Papers by Robert Kostecki
Research Square (Research Square), Aug 2, 2023
Layered Li-rich transition metal oxides (LRTMO) are one of the most promising cathode candidates ... more Layered Li-rich transition metal oxides (LRTMO) are one of the most promising cathode candidates for high energy density lithium batteries due to the redox contributions from transition metal (TM) cations and oxygen (O) anion. However, their practical application is hindered by gradual capacity fading and voltage decay. Although oxygen loss and phase transformation have been widely recognized as primary factors for these drawbacks, the structural deterioration and chemical rearrangement of LRTMO during battery operations, and the kinetic and thermodynamic evolution, remain unclear. Herein, we comprehensively investigate the morphological, structural, and oxidation state evolutions from the individual atoms to secondary particles. By means of nano-to micro-scale characterizations, distinct structural changing pathways associated with different intra-particle heterogeneous reactions are identi ed. Substantial O-defects are formed through the particle by slow electrochemical activation, accompanied with oxygen release triggering progressive phase transformation on surface and formation of nano-voids in bulk. The ultra-fast heterogeneous Li-(de)intercalation often leads to O-distortion dominated lattice displacement, TM-ions dissolution, and Li-sites variation. These inhomogeneous and irreversible structural changes are responsible for rst-cycle Coulombic ine ciency, and ongoing particle cracking and expansion in the following cycles.
Electrochimica Acta, May 1, 2007
13 C-carbon black substituted composite LiNi 0.8 Co 0.15 Al 0.05 O 2 cathodes were tested in mode... more 13 C-carbon black substituted composite LiNi 0.8 Co 0.15 Al 0.05 O 2 cathodes were tested in model electrochemical cells to monitor qualitatively and quantitatively carbon additive(s) distribution changes within tested cells and establish possible links with other detrimental phenomena. Raman qualitative and semi-quantitative analysis of 13 C in the cell components was carried out to trace the possible carbon rearrangement/movement in the cell. Small amounts of cathode carbon additives were found trapped in the separator, at the surface of Li-foil anode, in the electrolyte. The structure of the carried away carbon particles was highly amorphous unlike the original 12 C graphite and 13 C carbon black additives. The role of the carbon additive, the mechanism of carbon retreat in composite cathodes and its correlation with the increase of the cathode interfacial charge-transfer impedance, which accounts for the observed cell power and capacity loss is investigated and discussed.
Carbon, Apr 1, 2010
ABSTRACT Thin layers of graphitic carbon were produced from solid organic precursors by a one-ste... more ABSTRACT Thin layers of graphitic carbon were produced from solid organic precursors by a one-step microwave plasma chemical vapor deposition method. Low-pressure Ar-plasma and strong electromagnetic radiation led to the rapid evaporation and pyrolysis of organic precursors at relatively low temperatures, yielding uniform films of nanometer-sized graphitized carbon particles. The structure and morphology of the carbon films were examined using scanning electron microscopy, transmission electron microscopy, and Raman spectroscopy. A direct correlation between electrical conductivity of graphitic thin films and their structure was established.
Journal of Power Sources, Nov 1, 2007
A novel synthesis method of thin-film composite Sn/C anodes for lithium batteries is reported. Th... more A novel synthesis method of thin-film composite Sn/C anodes for lithium batteries is reported. Thin layers of graphitic carbon decorated with uniformly distributed Sn nanoparticles were synthesized from a solid organic precursor Sn(IV) tert-butoxide by a one-step microwave plasma chemical vapor deposition (MPCVD). The thin-film Sn/C electrodes were electrochemically tested in lithium half cells and produced a reversible capacity of 423 and 297 mAh g −1 at C/25 and 5C discharge rates, respectively. A long-term cycling of the Sn/C nanocomposite anodes showed 40% capacity loss after 500 cycles at 1C rate.
Meeting abstracts, 2005
not Available.
Electrochemistry Communications, Jul 1, 2007
Composite carbon-platinum thin-films of nano-crystalline graphitic carbon decorated with uniforml... more Composite carbon-platinum thin-films of nano-crystalline graphitic carbon decorated with uniformly-dispersed 2-4 nm Pt nano-particles have been synthesized from a solid organic precursor by a one-step microwave plasma chemical vapor deposition (MPCVD). The fast Ar-plasma discharge and the presence of microwave radiation accelerate the formation of sites suitable for in situ heterogeneous nucleation, and consequently, the fine dispersion of metal in the carbonaceous matrix. The electrochemical response of the 2 lm C/Pt thin-film electrode displays electrochemical activity, which is attributed to the high ca. 18 m 2 /g effective surface area of Pt nano-particles.
Meeting abstracts, 2010
not Available.
The Journal of Physical Chemistry C
Table of Contents (TOC) Graphic TOC sentence: The SEI on Si-anodes reduces the decomposition of t... more Table of Contents (TOC) Graphic TOC sentence: The SEI on Si-anodes reduces the decomposition of the organic solvents, whereas the LiPF 6 salt continues to decompose upon cycling
Journal of Physics: Energy, 2021
The expectation to progress towards Terawatts production by solar technologies requires continuou... more The expectation to progress towards Terawatts production by solar technologies requires continuous development of new materials to improve efficiency and lower the cost of devices beyond what is currently available at industrial level. At the same time, the turnaround time to make the investment worthwhile is progressively shrinking. Whereas traditional absorbers have developed in a timeframe spanning decades, there is an expectation that emerging materials will be converted into industrially relevant reality in a much shorter timeframe. Thus, it becomes necessary to develop new approaches and techniques that could accelerate decision-making steps on whether further research on a material is worth pursuing or not. In this review, we will provide an overview of the photoemission characterization methods and theoretical approaches that have been developed in the past decades to accelerate the transfer of emerging solar absorbers into efficient devices.
Nature, 2020
Rechargeable lithium-ion batteries with high energy density that can be safely charged and discha... more Rechargeable lithium-ion batteries with high energy density that can be safely charged and discharged at high rates are desirable for electrified transportation and other applications 1-3. However, the sub-optimal intercalation potentials of current anodes result in a trade-off between energy density, power and safety. Here we report that disordered rock salt 4,5 Li 3+x V 2 O 5 can be used as a fast-charging anode that can reversibly cycle two lithium ions at an average voltage of about 0.6 volts versus a Li/Li + reference electrode. The increased potential compared to graphite 6,7 reduces the likelihood of lithium metal plating if proper charging controls are used, alleviating a major safety concern (short-circuiting related to Li dendrite growth). In addition, a lithium-ion battery with a disordered rock salt Li 3 V 2 O 5 anode yields a cell voltage much higher than does a battery using a commercial fast-charging lithium titanate anode or other intercalation anode candidates (Li 3 VO 4 and LiV 0.5 Ti 0.5 S 2) 8,9. Further, disordered rock salt Li 3 V 2 O 5 can perform over 1,000 charge-discharge cycles with negligible capacity decay and exhibits exceptional rate capability, delivering over 40 per cent of its capacity in 20 seconds. We attribute the low voltage and high rate capability of disordered rock salt Li 3 V 2 O 5 to a redistributive lithium intercalation mechanism with low energy barriers revealed via ab initio calculations. This low-potential, high-rate intercalation reaction can be used to identify other metal oxide anodes for fast-charging, long-life lithium-ion batteries. Lithium-rich disordered rock salt (DRS) oxides are known to be promising cathode materials, with fast lithium (Li) diffusion that is due to a percolating network of octahedron-tetrahedron-octahedron pathways 4,10. However, although the formation of DRS such as Li 3 MoO 4 and Li 5 W 2 O 7 oxides during electrochemical reactions is known 11,12 , there have been no investigations of further insertion of Li into DRS oxides to form potential anode materials. Delmas showed that three Li ions could intercalate into V 2 O 5 to form Li 3 V 2 O 5 when the discharge cutoff voltage is extended to 1.9 V, with the proposed structure to be a rock salt phase with crystallographic formula Li 0.6 V 0.4 O (refs. 13,14). Extended Data Fig. 1a, b presents the voltage curve and phase transformations of V 2 O 5 during its first lithiation down to 0.01 V. The results at above 1.5 V are consistent with previous reports 13. Surprisingly, the lithiation plateau below 1 V indicates that Li + could further insert into ω-Li 3 V 2 O 5. As shown in Fig. 1a, DRS-Li 3 V 2 O 5 can be cycled reversibly between 0.01 V and 2 V at a current density of 0.1 A g −1 with a specific capacity of 266 mA h g −1. In addition, the average working potential of 0.6 V is between those of lithium titanate and graphite, ideal for fast charging and high-energy-density applications. To fully resolve the structure of Li 3 V 2 O 5 , we employed joint Rietveld refinement of neutron diffraction and X-ray diffraction (XRD) patterns to quantify site occupancies in the unit cell 15. The results shown in Extended Data Fig. 1c, d and Extended Data Table 1 are consistent with a DRS structure with space group Fm3m. The cubic lattice parameter of the DRS-Li 3 V 2 O 5 is 4.095(1) Å. The O ions fully occupy the 4a sites, whereas the octahedral 4b sites are almost fully filled by Li and V ions, with 52% and 40% fractional occupancies, respectively. A few Li ions occupy 4% of the tetrahedral (8c) interstitial sites. Therefore, the structure of DRS-Li 3 V 2 O 5 can be expressed as [□ 9.6 Li 0.4 ] 8c [□ 0.4 Li 2.6 V 2 ] 4b [O 5 ] 4a , which has plenty of vacant tetrahedral sites for hosting more Li ions. In situ XRD was conducted while charging and discharging the electrode between 0.1 V and 2 V. The diffraction patterns (Extended Data Fig. 2c), show that the (220) peak of the rock salt phase persists throughout the entire electrochemical process. The (220) peak shifts to lower angles and broadens during Li insertion into DRS-Li 3 V 2 O 5. The changes are completely reversible upon Li removal during charge. Similar trends were observed in neutron diffraction as shown in Fig. 1c. On the basis
Nature Communications, 2020
Herein, we present a scalable approach for the synthesis of a hydrogen-bonded organic–inorganic f... more Herein, we present a scalable approach for the synthesis of a hydrogen-bonded organic–inorganic framework via coordination-driven supramolecular chemistry, for efficient remediation of trace heavy metal ions from water. In particular, using copper as our model ion of interest and inspired by nature’s use of histidine residues within the active sites of various copper binding proteins, we design a framework featuring pendant imidazole rings and copper-chelating salicylaldoxime, known as zinc imidazole salicylaldoxime supramolecule. This material is water-stable and exhibits unprecedented adsorption kinetics, up to 50 times faster than state-of-the-art materials for selective copper ion capture from water. Furthermore, selective copper removal is achieved using this material in a pH range that was proven ineffective with previously reported metal–organic frameworks. Molecular dynamics simulations show that this supramolecule can reversibly breathe water through lattice expansion and c...
This work focuses on the mechanisms of interfacial processes at the surface of amorphous silicon ... more This work focuses on the mechanisms of interfacial processes at the surface of amorphous silicon thin-film electrodes in organic carbonate electrolytes to unveil the origins of the inherent non-passivating behavior of silicon anodes in Li-ion batteries. Attenuated total reflection Fouriertransform infrared spectroscopy (ATR-FTIR), X-ray absorption spectroscopy (XAS), and infrared near-field scanning optical microscopy (IR aNSOM) were used to investigate the formation, evolution and chemical composition of the surface layer formed on Si upon cycling. We found that the chemical composition and thickness of the solid/electrolyte interphase layer (SEI) continuously change during the charging/discharging cycles. This SEI layer "breathing" effect is directly related
ACS Materials Letters, 2019
In this work, we show that the well-known lithium-ion anode material, Li 4 Ti 5 O 12 , exhibits e... more In this work, we show that the well-known lithium-ion anode material, Li 4 Ti 5 O 12 , exhibits exceptionally high initial capacity of 310 mAh g −1 when it is discharged to 0.01 V. It maintains a reversible capacity of 230 mAh g −1 , far exceeding the "theoretical" capacity of 175 mAh g −1 when this anode is lithiated to the composition Li 7 Ti 5 O 12. Neutron diffraction analyses identify that additional Li reversibly enters into the Li 7 Ti 5 O 12 to form Li 8 Ti 5 O 12. density functional theory (DFT) calculations reveal the average potentials of the Li 4 Ti 5 O 12 to Li 7 Ti 5 O 12 step and the Li 7 Ti 5 O 12 to Li 8 Ti 5 O 12 step are 1.57 and 0.19 V, respectively, which are in excellent agreement with experimental results. Transmission electron microscopy (TEM) studies confirm that the irreversible capacity of Li 4 Ti 5 O 12 during its first cycle originates from the formation of a solid electrolyte interface (SEI) layer. This work clarifies the fundamental lithiation mechanism of the Li 4 Ti 5 O 12 , when lithiated to 0.01 V vs Li.
Meeting abstracts, 2007
not Available.
Meeting abstracts, 2011
not Available.
Energy & Environmental Science
The oxidation process of lattice oxygen in Li-rich cathodes is dynamically compatible with that o... more The oxidation process of lattice oxygen in Li-rich cathodes is dynamically compatible with that of TMs. Fast delithiation at high current densities can lead to local structural transformation and limited Li+ diffusion rates.
Illumination of a voltage-biased plasmonic Ag cathode during CO 2 reduction results in a suppress... more Illumination of a voltage-biased plasmonic Ag cathode during CO 2 reduction results in a suppression of the H 2 evolution reaction while enhancing CO 2 reduction. This effect has been shown to be photonic rather than thermal, but the exact plasmonic mechanism is unknown. Here, we conduct an in situ ATR-SEIRAS study of a sputtered thin film Ag cathode on a Ge ATR crystal in CO 2-saturated 0.1 M KHCO 3 over a range of potentials 1 in both dark and illuminated (365 nm, 125 mW cm −2) conditions to elucidate the nature of this plasmonic enhancement. We find that the onset potential of CO 2 reduction to adsorbed CO on the Ag surface is-0.25 V RHE and is identical in the light and the dark. As the production of gaseous CO is detected in the light near this onset potential but is not observed in the dark until-0.5 V RHE we conclude that the light must be assisting the desorption of CO from the surface. Furthermore, the HCO − 3 wavenumber and peak area increase immediately upon illumination, precluding a thermal effect. We propose that the enhanced local electric field that results from the LSPR is strengthening the HCO − 3 bond, further increasing the local pH. This would account for the decrease of H 2 formation and increase of CO 2 reduction products in the light. Experimental Methods Cathode Fabrication To prepare the cathode, a 60°Ge ATR crystal (Pike Technologies, 013-3132) was polished three times with subsequently smaller diameter alumina suspensions of 1.0 µm, 0.3 µm, and 0.05 µm (Buehler, 40-10081, 40-10082, and 40-10083) using microcloth pads (BASi, MF-1040). The crystal surface was cleaned with water and acetone using lint-free wipes and dried with compressed nitrogen. The crystal was placed in a Faraday cage and subjected to air plasma for 8 minutes on high power (Harrick Plasma, PDC-002-CE). A 40 nm film of Ag was deposited on the crystal surface in a custom-built sputtering tool with an argon (Ar) pressure of 50 µbar, deposition rate of 0.01455 nm s −1 , and substrate rotation of 15°s −1. After deposition, the resistance across the surface of the cathode was typically 4-8 Ω, as measured by a multimeter. A schematic of the cathode is shown in Figure S2.
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Papers by Robert Kostecki