Nitride materials offer a promising chemistry for alternative anode materials in Li-ion batteries, yet limited efforts have been made in this field. This work investigates the electrochemical activity of Fe3+/Fe4+ redox couple in the lithiated iron nitride Li3FeN2, positioning Li3FeN2 as a new high-capacity and low-cost anode for Li-ion batteries. The best synthesis conditions have been developed at 750 degrees C under nitrogen flow and mastering the particle size of iron precursor around 1 mu m has been revealed as the key point. Orthorhombic shaped Li3FeN2 crystals with 5-10 mu m length, 2 mu m width are obtained. Despite a complex delithiation-lithiation process involving four phases, Li3FeN2 demonstrates an attractive initial discharge capacity of 250 mAh g-1 near 1.2 V at C/10 within the 1.6 V-0.9 V range. The capacity retention limited to 83-87 % over 80 cycles depending on the C rate, has been improved to 89-97 % when the upper cutoff voltage is lowered from 1.6 V to 1.5 V. The cycling properties of Li3FeN2 are discussed in terms of rate capability, cycling limits and ageing time in the charged state. With a stable capacity of 180 mAh g-1, 140 mAh g-1 and 110 mAh g-1 at C/10, C/2 and 1C, respectively, available at 1.2 V, Li3FeN2 could compete the benchmark Li4Ti5O12 anode operating 300 mV higher than Li3FeN2. Further research is required to understand and solve the capacity loss observed during the first two cycles and to take into account the possible Fe4+ instability.

In this study, the gamma'-V2O5 cathode material was prepared through a solution synthesis technique leading to homogeneous, fine and porous particles 100-200 nm in size. This successful preparation allows to overcome the huge drawback of the microsized material in terms of charge efficiency and to take benefit of the attractive Na insertion properties of gamma'-V2O5, i. e. a significant available capacity of 145 mAh g(- 1), a high working potential of about 3.25 V vs. Na+/Na, an excellent charge efficiency, a high-rate capability and good cycle life. A detailed structural study upon Na insertion/extraction shows that the proposed nanosizing approach promotes a homogeneous Na solubility and solid solution behavior in a wider composition range (0.4 < x <= 1 in gamma-NaxV2O5) compared to the results previously reported for solid-state synthesized gamma'-V2O5. Furthermore, highly reversible structural changes are evidenced. Key kinetic parameters governing the Na insertion-extraction reaction are discussed thanks to an impedance spectroscopy study revealing a faster Na diffusivity in the one-phase region. The obtained results allow a comprehensive understanding of the enhanced performance exhibited by the present sub-micronic gamma'-V2O5 material.

Electrochemical potassium-ion insertion in high pressure /high temperature (HP/HT) β-V2O5 polymorph is examined for the first time. Monoclinic HP/HT β-V2O5 delivers a high reversible capacity of 120 mAh g−1 at C/20 rate corresponding to the K0.8V2O5 composition, at an average discharge potential of 3.2 V vs. K+/K. A good cycling performance is achieved over at least 175 cycles at C/5 rate at room temperature, confirming HP/HT β-V2O5 is an efficient host material for K+ insertion-extraction reaction. First insight into the reversibility of the structural changes upon potassiation is given.

Electrochemical lithium (de)intercalation in an atomic layer deposited (ALD) TiO 2 anatase thin film deposited on a planar Si /Al 2 O 3 /Pt substrate is investigated by Raman spectroscopy. An initial discharge capacity of 63 µAh cm −2 µm −1 (0.5 Li + mole −1 ) is reached at C/10 rate, which increases up to 77 µAh cm −2 µm −1 upon further cycles. An excellent capacity retention is achieved over at least 100 cycles, showing the good adherence of the ALD thin film. Raman spectra of Li x TiO 2 (0 ≤ x ≤ 0.5) thin film electrodes point to the nucleation of the orthorhombic lithiated titanate (LT) Li 0.5 TiO 2 phase from x = 0.1. This LT phase coexists with tetragonal TiO 2 in the 0.1 ≤ x ≤ 0.4 composition domain to be pure for x = 0.5. A fully reversible transformation from orthorhombic LT to tetragonal TiO 2 is observed upon the charge. The high quality of the Raman spectra allows identifying for the first time 12 modes in the 100–800 cm −1 region for the electrochemically formed LT phase. Furthermore, an appropriate Raman spectra analysis allows a reliable and quantitative determination of the thin film composition during discharge and charge. These results illustrate Raman spectroscopy is a powerful probe to scrutinize the Li insertion/extraction mechanism in TiO 2 thin films.

Lithium-ion batteries (LiBs) based on insertion electrodes reach intrinsic capacity limits. Performance im-provements and cost reduction require alternative reaction mechanisms and novel battery chemistries such as conversion reactions and sodium-ion batteries (NaBs), respectively. We here study the formation of Ti1-xVxH2 hydrides (0 <= x <= 1) and their electrochemical properties as anodes in LiBs and NaBs half-cells. Hydrides were synthesized by mechanochemistry of the metal powders under hydrogen atmosphere (PH2 similar to 8 MPa). For V contents below 80 at. % (x < 0.8), single-phase pseudobinary dihydride compounds Ti1-xVxH2 are formed. They crystallize in the fluorite-type structure and are highly nanostructured (crystallite size <= 10 nm). Their lattice parameter decreases linearly with the V content leading to hydride destabilization. Electrochemical studies were first carried out in Li-ion half cells with full conversion between Ti1-xVxH2 hydrides and lithium. The potential of the conversion reaction is gradually tuned with the vanadium content as result of the hydride induced destabilization. Furthermore, different paths for the conversion reaction are observed for Ti-rich (x <= 0.25) and V-rich (x >= 0.7) alloys. Na-ion half-cell measurements prove the reactivity between (V, Ti)H2 hydrides and sodium, albeit with significant kinetic limitations.(c) 2023 Elsevier B.V. All rights reserved.

Due to its great theoretical capacity (147 mAh g −1 ) and high operating potential (4.7 V vs Li + /Li), Co‐free spinel LiNi 0.5 Mn 1.5 O 4 (LNMO) is one of the most promising thin film cathodes allowing designing Li‐ion micro‐batteries with a high specific energy. In this work, the Li extraction–insertion mechanism in sputtered LNMO thin films is investigated by X‐ray diffraction and Raman spectroscopy during the first electrochemical cycle. A one‐step phase transition involving two cubic phases is revealed, consisting of a wide solid solution region (0.3 ≤ x ≤ 1 in Li x NMO) and a narrow biphasic domain (0 < x ≤ 0.3). Remarkably, significant variations are observed in the Raman spectra, which are linked to the activity of the Ni redox system at 4.7 V. It is demonstrated that an appropriate analysis of the bands corresponding to pure Ni–O stretching modes leads to an accurate estimation of the electrode states of charge and depth of discharge, which opens the way for a reliable quantification of the self‐discharge phenomenon. The mechanism of Li extraction insertion here pictured for the first time for LNMO thin layers is consistent with their disordered nature and accounts for their good electrochemical performance.

Electrochemical properties of the puckered layered gamma'-V2O5 polymorph as a cathode material in a nonaqueous Zn metal cell using the acetonitrile-Zn(CF3SO3)(2) electrolyte are investigated here for the first time. A typical galvanostatic profile in the 2-0.3 V vs Zn2+/Zn voltage range shows a sloping discharge curve involving a capacity of 130 mAh g(-1) at C/20 in one single step centered at 0.9 V vs Zn2+/Zn. The structural response of gamma'-V2O5 during the discharge-charge cycle is investigated by ex situ X-ray diffraction (XRD) and Raman spectroscopy. Up to 0.41 Zn mol(-1) can be accommodated between the gamma'-V2O5 layers, inducing only a moderate interlayer expansion of +6.4%, comparable to that found for Li+ insertion. Remarkably, the insertion process is fully reversible in spite of the high charge density of Zn2+. Good cycle life can be achieved at a moderate rate, with a stable capacity of nearly 130 mAh g(-1) available at 0.9 V vs Zn2+/Zn over at least 60 cycles. The peculiar structural features of the new electroformed Zn0.41V2O5 bronze highlight the interest of the gamma'-V2O5 polymorph to mitigate the expected large deformation upon electrochemical divalent Zn2+ incorporation.

Micro-batteries are attractive miniaturized energy devices for new Internet of Things applications, but the lack of understanding of their degradation process during cycling hinders improving their performance. Here focused ion beam (FIB)-lamella from LiMn1.5 Ni0.5 O4 (LMNO) thin-film cathode is in situ cycled in a liquid electrolyte inside an electrochemical transmission electron microscope (TEM) holder to analyze structural and morphology changes upon (de)lithiation processes. A high-quality electrical connection between the platinum (Pt) current collector of FIB-lamella and the microchip's Pt working electrode is established, as confirmed by local two-probe conductivity measurements. In situ cyclic voltammetry (CV) experiments show two redox activities at 4.41 and 4.58/4.54 V corresponding to the Ni2+/3+ and Ni3+/4+ couples, respectively. (S)TEM investigations of the cycled thin-film reveal formation of voids and cracks, loss of contact with current collector, and presence of organic decomposition products. The 4D STEM ASTAR technique highlights the emergence of an amorphization process and a decrease in average grain size from 20 to 10 nm in the in situ cycled electrode. The present findings, obtained for the first time through the liquid electrochemical TEM study, provide several insights explaining the capacity fade of the LMNO thin-film cathode typically observed upon cycling in a conventional liquid electrolyte.

Li-on battery (LIB) is an important technology which is widely used in portable electronic devices, electric vehicles (EV) and other energy storage applications. Commercial LIB has multiple choices as positive electrode materials such as layered transition metal oxides (LiCoO2, LiNi1-y-zMnyCozO2...), spinel oxides LiNixMn2-xO4 as well as olivine LiFePO4. Conversely, the selection of negative electrodes is mainly limited to graphite or Li4Ti5O12 (LTO). Graphite is inexpensive and delivers large capacity but suffers from the formation of solid electrolyte interphase (SEI) as well as Li dendrites formed at high rate, leading to low rate capability and security problems [1]. Li4Ti5O12 (LTO) on the other hand, is able to circumvent the problems of graphite thanks to its higher working potential (1.5 V vs Li+/Li) and minimal structural change during lithiation [2]. However, LTO has a lower energy density than graphite due to a higher working potential and a moderate specific capacity (∼150 mAh g− 1 and 120 mAh g− 1 at 1C and 5C rate, respectively). Therefore, there is a strong need of researching large-capacity insertion-based negative electrode materials working in the 1.0 < V ≤ 1.5 V voltage range to design new generation high energy density full cells. Transition-metal nitrides are considered to be among the most promising class of anode materials for LiBs [3]. Within this family, Li7MnN4 (LMN) [4] with an anti-fluorite 3D structure has received great attention due to its large specific capacity of 280 mAh g-1, excellent cycle stability and appropriate working potential of 1.2 V. We previously showed this material prepared at high temperature exhibits very large particle size [4]. Therefore, a crucial post-synthesis ball-milling step was required to benefit from the maximum capacity and high rate capability. However, this ball-milling step is hard to reproduce due to its dependence on many instrumental factors such as jar geometry, ball/material mass ratio [4]. In this work, an optimization of the synthesis conditions of LMN is proposed and new key parameters controlling the particle size distribution (PSD) are identified, allowing the suppression of the post-synthesis ball-milling process. Thanks to the specific morphology attained when using our optimized synthesis conditions, the as-synthesized LMN material is able to deliver larger capacity at higher rate (265 mAh g− 1 and 160 mAh g− 1 at 1C and 5C rate, respectively). These capacity values are the best to our knowledge and compete with that of benchmark LTO. Furthermore, the lower working potential of LMN (1.2 V, i. e. 0.35 V lower than LTO) is expected to provide larger energy density in a full cell device compared to LTO. To carry this argument further, NMC/LMN full cell is constructed for the first time with LiNi0.6Mn0.2Co0.2O2 and pre-delithiated LMN (Li5.3MnN4). This NMC/LMN coin cell is applied for galvanostatic cycling at different current densities while a 3-electrode cell using metallic Li as reference electrode is used to clarify potential changes during the charge-discharge process. We show the NMC/LMN full cell replicates the electrochemical performance of NMC/Li half-cell in the 3.2 V - 2 V potential window. These results prove the feasibility and compatibility of the NMC/LMN full cell and the suitability of delithiated LMN as negative electrode material. Remarkably, the maximum energy density of the NMC/LMN full cell, of 256 Wh/kg(based on total active materials mass loading), is 30% to 50% higher than that exhibited by a NMC/LTO full cell. [1] T. Waldmann, B. I. Hogg, and M. Wohlfahrt-Mehrens, “Li plating as unwanted side reaction in commercial Li-ion cells – A review,” J. Power Sources, vol. 384, no. November 2017, pp. 107–124, 2018. [2] T. Ohzuku, A. Ueda, and N. Yamamoto, “Zero‐Strain Insertion Material of Li [ Li1 / 3Ti5 / 3 ] O 4 for Rechargeable Lithium Cells,” J. Electrochem. Soc., vol. 142, no. 5, pp. 1431–1435, 1995. [3] J. M. Tarascon and M. Armand, “Issues and challenges facing rechargeable lithium batteries,” Mater. Sustain. Energy A Collect. Peer-Reviewed Res. Rev. Artic. from Nat. Publ. Gr., vol. 414, no. November, pp. 171–179, 2010. [4] E. Panabière, N. Emery, S. Bach, J. P. Pereira-Ramos, and P. Willmann, “Ball-milled Li7MnN4: An attractive negative electrode material for lithium-ion batteries,” Electrochim. Acta, vol. 97, pp. 393–397, 2013. Figure 1

LiMn2-xNixO4 spinel phases, with their almost flat electrochemical curves composed of two plateaus around 4.7 V vs Li+/Li separated by a voltage difference Delta V of 20-60 mV, are good candidates for high power applications. The Ni/Mn order is one of the key parameters in understanding the electrochemical curve shape. In this work, the Ni/Mn order in the nickel-rich region of the spinel LiMn2-xNixO4 solid solution (0.38 <= x <= 0.50) has been investigated using time-of-flight powder neutron diffraction (TOF-PND) and density functional theory (DFT) calculations. For LiMn2-xNixO4 solid-solution samples prepared between 700 and 900 degrees C, Ni/Mn ordering was found to be retained to room temperature by systematic broadening of diffraction peaks with hkl indexes of mixed even/odd parity. This broadening is due to the increasing density of a planar defect called antiphase domain boundaries (APBs). DFT calculations performed on several Ni/Mn defective configurations and TOF-PND Rietveld refinement indicate that the {100} orientation of the APB boundary is the most probable. Hence, in the whole composition range, a unique ordered spinel phase within the space group P4(3)32, with a single hkl-dependent parameter to represent the APB crossing probability, gives a measure of the Ni/Mn order coherence length. We show that this defect density is driven by the synthesis temperature and the nickel content of the spinel phase. A correlation between the synthesis condition effect on the local ordering and the voltage profile is given for two Ni/Mn initial ratios (0.4/1.6 and 0.5/1.5). The influence of the synthesis temperature on these two compositions is drastically different: for LiMn1.6Ni0.4O4, with a similar APB domain size whatever the temperature, only a slight variation of AV is observed. Reversely, for LiMn1.5Ni0.5O4, a strong increase of the AV with the synthesis temperature is evidenced, concomitant with a decrease in the APB domain size and the Ni content.

In-Situ Cycling In article number 2100891, Demortiére and co-workers demonstrate that in-situ cycling of a LiMn1.5Ni0.5O4 thin-film cathode in an electrochemical transmission electron microscope (TEM) holder reveals structural and morphologic changes upon (de)lithiation processes. (S)TEM images of the cycled thin-film reveal the formation of voids, cracks, and organic decomposition products. The 4D STEM ASTAR technique highlights the emergence of an amorphization process in the in-situ cycled electrode.

All solid state Li-ion micro-battery is a promising candidate to power miniaturized sensors for Internet of things (IOT) and other electronic devices. In recent times, the spinel LiMn1.5Ni0.5O4 (LNMO) has demonstrated as a potential positive electrode material for Li-ion thin film batteries offering a theoretical capacity of 147 mAh/g (65 µAh/cm2/µm for a bulk density of 4.47 g/cm3) and operates up to now at the highest potential (around 4.7 V vs. Li+/Li) [1]. In this work, we report our first successful in situ TEM attempts to observe the morphological, structural and interfacial changes in the positive electrode layer of FIB prepared sample which undergo after cycling using liquid electrolyte. More precisely we compared the morphological and structural evolution between a pristine and cycled microbattery by 4D STEM-ASTAR technique to highlight the key information to improve the deposition conditions that will enhance the reliability and production quality of such micro power devices. The in situ cycling in liquid TEM has given this opportunity to study the battery electrode materials so as to spot the slightest modifications of the materials resulting in important advances in knowledge on electrochemical energy storage [2-3]. Here, our approach is based on the cycling a FIB lamella sample inside the TEM using liquid-electrochemical TEM holder with conventional liquid electrolyte (1M LiClO4, EC: DMC 1:1). The cross-section image of as prepared FIB sample with homogeneous deposition of distinctive layers of different thickness [from bottom to top-Si (0.385mm)/ Al2O3 (100nm)/ Pt (630nm) / LNMO (400nm)] is shown in figure 1a. The Pt current collector of FIB lamella sample is connected to the Pt working electrode on the e-chips used for TEM study (figure 1b). First, using FIB preparation technique, we sliced a full 2-D “thin film micro-battery” making it as thin to observe/analyse under TEM. Then, we modified the FIB lamellar design using FIB-SEM tool to get good electrical contact and reduced polarisation. Several technological problems have to be overcome in the process. For the instance, it is mandatory to obtain a good electrical contact between the Pt working electrode of e-chip and Pt current collector of FIB lamellar, which is later achieved by depositing extra Pt between the two contacts forming a platinum bridge. A 4-Probe electrical conductivity performed locally confirms the good electrical contact between the as prepared FIB lamella sample and Pt working electrode of e-chip. The cross-section bright field TEM image of a final modified version of FIB lamella sample used in the study is shown in figure 1d. The FIB lamella sample is then later cycled inside the liquid electrochemical TEM holder (fig 1c) in potential window of 4.1 V-4.8 V vs. Li+/Li. The flow of the electrolyte (LiClO4 EC:DMC 1:1) inside the TEM holder was further controlled by microfluidic controller with the flow rate of 2 µL/min. CV was recorded at a sweep rate of 0.1mV/s and two plateaus at 4.4 V and 4.6 V was observed corresponding to Ni2+/3+ and Ni3+/4+ oxidation respectively (Fig 1f). The basic redox steps observed during the charge are same as observed in the case of cycling bulk 2D thin film in a homemade flat cell. The comparison between the cycled and pristine microbattery sliced by FIB and observed by TEM allowed us to clearly demonstrate the formation of cracks inside the LMNO layer, loss of contact between the LMNO layer and the platinum current collector, as well as the agglomeration of the organic compounds produced due to the electrolyte decomposition. Moreover, 4D STEM-ASTAR technique provided us with the crucial information regarding the grain size reduction from 20 nm in pristine to 12 nm in cycled sample, confirming the continuous electrode-electrolyte reaction happening over the cycling. Also, the decrease in crystallinity and increase in the amorphization of the LMNO grains by 38 % in the cycled sample compared to pristine as shown in figure 1e and g clearly prove the fast capacity fading phenomenon observed in bulk microbattery. Furthermore, a thickness of ~20nm along the platinum layer, a (111) preferred orientation is observed exhibiting the epitaxial effect of LMNO on platinum layer which has been further supported by the precision electron diffraction (PED) recorded on both LMNO and platinum grains. References: [1] M. Hallot, A. Demortière, P. Roussel, C. Lethien, Energy Storage Materials, (18)30779-7 [2] O.M. Karakulina, A. Demortière, W. Dachraoui, A.M. Abakumov, J. Hadermann, Nano lett. 18(2018) 6286-6291. [3] L. Lutz, W. Dachraoui, A. Demortière, L. R. Johnson, P. G. Bruce, A. Grimaud, J.M. Tarascon, Nano Lett. 18(2018), 1280-1289 Figure 1

The electronic structure of alpha-V2O5, gamma'-V2O5, and gamma-MeV2O5 (Me = Li, Na) bronzes is studied by quantum-chemical calculations completed by spectroscopic experiments. The calculations are performed using the G(0)W(0) method with the DFT+U self-consistent wave function as an initial approximation. The electronic band gap E-g = 2.89 eV calculated for alpha-V2O5 is found to be in fair agreement with available experimental data. The strategy was then applied to studying the electronic structure of the. gamma'-V2O5 phase and gamma-MeV2O5 bronzes for which no experimental band gap data exist in the literature. Computed E-g values are equal to 3.17, 1.21 and 1.18 eV for gamma'-V2O5, gamma-LiV2O5, and gamma-NaV2O5, respectively. The nature of the alkali metal atom is determined to have little influence on the structure and electronic states of the bronzes. Raman spectra recorded with different wavelengths of exciting radiation have allowed the determination of the energy threshold corresponding to the transition from off-resonance to resonance Raman scattering process. In this way, a band gap value in the range 2.54-2.71 eV for alpha-V2O5 and gamma'-V2O5 is obtained in good agreement with the experimental values for the alpha-phase. Raman spectra of gamma-MeV2O5 suggest the band gap smaller than 1.58 eV in these materials, whereas the photoluminescence measurements yield E-g approximate to 0.95 eV for the gamma-LiV2O5 bronze. Remarkably, the result of the G(0)W(0) calculations lies in between the experimental estimates. The strong similarity of structures and electronic states of gamma-LiV2O5 and gamma-NaV2O5 accounts for their the same operating voltage when used as cathodes in Li(Na)-ion batteries.

The recent intensive research for cathode materials beyond Li-ion batteries has revitalized interest in V2O5 due to its high reversible capacity. Among the various polymorphs, gamma'-V2O5 exhibits a unique corrugated layered structure that promotes the insertion of guest species. However, when used as cathode material for SIB, this material suffers from a 50% first charge efficiency that prevents the full benefit of its high discharge capacity of 140 mAh g(-1). Herein, we demonstrate and explain the effectiveness of a ball-milling approach to overcome this strong limitation. Several positive impacts of particle size reduction are highlighted: the charge efficiency is increased to 90%, allowing a 2-fold enhancement of the available capacity upon cycling (120 mAh g(-1) after 50 cycles at C/2). The Na insertion mechanism investigated by XRD and Raman spectroscopy shows a peculiar behavior with wide solid solution domains at the expense of the diphasic region. The kinetics study reveals a faster diffusivity in the ball-milled material and enhanced Na diffusion in the single-phase region. Both structural and kinetic reversibility account for the high performance here achieved for gamma'-V2O5: a high working voltage of 3.2 V vs Na+/Na, a high rate capability, excellent charge efficiency and good cycle life.

K-ion batteries (KIBs) are receiving increasing interest because of their low K+/K redox potential and reduced cost. This emerging alternative is, however, strongly dependent on the development of cathode materials with a suitable structure for accommodating K+ ions. We show here the promising properties of the puckered layered gamma'-V2O5 polymorph that inserts up to 0.9 K+ mol(-1) at 3.3 V versus K+/K at C/60. An initial depotassiation capacity of 72 mA h g(-1) corresponding to the exchange of 0.5 K+ ions is still delivered at C/10, and a reversible capacity of 48 mA h g(-1), stable over 100 cycles, is achieved in the 4.4-2.4 V voltage window. The reaction mechanism, investigated by X-ray diffraction and Raman spectroscopy, involves the formation on the first discharge of a new layered KxV2O5 host structure. The K0.78V2O5 bronze obtained at 2.4 V exhibits unfolded V2O5 sheets and an unexpected moderate expansion of the interlayer spacing compared to gamma'-V2O5. Depotassiation-potassiation reversibly occurs within KxV2O5 (0.3 <= x <= 0.78) with less than 2% breathing. Such findings demonstrate the remarkable structural flexibility of gamma'-V2O5 to accommodate the large-sized K+ ions and illustrate the richness of V2O5 polymorphs as positive electrode materials for KIBs.

Aqueous rechargeable zinc batteries are getting increasing attention for large-scale energy storage owing to their advantages in terms of cost, environmental friendliness and safety. Here, the layered puckered gamma'-V2O5 polymorph with a porous morphology is firstly introduced as cathode for an aqueous zinc battery system in a binary Zn2+/Li+ electrolyte. The Zn parallel to gamma'-V2O5 cell delivers high capacities of 240 and 190 mAh g(-1) at current densities of 29 and 147 mA g(-1), respectively, and remarkable cycling stability in the 1.6 V-0.7 V voltage window (97% retention after 100 cycles at 0.15 A g(-1)). The detailed structural evolution during first discharge-charge and subsequent cycling is investigated using X-ray diffraction and Raman spectroscopy. We demonstrate a reaction mechanism based on a selective Li insertion in the 1.6 V-1.0 V voltage range. It involves a reversible exchange of 0.8 Li+ in gamma'-V2O5 and the same structural response as the one reported in lithiated organic electrolyte. However, in the extended 1.6 V-0.7 V voltage range, this work puts forward a concomitant and gradual phase transformation from gamma'-V2O5 to zinc pyrovanadate Zn3V2O7(OH)(2 center dot)2H(2)O (ZVO) during cycling. Such mechanism involving the in-situ formation of ZVO, known as an efficient Zn and Li intercalation material, explains the high electrochemical performance here reported for the Zn parallel to gamma'-V2O5 cell. This work highlights the peculiar layered-puckered gamma'-V2O5 polymorph outperforms the conventional alpha-V2O5 with a huge improvement of capacity of 240 mAh g(-1) vs 80 mAh g(-1) in the same electrolyte and voltage window. (C) 2021 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by ELSEVIER B.V. and Science Press. All rights reserved.