PTC Polymer Current Collector for Battery Overheat Isolation
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Solution Overview
Problem
Secondary batteries are prone to ignition or explosion due to short phenomena caused by direct contact between positive and negative electrodes, leading to increased heat generation and gas generation, which can be exacerbated by overcharging, high temperatures, or external shocks.
Innovation Solution
A current collector with a polymer layer exhibiting a positive temperature coefficient (PTC) effect is used to form electrodes, maintaining low resistance for normal operation and increasing resistance in abnormal conditions to prevent energization and stabilize the battery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a current collector with low resistance is used to ensure good electrical characteristics in normal operation, then electrical performance is improved, but safety in abnormal states (high temperature, short circuit) deteriorates due to inability to block energization
Solution Approach 1:
The patent applies parameter changes by utilizing the positive temperature coefficient (PTC) effect, where the resistance of the polymer layer changes based on temperature. In normal operating conditions, the polymer layer maintains low resistance for good electrical characteristics. When abnormal conditions occur (temperature increase or short circuit), the resistance sharply increases to block energization, thus resolving the contradiction between electrical performance and safety.
Solution Approach 2:
The polymer layer acts as an intermediary between the current collector and the external circuit. It functions as a smart material that mediates electrical current flow based on temperature conditions, allowing normal operation while preventing dangerous states, thus bridging the gap between electrical performance requirements and safety requirements.
2Loss of energy
If the resistance of the current collector is kept low for normal operation, then energy efficiency is improved, but the ability to prevent heat generation and ignition in abnormal states worsens
Solution Approach 1:
The polymer layer's resistance parameter dynamically changes with temperature. During normal operation at low temperatures, it maintains low resistance to minimize energy loss. When abnormal heat generation occurs, the temperature increase triggers a sharp rise in resistance, which blocks current flow and prevents further heat generation and potential ignition, thus resolving the contradiction between energy efficiency and heat prevention.
Solution Approach 2:
The patent converts the harmful effect of temperature increase (which normally would lead to ignition) into a beneficial protective mechanism. The temperature rise itself triggers the PTC effect, causing resistance increase that blocks energization and prevents the harmful outcome, thus transforming the harmful thermal effect into a protective feature.
3Object-affected harmful factors
If a polymer layer with PTC effect is added to the current collector to provide safety in abnormal states, then safety is improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent employs composite materials by combining the current collector substrate with a polymer layer exhibiting PTC effect. This composite structure integrates the conductive properties of the current collector with the temperature-responsive properties of the polymer, providing safety functionality without requiring separate complex safety systems. The composite material approach simplifies the overall device structure while achieving the desired safety performance.
Solution Approach 2:
The polymer layer serves multiple functions simultaneously: it acts as a conductive material for normal electrical operation, a temperature sensor for detecting abnormal conditions, and a protective element for blocking energization. This multi-functionality reduces device complexity by eliminating the need for separate components for each function.
4Object-affected harmful factors
If the PTC effect is enhanced to provide better protection in abnormal states, then safety performance is improved, but electrical characteristics in normal operation deteriorate due to increased resistance
Solution Approach 1:
The patent optimizes the PTC characteristics of the polymer layer to achieve the right balance. The polymer is selected or designed to have a transition temperature that corresponds to abnormal operating conditions, ensuring that resistance remains low during normal operation (maintaining good electrical characteristics) while sharply increasing only when temperature exceeds the safe operating range (providing adequate protection). This precise parameter control resolves the contradiction between protection level and electrical performance.
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 current collector ensures stable operation and storage in normal conditions while providing safety by blocking energization in abnormal states, preventing potential hazards.
Implementation Method 1
a polymer layer formed on the current collector main body... exhibiting a positive temperature coefficient (PTC) effect... maintaining low resistance for normal operation and increasing resistance in abnormal conditions
Data Source
AI summary
A current collector and a use thereof is disclosed. The current collector is capable of forming an electrode, which does not affect performance and operation of a secondary battery by exhibiting, in a normal state, excellent electrical characteristics including low resistance, and can ensure stability by blocking, in an abnormal state, energization of an electrode assembly through resistance increase, and a use thereof. An electrode, an electrode assembly and a secondary battery comprising the current collector are also described.