Xiongwu Zhong

Amorphous Red Phosphorus Embedded in Highly Ordered Mesoporous Carbon with Superior Lithium and Sodium Storage Capacity

Red phosphorus (P) have been considered as one of the most promising anode material for both lithium-ion batteries (LIBs) and (NIBs), because of its high theoretical capacity. However, natural insulating property and the large volume expansion of red P during cycling lead to poor cyclability and low rate performance, which prevents its practical application. Here, we significantly improves both lithium storage and sodium storage performance of red P by confining nanosized amorphous red P into the mesoporous carbon matrix (P@CMK-3) using a vaporization-condensation-conversion process. The P@CMK-3 shows a high reversible specific capacity of ∼ 2250 mA h g(-1) based on the mass of red P at 0.25 C (∼ 971 mA h g(-1) based on the composite), excellent rate performance of 1598 and 624 mA h g(-1) based on the mass of red P at 6.1 and 12 C, respectively (562 and 228 mA h g(-1) based on the mass of the composite at 6.1 and 12 C, respectively) and significantly enhanced cycle life of 1150 mA h g(-1) based on the mass of red P at 5 C (500 mA h g(-1) based on the mass of the composite) after 1000 cycles for LIBs. For Na ions, it also displays a reversible capacity of 1020 mA h g(-1) based on the mass of red P (370 mA h g(-1) based on the mass of the composite) after 210 cycles at 5C. The significantly improved electrochemical performance could be attributed to the unique structure that combines a variety of advantages: easy access of electrolyte to the open channel structure, short transport path of ions through carbon toward the red P, and high ionic and electronic conductivity.

Carbon‐Coated Germanium Nanowires on Carbon Nanofibers as Self‐Supported Electrodes for Flexible Lithium‐Ion Batteries

A hybrid structure with carbon-coated germanium nanowires grown on the surface of carbon nanofibers is fabricated using an in situ vapor-liquid-solid process. It is used as a self-supported and flexible anode for Li-ion batteries.

General Strategy for Fabricating Sandwich-like Graphene-Based Hybrid Films for Highly Reversible Lithium Storage.

We report a general strategy for the fabrication of freestanding sandwich-like graphene-based hybrid films by electrostatic adsorption and following reduction reaction. We demonstrate that by rational control of pH value in precursors, graphene oxide (GO) sheets can form three-dimensional (3D) sandwich frameworks with nanoparticles decorated between the layers of graphene. In our proof-of-concept study, we prepared the graphene/Si/graphene (G@Si@G) sandwich-like films. When used as negative electrode materials for lithium-ion batteries, it exhibits superior lithium-ion storage performance (∼1800 mA h g(-1) after 40 cycles at 100 mA g(-1)). Importantly, with this simple and general method, we also successfully synthesized graphene/Fe2O3/graphene and graphene/TiO2/graphene hybrid films, showing improved electrochemical performance. The good electrochemical property results from the enhanced electron transport rate, and the 3D flexible matrix to buffer volume changes during cycling. In addition, the porous sandwich structure consisting of plate-like graphene with high surface area provides effective electrolyte infiltration and promotes diffusion rate of Li(+), leading to an improved rate capability.

Phosphorus-doped porous carbon derived from rice husk as anode for lithium ion batteries

We developed a simple and scalable chemical method to obtain phosphorus-doped porous carbon (P-PC–RH) by optimized acid treatment and thermal annealing of rice husk with triphenylphosphine (TPP). After doping with phosphorus (doping level of ∼4.14 at% P), the P-PC–RH electrode increases by almost half the reversible capacity (757 mA h g−1 after 100 cycles at 100 mA g−1) of porous carbon without phosphorus doping (PC–RH-x, x = 2, 4, 6). When cycled at a high current of 2000 mA g−1, it still delivers a reversible specific capacity of 382 mA h g−1. The improved electrochemical performance of P-PC–RH is attributed to the synergetic effect of the 3D interconnected porous structure and phosphorus doping, which can maintain perfect electrical conductivity throughout the electrode and enhance electrochemical activities for lithium storage.

Facile synthesis of germanium–reduced graphene oxide composite as anode for high performance lithium-ion batteries

Germanium is a promising anode material for lithium ion batteries (LIBs) due to its high specific capacity, but it still suffers from poor cyclability. A simple method was developed to synthesize Ge–reduced graphene oxide nanocomposites using organic germanium as a precursor. The nanocomposites exhibit improved electrochemical performance with a reversible specific capacity of 814 mA h g−1 after 50 cycles at a current density of 0.1 A g−1. When cycled at a high current density of 2 A g−1, they still deliver a reversible specific capacity of 690 mA h g−1 after 150 cycles. The improved electrochemical performance is attributed to the unique nanostructure (0D electroactive particles in 2D mixed conducting matrix), which conferred a variety of advantages: high flexibility of the graphene sheets for accommodating the volume change, good electrochemical coupling and short transport length for ions and electrons, enabling low contact resistances.

Germanium encapsulated in sulfur and nitrogen co-doped 3D porous carbon as an ultra-long-cycle life anode for lithium ion batteries

Germanium (Ge) has been considered as a promising anode material for Li-ion batteries because of its theoretical capacity (1600 mA h g−1). However, its poor electrochemical performances resulting from the large volume variation during Li–Ge alloy/dealloy processes prevent its practical application. Herein, we designed a 3D core/shell structure by encapsulation of Ge in a sulfur (S) and nitrogen (N) co-doped three-dimensionally (3D) interconnected macroporous carbon matrix (denoted as Ge@S,N-3DPC). The 3D porous structure can not only buffer the volume change during alloy/dealloy processes, but also facilitate the electrolyte to soak in, offering fast ion/electron pathways. Whats more, the co-doping of S and N in carbon could introduce more defects and active sites, which can also help to improve the interfacial adsorption and electrochemical behaviors. When used as an anode material for LIBs, the Ge@S,N-3DPC shows excellent electrochemical performances (1000 mA h g−1 at 200 mA g−1), outstanding cycling stability (94% capacity retention after 300 cycles) and high rate capability (358 mA h g−1 at 10 A g−1). This work develops a general strategy to improve the electrochemical performance of these alloy-type electrode materials with huge volume change in the energy storage area.

2D sandwich-like nanosheets of ultrafine Sb nanoparticles anchored to graphene for high-efficiency sodium storage

Sb is considered a promising anode material for high-performance sodium-ion batteries (NIBs) owing to its high theoretical specific capacity (660 mAh·g−1). However, Sb shows a very large volume change (∼200%) during sodiation and desodiation, leading to poor electrochemical performance. Here, we designed and tested a sandwich-like graphene-supported Sb nanocomposite (denoted Sb@RGO@Sb), in which ultrafine Sb nanoparticles are uniformly anchored on a reduced graphene oxide (RGO) surface. The ultrafine Sb nanocrystals anchored on the RGO surface minimize the aggregation of Sb and inhibit restacking of the RGO sheets, leading to a minimum transport length for both ions and electrons. The graphene layer not only accommodates the large volume variation of Sb during cycling but also promotes the electron conductivity of the whole electrode. Owing to its unique structure, this sandwich-like composite exhibits superior sodium storage properties.

Amorphous Red Phosphorus Embedded in Sandwiched Porous Carbon Enabling Superior Sodium Storage Performances

The red P anode for sodium ion batteries has attracted great attention recently due to the high theoretical capacity, but the poor intrinsic electronic conductivity and large volume expansion restrain its widespread applications. Herein, the red P is successfully encapsulated into the cube shaped sandwich-like interconnected porous carbon building (denoted as P@C-GO/MOF-5) via the vaporization-condensation method. Superior cycling stability (high capacity retention of about 93% at 2 A g-1 after 100 cycles) and excellent rate performance (502 mAh g-1 at 10 A g-1 ) can be obtained for the P@C-GO/MOF-5 electrode. The superior electrochemical performance can be ascribed to the successful incorporation of red P into the unique carbon matrix with large surface area and pore volume, interconnected porous structure, excellent electronic conductivity and superior structural stability.

Carbon and Carbon Hybrid Materials as Anodes for Sodium-Ion Batteries

Sodium-ion batteries (SIBs) have attracted much attention for application in large-scale grid energy storage owing to the abundance and low cost of sodium sources. However, low energy density and poor cycling life hinder practical application of SIBs. Recently, substantial efforts have been made to develop electrode materials to push forward large-scale practical applications. Carbon materials can be directly used as anode materials, and they show excellent sodium storage performance. Additionally, designing and constructing carbon hybrid materials is an effective strategy to obtain high-performance anodes for SIBs. In this review, we summarize recent research progress on carbon and carbon hybrid materials as anodes for SIBs. Nanostructural design to enhance the sodium storage performance of anode materials is discussed, and we offer some insight into the potential directions of and future high-performance anode materials for SIBs.

Boosting the Electrochemical Performance of Li-S Batteries with a Dual Polysulfides Confinement Strategy

Lithium-sulfur (Li-S) batteries have attracted more and more attention because they represent one of the most promising candidates to satisfy emerging energy storage demands. The biggest challenge regarding the application of the Li-S battery is to suppress the polysulfide shuttle while maintaining a high sulfur loading mass. Here, a dual polysulfide confinement strategy is designed by confinement of sulfur in polydopamine-coated MXene nanosheets (denoted as S@Mxe@PDA) that performs as a high-performance cathode for Li-S cells owing to their inherently high underlying metallic conductivity and chemical bonding and strong chemical adsorption to lithium polysulfides (LPs). This dual LPs confinement strategy is supported by the results of density functional theory calculations. It is demonstrated that the S@Mxe@PDA cathode exhibits outstanding electrochemical properties, including high reversible capacity (1044 mAh g-1 after 150 cycles at 0.2 C), superior rate capability (624 mAh g-1 at 6 C) and excellent cycling stability (556 mAh g-1 after 330 cycles at 0.5 C with 4.4 mg cm-2 sulfur loading). This work offers a facile and effective method for boosting Li-S batteries into practical applications.