We propose lithium metal cells employing LiCF3SO3-tetraethylene glycol dimethy ether (TEGDME)\ud electrolyte solution with LiFePO4 and LiMn0.5Fe0.5PO4 cathodes. The electrolyte is selected due to its nonflammability, herein demonstrated, and considered as a key requirement for application cells employing\ud high energy lithium metal anode. The selected olivine cathodes, i.e., stable materials prepared by solvothermal\ud pathway, have regular submicrometrical morphology suitable for cell operation and homogeneous\ud composition, as confirmed by electron microscopy and energy dispersive X-ray spectroscopy.\ud The electrochemical tests reveal promising cycling performances in terms of delivered capacity, stability\ud and rate capability. The Li/LiCF3SO3-TEGDME/LiFePO4 cell operates at 3.5 V with capacity ranging from\ud 150 mAh g-1 at C/10 to 110 mAh g-1 at 2C, while the Li/LiCF3SO3-TEGDME/LiFe0.5Mn0.5PO4 cell performs\ud following two plateaus at 4.1 V and 3.5 V with capacity ranging from 160 mAh g-1 at C/10 to\ud 75 mAh g-1 at 2C. Hence, the results demonstrate the suitability of TEGDME-based electrolytes in\ud combination with LiFePO4 and LiFe0.5Mn0.5PO4 cathodes for high performances lithium battery

Herein we provide a fundamental study revealing the substantial changes promoted by manganese and iron substitution for cobalt in high-voltage LiCoPO4 olivine cathode. Therefore, LiCoPO4, LiCo0.9Fe0.1PO4, LiCo0.6Fe0.4PO4, LiCo0.9Mn0.1PO4 and LiCo0.6Mn0.4PO4 are synthesized by a solgel pathway and comparatively investigated in terms of structure, morphology and electrochemical features in lithium battery. Beside the observed effects on structure, particle size and metals distribution, the work reveals a gradually enhancing electrode reaction by increasing the Fe content in LiCo0.9Fe0.1PO4 and LiCo0.6Fe0.4PO4, with Co 3+ /Co 2+ and Fe 3+ /Fe 2+ signatures at 4.8 and 3.5 V vs. Li + /Li, respectively. On the other hand, the introduction of Mn leads to a progressive electrode deactivation in LiCo0.9Mn0.1PO4 and LiCo0.6Mn0.4PO4 due to an intrinsic hindering of the Mn 3+ /Mn 2+ process at 4.1 V vs. Li + /Li. The reasons accounting for such an intriguing behavior are 2 investigated in detail using electrochemical impedance spectroscopy within the potential range of the redox processes. The study reveals that manganese and iron substitutions in the high-voltage olivine have opposite effects on the charge transfer resistance, i.e., detrimental for the former while beneficial for the latter with remarkable enhancement of the reversible capacity, the coulombic efficiency, and the cycle life. Such results provide to the scientific community useful information on possible strategies to enhance the emerging LiCoPO4 high voltage electrode by transition metal substitution.