Cell Stack Thermal Shielding and Collector Cooling for Ester Electrolytes
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Solution Overview
Problem
Power storage devices using liquid electrolytes with ester compounds are susceptible to temperature fluctuations in high-temperature environments, leading to increased diffusion resistance of charge carriers due to volatility issues.
Innovation Solution
A power storage device configuration that includes a cell stack with a liquid electrolyte containing an ester compound, where the cell stack is covered with a plastic covering portion and terminal current collectors made of high thermal conductivity materials, along with a cooling unit to manage heat transfer and prevent excessive temperature rise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a liquid electrolyte containing an ester compound is used to reduce viscosity and suppress diffusion resistance of charge carriers, then the energy density and charge carrier diffusion efficiency are improved, but the device becomes susceptible to heat of outside air in high-temperature environments due to the low boiling point and volatility of the ester compound
Solution Approach 1:
The patent introduces a covering portion made of plastic as an intermediary barrier between the liquid electrolyte containing ester compound and the outside air. This covering portion prevents direct contact between the volatile ester compound and the external environment, thereby reducing the harmful effect of heat-induced volatility while maintaining the electrolyte's functional benefits for charge carrier diffusion
Solution Approach 2:
The patent converts the harmful volatility of the ester compound at high temperatures into a beneficial controlled evaporation process. By allowing controlled evaporation within the sealed covering portion and using the evaporated ester compound to form a protective film on the electrode surfaces, the harmful volatility is transformed into a beneficial effect that stabilizes the electrode-electrolyte interface
2Quantity of substance
If the weight per unit area of active material layer is increased to increase energy density, then the energy density is improved, but the diffusion resistance of charge carriers in the active material layer is increased
Solution Approach 1:
The patent changes the physical parameter of the electrolyte by using an ester compound with specific viscosity-reducing properties. This parameter change (lower viscosity) compensates for the increased diffusion resistance caused by higher active material layer weight, allowing charge carriers to move more easily through the denser active material by reducing resistance at the electrolyte interface
Solution Approach 2:
The patent employs a composite electrolyte system combining ester compound with other components to create a multi-functional electrolyte that simultaneously provides low viscosity for reduced diffusion resistance and appropriate ionic conductivity. This composite approach allows the system to handle both the high energy density requirement and the charge carrier diffusion efficiency requirement
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 configuration reduces the impact of high-temperature environments on the power storage device, maintaining efficient charge carrier diffusion and extending the device's operational stability.
Implementation Method 1
At least one of the terminal current collectors is made of a high thermal conductivity material having a thermal conductivity greater than or equal to 100 W/(m·K). The power storage device includes a cooling unit that cools the terminal current collector made of the high thermal conductivity material.
Implementation Method 2
the diffusion resistance of charge carriers such as lithium ions in the active material layer is increased. The inventors of the present invention have found that using a liquid electrolyte containing an ester compound to reduce viscosity suppresses the diffusion resistance of charge carriers in an active material layer.
Implementation Method 3
A side surface of the cell stack with respect to a stacking direction is covered with a covering portion made of a plastic.
Data Source
AI summary
A power storage device includes power storage cells that includes a positive electrode, a negative electrode, a separator, and an accommodation chamber accommodating a liquid electrolyte in a liquid-tight manner. The power storage device includes a cell stack in which the power storage cells are stacked in series. A side surface of the cell stack is covered with a seal portion made of a plastic. A terminal positive electrode current collector and a terminal negative electrode current collector located in the outermost layer of the cell stack are made of a high thermal conductivity material having a thermal conductivity greater than or equal to 100 W/(m·K). The power storage device includes a positive electrode cooling unit, which cools the terminal positive electrode current collector, and a negative electrode cooling unit, which cools the terminal negative electrode current collector. The liquid electrolyte contains an ester compound.