RESUMO
Li3V2(PO4)3/C (LVP/C) composites have been modified by different ways of Zr-incorporation via ultrasonic-assisted solid-state reaction. The difference in the effect on the physicochemical properties and the electrochemical performance of LVP between Zr-doping and ZrO2-coating has also been investigated. Compared with pristine LVP/C, Zr-incorporated LVP/C composites exhibit better rate capability and cycling stability. In particular, the LVP/C-Zr electrode delivers the highest initial capacity of 150.4 mA h g-1 at 10C with a capacity retention ratio of 88.4% after 100 cycles. The enhanced electrochemical performance of Zr-incorporated LVP/C samples (LVZrP/C and LVP/C-Zr) is attributed to the increased ionic conductivity and electronic conductivity, the improved stability of the LVP structure, and the decreased charge-transfer resistance.
RESUMO
Na super ionic conductor (NASICON)-structured materials have evolved to play many critical roles in battery systems because of their three-dimensional framework structures. Here, by coupling NASICON-structured Na3V2(PO4)2O2F cathodes and Na3V2(PO4)3 anodes, an asymmetric Na-ion-based full cell exhibits two flat voltage plateaus at about 2.3 and 1.9 V and a high capacity of 101 mA h/g. Moreover, an all-solid-state Na-ion battery has been further enabled by the concept of using all NASICON-structured materials, including cathodes, anodes, and electrolytes (Na5YSi4O12), which delivers a high output voltage. Importantly, the full cell displays high safety without using a flammable organic liquid electrolyte and superior structure stability with all NASICON-structured materials.
RESUMO
Multi-heteroatom (N, S and F) doped carbon coated Na3V2(PO4)3 (labeled as NVP/C-ILs) derived from an ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIM]TF2N) has been successfully fabricated. The as-prepared Na3V2(PO4)3 particles are well dispersed and closely coated with a multi-heteroatom (N, S and F) doped carbon layer. As a cathode for sodium-ion batteries, the NVP/C-ILs electrode exhibits high reversible specific capacity (117.5 mA h g-1 at 1C), superior rate performance (93.4 mA h g-1 at 10C) and excellent cycling stability (â¼95% capacity retention ratio at 10C over 1000 cycles). The impressive electrochemical performance of NVP/C-ILs can be attributed to effectively conductive networks for electrons and Na+ ions induced by a joint effect of N, S and F doping on carbon. The use of multi-heteroatom doped carbon coated Na3V2(PO4)3 provides a facile and effective strategy for the fabrication of high performance electrode materials with low intrinsic electrical conductivity.
RESUMO
In this study, low cost anthracite-derived dual-phase carbon-coated Li3V2(PO4)3 composites have been successfully prepared via a traditional solid-phase method. XRD results show that the as-prepared samples have high crystallinity and anthracite introduction has no influence on the LVP crystal structure. The LVP/C particles are uniformly covered with a dual-phase carbon layer composed of amorphous carbon and graphitic carbon. The effect of the amount of anthracite on the battery performance of LVP as a cathode material has also been studied. The LVP/C composite obtained with 10 wt % anthracite (LVP/C-10) delivers the highest initial charge/discharge capacities of 186.1/168.2 mAh g-1 at 1 C and still retains the highest discharge capacity of 134.0 mAh g-1 even after 100 cycles. LVP/C-10 also displays an outstanding average capacity of 140.8 mAh g-1 at 5 C. The superior rate capability and cycling stability of LVP/C-10 is ascribed to the reduced particle size, decreased charge-transfer resistance, and improved lithium ion diffusion coefficient. Our results demonstrate that using anthracite as a carbon source opens up a new strategy for larger-scale synthesis of LVP and other electrode materials with poor electronic conductivity for lithium ion batteries.