Multifunctional Electrolyte for High Voltage Lithium-Ion Batteries
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Solution Overview
Problem
Conventional lithium-ion battery electrolytes with carbonate solvents fail to meet safety and power density requirements, exhibit low voltage stability, and limit the materials that can be used due to chemical instability at the solid electrolyte interface, restricting the operational range and performance of lithium-ion batteries.
Innovation Solution
A multifunctional electrolyte comprising a solvent mixture of 10.0 wt. % to 35.0 wt. % carbonate-based solvent and 50.0 wt. % to 80.0 wt. % propionate-based solvent, 1.1M to 1.3M lithium salt, 0.1 wt. % to 12.0 wt. % phosphazene-based flame retardant, and 1,3,6-hexanetricarbonitrile and succinonitrile, along with 1.7 wt. % to 15.0 wt. % additives such as vinyl ethylene carbonate, propane sultone, and fluoroethylene carbonate, which enhances high voltage stability and safety across a wide temperature range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional carbonate-based electrolytes are used, then the battery can operate with traditional materials, but the voltage stability is low and safety requirements cannot be met
Solution Approach 1:
The patent changes the chemical composition parameters of the electrolyte by replacing conventional carbonate-based solvents with propionate-based solvents (ethyl propionate and propylene propionate) in specific concentration ranges (70-90 vol% and 10-30 vol% respectively). This parameter change achieves high voltage stability (enabling operation above 4.4V) while maintaining material compatibility through the formation of stable SEI layers.
Solution Approach 2:
The patent creates a composite electrolyte system by combining propionate-based solvents with specific additives including phosphazene-based flame retardants (0.1-10 wt%), nitrile-based additives (0.1-5 wt%), and other functional additives (1-15 wt%). This composite approach achieves both high voltage stability and improved safety properties while maintaining compatibility with battery materials.
2Power
If the battery voltage is increased to achieve higher energy density, then the power density improves, but the chemical stability at the electrolyte interface deteriorates
Solution Approach 1:
The patent applies preliminary action by using additive components (phosphazene-based flame retardants, nitrile-based additives, and other functional additives) that pre-form stable solid electrolyte interface (SEI) layers on the electrodes before high-voltage operation begins. This preliminary SEI formation protects the electrodes during subsequent high-voltage charging (above 4.4V), preventing direct harmful interactions between the electrolyte and electrode materials at elevated voltages.
3Device complexity
If traditional electrolyte compositions are used, then the formulation is simple, but the safety and operational temperature range are limited
Solution Approach 1:
The patent introduces intermediary substances that mediate between the electrolyte and electrode materials. Specifically, phosphazene-based flame retardants (0.1-10 wt%), nitrile-based additives (0.1-5 wt%), and other functional additives (1-15 wt%) act as intermediaries that form protective SEI layers, improving safety by preventing thermal runaway while extending the operational temperature range from -20°C to 85°C.
4Reliability
If the electrolyte is made more stable at high voltage, then the voltage stability improves, but the cyclability and lifetime may be affected
Solution Approach 1:
The patent optimizes the concentration parameters of multiple components to achieve both high voltage stability and long cyclability. The specific ranges used - propionate-based solvents (70-90 vol%), phosphazene-based flame retardants (0.1-10 wt%), nitrile-based additives (0.1-5 wt%), and other functional additives (1-15 wt%) - create a balanced electrolyte composition that forms stable SEI layers enabling operation above 4.4V while maintaining good cyclability over extended periods.
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 multifunctional electrolyte enables lithium-ion batteries to operate safely and stably over a wide temperature range, achieving high voltage stability up to 4.55V, improving energy and power density, and extending the battery's lifetime and cyclability.
Implementation Method 1
The solid electrolyte interface (SEI) formed at the interfaces promotes chemical compatibility. The formation and properties of the SEI depend on both the electrolyte and the active materials used.
Implementation Method 2
0.1 wt. % to 12.0 wt. % of a phosphazene-based flame retardant
Implementation Method 3
1,3,6-hexanetricarbonitrile and succinonitrile together in a range of 0.1 wt. % to 5.0 wt. %
Data Source
AI summary
An electrolyte for a rechargeable lithium-ion battery includes a solvent consisting of 10.0 wt. % to 35.0 wt. % carbonate-based solvent and 50.0 wt. % to 80.0 wt. % propionate-based solvent, 1.1M to 1.3M lithium salt, 0.1 wt. % to 12.0 wt. % of a phosphazene-based flame retardant, 1,3,6-hexanetricarbonitrile and succinonitrile together in a range of 0.1 wt. % to 5.0 wt. %, and 1.7 wt. % to 15.0 wt. % additives.