Formation Mechanism of Nitrogen-Doped Titanium Monoxide Nanospheres and Their Application as Sulfur Hosts in Lithium Sulfur Batteries

Abstract

Lithium–sulfur batteries are one of the most promising next generation electrochemical devices with low cost and high energy density. Up to now, various metal oxides with strong interaction with lithium polysulfides (LiPs) have been designed as sulfur hosts to inhibit the notorious shuttle effect. Nitrogen doping on metal oxides can not only improve their shortcomings of poor electrical conductivity, but also introduce additional oxygen vacancies to further enhance their interaction with LiPs. In this work, the nitrogen-doped titanium monoxide (N–TiO) nanospheres have been first synthesized through a one-step method based on the synergistic effect of carbothermal reduction and nitridation reaction. The X-ray diffraction results suggested the gradually changed diffraction peak position, corresponding to the nitridation process. Through the calculation of Gibbs free energies in the temperature range of 800–1500 K, it was confirmed that TiO2 can directly transform to TiO and then to TiN. Moreover, the structural characterization and X-ray photoelectron spectroscopy results suggested the synthesized N–TiO nanospheres contain mixed valences of Ti4+, Ti3+, and Ti2+, together with a significantly increased O vacancy concentration. By using N–TiO/S as the cathode, a high initial capacitance of 1438 mA h g–1 at 0.2 C can be achieved, which was higher than those of the undoped TiO/S and TiN/S electrodes. In addition, such a cathode also delivered an initial discharge capacity of 1105 mA h g–1 at 2 C, and retained 474 mA h g–1 after 800 cycles, corresponding to the capacity decay rate of 0.071% per cycle. The strong interaction between O vacancies in N–TiO and LiPs, which has been confirmed through visible adsorption experiment and cyclic voltammetry curves of the Li2S6 symmetric cells, is the main reason for its excellent electrochemical performance. This work can provide new ideas for the preparation and application of N-doped metal oxide materials in the field of lithium–sulfur batteries.

Yttria-Stabilized Zirconia Nanoparticles─Carbon Nanotube Composite as a Polysulfide-Capturing Lithium–Sulfur Battery Separator

“…According to Figure S12, the oxygen vacancies seemed to have disappeared, which verifies that the vacant oxygen sites acted as the adsorption sites for sulfur to effectively capture polysulfides. Our observation agrees with the results from previous studies on sulfur adsorption on doped titanium oxide by Li et al and Tsou et al as well, which reported strong interaction between sulfur and metal ions at the vacant oxygen sites.…”

2D Co-doped MnCr2O4 nanosheets as efficient bifunctional cathode materials for long-life Li–O2 batteries

“…The strong binding between LiO 2 and MnCoCrO can make Li 2 O 2 more inclined to nucleation and grow at the active site by a surface mechanism, which effectively prevents Li 2 O 2 from dissolving into the electrolyte and contacting the organic electrolyte, suppressing parasitic reactions originating from LiO 2 nucleophilic attack, thereby providing excellent rechargeability and cycling stability. 4,14,79 At the same time, we further calculated the density of states (DOS) of the two materials to analyze the effect of heteroatom doping, as shown in Fig. S9 †.…”

Surface Crystal Modification of Na3V2(PO4)3 to Cast Intermediate Na2V2(PO4)3 Phase toward High‐Rate Sodium Storage

“…In contrast, in N‐NVP/N‐CP or N‐NVP/N‐CN system, NH 3 gas was trapped by the enclosed carbon hollow shell, forming a “nano gas chamber”, leading to a high concentration of NH 3 gas in the chambers, which was confirmed by the slower mass losing in TGA test of N‐NVP/N‐CP or N‐NVP/N‐CN compared to NVP/N‐CB (Figure S16, Supporting Information). Thus, the increased kinetic energy of NH 3 molecule was endowed to increase collision activation energy [ 45 ] with NVP during calcination, which triggered the N‐doping in the lattice of NVP.…”