The development of novel materials is essential for the next generation of electric vehicles and portable devices. Tin oxide (SnO2), with its relatively high theoretical capacity, has been considered as a promising anode material for applications in energy storage devices. However, the SnO2 anode material suffers from poor conductivity and huge volume expansion during charge/discharge cycles. In this study, we evaluated an approach to control the conductivity and volume change of SnO2 through a controllable and effective method by confining different percentages of SnO2 nanoparticles into carbon nanotubes (CNTs). The binder-free confined SnO2 in CNT composite was deposited via an electrostatic spray deposition technique. The morphology of the synthesized and deposited composite was evaluated by scanning electron microscopy and high-resolution transmission electron spectroscopy. The binder-free 20% confined SnO2 in CNT anode delivered a high reversible capacity of 770.6 mAh g−1. The specific capacity of the anode increased to 1069.7 mAh g−1 after 200 cycles, owing to the electrochemical milling effect. The delivered specific capacity after 200 cycles shows that developed novel anode material is suitable for lithium-ion batteries (LIBs).

Lead‐based relaxor ferroelectrics are characterized by outstanding piezoelectric and dielectric properties, making them useful in a wide range of applications. Despite the numerous models proposed to describe the relation between their nanoscale polar structure and the large properties, the multiple contributions to these properties are not yet revealed. Here, by combining atomistic and mesoscopic‐scale structural analyses with macroscopic piezoelectric and dielectric measurements across the (100– x )Pb(Mg 1/3 Nb 2/3 )O 3 – x PbTiO 3 (PMN– x PT) phase diagram, a direct link is established between the multiscale structure and the large nonlinear macroscopic response observed in the monoclinic PMN‐ x PT compositions. The approach reveals a previously unrecognized softening effect, which is common to Pb‐based relaxor ferroelectrics and arises from the displacements of low‐angle nanodomain walls, facilitated by the nanoscale polar character and lattice strain disorder. This comprehensive comparative study points to the multiple, distinct mechanisms that are responsible for the large piezoelectric response in relaxor ferroelectrics.

Electrocaloric fatigue, i.e., the degradation of the electrocaloric temperature change of an active material under continuous electric-field cycling, has not been addressed in detail so far, despite the elevated electric fields expected for EC cooling devices. Here, we investigate the electrocaloric fatigue mechanism of a prototype relaxor material, i.e., Pb(Mg1/3Nb2/3)O3, by directly measuring its temperature response under device-relevant electric-field conditions. We show that after a critical number of field cycles the temperature of the sample begins to increase dramatically, leading to a significant degradation of the cooling properties. The degradation of cooling properties is investigated using a combination of multiscale characterization techniques, revealing that the origin of the degradation is the increased grain boundary conductance caused by an unexpected electric-field-induced phase transformation to a ferroelectric phase. We further show that this transformation and thus the fatigue can be regulated by careful control of the temperature and electric-field conditions. By revealing a previously unexplored fatigue mechanism, this study provides the first guidelines for the integration of high-performance relaxors into cooling devices.

Electrochemical capacitors or “supercapacitors” essentially bridge the gap between traditional capacitors and rechargeable batteries with their high specific power and moderate energy densities. Commercial supercapacitors typically comprise activated carbon (AC) electrodes, which rely on electrostatic double layer charge storage mechanisms. Pseudocapacitors, on the other hand, benefit from surface redox reactions which lend them superior capacitance than their double layer counterparts. Conducting polymers and transitional metal oxides (TMOs) account for pseudocapacitors in general and among TMOs, manganese oxides have widely been investigated owing to their high specific capacitances, low cost, and environmental benignity. In this work, porous manganese oxide (MnO x ) thin films were synthesized via electrostatic spray deposition (ESD) and evaluated as pseudocapacitive electrode materials in aqueous media. Very interestingly, the gravimetric specific capacitance of the ESD based MnO x electrodes underwent a marked enhancement upon electrochemical cycling, from 72Fg -1 to 225Fg -1 , with a concomitant improvement in kinetics and conductivity. The change in capacitance and resistivity is attributed to a partial electrochemical phase transformation from the spinel type hausmannite Mn 3 O 4 to the conducting layered birnessite MnO 2 . Furthermore, the films were able to retain 88.4% of the maximal capacitance after 1000 cycles. Upon verifying the viability of the manganese oxide films for pseudocapacitive applications, the thin films were integrated onto carbon micro-pillars created via carbon microelectromechanical systems (C-MEMS) for examining their application as potential microelectrode candidates. In a symmetric two-electrode cell setup, the MnO x /C-MEMS microelectrodes were able to deliver specific capacitances as high as 0.055 Fcm -2 and stack capacitances as high as 7.4Fcm -3 , with maximal stack energy and power densities of 0.51 mWhcm -3 and 28.3 mWcm -3 , respectively. The excellent areal capacitance of the MnO x -MEs is attributed to the pseudocapacitive MnO x as well as the three-dimensional architectural framework provided by the carbon micropillars.

In this study, porous manganese oxide (MnOx) thin films were synthesized via electrostatic spray deposition (ESD) and evaluated as pseudocapacitive electrode materials in neutral aqueous media. Very interestingly, the gravimetric specific capacitance of the ESD-based electrodes underwent a marked enhancement upon electrochemical cycling, from 72 F∙g−1 to 225 F∙g−1, with a concomitant improvement in kinetics and conductivity. The change in capacitance and resistivity is attributed to a partial electrochemical phase transformation from the spinel-type hausmannite Mn3O4 to the conducting layered birnessite MnO2. Furthermore, the films were able to retain 88.4% of the maximal capacitance after 1000 cycles. Upon verifying the viability of the manganese oxide films for pseudocapacitive applications, the thin films were integrated onto carbon micro-pillars created via carbon microelectromechanical systems (C-MEMS) for examining their application as potential microelectrode candidates. In a symmetric two-electrode cell setup, the MnOx/C-MEMS microelectrodes were able to deliver specific capacitances as high as 0.055 F∙cm−2 and stack capacitances as high as 7.4 F·cm−3, with maximal stack energy and power densities of 0.51 mWh·cm−3 and 28.3 mW·cm−3, respectively. The excellent areal capacitance of the MnOx-MEs is attributed to the pseudocapacitive MnOx as well as the three-dimensional architectural framework provided by the carbon micro-pillars.

The development of high capacity rechargeable lithium-ion batteries is crucial given the insatiable energy demands that come with the rapidly-developing technological landscape. One of the major areas of research focus is the development of high performance advanced electrochemical materials. Transition metal oxides (MxOy) are one of the most widely studied classes of materials given their high theoretical capacities. However, such materials often exhibit large volumetric expansion during the cycling processes due to their lithium storage mechanisms, in addition to poor electronic conductivities. One of the methods to resolve these issues is the confinement of nano-scale particulates of various transition metal oxides with the interest of improving their charge storage capability, rate capability, and the longevity of their performance with cycling. Confinement of metal oxide nanoparticles (e.g. SnO2) within carbon nanotubes has been shown to improve the performance of these anode materials versus unconfined metal oxides. The increased surface area, enhanced interfacial charge storage and enhanced electrical conductivity contribute to improved electrochemical performance. Here, electrostatic spray deposition (ESD) is used to create a thin film of the anode materials of interest for subsequent property testing of the assembled LIBs. This presentation will give the details of the techniques used to produce the desired anode materials and their electrochemical characterization as LIB anodes.

Piezoelectric and ferroelectric materials are useful as the active element in non-destructive monitoring devices for high-radiation areas. Here, crystallographic structural refinement (i.e., the Rietveld method) is used to quantify the type and extent of structural changes in PbZr0.5Ti0.5O3 after exposure to a 1 MeV equivalent neutron fluence of 1.7 × 1015 neutrons/cm2. The results show a measurable decrease in the occupancy of Pb and O due to irradiation, with O vacancies in the tetragonal phase being created preferentially on one of the two O sites. The results demonstrate a method by which the effects of radiation on crystallographic structure may be investigated.