Hydrothermal fabrication of three-dimensional secondary battery anodes

3D Ordered Porous Nanostructure Confers Fast Charge Transfer Rate and Reduces the Electrode Polarization in Thick Electrode

Lithium batteries with high electrode thickness always possess a poor battery property due to electrode polarization along the thickness direction. Herein, a concept that the electrode polarization can be reduced through the fabrication of 3D ordered interconnected nanostructure in the electrode is put forward. A nitrogen-doped carbon photonic crystal (NCPC) with the ordered interconnected nanostructure is used in the electrode to prove the concept. NCPC can provide a fast charge transfer rate along the thickness direction and a uniform distribution for electrons and lithium ions, resulting in diminishing the concentration polarization and concentration gradient. When NCPC works for lithium-sulfur battery, the thick electrode achieves a fast charge transfer rate and a small voltage gap as well as the thin electrode. The 200 µm thick sulfur cathode obtains a specific capacity (87%) as high as 100 µm thick sulfur cathode. In contrast, the capacity ratio of the electrode made by the traditional coating method is only 45%.

Dendrite-Free and Ultra-Long-Life Lithium Metal Anode Enabled via a Three-Dimensional Ordered Porous Nanostructure

Constructing a stable non-dendritic lithium metal anode is the key to the development of high-energy batteries in the future. Herein, we fabricated nitrogen-doped carbon photonic crystals in situ in the macropores of carbon papers as a porous skeleton and confined hosts for metallic lithium. The large specific surface area of the carbon photonic crystal reduces the current density of the electrode. The three-dimensional ordered microstructure promotes uniform charge distribution and uniform lithium deposition and inhibits the volume expansion of metallic lithium. The as-prepared lithium metal anode exhibits prominent electrochemical performance with a small hysteresis of less than 95 mV beyond 180 cycles at an extremely high current density of 15 mA cm^-2. When the as-prepared lithium metal anode is coupled with the sulfur cathode, the obtained full cell displays enhanced capacitive properties and cycle life. Compared with the bare Li anode, the full cell exhibits more than 300 cycles of cell life and a 70 mA h g^-1 higher discharge capacity.

Three-Dimensional Ordered Porous Nanostructures for Lithium-Selenium Battery Cathodes That Confer Superior Energy-Storage Performance

Lithium-selenium (Li-Se) batteries suffer from the problems of polyselenides dissolution and volume expansion of active materials during the charge/discharge process. Moreover, the heavy atomic mass of selenium atoms limits the capacitive property of a Li-Se battery. Porous materials as the host for selenium particles reported by previous research studies are often disordered in pore structure and nonuniform in pore size. Herein, we report that a three-dimensional (3D) nitrogen-doped carbon photonic crystal (NCPC) with an ordered, interconnected structure was synthesized via a simple method to be the host of active materials. In addition, we prepared a Se-rich Se_1-xS_x by introducing a small amount of sulfur into a selenium ring to reduce the molecular mass but still keep the high electronic conductivity. As cathodes for a Li-Se battery, amorphous Se-rich Se_1-xS_x@NCPC composites exhibited high electrochemical performance with a specific capacity of 692 mA h g^-1 at 0.1 Ag^1-, an excellent rate capability of 526 mA h g^-1 at 3 Ag^1-, and an outstanding cycling property with an ultralow decay rate of 0.0132% per cycle at 0.6 Ag^1- over 1000 cycles. Moreover, the pouch cell of Se_1-xS_x@NCPC composites also showed a good property with an energy of 253 Wh kg^-1 at 0.1 Ag^1- and an outstanding rate energy of 192 Wh kg^-1 at 1.5 Ag^1-, manifesting great potential in practical application.

Functional inks and extrusion-based 3D printing of 2D materials: a review of current research and applications

Graphene and related 2D materials offer an ideal platform for next generation disruptive technologies and in particular the potential to produce printed electronic devices with low cost and high throughput. Interest in the use of 2D materials to create functional inks has exponentially increased in recent years with the development of new ink formulations linked with effective printing techniques, including screen, gravure, inkjet and extrusion-based printing towards low-cost device manufacturing. Exfoliated, solution-processed 2D materials formulated into inks permits additive patterning onto both rigid and conformable substrates for printed device design with high-speed, large-scale and cost-effective manufacturing. Each printing technique has some sort of clear advantages over others that requires characteristic ink formulations according to their individual operational principles. Among them, the extrusion-based 3D printing technique has attracted heightened interest due to its ability to create three-dimensional (3D) architectures with increased surface area facilitating the design of a new generation of 3D devices suitable for a wide variety of applications. There still remain several challenges in the development of 2D material ink technologies for extrusion printing which must be resolved prior to their translation into large-scale device production. This comprehensive review presents the current progress on ink formulations with 2D materials and their broad practical applications for printed energy storage devices and sensors. Finally, an outline of the challenges and outlook for extrusion-based 3D printing inks and their place in the future printed devices ecosystem is presented.

Electrodeposition Technologies for Li-Based Batteries: New Frontiers of Energy Storage

Electrodeposition induces material syntheses on conductive surfaces, distinguishing it from the widely used solid-state technologies in Li-based batteries. Electrodeposition drives uphill reactions by applying electric energy instead of heating. These features may enable electrodeposition to meet some needs for battery fabrication that conventional technologies can rarely achieve. The latest progress of electrodeposition technologies in Li-based batteries is summarized. Each component of Li-based batteries can be electrodeposited or synthesized with multiple methods. The advantages of electrodeposition are the main focus, and they are discussed in comparison with traditional technologies with the expectation to inspire innovations to build better Li-based batteries. Electrodeposition coats conformal films on surfaces and can control the film thickness, providing an effective approach to enhancing battery performance. Engineering interfaces by electrodeposition can stabilize the solid electrolyte interphase (SEI) and strengthen the adhesion of active materials to substrates, thereby prolonging the battery longevity. Lastly, a perspective of future studies on electrodepositing batteries is provided. The significant merits of electrodeposition should greatly advance the development of Li-based batteries.

Three-Dimensional-Ordered Porous Nanostructures for Lithium-Sulfur Battery Anodes and Cathodes Confer Superior Energy Storage Performance

The nonuniformity of microscopic electrochemical reaction of electrodes essentially results in the partial reaction discrepancy and subsequent partial overheating, which is the most critical safety problem of the battery system in electric vehicles. Herein, we report a class of DLPC@S/DLPC@Li full cell based on a distinctly constructed double-layer photonic crystal (DLPC) with a three-dimensional-ordered interconnected structure. This full cell not only ensures the uniformity of microscopic electrochemical reaction but also solves common problems such as low conductivity of sulfur, poor cycle life, and lithium dendrite growth. Impressively, the full cell exhibits superior electrochemical performance pertaining to high reversible capacity of 703.3 mAh g^-1 even at an extremely high rate of 10 C and excellent cycle performance with 1200 cycles with about 0.0317% capacity loss per cycle at 0.5 C.

Strategies for Building Robust Traffic Networks in Advanced Energy Storage Devices: A Focus on Composite Electrodes

The charge transport system in an energy storage device (ESD) fundamentally controls the electrochemical performance and device safety. As the skeleton of the charge transport system, the "traffic" networks connecting the active materials are primary structural factors controlling the transport of ions/electrons. However, with the development of ESDs, it becomes very critical but challenging to build traffic networks with rational structures and mechanical robustness, which can support high energy density, fast charging and discharging capability, cycle stability, safety, and even device flexibility. This is especially true for ESDs with high-capacity active materials (e.g., sulfur and silicon), which show notable volume change during cycling. Therefore, there is an urgent need for cost-effective strategies to realize robust transport networks, and an in-depth understanding of the roles of their structures and properties in device performance. To address this urgent need, the primary strategies reported recently are summarized here into three categories according to their controllability over ion-transport networks, electron-transport networks, or both of them. More specifically, the significant studies on active materials, binders, electrode designs based on various templates, pore additives, etc., are introduced accordingly. Finally, significant challenges and opportunities for building robust charge transport system in next-generation energy storage devices are discussed.

Ordered Mesoporous Tin Oxide Semiconductors with Large Pores and Crystallized Walls for High-Performance Gas Sensing

Owing to their distinct chemical and physical properties, mesoporous metal oxide semiconductors have shown great application potential in catalysis, electrochemistry, energy conversion, and energy storage. In this study, mesoporous crystalline SnO₂ materials have been synthesized through an evaporation-induced co-assembly (EICA) method using poly(ethylene oxide)-b-polystyrene diblock copolymers as the template, tin chlorides as the tin sources, and tetrahydrofuran as the solvent. By controlling conditions of the co-assembly process and employing a carbon-supported thermal treatment strategy, highly ordered mesoporous SnO₂ materials with a hexagonal mesostructure (space group P6₃/mmc) and crystalline pore walls can be obtained. The mesoporous SnO₂ is employed for fabricating gas sensor nanodevices which exhibit an excellent sensing performance toward H₂S with high sensitivity (170, 50 ppm) and superior stability, owing to its high surface area (98 m²/g), well-connected mesopores of ca. 18.0 nm, and high density of active sites in the crystalline pore walls. The chemical mechanism study reveals that both SO₂ and SnS₂ are generated during the gas sensing process on the SnO₂-based sensors.

Progress in 3D Printing of Carbon Materials for Energy-Related Applications

The additive-manufacturing (AM) technique, known as three-dimensional (3D) printing, has attracted much attention in industry and academia in recent years. 3D printing has been developed for a variety of applications. Printable inks are the most important component for 3D printing, and are related to the materials, the printing method, and the structures of the final 3D-printed products. Carbon materials, due to their good chemical stability and versatile nanostructure, have been widely used in 3D printing for different applications. Good inks are mainly based on volatile solutions having carbon materials as fillers such as graphene oxide (GO), carbon nanotubes (CNT), carbon blacks, and solvent, as well as polymers and other additives. Studies of carbon materials in 3D printing, especially GO-based materials, have been extensively reported for energy-related applications. In these circumstances, understanding the very recent developments of 3D-printed carbon materials and their extended applications to address energy-related challenges and bring new concepts for material designs are becoming urgent and important. Here, recent developments in 3D printing of emerging devices for energy-related applications are reviewed, including energy-storage applications, electronic circuits, and thermal-energy applications at high temperature. To close, a conclusion and outlook are provided, pointing out future designs and developments of 3D-printing technology based on carbon materials for energy-related applications and beyond.

High Volumetric Capacity Three-Dimensionally Sphere-Caged Secondary Battery Anodes

High volumetric energy density secondary batteries are important for many applications, which has led to considerable efforts to replace the low volumetric capacity graphite-based anode common to most Li-ion batteries with a higher energy density anode. Because most high capacity anode materials expand significantly during charging, such anodes must contain sufficient porosity in the discharged state to enable the expansion, yet not excess porosity, which lowers the overall energy density. Here, we present a high volumetric capacity anode consisting of a three-dimensional (3D) nanocomposite formed in only a few steps which includes both a 3D structured Sn scaffold and a hollow Sn sphere within each cavity where all the free Sn surfaces are coated with carbon. The anode exhibits a high volumetric capacity of ∼1700 mA h cm(-3) over 200 cycles at 0.5C, and a capacity greater than 1200 mA h cm(-3) at 10C. Importantly, the anode can even be formed into a commercially relevant ∼100 μm thick form. When assembled into a full cell the anode shows a good compatibility with a commercial LiMn2O4 cathode. In situ TEM observations confirm the electrode design accommodates the necessary volume expansion during lithiation.

Quasi-ballistic Electronic Thermal Conduction in Metal Inverse Opals

Porous metals are used in interfacial transport applications that leverage the combination of electrical and/or thermal conductivity and the large available surface area. As nanomaterials push toward smaller pore sizes to increase the total surface area and reduce diffusion length scales, electron conduction within the metal scaffold becomes suppressed due to increased surface scattering. Here we observe the transition from diffusive to quasi-ballistic thermal conduction using metal inverse opals (IOs), which are metal films that contain a periodic arrangement of interconnected spherical pores. As the material dimensions are reduced from ∼230 nm to ∼23 nm, the thermal conductivity of copper IOs is reduced by more than 57% due to the increase in surface scattering. In contrast, nickel IOs exhibit diffusive-like conduction and have a constant thermal conductivity over this size regime. The quasi-ballistic nature of electron transport at these length scales is modeled considering the inverse opal geometry, surface scattering, and grain boundaries. Understanding the characteristics of electron conduction at the nanoscale is essential to minimizing the total resistance of porous metals for interfacial transport applications, such as the total electrical resistance of battery electrodes and the total thermal resistance of microscale heat exchangers.

Solid Electrolyte Lithium Phosphous Oxynitride as a Protective Nanocladding Layer for 3D High-Capacity Conversion Electrodes

Materials that undergo conversion reactions to form different materials upon lithiation typically offer high specific capacity for energy storage applications such as Li ion batteries. However, since the reaction products often involve complex mixtures of electrically insulating and conducting particles and significant changes in volume and phase, the reversibility of conversion reactions is poor, preventing their use in rechargeable (secondary) batteries. In this paper, we fabricate and protect 3D conversion electrodes by first coating multiwalled carbon nanotubes (MWCNT) with a model conversion material, RuO2, and subsequently protecting them with conformal thin-film lithium phosphous oxynitride (LiPON), a well-known solid-state electrolyte. Atomic layer deposition is used to deposit the RuO2 and the LiPON, thus forming core double-shell MWCNT@RuO2@LiPON electrodes as a model system. We find that the LiPON protection layer enhances cyclability of the conversion electrode, which we attribute to two factors. (1) The LiPON layer provides high Li ion conductivity at the interface between the electrolyte and the electrode. (2) By constraining the electrode materials mechanically, the LiPON protection layer ensures electronic connectivity and thus conductivity during lithiation/delithiation cycles. These two mechanisms are striking in their ability to preserve capacity despite the profound changes in structure and composition intrinsic to conversion electrode materials. This LiPON-protected structure exhibits superior cycling stability and reversibility as well as decreased overpotentials compared to the unprotected core-shell structure. Furthermore, even at very low lithiation potential (0.05 V), the LiPON-protected electrode largely reduces the formation of a solid electrolyte interphase.

In-Situ Crafting of ZnFe₂O₄ Nanoparticles Impregnated within Continuous Carbon Network as Advanced Anode Materials

The ability to create a synergistic effect of nanostructure engineering and its hybridization with conductive carbonaceous material is highly desirable for attaining high-performance lithium ion batteries (LIBs). Herein, we judiciously crafted ZnFe2O4/carbon nanocomposites composed of ZnFe2O4 nanoparticles with an average size of 16 ± 5 nm encapsulated within the continuous carbon network as anode materials for LIBs. Such intriguing nanocomposites were yielded in situ via the pyrolysis-induced carbonization of polystyrene@poly(acrylic acid) (PS@PAA) core@shell nanospheres in conjunction with the formation of ZnFe2O4 nanoparticles through the thermal decomposition of ZnFe2O4 precursors incorporated within the PS@PAA nanospheres. By systematically varying the ZnFe2O4 content in the ZnFe2O4/carbon nanocomposites, the nanocomposite containing 79.3 wt % ZnFe2O4 was found to exhibit an excellent rate performance with high capacities of 1238, 1198, 1136, 1052, 926, and 521 mAh g(-1) at specific currents of 100, 200, 500, 1000, 2000, and 5000 mA g(-1), respectively. Moreover, cycling performance of the ZnFe2O4/carbon nanocomposite with 79.3 wt % ZnFe2O4 at specific currents of 200 mA g(-1) delivered an outstanding prolonged cycling stability for several hundred cycles.

2D and 3D photonic crystal materials for photocatalysis and electrochemical energy storage and conversion

This perspective reviews recent advances in inverse opal structures, how they have been developed, studied and applied as catalysts, catalyst support materials, as electrode materials for batteries, water splitting applications, solar-to-fuel conversion and electrochromics, and finally as photonic photocatalysts and photoelectrocatalysts. Throughout, we detail some of the salient optical characteristics that underpin recent results and form the basis for light-matter interactions that span electrochemical energy conversion systems as well as photocatalytic systems. Strategies for using 2D as well as 3D structures, ordered macroporous materials such as inverse opals are summarized and recent work on plasmonic-photonic coupling in metal nanoparticle-infiltrated wide band gap inverse opals for enhanced photoelectrochemistry are provided.

MoO3@Ni nanowire array hierarchical anode for high capacity and superior longevity all-metal-oxide asymmetric supercapacitors

An all-metal-oxide asymmetric supercapacitor based on MoO₃@Ni nanowire array anode with high mass loading and VO₂@NNA nanowire array cathode was constructed, which achieved a real capacity (307 mF cm⁻²) and cyclability (116.6% capacitance retention after 20 000 cycles).

High Full-Electrode Basis Capacity Template-Free 3D Nanocomposite Secondary Battery Anodes

A high full-electrode basis capacity secondary battery anode consisting of a template-free 3D nanostructured Fe3O4/C composite is presented. On a full electrode basis, the nanocomposite exhibits attractive electrochemical performance including a volumetric capacity of 1064 mAh cm(-3), which significantly exceeds both the practical (≈300 mAh cm(-3)) and theoretical (837 mAh cm(-3)) capacity of a commercial graphite-based anode.

Holographic patterning of high-performance on-chip 3D lithium-ion microbatteries

As sensors, wireless communication devices, personal health monitoring systems, and autonomous microelectromechanical systems (MEMS) become distributed and smaller, there is an increasing demand for miniaturized integrated power sources. Although thin-film batteries are well-suited for on-chip integration, their energy and power per unit area are limited. Three-dimensional electrode designs have potential to offer much greater power and energy per unit area; however, efforts to date to realize 3D microbatteries have led to prototypes with solid electrodes (and therefore low power) or mesostructured electrodes not compatible with manufacturing or on-chip integration. Here, we demonstrate an on-chip compatible method to fabricate high energy density (6.5 μWh cm(-2)⋅μm(-1)) 3D mesostructured Li-ion microbatteries based on LiMnO2 cathodes, and NiSn anodes that possess supercapacitor-like power (3,600 μW cm(-2)⋅μm(-1) peak). The mesostructured electrodes are fabricated by combining 3D holographic lithography with conventional photolithography, enabling deterministic control of both the internal electrode mesostructure and the spatial distribution of the electrodes on the substrate. The resultant full cells exhibit impressive performances, for example a conventional light-emitting diode (LED) is driven with a 500-μA peak current (600-C discharge) from a 10-μm-thick microbattery with an area of 4 mm(2) for 200 cycles with only 12% capacity fade. A combined experimental and modeling study where the structural parameters of the battery are modulated illustrates the unique design flexibility enabled by 3D holographic lithography and provides guidance for optimization for a given application.