Sodium‐ion batteries are alternatives for lithium‐ion batteries in applications where cost‐effectiveness is of primary concern, such as stationary energy storage. The stability of sodium‐ion batteries is limited by the current generation of electrolytes, particularly at higher temperatures. Therefore, the search for an electrolyte which is stable at these temperatures is of utmost importance. Here, such electrolytes are introduced in the form of nonflammable deep eutectic solvents (DESs), consisting of sodium bis(trifluoromethane)sulfonimide (NaTFSI) dissolved in N‐methyl acetamide (NMA). Increasing the NaTFSI concentration replaces NMA—NMA hydrogen bonds with strong ionic interactions between NMA, Na+, and TFSI−. These interactions lower NMA's highest occupied molecular orbital (HOMO) energy level compared with that of TFSI−, leading to an increased anodic stability (up to ≈4.65 V versus Na+/Na). (Na3V2(PO4)2F3/carbon nanotube [CNT])/(Na2+x Ti4O9/C) full cells show 97.0% capacity retention after 250 cycles at 0.2 C and 55 °C. This is considerably higher than for (Na3V2(PO4)2F3/CNT)/(Na2+x Ti4O9/C) full cells containing a conventional electrolyte. According to the electrochemical impedance analysis, the improved electrochemical stability is linked to the formation of more robust surface films at the electrode/electrolyte interface. The improved durability and safety highlight that DESs can be viable electrolyte alternatives for sodium‐ion batteries.

Radiative Cooling In article number http://doi.wiley.com/10.1002/aesr.202100159, Dries De Sloovere, An Hardy, and co‐workers, show that careful investigation and optimization of the coordination structure of deep eutectic solvents allows the preparation of a viable electrolyte alternative for sodium‐ion batteries. The optimized electrolyte is durable and nonflammable, considerably improving the safety of battery operation. Furthermore, it can offer a more durable electrochemical performance compared to conventional electrolytes.

Layered Li-rich/Mn-rich NMC (LMR-NMC) is characterized by high initial specific capacities of more than 250 mAh/g, lower cost due to a lower Co content and higher thermal stability than LiCoO2....

Co-free Li-rich layered oxides are gaining interest as feasible positive electrode materials in lithium-ion batteries (LIBs) in terms of energy density, cost reduction, and alleviating safety concerns. Unfortunately, their commercialization is hindered by severe structural degradation that occurs during electrochemical operation. The study at hand demonstrates advanced structural engineering of a Li-rich Co-free oxide with composition Li 1.1 Ni 0.35 Mn 0.55 O 2 by spray pyrolysis and subsequent calcination of an aqueous precursor, creating a segregated structure of two distinct layered phases with space groups R3̅ m (rhombohedral) and C2/m (monoclinic). This particular structure was investigated with powder neutron diffraction, high-resolution analytical transmission electron microscopy imaging, and electron energy loss spectroscopic characterization. This complex structure contributes to the high electrochemical stability and good rate capability observed for this compound (160 mAh/g at C/3 and 100 mAh/g at 1C) . These results provide new insights into the feasibility of developing and commercializing cobalt-free positive electrode materials for LIBs.