Polymer-Dispersed Positive Electrode for Battery Safety
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Solution Overview
Problem
Existing secondary batteries with high energy density face safety issues due to internal short circuits, which generate excessive heat and degrade performance, as controlling conductivity to improve thermal stability increases resistance.
Innovation Solution
Incorporating a polymer material with a melting point or thermal decomposition temperature between 200°C and 500°C, dispersed as island-shaped regions in the positive electrode active material layer, to block conductive paths and increase resistance during short circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conductivity is controlled to improve thermal stability, then safety is improved, but battery resistance increases leading to performance degradation
Solution Approach 1:
The positive electrode active material layer is segmented into multiple functional regions: conductive regions containing positive electrode active material particles and conductive aid for maintaining low resistance during normal operation, and insulating regions containing polymer material particles that provide high resistance during thermal runaway. This spatial segmentation allows the electrode to exhibit both low resistance for performance and high resistance for safety under different conditions.
Solution Approach 2:
Different regions of the positive electrode active material layer are assigned different electrical properties. The conductive regions maintain low resistance for efficient charge discharge, while the insulating regions provide high resistance when temperature rises. This local differentiation of material properties enables the electrode to simultaneously achieve good battery performance and high safety.
2Quantity of substance
If high energy density is achieved, then battery capacity is improved, but heat generation from internal short circuit increases
Solution Approach 1:
The polymer material particles act as intermediary elements distributed within the positive electrode active material layer. During normal operation, they remain inactive and do not affect battery capacity. When thermal runaway occurs, they melt and form insulating barriers that interrupt current flow, thereby mediating between the high energy density requirement and the heat generation problem by providing passive safety protection.
Solution Approach 2:
The polymer material particles are pre-dispersed throughout the positive electrode active material layer during electrode manufacturing. This preliminary placement ensures that protective insulating barriers are already in position before any short circuit occurs. When thermal runaway happens, these pre-positioned particles rapidly melt and form barriers, preventing the propagation of short circuits and reducing heat generation from runaway reactions.
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 approach enhances safety by reducing short-circuit currents and maintaining battery performance, achieving both high safety and good battery performance.
Implementation Method 1
the additive is a polymer material having a melting point or thermal decomposition temperature of 200°C or higher and 500°C or lower
Implementation Method 2
the additive is a polymer material having a melting point or thermal decomposition temperature of 200°C or higher and 500°C or lower
Implementation Method 3
Joule heat generated by the short-circuited current
Data Source
Figure 1
AI summary
A nonaqueous electrolyte secondary battery includes a positive electrode, a negative electrode, a nonaqueous electrolyte, and a separator provided between the positive electrode and the negative electrode. The positive electrode includes a positive electrode current collector and a positive electrode active material layer carried on the positive electrode current collector. The positive electrode active material layer contains a positive electrode active material, a binder, and an additive. The additive is a polymer material having a melting point or thermal decomposition temperature of 200°C or higher and 500°C or lower. In a cross section of the positive electrode active material layer, the polymer material forms and is dispersed as a plurality of island-shaped regions. The average area of top three largest of the island-shaped regions is 900 µm2 or less.