Battery Electrode Functional Layer for Overheat and Overcharge Safety
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Solution Overview
Problem
Rechargeable lithium batteries face challenges in ensuring physical and thermal safety, as well as electrochemical safety, particularly during overcharging and overheating, which can lead to energy density reduction and safety risks.
Innovation Solution
The electrode for rechargeable lithium batteries incorporates a current collector, an active material layer, and a functional layer comprising a positive temperature coefficient (PTC) resin and lithium transition metal phosphate, which helps in reducing Joule heat and increasing internal resistance to prevent overheating and physical damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a functional layer with PTC resin and lithium transition metal phosphate is added between the current collector and active material layer, then thermal safety and electrochemical safety are improved, but device complexity increases
Solution Approach 1:
The functional layer is segmented 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 electrochemical safety. This segmentation allows each layer to independently perform its specific safety function without interfering with the other, while collectively resolving the technical contradiction by providing comprehensive safety protection.
Solution Approach 2:
The functional layer combines two different materials with complementary safety properties: PTC resin that increases resistance at elevated temperatures to prevent thermal runaway, and lithium transition metal phosphate that suppresses lithium dendrite growth and prevents internal short circuits. This composite structure achieves both thermal and electrochemical safety simultaneously.
2Reliability
If a functional layer with PTC resin and lithium transition metal phosphate is added between the current collector and active material layer, then electrochemical safety is improved, but energy density is reduced
Solution Approach 1:
The functional layer is applied locally at the critical interface between the current collector and active material layer, where safety issues such as lithium dendrite penetration and internal short circuits most commonly occur. By concentrating the safety function at this specific location rather than throughout the entire electrode, the design provides effective electrochemical safety protection while minimizing the volume of non-active materials and preserving energy density.
3Reliability
If the functional layer increases internal resistance to prevent overheating, then thermal safety is improved, but energy loss increases
Solution Approach 1:
The PTC resin in the first functional layer provides dynamic resistance adjustment: at normal operating temperatures, the layer maintains low resistance to minimize energy loss; when abnormal temperature rise occurs, the PTC effect automatically increases the resistance to prevent thermal runaway. This dynamic response allows the system to provide thermal safety protection only when needed, avoiding continuous energy loss.
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 configuration enhances electrochemical, physical, and thermal safety, minimizing energy density reduction and ensuring reliable operation by limiting lithium ion and electron movement during abnormal temperatures, thus securing safety and performance.
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
AI summary
An electrode for a rechargeable lithium battery and a rechargeable lithium battery including the same are provided. 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.