The Synthesis And Electrochemical Characterization Of Titanium-Vanadium Oxide Anode Materials

To be used as the anode of lithium ion batteries among the potential candidate transition metal oxides,what make titanium dioxide(TiO₂)under the spotlight attracting much attention is its intrinsic advantages,such as it's high natural abundance,low cost,barely environmental impact,and negligible lattice change(<4%)during lithiation/delithiation processes.However,its low practical capacity and poor rate performance for Li storage duo to it's slow Li⁺diffusion and low electronic conductivity in the bulk TiO₂ strictly limit the practical applications of TiO ₂ as an anode material.In this investigation,a new titanium-vanadium oxide-CNTs nanocomposite(Ti-m V-n CNTs)was successfully fabricated via an in-situ pyrolysis reaction of a novel and simple titanium-vanadium organic frame work polymer (Ti_mV_n(OCH₂CH₂O)_2(m+n)-l CNTs).The TiO₂/LHPC composite material was prepared by loading titanium dioxide crystal particles onto the surface of the hierarchical porous carbon from lignin(LHPC).In addition,various physical performance tests and electrochemical performance tests were carried out in order to obtain t itanium dioxide-based anode materials with excellent electrochemical properties.The main contents of this investigations are summarized as following:(1)The physical properties and charge-discharge performance of Ti-m V-n CNTs samples prepared at different pyrolysis temperatures,with different CNTs content,and with different dopant concentrations of vanadium ions were studied;(2)The electrochemical performance,lithium storage mechanism,and kinetic characteristics of the Ti-20V-9CNTs nanocomposite prepared under the optimal conditions were investigated;(3)The physical properties,electrochemical properties,and lithium storage mechanism of TiO₂/LHPC composite were discussed.The conclusions were summarized as follows:(1)Based on the charge and discharge performances of different Ti-m V-n CNTs samples,it was found that Ti-20V-9CNTs(prepared at 500?)that contains 13.10 wt% of CNTs and has a Ti to V atomic ratio of about 3.91:1 behaviors the best.(2)The Li ion diffusion property and electronic conductivity of Ti-20V-9CNTs was improved after the introduction of vanadia in Ti-20V-9CNTs;The cathodic and anodic processes of the Ti-20V-CNTs nanocomposite are partially dominated by the pseudocapacitive behavior and the pseudocapacitive charge storage performance is enhanced after the introduction of vanadia.(3)The Ti-20V-9CNTs nanocomposite exhibites excellent lithium storage properties as an anode in Li-ion battery.This material delivers an extraordinary high rate performance(350.0 and 220.0 m Ah g-1 at 0.10 and 5.0 A g-1,respectively)and remarkable long time cycling stability(negligible capacity decay at 0.10 A g-1 within 350 cycles).(4)The TiO₂/LHPC composite exhibites perfect rate capability,as an anode material in Li-ion battery.The specific capacities of TiO₂/LHPC are 365,289,200,140,91,and 64 m Ah g-1 at 0.1,0.2,0.5,1.0,2.0,and 3.0 A g-1,respectively.It displays a stable high capacity of 320 m Ah g-1 after 50 galvanostatic charge-discharge cycles at a current density of 0.1 A g-1.Moreover,TiO₂/LHPC composite exhibits excellent cycling stability(130 m Ah g-1 after 50 cycles at 1.0 A g-1 and ⁸9.2% retention after 500 cycles).The superior electrochemical properties of TiO₂/LHPC composite are mainly attributed to the perfect conductive carbon network and the high specific surface area of LHPC.