Cell Stack Cooling Through High-Conductivity Terminal Collectors
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Solution Overview
Problem
Power storage devices using liquid electrolytes with oxalate compounds experience excessive temperature rises due to exothermic reactions, particularly in high-temperature environments, which can lead to further temperature increases and reduced device lifespan.
Innovation Solution
A power storage device configuration with a cell stack covered by 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 rises. The covering portion is made of low-density polyethylene to allow carbon dioxide gas permeation, reducing internal pressure and temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If a liquid electrolyte containing an oxalate compound is used to extend power storage device life, then the lifespan is improved, but temperature increases due to exothermic reactions between the electrolyte and the coating on the negative electrode active material
Solution Approach 1:
The harmful exothermic reaction between the oxalate compound and the coating on the negative electrode is extracted and isolated by introducing a cooling unit that removes heat from the system, separating the beneficial lifespan-extending function from the harmful temperature-increasing side effect
Solution Approach 2:
A cooling unit is introduced as an intermediary component between the electrochemical reactions and the surrounding environment, mediating the heat transfer to prevent excessive temperature rise while allowing the oxalate compound to continue functioning in extending device lifespan
2Power
If multiple power storage cells are stacked in series to form a cell stack, then the power output is improved, but the accommodation chamber becomes narrow and contact portion of liquid electrolyte with negative electrode surface increases, accelerating temperature increase
Solution Approach 1:
The cell stack is segmented into multiple individually produced power storage cells, each with its own cooling capability, allowing heat management to be distributed and controlled at each segment rather than as a single large mass
Solution Approach 2:
A cooling unit is introduced as an intermediary heat removal system that compensates for the increased electrolyte-negative electrode contact area, mediating the thermal balance to prevent excessive temperature rise despite the narrow accommodation chamber
3Temperature
If the temperature of the power storage device reaches high temperature of 180°C or higher, then the exothermic reaction occurs between liquid electrolyte and coating, but this causes further temperature increase that reduces device lifespan
Solution Approach 1:
The cooling unit applies preliminary anti-action by continuously removing heat before the temperature can reach the critical 180°C threshold, preventing the exothermic reaction from occurring in the first place rather than attempting to mitigate it after it starts
Solution Approach 2:
The cooling system provides negative feedback by monitoring and responding to temperature increases, automatically adjusting heat removal to maintain temperature within safe operating limits and prevent the runaway exothermic reaction
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 effectively suppresses temperature increases, extends the lifespan of the power storage device by preventing exothermic reactions, and enhances energy density through efficient heat management and pressure regulation.
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 covering portion is made of low-density polyethylene to allow carbon dioxide gas permeation, reducing internal pressure and temperature.
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. The terminal positive electrode current collector and the 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 oxalate compound.