New Insights into the Structure Changes and Interface Properties of Li₃VO₄ Anode for Lithium-Ion Batteries during the Initial Cycle by in-Situ Techniques

Abstract

Li3VO4 has been regarded as a new-type anode of lithium-ion batteries in recent years, which has a high theoretical specific capacity of 394 mAh g(-1), a proper potential for Li(+) insertion/deinsertion (∼1 V), and a good rate capacity. However, its low initial Coulombic efficiency, poor conductivity, and poor cycle performance restricts its development. In order to figure out the cause of the low initial Coulombic efficiency of Li3VO4 material, the nanosized Li3VO4 material was synthesized by citric acid-assisted sol-gel method. The lithium storage behaviors of the prepared Li3VO4 material were studied by in-situ XRD and in-situ EIS techniques. In-situ XRD results indicated that there was irreversible phase transformation of Li3VO4 during the initial charging/discharging process. In-situ EIS experiment was performed during the potentiostatic intermittent titration technique (PITT) process to discuss the formation of the solid electrolyte interface (SEI) on the Li3VO4 and the kinetics of lithium-ion diffusion. It is worth pointing out that this is the first time to prove the existence of SEI on Li3VO4 during the initial charging/discharging process by in-situ EIS experiment. It turned out that the irreversible phase transformation and the formation of SEI on Li3VO4 were the two important reasons causing the low initial Coulombic efficiency of Li3VO4 material.

Metal–Organic Framework (MOF) Derived Electrodes with Robust and Fast Lithium Storage for Li‐Ion Hybrid Capacitors

“…Figure d presents the percent contribution of separate capacitive and diffusion‐controlled charge contributions measured at different scan rates. The Li‐ion diffusion coefficient in MnO 2 @C‐NS electrode was further estimated by the Randles–Sevick equationwhere i p is current maximum in amps (we considered current value at three points), n is number of electrons involved in the charge storage, A is electrode area in cm 2 (for simplicity we have considered geometrical area), D Li is diffusion coefficient in cm 2 s −1 , ν is scan rate in V s −1 , and C is concentration of Li‐ion in mol cm −3 . The diffusion coefficients for MnO 2 @C‐NS calculated at different points are in the range of 10 −9 ‐ 10 −11 cm 2 s −1 for different scan rates (see Figure S6b, Supporting Information).…”

Illumining phase transformation dynamics of vanadium oxide cathode by multimodal techniques under operando conditions

“…Further, to quantify the EIS results of different degrees of lithium insertion, a series of fittings were done, as shown in Fig. 7(b) [27]. The Nyquist plots were fitted by the two-time constant model ( Fig.…”

Insights into the Charge Storage Mechanism of Li3VO4 Anode Materials for Li‐Ion Batteries

“…Moreover, the experimental data show that this transformation may continue via an intermediate Phase II to the further lithiated Phase III. The XRD patterns of the Phase II and Phase III cannot be indexed due to the lack of crystallographic information; however, the disappearance of the intermediate Phase II on the first lithiation proposes a different lithiation mechanism from previous reports . Furthermore, the suggested antifluorite‐type Li 6 VO 4 (3.0 Li + ) structure at a deep lithiation level was not observed, probably because the LVO‐BM does not achieve full lithiation (3.0 Li + ) but only the nominal composition of Li 5.4 VO 4 (2.4 Li + ) in the present in situ experiments.…”

“…A clear trend in all experiments is observed: the irreversible specific charge “loss” in the first cycle is nearly constant at every C‐rate (C/30 and C/200) for the LVO‐BM electrodes. The irreversible specific charge “loss” in the first cycle can be associated mainly with irreversible phase transformation that the LVO material undergoes due to Li + insertion into the original structure and/or due to irreversible parasitic processes such as electrolyte decomposition and SEI formation . Based on the above results, the first hypothesis seems more plausible because there is no obvious dependence on time spent under highly reducing conditions (see Figure ).…”

“…Zhou et al . reported from their in situ XRD measurements over the 2 Θ range of 32°≤2 Θ ≤51° that two new phases appear at the same time at around 0.60 V and remain until the end of the first lithiation . One of the new phases is still visible at the end of the first delithiation at 3.0 V and attributed to the origin of the irreversible specific charge “loss” of LVO on the first lithiation .…”