Multi-functional Electrolyte for Internal Battery Thermal Management
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Solution Overview
Problem
Lithium-ion batteries face thermal management challenges due to their low thermal conductivity, leading to high temperature gradients and potential thermal runaway, which existing external thermal management systems are unable to effectively address, especially in large battery packs.
Innovation Solution
A multi-functional electrolyte (MFE) is integrated within the battery cells, comprising a lithium salt, an organic electrolyte, and a volatile fluorinated hydrocarbon, which evaporates to absorb thermal energy, condenses, and recycles, providing internal passive thermal management by creating a loop heat pipe architecture to regulate temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If external liquid cooling systems are used to manage battery temperature, then thermal management capability is improved, but system weight and volume increase significantly
Solution Approach 1:
The patent combines the thermal management function with the battery cell structure itself by integrating heat pipe channels directly into the electrode stack. The electrolyte serves dual purposes as both ionic conductor and heat transfer medium, eliminating the need for separate external cooling systems and their associated weight and volume.
Solution Approach 2:
The heat pipe channels are nested within the electrode stack structure, with vaporization channels formed in the positive electrode and condensation channels in the negative electrode. This nested arrangement allows the thermal management system to occupy minimal space within the battery cell while providing effective heat removal.
2Temperature
If external thermal management systems are used, then heat removal capability is improved, but the systems cannot directly manage internal cell temperature and require significant optimization
Solution Approach 1:
The battery cell performs its own thermal management through passive heat pipe mechanisms. The electrolyte automatically vaporizes in hot regions, transports heat to cooler regions where it condenses, and returns to the vaporization zone, creating a self-sustaining thermal regulation cycle without external control systems.
Solution Approach 2:
The patent replaces active mechanical cooling systems with passive heat pipe technology that utilizes phase change mechanisms. The heat transfer is driven by natural convection and phase change thermodynamics rather than pumps, valves, or control electronics, significantly reducing system complexity.
3Temperature
If a volatile co-solvent is added to enable internal evaporation cooling, then thermal management effectiveness is improved, but electrolyte composition complexity increases
Solution Approach 1:
The electrolyte composition is designed to serve multiple functions simultaneously: the volatile co-solvent enables heat absorption through vaporization, the base electrolyte maintains ionic conductivity for battery operation, and the mixture ensures proper freezing and boiling points for thermal management. This multi-functional design eliminates the need for separate cooling systems.
Solution Approach 2:
The patent modifies electrolyte parameters by incorporating volatile co-solvents with specific boiling points below the thermal runaway temperature. This parameter change enables the electrolyte to undergo phase change at controlled temperatures, providing passive thermal management while maintaining electrochemical functionality.
4Device complexity
If passive evaporation cooling is implemented, then system simplicity is improved, but heat removal efficiency depends on achieving sufficient vapor pressure
Solution Approach 1:
The patent utilizes phase transitions of the electrolyte (vaporization and condensation) as the core heat transfer mechanism. The volatile co-solvent vaporizes in hot regions absorbing latent heat, the vapor travels to cooler regions where it condenses releasing heat, and the liquid returns to repeat the cycle, providing efficient passive heat removal.
Solution Approach 2:
The heat pipe mechanism employs vapor pressure gradients to drive heat transfer. Vapor generated in hot zones flows through pressure gradients to condensation zones, and the liquid return is driven by capillary forces and gravity, creating an autonomous thermal management system without mechanical pumps.
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 internal thermal management system effectively cools the battery cells by absorbing and rejecting heat, reducing the risk of thermal runaway and improving the efficiency of thermal management within large battery packs, while minimizing the weight and volume of the cooling system.
Implementation Method 1
the fluorinated hydrocarbon phase-changes to a vapor by absorbing thermal energy
Implementation Method 2
the fluorinated hydrocarbon vapor phase-changes to a liquid-phase by condensing in the condenser
Implementation Method 3
The liquid-vapor phase change process absorbs a significant amount of energy per unit mass of volatile co-solvent evaporated
Implementation Method 4
The vapor generated is transported to the skin of the cell, where it is condensed and transported back to the internal portion of the cell via surface tension forces
Implementation Method 5
The vapor generated is transported to the skin of the cell, where it is condensed and transported back to the internal portion of the cell via surface tension forces
Data Source
AI summary
The high thermal conduction resistances of a lithium-ion battery (LIB) severely limit the effectiveness of a conventional external thermal management system (TMS). A method for a new thermal management system for lithium-ion batteries that utilizes a multi-functional electrolyte (MFE) to remove heat locally inside the cell by evaporating a volatile component of the MFE is disclosed. These new electrolyte mixtures comprise a high vapor pressure co-solvent. The characteristics of a previously unstudied high vapor pressure co-solvent HFE-7000 (65 kPa at 25° C.) in an MFE (1 M LiTFSI in 1:1 HFE-7000/EMC), and other possible MFE compositions that can be utilized in a custom electrolyte boiling facility, are disclosed.