt is soluble in the solvent
Implementation Method 2
forming a stable solid electrolyte interphase (SEI) layer (that is enriched in inorganic components such as LiF, Li2CO3, Li2SOx, Li2O, LiNOx, etc. derived from decomposition of the active salt in the electrolyte)
Implementation Method 3
a diluent in which the active salt is insoluble or poorly soluble... the active salt has a solubility in the diluent at least 10 times less than a solubility of the active salt in the solvent
Data Source
AI summary
Low flammability and nonflammable localized superconcentrated electrolytes (LSEs) for stable operation of lithium and sodium ion batteries are disclosed. Electrochemical devices including the low flammability and nonflammable LSEs are also disclosed. The low flammability and nonflammable LSEs include an active salt, a solvent comprising a flame retardant compound, wherein the active salt is soluble in the solvent, and a diluent in which the active salt is insoluble or poorly soluble. The LSE may further include a cosolvent, such as a carbonate, a sulfone, a sulfite, a sulfate, a carboxylate, an ether, a nitrogen-containing solvent, or any combination thereof. In certain embodiments, such as when the solvent and diluent are immiscible, the LSE further includes a bridge solvent.