Electrode Protective Layer Composition With PTC Conductivity Switching
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Solution Overview
Problem
Existing lithium secondary batteries face challenges in enhancing safety while maintaining conductivity and rate characteristics, as adding functional layers to prevent ignition and explosion often compromises these properties.
Innovation Solution
A composition for forming an electrode protective layer using a polythiophene-based conductive polymer with PTC characteristics and porous conductive carbon particles with 10-300 nm pores, which allows for high conductivity and resistance increase under high temperatures, preventing short circuits and heat generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a functional layer is added to increase resistance and improve safety, then safety is improved, but conductivity and rate characteristics are lowered
Solution Approach 1:
The patent utilizes the PTC (positive temperature coefficient) effect to change the electrical resistance parameter of the protective layer dynamically. At normal temperatures, the layer maintains low resistance for good conductivity, but at elevated temperatures (above 100°C), the resistance increases dramatically to interrupt current flow and prevent thermal runaway, thus resolving the contradiction between maintaining conductivity and improving safety
Solution Approach 2:
The protective layer is formed as a composite material combining polythiophene-based conductive polymer with porous conductive carbon particles. This composite structure provides both the PTC effect for safety and sufficient conductivity for battery performance, achieving a balance between the contradictory requirements of safety and conductivity
2Reliability
If the thickness of the functional layer is increased to improve safety, then safety is improved, but electrolyte penetration is reduced and conductivity deteriorates
Solution Approach 1:
The protective layer incorporates porous conductive carbon particles with specific pore structures that allow electrolyte penetration even when the layer has sufficient thickness to provide safety. The porous structure maintains ion transport pathways while the PTC effect ensures thermal safety, thus resolving the contradiction between layer thickness for safety and electrolyte penetration for rate characteristics
3Reliability
If a protective layer is added to prevent short circuit, then safety is improved, but internal resistance increases and power output is reduced
Solution Approach 1:
The protective layer exhibits dynamic electrical resistance that adapts to operating conditions. At normal operating temperatures, the layer maintains low resistance to minimize power loss and maintain power output. When abnormal temperature rise occurs indicating potential short circuit or thermal runaway, the PTC effect triggers a dramatic resistance increase to interrupt current flow, thus dynamically balancing power output and safety
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 electrode protective layer effectively interrupts current flow during high temperatures or impacts, preventing ignition and explosion while maintaining excellent conductivity and rate characteristics of the battery.
Implementation Method 1
a polythiophene-based conductive polymer that exhibits PTC (positive temperature coefficient) characteristics
Implementation Method 2
porous conductive carbon particles having a plurality of pores with a diameter of 10 to 300 nm formed therein
Data Source
AI summary
The present disclosure relates to a composition for forming an electrode protective layer for a lithium secondary battery, which not only suppresses heat generation or ignition caused by external impacts, etc., and thus has excellent stability, but also makes it possible to provide electrodes and batteries having excellent conductivity and rate characteristics, and to an electrode for a lithium secondary battery and a lithium secondary battery comprising the same.