Ionic Liquid Electrolyte for High-Energy Lithium Metal Batteries
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Solution Overview
Problem
Rechargeable lithium metal and lithium-ion batteries face challenges such as dendrite formation, thermal runaway, and low energy density due to flammable organic solvents and poor cathode material utilization, limiting their commercialization and safety.
Innovation Solution
A non-flammable, high-concentration ionic liquid-based electrolyte system with a lithium salt concentration greater than 3 M, combined with a solubility-promoting agent, is used to enhance lithium ion transport and prevent dendrite formation, while a meso-porous exfoliated graphite worm structure supports sulfur or lithium polysulfide cathodes to improve active material utilization and reduce the shuttle effect.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If flammable organic solvents (carbonate and ether families) are used in the electrolyte, then lithium ion transport is facilitated, but thermal runaway and safety issues occur
Solution Approach 1:
The patent changes the chemical composition parameter of the electrolyte from flammable organic solvents to non-flammable ionic liquids, specifically using imidazolium-based ionic liquids with lithium salts at concentrations greater than 3M. This parameter change maintains lithium ion transport capability while eliminating the flammability and thermal runaway issues associated with traditional organic solvents.
Solution Approach 2:
The patent employs a composite electrolyte system combining ionic liquid solvent with lithium salt (such as LiPF6, LiBF4, or LiClO4) at high concentrations. This composite material approach creates an electrolyte that exhibits both good ionic conductivity for lithium ion transport and inherent non-flammability, resolving the contradiction between transport speed and safety.
2Quantity of substance
If lithium metal anode is used, then high specific capacity (3,861 mAh/g) is achieved, but dendrite formation occurs leading to internal shorting
Solution Approach 1:
The patent changes the electrolyte concentration parameter to high lithium salt concentration (>3M) in ionic liquid, which modifies the solvation structure and reduces the tendency for dendrite formation. The high concentration electrolyte creates a more stable solid electrolyte interface (SEI) on the lithium metal anode, enabling safe operation while maintaining high specific capacity.
Solution Approach 2:
The ionic liquid-based high concentration electrolyte acts as an intermediary layer between the lithium metal anode and the external circuit. It mediates the lithium ion deposition process, promoting uniform plating and preventing dendrite formation, thus enabling reliable high-capacity lithium metal battery operation.
3Duration of action of stationary object
If conventional electrolyte systems are used, then battery operation is achieved, but cycling stability deteriorates due to dendrite formation
Solution Approach 1:
The patent applies parameter changes by using high concentration lithium salt (>3M) in ionic liquid electrolyte, which fundamentally alters the electrolyte's physical and chemical properties. This results in enhanced cycling stability through reduced dendrite formation, lower solvent decomposition, and improved electrode interface stability, enabling long-duration reliable battery operation.
Solution Approach 2:
The ionic liquid-based electrolyte creates an inert chemical environment that is resistant to decomposition and side reactions. This inert environment protects the electrode materials and maintains stable electrochemical performance over extended cycling, significantly improving cycling stability compared to conventional organic electrolyte systems.
4Object-affected harmful factors
If ionic liquid-based electrolyte with high lithium salt concentration is used, then safety and non-flammability are achieved, but viscosity increases potentially reducing ion transport
Solution Approach 1:
The patent optimizes the ionic liquid structure parameters (choosing imidazolium-based ionic liquids with appropriate alkyl chain lengths) and lithium salt concentration (>3M) to achieve a balance between viscosity and ionic conductivity. The selected ionic liquid-salt combination maintains relatively low viscosity while providing high safety and non-flammability, ensuring adequate ion transport speed.
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 achieves high specific energy density, long cycle life, and safety by facilitating lithium ion transport, reducing dendrite formation, and enhancing cathode active material utilization, resulting in cells with specific energies exceeding 600 Wh/Kg and stable cycling performance.
Implementation Method 1
the electrolyte contains a lithium salt dissolved in a first ionic liquid solvent with a salt concentration greater than 3 M (mole/liter)... facilitating lithium ion transport
Implementation Method 2
reducing dendrite formation... upon repeated charges and discharges, the lithium metal resulted in the formation of dendrites at the anode
Implementation Method 3
The carbonaceous material absorbs lithium (through intercalation of lithium ions or atoms between graphene planes, for instance) and desorbs lithium ions during the re-charge and discharge phases
Implementation Method 4
the electrolyte contains a lithium salt dissolved in a first ionic liquid solvent with a salt concentration greater than 3 M (mole/liter)
Data Source
AI summary
A rechargeable lithium metal or lithium-ion cell comprising a cathode having a cathode active material and/or a conductive supporting structure, an anode having an anode active material and/or a conductive supporting nano-structure, a porous separator electronically separating the anode and the cathode, a highly concentrated electrolyte in contact with the cathode active material and the anode active material, wherein the electrolyte contains a lithium salt dissolved in an ionic liquid solvent with a concentration greater than 3 M. The cell exhibits an exceptionally high specific energy, a relatively high power density, a long cycle life, and high safety with no flammability.