Fast Ion Diffusion Research Articles

Sustainable SiO2 Nanostructures from Different Diatom Species As Anode Material for Future Generation Lithium-Ion Batteries

Energy harvesting and storage devices occupy a more prominent place in the 21st century than at any time in the past. Intensive efforts have been devoted to next-generation energy storage devices such as rechargeable lithium-ion batteries (LIBs) to develop high energy density and long cycle life electrode materials from sustainable sources. In the present anode, graphite is severely restricted by capacity and unavoidable solid electrolyte interface (SEI) formation. Besides, it has been listed as a critical material by the European Commission. Recently, silicon-based electrodes have been pinpointed as promising anode candidates due to their high theoretical capacity (~4200 mAhg-1 for Li4.4Si), low operating voltage (0.4V/Li/Li+), abundant resources, and environmental friendliness. Interestingly, nanostructures of Silica (SiO2) can be extracted from the frustules (exoskeletons) of a type of microalgae called diatoms. In this current work, SiO2 frustules were grown from two different diatom species, constituting a sustainable source for producing nanostructured Si-based materials. Scanning electron microscopy (SEM) images confirmed the highly nanoporous structure of diatom silica, which was retained even after ball-milling. The electrochemical performance of SiO2 was investigated as an anode material for LIBs. Herein, we have tested both species A & B milled and un-milled samples (denoted as SPAUM, SPAM, SPBUM, and SPBM). The diatom SiO2 un-milled species A (SPAUM) exhibited a high specific capacity of ~ 810 mAhg-1 with remarkable capacity retention and coulombic efficiency even after 100 cycles at 0.1 Ag-1 and delivered a high specific capacity of ~ 400 mAhg-1 even at high current density 3 Ag-1. For comparison and understanding, commercially available diatomaceous earth milled, and un-milled silica (denoted as EDAM & EDAUM) has been subjected to the same cycling protocol. Results clearly showed species A & B milled and un-milled displaying better electrochemical performance than diatomaceous earth milled and un-milled silica. Such improved electrochemical properties like cycle life, and rate capability of SPAUM are mainly ascribed to their highly porous nature which significantly facilitates fast Li ion diffusion, its unique morphology, which favors a faster kinetics and its complete lithiation/de-lithiation after the initial activation cycle. In view of the superior electrochemical properties, such sustainably sourced SiO2 materials can be considered a potential anode material for future LIBs. Figure 1

Peptide Gel Electrolytes for Stabilized Zn Metal Anodes.

The rechargeable aqueous Zn ion battery (AZIB) is considered a promising candidate for future energy storage applications due to its intrinsic safety features and low cost. However, Zn dendrites and side reactions (e.g., corrosion, hydrogen evolution reaction, and inactive side product (Zn hydroxide sulfate) formation) at the Zn metal anode have been serious obstacles to realizing a satisfactory AZIB performance. The application of gel electrolytes is a common strategy for suppressing these problems, but the normally used highly cross-linked polymer matrix (e.g., polyacrylamide (PAM)) brings additional difficulties for battery assembly and recycling. Herein, we have developed a gel electrolyte for Zn metal anode stabilization, where a peptide matrix, a highly biocompatible material, is used for gel construction. Various experiments and simulations elucidate the sulfate anion-assisted self-assembly gel formation and its effect in stabilizing Zn metal anodes. Unlike polymer gel electrolytes, the peptide gel electrolyte can reversibly transform between gel and liquid states, thus facilitating the gel-involved battery assembly and recycling. Furthermore, the peptide gel electrolyte provides fast Zn ion diffusion (comparable to conventional liquid electrolyte) while suppressing side reactions and dendrite growth, thus achieving highly stable Zn metal anodes as validated in various cell configurations. We believe that our concept of gel electrolyte design will inspire more future directions for Zn metal anode protection based on gel electrolyte design.

Te hexagonal nanotubes with fast 1-dimensional Zn ion diffusion for high-performance zinc-ion battery cathodes

The need for advanced next-generation secondary batteries have been urgently demanded for improved, sustainable, and eco-friendly energy storage systems. Aqueous rechargeable zinc ion batteries (ARZIBs) have garnered substantial attention as a substitute for lithium-ion batteries owing to their exceptional stability, environmentally friendly features, and cost-effectiveness. In this study, it is found that tellurium hexagonal nanotubes with a unique crystal growth orientation of [001] are of promising cathode materials for enhancing the performance of zinc ion batteries owing to their outstanding reaction kinetic properties. Additionally, the hollow interior of the nanotubes effectively mitigates the volume changes of tellurium during the charging and discharging processes. These research findings are expected to solidify the potential of tellurium hexagonal nanotubes as reliable cathode materials, significantly contributing to the commercialization of zinc ion battery technology in the future.

(Invited) Nanostructured Solid State Battery Architectures Enabled by Atomic Layer Deposition

Solid state batteries (SSBs) are considered the most promising next-generation energy storage technology both due to their increased safety over conventional wet Li-ion cells and their ability to fabricate novel architectures with simultaneous high energy and power density. However, the ionic conductivities of many solid electrolyte materials are orders of magnitude lower than liquid carbonate-based electrolytes. In order to offer SSBs with competitive charge/discharge rates, SSB active layers need to be thin (for fast ion diffusion) but have a large surface area (to enable large ion flux from anode to cathode). These geometric constraints establish the need for 3D electrode (and solid electrolyte) structures for a high performance battery architecture. Atomic layer deposition (ALD) is ideally suited to fabricate such devices due to its highly conformal nature and Angstrom-scale thickness control, however many challenges remain with materials fabrication and process integration.I will discuss development of both plasma-enhanced ALD (PEALD) and thermal ALD processes for the Li, Na, and K alkali polyphosphazene (A*PON) electrolytes1,2,3,4. The PEALD A*PON processes, by virtue of their 4-precursor synthesis route, allow some degree of chemical composition tuning. The thermal A*PON processes, unlike their PEALD counterparts, have a predetermined P-N ratio fixed by use of the precursors, however there is a tradeoff between the low temperature deposition enabled using plasma-based A*PON processes, and the conformality offered using the thermal A*PON processes. I will discuss and compare the reaction mechanisms and growth behavior among the entire family of A*PON solid electrolyte thin films, as well as discuss the integration challenges on the path to developing all-ALD planar and 3D SSBs. Pearse, A.; Schmitt, T.; Sahadeo, E.; Stewart, D. M.; Kozen, A.; Gerasopoulos, K.; Talin, A. A.; Lee, S. B.; Rubloff, G. W.; Gregorczyk, K. E., Three-Dimensional Solid-State Lithium-Ion Batteries Fabricated by Conformal Vapor-Phase Chemistry. ACS Nano 2018, 12 (5), 4286-4294. Pearse, A. J.; Schmitt, T. E.; Fuller, E. J.; El-Gabaly, F.; Lin, C.-F.; Gerasopoulos, K.; Kozen, A. C.; Talin, A. A.; Rubloff, G.; Gregorczyk, K. E., Nanoscale Solid State Batteries Enabled by Thermal Atomic Layer Deposition of a Lithium Polyphosphazene Solid State Electrolyte. Chemistry of Materials 2017, 29 (8), 3740-3753. Nuwayhid, R. B.; Jarry, A.; Rubloff, G. W.; Gregorczyk, K. E., Atomic Layer Deposition of Sodium Phosphorus Oxynitride: A Conformal Solid-State Sodium-Ion Conductor. ACS Applied Materials & Interfaces 2020, 12 (19), 21641-21650. Kozen, A. C.; Pearse, A. J.; Lin, C-F.; Noked, M.; Rubloff, G. W.; Atomic Layer Deposition of the Solid Electrolyte LiPON. Chemistry of Materials 2015, 27 (15), 5324-5331.

Investigation of Transition Metal Oxides & Phosphates for Zn-Ion/Zn-Air Batteries

Being a champion in a portable electronics world, lithium-ion batteries (LIBs) are irreplaceable, but the scarcity of Li, high cost, and the inclusion of non-aqueous electrolytes make them relatively perilous and inefficient for grid-scale energy storage. Recently, the blooming aqueous Zn-ion batteries (ZIBs) have emerged as one of the pioneer candidates featuring the inherently safe nature of metallic Zn anode and its unique properties.[1] Vanadium-based compounds show fast ion diffusion and excellent reversible capacity because of their rich valence state of vanadium, facile distortion of V-O polyhedrons, and tuneable composition, which offers an excellent treasure house. Moreover, the different oxidation states of vanadium allow a higher degree of structural change and greater functional flexibility while incorporating multivalent cations into vanadium-based compounds. [2] The present work focuses on one V-based oxide cathode. The cathode, ZnV2O4, synthesized by a simple solid-state route, showed a reversible capacity of around 200 mAh/g at a current density of 500 mA/g. Ex-situ XAS suggested that there is a drastic change in V and Zn local environment, confirming that there is a structural transformation taking place. Further, we have pursued ex-situ TEM where segregation of the conversion product phases was seen, confirmed by the small crystalline domains present at the nanoscale regime. A detailed analysis will be discussed to verify that a phase transformation is happening and is getting amorphized in subsequent cycles using ex-situ TEM and XAS.Also, metal-air batteries are widely discussed and studied because of their high energy density. In this pursuit, highly efficient bifunctional electrocatalysts, non-noble such as Co metal-based phosphates/oxides, have been studied vividly.[3,4] Herein, we present a thorough study of three-dimensional ZnCo2(PO4)2 (ZCP), which showed excellent bifunctional activity compared to the benchmark catalysts, denoting the presence of many catalytically active Co sites in ZCP. The presence of asymmetric edge-sharing CoO5/CoO6 polyhedra enhances the net catalytic activity.[5] ZCP exhibited robust oxygen reduction and evolution (ORR and OER) activity with the onset of 0.87 and 1.50 V vs. RHE for ORR and OER, respectively. The ORR saturated current density for ZCP was 6.38 mA/cm2, close to the 20% Pt/C catalyst benchmark. It also showed an OER exchange current density of 16.7 mA/cm2, closer to RuO2 ( j= 17.6 mA/cm2). This bifunctional electrocatalytic activity will be elaborated using analytical tools and DFT, along with the demonstration of Zn-air batteries. A detailed structural characterization using synchrotron refinement, TEM analysis, magnetic studies, and electrocatalysis performance will be discussed. Reference s : [1] M. Song et al., Adv. Funct. Mater. 2018, 28, 1802564.[2] Yao. Zhang et al., Chem. Front. 2021, 5 744-762.[3] J. L. Jung et al., Energy Environ. Sci. 2016, 9176-183.[4] W. Liu et al., Acc. Chem. Res . 2018,51,1858.[5] A. Baby et al., Chem. Comm. 2020, 56, 8400-8403.

Elucidating the Role of Anion Groups in Lithium-Ion Diffusion

Since the 1960s, the paddlewheel effect has been proposed as a way to enhance lithium-ion diffusion in inorganic materials by using rotor-like anion groups to assist lithium-ion movement(1–5). However, so far the physical mechanism behind how anion-group dynamics affect lithium-ion diffusion has not been clearly understood. In this talk, we clearly define various types of rotational motions of anion-groups. Based on such definition, we detect and differentiate such distinct anion-group rotational motions throughout a total of 10’s of ns ab-initio molecular dynamics trajectories. By performing rigorous statistical analysis of various rotational events as well as lithium-ion diffusion events, we reveal how each type of anion rotational motions are related to lithium-ion diffusion. Our research has finally resolved the ongoing debate about the existence of the paddlewheel effect and provide a clear physical understanding of how anion-group rotations are related to fast ionic diffusion in inorganic materials. L. Karlsson, R. L. McGreevy, Mechanisms of ionic conduction in Li2SO4 and LiNaSO4: Paddle wheel or percolation? Solid State Ionics. 76, 301–308 (1995).A. Kvist, A. Lundén, Electrical Conductivity of Solid and Molten Lithium Sulfate. Zeitschrift Für Naturforschung. 20, 235–238 (1965).Z. Zhang, L. F. Nazar, Exploiting the paddle-wheel mechanism for the design of fast ion conductors. Nat Rev Mater, 1–17 (2022).J. G. Smith, D. J. Siegel, Low-temperature paddlewheel effect in glassy solid electrolytes. Nat Commun. 11, 1483 (2020).M. Jansen, Volume Effect or Paddle‐Wheel Mechanism—Fast Alkali‐Metal Ionic Conduction in Solids with Rotationally Disordered Complex Anions. Angewandte Chemie Int Ed Engl. 30, 1547–1558 (1991).

Tungsten oxide/nitrogen-doped carbon nanotubes composite catalysts for enhanced redox kinetics in lithium–sulfur batteries

The sluggish redox kinetics of polysulfides in lithium-sulfur (Li-S) batteries is a significant obstacle to their widespread adoption as energy storage devices. However, recent studies have shown that tungsten oxide (WO3) can facilitate the conversion kinetics of polysulfides in Li-S batteries. Herein, we fabricated host materials for sulfur using nitrogen-doped carbon nanotubes (N-CNTs) and WO3. We used low-cost components and simple procedures to overcome the poor electrical conductivity that is a disadvantage of metal oxides. The composites of WO3 and N-CNTs (WO3/N-CNTs) creates a stable framework structure, fast ion diffusion channels, and a 3D electron transport network during electrochemical reaction processes. As a result, the WO3/N-CNT-Li2S6 cathode demonstrates high initial capacity (1162 mA·h·g–1 at 0.5 C), excellent rate performance (618 mA·h·g–1 at 5.5 C), and a low capacity decay rate (0.093% up to 600 cycles at 2 C). This work presents a novel approach for preparing tungsten oxide/carbon composite catalysts that facilitate the redox kinetics of polysulfides conversion.

Controlled Growth of WO3 Photoanode under Various pH Conditions for Efficient Photoelectrochemical Performance.

Herein, the effects of the precursor solution's acidity level on the crystal structure, morphology, nucleation, and growth of WO3·nH2O and WO3 nanostructures are reported. Structural investigations on WO3·nH2O using X-ray diffraction and Fourier-transform infrared spectroscopy confirm that the quantity of hydrate groups increases due to the interaction between H+ and water molecules with increasing HCl volume. Surface analysis results support our claim that the evolution of grain size, surface roughness, and growth direction on WO3·nH2O and WO3 nanostructures rely on the precursor solution's pH value. Consequently, the photocurrent density of a WO3 photoanode using a HCl-5 mL sample achieves the best results with 0.9 mA/cm2 at 1.23 V vs. a reversible hydrogen electrode (RHE). We suggest that the improved photocurrent density of the HCl-5 mL sample is due to the efficient light absorption from the densely grown WO3 nanoplates on a substrate and that its excellent charge transport kinetics originate from the large surface area, low charge transfer resistance, and fast ion diffusion through the photoanode/electrolyte interface.

Multilevel Gradient-Ordered Silicon Anode with Unprecedented Sodium Storage.

While cost-effective sodium-ion batteries (SIBs) with crystalline silicon anodes promise high theoretical capacities, they perform poorly because silicon stores sodium ineffectively (capacity <40 mAh g-1 ). To address this issue, herein an atomic-order structural-design tactic is adopted for obtaining unique multilevel gradient-ordered silicon (MGO-Si) by simple electrochemical reconstruction. In situ-formed short-range-, medium-range-, and long-range-ordered structures construct a stable MGO-Si, which contributes to favorable Na-Si interaction and fast ion diffusion channels. These characteristics afford a high reversible capacity (352.7 mAh g-1 at 50mA g-1 ) and stable cycling performance (95.2% capacity retention after 4000 cycles), exhibiting record values among those reported for pure silicon electrodes. Sodium storage of MGO-Si involves an adsorption-intercalation mechanism, and a stepwise construction strategy of gradient-ordered structure further improves the specific capacity (339.5 mAh g-1 at 100mA g-1 ). Reconstructed Si/C composites show a high reversible capacity of 449.5 mAh g-1 , significantly better than most carbonaceous anodes. The universality of this design principle is demonstrated for other inert or low-capacity materials (micro-Si, SiO2 , SiC, graphite, and TiO2 ), boosting their capacities by 1.5-6 times that of pristine materials, thereby providing new solutions to facilitate sodium storage capability for better-performing battery designs.

Integration of Porous High‐Loading Electrode and Gel Polymer Electrolyte for High‐Performance Quasi‐Solid‐State Battery

AbstractThe practical applications of lithium‐ion batteries (LIBs) are challenged by safety concerns using liquid electrolytes (LEs). The gel polymer electrolytes (GPEs) are considered as a promising candidate to solve this safety issue. In addition, using high‐mass loading electrodes is essential to achieve high energy density. However, poor interfacial contact between electrode and electrolyte remains a challenging issue, particularly for the high‐mass‐loading electrode. Here, porous channels are constructed in electrodes with high active material loading using the melamine formaldehyde sponge, and then the GPE is penetrated into porous channels of electrodes through an in‐situ thermal induced polymerization. The porous electrode structure with sufficient surface area improves electrolyte percolation and fast ion diffusion kinetics, which enables a uniform distribution of Li‐ion flux and effectively homogenizes the local current density to realize uniform Li deposition. The half cells and anode‐free full cells using the integration of porous electrodes and in‐situ polymerized GPEs exhibit excellent discharge capacity and cycle stability. This integration method is applicable for fabricating batteries with high energy density and safety.

A permselective protection layer assembled by two-dimensional organic vermiculite produces a highly stable lithium metal anode for lithium-sulfur batteries

Designing a protective coating for the lithium metal anode is the crucial yet challenging solution to its practical applications. How to well isolate the reactants in electrolytes but allow fast and uniform ion diffusion is the greatest challenge for various high energy density batteries, e.g., lithium–sulfur batteries. Herein, we propose a permselective protect coating, which has the ability to accelerate the homogeneous fast Li-ion diffusion but block the polysulfide anion penetration, and obtain a dendrite-free and corrosion-resistive lithium metal anode. The above ion-sieving function is realized by a membrane assembled with cetyltrimethylammonium (CTA+)-modified two-dimensional organic vermiculite nanosheets. The enlarged interlayer spacing of the membrane with CTA+ and the negative charges on the vermiculite nanosheets enhance the fast Li-ion transmission across the membrane for uniform Li deposition. At the same time, the non-polar alkyl of CTA+ and the negatively charged surface effectively block the polysulfide adsorption and penetration. Therefore, the side reactions and dendrite growth are effectively suppressed, and with the high sulfur loading (5 mg/cm2) and limited E/S ratio, the assembled lithium–sulfur cell shows good cycling stability at 0.1C, revealing a high capacity retention of 65.9 % over 300 cycles.

Ultra-Thin Hydrogen-Organic-Framework (HOF) Nanosheets for Ultra-Stable Alkali Ions Battery Storage.

Organic frameworks-based batteries with excellent physicochemical stability and long-term high capacity will definitely reduce the cost, carbon emissions, and metal consumption and contamination. Here, an ultra-stable and ultra-thin perylene-dicyandiamide-based hydrogen organic framework (HOF) nanosheet (P-DCD) of ≈3.5nm in thickness is developed. When applied in the cathode, the P-DCD exhibits exceptional long-term capacity retention for alkali-ion batteries (AIBs). Strikingly, for lithium-ion batteries (LIBs), at current of 2 A g-1, the large reversible capacity of 108mA h g-1 shows no attenuation within 5000 cycles. For sodium-ion batteries (SIBs), the related capacity retains 91.7% within 10000 cycles compared to the initial state, significantly much more stable than conventional organic materials reported previously. Mechanism studies through ex situ and in situ experiments and theoretical density functional theory (DFT) calculations reveal that the impressive long-term performance retention originates from the large electron delocalization, fast ion diffusion, and physicochemical stability within the ultra-thin 2D P-DCD, featuring π-π and hydrogen bonding stacking, nitrogen-rich units, and low impedance. The advantageous features demonstrate that rationally designed stable and effective organic frameworks pave the way to utilizing complete organic materials for developing next-generation low-cost and highly stable energy storage batteries.

Metal organic framework derived NiCo layered double hydroxide anode aggregated with biomass derived reduced graphene oxide cathode: A hybrid device configuration for supercapattery applications

Metal-organic frameworks (MOFs), due to its exceptional characteristics like high specific surface area and design diversity, serve as an outstanding sacrificial template in forming layered double hydroxides (LDHs) for highly efficient electrodes in supercapattery devices. In this work, we have prepared bimetallic layered Nickel Cobalt LDH via in-situ etching of Co-ZIF, in different Nickel concentrations directly on Ni foam that enhances the interfacial contact between substrate and the material. The optimised NiCo LDH-2 sample exhibited remarkable electrochemical behaviour with fast electrolyte ion diffusion kinetics ideal for supercapattery device and delivered a high specific capacitance of 2567 Fg−1 at 1 Ag−1. Further, the supercapattery device assembled with Ni-Co LDH as anode and rGO derived from a sustainable source as cathode demonstrated an energy density of 21 Whkg−1, power density of 0.307 kWkg−1 and good cyclic stability with capacitance retention of 88.89 % along with coulombic efficiency of 90.58 % over 1500 cycles. This work proposes an effective approach for designing layered NiCo-LDH that can be further extended to the synthesis of other transition metal-derived LDH for supercapattery devices.

Stabilized Li-Rich Layered Oxide Cathode by a Spontaneously Formed Yb and Oxygen-Vacancy Rich Layer on the Surface.

Li-rich layered oxides (LLOs) are among the most promising cathode materials with high theoretical specific capacity (>250 mAh g-1 ). However, capacity decay and voltage hysteresis due tostructural degradation during cycling impede the commercial application of LLOs. Surface engineering and element doping are two methods widely applied tomitigate the structural degradation. Here, it is found that trace amount lanthanide element Yb doping can spontaneously form a surficial Yb-rich layer with high density of oxygen vacancy on the LLO-0.3% Yb (Li1.2 Mn0.54 Co0.13-x Ybx Ni0.13 O2 where x = 0.003) cathodes, which mitigating lattice oxygen loss and the non-preferred layered-to-spinel-to-rock salt tri-phase transition. Meanwhile, there are also some Yb ions doped into the lattice of LLO, which enhance the binding energy with oxygen and stabilize the lattice in grain interior during cycling. The dual effects of Yb doping greatly mitigate the structure degradation during cycling, and facilitate fast diffusion of lithium ions. As a result, the LLO-0.3% Yb sample achieves significantly improved cycling stability, with a capacity retention of 84.69% after 100 cycles at 0.2 C and 84.3% after 200 cycles at 1 C. These finding shighlight the promising rare element doping strategy that can have both surface engineering and doping effects in preparing LLO cathodes with high stability.

Fluoride-Rich, Organic-Inorganic Gradient Interphase Enabled by Sacrificial Solvation Shells for Reversible Zinc Metal Batteries.

Zinc metal batteries are strongly hindered by water corrosion, as solvated zinc ions would bring the active water molecules to the electrode/electrolyte interface constantly. Herein, we report a sacrificial solvation shell to repel active water molecules from the electrode/electrolyte interface and assist in forming a fluoride-rich, organic-inorganic gradient solid electrolyte interface (SEI) layer. The simultaneous sacrificial process of methanol and Zn(CF3SO3)2 results in the gradient SEI layer with an organic-rich surface (CH2OC- and C5 product) and an inorganic-rich (ZnF2) bottom, which combines the merits of fast ion diffusion and high flexibility. As a result, the methanol additive enables corrosion-free zinc stripping/plating on copper foils for 300 cycles with an average coulombic efficiency of 99.5%, a record high cumulative plating capacity of 10 A h/cm2 at 40 mA/cm2 in Zn/Zn symmetrical batteries. More importantly, at an ultralow N/P ratio of 2, the practical VO2//20 μm thick Zn plate full batteries with a high areal capacity of 4.7 mAh/cm2 stably operate for over 250 cycles, establishing their promising application for grid-scale energy storage devices. Furthermore, directly utilizing the 20 μm thick Zn for the commercial-level areal capacity (4.7 mAh/cm2) full zinc battery in our work would simplify the manufacturing process and boost the development of the commercial zinc battery for stationary storage.

Highly effective Cu doped SrTiO3 as a cathode driven by oxygen vacancies and redox of Ti4+/Ti3+ and Cu2+/Cu+ for rechargeable alkaline zinc batteries

There is great demand for environmental concerns and explosion hazard batteries. Rechargeable alkaline zinc batteries (RAZBs) have gained significant attention due to their exceptional characteristics such as affordability, safety features, and high theoretical gravimetric capacity. However, practically RAZBs still exhibit poor capacities and limited rechargeability. In this study, copper-doped SrTiO3 (Cu-STO) was successfully synthesized via facile hydrothermal method to be used as a cathode in RAZBs. The capacity of RZABs has enhanced up to 208 mAh g−1 (0.2 A g−1) or 1.5 folds as compared to that of pristine SrTiO3. This is attributed to the presence of oxygen vacancies (Vö) which facilitate the activation of redox-active sites involving Ti4+/Ti3+ and Cu2+/Cu+ ions. Moreover, the fast ions diffusion and good conductivity enable high capacity and rechargeability. Thus, RAZBs showed good rechargeability even after 1000 cycles under 1 A g−1. This provides the underlying potential of Cu-STO as cathode in RAZBs.

Accumulative Delocalized Mo 4d Electrons to Bound the Volume Expansion and Accelerate Kinetics in Mo6S8 Cathode for High-Performance Aqueous Cu2+ Storage.

Electronic structure defines the conductivity and ion absorption characteristics of a functional electrode, significantly affecting the charge transfer capability in batteries, while it is rarely thought to be involved in mesoscopic volume and diffusion kinetics of the host lattice for promoting ion storage. Here, we first correlate the evolution in electronic structure of the Mo6S8 cathode with the ability to bound volume expansion and accelerate diffusion kinetics for high-performance aqueous Cu2+ storage. Operando synchrotron energy-dispersive X-ray absorption spectroscopy reveals that accumulative delocalized Mo 4d electrons enhance the Mo-Mo interaction with distinctly contracting and uniformizing Mo6 clusters during the reduction of Mo6S8, which potently restrain lattice expansion and release space to promote Cu2+ diffusion kinetics. Operando synchrotron X-ray diffraction and comprehensive characterizations further validate the structural and electrochemical properties induced by the Cu2+ intercalation electronic structure, endowing the Mo6S8 cathode a high specific capacity with small volume expansion, fast ions diffusion, and long-term cycling stability.

Synergistically Stabilizing Thin Li Metal through the Formation of a Stable and Highly Conductive Solid Electrolyte Interface and Silver-Lithium Alloy.

In this study, a stable solid electrolyte interface (SEI) and a Ag-Li alloy were formed through a simple slurry coating of silver (Ag) nanoparticles and Li nitrate (LiNO3) on a Li metal surface (AgLN-coated Li). The Ag-Li alloy has a high Li diffusion coefficient, which allowed the inward transfer of Li atoms, thus allowing Li to be deposited below the alloy. Moreover, the highly conductive SEI enabled the fast diffusion of Li ions corresponding to the alloy. This inward transfer resulted in dendrite suppression and improved the Coulombic efficiency (CE). The AgLN-coated Li exhibited an initial capacity retention >81% and CE > 99.7 ± 0.2% over 500 cycles at a discharge capacity of 2.3 mA h cm-2.

Sequential processing of nitrogen-rich, biowaste-derived carbon quantum dots combined with strontium cobaltite for enhanced supercapacitive performance

Disposal of waste edible oil is a major concern for government regulatory bodies worldwide, with improper disposal leading to the blocking of sewer lines, polluting water bodies, and degrading the environment. In the present work, waste soybean oil is converted into soot and hydrothermally processed to produce nitrogen-rich carbon quantum dots (N-CQDs). The N-CQDs are further treated with strontium cobaltite (SC) prepared via the sol-gel method. A significant difference is observed in the morphology, surface area, and electrochemical performance of the N-CQDs (124 Fg−1), SC particles (106.7 Fg−1), and the combined SC@N-CQDs material (386.5 Fg−1). The bio derived SC@N-CQD sample is used as an electrode in a symmetrical supercapacitor, and the device shows EDLC behavior with co-contribution of minor pseudocapacitance due to the nitrogen functional groups and Co2+/Co3+ states of the SC. The SC@N-CQDs deliver an exceptionally high specific capacitance of 180.24 Fg−1 at 0.5 Ag−1 due to the enhanced surface area offered by the combined material, good conductivity imparted by the N-CQDs, and oxygen vacancies in the SC. The synergy leads to fast ion diffusion between the electrode and the electrolyte interface, and an additional boost is achieved by the pyrrolic-N and pyridinic-N present in the electrode material. The capacitance retention is 80.8% of the initial capacitance after 5000 cycles. The SC@N-CQD supercapacitor provides a high energy density of 7.51 Whkg−1 and can operate a red LED, thus demonstrating the efficient utilization of waste edible oils to yield high-performance material for supercapacitor applications. This study can have a broad environmental impact on the reduction and reuse of biowaste.

Mesoporous Ti-substituted NiO nanosheets as an efficient electrocatalyst for triiodide reduction in dye-sensitized solar cells

In this work, a novel two-dimensional hexagonal mesoporous nickel oxide (2D-HM NiO) and titanium substituted NiO (Ti (1, 3, 5, 7 and 9 mol%)-NiO) nanosheets (NSs) are synthesized via a one-step hydrothermal method. The as-prepared 2D-HM NiO and Ti (1–9%)-NiO NSs are used to fabricate cost-effective counter electrodes (CEs) for DSSCs. The DSSCs device made with NiO and 1% of Ti-substituted NiO (1-TNO) CEs show excellent electrochemical properties and photovoltaic performance. The 100 consecutive cycles of cyclic voltammetry (CV) shows that NiO and 1-TNO CEs have high chemical stability towards I−/I3− redox mediator as compared with Pt CE. For the first time, the power conversion efficiency (PCE) of DSSCs with NiO-based CE reached up to 4.08% whereas 1-TNO CE a PCE slightly increased up to 4.12% which is relatively closer to Pt-based CE (5.34%) under identical working conditions. The high performance of NiO and 1-TNO CEs can be attributed to the large number of electrocatalytic active sites and fast ion diffusion, which is due to the high specific surface area of the 2D nanosheet structure with mesoporous nature.