Summary: A well‐dispersed gold nanoparticle/poly(N‐isopropylacrylamide) (PNIPAm) hydrogel nanocomposite with thermoswitchable electrical properties is prepared by the copolymerization of functional Au nanoparticles with N‐isopropylacrylamide. It is found that the electrical conductivity of the nanocomposite changes by two orders of magnitude at moderate temperature (Ttran) upon temperature stimuli. The change of electrical properties is reversible during a heating and cooling cycle.Schematic illustration of the mechanism of the thermo‐switchable electronic properties of the Au nanoparticle/PNIPAm composite.magnified imageSchematic illustration of the mechanism of the thermo‐switchable electronic properties of the Au nanoparticle/PNIPAm composite.

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In this work, we synthesized a composite cathode material containing LiFePO 4 and activated carbon ͑AC͒, which is abbreviated as LAC, by a solid-state reaction, and assembled a hybrid battery-capacitor LAC/Li 4 Ti 5 O 12 . The electrochemical performances of the hybrid battery-capacitor LAC/Li 4 Ti 5 O 12 were characterized by cyclic voltammograms, constant current charge-discharge, rate charge-discharge, and cycle performance testing. The results show the hybrid battery-capacitor LAC/Li 4 Ti 5 O 12 has advantages of the high rate capability of hybrid capacitor AC/Li 4 Ti 5 O 12 and the high capacity of battery LiFePO 4 /Li 4 Ti 5 O 12 . It is also proven that the hybrid battery-capacitor LAC/Li 4 Ti 5 O 12 is an energy storage device where the capacitor and the secondary battery coexist in one cell system.

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To achieve the higher capacity and the better cycle performance of the lithium-sulfur (L-S) batteries, a copolymer electrolyte prepared via emulsifier-free emulsion polymerization was used as the binder for the sulfur cathode in this study. This polyelectrolyte binder has uniform dispersion and good Li conductivity in the cathode that can improve the kinetics of sulfur electrochemical reactions. As a result, the capacity and cycle performance of the battery are improved evidently when the cell is discharged to 1.8 V. Moreover, when the cell is discharged to 1.5 V, the difficult deposition of LiS will take place easily at 1.75 V, and the difficult transformation from solid LiS to solid LiS will progress smoothly and completely during the voltage range of 1.55-1.75 V, too. The capacity of this L-S battery discharged to 1.5 V is as much as 1700 mAh g, which is very close to the theoretical value of sulfur cathode. The knowledge acquired in this study is valuable not only for the design of an efficient new polyelectrolyte binder for sulfur cathode but also the discovery that the discharge degree is the main fact that limits the capacity to reach its theoretical value.

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