13 research outputs found
Ultra-high-rate pseudocapacitive energy storage in two-dimensional transition metal carbides
The use of fast surface redox storage (pseudocapacitive) mechanisms can enable devices that store much more energy than electrical double-layer capacitors (EDLCs) and, unlike batteries, can do so quite rapidly. Yet, few pseudocapacitive transition metal oxides can provide a high power capability due to their low intrinsic electronic and ionic conductivity. Here we demonstrate that two-dimensional transition metal carbides (MXenes) can operate at rates exceeding those of conventional EDLCs, but still provide higher volumetric and areal capacitance than carbon, electrically conducting polymers or transition metal oxides.We applied two distinct designs for MXene electrode architectures with improved ion accessibility to redox-active sites. A macroporous Ti3C2Tx MXene film delivered up to 210 F g-1 at scan rates of 10Vs-1, surpassing the best carbon supercapacitors known. In contrast, we show that MXene hydrogels are able to deliver volumetric capacitance of 1,500 F cm-3 reaching the previously unmatched volumetric performance of RuO2
BOOSTING MXENE CAPACITY BY SELF-OXIDATION IN AIR ATMOSPHERE FOR WATER-IN-SALT ELECTROLYTE BASED SUPERCAPACITOR
The use of Ti3C2Tx (MXene) electrodes for energy storage applications is gaining momentum
in recent years. The ability of the MXene to host a large variety of mono and multivalent ions
regardless of their charge or ionic radius makes it an attractive anode for aqueous and non-aqueous
batteries and supercapacitor devices
Electrochemical Quartz Crystal Microbalance with Dissipation Real-Time Hydrodynamic Spectroscopy of Porous Solids in Contact with Liquids
Using multiharmonic
electrochemical quartz crystal microbalance
with dissipation (EQCM-D) monitoring, a new method of characterization
of porous solids in contact with liquids has been developed. The dynamic
gravimetric information on the growing, dissolving, or stationary
stored solid deposits is supplemented by their precise in-operando
porous structure characterization on a mesoscopic scale. We present
a very powerful method of quartz-crystal admittance modeling of hydrodynamic
solid–liquid interactions in order to extract the porous structure
parameters of solids during their formation in real time, using different
deposition modes. The unique hydrodynamic spectroscopic characterization
of electrolytic and rf-sputtered solid Cu coatings that we use for
our “proof of concept” provides a new strategy for probing
various electrochemically active thin and thick solid deposits, thereby
offering inexpensive, noninvasive, and highly efficient quantitative
control over their properties. A broad spectrum of applications of
our method is proposed, from various metal electroplating and finishing
technologies to deeper insight into dynamic build-up and subsequent
development of solid-electrolyte interfaces in the operation of Li-battery
electrodes, as well as monitoring hydrodynamic consequences of metal
corrosion, and growth of biomass coatings (biofouling) on different
solid surfaces in seawater
Understanding the effects of transition metal intercalation on electronic and electrochemical properties of Ti3C2Tx MXene
MXenes are 2D transition metal carbides, nitrides, and/or carbonitrides, capable of intercalation by various cations through chemical or electrochemical means. Previous research has primarily focused on intercalating alkaline and alkaline earth cations, such as Li+, K+, Na+, Mg2+ or alkylammonium cations, into Ti3C2Tx MXenes. However, the impact of intercalated transition metal (TM) ions on the electronic and electrochemical properties of MXenes remains largely unexplored. In this study, we investigated the effects of pre-intercalated Cu ions on Ti3C2Tx MXenes and vice versa to gain a comprehensive understanding of how the electronic and electrochemical properties of both intercalated TM ion and MXene host are altered. Using in-situ X-ray absorption spectroscopy (XAS), we reveal changes in the oxidation states of intercalated Cu ions and Ti atoms during charging and their corresponding role in charge storage mechanisms. Our findings show that electronic coupling between Ti3C2Tx and Cu ions results in modified electrochemical and electronic properties compared to pristine Ti3C2Tx. These insights lay the foundation for the rational design and utilization of TM ion intercalants to tailor the properties of MXenes for various electrochemical systems and beyond
What About Manganese? Toward Rocking Chair Aqueous Mn-Ion Batteries
The emerging interest in aqueous rechargeable batteries has led to significant progress in the development of next-generation electrolytes and electrode materials enabling reversible and stable insertion of various multivalent ions into the electrode's bulk. Yet, despite its abundance, high salt solubility, and small ionic radius, the use of manganese ions for energy storage purposes has not received sufficient attention. Herein, we present the use of Mo6S8 (Chevrel phase) as an anode for Mn2+ insertion. By careful optimization of the electrolyte solution, high-capacity values exceeding 90 mAh/g and long-term stability (more than 1500 cycles) have been obtained. Based on in situ XRD analysis, the charging mechanism and the associated structural changes occurring during Mn2+ insertion have been carefully studied. Finally, we demonstrate for the first time a rocking chair aqueous Mn-ion battery comprising a Chevrel anode and NiHCF cathode.ISSN:2380-819
Titanium carbide MXene shows an electrochemical anomaly in water-in-salt electrolytes
Identifying and understanding charge storage mechanisms is important for advancing energy storage, especially when new materials and electrolytes are explored. Well-separated peaks in cyclic voltammograms (CVs) are considered key indicators of diffusion-controlled electrochemical processes with distinct Faradic charge transfer. Herein, we report on an electrochemical system with separated CV peaks, accompanied by surface-controlled partial charge transfer, in 2D Ti3C2Tx MXene in water-in-salt electrolytes. The process involves the insertion/desertion of desolvation-free cations, leading to an abrupt change of the interlayer spacing between MXene sheets. This unusual behavior increases charge storage at positive potentials, thereby increasing the amount of energy stored. This also demonstrates new opportunities for the development of high-rate aqueous energy storage devices and electrochemical actuators using safe and inexpensive aqueous electrolytes
Engineering Robust Battery Interphases with Dilute Fluorinated Cations
Controlling solid electrolyte interphase (SEI) in batteries is crucial for their efficient cycling. Herein, we demonstrate an approach to enable robust battery performance that does not rely on high fractions of fluorinated species in electrolytes, thus substantially decreasing the environmental footprint and cost of high-energy batteries. In this approach, we use very low fractions of readily reducible fluorinated cations in electrolyte (~0.1 wt.%) and employ electrostatic attraction to generate a substantial population of these cations at the anode surface. As a result, we can form a robust fluorine-rich SEI that allows for dendrite-free deposition of dense Li and stable cycling of Li metal
full cells with high-voltage cathodes. Our approach represents a general strategy for delivering desired chemical species to battery anodes through electrostatic attraction while using minute amounts of additive
Quantification of porosity in extensively nanoporous thin films in contact with gases and liquids
Manipulating Oxygen Vacancies to Spur Ion Kinetics in V2O5 Structures for Superior Aqueous Zinc-Ion Batteries
Vanadium-based intercalation materials have attracted considerable attention for aqueous zinc-ion batteries (ZIBs). However, the sluggish interlaminar diffusion of zinc ions due to the strong electrostatic interaction, severely restricts their practical application. Herein, oxygen vacancy-enriched V2O5 structures (Zn0.125V2O5·0.95H2O nanoflowers, Ov-ZVO) with expanded interlamellar space and excellent structural stability are prepared for superior ZIBs. In situ electron paramagnetic resonance (EPR) and X-ray diffraction (XRD) characterization revealed that numerous oxygen vacancies are generated at a relatively low reaction temperature because of partially escaped lattice water. In situ spectroscopy and density functional theory (DFT) calculations unraveled that the existence of oxygen vacancies lowered Zn2+ diffusion barriers in Ov-ZVO and weakened the interaction between Zn and O atoms, thus contributing to excellent electrochemical performance. The Zn||Ov-ZVO battery displayed a remarkable capacity of 402 mAh g−1 at 0.1 A g−1 and impressive energy output of 193 Wh kg−1 at 2673 W kg−1. As a proof of concept, the Zn||Ov-ZVO pouch cell can reach a high capacity of 350 mAh g−1 at 0.5 A g−1, demonstrating its enormous potential for practical application. This study provides fundamental insights into formation of oxygen-vacant nanostructures and generated oxygen vacancies improving electrochemical performance, directing new pathways toward defect-functionalized advanced materials