Dual Functional Electrode Layers for Safer Lithium Batteries
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Solution Overview
Problem
Rechargeable lithium batteries face challenges in ensuring physical, thermal, and electrochemical safety while maintaining high energy density, particularly during overcharging and overheating conditions.
Innovation Solution
The electrode incorporates a dual functional layer structure, comprising a first functional layer with a positive temperature coefficient (PTC) resin and a second functional layer with lithium transition metal phosphate, which works together to manage thermal and physical safety, respectively, by limiting current flow and inducing Joule heat reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a functional layer is added between the current collector and active material layer to improve safety, then physical and thermal safety are improved, but energy density is reduced
Solution Approach 1:
The functional layer is divided into two distinct layers: a first functional layer containing PTC resin for thermal safety, and a second functional layer containing lithium transition metal phosphate for physical safety. This segmentation allows each layer to specialize in specific safety functions while minimizing overall thickness and weight impact on energy density.
Solution Approach 2:
Different materials are used in different regions of the functional layer to provide localized functions. The PTC resin is positioned to address thermal runaway risks, while the lithium transition metal phosphate is positioned to address physical impact and dendrite issues. This local quality approach ensures optimal safety performance with minimal material usage.
2Temperature
If a PTC resin layer is added to prevent thermal runaway, then thermal safety is improved, but internal resistance increases
Solution Approach 1:
The PTC resin is formulated with specific molecular weight and crystallinity parameters to control its phase transition temperature. By optimizing these parameters, the resin remains conductive at normal operating temperatures but rapidly increases resistance only when thermal runaway is detected, thus providing thermal protection with minimal impact on normal battery performance.
3Reliability
If lithium transition metal phosphate is added to the functional layer to prevent dendrite formation, then electrochemical safety is improved, but manufacturing complexity increases
Solution Approach 1:
The lithium transition metal phosphate is pre-formed into particles with controlled size distribution before being incorporated into the slurry. This preliminary preparation ensures uniform dispersion and proper thickness when the functional layer is applied, simplifying the manufacturing process while maintaining effective dendrite prevention.
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 dual-layer design effectively secures electrochemical, physical, and thermal safety, minimizing energy density reduction and enhancing reliability against overcharging and external impacts.
Implementation Method 1
the first functional layer includes a positive temperature coefficient (PTC) resin
Implementation Method 2
the second functional layer includes a lithium transition metal phosphate
Data Source
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AI summary
Disclosed are an electrode for a rechargeable lithium battery and a rechargeable lithium battery including the same. In an embodiment, an electrode for a rechargeable lithium battery includes a current collector; an active material layer on the current collector; and a functional layer between the current collector and the active material layer, wherein the functional layer includes a first functional layer and a second functional layer, the first functional layer includes a positive temperature coefficient (PTC) resin, and the second functional layer includes a lithium transition metal phosphate.