Jianjiang He

Nitrogen-Doped Graphdiyne Applied for Lithium-Ion Storage.

The elemental N emerged uniformly in graphdiyne (GDY) after heat treatment under NH3 atmosphere to form N-doping GDY. The interplanar N-GDY distance decreased slightly, which may be ascribed to the smaller atom radius of N than C. Compared with GDY, the introduction of N atoms in N-GDY created numerous heteroatomic defects and active sites, thus achieving enhanced electrochemical properties, including higher reversible capacity, improved rate performance, and superior cycling stability. In addition, N-doping might be advantageous to minimize the surface side reactions and form stable interfaces, hence improving the electrochemical cycling stability of N-GDY electrodes. These results indicate N-doping is also an efficient way for improving the electrochemical performance of GDY materials.

Hydrogen substituted graphdiyne as carbon-rich flexible electrode for lithium and sodium ion batteries

Organic electrodes are potential alternatives to current inorganic electrode materials for lithium ion and sodium ion batteries powering portable and wearable electronics, in terms of their mechanical flexibility, function tunability and low cost. However, the low capacity, poor rate performance and rapid capacity degradation impede their practical application. Here, we concentrate on the molecular design for improved conductivity and capacity, and favorable bulk ion transport. Through an in situ cross-coupling reaction of triethynylbenzene on copper foil, the carbon-rich frame hydrogen substituted graphdiyne film is fabricated. The organic film can act as free-standing flexible electrode for both lithium ion and sodium ion batteries, and large reversible capacities of 1050 mAh g−1 for lithium ion batteries and 650 mAh g−1 for sodium ion batteries are achieved. The electrode also shows a superior rate and cycle performances owing to the extended π-conjugated system, and the hierarchical pore bulk with large surface area.Flexible batteries have been used to power wearable smart electronics and implantable medical devices. Here, the authors report a carbon-rich flexible hydrogen substituted graphdiyne electrode exhibiting superior electrochemical performance in lithium and sodium ion batteries.

Nitrogen-Doped Porous Graphdiyne: A Highly Efficient Metal-Free Electrocatalyst for Oxygen Reduction Reaction

Metal-free catalysts for oxygen reduction reaction (ORR) are the desired materials for low-cost proton exchange membrane fuel cells. Graphdiyne (GDY), a novel type of two-dimensional carbon allotrope, is featured by its sp- and sp2-hybridized carbon atoms, different from the other existing carbon materials. Thus, nitrogen (N) can be doped in new styles by substituting sp-hybridized carbon atoms, effective for ORR, which has been displayed in this study using both experimental and theoretical technologies. The N-doped GDY was synthesized with pyridine and NH3 as N sources successively, expressing an electrocatalytic activity at a potential above 0.8 V similar to that of commercial Pt/C for ORR in alkaline solution and higher stability and better methanol tolerance than those of Pt/C.

Synthesis of Chlorine-Substituted Graphdiyne and Applications for Lithium-Ion Storage

Chlorine-substituted graphdiyne (Cl-GDY) is prepared through a Glaser-Hay coupling reaction on the copper foil. Cl-GDY is endowed with a unique π-conjugated carbon skeleton with expanded pore size in two dimensions, having graphdiyne-like sp- and sp2 - hybridized carbon atoms. As a result, the transfer tunnels for lithium (Li) ions in the perpendicular direction of the molecular plane are enlarged. Moreover, benefiting from the bottom-to-up fabrication procedure of graphdiyne and the strong chemical tailorability of the alkinyl-contained monomer, the amount of substitutional chlorine atoms with appropriate electronegativity and atom size is high and evenly distributed on the as-prepared carbon framework, which will synergistically stabilize the Li intercalated in the Cl-GDY framework, and thus generate more Li storage sites. Profiting from the above unique structure, Cl-GDY shows remarkable electrochemical properties in lithium ion half-cells.

High energy density hybrid Mg2+/Li+ battery with superior ultra-low temperature performance

The development of high energy density rechargeable Mg-based batteries operating in a wide electrochemical window and ultra-low temperature remains a great challenge owing to parasitic side reactions between electrolytes and battery components when examined at high operating potentials (above 2.0 V vs. Mg2+/Mg). Herein we propose a flexible pyrolytic graphitic film (GF) as a reliable current collector of high-voltage cathodes for a hybrid Mg2+/Li+ battery within a pouch cell configuration. The utilization of such a highly electrochemical stable GF unlocks the critical bottleneck of incompatibility among all battery parts, especially parasitic corrosive reactions between electrolytes and currently available current collectors, which takes a big step forward towards the practical applications of Mg-based batteries. With an operating potential of 2.4 V, the hybrid Mg2+/Li+ battery designed by us can deliver a maximum energy density of 382.2 W h kg(-1), which significantly surpasses that of the conventional Mg battery (about 60 W h kg(-1)), and the Al battery (about 40 W h kg(-1)) as well as the state-of-the-art hybrid Na/Mg and Li/Mg batteries. The electrochemical property of the hybrid Mg2+/Li+ battery is also characterized by higher rate capability (68.8 mA h g(-1) at 3.0C), higher coulombic efficiency of 99.5%, and better cyclic stability (98% capacity retention after 200 cycles at 1.0C). In addition, the designed hybrid battery delivers excellent electrochemical performance at an ultra-low temperature of -40 degrees C, at which it retains 77% capacity compared to that of room temperature. Our strategy opens up a new possibility for widespread applications of graphitic current collectors towards high energy rechargeable Mg-based hybrid batteries, especially applied in polar regions, aerospace, and deep offshore waters.

Porous graphdiyne applied for sodium ion storage

Sodium ion batteries have gained recognition as an intriguing candidate for next generation battery systems and large scale energy storage devices due to the natural abundance of sodium sources. In this study, we prepared bulk graphdiyne powder with a porous structure and explored its sodium storage properties. The assembled sodium ion batteries exhibited extraordinary electrochemical performance, including moderate specific capacity, long cycle life as well as excellent rate performance, which should be attributed to its unique three-dimensional porous structure, chemical stability and high electronic conductivity. We obtained a reversible capacity of 261 mA h g−1 after 300 cycles at a current density of 50 mA g−1. Even at a high current density of 100 mA g−1, the as-prepared GDY electrodes delivered a moderate specific capacity of 211 mA h g−1 after 1000 cycles, with an excellent capacity retention of 98.2%. The calculation results indicate that most intercalated Na cations stay in a large triangular hole in bulk material.

Graphene boosted Cu2GeS3 for advanced lithium-ion batteries

Germanium-based materials as the anode for lithium ion batteries (LIBs) have been investigated extensively because of their high theoretical capacities. However, ternary germanium-based sulfides as the anode material for LIBs have been rarely investigated until now. In this work, we successfully synthesized a novel ternary Cu2GeS3 (CGS) incorporated with reduced graphene oxide (CGS@RGO) and measured their lithium storage performance. As a result, the binder-free CGS@RGO anodes deliver excellent stable cycling properties and high rate capabilities. These improved properties can be ascribed to the introduction of RGO, which acts as a buffer to accommodate the large volume change and maintain the structural integrity of the electrode. More importantly, this work opens an opportunity to develop novel Ge-based anodes for high performance LIBs.

A Delicately Designed Sulfide Graphdiyne Compatible Cathode for High‐Performance Lithium/Magnesium–Sulfur Batteries

Novel sulfur cathodes hold the key to the development of metal-sulfur batteries, the promising candidate of next-generation high-energy-storage systems. Herein, a fascinating sulfur cathode based on sulfide graphdiyne (SGDY) is designed with a unique structure, which is composed of a conducting carbon skeleton with high Li+ mobility and short sulfur energy-storing unites. The SGDY cathode can essentially avoid polysulfide dissolution and be compatible with commercially available carbonate-based electrolytes and Grignard reagent-based electrolytes (all phenyl complex (APC) type electrolytes). Both the assembled Li-S and Mg-S batteries exhibit excellent electrochemical performances including large capacity, superior rate capability, high capacity retention, and high Coulombic efficiency. More importantly, this is the first implementation case of a reliable Mg-S system based on nucleophilic APC electrolytes.

Preparation of 3D Architecture Graphdiyne Nanosheets for High-Performance Sodium-Ion Batteries and Capacitors

Here, we apply three-dimensional (3D) architecture graphdiyne nanosheet (GDY-NS) as anode materials for sodium-ion storage devices achieving high energy and power performance along with excellent cyclic ability. The contribution of 3D architecture nanostructure and intramolecular pores of the GDY-NS can substantially optimize the sodium storage behavior through the accommodated intramolecular pore, 3D interconnective porous structure, and increased activity sites to facilitate a fast sodium-ion-diffusion channel. The contribution of butadiyne linkages and the formation of a stable solid electrolyte interface layer are directly confirmed through the in situ Raman measurement. The GDY-NS-based sodium-ion batteries exhibit a stable reversible capacity of approximately 812 mAh g-1 at a current density of 0.05 A g-1; they maintain more than 405 mAh g-1 over 1000 cycles at a current density of 1 A g-1. Furthermore, the sodium-ion capacitors could deliver a capacitance more than 200 F g-1 over 3000 cycles at 1 A g-1 and display an initial specific energy as high as 182.3 Wh kg-1 at a power density of 300 W kg-1 and maintain specific energy of 166 Wh kg-1 even at a power density of 15 000 W kg-1. The high energy and power density along with excellent cyclic performance based on the GDY-NS anode offers a great potential toward application on next-generation energy storage devices.

Construction of Large-Area Uniform Graphdiyne Film for High-Performance Lithium-Ion Batteries

Large-area graphdiyne film is constructed by heat treatment, including thermally induced evaporation and a cross-coupling reaction process. The growth mechanism is proposed based on the observation and characterization that the heating temperature plays an important role in the evaporation of oligomers and in triggering the thermal cross-coupling reaction, whereas the heating duration mainly determines the execution of the thermal cross-coupling reaction. By controlling the heat-treatment process, a graphdiyne film with uniform morphology and good conductivity is obtained. The improved GDY film based electrodes deliver good interfacial contact and more lithium storage sites; thus leading to superior electrochemical performance. A reversible capacity of 901 mAh g-1 is achieved. Specifically, the electrodes exhibit excellent rate performance, with which a capacity of 430 mAh g-1 is maintained at a rate as high as 5 A g-1 . These advantages mean that the uniform graphdiyne film is a good candidate for the fabrication of a flexible and high-capacity electrode material.