RESUMEN
We present a sustainable, inherently safe battery chemistry that is based on widely available and cheap materials, that is, iron and manganese hosted in alginate bio-material known from the food and medical industry. The resulting battery can be recycled to allow circularity. The electrodes were synthesised by the alginate caging the multi-valent metals to form a hydrogel in an aqueous environment. Characterisation includes FTIR, XPS and Mössbauer spectroscopy. The electrochemical performance of the electrodes was investigated by performing cyclic voltammetry (CV) and (dis)charge experiments. Mn and Fe ions show good co-ordination with the alginic acid with higher oxidation states demonstrating complex bonding behaviour. The non-optimised iron and manganese alginate electrodes already exhibit a cycling efficiency of 98% and 69%, respectively. This work shows that Fe and Mn atomically disperse in a bio-based host material and can act as electrodes in an aqueous battery chemistry. While demonstrated at cell level, it is furthermore explained how these materials can form the basis for a (semi-solid) flow cell.
RESUMEN
Rechargeable solid-state sodium-ion batteries (SSSBs) hold great promise for safer and more energy-dense energy storage. However, the poor electrochemical stability between current sulfide-based solid electrolytes and high-voltage oxide cathodes has limited their long-term cycling performance and practicality. Here, we report the discovery of the ion conductor Na3-xY1-xZrxCl6 (NYZC) that is both electrochemically stable (up to 3.8 V vs. Na/Na+) and chemically compatible with oxide cathodes. Its high ionic conductivity of 6.6 × 10-5 S cm-1 at ambient temperature, several orders of magnitude higher than oxide coatings, is attributed to abundant Na vacancies and cooperative MCl6 rotation, resulting in an extremely low interfacial impedance. A SSSB comprising a NaCrO2 + NYZC composite cathode, Na3PS4 electrolyte, and Na-Sn anode exhibits an exceptional first-cycle Coulombic efficiency of 97.1% at room temperature and can cycle over 1000 cycles with 89.3% capacity retention at 40 °C. These findings highlight the immense potential of halides for SSSB applications.
RESUMEN
Organosulfur silanes grafted on an aluminum current collector have been proposed and demonstrated to function as a sulfur source in the cathode for a lithium-sulfur (Li-S) battery. Bis[3-(triethoxysilyl)propyl]disulfide silane (TESPD) and bis[3-(triethoxysilyl)propyl]tetrasulfide silane (TESPT) are typical examples of organosulfur complexes used for the study. These organosulfur silanes act as an insulator. Formation of polysulfides (Li2Sx), which is a major bottleneck in the case of elemental sulfur, can be eliminated using this novel cathode. In the absence of charge-carrying polysulfide species, the role of insulating TESPD/TESPT in the charge conduction pathway is an open question. Insight into the interface between the Al current collector and grafted TESPD/TESPT at an atomic level is a prerequisite for addressing the charge conduction pathway. The systematic theoretical methodology is developed based on electronic structure calculations and ab initio molecular dynamics simulations to propose the realistic cathode model (hydration environment) for the Li-S battery. A cluster model is developed to predict the reduction potentials of TESPD/TESPT disclosing the reduction reaction with Li, resulting in the intramolecular S-S bond breaking which is validated by experimental cyclic voltammetry measurements. A realistic cathode model between the aluminum current collector and TESPD/TESPT is also proposed to mimic the experimental conditions where the Al surface was exposed to O2 and H2O. The top few layers of Al are transformed into α-Al2O3 and covered with H2O molecules in the vicinity of grafted TESPD/TESPT. The structural models are further validated by comparing simulated S 2p binding energies with experimental X-ray photoelectron spectroscopy studies.
