Active Cathode Research Articles

The effect of Cu oxidation states on C2H4 production from electrochemical CO2 conversion

Recently, many studies have reported on the significant role of Cuδ+/Cu0 in the production of C2H4, highlighting the enhanced activity of oxidized Cu electrodes compared to metallic Cu electrodes. However, there is relatively little research that compares catalytic performance for C2H4 production in membrane electrode assembly (MEA)-type cells. Herein, we present an analysis of the performance of Cu-based oxidized cathodes in MEA-type cells, specifically focusing on the Cu oxidation state in relation to the CO2 reduction reaction (CO2RR). Both metallic Cu and oxidized Cu cathodes were prepared via a simple electroless deposition and subsequent oxidation process. The electric, chemical, and thermal oxidation methods yielded Cu electrodes with distinct electronic structures. Subsequently, the CO2RR performance of these electrodes was evaluated in single MEA-type cells, and the correlation between the Cu0–1+ ratio and their performance was studied. Our findings confirmed that the ability to form C2H4 follows a volcano-shaped trend based on the Cu0–1+ ratio. Furthermore, a stability test was conducted for CO2RR at a cell voltage of 3.2 V, revealing that the initially highly active Cu-based cathode exhibited notably poor stability in the MEA-type cell test.

Electrochemical activity of copper doped Sr2.7Pr0.3Fe2O7−δ cathode catalysts for solid oxide fuel cells

Due to their great efficiency, low cost and pollution, and flexible fuel choice, solid oxide fuel cells (SOFCs) have been applied to energy conversion filed. However, one challenge for developing SOFCs is sluggish oxygen reduction reaction (ORR) rate. Herein, a series of Ruddlesden-Popper-type Sr2.7Pr0.3Fe2–xCuxO7–δ (SPFCx) oxides are successfully synthesized and thoroughly assessed as potential SOFCs cathodes. Among all compositions, Sr2.7Pr0.3Fe1·9Cu0·1O7–δ (SPFC10) possesses the best electrocatalysis performance and improved oxygen reduction kinetics, with the lowest polarization resistance (Rp, 0.13 Ω cm2) at 700 °C. Cu-doping will contribute to improving oxygen transport kinetics, increasing oxygen vacancy concentration, and O 2p band centers close to the Fermi level, hence, enhancing the electrocatalysis performance. At 700 °C, the maximum output of the single cell with SPFC10 cathode is 704 mW cm−2. These results highlight a highly active SPFC10 cathode with Ruddlesden-Popper structure for SOFCs.

Effect of Zn doping on Sr3Fe2O7-δ Ruddlesden-Popper oxides as active and robust cathodes for protonic ceramic fuel cells

Perovskite oxides are promising electrodes for protonic ceramic fuel cells (PCFCs) due to their good electrochemical performance and stability. However, the lower operating temperature results in a large polarization resistance and sluggish oxygen reduction reaction (ORR) in cathodes. Herein, Ruddlesden-Popper (R–P) type perovskite Sr3Fe2-xZnxO7-δ (SFZx, x = 0, 0.1, 0.5) were successfully synthesized and the partial replacement of Fe by Zn in SFZx demonstrates a superior ORR activity. At 750 °C, the polarization resistance of SFZ05 is 0.072 Ω cm−2, which is 47% lower than that of the undoped Sr3Fe2O7-δ (SFO), and the peak power density of the single-cell with an SFZ05 cathode reaches 523.56 mW cm−2. The distribution of relaxation time (DRT) results manifest that the rate-limiting steps of ORR are charge transfer and ionic migration processes. Furthermore, SFZ05 also presented better CO2 tolerance. These results show that SFZ05 is a promising cathode candidate with high activity and stability for PCFCs.

Electrochemically Assisted Construction of a La2NiO4+δ@Pt Core-Shell Structure for Enhancing the Performance and Durability of La2NiO4+δ Cathodes.

Ruddlesden-Popper oxide La2NiO4+δ (LNO) has a high ionic conductivity and good thermal match with the electrolyte of solid oxide fuel cells (SOFCs); however, LNO suffers from performance decay owing to the La surface segregation under the operation conditions of SOFCs. Herein, we report an in situ electrochemical decoration strategy to improve the electrocatalytic activity and durability of LNO cathodes. We show that the electrochemical polarization leads to in situ construction of the LNO@Pt core-shell structure, significantly suppressing the detrimental effect of La surface segregation on the LNO cathode. The initial peak power density of a single cell with the LNO cathode is 0.71 W cm-2 at 750 °C, increasing to 1.39 W cm-2 by the in situ construction of the LNO@Pt core-shell structure after polarization at 0.5 A cm-2 for 20 h. The LNO@Pt core-shell structure is also highly durable without noticeable performance degradation over the duration of the test for 180 h. The findings shed light on the design and fabrication of highly active and durable LNO-based cathodes for SOFCs.

Direct methanol fuel cell with enhanced oxygen reduction performance enabled by CoFe alloys embedded into N-doped carbon nanofiber and bamboo-like carbon nanotube

The exploration of cost-effective electrocatalysts with high catalytic activity and methanol tolerance to replace precious metal catalysts in the oxygen reduction reaction (ORR) is highly desirable for direct methanol fuel cells (DMFCs). Herein, we report a novel complex composed of a CoFe alloy with a modulated electronic structure confined to nitrogen-doped carbon nanofiber (NCNF) and bamboo-like carbon nanotube (BCNT) by tuning the molar ratio of Co and Fe (CoFe@NCNF/BCNT). The synthetized catalysts possess one-dimensional (1D) mesoporous structure, high specific surface area, and rich pyridinic-N content. Notably, the Co1Fe1@NCNF/BCNT and Co1Fe3@NCNF/BCNT (Co:Fe ≈ 1:1 and 1:3) exhibited enhanced oxygen reduction activity and methanol tolerance, compared to unmodified samples. In addition, alkaline DMFCs containing Co1Fe1@NCNF/BCNT and Co1Fe3@NCNF/BCNT presented high power density (29.10 and 31.11 mW cm−2), exceeding that of Pt/C-modified DMFC (27.23 mW cm−2). Furthermore, the Co1Fe1@NCNF/BCNT-catalyzed DMFC exhibited high stability. This improved catalytic activity can be attributed to the rich surface area, controllable alloy composition, optimized N configuration, and favorable electronic interaction. The as-developed CoFe@NCNF/BCNT with multifunctional components may open a new avenue for designing highly active cathode catalysts for various fuel cells.

LiFePO4 as a dual-functional coating for separators in lithium-ion batteries: A new strategy for improving capacity and safety

Lithium-ion batteries (LIBs) require separators with high performance and safety to meet the increasing demands for energy storage applications. Coating electrochemically inert ceramic materials on conventional polyolefin separators can enhance stability but comes at the cost of increased weight and decreased capacity of the battery. Herein, a novel separator coated with lithium iron phosphate (LFP), an active cathode material, is developed via a simple and scalable process. The LFP-coated separator exhibits superior thermal stability, mechanical strength, electrolyte wettability, and ionic conductivity than the conventional polyethylene (PE) separator. Moreover, the LFP coating can actively participate in the electrochemical reaction during the charge-discharge process, thus enhancing the capacity of the battery. The results show that the LFP-coated separator can increase the cell capacity by 26%, and improve the rate capability by 29% at 4 C compared with the conventional PE separator. The LFP-coated separator exhibits only 1.1% thermal shrinkage at 140 °C, a temperature even above the melting point of PE. This work introduces a new strategy for designing separators with dual functions for the next-generation LIBs with improved performance and safety.

Tailoring short-chain sulfur molecules to drive redox dynamics for sulfur-based aqueous battery

Solid-solid reactions stand out in rechargeable sulfur-based batteries due to the robust redox couples and high sulfur utilization in theory. However, conventional solid-solid reactions in sulfur cathode always present slow reaction kinetics and huge redox polarization due to the low electronic conductivity of sulfur and the generation of various electrochemical inert intermediates. In view of this, it is crucial to improve the electrochemical activity of sulfur cathode and tailor the redox direction. Guided by thermodynamics analysis, short-chain sulfur molecules (S2-4) are successfully synthesized by space-limited domain principle. Unlike conventional cyclic S8 molecules with complex routes in solid-solid reaction, short-chain sulfur molecules not only shorten the length of the redox chain but also inhibit the formation of irreversible intermediates, which brings excellent redox dynamics and reversibility. As a result, the Cu-S battery built by short-chain sulfur molecules can deliver a high reversible capacity of 3,133 mAh g-1. To put this into practice, quasi-solid-state aqueous flexible battery based on short-chain sulfur molecules is also designed and evaluated, showing superior mechanical flexibility and electrochemical property. It indicates that the introduction of short-chain sulfur molecules in rechargeable battery can promote the development and application of high-performance sulfur-based aqueous energy storage systems.

Neodymium-Doped Zinc Oxide Nanoparticles Catalytic Cathode for Enhanced Efficiency of Microbial Desalination Cells

The Microbial Desalination Cell is a novel method for desalinating water that also generates energy via substrate oxidation. The MDC comprises three chambers: the anode chamber, the desalination chamber, and the cathode chamber. The fundamental problem with the technology is that it generates very little power during the oxygen reduction reaction (ORR). One solution to this issue is to use a highly active cathode catalyst, which effectively increases the ORR rate. Neodymium-doped ZnO nanoparticles were produced and employed as a cathode catalyst in the three-chambered MDC1 to improve performance. Zn1−xNdxO nanocrystalline samples containing x = 0.0, 0.03, 0.6, and 0.10 were synthesized efficiently through the cost-efficient sol-gel method. Transmission electron microscopy (TEM) and X-ray diffraction techniques revealed the nanocrystalline nature and the phase purity of the Zn1−xNdxO samples. The structural properties of ZnO nanostructured materials were elucidated by Rietveld refinement of the XRD patterns, which showed displacement of Zn and O ions and revealed changes in the electron density around the Zn-O bond with Nd substitution. The local features of light emission from Zn1−xNdxO samples have been studied with photoluminescence. The UV and green-yellow emissions originate from the exciton transition and the transition between the Nd3+ deep level, oxygen vacancy and interstitial oxygen. The results were compared to MDC-2, which did not have a catalyst on the cathode. Both MDCs were tested using a saline water solution containing 15 g/L of NaCl to measure their desalination performance. The better reduction kinetics was confirmed by cyclic voltammetry of the MDC-1 cathode. MDC-1 had a higher desalination efficiency (77.02% ± 2.0%) due to the presence of an Nd-doped ZnO catalyst than MDC-2 (59.3% ± 8.3%). MDC-1’s maximum power density of 3.65 W/m3 was 2.78 times greater than MDC-2’s (0.78 W/m3). Furthermore, the coulombic efficiency of MDC-1 was found to be (8.8 ± 0.3%), which was much higher than that of MDC-2 (4.56 ± 0.2%). As a result, the Nd-doped ZnO-based catalyst developed in this study can potentially improve ORR in MDC cathodes, enabling them to generate more power.

Pronounced Strain Effects on Oxygen Dissociation; Pt‐ or Au‐Dispersed Pr2Ni(Cu, Ga)O4 for Active Cathode of Solid Oxide Fuel Cells

The correlation between lattice strain induced by metal dispersion into grain and the cathodic overpotential is studied for increasing oxygen‐dissociation activity and improving power density of solid oxide fuel cells (SOFC) at decreased temperature. Pt or Au dispersion in Pr1.90Ni0.71Cu0.21Ga0.05O4+d (PNCG) is prepared and the 3D tensile strain is successfully induced after sintering by a mismatch in thermal expansion coefficient. Due to higher hardness and melting temperature, Pt dispersion into bulk of PNCG introduces larger tensile strain than that by Au at the same amount. In particular, at 1 mol% Pt dispersion, large tensile strain of 0.67% is induced. Overpotential of 1 mol% Pt‐PNCG cathode is 8 times smaller (35 mV) than that of PNCG (270 mV) at 800 °C and 300 mA cm−2, and it is found that the cathodic overpotential of PNCG is decreased with tensile strain on both Pt and Au dispersion. This cathodic activity enhancement appears to be related with the increased diffusivity of oxide ion in PNCG. In this study, cathodic overpotential is more significantly influenced by the induced tensile strain comparing with the intrinsic catalytic activity of the dispersed metal.

Unveiling the effect of Al–Mn intermetallic on the micro-galvanic corrosion of AM50 Mg alloy in NaCl solution

The influence of Al–Mn intermetallic on corrosion resistance of AM50 alloy was investigated. TEM-SAED was utilized to identify microstructure and composition of the corrosion products on Al–Mn intermetallic. The electrochemistry results revealed that the corrosion rate of pure Mg was lower than AM50 due to thermodynamic driving force for micro-galvanic corrosion by Al–Mn with matrix. Although the Volta potential difference reduce because of accumulation of corrosion products, the cathodic activity of AM50 alloy increases with exposure time. The progress of corrosion could not be inhibited since the loose and porous corrosion products provided an area for containing and storing the corrosion medium.

Graphene quantum dots as sulfiphilic and lithiophilic mediator toward high stability and durable life lithium-sulfur batteries

The development of lithium-sulfur (Li-S) battery as one of the most attractive energy storage systems among lithium metal batteries is seriously hindered by low sulfur utilization, poor cycle stability and uneven redeposition of Li anode. It is necessary to propose strategies to address the problems as well as improve the electrochemical performance. One of the effective solutions is to improve the sulfiphilicity of sulfur cathode and the lithiophilicity of the Li anode. Herein, we reported that a synergistic functional separator (graphene quantum dots (GQDs)-polyacrylonitrile (PAN) @polypropylene (PP) separator) improved the electrochemical activity of sulfur cathode as well as the stability of Li anode. GQDs induced uniform Li+ nucleation and deposition, which slowed down the passivation of Li anode and avoided short-circuit. Further, three-dimensional network constructed by electrospinning nanofibers and the polar functional groups of GQDs could both effectively inhibit the shuttle of LiPSs and improve the sulfur utilization. The stability of Li-S battery was improved by the synergistic effect. In addition, GQDs and electrospinning nanofibers protector increased lifetime of separators. Benefiting from the unique design strategy, Li//Li symmetric battery with GQDs-PAN@PP separators exhibited stably cycling for over 600 h. More importantly, the Li-S full batteries based GQDs-PAN@PP separators enabled high stability and desirable sulfur electrochemistry, including high reversibility of 558.09 mA h g−1 for 200 cycles and durable life with a low fading rate of 0.075% per cycle after 500 cycles at 0.5 C. Moreover, an impressive areal capacity of 3.23 mA h cm−2 was maintained under high sulfur loading of 5.10 mg cm−2. This work provides a new insight for modification separator to improve the electrochemical performance of Li-S/Li metal batteries.

Design of atomic cobalt selenide-doped sulfurized polyacrylonitrile cathode with enhanced electrochemical kinetics for high performance lithium-SPAN batteries

In this work, sulfurized polyacrylonitrile (SPAN) cathodes with atomically dispersed Co and Se active site, namely cobalt selenide doped-sulfide polyacrylonitrile (CoSe2-x@SPAN, x = 6, 10, 15) with different CoSe2 doping concentrations of 6, 10, and 15 wt%, were fabricated by co-heating approach to strengthen the charge conductivity and catalytic activity of SPAN cathode. Atomic scale CoSe2 were doped into the SPAN skeleton to expediating the redox kinetics of lithium storage process, and the catalytic mechanism was made clear by a viewing angle of frontier molecular orbital theory. The DFT calculation results show that CoSe2@SPAN has a more uniform electrostatic potential distribution with a smaller LUMO-HOMO band gap, which is more conducive to electron transport. The Co/Se loaded SPAN polymer constructed by N-Co-S chemical coordination improves the matching degree between the highest occupied molecular orbital (HOMO) of the nucleophile S2− and the lowest unoccupied molecular orbital (LUMO) of the electrophile Li+ during the discharge process, and effectively reduces the bonding orbital σ level of the deposited product Li2S, thereby promoting the lithium storage kinetics of CoSe2@SPAN cathode material and avoiding the shuttle effect. Meanwhile, the larger Gibbs free energy variation during the lithiation process indicates the enhanced reaction kinetics of the CoSe2@SPAN cathode. Ultimately, The Li-SPAN battery with CoSe2-10@SPAN cathode delivers high reversible capacity of 1475 mAh g−1 at 0.2 A/g, superior rate capability and long-term capacity retention of 71.1% after 500 cycles at 1.0 A/g. Accordingly, this study offers insights into the utilization of frontier molecular orbital theory (FMO) to improve the redox kinetics and sulfur utilization of Li-SPAN batteries.

Hollow Raspberry-like CoSx/C Sub-Microspheres as a Highly Active Air Cathode Catalyst for Rechargeable Zinc-Air Batteries

Hollow Raspberry-like CoS_<i>x</i>/C Sub-Microspheres as a Highly Active Air Cathode Catalyst for Rechargeable Zinc-Air Batteries

Large oxygen reduction response of CaFe2O4-WO3 heterostructure composite for protonic ceramic fuel cell cathode

Protonic Ceramic fuel cells (PCFCs) hold great promise for many applications; however, their high operating temperature hinders their commercial use in practice. The crucial issue that limits the electrochemical performance of PCFCs (including oxygen and proton-ion-conducting) is the sluggish oxygen redox reaction (ORR) at the cathode surface at low operating temperatures. Herein, we have developed a CaFe2O4-WO3heterostructure composite by interface-vacancy engineered for an efficient ORR electrocatalyst for LT-PCFCs. The CaFe2O4-WO3 heterostructure composite exhibits very low cathodic area-specific resistance (ASR) and high oxygen reduction reaction (ORR) activity response at low operating temperatures of 400–550 °C using a BaCe0.7Zr0.2Y0.1O3-δ (proton-conducting) electrolyte. We have demonstrated high-power density of 585 ± 2% mW-cm−2 with a current density of 1660 mA-cm−2 at 550 °C with H2 fuel and atmospheric air as oxidant and even with possible operation at 400 °C. Moreover, the CaFe2O4-WO3heterostructure composite shows a very low proton migration energy and activation energy compared to individual CaFe2O4 and WO3, helping to promote ORR activity. Various spectroscopic measurements, such as X-ray diffraction, high resolution transmission electron microscopy (HR-TEM), U-visible spectroscopy (UV–visible), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) calculations are employed to understand the interfacial properties for the improved ORR electrocatalytic activity of the CaFe2O4-WO3 heterostructure composite cathode. Our obtained experimental and theoretical results can further help to develop functional cobalt-free electrocatalysts for LT-PCFCs.

Electrode potential, inflammatory solution chemistry and temperature alter Ti-6Al-4V oxide film properties

Post implantation, a thin TiO2 film protects Ti-6Al-4V in vivo. Mechanically and chemically destructive conditions may disrupt this oxide film and promote corrosion at the device interface. While tribocorrosion has been explored in vitro, pre-clinical tests fail to fully reproduce the damage documented on retrievals. A gap persists in our fundamental knowledge of the oxide film and its response to adverse electrochemical events. In this study, we first characterized the TiO2 oxide film structure after inducing β phase selective dissolution. Next, we used electrochemical impedance spectroscopy and Mott-Schottky analysis to investigate the oxide film on freshly prepared surfaces following negative potential excursions. We systematically increased electrode potential from -1 V vs. Ag/AgCl in 0.1 V steps to +0.5 V. Various H2O2 concentrations (0.1 M to 0.001 M) in phosphate buffered saline and temperatures ranging from 24 °C to 55 °C were investigated. Atomic force microscopy showed morphological changes to oxide domes over the α phase following β phase selective dissolution. Below the Ti-6Al-4V open circuit potential (ca. -0.3 V), we identified systematic variations in polarization resistance (Rp) and capacitance (C) with potential, solution chemistry, and temperature. The combined effect of cathodic activation and H2O2 solution concentration synergistically and systematically decreased Rp by orders of magnitude (p = 0.000). Increased solution temperatures decreased Rp (p = 0.000). At high concentrations of ROS (0.1 M), we documented changes in constant phase element capacitance, from n-type to p-type. Finally, we developed empirical equations to predict Rp for a given concentration, temperature, and potential. In totality, these experiments help to further elucidate the complex interactions at the oxide-biology interface in vivo and provide guidance for in vitro testing methods development.

Highly Conductive Iodine and Fluorine Dual-Doped Argyrodite Solid Electrolyte for Lithium Metal Batteries

Sulfide-type argyrodite solid electrolytes (SEs) with halide doping have attracted serious interest. Although other halides such as Cl and Br have been found to enhance Li-ion transport in argyrodites, the direct synthesis of efficiently conductive Li6PS5I without postprocessing has rarely been investigated. In this work, we report the one-step synthesis of highly conductive Li6PS5I with an impressive ionic conductivity of 2.5 × 10–4 S cm–1 at room temperature through a solvent-based method. Moreover, by introducing F– to partially replace I–, hybrid-doped argyrodites Li6PS5FxI1–x (x = 0.25, 0.5, 0.75) have been synthesized. Li6PS5F0.25I0.75 achieves the highest conductivity of 3.5 × 10–4 S cm–1 due to the energetic preference for anion-disordering among F–/I– and S2–, which facilitate faster Li transport as supported by density functional theory (DFT) calculations. With higher F content in argyrodites, Li6PS5F0.75I0.25 displays the best electrochemical stability toward Li metal, as evidenced by long-term stable cycling in Li symmetric cells up to 1100 h. Solid-state Li metal batteries with an active cathode of Li4Ti5O12 (LTO) display an initial specific capacity of 140 mAh g–1 and remain at 105 mAh g–1 after 200 cycles, suggesting great battery cycling performance. This research has developed new compositions in the argyrodite SE family which could lead to advancements in the development of solid-state Li metal batteries.

Defect-Rich MoO3 Nanobelts for ultrafast and wide-temperature proton battery

Protons (H+) are considered as ideal charge carries for rechargeable batteries because of the small size, high ionic mobility and wide availability. In this work, MoO3 nanobelts with rich defects are prepared by simple hydrothermal treatment of MoO3 nanoparticles and are demonstrated as high-performance electrode materials for proton battery. Benefiting from the nanobelt morphology, abundant oxygen vacancy, large interlayer spacing, improved conductivity and fast ion transfer, the MoO3 nanobelts electrode delivers a state-of-the-art capacity of 285.3 mAh g−1 at the current density of 1.0 A g−1, and ∼75% of the initial capacity is retained at 50.0 A g−1. It is found that the MoO3 nanobelts electrode can still maintain its original capacity, nanobelt morphology and crystal structure even after 23,000 cycles. Notably, the electrode delivers a high areal capacity of 3.48 mAh cm−2 at a high mass loading of 16.0 mg cm−2. The proton battery assembled with MoO3 nanobelts anode and N-doped active carbon cathode shows the maximum energy density of 46.2 Wh kg−1 at the power density of 800.3 W kg−1. The proton battery shows satisfactory proton storage properties at a wide temperature range of -25°C ∼ 65°C. This study provides insights into the design of ultrafast and wide-temperature proton battery for practical applications.

Enhancing Electrochemical CO2 Reduction on Perovskite Oxide for Solid Oxide Electrolysis Cells through In Situ A-Site Deficiencies and Surface Carbonate Deposition Induced by Lithium Cation Doping and Exsolution.

Solid oxide electrolysis cells (SOECs) hold enormous potential for efficient conversion of CO2 to CO at low cost and high reaction kinetics. The identification of active cathodes is highly desirable to promote the SOEC's performance. This study explores a lithium-doped perovskite La0.6- x Lix Sr0.4 Co0.7 Mn0.3 O3-δ (x = 0, 0.025 0.05, and 0.10) material with in situ generated A-site deficiency and surface carbonate as SOEC cathodes for CO2 reduction. The experimental results indicate that the SOEC with the La0.55 Li0.05 Sr0.4 Co0.7 Mn0.3 O3-δ cathode exhibits a current density of 0.991 A cm-2 at 1.5V/800°C, which is an improvement of ≈30% over the pristine sample. Furthermore, SOECs based on the proposed cathode demonstrate excellent stability over 300 h for pure CO2 electrolysis. The addition of lithium with high basicity, low valance, and small radius, coupled with A-site deficiency, promotes the formation of oxygen vacancy and modifies the electronic structure of active sites, thus enhancing CO2 adsorption, dissociation process, and CO desorption steps as corroborated by the experimental analysis and the density functional theory calculation. It is further confirmed that Li-ion migration to the cathode surface forms carbonate and consequently provides the perovskite cathode with an impressive anti-carbon deposition capability, as well as electrolysis activity.

Stepwise induced passivation film formation on the surface of spherical hard carbons enabling ultra-stable potassium ions storage

Potassium-ion storage devices are seen as a form of prospective substitute for large-scale electrochemical energy storage because of the low cost and the fast charge transport in electrolytes. However, the rosy scenario is compromised by developing ultra-stable electrode materials to ensure long-term cycling performance. Herein, with sucrose as the carbon source, we construct two carbon materials, namely hard carbon spherules (HCS) and active hard carbons (AHCS), as anode and cathode materials, respectively, to fabricate high-performance potassium-ion hybrid capacitors (PIHC). Benefiting from the advantageous ionic conductivity and the comparatively stable passivation film, HCS bonding with sodium alginate delivers superior rate performance and high pseudocapacitive proportion. In situ electrochemical impedance spectroscopy and distribution of relaxation time analysis combined with ex situ scanning electron microscope images reveal that the formation of solid electrolyte interface on the surface of the HCS during the initial discharge can be explained as a gradually forming process. As expected, the HCS//AHCS PIHC device delivers a high energy density of 116 Wh kg−1 at a power density of 218 W kg−1 and exhibits an ultra-stable lifespan over 20000 cycles. This study provides a worthy reference for the value-added utilization of biomass in innovative potassium-based energy storage technology.

Current Trends in Spent Portable Lithium Battery Recycling.

This paper provides an overview of the current state of the field in spent portable lithium battery recycling at both the research and industrial scales. The possibilities of spent portable lithium battery processing involving pre-treatment (manual dismantling, discharging, thermal and mechanical-physical pre-treatment), pyrometallurgical processes (smelting, roasting), hydrometallurgical processes (leaching followed by recovery of metals from the leachates) and a combination of the above are described. The main metal-bearing component of interest is the active mass or cathode active material that is released and concentrated by mechanical-physical pre-treatment procedures. The metals of interest contained in the active mass include cobalt, lithium, manganese and nickel. In addition to these metals, aluminum, iron and other non-metallic materials, especially carbon, can also be obtained from the spent portable lithium batteries. The work describes a detailed analysis of the current state of research on spent lithium battery recycling. The paper presents the conditions, procedures, advantages and disadvantages of the techniques being developed. Moreover, a summary of existing industrial plants that are focused on spent lithium battery recycling is included in this paper.