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Olivine LiMn1–x Fe x PO4 (x = 0.5, 0.4, 0.3, 0.2) coated with carbon are prepared as the cathode materials for the aqueous rechargeable lithium-ion batteries (ARLBs). Li+ insertion-extraction behaviors of the as-prepared materials in LiNO3 aqueous electrolyte with/without dissolved oxygen are studied by cyclic voltammograms (CVs) and electrochemical impedance spectra (EIS). The Li+ diffusion coefficient of LiMn1–x Fe x PO4 in LiNO3 aqueous electrolyte is first reported. The results indicate that eliminating the dissolved oxygen in the aqueous electrolyte could decrease the charge transfer-resistance and increase the Li+ diffusion coefficient of (LiMn1–x Fe x PO4/C)//LiV3O8 ARLBs, which also improves the electrochemical properties of the ARLBs. The initial discharge specific capacity of LiMn0.6Fe0.4PO4/C is 112 mA h g–1 at 0.1 C-rate, which provides a new candidate cathode material for ARLBs.

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To improve the electrochemical performance of cathode material in aqueous LiNO 3 solution, modified spinel LiMn 2 O 4 materials prepared with different amounts of sucrose additive are synthesized using a two-step sintering method. The phase structure and morphologies of as-prepared samples are characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. Electrochemical performances of modified LiMn 2 O 4 used as the cathode material of the aqueous rechargeable lithium battery (ARLB) are investigated by galvanostatic charge/discharge testing. The effects of the carbon, which decomposed from the additive sucrose, on the electrochemical performances of the modified spinel LiMn 2 O 4 cathode for the ARLBs are discussed. In comparison to pristine LiMn 2 O 4 , the optimum quantity of sucrose addition improves the electrochemical performance of spinel LiMn 2 O 4 material in an aqueous LiNO 3 solution, especially for the addition of 20 wt % sucrose, and its initial discharge specific capacity is 118.3 mAh g À1 ; moreover, it still has 102.8 mAh g À1 after 40 cycles.