Electrode Plate Structure With Local PTC Layer for Battery Safety
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Solution Overview
Problem
Existing secondary battery technologies face safety hazards due to high energy density, which leads to mechanical, electrical, and thermal abuse issues, causing abnormal currents and potential explosions, and previous solutions like PTC materials increase internal resistance, deteriorating battery capacity and power performance.
Innovation Solution
An electrode plate design featuring a current collector with protruding and recessed portions, a functional layer, and an active material layer, where the functional layer, composed of polymer or PTC materials, increases resistivity at high temperatures to prevent electrical connection and ensure safety, while maintaining low resistivity at room temperature, thereby enhancing both capacity and power performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If PTC material coating is added to prevent abnormal current, then safety performance is improved, but internal resistance increases significantly, deteriorating battery capacity and power performance
Solution Approach 1:
The patent applies local quality by creating protruding portions and recessed portions on the current collector surface, with the PTC material coating selectively applied to the recessed portions. This localized application ensures that the PTC safety function is activated only where needed (in recessed areas where abnormal current may concentrate), while the protruding portions maintain low resistance electrical contact, thus resolving the contradiction between safety and energy loss.
Solution Approach 2:
The current collector surface is segmented into protruding portions and recessed portions, with different functional characteristics. The recessed portions contain the PTC material coating for safety protection, while the protruding portions provide low-resistance electrical pathways. This segmentation allows simultaneous achievement of safety performance and low internal resistance.
2Object-affected harmful factors
If PTC material coating is added to prevent abnormal current, then thermal runaway prevention is improved, but power performance deteriorates due to increased resistance
Solution Approach 1:
The PTC material coating is locally applied to recessed portions of the current collector rather than uniformly across the entire surface. This localized application provides thermal runaway protection in areas where abnormal current concentration is most likely to occur, while maintaining low resistance pathways through the protruding portions, thus preserving power performance.
Solution Approach 2:
The recessed portions with PTC coating act as intermediary safety elements that only activate under abnormal conditions. During normal operation, the protruding portions serve as the primary electrical pathways, minimizing the impact of the PTC material on power performance while still providing thermal protection capability.
3Reliability
If functional layer is disposed in recessed portions only, then safety at high temperature is improved, but contact area between active material layer and current collector is reduced
Solution Approach 1:
The functional layer (PTC material coating) is selectively disposed in the recessed portions rather than covering the entire current collector surface. This local quality approach provides high-temperature safety protection in the recessed areas while leaving the protruding portions available for optimal electrical contact with the active material layer, thus maintaining sufficient contact area.
Solution Approach 2:
The current collector surface is segmented into functional zones: recessed portions containing the functional layer for safety, and protruding portions providing electrical contact. This segmentation allows the functional layer to be positioned where it provides maximum safety benefit without compromising the contact area needed for 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 electrode plate design effectively balances battery performance at room temperature with enhanced safety at high temperatures by controlling resistivity, reducing the risk of thermal runaway and maintaining capacity and power performance.
Implementation Method 1
The functional layer includes at least one of a polymer material or a PTC material (a positive temperature coefficient material)... When the PTC material is heated to around Curie temperature, a resistivity of the material increases in a step-like manner
Implementation Method 2
The functional layer expands or makes the current collector and the active material layer be out of contact when the temperature rises to a value greater than or equal to 80° C. (for example, when the functional layer contains a polymer material)
Data Source
AI summary
A secondary battery includes an electrode plate including a current collector, a functional layer, and an active material layer. At least a portion of a surface of the current collector includes a plurality of protruding portions and a plurality of recessed portions. The functional layer is disposed in one or more of the plurality of recessed portions. The active material layer covers and contacts the current collector and the functional layer. The functional layer includes at least one of a polymer material or a positive temperature coefficient (PTC) material.