Modeling Nucleation and Growth of Zinc Oxide During Discharge of Primary Zinc-Air Batteries

Metal-air batteries are among the most promising next-generation energy storage devices. Relying on abundant materials and offering high energy densities, potential applications lie in the fields of electro-mobility, portable electronics, and stationary grid applications. Now, research on secondary zinc-air batteries is revived, which are commercialized as primary hearing aid batteries. One of the main obstacles for making zinc-air batteries rechargeable is their poor lifetime due to the degradation of alkaline electrolyte in contact with atmospheric carbon dioxide. In this article, we present a continuum theory of a commercial Varta PowerOne button cell. Our model contains dissolution of zinc and nucleation and growth of zinc oxide in the anode, thermodynamically consistent electrolyte transport in porous media, and multi-phase coexistance in the gas diffusion electrode. We perform electrochemical measurements and validate our model. Excellent agreement between theory and experiment is found and novel insights into the role of zinc oxide nucleation and growth and carbon dioxide dissolution for discharge and lifetime is presented. We demonstrate the implications of our work for the development of rechargeable zinc-air batteries.Comment: 16 pages, 8 figures, Supplementary Information uploaded as ancillary fil

On the nanoscopic structural heterogeneity of liquid n-alkyl carboxylic acids

Herein we report the first in-depth structural characterisation of simple linear carboxylic acids with alkyl tail length ranging from one to six carbon atoms. By means of the SWAXS technique, a pronounced nanoscopic heterogeneity evolving along the aliphatic portion of the molecule is highlighted. Via classical molecular dynamics, the origin of such heterogeneity is unambiguously assigned to the existence of aliphatic domains resulting from the self-segregation of the polar and apolar portions of the molecules. Furthermore, the structural correlation of aliphatic-separated polar domains is responsible for observing the so-called “pre-peak” in the SAXS region

Mixed Metal‐Organic Frameworks as Efficient Semi‐Solid Electrolytes for Magnesium‐Ion Batteries

One of the main issues of metal organic framework (MOF)-based solid electrolytes (SE) is their high guest solvent content reaching up to >50 wt% of the total mass of SE pellets. The presence of large solvent amounts reduces the SE hardness and the electrochemical stability in presence of a magnesium (Mg) anode. Moreover, this often leads to misleading ionic conductivity values. In the present work, a strategy to minimize the guest solvent in MOF-based SE from 44–55 wt% to 20–30 wt% of the total SE\u27s mass is presented. Moreover, mixed metal organic frameworks of different structures and crystallinity are demonstrated for the first time to enhance the ionic conductivity of Mg$^{2+}$ ions inside the MOFs’ structures. The presence of both highly crystalline and amorphous MOFs increases the degree of disorder in the mixture and consequently opens up extra pathways for Mg$^{2+}$ ion diffusion. The ionic conductivity of mixed MOFs [amorphous Mgbp3dc and crystalline α-Mg$_3$(HCOO)$_6$] showed an enhanced value of 3.8×10$^{−5}$ S cm$^{−1}$ at 30 °C compared to 1.1×10$^{−6}$ S cm$^{−1}$ for α-Mg$_3$(HCOO)$_6$. Mixed MOF-SEs with a transference number (t+) of 0.335 showed a good stability in the presence of Mg electrodes with an enhanced reversibility upon galvanostatic cycling

Novel sulfur-doped single-ion conducting multi-block copolymer electrolyte

Solid-state lithium batteries are considered one of the most promising candidates for future electrochemical energy storage. However, both inorganic solid electrolytes (such as oxide-based or sulfide-based materials) and polymer electrolytes still have to overcome several challenges to replace the currently used liquid organic electrolytes. An increasingly adopted approach to overcome these challenges relies on the combination of different electrolyte systems. Herein, we report the synthesis and characterization of a novel sulfur-doped single-ion conducting multi-block copolymer (SIC-BCE) system. This SIC-BCE may serve as interlayer between the electrodes and the sulfidic electrolyte such as Li$_{6}$PS$_{5}$Cl, thus benefitting of the high ionic conductivity of the latter and the favorable interfacial contact and electrochemical stability of the polymer. The polymer shows excellent ionic conductivity when swollen with ethylene carbonate and allows for stable stripping/plating of lithium, accompanied by a suitable electrochemical stability towards reduction and oxidation. First tests in symmetric Cu|SIC-BCE|Li$_{6}$PS$_{5}$Cl|SIC-BCE|Cu cells confirm the general suitability of the polymer to stabilize the electrode|electrolyte interface by preventing the direct contact of the sulfidic electrolyte with, e.g., metallic copper foils

Portable High Voltage Integrated Harvesting-Storage Device Employing Dye-Sensitized Solar Module and All-Solid-State Electrochemical Double Layer Capacitor

A dye-sensitized solar module (DSSM) and a high voltage all-solid-state electrochemical double layer capacitor (EDLC) are, for the first time, implemented in a compact Harvesting-Storage (HS) device. Conductive glass is employed as current collecting substrate for both DSSM and EDLC, leading to a robust and portable final structure. The photovoltaic section is constituted by a 4 series cells W-type module, while in the storage section an EDLC employing an ionic liquid-based polymeric electrolyte (a mixture of polyethylene oxide and N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide, PEO-Pyr14TFSI) and activated carbon electrodes is used. The solid state EDLC is first characterized individually to determine its electrochemical performance before successfully proving the integration with the DSSM. The harvesting-storage properties of the integrated photo-capacitor are evaluated through photo-charge and subsequent discharge protocols performed at two different discharge currents, showing that in this configuration the EDLC unit can be effectively charged up to 2.45 V

High loading CuS-based cathodes for all-solid-state lithium sulfur batteries with enhanced volumetric capacity

Transition metal sulfides have shown to improve the performance of lithium-sulfur batteries both with liquid and solid electrolytes. In this work, the beneficial effect of copper sulfide for enabling high areal capacity lithiumsulfur all-solid-state batteries is shown. Copper sulfide-carbon (CuSC) and three different copper sulfide-sulfurcarbon (CuSS) composites are investigated as positive electrodes in all-solid-state lithium-sulfur batteries. The composites are prepared via facile and low-cost mechanochemical ball-milling. It is found that the CuS/C ratio greatly influences the redox properties of the CuSC cathode. Scanning electron microscopy, ex-situ X-ray diffraction, and galvanostatic cycling were also conducted to evaluate the CuSS composite electrodes in Li|LiI-Li$_{3}$PS$_{4}$|CuS–S–C solid-state cells. High mass loading cells made using these composite electrodes deliver capacities as high as 1600 mAh g$^{-1}$$_{(CuS+S)}$ and 7 mAh cm$^{-2}$ at 20 °C. The higher density of CuS also leads to larger volumetric capacities, up to 3900 mAh cm$^{-3}$$_{(CuS+S)}$, thus enabling a potential energy density gain up to 15% with respect to a conventional Carbon–Sulfur cathode

Liquid-Assisted Mechanochemical Synthesis of LiI-Doped Sulfide Glass Electrolyte

Inorganic solid electrolytes (ISEs) gain tremendous attention during the past decade for application in energy storage. Among different classes of ISEs, sulfides are particularly appealing due to their higher ionic conductivity, ductility, and lower density compared with oxides. However, most of the preparation methods proposed so far require either the time-consuming mechanical ball-milling process or the energy-consuming high-temperature solid-state reaction. Herein, a new and fast liquid-assisted approach to synthesize LiI-doped glassy Li$_{2}$S-P$_{2}$S$_{5}$ (LPS) with excellent electrochemical and morphological features is reported. The obtained solid electrolyte offers an ionic conductivity of 1.2 mS cm$^{-1}$ at room temperature and establishes a rather stable interphase with lithium. These enable rather high critical current densities (up to 1 mA cm$^{-2}$), as well as enhanced cathode active material utilization in solid-state lithium metal cells