Huiping Du

Nickel Disulfide–Graphene Nanosheets Composites with Improved Electrochemical Performance for Sodium Ion Battery

Nickel disulfide-graphene nanosheets (NiS2-GNS) composites were successfully synthesized via a simple and mild hydrothermal method. It was revealed by scanning electron microscopy and transmission electron microscopy images that the spherical NiS2 nanoparticles with a diameter of 200-300 nm were uniformly dispersed on graphene nanosheets. Na(+) electrochemical storage properties including cycling performance and high-rate capability of NiS2-GNS composites were investigated, demonstrating a superior reversible capacity of 407 mAh g(-1) with the capacity retention of 77% over 200 cycles at a current density of 0.1 C. Furthermore, even at a large current density of 2 C, a high capacity of 168 mAh g(-1) can still remain, which is much higher than that of pristine NiS2 materials. The enhancement in electrochemical properties might be attributed to the synergetic effect endowed by high conductivity of graphene and novel structure of the electrode material. Combined with the advantages of low cost and environmental benignity, NiS2-GNS composite would be a potential anode material for sodium ion batteries.

Ultrafast Alkaline Ni/Zn Battery Based on Ni-Foam-Supported Ni3S2 Nanosheets

Self-supported Ni3S2 ultrathin nanosheets were in situ formed by direct sulfurization of commercially available nickel foam using thioacetamide as sulfur source under hydrothermal process. The morphology and structure of the as-obtained sample were analyzed by using XRD, XPS, SEM, and TEM, revealing that an ultrathin nanosheets Ni3S2 were grown on the surface of Ni form. The as-obtained Ni3S2/Ni composite with uniform architecture was used as cathode material for alkaline Ni/Zn battery, which delivered high capacity of 125 mAh g(-1) after 100 cycles with no obvious capacity fading, extraordinary rate capability (68 mAh g(-1) at the current density of 5.0 A g(-1)), and high operating voltage (1.75 V).

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.

A high-voltage poly(methylethyl α-cyanoacrylate) composite polymer electrolyte for 5 V lithium batteries

High-voltage lithium batteries have attracted increasing attention for large scale energy storage application in electric vehicles, smart grids and other electronic devices. However, a major bottleneck to achieve high-voltage lithium batteries is the anodic voltage stability of electrolytes. Herein, we fabricate a composite polymer electrolyte, comprised of poly(methylethyl α-cyanoacrylate), nonwoven polytetrafluoroethylene and lithium bis(oxalate)borate salt. The composite polymer electrolyte presents a wide electrochemical window, which is explored to address the above-mentioned bottleneck. It is demonstrated that such a composite polymer electrolyte exhibits a higher ionic conductivity (1.24 mS cm−1 at 25 °C), better dimensional thermal resistance (150 °C) and higher ion transference number (0.63) compared to those of commercially available liquid electrolytes with a polypropylene separator. In addition, LiNi0.5Mn1.5O4/Li batteries employing such a composite polymer electrolyte deliver excellent cycling performance and outstanding rate capability. So, it is demonstrated that the poly(methylethyl α-cyanoacrylate) based polymer electrolyte appears to be a promising candidate of high-voltage lithium battery electrolyte towards next generation high energy density batteries.

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.

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.

Facile and Reliable in Situ Polymerization of Poly(Ethyl Cyanoacrylate)-Based Polymer Electrolytes toward Flexible Lithium Batteries

Polycyanoacrylate is a very promising matrix for polymer electrolyte, which possesses advantages of strong binding and high electrochemical stability owing to the functional nitrile groups. Herein, a facile and reliable in situ polymerization strategy of poly(ethyl cyanoacrylate) (PECA) based gel polymer electrolytes (GPE) via a high efficient anionic polymerization was introduced consisting of PECA and 4 M LiClO4 in carbonate solvents. The in situ polymerized PECA gel polymer electrolyte achieved an excellent ionic conductivity (2.7 × 10-3 S cm-1) at room temperature, and exhibited a considerable electrochemical stability window up to 4.8 V vs Li/Li+. The LiFePO4/PECA-GPE/Li and LiNi1.5Mn0.5O4/PECA-GPE/Li batteries using this in-situ-polymerized GPE delivered stable charge/discharge profiles, considerable rate capability, and excellent cycling performance. These results demonstrated this reliable in situ polymerization process is a very promising strategy to prepare high performance polymer electrolytes for flexible thin-film batteries, micropower lithium batteries, and deformable lithium batteries for special purpose.

Li–O2 Cell with LiI(3-hydroxypropionitrile)2 as a Redox Mediator: Insight into the Working Mechanism of I– during Charge in Anhydrous Systems

Redox mediators (RMs) have been widely applied to reduce the charge overpotential of nonaqueous lithium-oxygen (Li-O2) batteries. Among the reported RMs, LiI is under hot debate with lots of controversial reports. However, there is a limited understanding of the charge mechanism of I- in anhydrous Li-O2 batteries. Here, we study the chemical reactivity between the oxidized state of I- and Li2O2. We confirm that the Li2O2 particles could be chemically oxidized by I2 rather than I3- species. Furthermore, our work demonstrates that the generated I- from Li2O2 oxidation would combine with I2 to give I3- species, hindering further oxidation of Li2O2 by I2. To improve the working efficiency of I- RMs, we introduce a compound LiI(3-hydroxypropionitrile)2 (LiI(HPN)2) with a high binding ability of I-. Compared with LiI, the cell that contained LiI(HPN)2 shows a significantly increased amount of I2 species during charge and enhanced Li2O2 oxidation efficiency under the same working conditions.

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.