Rechargeable aqueous zinc-manganese dioxide batteries with high energy and power densities

Rechargeable aqueous zinc-manganese dioxide batteries with high energy and power densities Ning Zhang Fangyi Cheng Junxiang Liu Liubin Wang Xinghui Long Xiaosong Liu Fujun Li Jun Chen

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Rechargeable aqueous zinc-manganese dioxide batteries with high energy and power densities 2017 Nature Communications 10.1038/s41467-017-00467-x zhang2017-rechargeable-aqueous-zinc-manganes zhang2017-rechargeable-aqueous-zinc-manganes.txt, the project's staged copy ccb832c3ca78a24dd34a47d9a4a6aa099e66b5ed cc-by engineering

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0 spans located by searching the stored text for the quote's exact words, allowing any whitespace between them what actually happens at a manganese dioxide cathode in a mild-acidic aqueous zinc cell - which phase is present, which ion moves, and where the lost capacity goes Quotation withheld because this record is not cleared for redistribution. whether the competing published mechanisms for Zn insertion in MnO2 polymorphs are different reactions or one reaction seen at different points, and whether the resulting cell can be made to cycle Quotation withheld because this record is not cleared for redistribution. one common electrode mechanism for alpha, beta and gamma MnO2 - an irreversible tunnel-to-layered conversion to Zn-buserite on first discharge followed by reversible Zn2+ (de)intercalation - plus a triflate electrolyte with a Mn2+ additive giving 94% retention over 2000 cycles Quotation withheld because this record is not cleared for redistribution. mechanism Quotation withheld because this record is not cleared for redistribution. a cathode material that changes identity during its own first discharge, so that its measured properties before and after describe different substances Quotation withheld because this record is not cleared for redistribution. experiment experiment Quotation withheld because this record is not cleared for redistribution. Zn2+ and water co-insert into the pyrolusite framework, manganese dissolves away leaving vacancies, and the tunnel structure distorts into stacked layers with water between them; every subsequent cycle is intercalation into that layered product, so the material's own first discharge is the synthesis of the working electrode a host that becomes a different host on first use Quotation withheld because this record is not cleared for redistribution. Mn3+ in the solid disproportionates into Mn4+ that stays and Mn2+ that leaves; pre-loading the electrolyte with Mn2+ moves the equilibrium so that less leaves, which is why an additive that is not a reactant improves retention a dissolution equilibrium bought with a sacrificial solute Quotation withheld because this record is not cleared for redistribution. charging in Mn2+-containing electrolyte electrodeposits a porous amorphous MnOx nanosheet film on the cathode; being porous it does not impede mass diffusion, and it holds the electrode together - the EIS shows a new interface resistance of 6 ohm appearing while charge transfer falls from 350 to 25 a deposit that protects rather than blocks Quotation withheld because this record is not cleared for redistribution. triflate carries one charge against sulfate's two and is larger, so fewer water molecules surround each Zn2+; the ion moves and transfers charge more easily, which the paper offers as why the same cation in two salts gives 275 against 120 mAh g-1 a bulky anion thinning the solvation shell Quotation withheld because this record is not cleared for redistribution. the exact structural motif of the Zn-buserite phase the whole mechanism rests on is not determined Quotation withheld because this record is not cleared for redistribution. the tunnel-to-layer conversion is irreversible, and together with Mn dissolution and electrode pulverization it is the source of the capacity fade the additive only mitigates Quotation withheld because this record is not cleared for redistribution. nanorods expand and exfoliate over cycling, which the authors expect to cost capacity Quotation withheld because this record is not cleared for redistribution. the triflate salt is more expensive than the sulfate or hydroxide it replaces, and the authors say so rather than leaving it to a reader Quotation withheld because this record is not cleared for redistribution. the deposited MnOx layer contributes about 2.4% of the delivered capacity itself, so the reported cathode capacity is not purely the cathode's Quotation withheld because this record is not cleared for redistribution. the mechanism literature it corrects is genuinely contradictory - spinel, layered, birnessite and a conversion reaction have all been proposed for the same electrode Quotation withheld because this record is not cleared for redistribution. buserite, a layered manganese oxide known as a mineral, used as the structural model for a discharge product in a battery electrode Quotation withheld because this record is not cleared for redistribution. synchrotron X-ray absorption spectroscopy, carried from structural physics into reading the oxidation state and local coordination of a cycled electrode Quotation withheld because this record is not cleared for redistribution. the discharged electrode rinsed with water before EDS and XPS, with sulfur and fluorine checked for as the signature of residual electrolyte salt eliminates: precipitated electrolyte on the surface being read as part of the discharge product - S and F absent means the Zn and Mn signal is the electrode's · outcome: held Quotation withheld because this record is not cleared for redistribution. the rinsed discharged XRD pattern compared against every species previously reported for this electrode - MnOOH, spinel ZnMn2O4, birnessite, tunnelled and layered Zn-Mn oxides - and then Rietveld refined eliminates: the new phase being one of the published ones under another name; the comparison is to the named alternatives, not to nothing · outcome: held Quotation withheld because this record is not cleared for redistribution. alpha-MnO2 and gamma-MnO2 taken through the identical XRD and XAS analysis, not only the beta polymorph the argument is built on eliminates: the mechanism being a peculiarity of one polymorph - the claim is that the three converge, and it is tested on the three · outcome: held Quotation withheld because this record is not cleared for redistribution. thermal gravimetric analysis of the discharged phase, to test whether the water the structural model requires between the layers is actually there eliminates: the layered assignment resting on diffraction alone - the model predicts interlayer water and a mass-loss measurement can refute it · outcome: held Quotation withheld because this record is not cleared for redistribution. ICP-AES on the electrolyte at successive states of discharge, after the measured Mn valence disagreed with the value the delivered capacity predicts eliminates: the postulated disproportionation staying a postulate - the manganese that left the electrode is counted where it went rather than inferred from where it is not · outcome: held Quotation withheld because this record is not cleared for redistribution. four electrolytes compared on the same cell chemistry - 45 wt% KOH, 3 M ZnSO4, 3 M Zn(CF3SO3)2, and the same with 0.1 M Mn(CF3SO3)2 added eliminates: the cathode alone as the explanation of the cycling behaviour, and alkaline against mild-acidic as an untested assumption · outcome: held Quotation withheld because this record is not cleared for redistribution. the additive chosen as Mn(CF3SO3)2 rather than MnSO4, and then the cross combinations ZnSO4+MnSO4 and Zn(CF3SO3)2+MnSO4 also run eliminates: the anion as a hidden variable in the additive experiment - varying the cation while the anion changes too would confound the two · outcome: held Quotation withheld because this record is not cleared for redistribution. electrolyte concentration varied from 1 M to 3 M with everything else held eliminates: concentration being confounded with the choice of salt · outcome: held Quotation withheld because this record is not cleared for redistribution. three-electrode voltammetry across the working potential window, against the Nernst estimate for forming MnO2 and Mn2O3 from the additive eliminates: the added Mn2+ being reduced and plated during operation - the measurement shows it is not, within the window actually used · outcome: held Quotation withheld because this record is not cleared for redistribution. the capacity contributed by the deposited MnOx layer itself measured separately eliminates: the protective deposit being an unacknowledged second active material - it is one, at 2.4%, and the number is given · outcome: held Quotation withheld because this record is not cleared for redistribution. EIS on dismantled cathodes after ten cycles, with and without the additive, fitted to the same equivalent circuit eliminates: the additive's benefit being attributed to chemistry when it is partly interfacial - the fit separates series, interface, charge-transfer and diffusion terms and only some of them move · outcome: held Quotation withheld because this record is not cleared for redistribution. post-mortem examination of the zinc anode in all three electrolytes, plus EDS for manganese on the anode surface eliminates: the cathode being credited with a cell-level improvement that belongs to the anode, and manganese plating on the zinc as a hidden sink · outcome: held Quotation withheld because this record is not cleared for redistribution. commercial micrometre-sized beta-MnO2 powder run in the same electrolyte alongside the hydrothermally grown nanorods eliminates: the nanorod morphology as the source of the result - a bulk commercial powder with no special preparation also cycles · outcome: held Quotation withheld because this record is not cleared for redistribution. Zn-buserite Zn-buserite Quotation withheld because this record is not cleared for redistribution. phase transition phase transition Quotation withheld because this record is not cleared for redistribution. polymorphs polymorphs Quotation withheld because this record is not cleared for redistribution. disproportional dissolution disproportional dissolution Quotation withheld because this record is not cleared for redistribution. capacity retention capacity retention Quotation withheld because this record is not cleared for redistribution. electrode integrity electrode integrity Quotation withheld because this record is not cleared for redistribution. Coulombic efficiency Coulombic efficiency Quotation withheld because this record is not cleared for redistribution. EXAFS EXAFS Quotation withheld because this record is not cleared for redistribution. ICP-AES ICP-AES Quotation withheld because this record is not cleared for redistribution. energy density energy density Quotation withheld because this record is not cleared for redistribution. b-MnO2's capacity for zinc - AS CHARACTERISED IN THE LITERATURE: hardly any, because the (1 x 1) tunnels are too narrow to admit Zn2+ Quotation withheld because this record is not cleared for redistribution. b-MnO2's capacity for zinc - AS MEASURED HERE: 307 mAh g-1 on first discharge against a theoretical 308, because the tunnels have stopped existing Quotation withheld because this record is not cleared for redistribution. the cell's energy density - PER ACTIVE MATERIAL MASS: 158.5 Wh kg-1 Quotation withheld because this record is not cleared for redistribution. the cell's energy density - PER WHOLE BATTERY MASS: 75.2 Wh kg-1, the number the abstract quotes and the only one comparable to the Pb-acid and Ni-Cd figures printed beside it Quotation withheld because this record is not cleared for redistribution. the Mn oxidation state at full discharge - AS PREDICTED FROM THE CAPACITY: about 3.0 Quotation withheld because this record is not cleared for redistribution. the Mn oxidation state at full discharge - AS MEASURED BY XANES: 3.6, and the gap is 8.9% of the manganese having left for the electrolyte Quotation withheld because this record is not cleared for redistribution. critiques → the published mechanisms for Zn insertion in MnO2 - spinel ZnMn2O4, layered Zn-buserite, birnessite and a conversion reaction to MnOOH have all been proposed for the same electrode, and the paper says the mechanism remains elusive and controversial Quotation withheld because this record is not cleared for redistribution. qualifies → the characterisation of beta-MnO2 as unable to host zinc because its tunnels are too narrow - true of the phase, and irrelevant to the electrode, because the phase does not survive the first discharge Quotation withheld because this record is not cleared for redistribution. extends → the practice of pre-adding Mn2+ salt to improve capacity retention, which was known to work and whose mechanism the paper says was unclear - resolved here into three separate functions Quotation withheld because this record is not cleared for redistribution. qualifies → its own cost case - the triflate salt is more expensive than the sulfate and hydroxide alternatives it outperforms Quotation withheld because this record is not cleared for redistribution. Zn-buserite —distinct-from→ polymorphs Zn-buserite polymorphs differs in: which phase is actually present after the first discharge, as against which was assumed · the relation itself is separately evidenced · strength of the relation: 0.95 · differs in (stated by the tagger, no quotation): which phase is actually present after the first discharge, as against which was assumed · the relation stated: the rinsed discharged pattern matches none of the species previously reported for this reaction Audit 2026-09-28: DOUBTFUL - read against its full span and kept, but the span says the two polymorphs TRANSFORM into Zn-buserite; distinct-from is loose. Quotation withheld because this record is not cleared for redistribution. alpha, beta and gamma MnO2 all convert to layered Zn-buserite on first discharge, so the three polymorphs share one electrode mechanism alpha, beta and gamma MnO2 all convert to layered Zn-buserite on first discharge, so the three polymorphs share one electrode mechanism Quotation withheld because this record is not cleared for redistribution. beta-MnO2's initial discharge capacity reaches 307 of a theoretical 308 mAh g-1. beta-MnO2's initial discharge capacity reaches 307 of a theoretical 308 mAh g-1. Quotation withheld because this record is not cleared for redistribution. the tunnel-to-layer conversion is irreversible, shown by EXAFS spectra that do not recover on first recharge the tunnel-to-layer conversion is irreversible, shown by EXAFS spectra that do not recover on first recharge Quotation withheld because this record is not cleared for redistribution. At full discharge about 8.9% of the total manganese is dissolved in the electrolyte. At full discharge about 8.9% of the total manganese is dissolved in the electrolyte. Quotation withheld because this record is not cleared for redistribution. the Mn2+ additive does three separate things - accommodates dissolution, raises efficiency and conductivity, and deposits a porous MnOx film that holds the electrode together the Mn2+ additive does three separate things - accommodates dissolution, raises efficiency and conductivity, and deposits a porous MnOx film that holds the electrode together Quotation withheld because this record is not cleared for redistribution. The full cell delivers 158.5 Wh kg-1 on active-material mass and 75.2 Wh kg-1 on whole-battery mass. The full cell delivers 158.5 Wh kg-1 on active-material mass and 75.2 Wh kg-1 on whole-battery mass. Quotation withheld because this record is not cleared for redistribution. 94% capacity retention over 2000 cycles at 6.50 C with Coulombic efficiency approaching 100% 94% capacity retention over 2000 cycles at 6.50 C with Coulombic efficiency approaching 100% Quotation withheld because this record is not cleared for redistribution. the layered water-containing manganese oxide formed during the first discharge, whose XRD pattern differs from every species previously reported for this electrode Zn-buserite Quotation withheld because this record is not cleared for redistribution. Mn3+ in the solid splitting into Mn4+ that remains and Mn2+ that dissolves - proposed to explain a measured valence of 3.6 where the capacity predicts 3.0 disproportional dissolution Quotation withheld because this record is not cleared for redistribution. mAh g-1 initial discharge capacity of a polymorph the literature calls electrochemically inactive, against a theoretical 308 307 Quotation withheld because this record is not cleared for redistribution. capacity retention over 2000 cycles at 6.50 C with the triflate-plus-Mn2+ electrolyte 94% Quotation withheld because this record is not cleared for redistribution. of the total manganese found dissolved in the electrolyte at full discharge, measured by ICP-AES 8.9% Quotation withheld because this record is not cleared for redistribution. Wh kg-1 per ACTIVE MATERIAL mass - the same cell that gives 75.2 per whole-battery mass 158.5 Quotation withheld because this record is not cleared for redistribution. Wh kg-1 per WHOLE BATTERY mass - the number the abstract quotes, and the only one comparable to the Pb-acid and Ni-Cd figures printed beside it 75.2 Quotation withheld because this record is not cleared for redistribution. of the delivered capacity contributed by the protective MnOx deposit rather than by the cathode 2.4% Quotation withheld because this record is not cleared for redistribution. Rietveld refinement Rietveld refinement Quotation withheld because this record is not cleared for redistribution. capacity retention capacity retention Quotation withheld because this record is not cleared for redistribution. energy density energy density Quotation withheld because this record is not cleared for redistribution.

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