Rechargeable lithium-sulfur batteries.

Since the discovery of mechanically exfoliated graphene in 2004, research on ultrathin two-dimensional (2D) nanomaterials has grown exponentially in the fields of condensed matter physics, material science, chemistry, and nanotechnology. Highlighting their compelling physical, chemical, electronic, and optical properties, as well as their various potential applications, in this Review, we summarize the state-of-art progress on the ultrathin 2D nanomaterials with a particular emphasis on their recent advances. First, we introduce the unique advances on ultrathin 2D nanomaterials, followed by the description of their composition and crystal structures. The assortments of their synthetic methods are then summarized, including insights on their advantages and limitations, alongside some recommendations on suitable characterization techniques. We also discuss in detail the utilization of these ultrathin 2D nanomaterials for wide ranges of potential applications among the electronics/optoelectronics, electrocat...

Recent Advances in Ultrathin Two-Dimensional Nanomaterials

The science and technology of ultracapacitors are reviewed for a number of electrode materials, including carbon, mixed metal oxides, and conducting polymers. More work has been done using microporous carbons than with the other materials and most of the commercially available devices use carbon electrodes and an organic electrolytes. The energy density of these devices is 3¯5 Wh/kg with a power density of 300¯500 W/kg for high efficiency (90¯95%) charge/discharges. Projections of future developments using carbon indicate that energy densities of 10 Wh/kg or higher are likely with power densities of 1¯2 kW/kg. A key problem in the fabrication of these advanced devices is the bonding of the thin electrodes to a current collector such the contact resistance is less than 0.1 cm2. Special attention is given in the paper to comparing the power density characteristics of ultracapacitors and batteries. The comparisons should be made at the same charge/discharge efficiency.

Ultracapacitors: Why, How, and Where is the Technology

We developed two-step solution-phase reactions to form hybrid materials of Mn3O4 nanoparticles on reduced graphene oxide (RGO) sheets for lithium ion battery applications. Mn3O4 nanoparticles grown selectively on RGO sheets over free particle growth in solution allowed for the electrically insulating Mn3O4 nanoparticles wired up to a current collector through the underlying conducting graphene network. The Mn3O4 nanoparticles formed on RGO show a high specific capacity up to ~900mAh/g near its theoretical capacity with good rate capability and cycling stability, owing to the intimate interactions between the graphene substrates and the Mn3O4 nanoparticles grown atop. The Mn3O4/RGO hybrid could be a promising candidate material for high-capacity, low-cost, and environmentally friendly anode for lithium ion batteries. Our growth-on-graphene approach should offer a new technique for design and synthesis of battery electrodes based on highly insulating materials.

Mn3O4-Graphene Hybrid as a High Capacity Anode Material for Lithium Ion Batteries

Owing to high specific energy, low cost, and environmental friendliness, lithium–sulfur (Li–S) batteries hold great promise to meet the increasing demand for advanced energy storage beyond portable electronics, and to mitigate environmental problems. However, the application of Li–S batteries is challenged by several obstacles, including their short life and low sulfur utilization, which become more serious when sulfur loading is increased to the practically accepted level above 3–5 mg cm−2. More and more efforts have been made recently to overcome the barriers toward commercially viable Li–S batteries with a high sulfur loading. This review highlights the recent progress in high-sulfur-loading Li–S batteries enabled by hierarchical design principles at multiscale. Particularly, basic insights into the interfacial reactions, strategies for mesoscale assembly, unique architectures, and configurational innovation in the cathode, anode, and separator are under specific concerns. Hierarchy in the multiscale design is proposed to guide the future development of high-sulfur-loading Li–S batteries.

Review on High-Loading and High-Energy Lithium–Sulfur Batteries

Compressed and Crumpled Porous Carbon Electrode for High Volumetric Performance Electrical Double‐Layer Capacitors

Lithium–sulfur (Li–S) batteries are receiving intense interest because of their high theoretical energy density and low cost. However, the rapid capacity fading is a significant problem facing the application of Li–S batteries. Herein, we describe an in situ confinement strategy for preparing a porous poly(3,4-ethylenedioxythiophene)/sulfur (pPEDOT/S) composite for Li–S batteries. The as-prepared pPEDOT/S composite exhibits a monodispersed nanostructure with sizes in the range of 400–600 nm. The pPEDOT/S composite electrode exhibits excellent cycling stability and high specific capacity. At a current rate of 0.5C, the pPEDOT/S electrode exhibits a high specific capacity of 883 mA h g−1 and a capacity retention of 71% after 200 cycles. During the charge/discharge process, the porous nanostructure could facilitate rapid electrolyte diffusion and accommodate the volumetric expansion. The chemical interaction between the PEDOT and polysulfides and discharged products could efficiently avoid the dissolution of polysulfides and the irreversible deposition of discharged products. The unique nanostructure plus the excellent electrochemical performances of the composites described in the current study allow for new opportunities to design high-performance electrodes for Li–S batteries.

An in situ confinement strategy to porous poly(3,4-ethylenedioxythiophene)/sulfur composites for lithium–sulfur batteries

Metal-ion inserted vanadium oxide nanoribbons as high-performance cathodes for aqueous zinc-ion batteries

Dual‐band electrochromic smart windows with dynamic and independent control of near‐infrared (NIR) and visible (VIS) light transmittance can notably reduce the carbon footprint of buildings and improve the occupants’ visual and thermal comfort. The dual‐band response is often generated by the phase transition of crystalline electrochromic materials. However, the phase‐transition of crystalline materials is kinetically sluggish, resulting in a long response time. Herein, a fast‐switching dual‐band electrochromic smart window based on a single‐component amorphous and porous tungsten oxide (AP‐WO3) cathode without the slow phase‐transition process is demonstrated. The amorphous and porous structure of WO3 not only significantly improves the ion transport, but also provides a large surface area for Li+ adsorption that gives rise to a tunable surface plasmon resonance (SPR) in the NIR range. Consequently, the single‐component AP‐WO3 film can modulate the NIR and VIS light transmittance independently and effectively through three distinct modes with high optical modulation, fast switching speed, high bistability, and good cycling stability. The prototype dual‐band electrochromic device assembled by AP‐WO3 cathode also delivers an impressive dual‐band electrochromic performance with fast‐switching speed (6.4 s for coloration and 7.2 s for bleaching).

Bing Ding

Papers

Compressed and Crumpled Porous Carbon Electrode for High Volumetric Performance Electrical Double‐Layer Capacitors

An in situ confinement strategy to porous poly(3,4-ethylenedioxythiophene)/sulfur composites for lithium–sulfur batteries

Metal-ion inserted vanadium oxide nanoribbons as high-performance cathodes for aqueous zinc-ion batteries

Amorphous and Porous Tungsten Oxide Films for Fast‐Switching Dual‐Band Electrochromic Smart Windows

N-doped hollow carbon nanoplates with mesoporous thin shells towards high-performance supercapacitors