Battery Electrolyte Composition Using High-Flash-Point Diluent
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Solution Overview
Problem
Current lithium ion and lithium metal batteries face challenges with the flammability of state-of-the-art liquid electrolytes, which poses a safety hazard and limits cycling stability and long cycle life due to the use of flammable organic carbonate solvents.
Innovation Solution
Development of electrolytes comprising a lithium salt, a nonaqueous solvent with a flame retardant, and a diluent with a flash point greater than 90°C, where the lithium salt has reduced solubility in the diluent compared to the solvent, creating a localized high concentration electrolyte structure that enhances safety and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If flammable organic carbonate solvents are used in electrolytes, then high ion conductivity and electrochemical performance are achieved, but safety deteriorates due to high flammability
Solution Approach 1:
The patent introduces a diluent as an intermediary substance that does not solvate lithium ions but mixes with the nonaqueous solvent to create a localized high concentration electrolyte structure. This diluent enables the use of flame retardant solvents while maintaining ion conductivity through the localized concentrated regions, thereby resolving the contradiction between safety and flammability.
Solution Approach 2:
The patent creates localized high concentration regions of lithium salt and nonaqueous solvent within the electrolyte system. These localized concentrated regions provide high ion conductivity and electrochemical performance, while the surrounding diluent provides flame retardancy and safety. This local quality differentiation resolves the contradiction between flammability and performance.
2Duration of action of stationary object
If conventional liquid electrolytes are used, then good electrochemical performance is achieved, but cycling stability deteriorates due to flammability-related degradation
Solution Approach 1:
The diluent acts as a mediator that stabilizes the electrolyte system by providing a non-flammable environment while allowing localized high concentration regions to maintain electrochemical performance. This intermediary role improves cycling stability without sacrificing cycle life, resolving the contradiction between these two reliability aspects.
3Object-affected harmful factors
If flame retardant solvents are used to improve safety, then flash point increases, but ion conductivity deteriorates due to reduced lithium salt solubility
Solution Approach 1:
The patent creates localized high concentration regions where lithium salt and nonaqueous solvent are concentrated, providing high ion conductivity. The bulk electrolyte contains diluent that provides high flash point and flame retardancy. This spatial differentiation of properties resolves the contradiction between flash point and ion conductivity.
Solution Approach 2:
The electrolyte is formulated as a composite system combining flame retardant nonaqueous solvent, lithium salt, and diluent in specific ratios. This composite structure integrates the flame retardancy of the solvent with the ion conductivity enabled by localized concentration, resolving the contradiction between flash point and ion conductivity.
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 proposed electrolytes exhibit improved safety with elevated flash points, maintaining high cycling stability and capacity retention, while promoting effective solid electrolyte interphase formation, thus enhancing the performance and safety of lithium ion and lithium metal batteries.
Implementation Method 1
a nonaqueous solvent comprising a flame retardant, wherein the lithium salt is soluble in the solvent... a diluent having a flash point greater than 90° C., wherein the lithium salt has a solubility in the diluent at least 10 times less than a solubility of the lithium salt in the nonaqueous solvent
Data Source
AI summary
Electrolytes for lithium ion and lithium metal batteries include (i) a lithium salt, (ii) a nonaqueous solvent comprising a flame retardant, wherein the lithium salt is soluble in the solvent, and (iii) a diluent having a flash point greater than 90° C., wherein the lithium salt has a solubility in the diluent at least 10 times less than a solubility of the lithium salt in the nonaqueous solvent. The electrolyte may further include an additive having a different composition than the lithium salt, a different composition than the nonaqueous solvent, and a different composition than the diluent.