Critical roles of multiphase coexistence in boosting piezo-catalytic activity of BaTiO3-based piezoelectric ceramics

Recently, piezocatalysis induced by perovskite ferroelectric ceramics has widely been favored as a possible fascinating strategy for water remediation due to its low cost, simplicity and feasibility. Herein, a strategy of three-ferroelectric-phase coexistence is proposed to boost the piezocatalytic performance of BaTiO3-based ceramics by introducing Ca(Sn0.5Zr0.5)O3 into BaTiO3. The piezocatalysts of (1-x)BaTiO3–xCa(Sn0.5Zr0.5)O3 ceramics were prepared by a high-temperature solid-phase method. The phase structure, microstructure, electrical properties and catalytic performance of ceramics were comprehensively studied. As x increases from 0 to 0.10, the ceramics undergo the phase evolution from single tetragonal phase to multiphase (coexistence of rhombic, orthorhombic, and tetragonal phases). It is found that the phase structure of the ceramics plays a critical role in enhancing the piezocatalytic activity. The pure BaTiO3 exhibits the tetragonal (T) phase with few spontaneous polarization directions and high polarization rotational energy barrier, resulting in poor catalytic performance and low piezoelectricity. With the coexistence of rhombic (R), orthorhombic (O) and tetragonal (T) phases, the ceramic with x = 0.1 exhibits the increased spontaneous polarization directions and low polarization rotational energy barrier, leading to excellent catalytic performance and high piezoelectricity. Especially, for the ceramics with x = 0.10, the degradation rates of rhodamine B (RhB), methylene blue (MB) and methyl orange (MO) under ultrasonication reach 97 %, 93 % and 73 %, respectively. In addition, the influencing factors of piezocatalytic degradation of RhB and the catalytic mechanism are investigated. This work proposes an environmentally friendly piezoelectric material for improving the water environment and a strategy for improving the catalytic activity of BaTiO3-based lead-free piezoelectric materials

Heterogeneous engineering and carbon confinement strategy to synergistically boost the sodium storage performance of transition metal selenides

Transition metal selenides (TMSs) stand out as a promising anode material for sodium-ion batteries (SIBs) owing to their natural resources and exceptional sodium storage capacity. Despite these advantages, their practical application faces challenges, such as poor electronic conductivity, sluggish reaction kinetics and severe agglomeration during electrochemical reactions, hindering their effective utilization. Herein, the dual-carbon-confined CoSe /FeSe @NC@C nanocubes with heterogeneous structure are synthesized using ZIF-67 as the template by ion exchange, resorcin-formaldehyde (RF) coating, and subsequent in situ carbonization and selenidation. The N-doped porous carbon promotes rapid electrolyte penetration and minimizes the agglomeration of active materials during charging and discharging, while the RF-derived carbon framework reduces the cycling stress and keeps the integrity of the material structure. More importantly, the built-in electric field at the heterogeneous boundary layer drives electron redistribution, optimizing the electronic structure and enhancing the reaction kinetics of the anode material. Based on this, the nanocubes of CoSe /FeSe @NC@C exhibits superb sodium storage performance, delivering a high discharge capacity of 512.6 mA h g at 0.5 A g after 150 cycles and giving a discharge capacity of 298.2 mA h g at 10 A g with a CE close to 100.0 % even after 1000 cycles. This study proposes a viable method to synthesize advanced anodes for SIBs by a synergy effect of heterogeneous interfacial engineering and a carbon confinement strategy. [Abstract copyright: Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.

Multilevel spatial confinement of transition metal selenides porous microcubes for efficient and stable potassium storage

Recently, potassium-ion batteries (PIBs) have been considered as one of the most promising energy storage systems; however, the slow kinetics and large volume variation induced by the large radius of potassium ions (K+) during chemical reactions lead to inferior structural stability and weak electrochemical activity for most potassium storage anodes. Herein, a multilevel space confinement strategy is proposed for developing zinc-cobalt bimetallic selenide (ZnSe/Co0.85Se@NC@C@rGO) as high-efficient anodes for PIBs by in-situ carbonizing and subsequently selenizing the resorcinol-formaldehyde (RF)-coated zeolitic imidazolate framework-8/zeolitic imidazolate framework-67 (ZIF-8/ZIF-67) encapsulated into 2D graphene. The highly porous carbon microcubes derived from ZIF-8/ZIF-67 and carbon shell arising from RF provide rich channels for ion/electron transfer, present a rigid skeleton to ensure the structural stability, offer space for accommodating the volume change, and minimize the agglomeration of active material during the insertion/extraction of large-radius K+. In addition, the three-dimensional (3D) carbon network composed of graphene and RF-derived carbon-coated microcubes accelerates the electron/ion transfer rate and improves the electrochemical reaction kinetics of the material. As a result, the as-synthesized ZnSe/Co0.85Se@NC@C@rGO as the anode of PIBs possesses the excellent rate capability of 203.9 mA h g−1 at 5 A g−1 and brilliant long-term cycling performance of 234 mA h g−1 after 2,000 cycles at 2 A g−1. Ex-situ X-ray diffraction (Ex-situ XRD) diffraction reveals that the intercalation/de-intercalation of K+ proceeds through the conversion-alloying reaction. The proposed strategy based on the spatial confinement engineering is highly effective to construct high-performance anodes for PIBs

Optimizing interplanar spacing, oxygen vacancies and micromorphology via lithium-ion pre-insertion into ammonium vanadate nanosheets for advanced cathodes in aqueous zinc-ion batteries

Ammonium vanadates, featuring an N─H···O hydrogen bond network structure between NH4+ and V─O layers, have become popular cathode materials for aqueous zinc-ion batteries (AZIBs). Their appeal lies in their multi-electron transfer, high specific capacity, and facile synthesis. However, a major drawback arises as Zn2+ ions tend to form bonds with electronegative oxygen atoms between V─O layers during cycling, leading to irreversible structural collapse. Herein, Li+ pre-insertion into the intermediate layer of NH4V4O10 is proposed to enhance the electrochemical activity of ammonium vanadate cathodes for AZIBs, which extends the interlayer distance of NH4V4O10 to 9.8 Å and offers large interlaminar channels for Zn2+ (de)intercalation. Moreover, Li+ intercalation weakens the crystallinity, transforms the micromorphology from non-nanostructured strips to ultrathin nanosheets, and increases the level of oxygen defects, thus exposing more active sites for ion and electron transport, facilitating electrolyte penetration, and improving electrochemical kinetics of electrode. In addition, the introduction of Li+ significantly reduces the bandgap by 0.18 eV, enhancing electron transfer in redox reactions. Leveraging these unique advantages, the Li+ pre-intercalated NH4V4O10 cathode exhibits a high reversible capacity of 486.1 mAh g−1 at 0.5 A g−1 and an impressive capacity retention rate of 72% after 5,000 cycles at 5 A g−1

Modulating solvated structure of Zn2+ and inducing surface crystallography by a simple organic molecule with abundant polar functional groups to synergistically stabilize zinc metal anodes for long-life aqueous zinc-ion batteries

Aqueous zinc-ion batteries (AZIBs) have attracted significant attention owing to their inherent security, low cost, abundant zinc (Zn) resources and high energy density. Nevertheless, the growth of zinc dendrites and side reactions on the surface of Zn anodes during repeatedly plating/stripping shorten the cycle life of AZIBs. Herein, a simple organic molecule with abundant polar functional groups, 2,2,2-trifluoroether formate (TF), has been proposed as a high-efficient additive in the ZnSO4 electrolyte to suppress the growth of Zn dendrites and side reaction during cycling. It is found that TF molecules can infiltrate the solvated sheath layer of the hydrated Zn2+ to reduce the number of highly chemically active H2O molecules owing to their strong binding energy with Zn2+. Simultaneously, TF molecules can preferentially adsorb onto the Zn surface, guiding the uniform deposition of Zn2+ along the crystalline surface of Zn(0 0 2). This dual action significantly inhibits the formation of Zn dendrites and side reactions, thus greatly extending the cycling life of the batteries. Accordingly, the Zn//Cu asymmetric cell with 2 % TF exhibits stable cycling for more than 3,800 cycles, achieving an excellent average Columbic efficiency (CE) of 99.81 % at 2 mA cm−2/1 mAh cm−2. Meanwhile, the Zn||Zn symmetric cell with 2 % TF demonstrates a superlong cycle life exceeding 3,800 h and 2,400 h at 2 mA cm−2/1 mAh cm−2 and 5 mA cm−2/2.5 mAh cm−2, respectively. Simultaneously, the Zn//VO2 full cell with 2 % TF possesses high initial capacity (276.8 mAh/g) and capacity retention (72.5 %) at 5 A/g after 500 cycles. This investigation provides new insights into stabilizing Zn metal anodes for AZIBs through the co-regulation of Zn2+ solvated structure and surface crystallography

Coexistence of three ferroelectric phases and enhanced piezoelectric properties in BaTiO3–CaHfO3 lead-free ceramics

Perovskite ferroelectrics possess the fascinating piezoelectric properties near a morphotropic phase boundary, attributing to a low energy barrier that the results in structural instability and easy polarization rotation. In this work, a new lead-free system of (1-x)BaTiO3-xCaHfO3 was designed, and characterized by a coexistence of ferroelectric rhombohedral-orthorhombic-tetragonal (R-O-T) phases. With the increase amount of CaHfO3 (x), a stable coexistence region of three ferroelectric phases (R-O-T) exists at 0.06 ≤ x ≤ 0.08. Both large piezoelectric coefficient (d33∼400 pC/N), inverse piezoelectric coefficient (d33*∼547 pm/V) and planar electromechanical coupling factor (kp∼58.2%) can be achieved for the composition with x = 0.08 near the coexistence of three ferroelectric phases. Our results show that the materials with the composition located at a region where the three ferroelectric R-O-T phases coexist would have the lowest energy barrier and thus greatly promote the polarization rotation, resulting in a strong piezoelectric response

Core-shell nanostructured MnO2@Co9S8 arrays for high-performance supercapacitors

Manganese dioxide (MnO2) with large theoretical capacity, low cost and rich reserves has been considered as one of the most promising advanced electrode materials of supercapacitors, but the shortage of electrochemical active sites and the inherent defects of electrical conductivity hinder its widespread application in high-performance supercapacitors. Herein, the hierarchical core-shell nanostructure has been rationally designed by coating highly electrically conductive Co9S8 on MnO2 arrays on Ni foam (MnO2@Co9S8/NF) using a simple solution-based method. The prepared MnO2@Co9S8/NF exhibits a high specific capacitance of 643.3 C g−1 at 3 mA cm−2, which is 3.4 and 10.1 times higher than the Co3O4@MnO2 and pristine MnO2 electrodes, respectively. Moreover, the asymmetric supercapacitor (ASC) with MnO2@Co9S8 composite electrode provides a high areal capacitance of 1540 mC cm−2 and a maximum energy density of 346.5 μW h cm−2 (35 Wh kg−1) at the power density of 2376 μW cm−2 (240 W kg−1). Importantly, the excellent cycling life with a capacitance retention of 97.5% after 36,000 cycles indicates the good stability of the core-shell structure of the composite electrode. These superior electrochemical properties of current materials are comparable to the most advanced MnO2-based electrodes for supercapacitors

Excellent rate capability and cycling stability in Li+-conductive Li2SnO3-coated LiNi0.5Mn1.5O4 cathode materials for lithium-ion batteries

High-voltage LiNi0.5Mn1.5O4 is a promising cathode candidate for lithium-ion batteries (LIBs) due to its considerable energy density and power density, but the material generally undergoes serious capacity fading caused by side reactions between the active material and organic electrolyte. In this work, Li+-conductive Li2SnO3 was coated on the surface of LiNi0.5Mn1.5O4 to protect the cathode against the attack of HF, mitigate the dissolution of Mn ions during cycling and improve the Li+ diffusion coefficient of the materials. Remarkable improvement in cycling stability and rate performance has been achieved in Li2SnO3-coated LiNi0.5Mn1.5O4. The 1.0 wt% Li2SnO3-coated LiNi0.5Mn1.5O4 cathode exhibits excellent cycling stability with a capacity retention of 88.2% after 150 cycles at 0.1 C and rate capability at high discharge rates of 5 C and 10 C, presenting discharge capacities of 119.5 and 112.2 mAh g−1, respectively. In particular, a significant improvement in cycling stability at 55 °C is obtained after the coating of 1.0 wt% Li2SnO3, giving a capacity retention of 86.8% after 150 cycles at 1 C and 55 °C. The present study provides a significant insight into the effective protection of Li-conductive coating materials for a high-voltage LiNi0.5Mn1.5O4 cathode material

Interface engineering of a hollow core-shell sulfur-doped Co2P@Ni2P heterojunction for efficient charge storage of hybrid supercapacitors

Transition metal phosphides (TMPs) are widely used as supercapacitor energy storage materials due to their abundant valence and high theoretical capacity, but their poor electrical conductivity and low active material utilization lead to low actual capacity and slow kinetics. Herein, we demonstrate the excellent electrochemical properties of sulfur-doped Co2P@Ni2P heterojunction materials prepared using a combination of hydrothermal, ion-exchange and low-temperature annealing approaches. For sulfur-doped Co2P@Ni2P, hollow core-shell microstructures increase the number of electroactive sites and provides a shortcut for electron transport, while sulfur doping promotes the transfer and rearrangement of interfacial charge from Co2P to Ni2P, optimizing the redox ability of the active component. In addition, the S doping and the highly electrochemically active nickel-cobalt phosphide synergistically accelerate the charge transfer, which leads to fast reaction kinetics. Therefore, the obtained S-Co2P@Ni2P exhibits an optimal specific capacity of 1200Cg-1 at 1Ag-1 and excellent rate performance. Furthermore, when combined with activated carbon (AC) for hybrid supercapacitor (HSC), the S-Co2P@Ni2P//AC device shows an excellent energy density of 41.5Whkg-1 and a high-capacity retention of 93% after 15,000 cycles. This work provides a novel approach for the exploration of high-performance and stable phosphorus-based battery-like supercapacitor materials