Zn Cathode Research Articles

Performance comparison of electro-polymerized polypyrrole and polyaniline as cathodes for iodine redox reaction in zinc-iodine batteries

At present, Zinc-iodine (Zn//I) batteries have attracted much attention due to their high safety and capacity. However, how to suppress the shuttling of polyiodide ions generated during charging processes is still a tricky problem. Herein, polyaniline (PANI) and polypyrrole (PPy) are electro-polymerized on carbon felt (CF) by constant current and used as cathodes for zinc-iodine (Zn//I) batteries. Electrochemical tests of the PANI@CF and PPy@CF electrodes prove that the PANI@CF electrode has a higher capacity, a stronger ability to suppress shuttling of polyiodine ions, and more excellent cyclic stability than the PPy@CF electrode. According to the material characterizations, the differences of both electrodes in electrochemical performances are mainly caused by the microstructures of PANI and PPy in both electrodes. The PANI has a micro-nano porous structure while the PPy is very dense. The porous PANI not only has more channels for the infiltration of electrolyte, but also can provide more active adsorption sites to minimize the shuttling of polyiodide ions to anode, ensuring the excellent performances of the PANI@CF. However, dense PPy seriously hinders the electrolyte diffusion and triggers the formation of an insulating dense iodine film, bringing poor performances to the PPy@CF. Ultimately, the PANI@CF electrodes achieves the most specific capacity of 235.9 mAh g−1 at 0.35 A g−1 (∼1.7 C) and performs out long cycle life with high stability (75.7% capacitiy rention after 10,000 cycles) at 3.5 A g−1 (∼17 C) in Zn//I battery, manifesting the porous PANI@CF electrode is a greatly promising candidate as cathode for Zn//I batteries in actual application.

Regulating Interfacial Ion Migration via Wool Keratin Mediated Biogel Electrolyte toward Robust Flexible Zn-Ion Batteries.

Aqueous Zn-ion batteries (ZIBs) have emerged as a promising energy supply for next-generation wearable electronics, yet they are still impeded by the notorious growth of zinc dendrite and uncontrollable side reaction. While the rational design of electrolyte composition or separator decoration can effectively restrain zinc dendrite growth, synchronously regulating the interfacial electrochemical performance by tackling the physical delamination venture between electrode and electrolyte remains a major obstacle for high-performance wearable aqueous ZIB. Herein, a category of hybrid biogel electrolyte containing carrageenan and wool keratin (CWK) is put forward to regulate the interfacial electrochemistry in aqueous ZIB. Systematic electrochemical kinetics analyses and ex situ scanning electrochemical microscopy (SECM) characterizations achieve comprehensive understanding of the keratin enhanced interfacial Zn2+ redox reaction. Thanks to the keratin triggered selective ion permeability, the as-designed CWK hybrid biogel electrolyte manifests a promoted Zn2+ transference number and excellent reversibility of Zn plating/stripping and outstanding Zn utilization (average Coulombic efficiency ≈98%). More impressively, the CWK hybrid biogel electrolyte also demonstrates cathode side-reaction depression and strengthened interfacial adhesion while assembled into a quasi-solid-state flexible ZIB. This work offers a strategy to synchronously solve concurrent challenges for both of Zn anode and cathode toward realistic wearable aqueous ZIB.

Highly dispersed Bi clusters for efficient rechargeable Zn−CO2 batteries

Zn−CO2 batteries hold great promise for carbon-neutral and electricity generation simultaneously, whereas the main obstacle is the development of electrocatalysts with high activity and durability towards CO2 reduction reaction (CRR). Herein, we design atomically dispersed Bi clusters supported on hollow carbon spheres (BiC/HCS) for effectively reducing CO2 to formate, which shows the highest faradaic efficiency of 97 ± 2% at − 0.6 V vs RHE, being comparable to the previously best reported values of Bi-based materials. Experimental and theoretical analyses reveal that the atomic-level Bix clusters not only enable high CO2 adsorption but also stabilize the key *HCOO intermediate with a low free energy barrier. Further, an assembled rechargeable Zn−CO2 battery with BiC/HCS as the cathode achieves a peak power density of 7.2 ± 0.5 mW cm−2 as well as an impressive rechargeability of 200 cycles. This work provides a promising alternative for CO2 utilization and energy storage by Zn−CO2 batteries.Graphical AbstractBi clusters anchored on hollow carbon spheres have developed as an excellent cathode for Zn−CO2 battery. The catalyst presents a maximal formate faradaic efficiency of 97 ± 2% at − 0.6 V vs RHE as well as good durability. The assembled Zn−CO2 battery achieves a peak power density of 7.2 ± 0.5 mW cm−2 and energy efficiency of 68.9% (@ 3 mA cm−2), and a more than 200 cycle rechargeability. [Display omitted]

In-site coupling of NiFe layered double hydroxides with N-doped carbon nanosheets on carbon cloth as integrated cathode for rechargeable Zn–air batteries

Exploring low-cost, high catalytic activity and high durability dual-function catalysts is critical for rechargeable Zn–air batteries to promote the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) processes.

Aqueous Zn‐based rechargeable batteries: Recent progress and future perspectives

AbstractBenefiting from the advantageous features of high safety, abundant reserves, low cost, and high energy density, aqueous Zn‐based rechargeable batteries (AZBs) have received extensive attention as promising candidates for energy storage. To achieve high‐performance AZBs with high reversibility and energy density, great efforts have been devoted to overcoming their drawbacks by focusing on the modification of electrode materials and electrolytes. Based on different cathode materials and aqueous electrolytes, the development of aqueous AZBs with different redox mechanisms are discussed in this review, including insertion/extraction chemistries (e.g., Zn2+, alkali metal ion, H+, NH4+, and so forth) dissolution/deposition reactions (e.g., MnO2/Mn2+), redox couples in flow batteries (e.g., I3−/3I−, Br2/Br−, and so forth), oxygen electrochemistry (e.g., O2/OH−, O2/O22−), and carbon dioxide electrochemistry (e.g., CO2/CO, CO2/HCOOH). In particular, the basic reaction mechanisms, issues with the Zn electrode, aqueous electrolytes, and cathode materials as well as their design strategies are systematically reviewed. Finally, the remaining challenges faced by AZBs are summarized, and perspectives for further investigations are proposed.

Atomic Fe-N4 /C in Flexible Carbon Fiber Membrane as Binder-Free Air Cathode for Zn-Air Batteries with Stable Cycling over 1000 h.

Noble-metal-free, durable, and high-efficiency electrocatalysts for oxygen reduction and evolution reaction (ORR/OER) are vital for rechargeable Zn-air batteries (ZABs). Herein, a flexible and free-standing carbon fiber membrane immobilized with atomically dispersed Fe-N4 /C catalysts (Fe/SNCFs-NH3 ) is synthesized and used as air cathode for ZABs. The intertwined fibers with hierarchical nanopores facilitate the gas transportation, electrolyte infiltration and electron transfer. The large specific surface area exposes a high concentration of Fe-N4 /C sites embedded in the carbon matrix. Modulation of local atomic configurations by sulfur doping in Fe/SNCFs-NH3 catalyst leads to excellent ORR and enhanced OER activities. The as-synthesized Fe/SNCFs-NH3 catalyst demonstrates a positive half-wave potential of 0.89V and a small Tafel slope of 70.82mV dec-1 , outperforming the commercial Pt/C (0.86V/94.74mV dec-1 ) and most reported M-Nx /C (M = Fe, Co, Ni) catalysts. Experimental characterizations and theoretical calculations uncover the crucial role of S doping in regulating ORR and OER activities. The liquid-state ZABs with Fe/SNCFs-NH3 catalyst as air cathode deliver a large peak power density of 255.84mW cm-2 and long-term cycle durability over 1000 h. Solid-state ZAB shows stable cycling at various flat/bent/flat states, demonstrating great prospects in flexible electronic device applications.

Electrochemical Behaviors of Consumable Ti2CO@Al2O3 Anode for Ti Extraction by USTB Process

USTB technology is widely considered as a low-cost and environmentally-friendly method for titanium extraction from a consumable TiCxOy anode. It is expected to directly prepare TiCxOy by selective carbothermal reduction of titanium ores, not pure TiO2. However, impurities in titanium ores, particularly Al2O3, may affect the electrochemical dissolution of TiCxOy and Ti extraction. In this work, the effects of Al2O3 impurity on the preparation and dissolution behaviors of Ti2CO are studied. It is found that the existence form of Al2O3 is not changed during carbothermal reduction. With the increase of Al2O3 content, the conductivity of Ti2CO anode slightly decreases from 143.1 to 131.6 S cm−1 and the anodic polarization curves of Ti2CO@Al2O3 shifts to the positive direction due to the increase of dissolution resistances. Al2O3 in Ti2CO@Al2O3 anode will drop into molten salts to form anode slime during USTB process. On both liquid Zn and solid nickel cathodes, Ti is electrodeposited, which is not affected by Al2O3 impurity. Therefore, it is confirmed that typical Al2O3 impurity has no obvious effect on the electrochemical dissolution of Ti2CO anode and Ti extraction. The advanced USTB process is expectedly developed by the selective carbothermal reduction of titanium ores to prepare Ti2CO anode.

Bifunctional Hydrated Gel Electrolyte for Long‐Cycling Zn‐Ion Battery with NASICON‐Type Cathode

AbstractAqueous Zn‐ion batteries are promising and safe energy storage technologies. However, current aqueous electrolyte Zn‐ion battery technology is hindered by undesirable reactions between the electrolyte and electrodes, which can lead to Zn dendrite growth, gas evolution, and cathode degradation. In this study, a hydrated gel electrolyte (HGE) that combines adiponitrile (ADN) and Zn(ClO4)2·6H2O in a polymeric framework is created. ADN is found to stabilize the interface between the electrolyte and anode/cathode, enabling smooth Zn stripping/plating and reducing parasitic reactions. The HGE is simple to fabricate, inexpensive, safe, and flexible. Zn/HGE/Zn symmetrical cells can cycle more than 1000 h at 0.5 mA cm−2 and 2000 h at 0.2 mA cm−2 without short‐circuiting, indicating effective suppression of Zn dendrites. Moreover, with a NASICON‐type Sr‐doped Na3V2(PO4)3 (SNVP) cathode, a Zn/HGE/SNVP full cell can be cycled over 8000 times at 10 C while retaining a high capacity of 90 mAh g−1.

Solving multifunctionality in the carbon footprint assessment of primary metals production: Comparison of different approaches

Multifunctionality is a recurring issue in the life cycle assessment (LCA) of primary metals production, as one metal is often co-produced with other metals. In this context, this study aims at i) reviewing the approaches actually implemented in the literature for solving multifunctionality in the context of the LCA of primary metals co-production; ii) comparing the currently existing multifunctionality-solving approaches as defined by the ISO hierarchy, considering the carbon footprint assessment (in a life-cycle perspective) of copper (Cu), zinc (Zn), lead (Pb) and silver (Ag) co-production through the implementation of on-site “mine-to-metal” technologies at pilot scale in a Spanish mine; iii) discussing the implications associated with the use of these different approaches in the context of primary metals co-production and the extent to which they may affect the assessment of the environmental performances of metals. Overall, the allocation approach stands for the first option for solving multifunctionality in the LCA of metals co-production based on the review of 27 studies; despite the ISO hierarchy recommends the use of allocation as last resort. Based on a representative set of primary data drawn from on-site trials at a pilot scale, the potential climate change impacts induced by the co-production of 1 ton Cu and 6 tons Zn cathodes along with 2.65 tons Pb and 0.045 ton Ag precipitates are calculated to amount to 90,324 kg CO2-eq in a life cycle perspective. Depending on the multifunctionality-solving approach, the apportionment of these impacts to each co-product shows significant discrepancies. The implementation of partial subdivision combined with market prices allocation attributes most (80%) of the impacts to Zn and Ag. The use of allocation approaches attribute the largest share of impacts to Zn (62%) and Pb (27%) when considering a mass criterion; while the impacts are primarily attributed to Ag (respectively 48% and 45%) and Zn (respectively 30% and 33%) when considering economic criteria (respectively market prices and production costs). In terms of representativeness, the use of partial subdivision shall be considered as a more representative approach for solving multifunctionality than the mere application of allocation. Moreover, the results obtained through the application of economic allocation are considered more consistent than those obtained by mass allocation in this case study; while the use of production costs may be seen as an alternative for overcoming the limits associated with market prices. Finally, the use of system expansion shows that the recovery of Zn, Pb and Ag in addition to Cu potentially avoids 25% of the total climate change impacts. The approach implemented to solve multifunctionality largely influences the estimated impacts of each co-produced metal, subsequently with potential large implications for the footprints of products and sectors using these metals. The way multifunctionality is solved shall therefore be transparently reported in the scope of LCA studies, with privileging subdivision whenever possible.

Electrochemical reduction of nitrate using divided electrolytic cell by proton exchange membrane

The electrochemical reduction of nitrate using a divided electrolytic cell in combination with Zn cathode and (Pt)/Ti anode reduced the high concentrations of nitrate (1,000 mg NO3-N/L). A proton exchange membrane (Nafion-117) was used to increase the nitrate reduction efficiency by preventing the re-oxidation of nitrite produced during the reduction process. The current density and anolyte concentration, considered as parameters, were tested to assess the electrochemical reduction of nitrate. The reduction of nitrate shortened the electrolysis time in proportion to the current density, and the time for 90% removal was 5 h at 5 mA/cm2, 3 h at 10 mA/cm2, and 1.8 h at 20 mA/cm2. The yields of ammonia were approximately 50%-55% of the initial nitrate-nitrogen concentration regardless of the current density and was insignificantly related to the anolyte concentration.

ZnOTe Compounds Grown by DC-Magnetron Co-Sputtering

ZnOTe compounds were grown by DC magnetron cosputtering from pure Tellurium (Te) and Zinc (Zn) cathodes in O2/Ar atmosphere. The applied power on the Zn target was constant equal to 100 W, while the one applied on the Te target took two values, i.e., 5 W and 10 W. Thus, two sample series were obtained in which the variable parameter was the distance from the Te targets to the substrate. Sample compositions were determined by Rutherford Backscattering Spectroscopy (RBS) experiments. Structural analysis was done using X-Ray diffraction (XRD) spectrometry and the growth of the hexagonal w-ZnO phase was identified in the XRD spectra. RBS results showed high bulk homogeneity of the samples forming ZnOTe alloys, with variable Te molar fraction (MF) ranging from 0.48–0.6% and from 1.9–3.1% for the sample series obtained at 5 W and 10 W, respectively. The results reflect great differences between the two sample series, particularly from the structural and optical point of view. These experiments point to the possibility of Te doping ZnO with the permanence of intrinsic defects, as well as the possibility of the formation of other Te solid phases when its content increases. The results and appreciable variations in the band gap transitions were detected from Photoluminescence (PL) measurements.

Polydopamine-coated bimetallic ZIF derivatives as an air cathode for acidic Zn-air batteries with super-high potential.

NC@Co-HPNC is synthesized, which exhibits a superior ORR/OER performance in acid/base solution. Hence, acid-base dual-electrolyte-based Zn-air batteries using NC@Co-HPNC reveal a long cycling life and a super-high voltage (2.1 V).

Electrolysis of rich Titanium Slag in Molten CaCl2 with a Liquid Zn Cathode

Electrolysis of rich Titanium Slag in Molten CaCl2 with a Liquid Zn Cathode

New Insight on Open‐Structured Sodium Vanadium Oxide as High‐Capacity and Long Life Cathode for Zn–Ion Storage: Structure, Electrochemistry, and First‐Principles Calculation

AbstractHerein, the promising properties of open‐structured NaV3O8 as a cathode material for Zn‐ion batteries (ZIBs) are investigated. First‐principles calculations predict the insertion of Zn2+ (0.74 Å) in NaV3O8 with an interlayer distance of ≈7 Å, enabling delivery of a high discharge capacity of 353 mAh g−1 at 70 mA g−1 (0.2 C) for 300 cycles in the operating window of 0.3−1.5 V in 1 m Zn(CF3SO3)2 aqueous solution. Operando synchrotron X‐ray diffraction, X‐ray absorption near edge structure spectroscopy, and first‐principles calculations validate the insertion of Zn2+ into the NaV3O8 structure within the operation range. Moreover, operando synchrotron X‐ray diffraction and operando Raman spectroscopy reveal the formation of layered zinc hydroxytriflate (Zn5(OH)8(CF3SO3)2∙xH2O) as a side reaction below 0.8 V on discharge (reduction) and its dissolution into the electrolyte above 0.8 V on charge (oxidation). The formation of the Zn hydroxytriflate interfacial layer increases the charge‐transfer activation energy from 15.5 to 48 kJ mol−1, leading to kinetics fade below 0.8 V. The findings reveal the charge‐storage mechanism for NaV3O8, which may also be applicable to other vanadate cathodes, providing new insights for the investigation and design of ZIBs.

Antibacterial properties of metal and PDMS surfaces under weak electric fields

The adhesion of several species of bacteria on two parallel rectangular electrodes under weak electric fields was studied. The electrodes were based on native metal or PDMS coated Cu. After 2 h of contact at a voltage of 0.2 to 1 V without any current, the Zn cathode showed a bacterial repellent effect with a difference in bacterial adhesion of about 1.5 to 2 log CFU/cm2 on the anode. Al electrodes were inactive due to their passivation by the alumina layer. At 1 V, both Zn and Al exhibited more than 80% mortality of suspended bacteria. The Cu electrodes showed a very high bactericidal effect even at 0 V, and the bacterial adhesion on its surface was too weak to see a difference between the two electrodes. A similar study carried out on PDMS surfaces, covering Cu electrodes, revealed that a difference of 1 log CFU/cm2 of bacterial adhesion between the cathode and anode surfaces can be obtained by applying a voltage ranging from 10 to 30 V. This cathodic repellent effect was specific to staphylococcus species, suggesting that in the presence of a PDMS coating, the electrostatic forces on the surface are too low to be the main factor governing bacterial adhesion.

LiMn<sub>1.5</sub>Ni<sub>0.25</sub>Fe<sub>0.2</sub>M<sub>0.05</sub>O<sub>4</sub> Nanoparticles as a Cathode Material for Rechargeable Li-Ion Batteries

New series of spinel LiNi0.25Fe0.2Mˊ0.05Mn1.5O4 (Mˊ = Cu, Mg or Zn) cathode materials have been purposefully tailored using sol-gel auto-combustion method at low annealing temperature ~ 700°C for 3 h. The XRD analysis showed that all substituted (LNFMO-Mˊ) samples are comported with the main structure of undoped (LNFMO) with crystalline disordered spinel Fd-3m structure. TEM images revealed the octahedron-shape like morphology for the particles and the LNFMO-Zn sample has the widest particle size distribution. EIS spectra evidenced that a typical one semicircle (LNFMO-Mg) was revealed for each cell, suggesting the absence of ionic conductivity contribution. The values of charge transfer resistance (Rct) were equal to 9.3, 6.7, 6.0 and 4.4 kΩ for LNFMO, LNFMO-Cu, LNFMO-Mg indicating that the Zn-doped sample has the fastest kinetic diffusion rate and lowest activation energy of conduction.

Rapid Electrodeposition of Ti on a Liquid Zn Cathode from a Consumable Casting TiC0.5O0.5 Anode

The USTB process with a consumable TiCxOy anode is considered as a low-cost and eco-friendly method for Ti production. However, the dendritic Ti products have disadvantages of high oxygen and salt contents. Here, a liquid Zn cathode was proposed to prepare Ti–Zn alloys from a casting TiC0.5O0.5 anode via a one-step electrolysis process in a NaCl–KCl molten salt. Cyclic voltammetry and square-wave voltammetry were used to investigate the electrochemical dissolution of Ti ions from a consumable TiC0.5O0.5 anode and subsequent reduction behavior on cathode. The results indicate that the reduction potential of Ti on a liquid Zn cathode is more positive than that on a solid W cathode. Ti2+ from the casting TiC0.5O0.5 anode was one-step reduced to Ti on the liquid Zn cathode. A quasi-reversible process was confirmed via diffusion-controlled mass transfer, and the diffusion coefficient of Ti2+ toward the liquid Zn electrode was 4.35 × 10−5 cm−2 s−1. The concentration of Ti2+ in molten salt is more stable during electrolysis with a liquid Zn cathode. Ti–Zn alloys were successfully prepared at a current density of 0.3 A cm−2 using a casting TiC0.5O0.5 anode and a liquid Zn cathode. Metallic Zn was confirmed to be a promising liquid cathode to prepare Ti–Zn alloys via the USTB process.

Bifunctional N-CoSe2/3D-MXene as Highly Efficient and Durable Cathode for Rechargeable Zn–Air Battery

Rechargeable Zn–air battery is a promising alternative to the widely used lithium–ion battery. Its practical use, however, is hindered by low power density, unsatisfactory energy efficiency, poor durability, and unstable voltage output. Here, we demonstrate a bifunctional catalyst for oxygen evolution and oxygen reduction reactions based on 3D MXene coupled with nitrogen-doped cobalt selenide nanocrystals (N-CoSe2/3D Ti3C2Tx). Combining experimental characterizations and density functional theory (DFT), the excellent performance is ascribed to enhanced intrinsic activity of CoSe2 due to electron transfer from MXene, N doping which lowers the reaction energy barriers, and 3D MXene architecture which provides large specific surface area, high porosity, and good conductivity. Moreover, Zn–air battery equipped with the developed N-CoSe2/3D MXene as the air cathode exhibits better power/energy densities and long-lasting cycling life (over 500 cycles) compared with that of mixed Pt/C and RuO2.

Enhanced electrodeposition and separation of metallic Cr from soluble K2CrO4 on a liquid Zn cathode

Abstract Carbon contamination and the formation of low-valence oxides limit the preparation of refractory metals by molten salt electrolysis. In this paper, a liquid Zn cathode is adopted for the electrochemical reduction of soluble K2CrO4 to metallic Cr in CaCl2-KCl molten salt. It is found that CrO42- can be directly electrochemically reduced to Cr via a six-electron-transfer step and low-valence Cr oxides is hardly produced. The reduction rate is obviously increased from 16.7 mgCr h−1 cm−2 on the solid Mo cathode to 58.7 mgCr h−1 cm−2 on liquid Zn cathode. The electrodeposited Cr is distributed in liquid Zn cathode. Carbon contamination is effectively avoided due to the negligible solubility of carbon in the liquid Zn cathode. Furthermore, Cr can be effectively separated and enriched to the bottom of liquid Zn under super-gravity field, realizing the efficient acquisition of metallic Cr and recycling of liquid Zn. The method herein provides a promising route for the preparation of refractory metals with high-purity by molten salt electrolysis.

Uranium recovery via electrochemical deposition with a liquid zinc cathode followed by electrochemical oxidation of rare earth metals

Uranium recovery with electrochemical deposition followed by selective oxidation of rare earth (RE) metals was examined to confirm the feasibility of liquid Zn cathode and figure out the behavior of RE dissolution. U was used as a surrogate for U/transuranic (TRU) elements in this study. About 1.6 wt% UCl3, 2.9 wt% NdCl3 and 3.1 wt% CeCl3 was dissolved into the LiCl-KCl eutectic, and the U, Nd, and Ce was co-deposited into a liquid Zn cathode. About 3.3 g of U/RE alloy was successfully consolidated by subsequent removal of the Zn with the distillation. U was segregated and agglomerated with each other in a matrix alloy consisting of Nd and Ce, confirming the co-deposition of RE along with U. The U/RE alloy was electrochemically oxidized to remove the RE, applying a constant voltage of −1.7 V (vs. Ag/AgCl) at the anode. Approximately 2.2 g of final product in a granular shape was ultimately obtained after the subsequent removal of residual salts. Characterization revealed that the concentration of U was larger than that of the REs, even though a large amount of REs still remained, confirming the selective dissolution of REs. The results suggest a new method, i.e., electrochemical deposition followed by selective oxidation of RE, to recover U/TRU from the LiCl-KCl salt using a liquid Zn cathode.