Battery Electrolyte Composition for High-Voltage Stability and Fast Kinetics
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Solution Overview
Problem
The challenge lies in balancing the high-voltage and high-temperature stability with room-temperature kinetic performance of lithium-ion batteries, particularly in high-voltage lithium cobaltate systems, where electrolytes with good kinetic performance exhibit poor oxidation resistance, leading to issues like gas generation, lithium precipitation, and increased impedance.
Innovation Solution
An electrochemical apparatus with a tailored electrolyte composition comprising propylene carbonate, ethylene carbonate, and a nitrile additive, along with controlled viscosity, to enhance stability and kinetic performance. The electrolyte includes specific mass percentages of these components, ranging from 4% to 26% for propylene carbonate, 14% to 46% for ethylene carbonate, and 2.8% to 8.5% for the nitrile additive, with a viscosity of less than 5.8 mPa·s at 25°C, to achieve a synergistic effect.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If electrolyte with good kinetic performance is used, then room-temperature kinetic performance is improved, but oxidation resistance deteriorates
Solution Approach 1:
The patent uses a composite electrolyte system combining multiple carbonate solvents (EC, PC, DEC, DMC) with specific ratios, creating a synergistic mixture that achieves both good kinetic performance and oxidation resistance. The composite formulation allows each component to contribute different properties: EC provides high dielectric constant for lithium salt dissolution, while PC and linear carbonates provide low viscosity for ion mobility, and the combination exhibits enhanced oxidation stability compared to individual components.
Solution Approach 2:
The patent optimizes the viscosity parameter of the electrolyte to less than 5.8 mPa·s at 25°C by adjusting the ratios of different carbonate solvents. This parameter control enables the electrolyte to maintain low resistance and high ionic conductivity at room temperature while the specific composition provides adequate oxidation resistance for high-voltage applications.
2Use of energy by moving object
If high-voltage system is used, then energy storage density is improved, but stability at high temperature deteriorates
Solution Approach 1:
The patent employs a composite electrolyte formulation with multiple carbonate components in specific proportions (EC: 14-46%, PC: 4-26%, DEC: 16-40%, DMC: 10-35%) that provides both high-voltage compatibility and high-temperature stability. The synergistic interaction among components creates an electrolyte system that can withstand high operating temperatures while supporting high-voltage lithium cobaltate cathodes for enhanced energy density.
Solution Approach 2:
The patent controls the viscosity parameter within a specific range (less than 5.8 mPa·s at 25°C) through compositional adjustment, which maintains good ionic conductivity at room temperature while the specific composition provides thermal stability for high-temperature operation. This parameter optimization enables the electrolyte to function reliably across a wide temperature range in high-voltage systems.
3Power
If high-voltage lithium cobaltate system is used, then open-circuit voltage is improved, but lithium precipitation increases
Solution Approach 1:
The patent optimizes the viscosity parameter to less than 5.8 mPa·s at 25°C by adjusting the ratio of linear carbonates (DEC and DMC) which have lower viscosity compared to cyclic carbonates. This low viscosity reduces the resistance to lithium ion transport, enabling smooth ion flux during charging and discharging at high voltage, thereby preventing lithium precipitation on the electrode surfaces while maintaining high open-circuit voltage.
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 composition improves both high-voltage and high-temperature stability while enhancing room-temperature kinetic performance by reducing gas generation, lithium precipitation, and impedance, thus resolving the stability-kinetic performance contradiction.
Implementation Method 1
Controlling the mass percentages of the propylene carbonate, ethylene carbonate, and nitrile additive, as well as the viscosity of the electrolyte at 25° C. within the foregoing ranges is conducive to formation of a synergistic effect between the various components in the electrolyte
Implementation Method 2
For high-voltage systems, electrolyte is required to be highly resistant to oxidation
Implementation Method 3
enhance the room-temperature kinetic performance of the electrochemical apparatus
Data Source
AI summary
An electrochemical apparatus includes a positive electrode, a negative electrode, and an electrolyte, where the electrolyte includes propylene carbonate, ethylene carbonate, and a nitrile additive. Based on a mass of the electrolyte, a mass percentage of the propylene carbonate is 4% to 26%, a mass percentage of the ethylene carbonate is 14% to 46%, and a mass percentage of the nitrile additive is 2.8% to 8.5%. A viscosity of the electrolyte at 25° C. is less than or equal to 5.8 mPa·s. By coordinately controlling the adding percentages of the propylene carbonate, ethylene carbonate, and nitrile additive, as well as the viscosity of the electrolyte, the contradiction between high-voltage and high-temperature stability and room-temperature kinetic performance of the electrochemical apparatus can be resolved.