Pouch Lithium Battery Thermal Conductor PTC Response
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Solution Overview
Problem
The existing pouch type lithium secondary batteries face a risk of explosion due to the slow reaction velocity of the positive temperature coefficient element during rapid temperature increases from overcharging or discharging, which compromises thermal stability.
Innovation Solution
A pouch type lithium secondary battery design that includes a positive temperature coefficient element connected to the junction pad and one of the electrode tabs, featuring conductive layers and a positive temperature coefficient material layer made of styrene butadiene rubber with added carbon, which rapidly interrupts electric current when the battery temperature rises, improving thermal stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the positive temperature coefficient element is mounted on the protection circuit module, then the battery structure is simplified and ease of manufacture is improved, but the reaction velocity becomes slow when temperature rapidly rises
Solution Approach 1:
The patent introduces a thermal conductor as an intermediary substance between the positive temperature coefficient element and the pouch bottom. This thermal conductor rapidly transmits heat from the battery interior to the PTC element, enabling the element to detect temperature increases quickly without requiring direct mounting on the protection circuit module, thus resolving the contradiction between ease of manufacture and reaction velocity
Solution Approach 2:
The patent replaces the mechanical mounting approach (directly attaching PTC element to protection circuit module) with a thermal field-based approach (using thermal conductor to transmit heat to PTC element). This substitution allows the PTC element to respond rapidly to temperature changes while maintaining simple structure and ease of manufacture
2Device complexity
If the positive temperature coefficient element responds slowly to temperature increase, then manufacturing complexity is reduced, but thermal stability and safety deteriorate due to explosion risk
Solution Approach 1:
The thermal conductor acts as a mediator that bridges the temperature detection function and the PTC element, enabling rapid thermal response without adding complex mechanical mounting structures. This maintains low device complexity while significantly improving thermal stability and preventing explosion risks
Solution Approach 2:
The patent implements preliminary thermal conduction preparation by placing the thermal conductor in advance between the pouch bottom and PTC element. This preliminary arrangement ensures that when temperature rise occurs, the heat is already positioned to quickly reach the PTC element, improving reliability without increasing device complexity
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 rapid operation of the positive temperature coefficient element effectively reduces the risk of explosion and enhances thermal stability by ensuring timely interruption of electric current during temperature increases.
Implementation Method 1
a positive temperature coefficient element which has one end attached to the junction pad, and the other end electrically connected to one of the first electrode tab and the second electrode tab, so as to interrupt electric current when a temperature of the battery rises
Implementation Method 2
the positive temperature coefficient element includes an upper conductive layer, a lower conductive layer, and a positive temperature coefficient material layer interposed between the upper and lower conductive layers
Data Source
AI summary
A pouch type lithium secondary battery having a positive temperature coefficient element disposed to rapidly operate depending on an increase in the temperature of the battery, thereby improving the thermal stability of the battery. The pouch type lithium secondary battery includes: an electrode assembly including a first electrode plate to which a first electrode tab is attached, a second electrode plate to which a second electrode tab is attached, and a separator interposed between the first and second electrode plates; a pouch material having a space in which the electrode assembly is received; a protection circuit module having a junction pad, for controlling charging and discharging of the electrode assembly; and a positive temperature coefficient element which has one end attached to the junction pad, and the other end electrically connected to one of the first and second electrode tabs, so as to interrupt electric current when a temperature of the battery rises.