Synthesis And Performance Of Li₃V₂（PO₄）₃/C Cathode Materials For Lithium-ion Batteries

Monolic Li3V2(PO4)3(LVP) has been extensively researched as a new promisingcathode material proposed for lithium-ion batteries due to its high operating voltageand theoretical specific capacity, and stable structure. In this work, the Li3V2(PO4)3/Ccomposite materials have been synthesized and the electrochemical performance hasalso been researched.1. Li3V2(PO4)3/C composite materials have been synthesized via a lowtemperature solid-state route with different heat treatments. It shows that the inintialdischarge specific capacity of LVP1/C (pre-sintering at350℃) is larger than that ofLVP2/C (without pre-sintering) both in the ranges of3.0-4.3V and3.0-4.8V.However, excellent rate capability and cyclic performance are presented by the twosamples in the range of3.0-4.3V. At3C, the initial discharge specific capacities ofLVP1/C and LVP2/C are103.9and99.9mAh g-1in the range of3.0-4.3V,respectively. And at10C, the initial discharge capacities of99.8and95.9mAh g-1arekept, respectively.95.8and90mAh g-1are still obtained in the300th cycle at10C,respectively.2. The optimal preparation conditions of the low temperature solid-state routehave been obtained. The raw materials were dispesed into deionized water andball-milled for4h, then a certain amount of C6H12O6·H2O (producing the carbonabout11.5%) and the mixture above were dispesed into ethanol and ball-milled for1h, and in the end the precursor was sintered at700℃for6h to obtain the productwith excellecnt electrochemical performance.3. LVP/C was prepared in the optimal preparation conditions by the lowtemperature solid-state route, and it was ultrasonically treated for20and60min,respectively. It shows that the particles decrease, and the specific surfaces increasewith the increase of the ultrasonica treatment time. At3C, the cyclic performance isthe best for the sample ultrasonically treated for20min compared with the other twosamples in200cycles in the range of3.0-4.3V. At the same rate, the dischargespecific capacity deceases sharply for the sample ultrasonically treated for60min inthe range of3.0-4.3V. However, excellent cyclic performance is presented for the sample, and only10.2mAh g-1is lost from201to850cycles.4. Three reactants dispersion methods have been attempted. Among, disperingthe raw materials into deionized water and stirring at room temperature to prepareprecursor has the advantage of liquid dispersion, and calcining the precursor tosynthesize the LVP/C with good electrochemical performance by a low temperaturequasi-solid state method. The initial discharge specific capacities of the sample are128.1,123.7and109.6mAh g-1at0.5,1and3C in the range of3.0-4.3V,respectively. The retention of the sample reaches97.1%at1C in the500th cycle, and89.5mAh g-1is still kept at3C in the500th cycle.5. LVP/C composite materials have been synthesized using polyvinyl alcohol(PVA) and polyethylene glycol (PEG) as carbon sources, respectively. The LVP/Cusing PVA as carbon source presents excellent electrochemical performance.106.4mAh g-1is released at1C in the510th cycle in the range of3.0-4.3V. At3C, thecapacity loss is only10.3%in the580th cycle and84mAh g-1is deliveried in the850th cycle.