Unraveling the Relationship between Ti⁴⁺ Doping and Li⁺ Mobility Enhancement in Ti⁴⁺ Doped Li₃V₂(PO₄)₃

Abstract

The electrochemical properties of Li3V2(PO4)3 (LVP) cathode of lithium ion batteries are often improved by ion doping. Nevertheless, the mechanism of ion doping has not been fully understood. Here, Ti4+ has been chosen as a typical dopant with similar atomic radius to the six-coordinated V3+. A series of Li3Ti x V(2–x)(PO4)3/C samples are successfully synthesized by a sol–gel route. The 7Li MAS NMR spectra of the LT x VP/C demonstrate that the doping of Ti4+ can enhance the mobility of Li ions. The results of electrochemical properties tests show that moderate Ti4+ doping is able to improve the high rate capability of the materials by increasing the electronic conductivity and Li-ion diffusion coefficient. The optimal sample (LT0.08VP/C) exhibits the best cycling behavior and rate capability, which can deliver 110.85 mAh/g and capacity retention of 99.36% at 10 C after 100 cycles. Electrochemical impedance spectroscopy results indicate that LT0.08VP/C possesses the minimum charge transfer resistance. The calculation results of cyclic voltammetry illustrate that the Li-ion diffusion coefficient of LT0.08VP/C has been improved. By combining the information extracted from a series of electrochemical characterizations and NMR tests, a structural model of Li+ vacancy is proposed to explain the improving of Li+ mobility.

Ultralong lifespan of SuperRedox Capacitor using Ti-doped Li3V2(PO4)3 cathode with suppressed vanadium dissolution

“…This enhanced rate performance can be attributed to two factors: (1) improvement in electronic conductivity due to the mitigation of inductive effects from Ti 4+ doping and (2) enhancement in Li + diffusion via the formation of vacancies at Li sites. 31…”

“…This result aligns with previous studies, which reported improved rate capacities of Ti 4+substituted LVP due to enhanced Li diffusion through the formation of Li vacancies. 27,31,40,41 Therefore, the higher capacity observed in Ti-LVP than LVP can be attributed to improved rate properties resulting from Ti 4+ substitution and the formation of Li vacancies.…”

“…This enhanced rate performance can be attributed to two factors: (1) improvement in electronic conductivity due to the mitigation of inductive effects from Ti 4+ doping and (2) enhancement in Li + diffusion via the formation of vacancies at Li sites. 31 To verify the suppression of electrolyte decomposition on the electrodes aer 10 000 cycles of the full cell, SEM observations and XPS analysis were conducted. Fig.…”

“…We chose Ti 4+ , Al 3+ , and Mn 2+ as the metal ions to be substituted. This choice is based on two main considerations: (i) stoichiometric substitutions with vanadium in LVP; 8,[31][32][33] (ii) the different valence and electronegativity values of these selected metals (V 3+ = 1.545, Ti 4+ = 1.730, Al 3+ = 1.513, and Mn 2+ = 1.343) 34 are expected to inuence the formation of V-O bonds within the material. In addition, this study includes a comprehensive examination of the capacity retention of the synthesized Li 3 V 2−X M X (PO 4 ) 3 materials with X ranging from 0.1 to 0.5.…”

Simultaneous defect regulation by p–n type co-substitution in a Na3V2(PO4)3/C cathode for high performance sodium ion batteries

“…4a. In order to describe the relationship between the potential E and the time T , Fick's second law is used as follows: 49–51 …”