Two-Dimensional Ga2O3/C Nanosheets as Durable and High-Rate Anode Material for Lithium Ion Batteries

Electrochemical Activation of LiGaO2: Implications for Ga-Doped Garnet Solid Electrolytes in Li-Metal Batteries

Ga-doped Li7La3Zr2O12 garnet solid electrolytes exhibit the highest Li-ion conductivities among the oxide-type garnet-structured solid electrolytes, but instabilities toward Li metal hamper their practical application. The instabilities have been assigned to direct chemical reactions between LiGaO2 coexisting phases and Li metal by several groups previously. Yet, the understanding of the role of LiGaO2 in the electrochemical cell and its electrochemical properties is still lacking. Here, we are investigating the electrochemical properties of LiGaO2 through electrochemical tests in galvanostatic cells versus Li metal and complementary ex situ studies via confocal Raman microscopy, quantitative phase analysis based on powder X-ray diffraction, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and electron energy loss spectroscopy. The results demonstrate considerable and surprising electrochemical activity, with high reversibility. A three-stage reaction mechanism is derived, including reversible electrochemical reactions that lead to the formation of highly electronically conducting products. The results have considerable implications for the use of Ga-doped Li7La3Zr2O12 electrolytes in all-solid-state Li-metal battery applications and raise the need for advanced materials engineering to realize Ga-doped Li7La3Zr2O12for practical use.

Low Barriers and Faster Electron/Ion Transport Rates through the Ga2O3/MnCO3 Anode with a Heterojunction Structure for Lithium-Ion Batteries

Electrode stability can be controlled to a large extent by constructing suitable composite structures, in which the heterojunction structure can affect the transport of electrons and ions through the effect of the interface state, changed band gap width, and the electric field at the interface. As a promising electrode material, the Ga-based material has a conversion between solid and liquid phases in the electrochemical reaction process, which endows it with self-healing properties with the structure and morphology. Based on these, the Ga2O3/MnCO3 composite was successfully synthesized with a heterogeneous structure by introducing a Ga source in the hydrothermal process. Benefitting from the acceleration effect of the internal electric field and the narrower band gap at the interface, a high-capacity Ga2O3/MnCO3 composite electrode (1112 mAh·g-1 after 225 cycles at 0.1 A·g-1 and 457.1 mAh·g-1 after 400 cycles at 1 A·g-1) can be achieved for lithium-ion batteries. The results can provide a reference for the research and preparation of electrode materials with high performance.

Multi-pixels gallium oxide UV detector array and optoelectronic applications

With the continuous advancement of deep-ultraviolet (DUV) communication and optoelectronic detection, research in this field has become a significant focal point in the scientific community. For more accurate information collection and transport, the photodetector array of many pixels is the key of the UV imaging and commnication systems, and its photoelectric performance seriously depends on semiconductor material and array layout. Gallium oxide (Ga2O3) is an emerging wide bandgap semicondutor material which has been widely used in DUV dectection. Therefore, this paper mainly focuses on Ga2O3semiconductor detector array which has gained widespread attention in the field of DUV technique, from the perspective of individual device to array and its optoelectonic integration, for reviewing and discussing the research progress in design, fabrication, and application of Ga2O3arrays in recent years. It includes the structure design and material selection of array units, units growth and array layout, response to solar blind light, the method of imaging and image recognition. Morever, the future development trend of the photodetector array has been analyzed and reflected, aiming to provide some useful suggestions for the optimizing array structure, improving patterned growth technology and material growth quality. As well as Ga2O3optoelectronic devices and their applications are discussed in view of device physics and photophysics in detector.

Fabrication of β-Ga2O3 Nanotubes via Sacrificial GaSb-Nanowire Templates

β-Ga2O3 nanostructures are attractive wide-band-gap semiconductor materials as they exhibit promising photoelectric properties and potential applications. Despite the extensive efforts on β-Ga2O3 nanowires, investigations into β-Ga2O3 nanotubes are rare since the tubular structures are hard to synthesize. In this paper, we report a facile method for fabricating β-Ga2O3 nanotubes using pre-synthesized GaSb nanowires as sacrificial templates. Through a two-step heating-treatment strategy, the GaSb nanowires are partially oxidized to form β-Ga2O3 shells, and then, the residual inner parts are removed subsequently in vacuum conditions, yielding delicate hollow β-Ga2O3 nanotubes. The length, diameter, and thickness of the nanotubes can be customized by using different GaSb nanowires and heating parameters. In situ transmission electron microscopic heating experiments are performed to reveal the transformation dynamics of the β-Ga2O3 nanotubes, while the Kirkendall effect and the sublimation process are found to be critical. Moreover, photoelectric tests are carried out on the obtained β-Ga2O3 nanotubes. A photoresponsivity of ~25.9 A/W and a detectivity of ~5.6 × 1011 Jones have been achieved with a single-β-Ga2O3-nanotube device under an excitation wavelength of 254 nm.

Influence of external electric field on electronic structure and optical properties of β-Ga2O3: a DFT study

The influence of different electric fields on the electronic structure and optical properties of β-Ga2O3 was studied by GGA+U method. The results show that appropriate electric field intensity can regulate the band gap of β-Ga2O3 more effectively to improve the photoelectric characteristics. The band gap value of intrinsic β-Ga2O3 is 4.865 eV, and decreases from 4.732 to 2.757 eV with the increase of electric field intensity from 0.05 to 0.20 eV Å-1. The length of the O-Ga bond along the electric field increases the fastest with the electric field intensity, and the distance between O and Ga reaches 2.52 Å when the electric field intensity is 0.20 eV Å-1. A new peak appears in the real and imaginary parts of the dielectric function for β-Ga2O3 in the low frequency region under the electric field, and the conductivity increases obviously. The optical absorption peaks induced by the electric field were observed in the wavelength range of 400-600 nm. The optical absorption of β-Ga2O3 is enhanced with an increase of electric field intensity, exhibiting a maximum value with the electric field of 0.15 eV Å-1. The electric field above 0.15 eV Å-1 causes a decrease of optical absorption intensity.

Self-Healable Lithium-Ion Batteries: A Review

The inner constituents of lithium-ion batteries (LIBs) are easy to deform during charging and discharging processes, and the accumulation of these deformations would result in physical fractures, poor safety performances, and short lifespan of LIBs. Recent studies indicate that the introduction of self-healing (SH) materials into electrodes or electrolytes can bring about great enhancements in their mechanical strength, thus optimizing the cycle stability of the batteries. Due to the self-healing property of these special functional materials, the fractures/cracks generated during repeated cycles could be spontaneously cured. This review systematically summarizes the mechanisms of self-healing strategies and introduces the applications of SH materials in LIBs, especially from the aspects of electrodes and electrolytes. Finally, the challenges and the opportunities of the future research as well as the potential of applications are presented to promote the research of this field.

Review of metal oxides as anode materials for lithium-ion batteries

Lithium-ion batteries with a stable circulation capacity, high energy density and good safety are widely used in automobiles, mobile phones, manufacturing and other fields. MOs due to their large theoretical capacity, simple processing and abundant reserves, and used as anode materials for LIBs, have attracted much attention. Three electrochemical mechanisms of MOs are reviewed in this paper. In addition, research progress of MOs and prospects for their further applications in LIBs are summarized.

Ga2O3–Li3VO4/NC nanofibers toward superb high-capacity and high-rate Li-ion storage

Porous Ga2O3–Li3VO4/N-doped C nanofibers consisting of ultrafine nanoparticles embedded in nanoflakes were designed and firstly prepared via electrospinning, showing superb high-rate Li-ion storage.

Several carbon-coated Ga2O3 anodes: efficient coating of reduced graphene oxide enhanced the electrochemical performance of lithium ion batteries

Gallium oxide as a novel electrode material has attracted attention because of its high stability and conductivity. In addition, Ga2O3 will be converted to Ga during the charge and discharge process, and the self-healing behavior of Ga can improve the cycling stability. In this paper, we synthesized Ga2O3 nanoparticles with a size of about 4 nm via a facile sol-gel method. Meanwhile, we employed three types of carbon materials (reduced graphene oxide, mesoporous carbon nanofiber arrays, and carbon nanotubes) to avoid the aggregation of Ga2O3 nanoparticles and improve the conductivity of Ga2O3 during the discharge/charge process as well. Among the three samples, the deactivating defective sites and special carbon matrix of reduced graphene oxide can provide more attachment points for Ga ions, so the Ga2O3 nanoparticles can be more closely and uniformly distributed on rGO. Benefitting from the perfect combination of reduced graphene oxide sheets and Ga2O3 nanoparticles, a stable capacity of the Ga2O3/rGO electrode can be maintained at 411 mA h g-1 at a current density of 1000 mA g-1 after 600 cycles. We believe that this work provides a novel and efficient way to improve the electrochemical stability of Li-ion batteries.