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.

LiNi0.5Mn1.5O4−δ surface is doped with Ti ion maintaining the spinel structure at 500 °C, higher annealing temperatures cause Ti diffusion from surface towards the core.

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Quasi-spherical undoped ZnO and Al-doped ZnO nanoparticles with different aluminum content, ranging from 0.5 to 5 at% of Al with respect to Zn, were synthesized. These nanoparticles were evaluated as photocatalysts in the photodegradation of the Rhodamine B (RhB) dye aqueous solution under UV-visible light irradiation. The undoped ZnO nanopowder annealed at 400 °C resulted in the highest degradation efficiency of ca. 81% after 4 h under green light irradiation (525 nm), in the presence of 5 mg of catalyst. The samples were characterized using ICP-OES, PXRD, TEM, FT-IR, 27Al-MAS NMR, UV-Vis and steady-state PL. The effect of Al-doping on the phase structure, shape and particle size was also investigated. Additional information arose from the annealed nanomaterials under dynamic N2 at different temperatures (400 and 550 °C). The position of aluminum in the ZnO lattice was identified by means of 27Al-MAS NMR. FT-IR gave further information about the type of tetrahedral sites occupied by aluminum. Photoluminescence showed that the insertion of dopant increases the oxygen vacancies reducing the peroxide-like species responsible for photocatalysis. The annealing temperature helps increase the number of red-emitting centers up to 400 °C, while at 550 °C, the photocatalytic performance drops due to the aggregation tendency.

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.

Sodium-ion batteries (SIBs) are potential cost-effective solutions for stationary energy storage applications. Unavailability of suitable anode materials, however, is one of the important barriers to the maturity of SIBs. Here, we report a Na2+x Ti4O9/C composite as a promising anode candidate for SIBs with high capacity and cycling stability. This anode is characterized by a capacity of 124 mAh g–1 (plus 11 mAh g–1 contributed by carbon black), an average discharge potential of 0.9 V vs Na/Na+, a good rate capability and a high stability (89% capacity retention after 250 cycles at a rate of 1 C). The mechanisms of sodium insertion/deinsertion and of the formation of Na2+x Ti4O9/C are investigated with the aid of various ex/in situ characterization techniques. The in situ formed carbon is necessary for the formation of the reduced sodium titanate. This synthesis method may enable the convenient synthesis of other composites of crystalline phases with amorphous carbon.

(LTO) is considered as a promising anode material for lithium ion batteries due to its high stability and its inherent safety. Since LTO is typically synthesized at high temperatures, a study of combustion synthesis of LTO is presented, wherein effects of oxidizer amount in the precursor and atmosphere during thermal decomposition are investigated. Combustion synthesis implies heating a precursor to a relatively low process temperature, after which the system generates the necessary energy for complete conversion and crystallization to the desired oxide. Hereto, the precursor and thermally treated powders were characterized by thermogravimetric analysis (TGA) coupled with differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), dynamic light scattering (DLS), X-ray diffraction (XRD), cyclic voltammetry (CV) and galvanostatic cycling. The study shows that the combustion process allows the synthesis of LTO at process temperatures as low as 300 C, compared to around 800 C for solid state reactions and sol-gel routes. The product consists of crystalline LTO with minor impurities. The product was used as an electrode material in a lithium battery coin cell and demonstrated a high stability and a capacity of 164 mA h g À1 at 0.1C and 132 mA h g À1 at 2C. This paper shows that combustion synthesis can considerably lower the temperature required for the synthesis of ceramic materials, after careful optimization of the precursor, since the mechanism of thermal degradation is complex and dependent on a large number of parameters.