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Disordered rock‐salt (DRS) type active materials are highly significant because of their large reversible capacities, which are due to their unique Li+ diffusion pathway and the redox capabilities of cationic transition metals (TMs) and anionic O ions. Loosely crystalline DRS materials have weak covalent bonds between TMs and O, increasing the O redox contribution and thereby enhancing their capacities. In this study, Mn‐based positive electrode materials with DRS structures are activated and stabilized by mechanochemical doping of nonmetallic elements P and B into interstitial sites. Synthesized Li0.90Mn0.84P0.04O2 (LMPO5) exhibits an initial discharge capacity of 346 mAh g−1 (1050 Wh kg−1) during charging/discharging. Li0.91Mn0.83B0.10O2 (LMBO5) has a moderately expanded lattice size, which facilitates high‐capacity retention during cycling (≈284 mAh g−1 at the 30th cycle). The structural properties of the synthesized active materials are extensively characterized. By introducing nonmetallic elements into the interstitial sites of Mn‐based materials, inexpensive, high‐capacity, and long‐cycling/calendar‐life Co/Ni‐free monometallic positive electrode materials may be further developed. [ABSTRACT FROM AUTHOR]

Lithium-rich layered oxides (LRLO) are a wide class of innovative active materials used in positive electrodes in lithium-ion (LIB) and lithium–metal secondary batteries (LMB). LRLOs are over-stoichiometric layered oxides rich in lithium and manganese with a general formula Li1+xTM1−xO2, where TM is a blend of transition metals comprising Mn (main constituent), Ni, Co, Fe and others. Due to their very variable composition and extended defectivity, their structural identity is still debated among researchers, being likely an unresolved hybrid between a monoclinic (mC24) and a hexagonal lattice (hR12). Once casted in composite positive electrode films and assembled in LIBs or LMBs, LRLOs can deliver reversible specific capacities above 220–240 mAhg−1, and thus they exceed any other available intercalation cathode material for LIBs, with mean working potential above 3.3–3.4 V vs Li for hundreds of cycles in liquid aprotic commercial electrodes. In this review, we critically outline the recent advancements in the fundamental understanding of the physical–chemical properties of LRLO as well as the most exciting innovations in their battery performance. We focus in particular on the elusive structural identity of these phases, on the complexity of the reaction mechanism in batteries, as well as on practical strategies to minimize or remove cobalt from the lattice while preserving its outstanding performance upon cycling. [ABSTRACT FROM AUTHOR]

Organic electrode materials are capable candidates for next‐generation greener energy storage solutions. One advantage is that their electrochemical performance can be tuned by structural modification. We herein investigate anisyl‐substituted poly(vinyl‐) and poly(styrylphenothiazines) as positive electrode materials for dual‐ion batteries. π‐Interactions – characteristic to phenothiazine redox polymers – are facilitated in the poly(styrene) derivatives PSAPT and PSAPT‐X‐DVB due to the longer spacing between phenothiazine units and polymer backbone and lead to high cycling stabilities, but reduce their specific capacities. In the poly(vinylenes), the linear PVAPT shows high cycling stability but a dissolution/redeposition mechanism, diminishing its capacity, while the cross‐linked X‐PVAPT demonstrates high cycling stabilities at specific capacities up to 81 mAh g−1 paired with an excellent rate performance, where 10,000 cycles at 100 C rate proceed with 86 % capacity retention. [ABSTRACT FROM AUTHOR]

In this manuscript, we report an extensive study of the physico-chemical properties of different samples of O3-NaMnO2, synthesized by sol–gel and solid state methods. In order to successfully synthesize the materials by sol–gel methods a rigorous control of the synthesis condition has been optimized. The electrochemical performances of the materials as positive electrodes in aprotic sodium-ion batteries have been demonstrated. The effects of different synthesis methods on both structural and electrochemical features of O3-NaMnO 2 have been studied to shed light on the interplay between structure and performance. Noticeably, we obtained a material capable of attaining a reversible capacity exceeding 180 mAhg − 1 at 10 mAg − 1 with a capacity retention >70% after 20 cycles. The capacity fading mechanism and the structural evolution of O3-NaMnO 2 upon cycling have been extensively studied by performing post-mortem analysis using XRD and Raman spectroscopy. Apparently, the loss of reversible capacity upon cycling originates from irreversible structural degradations. [ABSTRACT FROM AUTHOR]

The addition of tungsten has been reported to greatly improve the capacity retention of Ni‐rich layered oxide cathode materials in lithium‐ion batteries. In this work, Ni(OH)2 precursors, coated with WO3 and also W‐containing precursors prepared by co‐precipitation followed by heat treatment with LiOH·H2O, are studied. Structural analysi s and electron microscopy show that W is incorporated as amorphous LixWyOz phases concentrated in all the grain boundaries between the primary particles of LiNiO2 (LNO) and on the surface of the secondary particles. Tungsten does not substitute for Ni or Li in the LNO lattice no matter how W is added at the precursor synthesis stage. Scanning electron microscopy (SEM) images show that adding W greatly suppresses primary particle growth during synthesis. In agreement with previous literature reports, cycling test results show that 1% W added to LNO can greatly improve charge–discharge capacity retention while also delivering a high specific capacity. The LixWyOz amorphous phases act as coating layer on both the primary and secondary particles, restrict primary particle growth during synthesis and increase the resistance of the secondary particles to microcracking. [ABSTRACT FROM AUTHOR]

Lithium-rich layered oxides (LRLO) are a wide class of innovative active materials used in positive electrodes in lithium-ion (LIB) and lithium–metal secondary batteries (LMB). LRLOs are over-stoichiometric layered oxides rich in lithium and manganese with a general formula Li1+xTM1−xO2, where TM is a blend of transition metals comprising Mn (main constituent), Ni, Co, Fe and others. Due to their very variable composition and extended defectivity, their structural identity is still debated among researchers, being likely an unresolved hybrid between a monoclinic (mC24) and a hexagonal lattice (hR12). Once casted in composite positive electrode films and assembled in LIBs or LMBs, LRLOs can deliver reversible specific capacities above 220–240 mAhg−1, and thus they exceed any other available intercalation cathode material for LIBs, with mean working potential above 3.3–3.4 V vs Li for hundreds of cycles in liquid aprotic commercial electrodes. In this review, we critically outline the recent advancements in the fundamental understanding of the physical–chemical properties of LRLO as well as the most exciting innovations in their battery performance. We focus in particular on the elusive structural identity of these phases, on the complexity of the reaction mechanism in batteries, as well as on practical strategies to minimize or remove cobalt from the lattice while preserving its outstanding performance upon cycling.

In this manuscript, we report an extensive study of the physico-chemical properties of different samples of O3-NaMnO2, synthesized by sol–gel and solid state methods. In order to successfully synthesize the materials by sol–gel methods a rigorous control of the synthesis condition has been optimized. The electrochemical performances of the materials as positive electrodes in aprotic sodium-ion batteries have been demonstrated. The effects of different synthesis methods on both structural and electrochemical features of O3-NaMnO2 have been studied to shed light on the interplay between structure and performance. Noticeably, we obtained a material capable of attaining a reversible capacity exceeding 180 mAhg−1 at 10 mAg−1 with a capacity retention >70% after 20 cycles. The capacity fading mechanism and the structural evolution of O3-NaMnO2 upon cycling have been extensively studied by performing post-mortem analysis using XRD and Raman spectroscopy. Apparently, the loss of reversible capacity upon cycling originates from irreversible structural degradations.

Li‐rich transition‐metal oxides with a disordered rocksalt structure have drawn much attention as promising candidates for a positive electrode material of a lithium‐ion battery. Among the oxides, this study focuses on Li1.3Nb0.3Fe0.4O2 and Li1.3Nb0.43Ni0.27O2, and investigates local distortions around the cations and local cation ordering in the materials by means of a reverse Monte Carlo modeling using neutron and synchrotron X‐ray total scattering data. It is found from the simulated atomic configurations that a local distortion around Nb is larger than those around the other cations in both the materials. The large distortion is supposed to be induced by a smaller ionic radius of Nb than the others and/or a mismatch of electronic state of Nb in the disordered rocksalt structure. Furthermore, a coordination‐number analysis on the materials demonstrates that Li tends to be surrounded by Nb significantly in the disordered rocksalt structure. From these results, it can be considered that Li diffusion is disturbed by a cation with a higher valence in the disordered rocksalt structure. [ABSTRACT FROM AUTHOR]

Cobalt‐ and nickel‐free cathode materials are desirable for developing low‐cost sodium‐ion batteries (SIBs). Compared to the single P‐type and O‐type structures, biphasic P/O structures become a topic of interest thanks to improved performance. However, the added complexity complicates the understanding of the storage mechanism and the phase behavior is still unclear, especially over consecutive cycling. Here, the properties of biphasic P2(34%)/O3(60%) Na0.8Li0.2Fe0.2Mn0.6O2 and its behavior at different states of charge/discharge are reported on. The material is composed of single phase O3 and P2/O3 biphasic particles. Sodium occupies the alkali layers, whereas lithium predominantly (95%) is located in the transition metal layer. An initial reversible capacity of 174 mAh g‐1 is delivered with a retention of 82% dominated by Fe3+/Fe4+ along with contributions from oxygen and partial Mn3+/4+ redox. Cycling leads to complex phase transitions and ion migration. The biphasic nature is nevertheless preserved, with lithium acting as the structure stabilizer. [ABSTRACT FROM AUTHOR]

Transition-metal (TM) layered oxides have been attracting enormous interests in recent decades because of their excellent functional properties as positive electrode materials in lithium-ion batteries. In particular LiCoO2 (LCO), LiNiO2 (LNO) and LiMnO2 (LMO) are the structural prototypes of a large family of complex compounds with similar layered structures incorporating mixtures of transition metals. Here, we present a comparative study on the phase stability of LCO, LMO and LNO by means of first-principles calculations, considering three different lattices for all oxides, i.e., rhombohedral (hR12), monoclinic (mC8) and orthorhombic (oP8). We provide a detailed analysis—at the same level of theory—on geometry, electronic and magnetic structures for all the three systems in their competitive structural arrangements. In particular, we report the thermodynamics of formation for all ground state and metastable phases of the three compounds for the first time. The final Gibbs Energy of Formation values at 298 K from elements are: LCO(hR12) −672 ± 8 kJ mol−1; LCO(mC8) −655 ± 8 kJ mol−1; LCO(oP8) −607 ± 8 kJ mol−1; LNO(hR12) −548 ± 8 kJ mol−1; LNO(mC8) −557 ± 8 kJ mol−1; LNO(oP8) −548 ± 8 kJ mol−1; LMO(hR12) −765 ± 10 kJ mol−1; LMO(mC8) −779 ± 10 kJ mol−1; LMO(oP8) −780 ± 10 kJ mol−1. These values are of fundamental importance for the implementation of reliable multi-phase thermodynamic modelling of complex multi-TM layered oxide systems and for the understanding of thermodynamically driven structural phase degradations in real applications such as lithium-ion batteries.

Derivatives of tris-fused TTF extended with two ethanediylidenes (5), tris- and pentakis-fused TTFs extended with two thiophene-2,5-diylidenes (6–9) were successfully synthesized. Cyclic voltammograms of the tetrakis(n-hexylthio) derivative of 5 and 7 (5d, 7d) consisted of two pairs of two-electron redox waves and two pairs of one-electron redox waves. On the other hand, four pairs of two-electron redox waves and two pairs of one-electron redox waves were observed for the tetrakis(n-hexylthio) derivative of 9 (9d). Coin-type cells using the bis(ethylenedithio) derivatives of 5 (5b), 6 (6b) and the tetrakis(methylthio) derivatives of 5 (5c) and 8 (8c) as positive electrode materials showed initial discharge capacities of 157–190 mAh g−1 and initial energy densities of 535–680 mAh g−1. The discharge capacities after 40 cycles were 64–86% of the initial discharge capacities.

Lithium ion batteries (LIBs) are one of the most promising secondary batteries due to their advantages including long cycle life, high energy density, limited self-discharge, high operating voltage and environmental friendliness. The development of electrode materials is crucial for the further application of LIBs. There are many effective ways to enhance the performance of positive electrode materials of LIBs such as surface coating, ion doping, preparation of composite materials and nanosized materials and so forth. Among them, surface coating is considered to be a promising way to improve the electrochemical performance of LIBs. Surface coating can normally form a physical barrier or a doped surface layer to play favorable roles for the electrode materials, such as hindering side reactions between positive electrode materials and the electrolyte. In this paper, different kinds of surface coating layers will be discussed according to previous research, including carbon materials, metal oxides, metal fluorides, metal phosphates, nonmetal oxides, electrode materials coating layer, hybrid coating layer, polymer and so forth. In addition, the mechanism of these coating materials will be summarized, and the future development will be discussed in this paper. In the current study, different coating layers of the positive electrode for lithium ion batteries are summarized, including carbon materials, metal oxides, metal fluorides, metal phosphates, nonmetal oxides, electrode materials coating layer, hybrid coating layer, polymer and so forth. The mechanism of these coating layers is also discussed. [ABSTRACT FROM AUTHOR]

Abstract: Sodium 3d transition metal oxides for Na‐ion batteries have attracted attention of battery researchers because of their new chemistries and abundant material resources in the earth. Some companies have also developed Na‐ion battery prototypes mainly consisting of a layered oxide as a positive electrode material and hard carbon as the negative one for practical use. In this article, progress of Na‐containing layered transition‐metal oxides is reviewed in terms of fundamental chemistry and technology aspects for future batteries as a post Li‐ion battery. To realize practical positive electrode materials is still challenging and the practical issues are discussed. In this context the authors propose strategies for designing layered transition‐metal oxide materials toward realization of practical Na‐ion batteries. [ABSTRACT FROM AUTHOR]

The implementation of high potential materials as positive electrodes in high energy Li-ion batteries requires to develop scalable and smart synthetic routes. In the case of the LiNi 0.5 Mn 1.5 O 4 (LNMO) spinel material, a successful preparation strategy must drive the phase formation in order to obtain structural, morphological and surface properties capable to boost performances in lithium cells and minimize the electrolyte degradation. Here we discuss a novel simple and easily scalable mechanochemical synthetic route, followed by a high temperature annealing in air, to prepare LMNO materials starting from oxides. A synergic doping with chromium and iron has been incorporated, resulting in the spontaneous segregation of a CrO x -rich surface layer. The effect of the annealing temperature on the physico-chemical properties of the LMNO material has been investigated as well as the effect on the performances in Li-cells. [ABSTRACT FROM AUTHOR]

Nickel-rich layered oxides are adopted as electrode materials for EV's. They suffer from a capacity loss when the cells are charged above 4.15 V versus Li/Li + . Doping and coating can lead to significant improvement in cycling. However, the mechanisms involved at high voltage are not clear. This work is focused on LiNiO 2 to overcome the effect of M cations. Galvanostatic intermittent titration technique (GITT) and in situ X-ray diffraction (XRD) experiments are performed at very low rates in various voltage ranges (3.8-4.3 V,). On the "4.2-4.3 V" plateau the R2 phase is transformed simultaneously in R3, R3 with H4 stacking faults and H4. As the charge proceeds above 4.17 V cell polarization increases, hindering Li deintercalation. In discharge, such polarization decreases immediately. Upon cycling, the polarization increases at each charge above 4.17 V. In discharge, the capacity and dQ/dV features below 4.1 V remain constant and unaffected, suggesting that the bulk of the material do not undergo significant structural defect. This study shows that the change in polarization results from the electrochemical behavior of the grain surface having very low conductivity above 4.17 V and high conductivity below this threshold. This new approach can explain the behavior observed with dopants like tungsten., (© 2023 The Authors. Small published by Wiley-VCH GmbH.)

To realize a reversible solid-state MnIII/IV redox couple in layered oxides, co-operative Jahn-Teller distortion (CJTD) of six-coordinate MnIII (t2g3-eg1) is a key factor in terms of structural and physical properties. We develop a single-phase synthesis route for two polymorphs, namely distorted and undistorted P2-type Na2/3MnO2 having different Mn stoichiometry, and investigate how the structural and stoichiometric difference influences electrochemical reaction. The distorted Na2/3MnO2 delivers 216 mAh g−1 as a 3 V class positive electrode, reaching 590 Wh (kg oxide)−1 with excellent cycle stability in a non-aqueous Na cell and demonstrates better electrochemical behavior compared to undistorted Na2/3MnO2. Furthermore, reversible phase transitions correlated with CJTD are found upon (de)sodiation for distorted Na2/3MnO2, providing a new insight into utilization of the MnIII/IV redox couple for positive electrodes of Na-ion batteries. [ABSTRACT FROM AUTHOR]

To realize a reversible solid-state MnIII/IV redox couple in layered oxides, co-operative Jahn-Teller distortion (CJTD) of six-coordinate MnIII (t2g3-eg1) is a key factor in terms of structural and physical properties. We develop a single-phase synthesis route for two polymorphs, namely distorted and undistorted P2-type Na2/3MnO2 having different Mn stoichiometry, and investigate how the structural and stoichiometric difference influences electrochemical reaction. The distorted Na2/3MnO2 delivers 216 mAh g−1 as a 3 V class positive electrode, reaching 590 Wh (kg oxide)−1 with excellent cycle stability in a non-aqueous Na cell and demonstrates better electrochemical behavior compared to undistorted Na2/3MnO2. Furthermore, reversible phase transitions correlated with CJTD are found upon (de)sodiation for distorted Na2/3MnO2, providing a new insight into utilization of the MnIII/IV redox couple for positive electrodes of Na-ion batteries. [ABSTRACT FROM AUTHOR]

LiNi x Mn y Co 1 − x − y O 2 compounds (NMC) are layered oxides widely used in commercial lithium-ion batteries at the positive electrode. Nevertheless surface reactivity of this material is still not well known. As a first step, based on first principle calculations, this study deals with the electronic properties and the surface reactivity of LiMO 2 (M = Co, Ni, Mn) compounds, considering the behavior of each transition metal separately in the same R 3 ̅ m α -NaFeO 2 -type structure, the one of LiCoO 2 and NMC. For each compound, after a brief description of the bare slab electronic properties, we explored the acido-basic and redox properties of the (110) and (104) surfaces by considering the adsorption of a gaseous probe. The chemisorption of SO 2 produces both sulfite or sulfate species associated respectively to an acido-basic or a reduction process. These processes are localized on the transition metals of the first two layers of the surface. Although sulfate species are globally favored, a different behavior is obtained depending on both the surface and the transition metal considered. We conclude with a simple scheme which describes the reduction processes on the both surfaces in terms of formal oxidation degrees of transition metals. [ABSTRACT FROM AUTHOR]

Cation mixing in positive electrode materials for rechargeable lithium ion batteries, LiNixMn2-xO4 (x = 0, 0.2, 0.5) and Li0.21Ni0.7Mn1.64O4-δ (denoted as x = 0.7), is analyzed by high-angular-resolution electron-channeling X-ray/electron spectroscopy (HARECXS/ HARECES) techniques, using energy-dispersive X-ray spectroscopy and electron energyloss spectroscopy. Mixing between the tetrahedral lithium sites and the octahedral transition metal sites is quantified, and the site-dependent valence states of the transition metals are examined. In the non-doped (x = 0) sample, Mn was found to occupy only octahedral sites as either Mn3+ or Mn4+. For x = 0.2-0.7, some of the nickel ions (6-13% depending on x) occupy tetrahedral anti-sites. All the nickel ions are in the divalent state, regardless of the occupation site. For x = 0.2 and 0.7, manganese ions occupy both octahedral and tetrahedral sites; those in the octahedral sites are tetravalent, while the tetrahedral sites contain a mixture of divalent and trivalent ions. For x = 0.5, manganese occupies only the octahedral sites, with all ions determined to be in the tetravalent state (within experimental accuracy). All the samples substantially satisfied the local charge neutrality conditions. This study demonstrates the feasibility of using HARECXS/ HARECES for quantitative analysis of the atomic configuration and valence states in lithium manganese oxide spinel materials. [ABSTRACT FROM AUTHOR]

Na 2 MnF 5 and NaMnF 3 were prepared in aqueous media using Mn 2 O 3 and NaMnO 4 ·H 2 O as Mn precursors and characterized by XRPD, ATR-IR and ICP-OES/ICP-MS. Additionally, a new metastable hydrated oxyfluoride was prepared, with a diffraction pattern (neutron and SXRPD data) consistent with an orthorhombic cell with a = 4.07559 Å, b = 9.04090 Å and c = 6.77290 Å and Cccm space group which yielded NaMnF 4 upon dehydration. The feasibility of Na + deintercalation was experimentally tested in electrochemical cells against sodium metal counter electrodes under different conditions, and also investigated by first principles methods. Experimental results were confronted to blank experiments performed with electrodes containing only carbon black and allowed to conclude that the redox processes observed were not related to active materials but to electrolyte/carbon black reactivity. DFT results point at the electrochemical activity of such compounds taking place at high potential values, in some cases well outside the electrolyte stability window. In the case of NaMnF 3 , for which he calculated density of states predicts a bang gap of 2.7 eV, its insulating character induces significant cell polarization thus electrochemical activity cannot not practically reached with the available electrolytes. [ABSTRACT FROM AUTHOR]

Sodium layered oxides with mixed transition metals have received significant attention as positive electrode candidates for sodium-ion batteries because of their high reversible capacity. The phase transformations of layered compounds during electrochemical reactions are a pivotal feature for understanding the relationship between layered structures and electrochemical properties. A combination of in situ diffraction and ex situ X-ray absorption spectroscopy reveals the phase transition mechanism for the ternary transition metal system (Fe-Mn-Co) with P2 stacking. In situ synchrotron X-ray diffraction using a capillary-based microbattery cell shows a structural change from P2 to O2 in P2-Na0.7Fe0.4Mn0.4Co0.2O2 at the voltage plateau above 4.1 V on desodiation. The P2 structure is restored upon subsequent sodiation. The lattice parameter c in the O2 structure decreases significantly, resulting in a volumetric contraction of the lattice toward a fully charged state. Observations on the redox behavior of each transition metal in P2-Na0.7Fe0.4Mn0.4Co0.2O2 using X-ray absorption spectroscopy indicate that all transition metals are involved in the reduction/oxidation process. [ABSTRACT FROM AUTHOR]

Abstract: Sulfur–carbon composites were investigated as positive electrode materials for all-solid-state lithium ion batteries with an inorganic solid electrolyte (amorphous Li3PS4). The elemental sulfur was mixed with Vapor-Grown Carbon Fiber (VGCF) and with the solid electrolyte (amorphous Li3PS4) by using high-energy ball-milling process. The obtained sulfur–VGVF–solid electrolyte composite was used as positive electrode materials of the all-solid-state battery. The composite showed good electrochemical properties as positive electrode materials. The capacity that was calculated on the base of the weight of sulfur was about 1300mAhg−1 at room temperature, when the all-solid-state battery was discharged and charged in the voltage range of 0.9 to 2.6V at a constant current density of 0.1mAcm−2. The battery kept the capacity more than 1200mAhg−1 even after 50 discharge–charge cycles. [Copyright &y& Elsevier]

LiMnO and vanadium-substituted LiVMnO ( x = 0.05, 0.10 0.15 and 0.20) cathode materials were synthesized by sol-gel method using aqueous solutions of metal nitrates and tartaric acid as chelating agent at 600 °C for 10 h. The structure and electrochemical properties of the synthesized materials were characterized by using X-ray diffraction, SEM, TEM and charge-discharge studies. X-ray powder diffraction analysis was changed in lattice parameters with increasing vanadium content suggesting the occupation of the substituent within LiMnO interlayer spacing. TEM and SEM analyses show that LiVMnO has a smaller particle size and more regular morphological structure with narrow size distribution than LiMnO. It is concluded that the structural stability and cycle life improvement were due to many factors like better crystallinity, smaller particle size and uniform distribution compared to the LiMnO cathode material. The LiVMnO cathode material has improved the structural stability and excellent electrochemical performances of the rechargeable lithium ion batteries. [ABSTRACT FROM AUTHOR]

LiMn2O4 spinel cathode materials were coated with 1.0, 2.0 and 3.0wt% of LaPO4 by the polymeric process, followed by calcinations at 800°C for 6h in air. The structure and electrochemical properties of the surface modified LiMn2O4 materials were characterized by XRD, SEM, XPS, cyclic voltammetry and charge–discharge techniques. XRD patterns of LaPO4 coated LiMn2O4 revealed that the coating did not affect the crystal structure and space group Fd3m of the powder materials, compared to the uncoated LiMn2O4. XPS data illustrate that the LaPO4 was completely coated over the surface of the LiMn2O4 core materials. 2wt% of LaPO4 coated LiMn2O4 cathode material exhibits specific capacity of 103mAh/g (versus lithium metal) and excellent capacity retention (82% of its initial capacity) between 4.5 and 3V after 100 cycles at elevated temperature (50°C). LiMn2O4 coated with 0.0–3.0wt% of LaPO4 has slightly decreased the initial capacity, but the cycling stability increased remarkably over 3–4.5V. This result indicates that the surface treatment should be an effective way to improve the overall properties of the cathode materials for lithium ion batteries. Among them, 2wt% of LaPO4 coated spinel LiMn2O4 cathode material has improved the structural stability, high reversible capacity at elevated temperature and excellent electrochemical performances of the rechargeable lithium batteries. [ABSTRACT FROM AUTHOR]

We have successfully prepared Li0.44+x Mn1−y Ti y O2 having the Na0.44MnO2-type framework structure by ion-exchange technique in molten LiNO3 and LiNO3–LiOH salts at 270 °C from the precursor Na0.44Mn1−y Ti y O2 synthesized at 800 °C using homogeneous and fine Mn–Ti hydroxides as starting materials. The needle-shaped particle length can be successfully reduced. The chemical composition and the crystal structure of Li0.44+x Mn1−y Ti y O2 were confirmed by using ICP–AES and XRD Rietveld analyses. The electrochemical measurements revealed that both the charge and discharge properties of the obtained Li0.44+x Mn1−y Ti y O2 samples were drastically improved. Especially, the obtained Li0.71Mn0.90Ti0.10O2 exhibited initial charge and discharge capacities of 176 and 212 mAh g−1, respectively, with an average discharge voltage of 3.56 V vs. Li/Li+. The resultant initial discharge energy density was achieved to be 755 Wh kg− 1. A further chemical lithiation treatment was performed using LiI for the Li0.63MnO2 and Li0.71Mn0.90Ti0.10O2 samples. The electrochemical measurements between 4.8 and 2.5 V for the lithiated Li0.83MnO2 and Li0.90Mn0.90Ti0.10O2 samples showed the improvement of the initial charge capacities. The rate capability test revealed Li0.90Mn0.90Ti0.10O2 retains 81% of its discharge capacity in going from 1C to 5C rate. The excellent high rate capability and good cycling performance of Li0.90Mn0.90Ti0.10O2 is particularly attractive for electric vehicle applications. [ABSTRACT FROM AUTHOR]

Abstract: Spinel LiMn2O4 is a very promising material for positive electrodes in a wide range of Li-ion battery applications due to its lower cost and more environmental friendliness than any other electrode materials. Although the bulk properties of LiMn2O4 have been studied intensively, there have been few reports about the structure and properties of LiMn2O4 surfaces in spite of the importance of solid/electrolyte interfaces. This is caused by the difficulty in preparing LiMn2O4 samples with accessible flat surfaces suitable for atomistic observations. To address this, we have successfully prepared a single crystalline LiMn2O4 film with an atomically flat surface by solid-state reaction from a MnO wafer with LiOH.H2O powder. X-ray diffraction (XRD) reveals the single crystalline growth of LiMn2O4 films depending on the orientation of a MnO wafer. Atomic force microscopy observations revealed that a LiMn2O4 (111) film has an atomically flat surface with steps of a {111} interlayer height. Electron energy-loss spectroscopy (EELS) study of the (111) film revealed that the sample consists of Li, Mn3+ and Mn4+ with a composition similar to LiMn2O4. The (111) film sample is also investigated by cyclic voltammetry and galvanostatic experiments, revealing that a crushed powder sample from the film has electrochemical activity as usual positive electrode material. [Copyright &y& Elsevier]

It is desirable for secondary batteries to have high capacities and long lifetimes. This paper reports the use of Na 2 FeS 2 with a specific structure consisting of edge-shared and chained FeS 4 as the host structure and as a high-capacity active electrode material. An all-solid-state sodium cell that uses Na 2 FeS 2 exhibits a high capacity of 320 mAh g -1 , which is close to the theoretical two-electron reaction capacity of 323 mAh g -1 , and operates reversibly for 300 cycles. The excellent electrochemical properties of all-solid-state sodium cells are derived from the anion-cation redox and rigid host structure during charging/discharging. In addition to the initial one-electron reaction of Na x FeS 2 (1 ≤ x ≤ 2) activated Fe 2+ /Fe 3+ redox as the main redox center, the reversible sulfur redox further contributes to the high capacity. Although the additional sulfur redox affects the irreversible crystallographic changes, stable and reversible redox reactions are observed without capacity fading, owing to the local maintenance of the chained FeS 4 in the host structure. Sodium iron sulfide Na 2 FeS 2 , which combines low-cost elements, is one of the candidates that can meet the high requirements of practical applications., (© 2022 The Authors. Small published by Wiley-VCH GmbH.)

Intensive research is underway to further enhance the performance of lithium-ion batteries (LIBs). To increase the capacity of positive electrode materials, Li-rich layered oxides (LLO) are attracting attention but have not yet been put to practical use. The structural mechanisms through which LLO materials exhibit higher capacity than conventional materials remain unclear because their disordered phases make it difficult to obtain structural information by conventional analysis. The X-ray total scattering analysis reveals a disordered structure consisting of metal ions in octahedral and tetrahedral sites of Li layers as a result of cation mixing after the extraction of Li ions. Metal ions in octahedral sites act as rigid pillars. The metal ions move to the tetrahedral site of the Li layer, which functions as a Li-layer pillar during Li extraction, and returns to the metal site during Li insertion, facilitating Li diffusion as an adaptive pillar. Adaptive pillars are the specific structural features that differ from those of the conventional layered materials, and their effects are responsible for the high capacity of LLO materials. An essential understanding of the pillar effects will contribute to design guidelines for intercalation-type positive electrodes for next-generation LIBs., (© 2022 The Authors. Small published by Wiley-VCH GmbH.)

Abstract: The influence of two types of multi-walled carbon nanotubes, pristine (MWCNTs) and carboxylated (MWCNTs–COOH), on the electrochemical performance of LiNi0.33Co0.33Mn0.33O2 (NCM)- and LiFePO4 (LFP)-based positive electrodes is investigated. Several characterization techniques, e.g., electronic conductivity measurements, galvanostatic cycling, cyclic voltammetry, electrochemical impedance spectroscopy, and SEM/EDX, were employed. The results suggest that improved electronic conductivity is not necessarily synonymous with enhanced performance. A clear dependence of both rate capability and electrode morphology on the combination of conductive additive and active material can be observed. In particular, while LFP performs better with MWCNTs–COOH, pristine MWCNTs appear to be better suited for NCM. Although the use of MWCNTs–COOH improves the connective network between the active particles for both NCM and LFP, the presence of ties appears to have a strong effect on the surface properties of the NCM-based electrodes. MWCNTs–COOH formed a shell around the active particles, which may function as a physical barrier and hinder Li+ insertion/extraction. [Copyright &y& Elsevier]

Abstract: Three-dimensional LiNi0.5Mn0.5O2 (3D-LiNi0.5Mn0.5O2) nanostructures are in situ prepared using cryptomelane-type octahedral molecular sieve manganese dioxide (OMS-2) in the form of dendritic nanostructures as templates. The complete conversion of the OMS-2 precursor to layered α-NaFeO2-type LiNi0.5Mn0.5O2 and the retention of the 3D dendritic nanostructures have been confirmed by XRD, FE-SEM, TEM, and HR-TEM. The as-synthesized nanostructured positive electrode exhibits a significant improvement in rate performance and cycling reversibility due to its unique nanostructures composed of single-crystalline LiNi0.5Mn0.5O2 nanorods. And the influence of the assembly mode of nanosize LiNi0.5Mn0.5O2 positive electrode material to its electrochemical performances has been investigated. The battery based on 3D-LiNi0.5Mn0.5O2 retains a discharge capacity of 151.6mAhg−1 (93% of the first discharge capacity) after 50 cycles. A specific discharge capacity of 141.8mAhg−1 was retained at a rate of 3.2C, which is about 80% of the capacity at a rate of 0.2C. [Copyright &y& Elsevier]

Abstract: Li2−x VTiO4/C sample with a disordered rock salt structure was successfully prepared by annealing at a temperature of 850°C. The electrochemical oxidation in the first cycle occurs at voltages above 4V vs. metallic lithium, while the shapes of the electrochemical curves in consequent reduction–oxidation processes show a monotonous change of the potential between the selected cut-off voltages. A linear combination fit of individual XANES spectra was used for the determination of the oxidation states of as prepared sample and intermediate states during oxidation and reduction. In the as-prepared sample, vanadium was found to be in the average oxidation state of V3.5+ and was additionally oxidized to V3.8+ by the electrochemical charging. During the discharge process, the vanadium oxidation state was reduced to V3.0+. In situ X-ray diffraction patterns and EXAFS analysis suggest good structural stability during oxidation and reduction, which is also reflected in the cycling stability if batteries were cycled in the voltage window between 2.0V and 4.4V. Extension of the lower cut-off voltage to 1.0V doubles the capacity retention with the improved capacity stability if compared with several high capacity vanadium based materials. [Copyright &y& Elsevier]

Abstract: In the search of high-performance materials for lithium ion batteries, Li2CoPO4F offers many advantages like high theoretical capacity and high operating potential. The synthesis of Li2CoPO4F has been reinvestigated considering a conventional solid state reaction and an unconventional way. Due to the long heat-treatments required by the conventional approach, a beginning of grains coalescence is observed. Limiting particles growth has been allowed by a shorter reaction done by SPS (Spark Plasma Sintering). By this method, the synthesis of Li2CoPO4F was greatly shortened (from 10h to 9min), which favours the getting of submicrometric particles. The comparison of the electrochemical properties of the Li2CoPO4F obtained by the different ways confirms the advantages of SPS synthesis in performance enhancement. [ABSTRACT FROM AUTHOR]

Abstract: 57Fe Mössbauer spectroscopy is a powerful tool to investigate redox reactions during in electrochemical lithium insertion/extraction processes. Electrochemical oxidation of LiFeIIPO4 (triphylite) in Li-ion batteries results in FeIIIPO4 (heterosite). LiFePO4 was synthesized by solid state reaction at 800°C under Ar flow from Li2CO3, FeC2O4·2H2O and NH4H2PO4 precursors in stoichiometric composition. FePO4 was prepared from chemical oxidation of LiFePO4 using bromine as oxidative agent. For both materials a complete 57Fe Mössbauer study as a function of the temperature has been carried out. The Debye temperatures are found to be θ M=336K for LiFePO4 and θ M=359K for FePO4, leading to Lamb-Mössbauer factors f 300K=0.73 and 0.77, respectively. These data will be useful for a precise estimation of the relative amounts of each species in a mixture. [Copyright &y& Elsevier]

Abstract: Li-ion batteries are already used in many nomad applications, but improvement of this technology is still necessary to be durably introduced on new markets such as electric vehicles (EVs), hybrid electric vehicles (HEVs) or eventually photovoltaic solar cells. Modification of the nature of the active materials of electrodes is the most challenging and innovative aspect. High voltage spinel oxides for Li-ion batteries, with general composition LiMn2−x M x O4 (M a transition metal element), may be used to face increasing power source demand. It should be possible to obtain up to 240Whkg−1 at cell level when combining a nickel manganese spinel oxide with graphite (even more with silicon/carbon nanocomposites at the anode). Specific composition and material processing have to be selected with care, as discussed in this paper. It is demonstrated that ‘LiNi0.5Mn1.5O4’ and LiNi0.4Mn1.6O4 have remarkable properties such as high potential, high energy density, good cycle life and high rate capability. Choice of the electrolyte is also of primary importance in order to prevent its degradation at high voltage in contact with active surfaces. We showed that a few percents of additive in the electrolyte were suitable for protecting the positive electrode/electrolyte interface, and reducing the self-discharge. High voltage materials are also possibly interesting to be used in safe and high power Li-ion cells. In this case, the negative electrode may be made of Li4Ti5O12 or TiO2 to give a ‘3V’ system. [Copyright &y& Elsevier]

Abstract: A new type of 3-D flower-like monoclinic sodium ammonium vanadium bronze nano-architecture consisting of single crystalline nano-platelets was prepared. Under the hydrothermal condition, the intercalation of two kinds of cations (such as Na+ and ) induced structural transformations of the vanadium bronzes and gave rise to novel crystalline structures with specific morphologies. When used as positive electrode materials in rechargeable lithium battery, this sodium ammonium vanadium bronze exhibited high discharge capacity of ca. 200mAhg−1 in the range of 2–3.4V and excellent cycle stability. [Copyright &y& Elsevier]

Abstract: The high temperature reactions of 1M LiPF6 EC:DEC and LiCoO2, Li(Ni1/3Co1/3Mn1/3)O2 (NCM) or Li(Ni0.8Co0.15Al0.05)O2 (NCA) charged to 4.2V and 4.4V, respectively, were studied by accelerating rate calorimetry (ARC). The results indicate that NCM shows better thermal stability than both LiCoO2 and NCA. The state-of-the-art NCA sample shows better safety properties than LiCoO2. The reactivity of the samples depends on the electrolyte:active material ratio used during ARC testing. Electrode materials charged to 4.4V are more reactive than the electrode materials charged to 4.2V. These results should be useful for Li-ion battery researchers interested in maximizing the safety of high energy density cells and also as a benchmark for other researchers using ARC. [Copyright &y& Elsevier]

Abstract: The impact of the fluorine substitution on the electrochemical properties of layered lithium nickel manganese positive electrode materials for lithium ion batteries is summarized. The addition of a controlled amount of fluorine to the oxygen lattice can effectively improve the capacity retention as well as reduce the impedance of the positive electrode materials. The fluorination of the nickel and manganese based layered oxide cathode material has also led to significant improvement in cycle life and power capability of the battery. [Copyright &y& Elsevier]

Abstract: New olivines LiMAsO4 (M=Mn, Fe, Co, and Ni) have been tested as positive electrode in lithium cells. Under the used experimental conditions we did not succeed to remove lithium ions from LiFeAsO4, LiMnAsO4 or LiNiAsO4. More work is needed in order to verify whether the lack of electrochemical activity is intrinsic to these materials, or it is due to kinetical limitations such as particle size and poor conductivity. On the contrary lithium ions could be reversibly deinserted/inserted from/into LiCoAsO4 at average voltages of 4.8 and 4.6V respectively; the delithiated compound maintaining the olivine structural framework. The high pressure polymorph of LiMAsO4 (M=Fe, Co, Ni) crystallizing with the spinel structure did not show any electrochemical activity potentially useful in rechargeable lithium batteries. [Copyright &y& Elsevier]

The electrochemical performance of V2O5 has been studied in propylene carbonate (PC)-containing magnesium perchlorate [Mg(ClO4)2] electrolytes in view of their application as positive electrode in the rechargeable magnesium batteries. V2O5 exhibited good properties in hosting magnesium ions and its electrochemical performance depended on the amount of H2O in the electrolytes. The highest first discharge specific capacities of V2O5 electrode was up to 158.6 mAh/g in 1 mol dm-3 Mg(ClO4)2+1.79 mol dm-3 H2O/PC electrolytes. Electrochemical impedance spectroscopy (EIS) and charging–discharging tests showed that a reasonable amount of H2O in the electrolyte solution facilitated the electrochemical performance of V2O5 electrodes. [Copyright &y& Elsevier]