Lithium Battery Electrolyte for Wide Temperature Operation
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Solution Overview
Problem
Lithium batteries, particularly those with LiFePO4 and lithiated titanium oxide active materials, face challenges in maintaining high power delivery and low self-discharge rates across a wide temperature range, especially at extreme temperatures.
Innovation Solution
A liquid electrolyte comprising a mixture of 33% to 49% propylene carbonate, 33% to 49% diethyl carbonate, and 2% to 34% ethyl acetate, which dissolves a lithium salt, is used to enhance the performance of lithium batteries, allowing them to operate effectively at various temperatures with low self-discharge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If standard electrolyte mixtures are used, then the battery operates at moderate temperatures, but the power delivery and self-discharge control deteriorate at extreme temperatures
Solution Approach 1:
The patent modifies the electrolyte composition parameters by replacing traditional EC/DMC/DEC mixtures with a specific PC/DEC/EA formulation. The volume ratios are precisely controlled (33-49% PC, 33-49% DEC, 2-34% EA) to optimize performance across extreme temperatures. This parameter change enables the electrolyte to maintain appropriate viscosity and conductivity at both low and high temperatures, resolving the contradiction between temperature range and reliability.
Solution Approach 2:
The patent creates a composite electrolyte system by combining three specific solvents (propylene carbonate, diethyl carbonate, and ethyl acetate) in defined proportions. This composite formulation leverages the complementary properties of each component: PC provides high dielectric constant for lithium salt dissolution, DEC offers low viscosity for ion mobility, and EA contributes to stability at extreme temperatures. The synergistic combination resolves the contradiction by achieving reliable performance across the full temperature range.
2Power
If high power delivery is achieved at high current regimes, then the battery provides sufficient power, but self-discharge rates increase
Solution Approach 1:
The patent adjusts the electrolyte composition parameters to balance power delivery and self-discharge control. The specific inclusion of ethyl acetate (2-34% by volume) in addition to the PC/DEC base mixture modifies the electrolyte's electrochemical stability window and reduces parasitic reactions at the electrodes. This parameter optimization allows the system to maintain low self-discharge rates even when operating at high current regimes for power delivery.
3Quantity of substance
If traditional carbonate mixtures (EC/DMC/DEC) are used, then the electrolyte dissolves lithium salts effectively, but the performance at extreme temperatures is insufficient
Solution Approach 1:
The patent changes the electrolyte composition parameters by substituting ethylene carbonate (EC) with propylene carbonate (PC) and adding ethyl acetate (EA) to the traditional DMC/DEC mixture. PC maintains high dielectric constant for effective lithium salt dissolution while offering improved thermal stability. EA addition further enhances temperature range performance by modifying the electrolyte's viscosity-temperature relationship. This parameter change resolves the contradiction between salt dissolution capability and extreme temperature performance.
Solution Approach 2:
The patent develops a composite electrolyte formulation combining PC, DEC, and EA in specific proportions. This composite material integrates the high dielectric constant property of PC for lithium salt dissolution with the low viscosity and broad temperature stability of DEC and EA. The synergistic composite formulation achieves both effective salt dissolution and superior extreme temperature performance, resolving the identified contradiction.
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
This electrolyte combination enables lithium batteries to deliver high power at high current regimes while maintaining low self-discharge over a wide temperature range, including extremely low and high temperatures, comparable to standard electrolytes.
Implementation Method 1
a liquid electrolyte for a lithium battery comprising at least one lithium salt dissolved in a mixture of three non-aqueous organic solvents
Implementation Method 2
the liquid electrolyte generally comprises a lithium salt dissolved in one or more non-aqueous organic solvents
Data Source
AI summary
The invention relates to a liquid electrolyte for a lithium accumulator, including at least one lithium salt dissolved in a mixture of three non-aqueous organic solvents. The mixture comprises: 33 to 49 vol. % of propylene carbonate; 33 to 49 vol. % of diethyl carbonate; and 2 to 34 vol. % of ethyl acetate. The liquid electrolyte is particularly adapted for a lithium accumulator based on the pair LiFePO4/Li4Ti5O12 or derivatives thereof, said materials being the respective active materials of the positive and negative electrodes. Such a lithium accumulator in fact has the advantage of power operation in a wide temperature range while maintaining a low self-discharge capacity.