Zhichang Pan

In-situ Growth of Layered Bimetallic ZnCo Hydroxide Nanosheets for High-Performance All-Solid-State Pseudocapacitor

Two-dimensional (2D) hydroxide nanosheets can exhibit exceptional electrochemical performance owing to their shortened ion diffusion distances, abundant active sites, and various valence states. Herein, we report ZnCo1.5(OH)4.5Cl0.5·0.45H2O nanosheets (thickness ∼30 nm) which crystallize in a layered structure and exhibit a high specific capacitance of 3946.5 F g-1 at 3 A g-1 for an electrochemical pseudocapacitor. ZnCo1.5(OH)4.5Cl0.5·0.45H2O was synthesized by a homogeneous precipitation method and spontaneously crystallized into 2D nanosheets in well-defined hexagonal morphology with crystal structure revealed by synchrotron X-ray powder diffraction data analysis. In situ growth of ZnCo1.5(OH)4.5Cl0.5·0.45H2O nanosheet arrays on conductive Ni foam substrate was successfully realized. Asymmetric supercapacitors based on ZnCo1.5(OH)4.5Cl0.5·0.45H2O nanosheets @Ni foam// PVA, KOH//reduced graphene oxide exhibits a high energy density of 114.8 Wh kg-1 at an average power density of 643.8 W kg-1, which surpasses most of the reported all-solid-state supercapacitors based on carbonaceous materials, transition metal oxides/hydroxides, and MXenes. Furthermore, a supercapacitor constructed from ZnCo1.5(OH)4.5Cl0.5·0.45H2O nanosheets@PET substrate shows excellent flexibility and mechanical stability. This study provides layered bimetallic hydroxide nanosheets as promising electroactive materials for flexible, solid-state energy storage devices, presenting the best reported performance to date.

Charge Transfer in Ultrafine LDH Nanosheets/Graphene Interface with Superior Capacitive Energy Storage Performance

Two-dimensional LDH nanosheets recently have generated considerable interest in various promising applications because of their intriguing properties. Herein, we report a facile in situ nucleation strategy toward in situ decorating monodispersed Ni-Fe LDH ultrafine nanosheets (UNs) on graphene oxide template based on the precise control and manipulation of LDH UNs anchored, nucleated, grown, and crystallized. Anion-exchange behavior was observed in this Ni-Fe LDH UNs@rGO composite. The Ni-Fe LDH UNs@rGO electrodes displayed a significantly enhanced specific capacitance (2715F g-1 at 3 A g-1) and energy density (82.3 Wh kg-1 at 661 W kg-1), which exceeds the energy densities of most previously reported nickel iron oxide/hydroxides. Moreover, the asymmetric supercapacitor, with the Ni-Fe LDH UNs @rGO composite as the positive electrode material and reduced graphene oxide (rGO) as the negative electrode material, exhibited a high energy density (120 Wh kg -1) at an average power density of 1.3 kW kg -1. A charge transfer from LDH layer to graphene layer, which means a built in electric field directed from LDH to graphene can be established by DFT calculations, which can significantly accelerate reaction kinetics and effectively optimize the capacitive energy storage performance.

Rapid Amorphization in Metastable CoSeO3·H2O Nanosheets for Ultrafast Lithiation Kinetics

The realization of high-performance anode materials with high capacity at fast lithiation kinetics and excellent cycle stability remains a significant but critical challenge for high-power applications such as electric vehicles. Two-dimensional nanostructures have attracted considerable research interest in electrochemical energy storage devices owing to their intriguing surface effect and significantly decreased ion-diffusion pathway. Here we describe rationally designed metastable CoSeO3·H2O nanosheets synthesized by a facile hydrothermal method for use as a Li ion battery anode. This crystalline nanosheet can be steadily converted into amorphous phase at the beginning of the first Li+ discharge cycling, leading to ultrahigh reversible capacities of 1100 and 515 mAh g-1 after 1000 cycles at a high rate of 3 and 10 A g-1, respectively. The as-obtained amorphous structure experiences an isotropic stress, which can significantly reduce the risk of fracture during electrochemical cycling. Our study offers a precious opportunity to reveal the ultrafast lithiation kinetics associated with the rapid amorphization mechanism in layered cobalt selenide nanosheets.

CuGaS2 nanoplates: a robust and self-healing anode for Li/Na ion batteries in a wide temperature range of 268–318 K

The practical application of batteries in electric vehicles (EVs) and hybrid electric vehicles (HEVs) is hindered by the narrow operating temperature range due to the degradation of the solid–electrolyte interface (SEI) layer at high temperature and poor ion/electron diffusion kinetics at low temperature. Herein, we firstly report CuGaS2 hexagonal nanoplates as a novel and robust anode material working in a wide temperature range. CuGaS2 nanoplates with a lateral size of 2–3 μm and thickness of 180–200 nm have been successfully synthesized by a vapor thermal transformation from the oxide counterpart CuGaO2. The thermal workability of the as-synthesized CuGaS2 benefits from a synergistic effect including the high conductivity of copper and the self-healing nature of liquid metal gallium. Room temperature CuGaS2 as a lithium ion battery anode electrode exhibits a high reversible capacity over 521 mA h g−1 after 600 cycles at a high current density of 5 A g−1. Furthermore, as the temperature is lifted to 318 K, the CuGaS2 electrode exhibits a stable and reversible capacity over 784 mA h g−1 at a high current density of 0.5 A g−1; even at the low temperature of 268 K, a reversible capacity over 407 mA h g−1 can be realized, which is much superior to that of the commercial graphite anode.

In situ growth of (NH4)2V10O25·8H2O urchin-like hierarchical arrays as superior electrodes for all-solid-state supercapacitors

Hierarchical nanostructures with highly exposed active surfaces for use in high-performance pseudocapacitors have attracted considerable attention. Herein, we developed a one-step method for the in situ growth of (NH4)2V10O25·8H2O urchin-like hierarchical structures on highly conductive nickel foam substrates for use as advanced electrodes for all-solid-state asymmetric supercapacitors. The in situ growth of (NH4)2V10O25·8H2O urchin-like hierarchical structures delivers a specific capacitance of 1530 F g−1 at a current density of 1.5 A g−1, and retains 95.1% of the initial capacitance after 10 000 cycles, owing to the advantages of the urchin-like hierarchical structure such as more active sites for electrochemical reactions, as well as a shortened diffusion length for the charge carriers due to a binder-free effect, which exceeds that of most recently reported vanadates and polyvanadates. The as-assembled all-solid-state (NH4)2V10O25·8H2O@Ni//PVA/KOH//RGO@Ni device exhibits a comparable capacity of 92.2 F g−1 at a current density of 0.4 A g−1 and excellent cycling performance through 5000 cycles. Our study provides rational guidance toward the design of novel hierarchical nanostructures of polyvanadate for solid-state supercapacitors with superior electrochemical performances in long-term cycling stability and high energy density.