Xuexue Pan

Bio: Xuexue Pan is an academic researcher from South China Normal University. The author has contributed to research in topics: Electrode & Supercapacitor. The author has an hindex of 10, co-authored 18 publications receiving 293 citations.

Write-Once-Read-Many-Times and Bipolar Resistive Switching Characteristics of TiN/HfO 2 /Pt Devices Dependent on the Electroforming Polarity

Abstract: In this letter, we report the dependence of memory characteristics on electroforming polarity based on TiN/HfO2/Pt devices. Bipolar resistive switching (BRS) and write-once-read-many-times memory (WORM) behaviors were obtained after the negative and positive electroforming process, respectively. Analysis of conduction mechanisms of high resistance state confirms that BRS and WORM were dominated by Schottky emission and trap-controlled space charge limited current, respectively. These phenomena can be explained by the filamentary model with the assistance of interfacial role. Moreover, this letter also indicates that the TiN/HfO2/Pt devices have promising application in both RRAM and non-editable WORM.

Recent Advances in Two-Dimensional Nanomaterials for Supercapacitor Electrode Applications

Abstract: Supercapacitors represent a major technology to store energy for many applications including electronics, automobiles, military, and space. Despite their high power density, the energy density in supercapacitors is presently inferior to that of the state-of-the-art Li-ion batteries owing to the limited electrochemical performance exhibited by the conventional electrode materials. The advent of two-dimensional (2D) nanomaterials has spurred enormous research interest as supercapacitor electrode materials due to their fascinating electrochemical and mechanical properties. This Review discusses cutting-edge research on some of the key 2D supercapacitor electrode materials including transition metal dichalcogenides, transition metal oxides and hydroxides, MXenes, and phosphorene. Various synthetic approaches, novel electrode designs, and microstructure tuning of these 2D materials for achieving high energy and power densities are discussed.

Ultrathin‐Nanosheet‐Induced Synthesis of 3D Transition Metal Oxides Networks for Lithium Ion Battery Anodes

Abstract: A general ultrathin-nanosheet-induced strategy for producing a 3D mesoporous network of Co3O4 is reported. The fabrication process introduces a 3D N-doped carbon network to adsorb metal cobalt ions via dipping process. Then, this carbon matrix serves as the sacrificed template, whose N-doping effect and ultrathin nanosheet features play critical roles for controlling the formation of Co3O4 networks. The obtained material exhibits a 3D interconnected architecture with large specific surface area and abundant mesopores, which is constructed by nanoparticles. Merited by the optimized structure in three length scales of nanoparticles–mesopores–networks, this Co3O4 nanostructure possesses superior performance as a LIB anode: high capacity (1033 mAh g−1 at 0.1 A g−1) and long-life stability (700 cycles at 5 A g−1). Moreover, this strategy is verified to be effective for producing other transition metal oxides, including Fe2O3, ZnO, Mn3O4, NiCo2O4, and CoFe2O4.

Sandwich-like SnS2/Graphene/SnS2 with Expanded Interlayer Distance as High-Rate Lithium/Sodium-Ion Battery Anode Materials.

Abstract: SnS2 materials have attracted broad attention in the field of electrochemical energy storage due to their layered structure with high specific capacity. However, the easy restacking property during charge/discharge cycling leads to electrode structure instability and a severe capacity decrease. In this paper, we report a simple one-step hydrothermal synthesis of SnS2/graphene/SnS2 (SnS2/rGO/SnS2) composite with ultrathin SnS2 nanosheets covalently decorated on both sides of reduced graphene oxide sheets via C-S bonds. Owing to the graphene sandwiched between two SnS2 sheets, the composite presents an enlarged interlayer spacing of ∼8.03 A for SnS2, which could facilitate the insertion/extraction of Li+/Na+ ions with rapid transport kinetics as well as inhibit the restacking of SnS2 nanosheets during the charge/discharge cycling. The density functional theory calculation reveals the most stable state of the moderate interlayer spacing for the sandwich-like composite. The diffusion coefficients of Li/Na ions from both molecular simulation and experimental observation also demonstrate that this state is the most suitable for fast ion transport. In addition, numerous ultratiny SnS2 nanoparticles anchored on the graphene sheets can generate dominant pseudocapacitive contribution to the composite especially at large current density, guaranteeing its excellent high-rate performance with 844 and 765 mAh g-1 for Li/Na-ion batteries even at 10 A g-1. No distinct morphology changes occur after 200 cycles, and the SnS2 nanoparticles still recover to a pristine phase without distinct agglomeration, demonstrating that this composite with high-rate capabilities and excellent cycle stability are promising candidates for lithium/sodium storage.

Effect of cation substitution on the pseudocapacitive performance of spinel cobaltite MCo2O4 (M = Mn, Ni, Cu, and Co)

Abstract: Cation substitution is a promising strategy for modulating the structural properties and optimizing the electrochemical performance of spinel cobalt oxide (Co3O4); however, the underlying mechanism of this action induced by different cation substitutions has not yet been clearly addressed. Herein, a systematic investigation is performed to elucidate the effect of cation substitution on the pseudocapacitive performance of spinel cobaltite (MCo2O4; M = Mn, Ni, Cu, and Co) mesoporous nanowires grown on nickel foam (NF). Theoretical and experimental analyses reveal that the substitution of Co by transition metals (i.e., Mn, Ni, and Cu) in the lattice of Co3O4 can simultaneously improve charge transfer and ion diffusion, thereby exhibiting enhanced electrochemical properties. Herein, as a representative example, MnCo2O4 achieves a high specific capacitance of 2146 F g−1 at a current density of 1 A g−1, while 92.1% of its initial capacitance is retained after 5000 cycles. An asymmetric supercapacitor with MnCo2O4 as the positive material and activated carbon (AC) as the negative material delivers a high energy density of 56.1 W h kg−1 at a power density of 800 W kg−1, and a favorable energy density of 29.3 W h kg−1 at a power density as high as 8000 W kg−1.