A positive-temperature-coefficient electrode with thermal protection mechanism for rechargeable lithium batteries

Abstract

A new positive-temperature-coefficient (PTC) material was prepared simply by blending of conductive Super P carbon black (CB) with insulating poly(methyl methacrylate) (PMMA) polymer matrix, which was empolyed as a coating layer on the aluminium foil substrate to fabricate a sandwiched Al/PTC/LiCoO 2 cathode. The experimental results from cyclic voltammetry, charge-discharge measurements and impedance spectroscopy demonstrated that the PTC electrode has a normal electrochemical performance at ambient temperature, but shows an enormous increase in the resistance at the temperature range of 80120°C. This PTC behavior greatly restrains the reaction current passing through the electrode at elevated temperatures, capable of acting as a self-actuating safety mechanism to prevent the battery from thermal runaway.

Methods for promoting electrochemical properties of LiNil/3Col/3Mnl/3O2 for lithium-ion batteries

“…The NCM would become a good competitor for power battery by promoting its special capacity, energy density, rate capability, cycle life, especially the thermal stability properties [67]. The positive temperature coefficient resistors (PTC) are usually equipped as a safety device on the crust of commercial lithium ion batteries to restrict or even prevent current from flowing through the cell under abusive conditions [68].…”

Smart Materials and Design toward Safe and Durable Lithium Ion Batteries

“…Due to their suitable Curie temperature and compatibility with current LIB systems, various polymer‐PTC‐based cathode materials have been developed and demonstrated their feasibility. These polymer PTC composites include high‐density polyethylene (PE), particle polyvinylidene fluoride (PVDF), poly(methyl methacrylate) (PMMA), ethylene vinyl acetate (EVA), etc. Generally, in this strategy, the polymers, carbon black, and cathode active materials are mechanically mixed, which makes it hard to form a conductive network between the active components and the PTC, thus leading to less promising rate capability of the electrodes and batteries.…”

“…Besides mixing or in situ coating the cathode materials with PTC materials, a number of carbon–polymer composites, such as carbon black/epoxy resin and carbon black PMMA layers, have also been applied between the cathode layer and the Al current collector as a thermal‐response PTC layer.…”

“…Finally, this PTC layer results in self‐shutdown of a LIB under abnormal state. Xia et al also developed a carbon black/PMMA PTC layer, and showed that the resistance of this PTC electrode increased rapidly between 80 and 120 °C, so it can obviously suppress the current flow through the electrode at high temperatures. Between the LiFePO 4 cathode layer and the aluminum current collector, Li et al also coated a mixed Ni PVDF layer.…”

Positive‐Temperature‐Coefficient Graphite Anode as a Thermal Runaway Firewall to Improve the Safety of LiCoO2/Graphite Batteries under Abusive Conditions

“…Therefore, if materials with temperature-sensitive properties are added to the battery, they will be thermally activated when the battery temperature rises to the threshold of safety, and the batteries will no longer explode or combust. [22][23][24][25][26][27][28][29][30][31][32][33] With the emergence of battery systems with higher specific energies, it can be predicted that solving safety problems caused by thermal runaway will be increasingly challenging. [33][34][35][36][37] In functional polymer materials, positivetemperature-coefficient (PTC) materials have the characteristics of increasing resistance with increasing temperature and theoretically have the possibility to play an important role when the heat in batteries reaches a certain degree.…”