3D Anode Research Articles

Novel Silicon Nanowires-Based 3D Anodes for High-Capacity Lithium Ion Batteries

Here, we report on the scalable synthesis and characterization of novel architecture three-dimensional high-capacity amorphous SiNWs-based anodes, with focus on studying their electrochemical degradation mechanisms. We achieved an unprecedented combination of remarkable performance characteristics, high loadings of 3-15 mAh/cm2, a very low irreversible capacity (10% for the 3-4 mAh/cm2 anodes), current efficiency greater than 99.5%, cycle stability both in half cells and a LiFePO4 battery, a total capacity of 457mAh/cm2 over 204 cycles and fast charge–discharge rates (up to 2.7C at 20mA/cm2). These SiNWs-based binder-free 3D anodes have been cycled for over 200 cycles, exhibiting a stable cycle life. Notably, it was found that the growth of the continuous SEI layer thickness, and its concomitant increase in resistivity, represents the major reason for the observed capacity loss of the SiNWs-based anodes. Importantly, these SiNWs-based anodes of novel architecture meet the requirements of lithium batteries for future portable, and electric-vehicle, applications.

Fabrication of Ag-Deposited Silicon Nanoparticles for a Lithium Ion Battery Anode Prepared By Alkaline Immersion Plating

INTRODUCTION Lithium ion batteries (LIBs) with greater energy density are required for use in energy-demanding applications such as electric cars and electronic devices. Silicon is an attractive candidate anode material for use in LIBs due to its high theoretical capacity (4200 mAh/g) compared to carbon (372 mAh/g) currently used in commercially available lithium ion batteries. The commercial use of Si-based powders in anodes remains hindered by the low electrical conductivity of silicon and its huge volume change during lithiation and delithiation. Many studies have been conducted to alleviate the pulverization of silicon during the charge/discharge process and to increase the conductivity of silicon materials. Recently, several approaches for synthesizing 3D porous Si-based anode materials that exhibit good cycling characteristics have been developed. Several approaches employ a wet-chemical etching process using hydrofluoric acid (HF) and silver nitrate (AgNO3). The fabrication process consists of two steps. First, Ag is deposited on silicon nanoparticles using HF and AgNO3. Subsequently, the particles are immersed into HF and hydrogen peroxide (H2O2), resulting in the generation of 3D porous silicon nanoparticles. However, HF is a dangerous chemical and thus a process not requiring HF for the fabrication of Ag-deposited silicon particles is required.1,2,3) Herein, we present Ag-deposited silicon nanoparticles fabricated using an alkaline method and describe their charge/discharge properties as a LIB anode material. EXPERIMENTAL We used planetary ball milling silicon nanoparticles. An immersion plating bath containing 2 g/L Si, 0.005 M AgNO3 and 0.010 M EDTA-2Na was prepared, and KOH was then added to adjust to pH 9~12. The silicon nanoparticles were dispersed using ultrasonic irradiation for 30 min. The reaction was conducted in a water bath to maintain the temperature at 25, 30 40, 50, 60, 70, 80°C, respectively for 2 hours. The silicon nanoparticles were then collected on a filter by suction filtration and dried in vacuum at 110 °C for 2 hours. The microstructures of the samples were observed using field-emission scanning electron microscopy (FE-SEM) and scanning-transmission electron microscopy (STEM). Charge-discharge cycle tests of the prepared samples were performed. A coin cell (Model CR2032) was used as the test cell and lithium metal foil was used as the counter electrode. The cut-off potentials for the charge/discharge processes were 0.02 V and 1.5 V (vs. Li/Li+). RESULTS AND DISCUSSION Ag-deposited silicon nanoparticles were fabricated using an alkaline immersion plating method in the absence of HF. REFERENCES 1) Jung-In Lee, Soojin Park Nano Energy (2013) 2, 146-152 2) Satoshi Uchida, Megumi Mihashi, Masaki Yamagata, Masashi Ishikawa, Journal of Power Sources 273 (2015) 118-122 3) Chunli Li, Ping Zhang, Zhiyu Jiang Electrochemica Acta 161 (2015) 408-412 Figure 1

Tissue-like Silicon Nanowires-Based Three-Dimensional Anodes for High-Capacity Lithium Ion Batteries.

Here, we report on the scalable synthesis and characterization of novel architecture three-dimensional (3D) high-capacity amorphous silicon nanowires (SiNWs)-based anodes with focus on studying their electrochemical degradation mechanisms. We achieved an unprecedented combination of remarkable performance characteristics, high loadings of 3-15 mAh/cm(2), a very low irreversible capacity (10% for the 3-4 mAh/cm(2) anodes), current efficiency greater than 99.5%, cycle stability (both in half cells and a LiFePO4 battery), a total capacity of 457 mAh/cm(2) over 204 cycles and fast charge-discharge rates (up to 2.7C at 20 mA/cm(2)). These SiNWs-based binder-free 3D anodes have been cycled for over 200 cycles, exhibiting a stable cycle life. Notably, it was found that the growth of the continuous SEI layer thickness, and its concomitant increase in resistivity, represents the major reason for the observed capacity loss of the SiNWs-based anodes. Importantly, these NWs-based anodes of novel architecture meet the requirements of lithium batteries for future portable, and electric-vehicle, applications.

Carbonized textile with free-standing threads as an efficient anode material for bioelectrochemical systems

Efficiency of bioelectrochemical systems (BESs) is generally limited by the performance of bioanode, resulted from the nature of microbial electron transfer and the character of the anode substrate. In the present study, a 3D structured anode material is fabricated using a towel as precursor through high-temperature carbonization. The 3D electrode is resulted from freely standing threads, twisted by fibers with diameter at micrometer scale, on a woven textile substrate. The open structure provides easy accesses for microbial to attach on the fiber surface. Furthermore, the prepared materials possess a high capacitive character which is beneficial for electron storage and contributes to the performance of bioanode. When tested in BESs, the prepared material achieves a current density of 0.80 ± 0.06 mA cm−2, larger than conventional anodes, e.g. graphite felt (0.55 ± 0.01 mA cm−2), carbon cloth (0.06 ± 0.01 mA cm−2), and carbon mesh (0.02 ± 0.00 mA cm−2). The present study provides a novel 3D anode substrate that can effectively promote the performance of BESs.

On the effects of assembly compression on the performance of liquid-feed DMFCs under methanol-limiting conditions: A 2D numerical study

The influence of assembly compression on the performance of liquid-feed DMFCs under methanol-limiting conditions is explored by means of a 2D/1D multiphysics across-the-channel model. The numerical formulation incorporates a comprehensive 2D description of the anode GDL, including two-phase phenomena, non-uniform anisotropic transport properties, and electrical contact resistances at the GDL/BPP interface. GDL effective properties are evaluated using empirical data corresponding to Toray® carbon paper. A simplified but physically sound 1D description, locally coupled to the 2D anode GDL model, is adopted to describe transport processes in the MPLs, membrane and cathode GDL, whereas the catalyst layers are treated as infinitely thin surfaces. Good agreement is found between the numerical results and previous experimental data. The interplay between assembly compression, bipolar plate material, and channel configuration is also investigated. The results show that there is an optimum GDL compression ratio in terms of overall power density, the optimal compression level being strongly dependent on bipolar plate material. Beyond the optimum, the detrimental effect of compression is larger in non-parallel flow fields due to the additional reduction of methanol transported by under-rib convection. The results suggest that, under certain conditions, this transport mechanism could be more important than diffusion in the anode of liquid-feed DMFCs.

Cu/(Cu(OH)2-CuO) core/shell nanorods array: in-situ growth and application as an efficient 3D oxygen evolution anode

In this paper, we develop a novel strategy toward the in-situ growth of core/shell nanorods array consisting of Cu(OH)2-CuO nanosheets as the shell and Cu as the core on Cu foil [Cu/(Cu(OH)2-CuO) NA/CF]. As an integrated 3D non-noble-metal oxygen evolution anode, the Cu/(Cu(OH)2-CuO) NA/CF shows high catalytic activity with an onset overpotential of 350mV and a Tafel slope of 76mV/dec. It needs an overpotential of 417mV to drive current density of 10mA/cm2 and maintains its catalytic activity for at least 22h. The attractive performances make it promising candidate as a future high-performance catalyst for applications.

High-performance sodium ion batteries based on a 3D anode from nitrogen-doped graphene foams.

A 3D N-doped graphene foam with a 6.8 at% nitrogen content is prepared by annealing a freeze-dried graphene oxide foam in ammonia. It is used as an anode in sodium ion batteries to deliver a high initial reversible capacity of 852.6 mA h g(-1) at 1 C between 0.02 and 3 V with a long-term retention of 69.7% after 150 cycles.

Robust α-Fe2O3nanorod arrays with optimized interstices as high-performance 3D anodes for high-rate lithium ion batteries

Self-supported α-Fe2O3 nanorod arrays consisting of mesocrystalline nanorod bundles with tunable interstices were prepared by solution-phase growth coupled with chemical etching. The existence of acetic acid and sulfate ions in the hydrothermal system promoted the direct growth of α-Fe2O3 nanorod bundles with a mesocrystalline structure on a Ti substrate. The robust α-Fe2O3 nanorod arrays with optimized interstices are able to offer reduced lengths for electron transport and ion diffusion, and enough spaces to accommodate lithiation-induced volume expansion, leading to novel three-dimensional (3D) anodes with significantly improved rate capability and cyclability. When used as binder-free anodes for lithium ion batteries (LIBs), the α-Fe2O3 nanorod arrays retained a reversible capacity of 801 mA h g−1 after 500 cycles at 5 C (namely, 5 A g−1), and achieved practically valuable capacities of 499 mA h g−1 and 350 mA h g−1 at high rates of 20 C and 30 C, respectively. Furthermore, a flexible full battery with high capacity and fast charging capability was assembled using the α-Fe2O3 nanorod arrays as the anode, demonstrating their potential applications in flexible electronic devices.

In situ growth of nickel selenide nanowire arrays on nickel foil for methanol electro-oxidation in alkaline media

NiSe nanowire arrays solvothermally grown on nickel foil behave as an efficient 3D anode for electro-catalytic oxidation of methanol in alkaline media with strong durability.

Metal-catalyst-free carbohydrazide fuel cells with three-dimensional graphene anodes.

As a potential solution to concerns on sustainable energy, the wide spread commercialization of fuel cell has long been hindered by limited reserves and relatively high costs of metal catalysts. 3D graphene, a carbon-only catalyst prepared by reduction of carbon monoxide with lithium oxide, is found to electrochemically catalyze carbohydrazide oxidation reaction efficiently. A prototype of a completely metal-catalyst-free anion exchange membrane fuel cell (AEMFC) with a 3D graphene anode catalyst and an N-doped CNT (N-CNT) cathode catalyst generate a peak power density of 24.9 mW cm(-2) . The average number of electrons electrochemically extracted from one carbohydrazide molecule is 4.9, indicating the existence of CN bond activation, which is a key factor contributing to high fuel utilization efficiency.

Enhanced electrooxidation of urea using NiMoO4·xH2O nanosheet arrays on Ni foam as anode

Urea electrolysis has shown great potential in hydrogen production and remediation of urea-containing wastewater and it is highly important to develop efficient urea oxidation electrocatalysts made from earth-abundant elements. Here we report the growth of NiMoO4·xH2O nanosheet arrays on Ni foam (NiMoO4 NAs/NF) through a hydrothermal process. When directly used as a 3D catalytic anode for electrooxidation of urea in alkaline solutions, the NiMoO4 NAs/NF exhibits high catalytic activity and stability. It achieves specific current density of 830mAcm−2mg−1 at 0.5V at a scan rate of 10mV s−1, about 4.2 times enhancement compared to Ni(OH)2 NAs/NF.

Aligned TiO2 nanotube/nanoparticle heterostructures with enhanced electrochemical performance as three-dimensional anode for lithium-ion microbatteries

A novel TiO2 three-dimensional (3D) anode with an aligned TiO2 nanotube/nanoparticle heterostructure (TiO2 NTs/NPs) is developed by simply immersing as-anodized TiO2 NTs into water and further crystallizing the TiO2 NTs by post-annealing. The heterostructure, with its core in a tubular morphology and with both the outer and inner surface consisting of nanoparticles, is confirmed by FESEM and TEM. A reversible areal capacity of 0.126 mAh · cm−2 is retained after 50 cycles for the TiO2 NTs/NPs heterostructure electrode, which is higher than that of the TiO2 NTs electrode (0.102 mAh · cm−2 after 50 cycles). At the current densities of 0.02, 0.04, 0.06, 0.08, 0.10 and 0.20 mA · cm−2, the areal capacities are 0.142, 0.127, 0.117, 0.110, 0.104 and 0.089 mAh · cm−2, respectively, for the TiO2 NTs/NPs heterostructure electrode compared to the areal capacities of 0.123, 0.112, 0.105, 0.101, 0.094 and 0.083 mAh · cm−2, respectively, for the the TiO2 NTs electrode. The enhanced electrochemical performance is attributed to the unique microstructure of the TiO2 NTs/NPs heterostructure electrode with the TiO2 NT core used as a straight pathway for electronic transport and with TiO2 NP offering enhanced surface areas for facile Li+ insertion/extraction. The results described here inspire a facile approach to fabricate a 3D anode with an enhanced electrochemical performance for lithium-ion microbattery applications.

High-capacity carbon-coated titanium dioxide core–shell nanoparticles modified three dimensional anodes for improved energy output in microbial fuel cells

Three-dimensional (3D) electrodes have been intensively investigated as alternatives to conventional plate electrodes in the development of high-performance microbial fuel cells (MFCs). However, the energy output of the MFCs with the 3D anodes is still limited for practical applications. In this study, a 3D anode modified with a nano-structured capacitive layer is prepared to improve the performance of an microbial fuel cell (MFC). The capacitive layer composes of titanium dioxide (TiO2) and egg white protein (EWP)-derived carbon assembled core–shell nanoparticles, which are integrated into loofah sponge carbon (LSC) to obtain a high-capacitive 3D electrode. The as-prepared 3D anode produces a power density of 2.59 ± 0.12 W m−2, which is 63% and 201% higher than that of the original LSC and graphite anodes, respectively. The increased energy output is contributed to the enhanced electrochemical capacitance of the 3D anodes as well as the synergetic effects between TiO2 and EWP-derived carbon due to their unique properties, such as relatively high surface area, good biocompatibility, and favorable surface functionalization for interfacial microbial electron transfer. The results obtained in this study will benefit the optimized design of new 3D materials to achieve enhanced performance in MFCs.

Hematite nanorods array on carbon cloth as an efficient 3D oxygen evolution anode

In this communication, hematite nanorods array is developed on carbon cloth (α-Fe2O3 NA/CC) as a novel anode for oxygen evolution reaction in alkaline electrolytes. This integrated 3D electrode exhibits an onset overpotential of 330mV and a Tafel slope of 52mV dec−1 and its catalytic activity is superior over preformed α-Fe2O3 nanorods immobilized on CC using a polymer binder. Furthermore, this electrode affords current density of 10mAcm−2 at an overpotential of 420mV and is capable of maintaining its catalytic activity for at least 10h.

3D Imaging and in-operando Tracking of Battery Electrode Microstructures

Global demands for energy storage, supply and portability has seen continual increase. Meeting these requirements will be accelerated through an ability to directly image electrochemical devices such as batteries, in 3D, at high resolutions. However, despite their importance, the influence of microstructure on electrode behaviour remains poorly understood. Tomographic techniques allow for direct 3D imaging and chracterisation of complex microstructures down towards tens of nanometers; which are inadequately described in 2D. The performance of battery electrodes are dependent on their inherent nano/micro scale structures where important reactions occur. Microstructural differences in mechanical, electrochemical or transport behaviour at fine length scales ultimately influences cell and pack level performance. Additionally, during processing or operation microstructural evolution may degrade electrochemical performance. Here we utilise tomographic techniques to probe different 3D battery anode structures at high resolutions to capture micro-nanometer length scale structure. The advanced 3D quantification of complex electrode shapes, structures and morphology facilitate an understanding of cell level behaviour. Furthermore, we directly image and track in-operando interfacial and microstructural changes during anode lithiation (Figure 1). In doing so, this provides important insights for electrode design and understanding sources of performance degradation.

3D Nanostructured Binder Free Electrodes for Novel Energy Storage Devices

Energy-storage technologies, including supercapacitors with high power density and rechargeable batteries with high energy density, have attracted significant attention for applications in electric vehicles, power line conditioners, and load leveling of solar energy and wind power. However, for such applications, the demand for both high power density and energy density devices is becoming increasingly important. Thus, novel hybrid energy storage devices combining the advantages of supercapacitors and batteries is becoming a hotstopic in the energy storage research field. In previous work, the 3D nanostructured binder free electrodes have been shown to deliver high discharge capacity and excellent rate capability, which were assessed using Li-ion half cells [1-4], indicating that energy storage devices with high energy and power density may be achieved using such kinds of 3D electrodes. In this work, novel Li-ion full cells and supercapacitors were designed and fabricated using MnOx-based 3D electrodes, a manganese oxides based Li-ion full cell is shown in Figure 1a-c. The electrochemical performances of the different energy storage devices were assessed using a 3-electrode cell, as shown in Figure 1 d-f. The maximum energy density of the manganese oxides based Li-ion full cell is 223 Wh/kg at 146 W/kg. The Sn and Si based 3D anodes were also prepared and assessed using both Li-ion half cells and Li-ion full cells. Figure 1 (a)Figure 1 (b)Figure 1 (c)Figure 1 (d)Figure 1 (e) Figure 1: (a) Scheme of the manganese oxides based Li-ion full cell. S(T)EM images of the nanostructured LiMn2O4 cathode material (b) and the 3D C/MnOy/ACNTs anode materials (c). Two- and three-electrode charge (d) and discharge (e) voltage profiles of the manganese oxides based Li-ion full cell utilizing Li metal reference.

Experimental advances and preliminary mathematical modeling of the Swiss-roll mixed-reactant direct borohydride fuel cell

The Swiss-roll single-cell mixed reactant (SR-MRFC) borohydride – oxygen fuel cell equipped with Pt/carbon cloth 3D anode and either MnO2 or Ag gas-diffusion cathodes is investigated by a combination of experimental studies and preliminary mathematical modeling of the polarization curve. We investigate the effects of four variables: cathode side metallic mesh fluid distributor, separator type (Nafion 112® vs. Viledon®), cathode catalyst (MnO2 vs. Ag), and the hydrophilic pore volume fraction of the gas-diffusion cathode. Using a two-phase feed of alkaline borohydride solution (1 M NaBH4 – 2 M NaOH) and O2 gas in an SR-MRFC equipped with Pt/C 3D anode, MnO2 gas diffusion cathode, Viledon® porous diaphragm, expanded mesh cathode-side fluid distributor, the maximum superficial power density is 2230 W m−2 at 323 K and 105 kPa(abs). The latter superficial power density is almost 3.5 times higher than our previously reported superficial power density for the same catalyst combinations. Furthermore, with a Pt anode and Ag cathode catalyst combination, a superficial power density of 2500 W m−2 is achieved with superior performance durability compared to the MnO2 cathode. The fuel cell results are substantiated by impedance spectroscopy analysis and preliminary mathematical model predictions based on mixed potential theory.

Vertically Aligned CNT‐Supported Thick Ge Films as High‐Performance 3D Anodes for Lithium Ion Batteries

The electrochemical performance of a thick Ge film (ca. 1020 nm) is dramatically improved by adopting vertically aligned carbon nanotube (VACNT) arrays as a 3D current collector. The VACNT-supported thick Ge film exhibits high reversible specific capacity (1352 mAh g(-1) ), and excellent capacity retention (97.2% after 100 cycles) and rate capability (843 mAh g(-1) at 10 C).

Geobacter Sulfurreducens Biofilm Growth Kinetics on High Surface Area, Flow-through Anodes Under Ion-Transport Limitations

Anode-respiring bacteria like Geobacter sulfurreducens have been used to generate electrical current in many different bioelectrochemical systems, including microbial fuel cells and microbial electrolysis cells. Various cell designs have led to increases in the current densities of these systems when normalized to the projected surface area of the anodes by using 3D architecture and various convection mechanisms, with the result being an increase in current density by around five-fold. However, this increase does not nearly match the increase in available surface area. We hypothesized that the surface area is in excess in these systems, and that the current density is probably limited by ion-transport. To investigate this hypothesis, we designed a flow-through, 3D anode bioelectrochemical reactor to investigate the effect of the ion-transport limitation on the growth kinetics of G. sulfurreducens. Using our three-electrode bioelectrochemical reactor system, we ran experiments to test how the current production, acetate utilization, hydrogen production, and biomass production were affected by changing Nernst-Planck variables, including ion transport and electrode spacing. In our system, we found that ion transport can become limiting after a 3D electrode is sufficiently colonized by Geobacter sulfurreducens, and that beyond this point the growth kinetics are no longer defined by the Nernst-Monod equation. Under these conditions, we found that the maximum current is controlled by mass transport of acetate when advection is absent, and by the mass transport of ions when advection is present. We also found that on a graphite felt electrode, in a system where ion transport is limiting (i.e., when addition of salt or convection increases the current), the acetate consumption and growth kinetics of Geobacter sulfurreducens are arithmetic, with the respective rates controllable using the variables in the Nernst-Planck equation. In this arithmetic growth regime, the acetate consumption rate, hydrogen productivity and the growth rate were decoupled from instantaneous biomass, and instead coupled solely to the steady-state current. Though arithmetic growth patterns in bacteria and algae have been described historically when the cells are under certain conditions, this the first time that an arithmetic growth regime of a microorganism has been demonstrated to be caused by ion transport in an electrochemical system, and should add to our understanding of the growth kinetics of anode-respiring biofilms. The presentation will discuss the implications of our results for future reactor designs.

Quasi-perpetual discharge behaviour in p-type Ge–air batteries

Metal-air batteries continue to become attractive energy storage and conversion systems due to their high energy and power densities, safer chemistries, and economic viability. Semiconductor-air batteries - a term we first define here as metal-air batteries that use semiconductor anodes such as silicon (Si) and germanium (Ge) - have been introduced in recent years as new high-energy battery chemistries. In this paper, we describe the excellent doping-dependent discharge kinetics of p-type Ge anodes in a semiconductor-air cell employing a gelled KOH electrolyte. Owing to its Fermi level, n-type Ge is expected to have lower redox potential and better electronic conductivity, which could potentially lead to a higher operating voltage and better discharge kinetics. Nonetheless, discharge measurements demonstrated that this prediction is only valid at the low current regime and breaks down at the high current density region. The p-type Ge behaves extremely better at elevated currents, evident from the higher voltage, more power available, and larger practical energy density from a very long discharge time, possibly arising from the high overpotential for surface passivation. A primary semiconductor-air battery, powered by a flat p-type Ge as a multi-electron anode, exhibited an unprecedented full discharge capacity of 1302.5 mA h gGe(-1) (88% anode utilization efficiency), the highest among semiconductor-air cells, notably better than new metal-air cells with three-dimensional and nanostructured anodes, and at least two folds higher than commercial Zn-air and Al-air cells. We therefore suggest that this study be extended to doped-Si anodes, in order to pave the way for a deeper understanding on the discharge phenomena in alkaline metal-air conversion cells with semiconductor anodes for specific niche applications in the future.