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The Li-rich Li[NiMn]O microspheres are firstly prepared and subsequently transferred into the AlO-coated Li-rich Li[NiMn]O microspheres by a simple deposition method. The as-prepared samples are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and charge/discharge tests. The results reveal that the AlO-coated Li-rich Li[NiMn]O sample has a typical α-NaFeO layered structure with the existence of LiMnO-type integrated component, and the AlO layer is uniformly coated on the surface of the spherical Li-rich Li[NiMn]O particles with a thickness of about 4 nm. Importantly, the AlO-coated Li-rich sample exhibits obviously improved electrochemical performance compared with the pristine one, especially the 2 wt.% AlO-coated sample shows the best electrochemical properties, which delivers an initial discharge capacity of 228 mAh g at a rate of 0.1 C in the voltage of 2.0-4.6 V, and the first coulombic efficiency is up to 90 %. Furthermore, the 2 wt.% AlO-coated sample represents excellent cycling stability with capacity retention of 90.9 % at 0.33 C after 100 cycles, much higher than that of the pristine one (62.2 %). Particularly, herein, the typical inferior rate capability of Li-rich layered cathode is apparently improved, and the 2 wt.% AlO-coated sample also shows a high rate capability, which can deliver a capacity of 101 mAh g even at 10 C. Besides, the thin AlO layer can reduce the charge transfer resistance and stabilize the surface structure of active material during cycling, which is responsible for the improvement of electrochemical performance of the Li-rich Li[NiMn]O. [ABSTRACT FROM AUTHOR]

Spherical Li[NiCoMn]O cathode materials with different microstructure have been prepared by a continuous carbonate co-precipitation method using LiOH⋅HO, LiCO, CHCOOLi⋅2HO and LiNO as lithium source. The effects of Li source on the physical and electrochemical properties of Li[NiCoMn]O are investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrochemical measurements. The results show that the morphology, tap density and high rate cycling performance of Li[NiCoMn]O spherical particles are strongly affected by Li source. Among the four Li sources used in this study, LiOH⋅HO is beneficial to enhance the tap density of Li[NiCoMn]O, and the tap density of as-prepared sample reaches 2.32 g cm. Meanwhile, LiCO is preferable when preparing the Li[NiCoMn]O with high rate cycling performance, upon extended cycling at 1 and 5C rates, 97.5% and 92% of the initial discharge capacity can be maintained after 100 cycles. [ABSTRACT FROM AUTHOR]

Sodium ion batteries (SIBs) are recognized as one of the most promising alternatives for large-scale application due largely to low-cost and sustainable supply-chain. The crucial task is to explore the next generation of cathode materials with satisfactory performances at low cost. In this work, Na 2 FePO 4 F/C nanocomposite (NFPF/C-PG) has been synthesized via liquid route using polyfurfuryl alcohol (PFA) as grain size controller followed by solid-state reaction using glucose as carbon sources. PFA formed in situ polymerization not only prohibits effectively the aggregation of nanoparticle, but also plays a vital role in the construction of carbon network. As a proof-of-concept application, the NFPF/C-PG shows outstanding electrochemical properties as cathode material for sodium ion batteries, which delivers discharge capacities of 73.8 mAh/g with retaining 86.1% of initial capacity over 200 cycles at 1C. Unlabelled Image • Na 2 FePO 4 F/C composite is synthesized with the synergism of polyfurfuryl alcohol. • The Na 2 FePO 4 F nanoparticles are uniformly distributed in graphitized carbon. • NFPF/C-PG shows excellent cycling performance and rate capability. [ABSTRACT FROM AUTHOR]

P2-type Fe/Mn-based oxides are considered as the competitive cathode materials for sodium-ion batteries because of high specific capacity and low material cost. However, it suffers from poor cycling stability and unsatisfactory rate capability. Herein, the lithium-doped Na 0.67 Li 0.1 Fe 0.4 Mn 0.5 O 2 microspheres are successfully synthesized via a three-step method. Benefiting from the synergetic effect of the double modification through the morphology controlling and lithium doping, the Na 0.67 Li 0.1 Fe 0.4 Mn 0.5 O 2 delivers an improved cycling stability and rate performance. Moreover, fluorine is successfully introduced to further improve the electrochemical performance of the Na 0.67 Li 0.1 Fe 0.4 Mn 0.5 O 2. Fluorine doping can boost the stability of the material crystal structure because of the strong electronegativity of fluorine and the stable fluorine-metal bond. Meanwhile, fluorine doping avoids the formation of extra O3 phase by reducing the average valence of transition metals. Most importantly, P2-type 10 mol% F-Na 0.67 Li 0.1 Fe 0.4 Mn 0.5 O 2 shows a high discharge specific capacity of 182.0 mAh g-1 at 20 mA g-1, excellent capacity retention of 90.0% after 50 cycles and outstanding rate performance of 128.7 mAh g−1 at 400 mA g-1. Apparently, such a modification strategy apparently promotes the electrochemical performances of the P2-type Fe/Mn-based oxide and increases the commercial application possibilities of this cathode material in sodium-ion batteries. • P2/O3-type Li-doped NLFMO microspheres are successfully synthesized. • NLFMO microspheres delivers improved cycling stability and rate performance. • Pure P2-type NLFMO microspheres are synthesized by 10 mol% fluorine doping. • P2-type 10 mol% F-NLFMO displays higher specific capacity than NLFMO. • P2-type 10 mol% F-NLFMO also shows better cyclic stability and rate capability. [ABSTRACT FROM AUTHOR]

Nickel-rich layered cathodes have received extensive attention because of their relatively high energy density. However, the poor rate performance and inadequate cycling stability severely hinder its large-scale applications. Herein, a multi-functional modification strategy combining dual-site Mg/Nb co-doping with in-situ derived LiNbO 3 coating layer is proposed. Mg2+ doped as pillar ions at Li sites can reduce the disorder of Li+/Ni2+, while Nb5+ doped at transition metal sites can improve structural stability due to its stronger Nb-O binding energy. Moreover, LiNbO 3 ionically conductive nano-scale coating layer can effectively improve interface properties of the material. Benefitting from the synergistic effect of multi-functional modification strategy, the LiNi 0.83 Co 0.12 Mn 0.05 O 2 cathode material co-modified with 2 mol% Mg and 1.4 mol% Nb exhibits extraordinarily enhanced electrochemical performance, which can display an excellent capacity retention of 84.1% after 200 cycles at 1 C and a high specific capacity of 132.9 mAh g−1 at the ultra-high rate of 30 C. Furthermore, the multi-functional modification strategy can also effectively alleviate grain-level intergranular cracks and structural degradation during long-term cycling. These results demonstrate that simultaneously using two types of doping cations together with in situ derived coating layer is an efficient and feasible modification strategy for Ni-rich layered cathodes. [ABSTRACT FROM AUTHOR]

The Mn doped spherical Li 2 FeSiO 4 /C cathode materials are successfully synthesized through a citric acid-assisted sol-gel method. The effects of Mn doping on the chemical composition, structure characteristics, morphology and elemental distribution of the as-prepared polyanionic cathode materials are investigated by the inductively coupled plasma optical emission spectroscopy (ICP-OES), X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscope (TEM) and energy-dispersive X-ray spectroscope (EDX). The results indicate that the alien atom Mn can effectively and equably dope into the samples as well as maintain the original spherical morphology. Besides, the electrochemical measurements reveal that the sample doped with 5% Mn delivers the highest initial discharge capacity of 248.5 mAh g −1 at 0.1C under ambient temperature in a voltage range of 1.5–4.8 V, the retention of the capacity is as high as 91.9% after 200 cycles. Additionally, the sample doped with 5% Mn also exhibits a good rate capability with a discharge capacity of 105.6 mAh g −1 even at a high rate of 10C. The excellent electrochemical performances can be ascribed to the appropriate Mn doping, which can effectively optimize the crystal structure of Li 2 FeSiO 4 /C and facilitate the diffusion coefficient of lithium-ion during cycling process. [ABSTRACT FROM AUTHOR]

Although FeF 3 and its hydrates have been studied as the cathode materials for Li ion batteries (LIBs), herein the FeF 3 /graphene composite with sheet-like structure is innovatively prepared and used as LIB cathode material. By scanning electron microscope (SEM), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), X-ray diffraction (XRD) and electrochemical measurement, the structure and electrochemical performance of the as-synthesized FeF 3 /graphene composite are investigated. The results indicate that the sheet-like structure hybrid is formed by the FeF 3 nanosheets and the graphene sheets. Meantime, we demonstrate that the FeF 3 /graphene composite has good rate capability and cycling performance, whether it is based on conventional intercalation reaction or reversible conversion reactions. [ABSTRACT FROM AUTHOR]

The structure design strategy for LRO based on the reversible anionic redox and spinel-layered coherent structure is propitious to maintaining high specific capacity and improving the reversible anionic redox and stable cyclic performance of LRO. [Display omitted] • LRO cathode with reversible anionic redox and spinel-layered coherent structure is designed. • The specific capacity and initial Coulombic efficiency are enhanced by the introduction of S-anions. • Stable interface structure and enhanced electrochemical kinetics are realized by the spinel-layered coherent structure. • Improved specific capacity and excellent cyclic stability are revealed in the modified LRO. Initiating effective strategies to improve the reversibility of anionic redox and structural stabilization is crucial to the development and industrial application of Li-rich cathode materials (LRO), which are regarded as the preferred option of the cathode materials for the next-generation lithium-ion battery with high energy density. To remit the unexpected behavior of structural destruction and capacity attenuation, this paper proposes a strategy for maintaining high specific capacity and improving the reversible anionic redox and stable cyclic performance of LRO by introducing the spinel-layered coherent structure and S-anions. Proved by the ex-situ X-ray photoelectron spectroscopy, S-anions can regulate the anionic redox reversibility and thus enhance the reversible discharge capacity and initial Coulombic efficiency. Moreover, the structural stability is greatly improved by the introduction of spinel-layered coherent structure and S-anions in LRO, which has been confirmed by abundant structural characterizations. Besides, the results reveal that the optimized material exhibits a high reversible discharge capacity of 289.52 mAh/g and good cyclic performance with a retention rate of 88.21% after 200 cycles. Evidently, the structure design strategy for LRO based on the reversible anionic redox and spinel-layered coherent structure is a significant exploration, which will bring a new clew for the design of the cathode materials with high-energy–density and excellent electrochemical performance. [ABSTRACT FROM AUTHOR]

Highlights: [•] The Y2O3 coated LiMn2O4 microsphere wrapped with graphene is firstly synthesized. [•] The graphene/Y2O3/LiMn2O4 hybrid shows the notable rate and cycling performance. [•] Y2O3 and graphene modification can effectively improve the performance of material. [ABSTRACT FROM AUTHOR]

Highlights: [•] BiPO4 is initially reported as a cathode material for lithium-ion batteries. [•] We have explored that BiPO4 is a cathode material based on conversion reactions. [•] Its theoretical specific capacity and output voltage are 264.5mAhg−1 and 3.14V. [•] Its theoretical volumetric energy density is close to twice higher than LiCoO2. [•] Effects of the phase transformation on electrochemistry of BiPO4 are discussed. [ABSTRACT FROM AUTHOR]

Abstract: In order to improve the performance of the Li[Ni0.5Co0.2Mn0.3]O2, a novel spherical Li[Ni0.5Co0.2Mn0.3]O2–Li2MnO3 core–shell composite has been successfully synthesized by a simple sol–gel deposition method. It is found that the core–shell composite consists of Li[Ni0.5Co0.2Mn0.3]O2 as the core and Li2MnO3 as the outer shell according to examination by scanning electron microscope (SEM) with energy dispersive X-ray spectroscopy (EDXS) and X-ray diffraction (XRD). The core–shell composite delivers a high capacity of 180.4 mAh g−1 at a rate of 0.1 C in the voltage range of 2.0–4.4 V. Most importantly, the core–shell composite exhibits excellent capacity retention of 98.8% after 200 cycles at a rate of 0.5 C, and 93.8% capacity retention after 100 cycles at a rate of 5 C at room temperature. When cycled at an elevated 55 °C, the prepared sample exhibits only 2.3% capacity loss after 100 cycles. Meanwhile, the core–shell composite shows significantly improved thermal stability relative to that of the pristine Li[Ni0.5Co0.2Mn0.3]O2. The improved stability of the core–shell composite is ascribed to the stable Li2MnO3 outer shell, which can prevent the Li[Ni0.5Co0.2Mn0.3]O2 core from direct contact with the electrolyte, and the core material could operate with no risk of structural disruption at high voltages and high temperatures. [Copyright &y& Elsevier]

Abstract: The pristine LiFePO4/C and Ni and Mn co-doping LiFe1−x−y Ni x Mn y PO4/C (x = 0.01–0.04; y = 0.04–0.01) composites are synthesized for the first time by a simple high-temperature solid-state route. The structure, morphology and electrochemical performance of the samples are characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectra, scanning electron microscope (SEM), charge/discharge tests and electrochemical impedance spectroscopy (EIS). The results indicate that the Ni and Mn co-doping does not destroy the olivine structure of LiFePO4, but it can stabilize the crystal structure, lengthen the Li–O bond, decrease charge transfer resistance, enhance Li ion diffusion velocity, and thus improve its cycling and high-rate capability of the LiFePO4/C. Especially, the LiFe0.95Ni0.02Mn0.03PO4/C shows the best cycling stability and rate capability among all the doped samples. The first discharge capacity of LiFe0.95Ni0.02Mn0.03PO4/C is 145.4 mAh g−1 with the capacity retention ratio of 98.6% till 100 cycles at 1C. Even at a high rate of 10C, it still reveals a high discharge capacity of 115.2 mAh g−1. [Copyright &y& Elsevier]

Abstract: Na and Ti co-doping Li1−x Na x Fe1−x Ti x PO4/C (x =0.00, 0.01, 0.03 and 0.05) composites were synthesized by a simple high-temperature solid-state method. The structure, morphology and electrochemical performance of the samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), charge/discharge tests, electrochemical impedance spectroscopy (EIS) and galvanostatic intermittent titration technique (GITT). The results showed that the Na and Ti co-doped samples kept the olivine structure of LiFePO4, but Na and Ti co-doping can optimize the crystal microstructure, modify the particle morphology, decrease charge transfer resistance, enhance exchange current density, electrical conductivity and Li ion diffusion velocity, and thus improve the electrochemical performance of the LiFePO4/C. Among all the doped samples, Li0.97Na0.03Fe0.97Ti0.03PO4/C showed the best rate capability and cycling stability. The initial discharge capacity of Li0.97Na0.03Fe0.97Ti0.03PO4/C was 151.0mAhg−1 with the capacity retention ratio of 99.3% after 100 cycles at 1C. Especially, it still showed a high discharge capacity of over 97.3mAhg−1 even at a high rate of 20C. [Copyright &y& Elsevier]

• Construct Mn 3 O 4 protective shell to alleviate Jahn-Teller distortion. • Oxygen vacancy can effectively restrain the release of oxygen. • The designed LRNMO@Mn 3 O 4 cathode has higher electron/ion conductivity. • The Mn 3 O 4 -coated electrode exhibited excellent cycle stability. Herein, we put forward a feasible interfacial modification strategy in virtue of Mn 3 O 4 surface coating to construct protective shell and alleviate Jahn-Teller distortion during the charge/discharge process. It has been found that the increase of the oxygen vacancy on the surface of Li 1.2 Ni 0.27 Mn 0.54 O 2 of (LRNMO) after Mn 3 O 4 protective layer modification can effectively restrain the release of oxygen and enhancing rate capability, and thus improving its comprehensive electrochemical performances. In particular, the initial coulombic efficiency of the optimized LRNMO-1 electrode is improved from 72.3% to 84.3%. The capacity retention rate is up to 95.6% at 250 mA g−1 (1C) after 200 cycles. In addition, the LRNMO-1 electrode also has a good capacity retention rate (96.4% after 100 cycles) at a high current density of 5C. Moreover, the designed LRNMO@Mn 3 O 4 cathode exhibits higher ionic conductivity and better interface stability. As a result, this work offers a practicable and valuable exploration for the development and industrialization of Co-free Li-rich Mn-based cathode materials with high energy density. [ABSTRACT FROM AUTHOR]

Hexagonal BiPO4 is precipitated from a solution of Bi(NO3)3 in 10 wt.% aq. [ABSTRACT FROM AUTHOR]