Lin-Lin Zhang

Shale-like Co3O4 for high performance lithium/sodium ion batteries

In recent years, metal-organic compounds have been considered as ideal sacrificial templates to obtain transition metal oxides for electrochemical applications due to their diverse structures and tunable properties. In this work, a new kind of cobalt-based metal organic compound with a layered structure was designed and prepared, which was then transformed into ultrafine cobalt oxide (Co3O4) nanocrystallites via a facile annealing treatment. The obtained Co3O4 nanocrystallites further assembled into a hierarchical shale-like structure, donating extremely short ion diffusion pathway and rich porosity to the materials. The special structure largely alleviated the problems of Co3O4 such as inferior intrinsic electrical conductivity, poor ion transport kinetics and large volume changes during the redox reactions. When evaluated as anode materials for lithium-ion batteries, the shale-like Co3O4 (S-Co3O4) exhibited superior lithium storage properties with a high capacity of 1045.3 mA h g−1 after 100 cycles at 200 mA g−1 and good rate capabilities up to 10 A g−1. Moreover, the S-Co3O4 showed decent electrochemical performance in sodium-ion batteries due to the above-mentioned comprehensive merits (380 and 153.8 mA h g−1 at 50 and 5000 mA g−1, respectively).

A vertical and cross-linked Ni(OH)2 network on cellulose-fiber covered with graphene as a binder-free electrode for advanced asymmetric supercapacitors

Nanostructured transition metal oxides are attractive pseudocapacitive materials with high theoretical specific capacitance, scale-up potential and environmental benignity. However, realizing high capacitance and excellent rate capability remains a critical challenge. Herein, a three-dimensional carbon support of cellulose-fiber covered with graphene (CFG) to induce the growth of a hierarchical nanostructured Ni(OH)2 (Ni(OH)2–CFG) is fabricated through a one-pot hydrothermal reaction without using any surfactants or hard templates. The resulting Ni(OH)2–CFG composite exhibits a special vertical and cross-linked network structure with a large surface area (425.9 m2 g−1, higher than that of unsupported Ni(OH)2, 366.9 m2 g−1) and appropriate pore size distribution of micro–mesopores, which offer fast electrolyte ion-transport and short ion-diffusion pathways. Electrochemical characterization demonstrates that the Ni(OH)2–CFG composite as a binder-free electrode reveals high mass capacitance (2276 F g−1, at 1 A g−1), good rate capability and excellent cycling stability (no capacitance decay after 1000 cycles at a high current density of 5 A g−1). In addition, an asymmetric Ni(OH)2–CFG//activated carbon supercapacitor exhibits a high cell-voltage of 1.6 V and a maximum specific capacitance of 191.3 F g−1 with an energy density up to 15.0 W h kg−1. The excellent performances of the Ni(OH)2–CFG composite demonstrate its promising potential for future capacitor based energy storage and conversion.

Nanoscale Polysulfides Reactors Achieved by Chemical Au–S Interaction: Improving the Performance of Li–S Batteries on the Electrode Level

In this work, the chemical interaction of cathode and lithium polysulfides (LiPSs), which is a more targeted approach for completely preventing the shuttle of LiPSs in lithium-sulfur (Li-S) batteries, has been established on the electrode level. Through simply posttreating the ordinary sulfur cathode in atmospheric environment just for several minutes, the Au nanoparticles (Au NPs) were well-decorated on/in the surface and pores of the electrode composed of commercial acetylene black (CB) and sulfur powder. The Au NPs can covalently stabilize the sulfur/LiPSs, which is advantageous for restricting the shuttle effect. Moreover, the LiPSs reservoirs of Au NPs with high conductivity can significantly control the deposition of the trapped LiPSs, contributing to the uniform distribution of sulfur species upon charging/discharging. The slight modification of the cathode with <3 wt % Au NPs has favorably prospered the cycle capacity and stability of Li-S batteries. Moreover, this cathode exhibited an excellent anti-self-discharge ability. The slight decoration for the ordinary electrode, which can be easily accessed in the industrial process, provides a facile strategy for improving the performance of commercial carbon-based Li-S batteries toward practical application.

A novel approach to prepare Si/C nanocomposites with yolk-shell structures for lithium ion batteries

A novel method was developed to successfully prepare mesoporous Si/C nanocomposites with yolk–shell structures (MSi@C). Different from the reported methods, this approach was unique, straightforward and easily scaled up. A plausible mechanism for the formation of MSi@C nanocomposites was proposed, which was in accordance with the results of transmission electron microscopy (TEM). When the mixture of mesoporous Si (M-Si) and citric acid was heated up, the volume of air adsorbed by the M-Si expanded, and the viscoelastic citric acid layers inflated just like balloons, directly leading to the formation of the yolk–shell structured MSi@C nanocomposites during the carbonization. The MSi@C nanocomposites possessed an M-Si core with diameter ∼150 nm and a carbon shell with diameter ∼230 nm. Such nano and mesoporous structure combined with voids between the M-Si core and carbon shell not only provides enough space for the volume expansion of M-Si during lithiation, but also accommodates the mechanical stresses/strains caused by the volume inflation and contraction. Moreover, partial graphitization of the carbon contributed to the improved electrical conductivity and rate performance of MSi@C. As a result, the prepared MSi@C exhibited an initial reversible capacity of 2599.1 mA h g−1 and maintained 1264.7 mA h g−1 even after 150 cycles at 100 mA g−1, with high coulombic efficiency (CE) above 99% (based on the weight of M-Si in the electrode). Therefore, this work provided an alternative method to fabricate yolk–shell nanostructured materials with great potential as anode materials for lithium ion batteries.

A Novel Layered Sedimentary Rocks Structure of the Oxygen-Enriched Carbon for Ultrahigh-Rate-Performance Supercapacitors

In this paper, gelatin as a natural biomass was selected to successfully prepare an oxygen-enriched carbon with layered sedimentary rocks structure, which exhibited ultrahigh-rate performance and excellent cycling stability as supercapacitors. The specific capacitance reached 272.6 F g(-1) at 1 A g(-1) and still retained 197.0 F g(-1) even at 100 A g(-1) (with high capacitance retention of 72.3%). The outstanding electrochemical performance resulted from the special layered structure with large surface area (827.8 m(2) g(-1)) and high content of oxygen (16.215 wt %), which effectively realized the synergistic effects of the electrical double-layer capacitance and pseudocapacitance. Moreover, it delivered an energy density of 25.3 Wh kg(-1) even with a high power density of 34.7 kW kg(-1) and ultralong cycling stability (with no capacitance decay even over 10,000 cycles at 2 A g(-1)) in a symmetric supercapacitor, which are highly desirable for their practical application in energy storage devices and conversion.

Flexible paper electrodes constructed from Zn2GeO4 nanofibers anchored with amorphous carbon for advanced lithium ion batteries

A dissolution–recrystallization method was developed to prepare flexible paper electrodes constructed of Zn2GeO4 nanofibers anchored with amorphous carbon (ZGO/C-P) for high energy and power Li-ion batteries. The ZGO/C-P exhibits superior long-term cycle stability (up to 2000 cycles at 1 A g−1) and excellent rate capability.

A plum-pudding like mesoporous SiO2/flake graphite nanocomposite with superior rate performance for LIB anode materials.

A novel kind of plum-pudding like mesoporous SiO2 nanospheres (MSNs) and flake graphite (FG) nanocomposite (pp-MSNs/FG) was designed and fabricated via a facile and cost-effective hydrothermal method. Transmission electron microscopy (TEM) analysis showed that most of the MSNs were well anchored on FG. This special architecture has multiple advantages, including FG that offers a conductive framework and hinders the volume expansion effect. Moreover, the porous structure of MSNs could provide more available lithium storage sites and extra free space to accommodate the mechanical strain caused by the volume change during the repeated reversible reaction between Li(+) and active materials. Due to the synergetic effects of its unique plum-pudding structure, the obtained pp-MSNs/FG nanocomposite exhibited a decent reversible capacity of 702 mA h g(-1) (based on the weight of MSNs in the electrode material) after 100 cycles with high Coulombic efficiency above 99% under 100 mA g(-1) and a charge capacity of 239.6 mA h g(-1) could be obtained even under 5000 mA g(-1). Their high rate performance is among the best-reported performances of SiO2-based anode materials.

Porous Carbon with Willow-Leaf-Shaped Pores for High-Performance Supercapacitors

A novel kind of biomass-derived, high-oxygen-containing carbon material doped with nitrogen that has willow-leaf-shaped pores was synthesized. The obtained carbon material has an exotic hierarchical pore structure composed of bowl-shaped macropores, willow-leaf-shaped pores, and an abundance of micropores. This unique hierarchical porous structure provides an effective combination of high current densities and high capacitance because of a pseudocapacitive component that is afforded by the introduction of nitrogen and oxygen dopants. Our synthetic optimization allows further improvements in the performance of this hierarchical porous carbon (HPC) material by providing a high degree of control over the graphitization degree, specific surface area, and pore volume. As a result, a large specific surface area (1093 m2 g-1) and pore volume (0.8379 cm3 g-1) are obtained for HPC-650, which affords fast ion transport because of its short ion-diffusion pathways. HPC-650 exhibits a high specific capacitance of 312 F g-1 at 1 A g-1, retaining 76.5% of its capacitance at 20 A g-1. Moreover, it delivers an energy density of 50.2 W h kg-1 at a power density of 1.19 kW kg-1, which is sufficient to power a yellow-light-emitting diode and operate a commercial scientific calculator.