Improved Cyclability of Lithium-Ion Batteries Using Pyroprotein-Assisted Silicon Anodes

With a 10-fold higher theoretical capacity than that of graphite, silicon has excellent potential for use as an active anode material in lithium-ion (Li-ion) batteries, especially when high capacity and high energy density are required. In this study, we improved the lifetime characteristics of silicon nanoparticles (SINPs) by synthesizing a Si/C composite anode composed of carbonized fibroin (pyroprotein) and SINPs. The pyroprotein matrix effectively accommodates the volume expansion of the SINPs during charging and discharging, thereby suppressing the formation of surface defects on the electrode. This pyroprotein matrix also provides additional storage sites for Li-ion chemisorption and uniformly delivers Li ions to the SINP surfaces through a solid–solution reaction. The Si/C anode exhibits improved rate capability compared to that of the SINPs, with a 30% higher capacity retention over 50 cycles. Furthermore, even in a graphite-silicon (G-Si) composite anode, the G-Si/C anode showed a capacity retention rate of 99.5% over 100 cycles, which is superior to the performance of silicon-based anode materials; hence, it is a potential candidate for use in long-life G-Si composite anodes

Asymmetric Energy Storage Devices Based on Surface-Driven Sodium-Ion Storage

Energy storage devices (ESDs) based on Na ions are potential sustainable power sources for large-scale applications. However, they suffer from an unsatisfactory electrochemical performance originating from the unfavorable intercalation of large and heavy Na ions. In this study, two different types of nanostructured carbons were fabricated from renewable bioresources by simple pyrolysis and used as an anode/cathode pair for surface-driven Na-ion storage. Hierarchically porous carbon nanowebs (HP-CNWs) composed of highly defective pseudographitic layers were prepared from bacterial cellulose and used as the anode for Na-ion storage. In contrast, the corresponding cathode consisted of functionalized microporous carbon nanosheets (FM-CNSs) fabricated from waste coffee grounds. The HP-CNWs and FM-CNSs exhibited pseudocapacitive Na-ion storage, achieving remarkably fast and stable energy storage for the anodic and cathodic potential ranges, respectively. Moreover, asymmetric ESDs based on HP-CNWs and FM-CNSs showed a high specific energy of ∼130.6 W h kg^–1 at ∼210 W kg^–1 and a high specific power of ∼15,260 W kg^–1 at 43.6 W h kg^–1 with a stable behavior over 3,000 cycles

Sulfur-Doped Carbon Nanotemplates for Sodium Metal Anodes

Sodium metal is a good candidate as an anode for a large-scale energy storage device because of the abundance of sodium resources and its high theoretical capacity (∼1166 mA h g^–1) in a low redox potential (−2.71 V versus the standard hydrogen electrode). In this study, we report effects of sulfur doping on highly efficient macroporous catalytic carbon nanotemplates (MC-CNTs) for a metal anode. MC-CNTs resulted in reversible and stable sodium metal deposition/stripping cycling over ∼200 cycles, with average Coulombic efficiency (CE) of ∼99.7%. After heat treatment with elemental sulfur, the sulfur-doped MC-CNTs (S-MC-CNTs) showed significantly improved cycling performances over 2400 cycles, with average CEs of ∼99.8%. In addition, very small nucleation overpotentials from ∼6 to ∼14 mV were achieved at current densities from 0.5 to 8 mA cm^–2, indicating highly efficient catalytic effects for sodium metal nucleation and high rate performances of S-MC-CNTs. These results provide insight regarding a simple but feasible strategy based on bioabundant precursors and an easy process to design a high-performance metal anode

Hierarchically Porous Carbon Nanosheets from Waste Coffee Grounds for Supercapacitors

The nanostructure design of porous carbon-based electrode materials is key to improving the electrochemical performance of supercapacitors. In this study, hierarchically porous carbon nanosheets (HP-CNSs) were fabricated using waste coffee grounds by in situ carbonization and activation processes using KOH. Despite the simple synthesis process, the HP-CNSs had a high aspect ratio nanostructure (∼20 nm thickness to several micrometers in lateral size), a high specific surface area of 1945.7 m² g^–1, numerous heteroatoms, and good electrical transport properties, as well as hierarchically porous characteristics (0.5–10 nm in size). HP-CNS-based supercapacitors showed a specific energy of 35.4 Wh kg^–1 at 11250 W kg^–1 and of 23 Wh kg^–1 for a 3 s charge/discharge current rate corresponding to a specific power of 30000 W kg^–1. Additionally, the HP-CNS supercapacitors demonstrated good cyclic performance over 5000 cycles

Ultra Strong Pyroprotein Fibres with Long-range Ordering

<p><b>Figure 1 | Schematic of long-range ordered pyroprotein-based fibre.</b> <b>a</b>, The structure of silk composed of highly aligned β-sheet crystals organised by the self-assembly of GX repeat units through a number of inter-/intra-chain hydrogen bonds and surrounding amorphous domains consisting of non-repetitive peptide chains. <b>b</b>, At temperatures in excess of 800 °C, disordered poly-hexagonal carbon units are formed by the pyrolysis of poly-peptide molecules. <b>c</b>, Following heating to 2,800 °C, the disordered poly-hexagonal carbon units developed into pseudo-graphitic domains. <b>d</b>, By axial stretching, pyroprotein-based fibres with well-arranged poly-hexagonal carbon units along the fibre axis are formed by heating to 800 °C. <b>e,</b> Long-range ordered graphitic structures evolve following heating to 2,800 °C.</p> <p><b> </b></p> <p><a><b>Figure 2 | </b></a><a><b>X-ray diffraction profiles of pyroprotein-based fibres by heating to 2,800 </b></a><b>°C</b><b>. </b><b>a,b</b> WAXD patterns, <b>c</b>,<b>d</b>, 1D radial integration profiles of entire 2D patterns, and <b>e</b>,<b>f</b>, 1D azimuthal intensity profiles of the radially integrated (002) peak with Gaussian fits for silk-fibre samples treated at different temperatures with and without axial stretching, respectively. </p> <p> </p> <p><a><b>Figure 3 | Heat-treatment temperature dependent microstructural characteristics of pyroprotein-based fibres by heating to 2,800 </b></a><b>°C.</b> <b>a</b>,<b>b</b>, Raman spectra, and <b>c</b>,<b>d</b>, TEM and selected area diffraction patterns of the pyroprotein-derived fibres with and without axial stretching, respectively, as a function of the HTT. The scale bars in the top-left image in panel c and d represent 10 nm. </p> <p> </p> <p><b>Figure 4 | Mechanical and electrical properties of the pyroprotein-based fibres as a function of the heat-treatment temperature. </b><b>a</b>, Tensile strength and <b>b</b>, Young’s modulus of the pyroprotein-derived fibre samples treated at different temperatures with axial stretching. <b>c</b>, Photograph of the SSF1200 bundle enduring 0.5 kg of loading weight. <b>d</b>, <i>V-I</i>​ curves of the pyroprotein-derived fibres for various HTTs and (inset) the conductivity obtained from the inverse slope of <i>V-I</i>​ curves as a function of the HTT.</p

Long-Lasting Nb₂O₅‑Based Nanocomposite Materials for Li-Ion Storage

Advanced nanostructured hybrid materials can help us overcome the electrochemical performance limitations of current energy storage devices. In this study, three-dimensional porous carbon nanowebs (3D-CNWs) with numerous included orthorhombic Nb₂O₅ (T-Nb₂O₅) nanoparticles were fabricated using a microbe-derived nanostructure. The 3D-CNW/T-Nb₂O₅ nanocomposites showed an exceptionally stable long-term cycling performance over 70 000 cycles, a high reversible capacity of ∼125 mA h g^–1, and fast Li-ion storage kinetics in a coin-type two-electrode system using Li metal. In addition, energy storage devices based on the above nanocomposites achieved a high specific energy of ∼80 W h kg^–1 together with a high specific power of ∼5300 W kg^–1 and outstanding cycling performance with ∼80% capacitance retention after 35 000 cycles

Conversion Reaction of Copper Sulfide Based Nanohybrids for Sodium-Ion Batteries

Intercalation-based anode materials for Na-ion batteries show relatively unfavorable electrochemical performances compared with those of Li-ion batteries because of the larger and heavier Na ion, as well as its higher electrode potential. In contrast, conversion-reaction-based anode materials have great potential for use in Na-ion batteries. In this study, copper sulfide nanodisks (CuS-NDs) were fabricated by a simple low-temperature reaction and applied as the anode materials for Na-ion batteries with acid-treated single-walled carbon nanotubes (a-SWCNTs), which act as a paperlike nanohybrid. The nanohybrids had a high reversible capacity of ca. 610 mA h g^–1 and high rate capabilities at current rates from 0.1 to 3 A g^–1 during the conversion reaction that reversibly forms Na₂S and Cu metal. In addition, their electrochemical performances were stable and were maintained over 500 repetitive cycles; this stability arises from the unique nanohybrid structure, in which CuS-NDs are bound together by the a-SWCNT network

Tuning the Carbon Crystallinity for Highly Stable Li–O₂ Batteries

The Li–O₂ battery is capable of delivering the highest energy density among currently known battery chemistries and is thus regarded as one of the most promising candidates for emerging high-energy-density applications such as electric vehicles. Although much progress has been made in the past decade in understanding the reaction chemistry of this battery system, many issues must be resolved regarding the active components, including the air electrode and electrolyte, to overcome the presently insufficient cycle life. In this work, we demonstrate that the degradation kinetics of both the air electrode and electrolyte during cycles can be significantly retarded through control of the crystallinity of the carbon electrode, the most frequently used air electrode in current Li–O₂ batteries. Using ¹³C-based air electrodes with various degrees of graphitic crystallinity and in situ differential electrochemical mass spectroscopy analysis, it is demonstrated that, as the crystallinity increases in the carbon, the CO₂ evolution from the cell is significantly reduced, which leads to a 3-fold enhancement in the cyclic stability of the cell