Malin Li

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.

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.

Ultrafast lithium storage in TiO2–bronze nanowires/N-doped graphene nanocomposites

A TiO2–bronze/N-doped graphene nanocomposite (TiO2–B/NG) is prepared by a facile hydrothermal combined with hydrazine monohydrate vapor reduction method. The material exhibits macro- and meso-porosity with a high specific surface area of 163.4 m2 g−1. X-Ray photoelectron spectroscopy confirms the successful doping of nitrogen in the graphene sheets. In addition, the TiO2–B nanowires are substantially bonded to the NG sheets. Cyclic voltammetry and electrochemical impedance spectroscopy show that the N-doped graphene improves the electron and Li ion transport in the electrode which results in better electrochemical kinetics than that of the pristine TiO2–B nanowires. As a result, the charge transfer resistance of the TiO2–B/NG electrode is significantly reduced. In addition, the lithium diffusion coefficient of TiO2–B/NG increases by about five times with respect to that of pristine TiO2–B. The TiO2–B/NG composite exhibits a remarkably enhanced electrochemical performance compared to that of TiO2–B. It shows a discharge capacity of 220.7 mA h g−1 at the 10C rate with a capacity retention of 96% after 1000 cycles. In addition, it can deliver a discharge capacity of 101.6 mA h g−1 at an ultra high rate of 100C, indicating its great potential for use in high power lithium ion batteries.

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.

P2‐NaCo0.5Mn0.5O2 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.

Synthesis and electrochemical properties of highly crystallized CuV2O6 nanowires

CuV2O6 nanowires were prepared via a simple hydrothermal route using NH4VO3 and Cu(NO3)2 as starting materials. The structures and electrochemical properties of CuV2O6 nanowires were characterized by means of X-ray diffraction(XRD), scanning electron microscopy(SEM) and transmission electron microscopy(TEM). The results show that the CuV2O6 nanowires are about 100 nm in width and single crystalline grown along [001] direction. CuV2O6 nanowires delivered a high initial discharge capacity of 435 and 351 mA·h/g at current densities of 50 and 100 mA·h/g, respectively. The electrochemical kinetics of the CuV2O6 nanowires was also investigated by means of electrochemical impedance spectroscopy(EIS) and the poor rate performance was observed, which may be attributed to the low ion diffusion coefficient of the CuV2O6 nanowires.

P2-NaCo0.5Mn0.5O2as 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.

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.