| 1. |
- Finegan, Donal P., et al.
(författare)
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Spatial dynamics of lithiation and lithium plating during high-rate operation of graphite electrodes
- 2020
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Ingår i: Energy and Environmental Science. - : Royal Society of Chemistry (RSC). - 1754-5692 .- 1754-5706. ; 13:8, s. 2570-2584
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Tidskriftsartikel (refereegranskat)abstract
- The principal inhibitor of fast charging lithium ion cells is the graphite negative electrode, where favorable conditions for lithium plating occur at high charge rates, causing accelerated degradation and safety concerns. The local response of graphite, both at the electrode and particle level, when exposed to fast charging conditions of around 6C is not well understood. Consequently, the conditions that lead to the onset of lithium plating, as well as the local dynamics of lithium plating and stripping, have also remained elusive. Here, we use high-speed (100 Hz) pencil-beam X-ray diffraction to repeatedly raster along the depth of a 101 µm thick graphite electrode in 3 µm steps during fast (up to 6C) charge and discharge conditions. Consecutive depth profiles from separator to current collector were each captured in 0.5 seconds, giving an unprecedented spatial and temporal description of the state of the electrode and graphite's staging dynamics during high rate conditions. The electrode is preferentially activated near the separator, and the non-uniformity increases with rate and is influenced by free-energy barriers between graphite's lithiation stages. The onset of lithium plating and stripping was quantified, occurring only within the first 15 µm from the separator. The presence of lithium plating changed the behavior of the underlying graphite, such as causing co-existence of LiC6 and graphite in the fully discharged state. Finally, the staging behavior of graphite at different rates was quantified, revealing a high dependency on rate and drastic hysteresis between lithiation and delithiation.
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| 2. |
- Li, Zhaojun, 1989, et al.
(författare)
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9.0% power conversion efficiency from ternary all-polymer solar cells
- 2017
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Ingår i: Energy and Environmental Science. - : Royal Society of Chemistry (RSC). - 1754-5692 .- 1754-5706. ; 10:10, s. 2212-2221
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Tidskriftsartikel (refereegranskat)abstract
- Integration of a third component into a single-junction polymer solar cell (PSC) is regarded as an attractive strategy to enhance the performance of PSCs. Although binary all-polymer solar cells (all-PSCs) have recently emerged with compelling power conversion efficiencies (PCEs), the PCEs of ternary all-PSCs still lag behind those of the state-of-the-art binary all-PSCs, and the advantages of ternary systems are not fully exploited. In this work, we realize high-performance ternary all-PSCs with record-breaking PCEs of 9% and high fill factors (FF) of over 0.7 for both conventional and inverted devices. The improved photovoltaic performance benefits from the synergistic effects of extended absorption, more efficient charge generation, optimal polymer orientations and suppressed recombination losses compared to the binary all-PSCs, as evidenced by a set of experimental techniques. The results provide new insights for developing high-performance ternary all-PSCs by choosing appropriate donor and acceptor polymers to overcome limitations in absorption, by affording good miscibility, and by benefiting from charge and energy transfer mechanisms for efficient charge generation.
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| 3. |
- Patil, Sunil, et al.
(författare)
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Cisplatin-induced elongation of Shewanella oneidensis MR-1 cells improves microbe-electrode interactions for use in microbial fuel cells
- 2013
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Ingår i: Energy & Environmental Science. - : Royal Society of Chemistry (RSC). - 1754-5706 .- 1754-5692. ; 6:9, s. 2626-2630
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Tidskriftsartikel (refereegranskat)abstract
- Here, we present an unusual approach of modifying the growth pattern of electroactive bacteria for improving their communication with electrodes. Cells of a known exoelectrogen, Shewanella oneidensis MR-1, were treated with cisplatin, a drug that inhibits cell division but forces the cells to grow longer resulting in a characteristic elongated growth. Such elongated cells showed up to a 5-fold improvement in current densities compared to normal, untreated cells.
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| 4. |
- Valverde-Chavez, David A., et al.
(författare)
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Intrinsic femtosecond charge generation dynamics in single crystal CH3NH3PbI3
- 2015
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Ingår i: Energy & Environmental Science. - : Royal Society of Chemistry (RSC). - 1754-5706 .- 1754-5692. ; 8:12, s. 3700-3707
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Tidskriftsartikel (refereegranskat)abstract
- Hybrid metal-organic perovskite solar cells have astounded the solar cell community with their rapid rise in efficiency while maintaining low-cost fabrication. The intrinsic material photophysics related to the generation of free charges, their dynamics and efficiency, however, remains to be understood. As fabrication techniques improve, larger crystal grain sizes have been shown to be a critical factor for improving both the optical and transport properties of the hybrid metal halide perovskites. In this work, we use pulses of multi-THz frequency light in the ultra-broadband 1-30 THz (4-125 meV) range to observe the ac conductivity in large single crystal CH3NH3PbI3. Our spectra reveal the ultrafast dynamics and efficiencies of free charge creation and extremely high charge carrier mobility as high as 500800 cm(2) V-1 s(-1). While quasi-equilibrium analysis of efficiencies through the Saha equation suggests a binding energy on the order of 49 meV, an observed reflectance feature appearing at high pump fluence occurs at 12 meV and is consistent with an orbital transition of the exciton, indicating a much lower Rydberg energy of 17 meV at room temperature. The signature of the exciton is found to vanish on a 1 ps time scale commensurate with the appearance of mobile carriers, consistent with thermal dissociation of the exciton to the continuum in the room temperature tetragonal phase.
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| 5. |
- Yu, Shuang, et al.
(författare)
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Imidazole additives in 2D halide perovskites : impacts of -CN versus -CH3 substituents reveal the mediation of crystal growth by phase buffering
- 2022
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Ingår i: Energy and Environmental Science. - : Royal Society of Chemistry (RSC). - 1754-5692 .- 1754-5706. ; 15:8, s. 3321-3330
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Tidskriftsartikel (refereegranskat)abstract
- The unique sandwich structure and favorable crystallization kinetics have endowed two-dimensional (2D) halide perovskites with excellent ambient stability and facile film formation compared to those of their three-dimensional counterparts. However, the heterogeneous crystallization of multiple n-value phases during solution-casting of 2D perovskite thin films results in random and disordered crystalline alignment in conjunction with numerous lattice defects, all of which ultimately impair the device performance. Herein we demonstrate that highly ordered lattice arrangements in 2D lead halide perovskites, exemplified as a paradigm phenylethylamine (PEA) spacer, can be achieved using the 4,5-dicyanoimidazole (DCI) additive without any post-treatment. Electrostatic potential distribution mapping and X-ray photoelectron spectroscopy collectively confirm the Lewis acid-base interaction between -CN− units in DCI and Pb2+, which is conducive to homogeneous nucleation during perovskite crystallization. A sequence of in situ grazing-incident wide-angle X-ray scattering and high-resolution transmission electron microscopy characterization unravel the epitaxial growth of multi-phases that gradually buffer the internal lattice strain and consequently regulate the lattice orientation, which markedly leads to a reduction of trap density and a prolongation of carrier lifetime. The resulting planar solar cells based on 2D PEA2MA3Pb4I13 (n = 4) deliver an outstanding efficiency of ∼17.0% along with excellent operational stability.
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| 6. |
- Capone, F. G., et al.
(författare)
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Operando observation of the dynamic SEI formation on a carbonaceous electrode by near-ambient pressure XPS
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Ingår i: Energy and Environmental Science. - 1754-5692.
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Tidskriftsartikel (refereegranskat)abstract
- The dynamic formation of chemical species composing the solid electrolyte interphase (SEI) layer at the surface of a carbonaceous electrode in a carbonate-based liquid electrolyte was observed in real-time using operando near-ambient pressure XPS (NAP-XPS). The potential of the glassy carbon electrode vs. metallic lithium was controlled during the XPS experiment. By following the binding energy shifts as a function of applied potential, we could identify the main SEI species and observe their deposition on the electrode surface during the formation of the SEI. These results demonstrate that NAP-XPS is a powerful tool to investigate the SEI formation and stability in Li- and post-Li-ion batteries, paving the way for future studies on the effect of electrolyte additives and solvent mixtures on battery performance.
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