Exploration of Spinel LiCrTiO4 as Cathode Material for Rechargeable Mg-Li Hybrid Batteries.

Mg-Li hybrid batteries have attracted wide interest in recent years because of their potential safety as well as their cost benefit and high volumetric capacity. However, slow kinetic properties strongly hinder their commercial application. In this study, we have prepared spinel LiCrTiO4 by a solid-state reaction and have conducted a comprehensive study aimed at improving the performance of Mg-Li hybrid batteries by optimizing the dual-salt electrolyte. LiCrTiO4 has been found to show reversible discharge/charge capacities of 178 and 169 mA h g-1 in electrolytes of 1 m LiCl and 0.3 m APC (all-phenyl-complex), respectively. When the concentration of APC was increased to 0.4 m, LiCrTiO4 showed a high capacity retention of 95 % after 30 cycles. In addition, no phase transition could be observed for an LiCrTiO4 electrode in a dual-salt system, suggesting high electrochemical reversibility. Ex situ EDX and SEM studies have indicated that only Li+ ions are inserted into the cathode side, while Mg2+ ions are reversibly deposited on the surface of Mg metal without dendrite-like growth, indicative of good safety of the Mg-Li hybrid batteries.

Sodium vanadium titanium phosphate electrode for symmetric sodium-ion batteries with high power and long lifespan.

Sodium-ion batteries operating at ambient temperature hold great promise for use in grid energy storage owing to their significant cost advantages. However, challenges remain in the development of suitable electrode materials to enable long lifespan and high rate capability. Here we report a sodium super-ionic conductor structured electrode, sodium vanadium titanium phosphate, which delivers a high specific capacity of 147 mA h g-1 at a rate of 0.1 C and excellent capacity retentions at high rates. A symmetric sodium-ion full cell demonstrates a superior rate capability with a specific capacity of about 49 mA h g-1 at 20 C rate and ultralong lifetime over 10,000 cycles. Furthermore, in situ synchrotron diffraction and X-ray absorption spectroscopy measurement are carried out to unravel the underlying sodium storage mechanism and charge compensation behaviour. Our results suggest the potential application of symmetric batteries for electrochemical energy storage given the superior rate capability and long cycle life.

NASICON-Structured NaTi2(PO4)3@C Nanocomposite as the Low Operation-Voltage Anode Material for High-Performance Sodium-Ion Batteries.

NASICON-type structured NaTi2(PO4)3 (NTP) has attracted wide attention as a promising anode material for sodium-ion batteries (SIBs), whereas it still suffer from poor rate capability and cycle stability due to the low electronic conductivity. Herein, the architecture, NTP nanoparticles embedded in the mesoporous carbon matrix, is designed and realized by a facile sol-gel method. Different than the commonly employed potentials of 1.5-3.0 V, the Na(+) storage performance is examined at low operation voltages between 0.01 and 3.0 V. The electrode demonstrates an improved capacity of 208 mAh g(-1), one of the highest capacities in the state-of-the-art titanium-based anode materials. Besides the high working plateau at 2.1 V, another one is observed at approximately 0.4 V for the first time due to further reduction of Ti(3+) to Ti(2+). Remarkably, the anode exhibits superior rate capability, whose capacity and corresponding capacity retention reach 56 mAh g(-1) and 68%, respectively, over 10000 cycles under the high current density of 20 C rate (4 A g(-1)). Worthy of note is that the electrode shows negligible capacity loss as the current densities increase from 50 to 100 C, which enables NTP@C nanocomposite as the prospective anode of SIBs with ultrahigh power density.

P2-NaCo(0.5)Mn(0.5)O2 as a Positive Electrode Material for Sodium-Ion Batteries.

As a promising positive electrode material for sodium-ion batteries (SIBs), layered sodium oxides have attracted considerable attention in recent years. In this work, stoichiometric P2-phase NaCo(0.5)Mn(0.5)O2 was prepared through the conventional solid-state reaction, and its structural and physical properties were studied in terms of XRD, XPS, and magnetic susceptibility. Furthermore, the P2-NaCo(0.5)Mn(0.5)O2 electrode delivered a discharge capacity of 124.3 mA h g(-1) and almost 100% initial coulombic efficiency over the potential window of 1.5-4.15 V. It also showed good cycle stability, with a reversible capacity and capacity retention reaching approximately 85 mA h g(-1) and 99%, respectively, at the 5 C rate after 100 cycles. Additionally, cyclic voltammetry and ex situ XRD were employed to explain the electrochemical behavior at the different electrochemical stages. Owing to the applicable performances, P2-NaCo(0.5)Mn(0.5)O2 can be considered as a potential positive electrode material for SIBs.

Preparation and Electrochemical Properties of Tin-Iron-Carbon Nanocomposite as the Anode of Lithium-Ion Batteries.

Tin-iron-carbon nanocomposite is successfully prepared by a sol-gel method followed by a chemical vapor deposition (CVD) process with acetylene gas as the carbon source. The structural properties, morphology, and electrochemical performances of the nanocomposite are comprehensively studied in comparison with those properties of tin-carbon and iron-carbon nanocomposites. Sheet-like carbon architecture and different carbon contents are induced thanks to the catalytic effect of iron during CVD. Among three nanocomposites, tin-iron-carbon demonstrates the highest reversible capacity of 800 mA h g(-1) with 96.9% capacity retention after 50 cycles. It also exhibits the best rate capability with a discharge capacity of 420 mA h g(-1) at a current density of 1000 mA g(-1). This enhanced performance is strongly related to the carbon morphology and content, which can not only accommodate the large volume change, but also improve the electronic conductivity of the nanocomposite. Hence, the tin-iron-carbon nanocomposite is expected to be a promising anode for lithium-ion batteries.

Brannerite-Type Vanadium-Molybdenum Oxide LiVMoO6 as a Promising Anode Material for Lithium-Ion Batteries with High Capacity and Rate Capability.

Brannerite-type vanadium-molybdenum oxide LiVMoO6 is prepared by a facile liquid-phase method, and its electrochemical properties as anode of lithium-ion batteries are comprehensively studied by means of galvanostatic charge-discharge profiles, rate performance, and cyclic voltammetry. In the working voltage between 3.0 and 0.01 V, LiVMoO6 delivers a high reversible capacity of more than 900 mAh g(-1) at the current density of 100 mA g(-1) and a superior rate capability with discharge capacity of ca. 584 and 285 mAh g(-1) under the high current densities of 2 and 5 A g(-1), respectively. Moreover, ex situ X-ray diffraction and X-ray photoelectron spectroscopy are utilized to examine the phase evolution and valence changes during the first lithiated process. A small amount of inserted Li(+) induces a decomposition of LiVMoO6 into Li2Mo2O7 and V2O5, which play the host during further lithiated processes. When being discharged to 0.01 V, most V(5+) change into V(3+)/V(2+), suggesting intercalation/deintercalation processes, whereas Mo(6+) are reduced into a metallic state on the basis of the conversion reaction. The insights obtained from this study will benefit the design of novel anode materials for lithium-ion batteries.

Carbon and RuO2 binary surface coating for the Li3V2(PO4)3 cathode material for lithium-ion batteries.

RuO2 nanocrystals are successfully impregnated into the surface carbon layer of the Li3V2(PO4)3/C cathode material by the precipitation method. Transmission electron microscopy shows that the RuO2 particles uniformly embed in the surface carbon layer. Cyclic voltammetry and electrochemical impedance spectroscopy indicate that the coexistence of carbon and RuO2 enables high conductivity for both Li ions and electrons and thus stabilizes the interfacial properties of the electrode, facilitates the charge transfer reactions, and improves the Li(+) diffusion in the electrode. As a result, the Li3V2(PO4)3 cathode coated with the binary surface layer shows improved rate capability and cycle stability. Particularly, the material containing 2.4 wt % Ru exhibits the best electrochemical performance and delivers a discharge capacity of 106 mAh g(-1) at the 10 C rate with a capacity retention of 98.4% after 100 cycles.

LiFe(MoO4)2 as a novel anode material for lithium-ion batteries.

Polycrystalline LiFe(MoO4)2 is successfully synthesized by solid-state reaction and examined as anode material for lithium-ion batteries in terms of galvanostatic charge-discharge cycling, cyclic voltammograms (CV), galvanostatic intermittent titration technique (GITT), and electrochemical impedance spectroscopy (EIS). The LiFe(MoO4)2 electrode delivers a high capacity of 1034 mAh g(-1) at a current density of 56 mA g(-1) between 3 and 0.01 V, indicating that nearly 15 Li(+) ions are involved in the electrochemical cycling. LiFe(MoO4)2 also exhibits a stable capacity of 580 mAh g(-1) after experiencing irreversible capacity loss in the first several cycles. Moreover, the Li-ion storage mechanism for LiFe(MoO4)2 is suggested on the basis of the ex situ X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) at different insertion/extraction depths. A successive structural transition from triclinic structure to cubic structure is observed, and the tetrahedral coordination of Mo by oxygen in LiFe(MoO4)2 changes to octahedral coordination in Li2MoO3, correspondingly. When being discharged to 0.01 V, the active electrode is likely to be composed of Fe and Mo metal particles and amorphous Li2O due to the multielectron conversion reaction. The insights obtained from this study will benefit the design of new anode materials for lithium-ion batteries.

Synthesis of H2 V3 O8 /Reduced Graphene Oxide Composite as a Promising Cathode Material for Lithium-Ion Batteries.

H2 V3 O8 nanowires wrapped by reduced graphene oxide (RGO) are synthesized successfully through a simple hydrothermal process. The structural properties of the samples are characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Raman scattering, and X-ray photoelectron spectroscopy. The RGO nanosheets modify the surfaces of the H2 V3 O8 nanowires through VC linkages. The H2 V3 O8 /RGO composite exhibits a remarkably enhanced electrochemical performance in terms of its reversible capacity, cyclic performance, and rate capability. The material shows high discharge capacities of 256 and 117 mA h g-1 at the current densities of 0.1 and 1 A g-1 , respectively, with almost no capacity fading after fifty charge/discharge cycles. Cyclic voltammetry and electrochemical impedance spectroscopy show that the superior electrochemical performance of H2 V3 O8 /RGO can be attributed to the cooperation of RGO, which provides better mechanical flexibility, higher electronic conductivity, and smaller charge-transfer resistance.