Optimization of Rate Capability and Cyclability Performance in Li₃VO₄ Anode Material through Ca Doping

Abstract

A series of Ca-doped lithium vanadates Li Ca VO (x=0, 0.01, 0.03, and 0.05) are synthesized successfully through a simple sol-gel method. XRD patterns and energy-dispersive X-ray spectroscopy (EDS) mappings reveal that the doped Ca ions enter into the lattice successfully and are distributed uniformly throughout the Li VO (LVO) grains. XRD spectra and SEM images show that Ca doping can lead to an enlarged lattice and refined Li VO particles. A small quantity of V ions will transfer from V to V in the Ca-doped samples, as demonstrated by the X-ray photoelectron spectroscopy (XPS) analysis, which leads to an increase of an order of magnitude in the electronic conductivity. Improved rate capability and cycling stability are observed for the Ca-doped samples, and Li Ca VO exhibits the best electrochemical performance among the studied materials. The initial charge/discharge capacities at 0.1 C increase from 480/645 to 527/702 mA h g as x varies from 0 to 0.03. The charge capacity of Li Ca VO at 1 C retains 95.3 % of its initial value after 180 cycles, whereas the capacity retention is only 40 % for the pristine sample. Moreover, Li Ca VO maintains a high discharge capacity of 301.7 mA h g at a high discharge rate (4 C), whereas the corresponding value is only 95.2 mA h g for the pristine LVO sample. The enhanced cycling and rate performances are ascribed to the increased lithium ion diffusivity and electrical conductivity induced by Ca doping.

Partial surface phase transformation of Li3VO4 that enables superior rate performance and fast lithium-ion storage

“…Figure 4a shows the XPS data for Li 3 VO 4 , in which the signals located at binding energies of 517.7 and 525.2 eV matched well with those for V 2p 3/2 and V 2p 1/2 of V 5+ , as reported in literature [17,27,28]. The weak peak at 523.5 eV is in line with an X-ray satellite signal of O 1 s [27][28][29] [2,29]. The appearance of the low valence state demonstrates that V 5+ was reduced by carbon matrix during the heat-treatment process in inert atmosphere, in accordance with our XRD and HRTEM analyses.…”

“…To make sure that partial phase transformation occurred at surface, XPS was employed to study the surface chemical states and chemical components. Figure 4a shows the XPS data for Li 3 VO 4 , in which the signals located at binding energies of 517.7 and 525.2 eV matched well with those for V 2p 3/2 and V 2p 1/2 of V 5+ , as reported in literature [17,27,28]. The weak peak at 523.5 eV is in line with an X-ray satellite signal of O 1 s [27][28][29] [2,29].…”

“…By contrast, for the sample with a conductive layer, both reduction peaks were shifted to 0.518 and 0.821 V, respectively. The higher lithiation voltage of LL@C-600 compared to that of LVO indicates a lower barrier potential, as concluded elsewhere [19,28,34]. For the anodic segment, the anodic peak of LVO at 1.386 V is attributed to the delithiation process of Eq.…”

Sub-micro droplet reactors: Green synthesis of Li3VO4 anode materials for lithium ion batteries

“…This in turn yields a strong interface between the active materials and electrolyte, leading to a higher reaction area and shortening of the Li + ion movement pathway. 16,36,37 Such increase in the surface area can be explained as follows. When doping Ca, the foreign atoms act as a modifying agent, which changes not only the surface energy but also the mobility and reaction kinetics as they exhibit different hydration energy and diffusivity when compared to Li + ions.…”

Eu3+‐Activated Gd8V2O17: Energy Transfer, Luminescence, and Temperature‐Dependence Characteristics

“…Vanadates have been demonstrated to have many applications in different technical fields, such as optical lasers,e lectrochemistry devices, biology materials, medicine, electronic industry etc. [1][2][3] Especially as ak nown phosphorescent representative, the luminescence of vanadate materials has been intensively investigated in the past years. [4] Rare-earth (RE)i ons-activated vanadate phosphors usually present efficient luminescence even at ambient atmosphere due to the optically active VO 4 groups and the low-site symmetry of the RE activators in the host.…”