Carbonate Electrolyte Binding Lithium Salts for Battery Efficiency
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Solution Overview
Problem
Lithium metal batteries face performance degradation and premature failure due to side reactions between lithium metal and electrolyte species, compromising coulombic efficiency and cycling lifetime.
Innovation Solution
A highly-concentrated carbonate-based electrolyte system with a bound moiety of lithium bis(fluorosulfonyl)imide or similar salts bound to dimethyl carbonate or dimethyl dicarbonate, achieving a concentration of greater than 4M and a molar ratio of 0.5 to 1, which suppresses unbound species and enhances electrochemical cell efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If lithium metal is used as the negative electrode to achieve high energy density, then the theoretical capacity and electrochemical potential are improved, but side reactions with electrolyte species occur causing performance degradation and premature failure
Solution Approach 1:
A novel electrolyte composition is introduced as an intermediary between lithium metal and conventional electrolyte species. This electrolyte contains specific additives that form protective interfacial layers, mediating the interaction to prevent direct harmful reactions while maintaining ionic conductivity, thus preserving both high energy density and cycling lifetime
Solution Approach 2:
The electrolyte composition parameters are optimized by adjusting the ratios of carbonate solvents, lithium salts, and protective additives. By changing concentration parameters and chemical composition, the electrolyte achieves optimal properties that suppress side reactions while maintaining high lithium ion mobility for sustained performance
2Device complexity
If conventional electrolyte compositions are used with lithium metal anodes, then the battery structure is simple, but side reactions promote performance degradation compromising coulombic efficiency
Solution Approach 1:
Protective additives in the electrolyte act as intermediaries that preferentially react with lithium metal to form stable solid electrolyte interphase (SEI) layers. These intermediary layers prevent direct contact between conventional electrolyte species and lithium, eliminating parasitic side reactions and improving coulombic efficiency while maintaining relatively simple battery architecture
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 system significantly reduces side reactions, improving the energy density to over 900 Wh/L and maintaining high cycle efficiency, thereby extending the lifespan and performance of lithium-ion batteries.
Implementation Method 1
The electrolyte system includes a bound moiety including one or more salts associated with and/or bound to an carbonate-based solvent
Data Source
AI summary
A highly-concentrated electrolyte system for an electrochemical cell is provided, along with methods of making the electrolyte system. The electrolyte system includes a bound moiety having an ionization potential greater than an electron affinity and comprising one or more salts selected from the group consisting of: lithium bis(fluorosulfonyl)imide, sodium bis(fluorosulfonyl)imide, potassium bis(fluorosulfonyl)imide, and combinations thereof bound to a solvent comprising one or more solvents selected from the group consisting of: dimethyl carbonate, dimethyl dicarbonate, and combinations thereof. The salts have a concentration in the electrolyte system of greater than or equal to about 4 M. A molar ratio of the salts to the dimethyl carbonate is about 0.5. A molar ratio of the salts to the dimethyl dicarbonate is about 1. The salts binds to the dimethyl carbonate and/or dimethyl dicarbonate causing the electrolyte system to be substantially free of unbound dimethyl carbonate, unbound dimethyl dicarbonate, and unbound bis(fluorosulfonyl)imide.