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Mesoporous hollow TiO2 microboxes are synthesized by a two-step solvothermal method via CaTiO3 intermediate. Composite consisting of TiO2 microboxes and carbon nanotubes (CNT) is applied as a coating layer on conventional polymer separator for lithium-sulfur batteries. The cell using a modified separator exhibits enhanced cycling performance and rate capability. A discharge capacity of 852.3 mAh g−1 is achieved at 0.2 C after 200 cycles and more than 500 mAh g−1 of discharge capacity could be retained after 1000 cycles at 1 C, much better than the cells employing untreated or sole CNT-coated separator. Even at a high C-rate of 10 C, the cell with CNT-TiO2-coated separator could deliver a high specific discharge capacity of 561 mAh g−1. Such enhanced electrochemical performance is ascribed to the synergistic effect of CNT and TiO2 on suppressing shuttle reactions of lithium polysulfides. [ABSTRACT FROM AUTHOR]

Si nanoparticles and multi-walled carbon nanotubes (MWNTs) were combined using the simple, inexpensive, and scalable approach involving ultrasonication and positive-pressure filtration to generate binder-free freestanding flexible Si–MWNT (Si–MW) composite paper anodes for Li-ion batteries. Through controlling the Si/carbon nanotube (CNT) weight ratio, the composite with 3:2 Si/CNT ratio exhibited the optimal balance between the high capacity of SiNPs and high conductivity and structural stabilization quality of MWNTs, leading to high rate capability as well as specific capacity and cyclability surpassing the conventional slurry-cast SiNP electrode using binder and current collector and other complicated freestanding Si/carbon composite designs. After 100 cycles, our electrode retained a capacity of 1170 mA h/g at 100 mA/g and 750 mA h/g at 500 mA/g. Moreover, a different electrolyte composition enabled a reversible capacity of 1300 mA h/g at 100 mA/g after 100 cycles. The freestanding feature of our electrodes is promising for enhanced energy density of Li-ion cells. [ABSTRACT FROM AUTHOR]

Li ion battery (LIB) and electrochemical capacitor (EC) are considered as the most widely used energy storage systems (ESSs) because they can produce a high energy density or a high power density, but it is a huge challenge to achieve both the demands of a high energy density as well as a high power density on their own. A new hybrid Li ion capacitor (HyLIC), which combines the advantages of LIB and Li ion capacitor (LIC), is proposed. This device can successfully realize a potential match between LIB and LIC and can avoid the excessive depletion of electrolyte during the charge process. The galvanostatic charge-discharge cycling tests reveal that at low current, the HyLIC exhibits a high energy density, while at high current, it demonstrates a high power density. Ragone plot confirms that this device can make a synergetic balance between energy and power and achieve a highest energy density in the power density range of 80 to 300 W kg−1. The cycle life test proves that HyLIC exhibits a good cycle life and an excellent coulombic efficiency. The present study shows that HyLIC, which is capable of achieving a high energy density, a long cycle life and an excellent power density, has the potential to achieve the winning combination of a high energy and power density. [ABSTRACT FROM AUTHOR]