Encapsulation of Fe3O4 between Copper Nanorod and Thin TiO2 Film by ALD for Lithium-Ion Capacitors

Protein-Tannin Organic Polymer-Based Oxygen-Enriched Graded Porous Carbon as a Cathode for Metal-Ion Hybrid Capacitors

Metal-ion hybrid capacitors represent an innovative class of electrochemical energy storage systems. However, hybrid capacitors made from traditional carbon-based materials struggle to simultaneously achieve both high specific capacity and long-cycle stability. A hierarchical porous carbon material with an optimized pore structure was synthesized using pig kidney proteins and tannic acid as precursors, employing cross-linking polymerization and carbonization activation strategies. The as-synthesized sample features an exceptionally high specific surface area and abundant porosity, which efficiently accommodate the adsorption and transport of solvated zinc and magnesium ions. The zinc-ion hybrid capacitor (ZHC) achieved a reversible capacity of 221 mA h g-1 at 0.2 A g-1, while the magnesium-ion hybrid capacitor (MHC) delivered 132 mA h g-1 under the same conditions. Additionally, DFT calculations revealed the critical influence of pore size on metal ion storage. In a 2 M ZnSO4 aqueous electrolyte solution, when the pore size of the carbon material was 1.13 nm, solvated zinc ions exhibited the highest adsorption energy. In contrast, in a 0.4 M (MgPhCl)2-AlCl3 organic electrolyte, a pore size of 2.29 nm optimized the storage capacity of solvated magnesium ions. This study provides important theoretical insights into designing ZHCs and MHCs.

Preparation of Manganese Oxide Nanoparticles with Enhanced Capacitive Properties Utilizing Gel Formation Method

Development of efficient and environmentally benign materials is important to satisfy the increasing demand for energy storage materials. Nanostructured transition-metal oxides are attractive because of their variety in morphology, high conductivity, and high theoretical capacitance. In this work, the nanostructured MnO₂ was successfully fabricated using a gel formation process followed by calcination at 400 °C (MNO4) and 700 °C (MNO7) in the presence of air. The suitability of the prepared materials for electrochemical capacitor application was investigated using graphite as an electrode substrate. The chemical, elemental, structural, morphological, and thermal characterizations of the materials were performed with relevant techniques. The structural and morphological analyses revealed to be a body-centered tetragonal crystal lattice with a nano-tablet-like porous surface. The capacitive performances of the MNO4- and MNO7-modified graphite electrodes were examined with cyclic voltammetry and chronopotentiometry in a 0.5 M Na₂SO₄ aqueous solution. The synthesized MNO7 demonstrated a higher specific capacitance (627.9 F g^-1), energy density (31.4 Wh kg^-1), and power density (803.5 W kg^-1) value as compared to that of MNO4. After 400 cycles, the material MNO7 preserves 100% of capacitance as its initial capacitance. The highly conductive network of nanotablet structure and porous morphologies of MNO7 are most likely responsible for its high capacitive behavior. Such material characteristics deserve a good candidate for electrode material in energy storage applications.

Recent Advances and Perspectives of Battery-Type Anode Materials for Potassium Ion Storage

Potassium ion energy storage devices are competitive candidates for grid-scale energy storage applications owing to the abundancy and cost-effectiveness of potassium (K) resources, the low standard redox potential of K/K⁺, and the high ionic conductivity in K-salt-containing electrolytes. However, the sluggish reaction dynamics and poor structural instability of battery-type anodes caused by the insertion/extraction of large K⁺ ions inhibit the full potential of K ion energy storage systems. Extensive efforts have been devoted to the exploration of promising anode materials. This Review begins with a brief introduction of the operation principles and performance indicators of typical K ion energy storage systems and significant advances in different types of battery-type anode materials, including intercalation-, mixed surface-capacitive-/intercalation-, conversion-, alloy-, mixed conversion-/alloy-, and organic-type materials. Subsequently, host-guest relationships are discussed in correlation with the electrochemical properties, underlying mechanisms, and critical issues faced by each type of anode material concerning their implementation in K ion energy storage systems. Several promising optimization strategies to improve the K⁺ storage performance are highlighted. Finally, perspectives on future trends are provided, which are aimed at accelerating the development of K ion energy storage systems.

Structural, Optical, and Electronic Properties of Cu-Doped TiNxOy Grown by Ammonothermal Atomic Layer Deposition

Copper-doped titanium oxynitride (TiN_xO_y) thin films were grown by atomic layer deposition (ALD) using the TiCl₄ precursor, NH₃, and O₂ at 420 °C. Forming gas was used to reduce the background oxygen concentration and to transfer the copper atoms in an ALD chamber prior to the growth initiation of Cu-doped TiN_xO_y. Such forming gas-mediated Cu-doping of TiN_xO_y films had a pronounced effect on their resistivity, which dropped from 484 ± 8 to 202 ± 4 μΩ cm, and also on the resistance temperature coefficient (TCR), which decreased from 1000 to 150 ppm °C^-1. We explored physical mechanisms causing this reduction by performing comparative analysis of atomic force microscopy, X-ray photoemission spectroscopy, X-ray diffraction, optical spectra, low-temperature transport, and Hall measurement data for the samples grown with and without forming gas doping. The difference in the oxygen concentration between the films did not exceed 6%. Copper segregated to the TiN_xO_y surface where its concentration reached 0.72%, but its penetration depth was less than 10 nm. Pronounced effects of the copper doping by forming gas included the TiN_xO_y film crystallite average size decrease from 57-59 to 32-34 nm, considerably finer surface granularity, electron concentration increase from 2.2(3) × 10²² to 3.5(1) × 10²² cm^-3, and the electron mobility improvement from 0.56(4) to 0.92(2) cm² V^-1 s^-1. The DC resistivity versus temperature R(T) measurements from 4.2 to 300 K showed a Cu-induced phase transition from a disordered to semimetallic state. The resistivity of Cu-doped TiN_xO_y films decreased with the temperature increase at low temperatures and reached the minimum near T = 50 K revealing signatures of the quantum interference effects similar to 2D Cu thin films, and then, semimetallic behavior was observed at higher temperatures. In TiN_xO_y films grown without forming gas, the resistivity decreased with the temperature increase as R(T) = - 1.88T^0.6 + 604 μΩ cm with no semimetallic behavior observed. The medium range resistivity and low TCR of Cu-doped TiN_xO_y make this material an attractive choice for improved matching resistors in RF analog circuits and Si complementary metal-oxide-semiconductor integrated circuits.

Atomic/molecular layer deposition for energy storage and conversion

Energy storage and conversion systems, including batteries, supercapacitors, fuel cells, solar cells, and photoelectrochemical water splitting, have played vital roles in the reduction of fossil fuel usage, addressing environmental issues and the development of electric vehicles. The fabrication and surface/interface engineering of electrode materials with refined structures are indispensable for achieving optimal performances for the different energy-related devices. Atomic layer deposition (ALD) and molecular layer deposition (MLD) techniques, the gas-phase thin film deposition processes with self-limiting and saturated surface reactions, have emerged as powerful techniques for surface and interface engineering in energy-related devices due to their exceptional capability of precise thickness control, excellent uniformity and conformity, tunable composition and relatively low deposition temperature. In the past few decades, ALD and MLD have been intensively studied for energy storage and conversion applications with remarkable progress. In this review, we give a comprehensive summary of the development and achievements of ALD and MLD and their applications for energy storage and conversion, including batteries, supercapacitors, fuel cells, solar cells, and photoelectrochemical water splitting. Moreover, the fundamental understanding of the mechanisms involved in different devices will be deeply reviewed. Furthermore, the large-scale potential of ALD and MLD techniques is discussed and predicted. Finally, we will provide insightful perspectives on future directions for new material design by ALD and MLD and untapped opportunities in energy storage and conversion.

Recent progress in sodium/potassium hybrid capacitors

Metal ion hybrid capacitors (MIHCs) have been recognized as one of the most promising power sources owing to their combined merits of high energy density in batteries and high power output in supercapacitors. The kinetics mismatch between the capacitor-type cathode and battery-type anode yet must be well addressed before implementing their practical feasibility. Here, we overview the recent progress in sodium and potassium ion hybrid capacitors (SIHCs and PIHCs) and discuss the major challenges and give an outlook on the future directions in this field. The fundamental knowledge and the history will be firstly introduced, and special emphasis is then laid on the development of a variety of electrode materials in recent years. The prospects of future research of MIHCs are finally proposed towards their practical applications. We wish that this feature article can not only educate newcomers starting their reasearch in this field, but also inspire experieced researchers to contribute to the development of high-performance MIHC devices.

Recent Advances of Magnetic Nanomaterials in Bone Tissue Repair

The magnetic field has been proven to enhance bone tissue repair by affecting cell metabolic behavior. Magnetic nanoparticles are used as biomaterials due to their unique magnetic properties and good biocompatibility. Through endocytosis, entering the cell makes it easier to affect the physiological function of the cell. Once the magnetic particles are exposed to an external magnetic field, they will be rapidly magnetized. The magnetic particles and the magnetic field work together to enhance the effectiveness of their bone tissue repair treatment. This article reviews the common synthesis methods, the mechanism, and application of magnetic nanomaterials in the field of bone tissue repair.

Al2 O3 -Assisted Confinement Synthesis of Oxide/Carbon Hollow Composite Nanofibers and Application in Metal-Ion Capacitors

Hollow micro-/nanostructures are widely explored for energy applications due to their unique structural advantages. The synthesis of hollow structures generally involves a "top-down" casting process based on hard or soft templates. Herein, a new and generic confinement strategy is developed to fabricate composite hollow fibers. A thin and homogeneous atomic-layer-deposition (ALD) Al₂ O₃ layer is employed to confine the pyrolysis of precursor fibers, which transform into metal (or metal oxide)-carbon composite hollow fibers after removal of Al₂ O₃ . Because of the uniform coating by ALD, the resultant composite hollow fibers exhibit a hollow interior from heads to ends even if they are millimeter long. V, Fe, Co, and Ni-based hollow nanofibers, demonstrating the versatility of this synthesis method, are successfully synthesized. Because of the carbon constituent, these composite fibers are particularly useful for energy applications. Herein, the as-obtained hollow V₂ O₃ -C fiber membrane is employed as a freestanding and flexible electrode for lithium-ion capacitor. The device shows an impressive energy density and a high power density.

Advanced Materials for Sodium-Ion Capacitors with Superior Energy-Power Properties: Progress and Perspectives

Developing electrochemical energy storage devices with high energy-power densities, long cycling life, as well as low cost is of great significance. Sodium-ion capacitors (NICs), with Na⁺ as carriers, are composed of a high capacity battery-type electrode and a high rate capacitive electrode. However, unlike their lithium-ion analogues, the research on NICs is still in its infancy. Rational material designs still need to be developed to meet the increasing requirements for NICs with superior energy-power performance and low cost. In the past few years, various materials have been explored to develop NICs with the merits of superior electrochemical performance, low cost, good stability, and environmental friendliness. Here, the material design strategies for sodium-ion capacitors are summarized, with focus on cathode materials, anode materials, and electrolytes. The challenges and opportunities ahead for the future research on materials for NICs are also proposed.

Atomic Pt Promoted N-Doped Carbon as Novel Negative Electrode for Li-Ion Batteries

In this work, platinum single-atom enhanced mushroom-based carbon (Pt₁/MC) materials have been facilely synthesized and served as novel electrode materials in lithium-ion batteries (LIBs). The as-synthesized Pt₁/MC active material shows a uniform dispersion of isolated Pt atoms on an MC support with high specific surface area and large total pore volume. As a negative electrode material for LIBs, the Pt₁/MC exhibits excellent electrochemical properties, which retains a capacity of 846 mA h g^-1 after 800 cycles at 2 A g^-1 and 349 mA h g^-1 (near to the theoretical capacity of graphite) after 6000 cycles at a high current density of 5 A g^-1. The remarkable high capacity and excellent cycling stability can be attributed to their porous nanostructures and atomic-Pt-enhanced lithium-ion storage. Atomic Pt can compound with Li⁺ ions to form a platinum-lithium alloy during the discharge and charge process. Density functional theory (DFT) calculations are performed to verify that the PtLi₅ alloy is the most stable intermedium on the MC substrate, which further enhances the lithiation and delithiation kinetics. This novel perspective is helpful to explore next-generation negative electrode materials with high capacities and good stabilities for LIBs.