A Binder-Free and Free-Standing Cobalt Sulfide@Carbon Nanotube Cathode Material for Aluminum-Ion Batteries.

Rechargeable aluminum-ion batteries (AIBs) are considered as a new generation of large-scale energy-storage devices due to their attractive features of abundant aluminum source, high specific capacity, and high energy density. However, AIBs suffer from a lack of suitable cathode materials with desirable capacity and long-term stability, which severely restricts the practical application of AIBs. Herein, a binder-free and self-standing cobalt sulfide encapsulated in carbon nanotubes is reported as a novel cathode material for AIBs. The resultant new electrode material exhibits not only high discharge capacity (315 mA h g-1 at 100 mA g-1 ) and enhanced rate performance (154 mA h g-1 at 1 A g-1 ), but also extraordinary cycling stability (maintains 87 mA h g-1 after 6000 cycles at 1 A g-1 ). The free-standing feature of the electrode also effectively suppresses the side reactions and material disintegrations in AIBs. The new findings reported here highlight the possibility for designing high-performance cathode materials for scalable and flexible AIBs.

Recent Progress on Integrated Energy Conversion and Storage Systems.

Over the last few decades, there has been increasing interest in the design and construction of integrated energy conversion and storage systems (IECSSs) that can simultaneously capture and store various forms of energies from nature. A large number of IECSSs have been developed with different combination of energy conversion technologies such as solar cells, mechanical generators and thermoelectric generators and energy storage devices such as rechargeable batteries and supercapacitors. This review summarizes the recent advancements to date of IECSSs based on different energy sources including solar, mechanical, thermal as well as multiple types of energies, with a special focus on the system configuration and working mechanism. With the rapid development of new energy conversion and storage technologies, innovative high performance IECSSs are of high expectation to be realised for diverse practical applications in the near future.

An Innovative Freeze-Dried Reduced Graphene Oxide Supported SnS2 Cathode Active Material for Aluminum-Ion Batteries.

Rechargeable aluminum-ion batteries (AIBs) are attractive new generation energy storage devices due to its low cost, high specific capacity, and good safety. However, the lack of suitable electrode materials with high capacity and enhanced rate performance makes it difficult for real applications. Herein, the preparation of 3D reduced graphene oxide-supported SnS2 nanosheets hybrid is reported as a new type of cathode material for AIBs. The resultant material demonstrates one of the highest capacities of 392 mAh g-1 at 100 mA g-1 and good cycling stability. It is revealed that the layered SnS2 nanosheets anchored on 3D reduced graphene oxide network endows the composite not only high electronic conductivity but also fast kinetic diffusion pathway. As a result, the hybrid material exhibits high rate performance (112 mAh g-1 at 1000 mA g-1 ). The detailed characterization also verifies the intercalation and deintercalation of relatively large chloroaluminate anions into the layered SnS2 during the charge-discharge process, which is important for better understanding of the electrochemical process of AIBs.

Tuning the Morphologies of MnO/C Hybrids by Space Constraint Assembly of Mn-MOFs for High Performance Li Ion Batteries.

Morphology controllable fabrication of electrode materials is of great significance but is still a major challenge for constructing advanced Li ion batteries. Herein, we propose a novel space constraint assembly approach to tune the morphology of Mn(terephthalic acid) (PTA)-MOF, in which benzonic acid was employed as a modulator to adjust the available MOF assembly directions. As a result, Mn(PTA)-MOFs with microquadrangulars, microflakes, and spindle-like microrods morphologies have been achieved. MnO/C hybrids with preserved morphologies were further obtained by self-sacrificial and thermal transformation of Mn(PTA)-MOFs. As anodes for Li ion batteries, these morphologies showed great influence on the electrochemical properties. Owing to the abundant porous structure and unique architecture, the MnO/C spindle-like microrods demonstrated superior electrochemical properties with a high reversible capacity of 1165 mAh g-1 at 0.3 A g-1, excellent rate capability of 580 mAh g-1 at 3 A g-1, and no considerable capacity loss after 200 cycles at 1 A g-1. This strategy could be extended to engineering the morphology of other MOF-derived functional materials in various structure-dependent applications.

Green Synthesis of Porous Three-Dimensional Nitrogen-Doped Graphene Foam for Electrochemical Applications.

A facile and green approach was developed for the production of porous three-dimensional (3D) nitrogen-doped graphene with a foam structure. In comparison with conventional methods, this green approach uses environmental precursors in the preparation of graphene products. The resulting crystalline graphene foam product exhibited a uniform structure with large surface area. These appealing features render the prepared graphene foam product a prospective backbone for producing 3D charge-transport networks. The 3D graphene foam products were employed as the skeleton with an interconnected network for lithium-ion batteries. The lithium-ion batteries with the 3D porous foam structure exhibit superior cycling stability and good rate capability. There is no capacity loss after 800 cycles because the capacity stabilized for the first few cycles, and the lithium-ion batteries with 3D graphene foam showed a discharge capacity of 180 mA h g(-1) at a current density of 1000 mA g(-1). This superior cycling stability and good rate capability was ascribed to the 3D structure with an interconnected porous network and the nitrogen-doping strategy for improved conductive properties of graphene foam, which produces an efficient 3D charge-transport network. The configuration of this 3D transport network in lithium-ion cells not only can improve the electron-transport efficiency but also can suppress the volume effect during charge/discharge cycling. Besides, nitrogen doping could enhance the formation of chemical bonding between carbon and the nearby nitrogen atoms, which could accelerate the diffusion of lithium ions through the whole graphene network.

Electrochemical and structural study of layered P2-type Na(2/3)Ni(1/3)Mn(2/3)O2 as cathode material for sodium-ion battery.

P2-type Na(2/3)Ni(1/3)Mn(2/3)O2 was synthesized by a controlled co-precipitation method followed by a high-temperature solid-state reaction and was used as a cathode material for a sodium-ion battery (SIB). The electrochemical behavior of this layered material was studied and an initial discharge capacity of 151.8 mA h g(-1) was achieved in the voltage range of 1.5-3.75 V versus Na(+)/Na. The retained discharge capacity was found to be 123.5 mA h g(-1) after charging/discharging 50 cycles, approximately 81.4% of the initial discharge capacity. In situ X-ray diffraction analysis was used to investigate the sodium insertion and extraction mechanism and clearly revealed the reversible structural changes of the P2-Na(2/3)Ni(1/3)Mn(2/3)O2 and no emergence of the O2-Ni(1/3)Mn(2/3)O2 phase during the cycling test, which is important for designing stable and high-performance SIB cathode materials.

Break-up of two-dimensional MnO2 nanosheets promotes ultrasensitive pH-triggered theranostics of cancer.

Chemically exfoliated two-dimensional MnO2 nanosheets are successfully modified with amino-polyethylene glycol as a theranostic platform for ultrasensitive stimuli-responsive theranostics of cancer. The highly dispersed MnO2 nanosheets exhibit a unique break-up in the mildly acidic microenvironment of tumor tissues, which could substantially enhance their in vitro and in vivo performances in T1 -weighted magnetic resonance imaging. Such a pH-triggered breaking-up behavior could further promote the fast release of loaded anticancer drugs for concurrent pH-responsive drug release and circumvent the multidrug resistance of cancer cells.

Dual protection of sulfur by carbon nanospheres and graphene sheets for lithium-sulfur batteries.

Well-confined elemental sulfur was implanted into a stacked block of carbon nanospheres and graphene sheets through a simple solution process to create a new type of composite cathode material for lithium-sulfur batteries. Transmission electron microscopy and elemental mapping analysis confirm that the as-prepared composite material consists of graphene-wrapped carbon nanospheres with sulfur uniformly distributed in between, where the carbon nanospheres act as the sulfur carriers. With this structural design, the graphene contributes to direct coverage of sulfur to inhibit the mobility of polysulfides, whereas the carbon nanospheres undertake the role of carrying the sulfur into the carbon network. This composite achieves a high loading of sulfur (64.2 wt %) and gives a stable electrochemical performance with a maximum discharge capacity of 1394 mAh g(-1) at a current rate of 0.1 C as well as excellent rate capability at 1 C and 2 C. The improved electrochemical properties of this composite material are attributed to the dual functions of the carbon components, which effectively restrain the sulfur inside the carbon nano-network for use in lithium-sulfur rechargeable batteries.