Mobile and stationary energy storage by rechargeable batteries is a topic of broad societal and economical relevance. Lithium-ion battery (LIB) technology is at the forefront of the development, but a massively growing market will likely put severe pressure on resources and supply chains. Recently, sodium-ion batteries (SIBs) have been reconsidered with the aim of providing a lower-cost alternative that is less susceptible to resource and supply risks. On paper, the replacement of lithium by sodium in a battery seems straightforward at first, but unpredictable surprises are often found in practice. What happens when replacing lithium by sodium in electrode reactions? This review provides a state-of-the art overview on the redox behavior of materials when used as electrodes in lithium-ion and sodium-ion batteries, respectively. Advantages and challenges related to the use of sodium instead of lithium are discussed.

Die mobile und stationäre Energiespeicherung durch wiederaufladbare Batterien ist ein Thema von breiter gesellschaftlicher und ökonomischer Bedeutung. Die wichtigste Technologie in diesem Bereich ist die Lithiumionenbatterie (LIB), jedoch muss man davon ausgehen, dass ein massiv wachsender LIB‐Markt ernsten Druck auf Ressourcen und Lieferketten ausüben wird. Seit kurzem richtet sich die Aufmerksamkeit daher auch wieder auf die Natriumionenbatterie (SIB), die eine preisgünstige Alternative darstellen könnte, die weniger anfällig für Ressourcen‐ und Versorgungsrisiken ist. Auf dem Papier scheint der Austausch von Lithium durch Natrium in einer Batterie unkompliziert, jedoch erlebt man in der Praxis oft unvorhersehbare Überraschungen. Was geschieht, wenn in Elektrodenreaktionen Lithium durch Natrium ersetzt wird? Dieser Aufsatz bietet einen aktuellen Überblick über das Redoxverhalten von Materialien bei ihrer Verwendung als Elektroden in LIBs bzw. SIBs. Die Vorteile und Herausforderungen im Zusammenhang mit der Verwendung von Natrium anstelle von Lithium werden diskutiert.

Lithium and sodium thiophosphates (and related compounds) have recently attracted attention because of their potential use as solid electrolytes in solidstate batteries. These compounds, however, exhibit only limited stability in practice as they react with the electrodes. The decomposition products partially remain redox active hence leading to excess capacity. The redox activity of thiophosphates is explicitly used to act as electrode for sodium-ion batteries. Copper thiophosphate (Cu 3 PS 4 ) is used as a model system. The storage behavior between 0.01 and 2.5 V versus Na + /Na is studied in half cells using different electrolytes with 1 m NaPF 6 in diglyme showing the best result. Cu 3 PS 4 shows highly reversible charge storage with capacities of about 580 mAh g −1 for more than 200 cycles @120 mA g −1 and about 450 mAh g −1 for 1400 cycles @1 A g −1 . The redox behavior is studied by operando X-ray diffraction and X-ray photoelectron spectroscopy. During initial sodiation, Cu 3 PS 4 undergoes a conversion reaction including the formation of Cu and Na 2 S. During cycling, the redox activity seems dominated by sulfur. Interestingly, the capacity of Cu 3 PS 4 for lithium storage is smaller, leading to about 170 mAh g −1 after 200 cycles. The results demonstrate that thiophosphates can lead to reversible charge storage over several hundred cycles without any notable capacity decay.

Tin (Sn), antimony (Sb), as well as their intermetallic compound SnSb are potential high‐capacity negative electrodes for lithium‐ or sodium‐ion batteries. Starting from bulk Sn and Sb, the effect of ball milling in sodium‐ion half cells with a diglyme‐based electrolyte is studied. Nonreactive ball milling of Sn, Sb, and carbon leads to intimately mixed but largely phase‐separated composites (Sn + Sb) with electrochemical sodiation behavior being the sum of the individual phases. Thereby, Sb shows an unusual and rapid capacity fade in the chosen electrolyte which is unexpected, considering the usually excellent compatibility of diglyme‐based electrolytes with negative electrodes. Reactive ball milling of Sn and Sb using a planetary ball mill leads to the phase‐pure intermetallic compound β‐SnSb. Compared with Sn + Sb, SnSb shows excellent performance with a specific capacity exceeding 400 mAh g−1 after 190 cycles and a high rate capability (around 400 mAh g−1 at 5 C). Hence, herein, Sb is largely inactive as a pure phase but active when bound in the β‐SnSb intermetallic compound. Using in situ electrochemical dilatometry, the “breathing” of the electrodes during charging/discharging is minimized by optimizing ball‐milling time, which improves cycle life.

We investigated herein the morphological, structural, and electrochemical features of electrodes using a sulfur (S)-super P carbon (SPC) composite (i.e., S@SPC-73), and including few-layer graphene (FLG), multiwalled carbon nanotubes (MWCNTs), or a mixture of them within the current collector design. Furthermore, we studied the effect of two different electron-conducting agents, that is, SPC and FLG, used in the slurry for the electrode preparation. The supports have high structural crystallinity, while their morphologies are dependent on the type of material used. Cyclic voltammetry (CV) shows a reversible and stable conversion reaction between Li and S with an activation process upon the first cycle leading to the decrease of cell polarization. This activation process is verified by electrochemical impedance spectroscopy (EIS) with a decrease of the resistance after the first CV scan. Furthermore, CV at increasing scan rates indicates a Li+ diffusion coefficient (D) ranging between 10−9 and 10−7 cm2·s−1 in the various states of charge of the cell, and the highest D value for the electrodes using FLG as electron-conducting agent. Galvanostatic tests performed at constant current of C/5 (1 C = 1675 mA·gS−1) show high initial specific capacity values, which decrease during the initial cycles due to a partial loss of the active material, and subsequently increase due to the activation process. All the electrodes show a Coulombic efficiency higher than 97% upon the initial cycles, and a retention strongly dependent on the electrode formulation. Therefore, this study suggests a careful control of the electrode in terms of current collector design and slurry composition to achieve good electrode morphology, mechanical stability, and promising electrochemical performance in practical Li-S cells.