Study On Sodium Storage Properties Of Plasma Modified Titanium Dioxide Nanomaterials

In recent years,as environmental destruction and of people's use of energy increases dramaticly,the exploration for new energy storage materials has become the subject of scientists.Lithium-ion battery(LIBs),which has been extensively studied in the past,has increased exploitation cost due to the scarcity of lithium resources,which makes researchers pay more attention to environmentally friendly and cost-effective sodium-ion battery(SIBs).As a SIBs anode material,titanium dioxide(TiO₂)is an ideal candidate due to its stable properties,high safety and moderate theoretical capacity(335mAhg^-1),although its theoretical capacity is lower than that of transition metal oxides such as Fe₂O₃ and SnO₂.However,the intrinsic conductivity of TiO₂ is poor and the ion diffusion ability is weak,which could lead to the low capacity of TiO₂-based batteries and unsatisfactory rate performance.Therefore,modification of TiO₂ devoted to improve its electrical conductivity so as to improve the electrochemical performance is urgent.Plasma enhanced chemical vapor deposition(PECVD)technology is a environmentally effective surface modification method,where high energy electron of plasma can promote reaction powerfully.While unique fluidized-bed plasma-enhanced chemical vapor deposition(FB-PECVD)process can provide high energy in the reaction and simultaneously bring about excellent heat and mass transfer and uniform surface coating.Based on this,plasma modified titanium dioxide nanomaterials were designed in this paper by means of compositing with conductive materials,doping nitrogen atoms and designing oxygen defect so as to promote the sodium storage properties of TiO₂.Firstly,an effective and feasible carbon coating strategy was adopted to solve the bottleneck of low conductivity of TiO₂.Carbon coated TiO₂ composite nanomaterials were synthesized by fluidized-bed plasma-enhanced chemical vapor deposition(FB-PECVD).Plasma treatment brings out an amorphous carbon layer abundant in defects.The thickness of the lamella is about 6nm.The carbon layer is not only conducive to electron motion,significantly improving the conductivity of TiO₂ and the ratio discharge property of the material,but also,the Ti-C bond formed on the TiO₂/C interface makes the structure of TiO₂@C more stable and enhances electronic coupling between TiO₂ and carbon.The specific discharge capacity of TiO₂@C composite at 50mAg^-1 is 290.2mAhg^-1,1.5 times of the pristine TiO₂ electrode.On the other hand,nitrogen-doped TiO₂ nanomaterials(N-TiO₂)with nitrogen content of 5.99 at% were designed by FB-PECVD process.With urea as the nitrogen source,nitrogen was favourably incorporated into the TiO₂ crystal under the reaction of ammonia/argon/hydrogen plasma.Ti-N increases the electron transfer rate,and nitrogen doping promotes the formation of Ti³⁺,which is to the benefit of the improvement of electrical conductivity and the extraction and intromission of ions.The N-TiO₂ composite electrode provides a reversible capacity of 197mAhg^-1at a current density of 50mAg^-1.Finally,black anatase phase TiO₂ nanomaterial(b-TiO₂)was producted by plasma-enhanced chemical vapor deposition(PECVD)process.Argon/hydrogen plasma treatment can ameliorate the dynamics of electron motion of the material and improve the transport capacity of sodium ions due to oxygen vacancy.The b-TiO₂ electrode provides a reversible capacity of 203.8mAhg^-1 at 50mAg^-1,19% more than the pristine TiO₂ electrode.