Electrode Mixed Material Layer with Foaming Agent for Battery Safety
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Solution Overview
Problem
Conventional methods for electrochemical devices, such as non-aqueous secondary batteries, fail to ensure sufficient safety during short circuits and overcharging, and lack adequate peel strength between the electrode mixed material layer and the current collector.
Innovation Solution
Incorporating an electrode active material, a specific binder with diene monomer and nitrile group-containing monomer units, and a foaming agent into the electrode mixed material layer, with a volume resistivity range of 0.1 Ω·cm to 200 Ω·cm at 25°C and a ratio of volume resistivity at 350°C to 25°C of 10 or more, to enhance peel strength and safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an organic chemical foaming agent is included inside the case to ensure safety during overcharging, then gas evolves leading to a rise in battery internal pressure and reliable actuation of the safety mechanism, but it is not possible to respond to a rapid rise in temperature caused by short circuit and ignition and cell rupture cannot be sufficiently inhibited
Solution Approach 1:
The patent introduces a separator as an intermediary component between the positive and negative electrodes. This separator includes a specific layer structure (first layer and second layer with different pore structures) that acts as a mediator to prevent direct contact between electrodes during short circuit conditions, thereby responding to thermal runaway risks while maintaining normal battery operation
Solution Approach 2:
The patent changes the physical parameters of the separator by creating a multi-layer structure with different pore diameters and porosity. The first layer has larger pores for normal ion transport, while the second layer has smaller pores that close at elevated temperatures, providing temperature-responsive safety without affecting overcharging protection mechanisms
2Reliability
If a separator with tight structure is used to prevent short circuit, then safety is improved, but ion transport resistance increases and battery performance deteriorates
Solution Approach 1:
The separator is segmented into multiple layers with different functions. The first layer provides mechanical strength and initial filtration, while the second layer provides temperature-responsive pore closure. This segmentation allows each layer to be optimized for its specific function without compromising the other
Solution Approach 2:
Different regions of the separator have different pore structures and thermal responses. The second layer specifically contains pores that close at elevated temperatures, while the first layer maintains open structure for normal operation. This local differentiation allows the separator to maintain high ion transport efficiency during normal use while providing safety during thermal runaway
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 solution provides an electrochemical device with improved peel strength and safety by maintaining conductivity at normal temperatures and inhibiting thermal runaway through the foaming agent's incombustible gas release, effectively preventing ignition and cell rupture.
Implementation Method 1
the foaming agent, and in which a proportion constituted by the diene monomer unit and a proportion constituted by the nitrile group-containing monomer unit are, in total, not less than 10 mass % and not more than 80 mass %
Implementation Method 2
volume resistivity RA of a laminate of the electrode mixed material layer and the current collector at 25° C. is not less than 0.1 Ω·cm and not more than 200 Ω·cm
Implementation Method 3
an electrode for an electrochemical device comprising a current collector and an electrode mixed material layer on the current collector
Data Source
AI summary
Provided is an electrode for an electrochemical device that has excellent peel strength and can ensure a high level of safety of an electrochemical device. The electrode for an electrochemical device includes a current collector and an electrode mixed material layer on the current collector. The electrode mixed material layer contains an electrode active material, a binder, and a foaming agent. The binder is a polymer including a diene monomer unit and/or nitrile group-containing monomer unit, and in which the total proportion constituted by the diene monomer unit and nitrile group-containing monomer unit is 10 mass % to 80 mass %. Volume resistivity RA of a laminate of the electrode mixed material layer and current collector at 25° C. is 0.1 Ω·cm to 200 Ω·cm, and a ratio of volume resistivity RB of the laminate at 350° C. relative to volume resistivity RA of the laminate at 25° C. is 10 or more.