LiMn1.5Ni0.5O4 is a high-voltage cathode material for Li-ion batteries. The effects of Ni/Mn ordering and nickel content on its electrochemical behavior remain ambiguous. DFT can provide essential insights into these phenomena. We benchmark four exchange-correlation functionals (PBE, PBE+U, r2SCAN, and HSE06) for LixMn1.5Ni0.5O4 (x = 1, 0.5, 0) against experimental data. We evaluate key properties: operating voltage, voltage differences between Ni3+/Ni2+ and Ni4+/Ni3+ redox couples, magnetic and crystallographic structures, structural response upon delithiation, and oxygen K-edge EELS spectra. PBE underestimates the average voltage (3.94 V vs. 3.73 V) and overestimates redox voltage differences (114 mV vs. 15 mV), but captures essential trends in structural and electronic properties at moderate computational cost. While PBE+U improves voltage accuracy, it predicts an unstable half-lithiated phase and incorrect magnetic configurations. r2SCAN yields mixed results. HSE06 provides the highest accuracy for some results but at significant computational expense. PBE emerges as the best compromise for modeling LixMn1.5Ni0.5O4 phases.

Thin native oxide films spontaneously formed on a series of cobalt-nickel alloys with varying cobalt concentrations were investigated using X-ray photoemission spectroscopy (XPS). Combining XPS with sequential ion abrasion allowed identification of the various oxides and hydroxides present within the passive layers, depending on their depth in the films, which do not exceed 5 nm. A recent study of the Co20Ni80 alloy showed that the surface layer is heterogeneous both laterally and in depth, with some regions covered by oxidized cobalt compounds and others by oxidized nickel compounds. Different oxide thicknesses were observed on the Co20Ni80 alloy compared to pure Ni and Co metals. In the present study, we investigate the thicknesses and compositions of cobalt and nickel oxide films in binary alloys Co x Ni100-x , with x = 0, 20, 50, 70, 90, and 100. Building on the previous study of Co20Ni80, where a surface galvanic effect induced by alloying was proposed, we show that variations in Co concentration suggest that the magnetic properties of the substrate influence the composition of the passivation layers formed on the cobalt-nickel alloys.

Understanding the mechanism of lithium transport within the structure are essential for developing solid-state electrolytes for all-solid-state lithium-ion batteries. Enriching the halide content in argyrodite is an effective strategy to increase its ionic conductivity, but the structure-property relationship for bromide argyrodite needs further investigation. This study focuses on Li7-xPS6-xBrx (1 <= x <= 1.7) compositions, synthesized by ball milling. Their structures and conduction pathways were revealed through synchrotron and neutron joint diffraction refinements combined with BVSE analysis. The main finding is that increasing Br content enhances anionic disorder and reduces ionic potential at the 4d site, inducing a reorganization of the Li+ polyhedral cage, described by T2 and T5 sites. This reorganization expands the lithium cage and shortens the T2-T2 intercage jump. Consequently, the facilitation of intercage jumps enhances the ionic conductivity, reaching 3.5 mS/cm for Li5.3PS4.3Br1.7. However, at high Br contents, complex interplay of limiting factors such as vacancies creation and intracage jump may contribute to the overall transport mechanism. Bromide content has a limited effect on the electrochemical properties of argyrodite. Still, a high Br content tends to slightly destabilize both the argyrodite | Li metal interface and the oxidative stability window.

Nanostructured tin phosphite SnHPO3 was prepared via high-energy ball milling of hydrothermally synthesized powder to investigate its potential as an anode material for lithium-ion batteries. The nanostructuration process significantly reduced particle and crystallite sizes without altering the crystallographic structure or chemical composition. Electrochemical tests demonstrate that nanostructuration lowers kinetic barriers for lithium-ion transport, enabling the complete conversion of SnHPO3 into Sn nanoparticles, thereby facilitating its full lithiation. This results in a high reversible specific capacity of 645 mAh g- 1 at 0.2 Cover 70 cycles, with a coulombic efficiency exceeding 99 %. Operando X-ray diffraction, along with ex-situ TEM and XPS characterizations, reveals the complex interplay between morphological features and electrochemical storage mechanisms. The obtained high capacity is not only attributed to the classical LixSn alloys formation but also to a surface-related supercapacitive contribution and a potential overoxidation of Sn during delithiation.

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.

XPS data processing for cobalt and nickel core-level peaks can be complicated. This is especially true when analyzing a mixture of oxide/oxyhydroxide/hydroxide compounds of these metals. The objective of this study is to develop a method for decomposing XPS spectra of 2p core levels for nickel and cobalt-oxidized compounds. This methodology was then employed to study the passivation layer of the Co20Ni80 alloy. The analysis of Ni2p and Co2p photo peaks using a homemade code based on core-level peak structure and satellites enables us to determine the chemical composition of the surface layer, knowledge of which is particularly important because it is directly linked to the anticorrosive properties it confers on the surface of the oxidized alloy. The XPS analysis, coupled with sequential ion sputtering, revealed that the passive layer of the Co20Ni80 alloy is heterogeneously covered with either oxidized cobalt compounds or oxidized nickel compounds. The method used also demonstrates that the chemical heterogeneity is associated with the thickness heterogeneity of the passive layer.

Argyrodites Li6PS5X (X = Cl, Br) have attracted growing interest due to their exceptional ionic conductivity and ductility, making them promising electrolytes for all-solid-state lithium-ion batteries. However, their poor electrochemical stability at very low potential limits the use of lithium metal as a negative electrode. Instead of using Li-In alloy, this study explores the electrochemical properties of lithium nitridonickelate Li2.07Ni0.62N as an alternative negative electrode material, paired with balled milled argyrodite Li6PS5Br. The same electrochemical storage mechanism observed in liquid media is at work here, exhibiting a solid-solution profile along with low lattice expansion through the reversible insertion mechanism. By adjusting the potential window to minimize argyrodite degradation, the active material delivered a stable capacity of 125 mAh g_ 1 over 60 cycles at C/25, with a mean working potential of 0.5 V at room temperature. The excellent capacity retention was achieved up to C/10, demonstrating good compatibility between the argyrodite solid electrolyte and lithium nitridonickelate negative electrode.

Transparent Y2O3-MgO nanocomposite ceramic has been processed for mid-IR window applications. The powder was synthesized by a sol-gel route. The final temperature of this process has an impact on the crystallite size and crystallization ratio. A homogeneous powder with around 10 nm crystallite size was made with a final tem-perature of 600 degrees C. The powder was then sintered by the SPS technique performing a two-step sintering process at 1200 degrees C/50 MPa instead of a conventional bearing. A fully dense ceramic (>99%) with an average grain diameter of 150 nm (compared to 350 nm with one-stage sintering) was obtained. After HIP at 400 MPa and annealing in air for 100 h post-treatments, the IR transmittance in the 3-5 mu m wavelength range exceeds 80% for a thickness of 1 mm. Transparency loss at 5 mu m is less than 10% at 1000 degrees C, which is more suitable for the IR's band II than materials such as sapphire, spinel or AlON.

Lamellar lithiated nitridonickelates have been investigated from both experimental and theoretical points of view in a wide range of compositions. In this study, we show that the nickel ion in lamellar lithiated nitridonickelates adopts an intermediate valence close to +1.5. This solid solution can therefore be written Li3-1.5xNixN with 0 ≤ x ≤ 0.68. Attempts to introduce more nickel into these phases systematically lead to the presence of the endmember of the solid solution, Li1.97Ni0.68N, with metallic nickel as an impurity. The LiNiN phase has never been observed, and first-principles calculations suggested that all the structural configurations tested were mechanically unstable.

Y0.95Ni2 intermetallic is a promising candidate for hydrogen storage applications, but currently suffers from hydrogen-induced amorphization (HIA) mainly caused by its low stability. The structure stability of AB2 Laves phase is mainly controlled by the geometric factor rA/rB. The present work is focused on the ternary Mn-Ni-Y system, as Mn addition helps achieving a close-to-ideal rA/rB (<= 1.37) to avoid HIA or HID. Through a combination of X-ray diffraction, neutron diffraction, electron probe micro-analysis and first-principles calculations, new insight on the physicochemical properties and phase equilibrium of this ternary system was gained. Mn substitution is found to suppress the formation of a super-structure with ordered vacancies, in favor of a C15 Laves structure with a disordered distribution of Y vacancies. At low concentration Mn is accommodated only on the Ni sites, compensated by vacancies on the Y site (without long-range order). At high concentration, Mn is accommodated on both Ni and Y sites, with reduced Y vacancy concentration. The partitioning of Mn across the two sites allows to form a single-phase ternary intermetallic across a wide compositional range and suggests increased stability of the phase. Crown Copyright (c) 2023 Published by Elsevier B.V. All rights reserved.

Y0.95Ni2 intermetallic is a promising candidate for hydrogen storage applications, but currently suffers from hydrogen-induced amorphization (HIA) mainly caused by its low stability. The structure stability of AB2 Laves phase is mainly controlled by the geometric factor rA/rB. The present work is focused on the ternary Mn-Ni-Y system, as Mn addition helps achieving a close-to-ideal rA/rB (≤1.37) to avoid HIA or HID. Through a combination of X-ray diffraction, neutron diffraction, electron probe micro-analysis and first-principles calculations, new insight on the physicochemical properties and phase equilibrium of this ternary system was gained. Mn substitution is found to suppress the formation of a super-structure with ordered vacancies, in favor of a C15 Laves structure with a disordered distribution of Y vacancies. At low concentration Mn is accommodated only on the Ni sites, compensated by vacancies on the Y site (without long-range order). At high concentration, Mn is accommodated on both Ni and Y sites, with reduced Y vacancy concentration. The partitioning of Mn across the two sites allows to form a single-phase ternary intermetallic across a wide compositional range and suggests increased stability of the phase.

The kinetics of the electrochemical lithium intercalation in the nitridonickelate LixNi0.67N (1.67 <= x <= 2.17) is investigated by electrochemical impedance spectroscopy during a full reduction-oxidation cycle in a twoelectrode cell. The layered structure of this anode material delivers a reversible and stable specific capacity of 200 mAh g(- 1) over 100 cycles at C/10 near 0.5 V vs Li+/Li. The equivalent electric circuit simulation allows a full assignment of the impedance spectra, with different contributions including the SEI layers on each electrode, charge transfer and Li diffusion. The calculated lithium diffusion coefficient value of approximately 5 x 10(-9) cm(-2) s(-1) almost does not vary with the lithium content in LixNi0.67N (1.67 <= x <= 2.17). Conversely, the charge transfer resistance (R-ct) is found to strongly depend on the depth of reduction to be maximum for the fully reduced electrode, with a totally reversible behavior during oxidation. The overall impedance of the cell remains stable upon long cycling, which indicates a good chemical stability of the SEI on LixNi0.67N as well as remarkable structural and chemical stability of the nitridonickelate upon cycles. The present kinetic findings shed light on the remarkable ''zero-strain'' behavior of this negative electrode material presenting numerous Li vacancies.

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.

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.

On the recent research front for the next generation secondary batteries beyond Li, potassium insertion into graphite in non-aqueous cells has brought new insights into the electrochemical K+ intercalation behavior and introduced advantageous benefits from potassium. Since potassium resources are much abundant and the standard potential of K+/K is 0.13 V below that of Li+/Li, potassium-ion batteries can be regarded as an appealing alternative to LIBs to realize high voltage systems with low cost. The crucial issue is the development of cathode materials able to accommodate the large K-ion without displaying detrimental structural changes toward cycle life and rate capability performance. The 4.7 V LiMn1.5Ni0.5O4 spinel is already a promising cathode for the next generation of high voltage LIBs, and its host structure, λ-Mn0.75Ni0.25O2, could be of great interest for K-ion batteries. Here, we investigate for the first time the potassium insertion properties into electrochemically prepared λ-MnO2 (λ-MO) and λ-Mn0.75Ni0.25O2 (λ-MNO) spinels. Lithium ions in LiMn2O4 and LiMn1.5Ni0.5O4 samples are electrochemically extracted in lithium containing electrolyte solution, forming λ-Mn1- xNixO2 (x = 0, 0.25) by first oxidation process. Potassium ions are then inserted into the lithium extracted spinel phases. From structural analysis by X-ray diffraction and Raman spectroscopy, it is found that the original λ-Mn0.75Ni0.25O2 spinel phase converts into a layered phase, K~0.5Mn0.75Ni0.25O2. Then, K~0.5Mn0.75Ni0.25O2 can deliver a high reversible capacity of 90 mAh g-1 at C/20 in the 2 V- 4.6 V vs K+/K voltage range with 78% retention for 60 cycles at C/20 (Fig. 1). Promising rate performance are also evidenced with an initial capacity of 60 mAh g-1 at C/5 (Fig. 1), and 65% retention after 300 cycles at C/5. The origin of the attractive electrochemical performances of λ-MNO is investigated by XRD , Raman and EDS experiments after discharge and charge cycles. These results open the possibility of using inexpensive and high-capacity Mn-based active materials for potassium-ion batteries. Figure 1. Electrochemical properties of λ-Mn0.75Ni0.25O2 in a potassium cell. 1M KF6 /EC:PC 1:1 electrolyte, 2% vol. FEC. Voltage window 4.5 V- 2 V. Figure 1

The emerging interest in K-ion batteries (KIBs) increases the importance of cathodes with high working voltage in this system. The LiMn1.5Ni0.5O4 spinel is a promising alternative for the next generation of high voltage Li-ion positive electrodes and its delithiated structure could be of interest for KIBs. In this work, Li ions are extracted from LiMn1.5Ni0.5O4 by a first electrochemical oxidation. The electroformed lambda-Mn0.75Ni0.25O2 spinel phase is shown to convert into layered K0.5Mn0.75Ni0.25O2 (KMNO) at 20 degrees C along the first discharge in K cell. Then, 0.3 K+/KMNO (90 mAh g(-1)) are reversibly exchanged during the subsequent cycle. Superior electrochemical performance are reported for KMNO as compared to K0.5MnO2 (KMO): a higher working voltage vs. K+/K (3.10 V vs. 2.79 V), enhanced rate capability and better cycling stability (70 mAh g(-1) after 60 cycles at C/20 for KMNO vs. 40 mAh g(-1) for KMO). The contribution of the Ni redox system is revealed as a reason for these improved performances.

Low-cost, easily processable, and environmentally friendly rechargeable aqueous zinc batteries have great potential for large-scale energy storage, which justifies their receiving extensive attention in recent years. An original concept based on the use of a binary Li+/Zn2+ aqueous electrolyte is described herein for the case of the Zn/V2O5 system. In this hybrid, the positive side involves mainly the Li+ insertion/deinsertion reaction of V2O5, whereas the negative electrode operates according to zinc dissolution-deposition cycles. The Zn//3 mol L-1 Li2SO4-4 mol L-1 ZnSO4///V2O5 cell worked in the narrow voltage range of 1.6-0.8 V with capacities of approximately 136-125 mA h g(-1) at rates of C/20-C/5, respectively. At 1 C, the capacity of 80 mA h g(-1) was outstandingly stable for more than 300 cycles with a capacity retention of 100 %. A detailed structural study by XRD and Raman spectroscopy allowed the peculiar response of the V2O5 layered host lattice on discharge-charge and cycling to be unraveled. Strong similarities with the well-known structural changes reported in nonaqueous lithiated electrolytes were highlighted, although the emergence of the usual distorted delta-LiV2O5 phase was not detected on discharge to 0.8 V. The pristine host structure was restored and maintained during cycling with mitigated structural changes leading to high capacity retention. The present electrochemical and structural findings reveal a reaction mechanism mainly based on Li+ intercalation, but co-intercalation of a few Zn2+ ions between the oxide layers cannot be completely dismissed. The presence of zinc cations between the oxide layers is thought to relieve the structural stress induced in V2O5 under operation, and this resulted in a limited volume expansion of 4 %. This fundamental investigation of a reaction mechanism operating in an environmentally friendly aqueous medium has not been reported before.