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Lithium metal is considered one of the most promising anode materials for realizing high volumetric and gravimetric energy density, owing to the high specific capacity (∼3860 mAh g−1) and the low electrochemical potential of lithium (−3.04 V vs. the standard hydrogen electrode). However, undesirable dendritic lithium growth and corresponding instability of the solid electrolyte interphase prevent safe and long-term use of lithium metal anodes. This paper presents a simple electrolyte approach to enhance the performance of lithium metal batteries by tuning the dielectric constant of the liquid electrolyte. Electrolyte formulations are designed by changing the concentration of ethylene carbonate to have various dielectric constants. This study confirms that high ethylene carbonate content in a liquid electrolyte enhances the cycling performance of lithium metal batteries because the electric field intensity applied to the electrolyte is reduced in relation to the polarization of the electrolyte and thus allows smooth lithium plating and formation of a stable solid electrolyte interphase. We believe that this approach provides an important concept for electrolyte system design suitable to lithium metal batteries.

A facile method for preparing mesoporous perforated Co3O4 nanoparticles with hollow channels and a thin carbon layer was newly designed and achieved with sacrificial carbon nanotube (CNT) templates. The threaded Co3O4 nanoparticles on the CNTs were fabricated through a hybridization process, and a subsequent calcination process produced mesoporous perforated Co3O4 nanoparticles. With a finely tuned calcination, CNTs were sacrificed to generate hollow channels in the Co3O4 nanoparticles and to provide a carbon source for the formation of a few nm-thick carbon layer on the surface of the Co3O4 nanoparticles simultaneously. The prepared mesoporous perforated Co3O4 nanoparticles with a robust electronic conductive layer enabled not only an enhanced electrochemical reactivity from the greatly increased contact area between the electrolyte and electrode but also a high electronic conductivity of the overall electrode so that excellent electrochemical performances (1115.1 mA h g−1 after 100 cycles; 595.9 mA h g−1 @ 5 C rate) were successfully achieved in the anode application of a lithium-ion battery.

Layered electrodes of electrodeposited RuO 2 (eRuO 2 ) and polyaniline (ePAn) are prepared on a platinum substrate to yield ePAn-on-eRuO 2 and eRuO 2 -on-ePAn electrodes and their supercapacitive properties are investigated. The eRuO 2 electrode forms a compact stratified structure with nearly flat surfaces by electrodeposition from a RuCl 3 ·3H 2 O-based solution, whereas the ePAn electrode forms densely connected particles or particle aggregates by the electrodeposition from aniline solution. In the scan rate range of 20–1000 mV s −1 , specific capacitance (810–575 F g −1 ) of ePAn-on-eRuO 2 electrode is superior by the higher probability to occur redox reaction and proton diffusion due to particulate surface and inner pores of the upper layer (ePAn), respectively. In contrast, the eRuO 2 -on-ePAn electrode loses the specific capacity (680–550 F g −1 ) but achieves higher capacity retention ratio (81%) by flat compact surface of the upper layer (eRuO 2 ).

Effects of soluble polyimide (PI) binders on large-sized Li anodes (width = 21.5 cm; thickness = 40 μm) prepared using Li-metal powder (LiMP) have been investigated. PI binders form a uniform protective layer on exposed Li-powder-coated surfaces, thereby resulting in formation of scaffold-structured LiMP-based anodes. Uniform PI surface films favor realization of Li plating on Li-metal surfaces by forming a smooth surface structure, and the three-dimensional insulating PI matrix functions as a buffer layer that absorbs volume change. Moreover, PI binders facilitate enhanced cohesion between LiMP particles. The above-described triple action of PI binders significantly reduces Li dendrites. Consequently, PI-containing LiMP-based metal anodes demonstrate enhanced electrochemical performance compared to both polymeric binders and bare Li-metal foils. Results obtained in this study reveal that LiMP-based anodes containing PI binders exhibit 89% (98.2 mAh g–1) discharge-capacity retention during the 200th cycle, whereas bare Li-metal foil demonstrates sudden degeneration during the 65th cycle. Furthermore, PI containing LiMP-based anodes exhibit improved rate capability compared to other polymeric binders considered in this study.

Li1+xAlxTi2-x(PO4)3 (LATP) solid electrolytes are prepared by hydrothermal reaction as an effective method to yield moderate ionic conductivity adoptable in actual lithium-ion batteries. Particularly examined in this study are the effects of the synthesis conditions, such as Al dopant concentration (x), hydrothermal reaction time, and calcination and sintering temperatures, on the ionic conductivity of the synthesized LATP. Through repeated synthesis and characterizations of the LATPs by variation of the values of condition variables, the optimum condition for the best LATP with adequate ionic conductivity applicable to actual lithium batteries are determined to be x = 0.3 or 0.4, a hydrothermal reaction time of 12 h, and calcination and sintering temperatures of 600 °C and 900 °C, respectively.

Three kinds of polydimethylsiloxane (PDMS)-based grafted and ungrafted copolymers such as poly[dimethylsiloxane- co -(siloxane- g -acrylate)] (PDMS-A), poly(dimethylsiloxane- co -phenylsiloxane) (PDMS-P), and poly[dimethylsiloxane- co -(siloxane- g -ethylene oxide)] (PDMS-EO) are used as additives to standard liquid electrolyte solutions to enhance the lithium-ion battery performance at low temperatures. Liquid electrolyte solutions with PDMS-based additives are electrochemically stable under 5.0 V and have adequate ionic conductivities of 10 −4 S cm −1 at -20 °C. Particularly, liquid electrolytes with PDMS-P and PDMS-EO exhibit higher ionic conductivities of around 5 × 10 −4 S cm −1 at -20 °C, indicating a specific resisting property against the freezing of the liquid electrolyte components. As a result, the addition of PDMS-based additives to liquid electrolytes improves the capacity retention ratio and rate-capability of lithium-ion batteries at low temperatures.

Porous polyethylene (PE) or nonwoven poly(vinylidene fluoride) (PVdF) separator-supported gel polymer electrolytes are realized by thermal polymerization of a precursor solution consisting of poly(ethylene glycol)diacrylate (PEGDA) and an electrolyte solution (1 M LiPF 6 in an equal-volume mixture of ethylene carbonate and dimethyl carbonate). The polymerization conditions are optimized to include a PEGDA content of 3 wt.% in the precursor solution and subsequent heat treatment at 80 °C for 10 min. Even though the gelled PEGDA electrolyte has a lower ionic conductivity than the electrolyte solution, a Li x CoO 2 /graphite full-cell that has a gel electrolyte with optimized PEGDA content on the PVdF separator achieves a battery performance superior to the one with PE. The best battery performances achieved are a high discharge capacity (116 mAh g −1 ), a good high-rate capability (95 mAh g −1 at 5.0 C-rate), and a high capacity retention ratio (90%) after the 100th cycle. This enhancement is due to the incorporation of a polar electrolyte solution that is entrapped by the polar PEGDA matrix within the nonwoven PVdF separator, which is a more suitable host that is able to well absorb and preserve the gel electrolyte.

From mixed (anatase and rutile) bulk particles, anatase TiO2 nanotubes are synthesized in this study by an alkaline hydrothermal reaction and a consequent annealing at 300–400 °C. The physical and electrochemical properties of the TiO2 nanotube are investigated for use as an anode active material for lithium-ion batteries. Upon the first discharge–charge sweep and simultaneous impedance measurements at local potentials, this study shows that interfacial resistance decreases significantly when passing lithium ions through a solid electrolyte interface layer at the lithium insertion/deinsertion plateaus of 1.75/2.0 V, corresponding to the redox potentials of anatase TiO2 nanotubes. For an anatase TiO2 nanotube containing minor TiO2(B) phase obtained after annealing at 300 °C, the high-rate capability can be strongly enhanced by an isotropic dispersion of TiO2 nanotubes to yield a discharge capacity higher than 150 mAh g−1, even upon 100 cycles of 10 C-rate discharge–charge operations. This is suitable for use as a high-power anode material for lithium-ion batteries.

We observed that 3-chloroanisole (3CA), as an electrolyte additive was very effective for overcharging protection during a 12 V overcharging reaction. During overcharging, the cell voltage did not increase beyond 5.3 V, as opposed to other aromatic compounds that showed a voltage shoot-up to 12 V. This behavior was due to the 3CA decomposition and the formation of conducting polymer film within separator and at cathode/electrolyte interface, which consumes the surplus current and inhibit the voltage increase through the shunting effect. In addition, the use of 3CA did not lead to any problems with rate capability, cycle life, and long-term storage behavior at 50 and 70 °C. Furthermore, during storage at 90 °C for 4 and 24 h, electrolyte with 3CA in a Li-ion cell showed a similar increase of cell thickness as a cell without 3CA.

We have fabricated two types of supercapacitors, redox and hybrid, based on poly(ethylenedioxythiophene) (PEDOT) and MSP-20 powder as electrode materials with Et 4 NBF 4 in PC and LiPF 6 in EC/DMC as electrolyte solutions. The redox type of supercapacitor is assembled with two PEDOT electrode sheets, while the hybrid type with PEDOT and MSP-20 electrode sheets. Their electrochemical properties in different electrolyte solutions and cut-off voltage range are investigated. From the results of charge and discharge for the hybrid type, the specific discharge capacitance of ~56 F/g after 1000th cycle in the range 0–3 V is observed with LiPF 6 in EC/DMC system. The electrochemical properties of the hybrid type supercapacitor are shown much better than them of the redox type.

Polymer electrolytes based on the mixture of the blended polymer matrix (P(VdF-co-HFP)(Kynar 2801)/poly(vinyl acetate)(PVAc)) and the liquid electrolyte(EC/PC/1M LiClO 4 ) were prepared by solution casting. Ionic conductivity, interfacial stability with the lithium electrode, and electrochemical stability window of the polymer electrolytes were investigated by varying the PVAc content in the matrix polymer. The ionic conductivity of the plasticized polymer electrolyte slightly decreased with the PVAc content. The ionic conductivity of the polymer electrolyte based on the Kynar 2801/PVAc (7/3, w/w) blend was 2.3×10 −3 S cm −1 at 25°C. Interfacial stability between the polymer electrolyte and the lithium electrode was enhanced by blending PVAc with the Kynar 2801. The polymer electrolyte based on the Kynar 2801/PVAc (7/3, w/w) blend was electrochemically stable up to 5.0 V.