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Herein, the formulation of safe electrolytes for Li‐ion batteries based on phosphazene as a flame‐retardant (FR) is achieved. Three molecules are studied: hexafluorocyclotriphosphazene (FR1), (ethoxy)pentafluorocyclotriphosphazene (FR2), and pentafluoro(phenoxy)cyclotriphosphazene (FR3). By using a conventional electrolyte (LiPF6 salt in an ethylene carbonate/diethyl carbonate solvents mixture), FR's minimum percentages are defined to quantify their efficiency as FRs. Fluoroethylene carbonate is also added to the electrolyte (2 wt%). The surface tensions, vapor pressures, and transport properties of formulated electrolytes are measured to highlight the impact of the FR additives. Then, these electrolytes are tested in half and full electrochemical devices: Li|LiMn1.5Ni0.5O4 (LMNO) and graphite|LMNO between C/10 and C/2 at 20 °C. Flammability tests show that 3% of FR1, 5% of FR2, or 15% of FR3 are needed to make the electrolytes nonflammable. The transport properties of electrolytes based on FR1 and FR2 remain unchanged compared to the conventional electrolyte. Finally, the graphite|LMNO devices lose only 5% of the initial capacity after 100 cycles with the electrolytes based on FR1 and FR2, hence, confirming the latter's potential as an efficient FR for high‐voltage Li‐ion batteries. [ABSTRACT FROM AUTHOR]

Lithium‐ion batteries operating at high voltage generally endure drastic capacity fading and serious safety issues. Working on the electrolytes' stability can be a solution to mitigate these problems related to high voltage. Herein, the beneficial impact of functional electrolyte additives in a state‐of‐the‐art carbonate‐based electrolyte is demonstrated. The combination of fluoroethylene carbonate (FEC) with succinonitrile (SN) as additives was used to enhance the thermal stability of the electrolyte reference 1 M LiPF6 in EC:DMC (1 : 1, by weight) and cycling stability of a high voltage lithium‐ion device, consisting of a LiMn1.5Ni0.5O4 cathode and a metallic lithium anode. The electrolyte using the FEC/SN mixture displayed a wider electrochemical stability window (ESW) exhibited by linear sweep voltammetry (LSV). Furthermore, this electrolyte allowed the device to exhibit better rate capability and a capacity retention of 75 % after 100 cycles. Interestingly, the FEC+SN‐based electrolyte exhibited better thermal stability using operando accelerating rate calorimetry (ARC) by virtue of the lower heat quantity generated by the battery device. The remarkable improvements can be ascribed to the formation of a protective cathode‐electrolyte interface (CEI) produced by interfacial reactions between the cathode surface and electrolyte compounds. [ABSTRACT FROM AUTHOR]

Secondary zinc–MnO2 batteries represent the climax of aqueous battery technology owing to their high specific capacity and high power density. However, zinc–MnO2 batteries suffer from serious impediments such as capacity fading, poor electrical conductivity, and ion diffusion. Herein, we conducted an oxygen deficiency treatment on an amorphous manganese oxide with preexisting defects (A-MnO2) to maximize atom vacancies and compared it to its crystalline analogue (α-MnO2). As a result, A-MnO2 delivered a specific capacity of almost 600 mA h g−1 at 100 mA g−1, which is to our knowledge the highest specific capacity reported for undoped and non-composite manganese oxide, while α-MnO2 only reached 150 mA h g−1 under the same conditions. In addition, an in-depth investigation of the disordered material cycling mechanism using ex situ XRD and ex situ SEM validated the high specific capacity and explained the role of defect engineering and material disordering in taking aqueous batteries toward convincing high-scale commercialization. [ABSTRACT FROM AUTHOR]