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

Energy density is the main property of rechargeable batteries that has driven the entire technology forward in past decades. Lithium-ion batteries (LIBs) now surpass other, previously competitive battery types (for example, lead–acid and nickel metal hydride) but still require extensive further improvement to, in particular, extend the operation hours of mobile IT devices and the driving mileages of all-electric vehicles. In this Review, we present a critical overview of a wide range of post-LIB materials and systems that could have a pivotal role in meeting such demands. We divide battery systems into two categories: near-term and long-term technologies. To provide a realistic and balanced perspective, we describe the operating principles and remaining issues of each post-LIB technology, and also evaluate these materials under commercial cell configurations. Post-lithium-ion batteries are reviewed with a focus on their operating principles, advantages and the challenges that they face. The volumetric energy density of each battery is examined using a commercial pouch-cell configuration to evaluate its practical significance and identify appropriate research directions.

Promise and reality of post-lithium-ion batteries with high energy densities

Energy-storage technologies, including electrical double-layer capacitors and rechargeable batteries, have attracted significant attention for applications in portable electronic devices, electric vehicles, bulk electricity storage at power stations, and “load leveling” of renewable sources, such as solar energy and wind power. Transforming lithium batteries and electric double-layer capacitors requires a step change in the science underpinning these devices, including the discovery of new materials, new electrochemistry, and an increased understanding of the processes on which the devices depend. The Review will consider some of the current scientific issues underpinning lithium batteries and electric double-layer capacitors.

Challenges Facing Lithium Batteries and Electrical Double‐Layer Capacitors

Nano- and bulk-silicon-based insertion anodes for lithium-ion secondary cells

Review on recent progress of nanostructured anode materials for Li-ion batteries

A π-conjugated nanosheet comprising planar nickel bis(dithiolene) complexes was synthesized by a bottom-up method. A liquid–liquid interfacial reaction using benzenehexathiol in the organic phase and nickel(II) acetate in the aqueous phase produced a semiconducting bulk material with a thickness of several micrometers. Powder X-ray diffraction analysis revealed that the crystalline portion of the bulk material comprised a staggered stack of nanosheets. A single-layer nanosheet was successfully realized using a gas–liquid interfacial reaction. Atomic force microscopy and scanning tunneling microscopy confirmed that the π-conjugated nanosheet was single-layered. Modulation of the oxidation state of the nanosheet was possible using chemical redox reactions.

π-Conjugated Nickel Bis(dithiolene) Complex Nanosheet

The chemical structure of SiO (silicon monoxide) anodes has been analyzed using X-ray photoelectron spectroscopy (XPS). Vapor deposition was used to form SiO anodes on Cu film. XPS analysis was performed on anodes at eachof three stages: after deposition, after initial charge, and after discharge. The results of this analysis were then evaluated in terms of the anode's respective electrochemical characteristics. It has been found that some Si remains oxidized in the full charge state and that lithium silicates are formed. The lithium silicates serve as a buffer with respect to changes in anode volume.

Analysis of SiO Anodes for Lithium-Ion Batteries

We have used a codeposition technique to develop high-capacity metal-doped SiO anodes for use in Li-ion rechargeable batteries, and we have measured their electrochemical properties. Cycle maintenance rates were roughly 82% after 400 cycles with a manganese oxide cathode. Initial charge-discharge coulombic efficiencies were roughly 84% without Li addition and nearly 100% with Li addition to the anodes for their full performance using Li half-cells. The discharge capacities per unit weight of these anodes were about 3-4 times that of graphite. X-ray photoelectron spectroscopy analysis shows that the anodes have a different chemical structure from that of nondoped SiO anodes [J. Electrochem. Soc., 152, A2089 (2005)], that metal compounds are not formed in the doped metals, and that the valence of Si changed from 0 to 4+, and back to 0, during initial charge and discharge. Doped-metal works as an electron transporter, helping diffusion of Li ions in the electrode, and improves the electrical properties of the material.

https://iopscience.iop.org/article/10.1149/1.2455963/pdf

Electrochemical Properties and Chemical Structures of Metal-Doped SiO Anodes for Li-Ion Rechargeable Batteries

A negative electrode for a secondary cell which comprises a negative electrode collector (1a) and, formed thereon in the following order, a first layer comprising carbon as a primary component (a carbon layer 2a) and a second layer comprising particles having a theoretical capacity greater than that of graphite (a Li occluding layer 3a), wherein the second layer also comprises an another element having a theoretical capacity not greater than that of graphite. The above particles having a theoretical capacity greater than that of graphite allows the achievement of an improved capacity and an elevated operation voltage, and the another element allows the suppression of the expansion and shrinkage of the electrode associated with charge and discharge of the cell, which results in the suppression of the deterioration of the capacity of the cell due to the repeat of charge and discharge.

Negative electrode for secondary cell and secondary cell using the same

https://www.rsc.org/suppdata/CC/b9/b926841c/b926841c.pdf

Mariko Miyachi

Papers

π-Conjugated Nickel Bis(dithiolene) Complex Nanosheet

Analysis of SiO Anodes for Lithium-Ion Batteries

Electrochemical Properties and Chemical Structures of Metal-Doped SiO Anodes for Li-Ion Rechargeable Batteries

Negative electrode for secondary cell and secondary cell using the same

A photosensing system composed of photosystem I, molecular wire, gold nanoparticle, and double surfactants in water.