Bipolar Battery PTC Resistor Current Interruption
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Solution Overview
Problem
Bipolar secondary batteries, such as those used in electric vehicles, face challenges in preventing temperature increases due to short-circuit currents, which can lead to heat generation and damage from boiling electrolytes and melting separators.
Innovation Solution
Incorporating a temperature-sensitive resistor with a positive temperature coefficient (PTC) thermistor between laminated bodies, which increases electrical resistance in response to temperature increases, thereby interrupting excessive currents and preventing overheating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fluid sealant is used between current collectors to prevent electrolyte degradation, then the electrolyte layer is protected from moisture in air, but the fluid sealant undergoes electrolysis under high voltage and loses insulation property
Solution Approach 1:
The fluid sealant is divided into a plurality of sealed layers, so that the fluid sealant does not undergo high voltage. Each sealed layer has a thickness of 1 mm or less, preventing electrolysis while maintaining sealing effectiveness.
2Reliability
If the bipolar secondary battery is heated to high temperature, then the PTC layer resistance becomes high enough to act as an isolator, but this does not prevent short-circuit current or heat generation in normal operating conditions
Solution Approach 1:
A current collector with a PTC layer is inserted between adjacent laminated bodies to serve as an intermediary protective element. This PTC layer acts as a current interrupting member that responds to temperature increases by increasing resistance, thereby interrupting short-circuit current and preventing heat generation.
3Object-affected harmful factors
If a PTC layer is added between laminated bodies to interrupt current, then short-circuit current can be interrupted, but the resistance increases under normal operating conditions affecting battery performance
Solution Approach 1:
The PTC layer's resistance is dynamically changed based on temperature. Under normal operating conditions, the resistance is low to minimize impact on battery performance. When temperature increases indicate a short-circuit condition, the resistance increases to interrupt the current.
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
The solution effectively suppresses temperature rises in the battery, preventing the boiling of electrolytes and melting of separators, thus protecting the battery from damage and ensuring safe operation.
Implementation Method 1
a temperature sensitive resistor arranged between the positive electrode and the negative electrode of a pair of adjacent laminated bodies. The temperature sensitive resistor is formed of a positive temperature coefficient thermistor that increases resistance in response to a temperature increase
Implementation Method 2
When an external circuit connected to a bipolar secondary battery is shorted, a large amount of a short-circuit current flows continuously in the battery and the battery produces heat
Data Source
Figure 1~2
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Figure 5~7
AI summary
A bipolar secondary battery comprises laminated bodies. The laminated body comprises bipolar electrodes laminated via an electrolyte layer. The bipolar electrode comprises a positive electrode active material layer and a negative electrode active material layer formed on surfaces of a current collector. A positive electrode is formed on one end of the laminated bodies and a negative electrode is formed on another end. A temperature sensitive resistor having a smaller area than an electrical reaction area of the positive electrode active material layer and the negative electrode active material layer is arranged between the positive electrode and the negative electrode of a pair of adjacent laminated bodies, thereby suppressing a temperature increase caused by a high current by increasing the resistance in response to the flow of the high current into the bipolar secondary battery such as when an external circuit is shorted.