| Lithium ion batteries with high energy density can satisfy the need of large-scale electric vehicle and grid-storage applications. Therefore, it is imperative to search new electrode materials with remarkably improved performance. Transition metal oxides with high theoretical capacity are considered as ideal candidates alternative to carbon materials for Li+ storage. However, on account of its poor electronic conductivity, large volume changes and materials pulverization over extended cycling, most of materials show low capacity retention and poor high rate performance. Composited with other conductive materials is an effective way to optimize and enhance their electrochemical performance of oxide materials. Titanium carbide(TiC) is an appropriate supporting material with high chemically stability, excellent mechanical durability and high electronic conductivity. At present, researches on using TiC matrix as for anode materials for LIBs is rarely investigated. Herein, we prepared TiC nanowires via a simple, convenient, and cost-effective biotemplated method, and then fabricated core/shell TiC/NiO, TiC/Co3O4, TiC/MnO nanowires composites. The microstructure and lithium storage performances of the samples were researched.The core/shell TiC/NiO nanowires and NiO nanosheets were synthesized by hydrothermal method. TiC core is 100-150 nm in width and up to several micrometers in length, NiO nanosheets grow directly on the TiC substrate, forming a net-like porous structure. The as-constructed TiC/NiO(32 wt.% NiO) offers high overall capacity and excellent cycling ability, retaining above 507.5 mAh/g at 200 mA/g throughout 60 cycles(much higher than theoretical value of the TiC/NiO composite). Moreover, the lithium storage mechanism of the composite is synchronous battery-capacitive, in which the TiC nanowire core exhibits a typical double layer capacitive behavior, and the Ni O nanosheet shell serves as the active material to store Li+. Besides, the high rate capability is far superior to that of NiO, owing to its double layer capacitive characteristics of TiC nanowire and intrinsic high electrical conductivity for facile electron transport during Li+ storage process.The TiC/Co3O4 and Co3O4 samples were prepared by hydrothermal for different reaction time. The TiC/Co3O4 shows a typical core/shell structure, the core is TiC nanowires, and Co3O4 nanoparticles grow on the nanowires as the shell. As the anode material, the electrochemical lithium storage performance of TiC/Co3O4(36% of Co3O4 in composite, hydrothermal for 9 h) is superior to Co3O4(hydrothermal for 9 h), which achieves 753.7 mAh/g at 50 th cycle(91.4%) at a current density of 50 mA/g. After discharging at high current density(2 A/g), the reversible capacity(1060.4 mAh/g) can regain and surpass the initial one(1048.2 mAh/g) when return to 50 mA/g, which is exceed the value of Co3O4 overall.The immersion method was used to synthesize core/shell TiC/MnO nanowires. The core and shell of the acquired composites are TiC nanowires and MnO nanoparticles, respectively. As anode materials in lithium ion batteries, the optimal TiC/MnO(MnO of the composite is 46%) deliver discharge capacity of 542.9 mAh/g at 50 th cycle at 100 mA/g, and the retention is ~95%.The outstanding performance of both TiC/Co3O4 and TiC/MnO can be ascribed to the core/shell structure and the TiC. First, the core/shell nanostructure shorted Li+ diffusion length, increased electrolyte-electrode contact area, and had good tolerance to volume expansion. Second, intrinsic high electrical conductivity and chemistry stability of TiC can maintain the nanowire integrity well during repeated cycling. |
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