Thermal shutdown electrodes can provide a safety control for lithium‐ion batteries (LIBs) under a wide range of applications. However, developing such an electrode is difficult due to the lack of electrochemically compatible materials with suitable temperature‐responsive functions. Herein, a new thermal‐responsive conductive polymer—poly(3‐dodecylthiophene) (P3DDT)—is reported, and this polymer is used as a coating layer of electrode substrate to fabricate a thermal shutdown cathode of Al/P3DDT/LiCoO2 (LCO‐P3DDT). Benefited by the high room‐temperature conductivity, strong positive‐temperature‐coefficient (PTC) effect, and appropriate transition temperature of the P3DDT layer, the LCO‐P3DDT cathode not only exhibits similar electrochemical performance as a conventional LCO cathode at normal operating temperatures, but also plays a desired shutdown function to switch off the electrode reaction at elevated temperatures of ≥90 °C, thus protecting the cell from thermal runaway. This PTC effect of p‐doped P3DDT is found to be given rise by the thermal de‐doping of anions from the doped P3DDT skeleton at elevated temperature. This temperature‐responsive mechanism may provide a new insight for designing better thermal shutdown electrodes for a wide variety of battery applications.
The samarium-doped ceria (SDC) nanospheres were prepared by the one-step hydrothermal method and characterized by transmission electron microscope, scanning electron microscope, powder X-ray diffraction, X-ray photoelectron spectroscopy, energy-dispersive spectrometer and Raman spectra. According to the results, samarium was doped into the lattice successfully. The as-prepared samples were dispersed well and the average diameter was 60 nm. It showed better catalytic performance than pure ceria and the most appropriate concentration of doping was found.
Thermal safety is an increasing concern
with the widespread application
of lithium-ion batteries (LIBs) in electric vehicles and energy storage
stations. To address this concern, we propose herein a reversible
thermo-responsive switching material (RTSM) and use this material
to fabricate a temperature-sensitive cathode to enable reversible
thermal protection of LIBs. The RTSM material is achieved simply by
dispersing conductive fillers of multiwall carbon nanotubes (MWCNTs)
in a mixed plastic matrix of poly(vinylidene fluoride) (PVDF) and
poly(methyl methacrylate) (PMMA) polymers. Benefiting from the strong
hydrogen-bonding interaction between the MWCNT surface and PMMA molecules
as well as the large thermal expansion coefficient of the PVDF polymer,
the RTSM material exhibits a strong yet reversible PTC effect, with
its resistivity sharply rising up by 3 orders of magnitude at 110–120
°C and suddenly dropping down to the original value at room temperature
even after multiple thermal cycles. As a result, the LiCoO2 cathode with an RTSM coating sandwiched in between the Al foil current
collector and the electrode-active layer demonstrates a reversible
thermo-responsive switch behavior to rapidly shut its electrode reaction
down at an elevated temperature and to quickly resume its normal electrochemical
activity at room temperature, thus preventing the thermal runaway
while without compromising the normal electrochemical performances
of the cell. This work provides a possible route for designing reversible
thermo-responsive materials and building safer LIBs.
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