Jinju Song

High rate performance of a Na3V2(PO4)3/C cathode prepared by pyro-synthesis for sodium-ion batteries

A Na3V2(PO4)3/C cathode synthesized by a polyol-assisted pyro-synthetic reaction and subsequent sintering delivered a discharge capacity of 235 mA h g−1, corresponding to an extraction of 4 Na per formula with steady capacity retention and impressive rate capabilities that maintain 56% of theoretical capacity at 2.67 C.

Co3V2O8 Sponge Network Morphology Derived from Metal–Organic Framework as an Excellent Lithium Storage Anode Material

Metal-organic framework (MOF)-based synthesis of battery electrodes has presntly become a topic of significant research interest. Considering the complications to prepare Co3V2O8 due to the criticality of its stoichiometric composition, we report on a simple MOF-based solvothermal synthesis of Co3V2O8 for use as potential anodes for lithium battery applications. Characterizations by X-ray diffraction, X-ray photoelectron spectroscopy, high resolution electron microscopy, and porous studies revealed that the phase pure Co3V2O8 nanoparticles are interconnected to form a sponge-like morphology with porous properties. Electrochemical measurements exposed the excellent lithium storage (∼1000 mAh g(-1) at 200 mA g(-1)) and retention properties (501 mAh g(-1) at 1000 mA g(-1) after 700 cycles) of the prepared Co3V2O8 electrode. A notable rate performance of 430 mAh g(-1) at 3200 mA g(-1) was also observed, and ex situ investigations confirmed the morphological and structural stability of this material. These results validate that the unique nanostructured morphology arising from the use of the ordered array of MOF networks is favorable for improving the cyclability and rate capability in battery electrodes. The synthetic strategy presented herein may provide solutions to develop phase pure mixed metal oxides for high-performance electrodes for useful energy storage applications.

Pyro-synthesis of a high rate nano-Li3V2(PO4)3/C cathode with mixed morphology for advanced Li-ion batteries.

A monoclinic Li3V2(PO4)3/C (LVP/C) cathode for lithium battery applications was synthesized by a polyol-assisted pyro-synthesis. The polyol in the present synthesis acts not only as a solvent, reducing agent and a carbon source but also as a low-cost fuel that facilitates a combustion process combined with the release of ultrahigh exothermic energy useful for nucleation process. Subsequent annealing of the amorphous particles at 800°C for 5 h is sufficient to produce highly crystalline LVP/C nanoparticles. A combined analysis of X-ray diffraction (XRD) and neutron powder diffraction (NPD) patterns was used to determine the unit cell parameters of the prepared LVP/C. Electron microscopic studies revealed rod-type particles of length ranging from nanometer to micrometers dispersed among spherical particles with average particle-sizes in the range of 20–30 nm. When tested for Li-insertion properties in the potential windows of 3–4.3 and 3–4.8 V, the LVP/C cathode demonstrated initial discharge capacities of 131 and 196 mAh/g (~100% theoretical capacities) at 0.15 and 0.1 C current densities respectively with impressive capacity retentions for 50 cycles. Interestingly, the LVP/C cathode delivered average specific capacities of 125 and 90 mAh/g at current densities of 9.6 C and 15 C respectively within the lower potential window.

Fully activated Li2MnO3 nanoparticles by oxidation reaction

Fully activated Li2MnO3 nanoparticles were prepared by a chemical based oxidation reaction. All of the diffraction peaks of the prepared samples were well matched to a monoclinic phase (space group: C2/m) with no impurity peaks and refined using the General Structure Analysis System (GSAS) program. The activated Li2MnO3 sample showed homogeneously well-dispersed nanoparticles with a size of ∼10 nm. The oxidation state of Mn was confirmed by XPS. The activated Li2MnO3 nanoparticles delivered a high charge capacity of 302 mA h g−1 above 4.5 V and discharge capacity of 236 mA h g−1 during the first cycle. Interestingly, the cycle performance of the activated Li2MnO3 nanoparticles during extended cycles exhibited somewhat stable discharge capacities without any drastic capacity fading, even when cycled in the high voltage range of 2.0–4.9 V and after the phase transition to spinel. In terms of the rate performance, the activated Li2MnO3 sample exhibited significantly superior properties compared to the bulk Li2MnO3 sample, probably due to the nano-size particles with high crystallinity.

High rate performance of a NaTi2(PO4)3/rGO composite electrode via pyro synthesis for sodium ion batteries

The present study reports on a highly rate capable NASICON-structured NaTi2(PO4)3/reduced graphene oxide (NTP/rGO) composite electrode synthesized by polyol-assisted pyro synthesis for Na-ion batteries (NIBs). X-ray diffraction (XRD) studies confirmed the presence of a rhombohedral NaTi2(PO4)3 phase in the composite while Raman spectroscopy studies helped to identify the existence of rGO in the composite. Electron microscopy studies established that NaTi2(PO4)3 nanoparticles of average sizes ranging between 20 and 30 nm were uniformly distributed and embedded in the GO sheets. When tested for sodium storage properties, the obtained NTP/rGO composite electrode registered high rate capacities (95 mA h g−1 at 9.2C and 78 mA h g−1 at 36.8C) when compared to that of the NTP/C electrode (∼1 mA h g−1 at 9.2 and 36.8C). Further, the NTP/rGO composites delivered a reversible capability of 62 mA h g−1 at 20C after 1000 cycles. The enhanced performance of the composite electrode can be attributed to the nano-sized NaTi2(PO4)3 particles with shorter diffusion path lengths. These particles embedded in the rGO sheets with enhanced electrolyte/electrode contact areas ultimately lead to an improvement in the electrical conductivity at high current densities. Ex situ XANES studies confirmed reversible Na-ion intercalation/de-intercalation into/from NTP/rGO. The study thus demonstrates that the NaTi2(PO4)3/rGO nanocomposite electrode is a promising candidate for the development of high power/energy density anodes for NIBs.

Pyro-Synthesis of Functional Nanocrystals

Despite nanomaterials with unique properties playing a vital role in scientific and technological advancements of various fields including chemical and electrochemical applications, the scope for exploration of nano-scale applications is still wide open. The intimate correlation between material properties and synthesis in combination with the urgency to enhance the empirical understanding of nanomaterials demand the evolution of new strategies to promising materials. Herein we introduce a rapid pyro-synthesis that produces highly crystalline functional nanomaterials under reaction times of a few seconds in open-air conditions. The versatile technique may facilitate the development of a variety of nanomaterials and, in particular, carbon-coated metal phosphates with appreciable physico-chemical properties benefiting energy storage applications. The present strategy may present opportunities to develop “design rules” not only to produce nanomaterials for various applications but also to realize cost-effective and simple nanomaterial production beyond lab-scale limitations.

Metal–organic framework-combustion: a new, cost-effective and one-pot technique to produce a porous Co3V2O8 microsphere anode for high energy lithium ion batteries

A porous, cobalt vanadate (Co3V2O8) microsphere electrode with a cubic crystalline phase is synthesized using a novel one-pot synthesis with a metal–organic framework (MOF) based combustion strategy for use in high energy lithium ion batteries. The simple synthesis presented in this paper facilitates the evolution of a porous secondary microsphere morphology from primary aggregates of 20–50 nm particle sizes. This unique morphology appears to be derived from the Co-V–MOF intermediate network formed in situ during synthesis. The Co3V2O8 microsphere electrode displayed excellent cyclabilities at high current densities. In particular, a specific discharge capacity of 940 mA h g−1 after 100 cycles at 1 A g−1 and the highest known capacity of 650 mA h g−1 after 400 cycles at 5 A g−1 are sustained by the prepared microsphere electrode. The enhanced rate performance is mainly attributed to the unique morphology in addition to the nanoscale dimension of the electrode. Ex situ investigations confirmed that the high structural stability of the electrode facilitates minimum volume change during the electrochemical reaction under high discharge/charge rates. Furthermore, the present one-pot synthetic protocol appears to be promising for the production of phase pure, mixed metal oxide nanostructured electrodes for a wide range of applications including energy storage.

One‐Step Pyro‐Synthesis of a Nanostructured Mn3O4/C Electrode with Long Cycle Stability for Rechargeable Lithium‐Ion Batteries

A nanostructured Mn3 O4 /C electrode was prepared by a one-step polyol-assisted pyro-synthesis without any post-heat treatments. The as-prepared Mn3 O4 /C revealed nanostructured morphology comprised of secondary aggregates formed from carbon-coated primary particles of average diameters ranging between 20 and 40 nm, as evidenced from the electron microscopy studies. The N2 adsorption studies reveal a hierarchical porous feature in the nanostructured electrode. The nanostructured morphology appears to be related to the present rapid combustion strategy. The nanostructured porous Mn3 O4 /C electrode demonstrated impressive electrode properties with reversible capacities of 666 mAh g-1 at a current density of 33 mA g-1 , good capacity retentions (1141 mAh g-1 with 100 % Coulombic efficiencies at the 100th cycle), and rate capabilities (307 and 202 mAh g-1 at 528 and 1056 mA g-1 , respectively) when tested as an anode for lithium-ion battery applications.

Facile synthesis and the exploration of the zinc storage mechanism of β-MnO2 nanorods with exposed (101) planes as a novel cathode material for high performance eco-friendly zinc-ion batteries

Aqueous Zn-ion batteries (ZIBs) have emerged as promising and eco-friendly next-generation energy storage systems to substitute lithium-ion batteries. Therefore, discovering new electrode materials for ZIBs with high performance and unraveling their electrochemical reactions during Zn-ion insertion/extraction are of great interest. Here, we present, for the first time, tunnel-type β-MnO2 nanorods with exposed (101) planes, prepared via a facile microwave-assisted hydrothermal synthesis within only 10 min, for use as a high performance cathode for ZIBs. In contrast to its bulk counterpart, which showed no electrochemical reactivity, the present β-MnO2 nanorod electrode exhibited a high discharge capacity of 270 mA h g−1 at 100 mA g−1, high rate capability (123 and 86 mA h g−1 at 528 and 1056 mA g−1, respectively), and long cycling stability (75% capacity retention with 100% coulombic efficiency at 200 mA g−1) over 200 cycles. The Zn-ion storage mechanism of the cathode was also unraveled using in situ synchrotron, ex situ X-ray diffraction, ex situ X-ray photoelectron spectroscopy, and ex situ X-ray absorption spectroscopy. Our present study indicates that Zn intercalation occurred via a combination of solid solution and conversion reactions. During initial cycles, the β-MnO2 cathode was able to maintain its structure; however, after prolonged cycles, it transformed into a spinel structure. The present results challenge the common views on the β-MnO2 electrode and pave the way for the further development of ZIBs as cost-effective and environmentally friendly next-generation energy storage systems.

Facile green synthesis of a Co3V2O8 nanoparticle electrode for high energy lithium-ion battery applications

In the present study, a metal-organic framework (MOF) derived from a facile water-assisted green precipitation technique is employed to synthesize phase-pure cobalt vanadate (Co3V2O8, CVO) anode for lithium-ion battery (LIB) application. The material obtained by this eco-friendly method is systematically characterized using various techniques such as powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and N2 adsorption-desorption measurements. By using as an anode, an initial discharge capacity of 1640mAhg-1 and a reversible capacity of 1194mAhg-1 are obtained at the applied current densities after the 240th cycle (2Ag-1 for 200 cycles followed by 0.2Ag-1 for 40 cycles). Moreover, a reversible capacity as high as 962mAhg-1 is retained at high current densities even after 240 cycles (4Ag-1 for 200 cycles followed by 2Ag-1 for 40 cycles), revealing the long life stability of the electrode. Significantly, CVO anode composed of fine nanoparticles (NPs) registered a substantial rate performance and reversible specific capacities of 275, 390, 543 and 699mAhg-1 at high reversibly altered current densities of 10, 5, 2, and 1Ag-1, respectively.