Conductive Protective Paste for High Voltage Current Collectors
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Solution Overview
Problem
High voltage lithium secondary cells face challenges in protecting current collectors from corrosion, as existing surface protective layers and binders are inadequate, leading to deterioration of cell characteristics and capacity.
Innovation Solution
A conductive protective layer-forming paste containing polytetrafluoroethylene (PTFE) and a conductive filler, with optional binders like tetrafluoroethylene-hexafluoropropylene copolymers, is applied to current collectors to create a protective layer with suitable volume resistivity and flexibility, preventing corrosion without impairing electrode flexibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional surface protective layers (heterocyclic compounds, noble metals, conductive polymers) are formed on current collectors, then corrosion resistance is improved, but electrode flexibility is lost and oxidation potential is insufficient for high voltage designs
Solution Approach 1:
The patent uses a composite paste containing polytetrafluoroethylene (PTFE) as binder and conductive filler particles (such as carbon black or metal particles). This composite structure combines the corrosion resistance of PTFE with the electrical conductivity of the filler, while maintaining flexibility. The composite material achieves both protection and functionality required for high voltage electrodes.
Solution Approach 2:
The patent modifies the protective layer formulation by using PTFE-based paste with specific conductive filler content and ratios. This changes the physical and chemical parameters of the protective layer to achieve both high oxidation potential resistance and maintained flexibility, enabling application in high voltage (4.35V or higher) lithium secondary cells.
2Quantity of substance
If higher voltage designs (4.35V or higher) are implemented, then cell capacity is improved, but current collector corrosion susceptibility increases
Solution Approach 1:
The patent applies a protective paste coating to the current collector before electrode assembly. This preliminary protective layer prevents the harmful oxidation and corrosion reactions that would otherwise occur at high voltages, allowing the cell to operate at higher voltages (4.35V or higher) without current collector degradation.
Solution Approach 2:
The PTFE-based protective layer acts as an intermediary barrier between the current collector and the harsh high-voltage electrochemical environment. This intermediate layer protects the current collector from direct exposure to oxidizing conditions while maintaining electrical conductivity through the incorporated conductive filler.
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 protective layer effectively shields current collectors from corrosion in high voltage designs, maintaining cell characteristics and capacity, and is suitable for both positive and negative electrodes in lithium secondary cells and electric double layer capacitors.
Implementation Method 1
a paste for forming conductive protective layers... containing polytetrafluoroethylene; and a conductive filler (b)
Data Source
AI summary
The present invention provides a conductive protective layer-forming paste for current collector laminates which can be used even for high voltage designs to protect current collectors from corroding without loss of cell characteristics, and a current collector laminate, an electrode laminate, and nonaqueous secondary cells (e.g. a lithium secondary cell, an electric double layer capacitor) that include a conductive protective layer formed therefrom. The paste for forming conductive protective layers for current collector protection includes: polytetrafluoroethylene; and a conductive filler (b). The current collector laminate includes: a conductive protective layer (A); and a current collector (B), the conductive protective layer (A) being formed by coating the paste for forming conductive protective layers onto the current collector (B).