Xiaofei Bie

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.

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.

Na3V2(PO4)3/C composite as the intercalation-type anode material for sodium-ion batteries with superior rate capability and long-cycle life

A Na3V2(PO4)3/C (NVP/C) composite is successfully synthesized by the sol–gel method and examined as the anode material for sodium-ion batteries (SIBs) by means of galvanostatic charge–discharge profiles, cyclic voltammograms, rate performance and cyclic voltammetry comprehensively. The NVP/C electrode delivers a reversible capacity of about 170 mA h g−1 between 3.0 and 0.01 V at a current density of 20 mA g−1 corresponding to three sodium ions insertion/extraction processes. Besides the voltage plateau at 1.57 V, another novel working platform at around 0.28 V is found for the first time in both charging and discharging profiles, possibly owing to the further reduction of vanadium. NVP/C exhibits an excellent rate capability and long-cycle stability with a capacity retention of 62% after 3000 cycles at a high charge rate of 10 C (2 A g−1). Moreover, the intercalation-type Na-ions storage mechanism is proposed on the basis of ex situ X-ray diffraction and high-resolution transmission electron microscopy. Our findings reveal that the NVP/C sample is a promising anode material for SIBs due to its superior rate capability and long cycle life.

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.

Electrochemical properties and lithium-ion storage mechanism of LiCuVO4 as an intercalation anode material for lithium-ion batteries

LiCuVO4 with distorted inverse spinel structure is prepared by solid-state reaction and comprehensively examined as an intercalation anode material by means of cyclic voltammograms (CV), galvanostatic charge–discharge profiles, rate performance, and electrochemical impedance spectroscopy (EIS). LiCuVO4 shows a stable capacity of 447 mA h g−1 under 3–0.01 V at the current density of 200 mA g−1, and the capacity retention reaches 91% after 50 cycles. At high cutoff voltage, between 3 and 0.2 V, LiCuVO4 also delivers an average reversible capacity of 200 mA h g−1 at a current density of 2000 mA g−1, higher than the performance of the newly reported Li3VO4. Moreover, the lithium ion storage mechanism for LiCuVO4 is also explained on the basis of the ex situ X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) at different insertion/extraction depths. While being discharged to 0.01 V, LiCuVO4 decomposes into Li3VO4, whose surface is coated by Cu nanoparticles spontaneously. Interestingly, Li ions are suggested to be inserted into Li3VO4 in the subsequent cycles due to the intercalation mechanism, and Cu nanoparticles would not contribute to the reversible capacity. Our findings provide a strong supplemental insight into the electrochemical mechanism of the anode for lithium-ion batteries. In addition, LiCuVO4 is expected to be a potential anode material because of its low cost, simple preparation procedure, good electrochemical performance and safety discharge voltage.

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.

Cluster-spin-glass behavior in layered LiNi0.4Mn0.4Co0.2O2

Layered LiNi0.4Mn0.4Co0.2O2 has been synthesized by citrate precursor method. Its magnetic properties are investigated by dc magnetization. The high-temperature susceptibility curve follows the Curie–Weiss law with Curie and Weiss constant 1.435(2) emu K/mol Oe and −112(4) K, respectively, larger than those values reported in previous researches, which possibly results from the difference in the synthesis process and sintered temperature. Our dc susceptibility differs from that of the homogeneous spin glass in that below Tirr field cooled (FC) curve continues to rise, while the FC curve is almost flat for homogeneous spin glass. Together with the de Almeida–Thouless line analysis, cluster spin glass is suggested to be the ground state of LiNi0.4Mn0.4Co0.2O2. Frustration parameter |θ|/Tf in this system is estimated to be about four, lower than the value that frustration effect is strong enough to give rise to spin glass state. This fact indicates that the cluster-spin-glass results from the short–range str...

Revisiting the layered LiNi0.4Mn0.4Co0.2O2: a magnetic approach

Layered LiNi0.4Mn0.4Co0.2O2 has been synthesized by the co-precipitation method, and the structural, electrochemical and magnetic properties were comprehensively studied by Rietveld analysis, charge–discharge potential profiles, X-ray photoelectron spectroscopy, and dc and ac susceptibilities. The material shows initial discharge capacities of 166 and 206 mA h g−1 in potential windows of 2.5–4.4 V and 2.5–4.6 V, respectively, and a better capacity retention of 95% at 2.5–4.4 V after 50 cycles. The effective paramagnetic moment is calculated to be 3.02(3) μB/f.u. by fitting to the Curie–Weiss law, which is consistent with the averaged value, based on the specific contributions, as quantified by an analysis of the X-ray photoelectron spectroscopy data. The dc magnetization curves show irreversibility and spin freezing behavior at 77 K and 18 K, respectively. The evolution of irreversibility temperature under different applied fields indicates a spin-glass-like transition. The ac susceptibility data and the fitting using the frequency dependent spin-freezing temperatures also confirm this magnetic transition. In comparison with the previous results, the co-precipitation prepared sample shows a big difference in the magnetic parameters, coming from the different microscopic exchange interactions or the formation of a different scale of spin clusters, which is sensitive to the preparation procedure.

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.

High capacity and rate capability of a layered Li2RuO3 cathode utilized in hybrid Na+/Li+ batteries

A novel hybrid Na+/Li+ battery is established by using Li2RuO3 as the cathode, 1 M NaClO4 in 1 : 1 EC/PC solution as the electrolyte and metallic sodium as the anode. In the working voltages between 2.0 and 4.0 V, Li2RuO3 delivers a high discharge capacity of 168 mA h g−1 under the current density of 0.1 A g−1 and an excellent capacity retention of about 88.1% after 50 cycles. The cathode also exhibits superior rate capability and long-term cycle life, whose discharge capacity reaches 85 mA h g−1 after 300 cycles at the current density of 1 A g−1. Importantly, both Na+ and Li+ can reversibly intercalate/deintercalate into Li2RuO3 in the same manner as in the typical Li-ion half cell. In addition, ex situ X-ray diffraction patterns of the initial charge and discharge processes as well as after long electrochemical cycles are examined to study its structural evolution. Our studies provide a strong insight into the design and application of novel rechargeable batteries.