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Abstract: Olivine structure LiMnPO4 has been considered as one of the very promising electrodes for lithium-ion batteries because of their low cost, low toxicity and high voltage plateau compared with LiFePO4. In order to improve the electrochemical performance a key challenge in the field of lithium-ion battery, is to explore and invent suitable synthetic route to control the size and morphology of LiMnPO4. Here a detailed study exploring the novel route of microwave-hydrothermal (MH) synthesis for successfully obtaining LiMnPO4 crystals within few minutes is reported and the reaction process discussed in detail. Variation of the synthetic parameters show that a decrease in reactant concentration could lead to LiMnPO4 nano-platelets orientated in the ac plane with a very high electrochemical performance. The effect of the starting precursor (like, Mn) concentration as a means to tailor LiMnPO4 electrochemical performance is discussed. The effect of alteration of size, morphology, lattice parameters and crystal structure induced by addition of additives like citric acid (H3cit) and sodium dodecyl benzene sulfonate (SDBS) is further described and an example of the first reversible discharge of a product treated with H3cit obtained by MH route as high as 89.0mAh/g, is shown. The general investigation demonstrates that there is a relationship among microwave irradiation condition, crystal structure, morphology and electrochemical performance that can be exploited for the design of next generation lithium batteries. [Copyright &y& Elsevier]

Abstract: To investigate the crystal structure and electrochemical performance of samples synthesized under different microwave solid-state synthesis condition, a series of Li3V2(PO4)3 samples has been synthesized at five different temperatures for 3–5min and at 750°C for various time. The as-synthesized Li3V2(PO4)3 samples are characterized and studied by ICP-AES analysis, X-ray diffraction (XRD), Rietveld analysis, scanning and transmission electron microcopy (SEM and TEM). At relatively lower temperature (650°C) and very short reaction time (3min), pure phase of Li3V2(PO4)3 could be synthesized in microwave irradiation field. The crystal structure and Li atomic fractional coordinate present a significant deviation upon the change of microwave irradiation temperature and time. Relatively, the diffusion ability of lithium cations and the electrochemical performance are affected. Under the proper reaction temperature and time, the carbon-free samples MW750C5m and MW850C3m show the best specific discharge capacity 126.4 and 132mAhg−1 at the voltage range of 3.0–4.3V, near the reversible cycling of two lithium ions per Li3V2(PO4)3 formula unit (133mAhg−1). At the voltage range of 3–4.8V, the sample MW750C5m presents the best initial specific charge capacity of 197mAhg−1, equivalent to the reversible cycling of three lithium ions per Li3V2(PO4)3 formula unit (197mAhg−1). The initial discharge capacity, the samples MW750C5m and MW850C3m present high specific discharge capacity 183.4 and 175.7mAhg−1, respectively. The relationship among microwave irradiation condition, crystal structure, lithium atomic fractional coordinates and the electrochemical performance have been discussed in detail. [Copyright &y& Elsevier]

Abstract: Rod-like orthorhombic LiMnO2 nanocrystals were successfully synthesized using temperature-controlled microwave hydrothermal route (TCMH) in a short time (30min) at a temperature as low as 160°C. o-LiMnO2 obtained by two different methods was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrochemistry test. SEM revealed that the product obtained in case of TCMH was rod-like with a diameter of 40nm, while the nanoparticles with 200nm diameter were obtained by traditional hydrothermal route (TH). The dramatic formation of o-LiMnO2 in the microwave hydrothermal field influenced the morphology and crystal structure of the final products. The formation and preferred growth orientation mechanism of o-LiMnO2 in the microwave irradiation process was discussed. Electrochemistry performance exhibited that the as-synthesized o-LiMnO2 nanorods reached the maximum discharge capacity of 194.2mAhg−1 at 0.1C rate after several cycles between 2.2 and 4.4V vs. Li+/Li at room temperature, which was higher than the electrochemical performance of o-LiMnO2 obtained by TH. The experimental results showed that the TCMH method provided an effective way for preparing o-LiMnO2 cathode material in lithium-ion batteries. [Copyright &y& Elsevier]

Abstract: Monoclinic Li3V2(PO4)3 can be rapidly synthesized at 750°C for 5min (MW5m) by using microwave solid-state synthesis method. The refined cell parameters and atomic coordination of the sample MW5m show some deviations compared with those of the sample synthesized in conventional solid-state synthesis method, especially the coordinate of Li atoms. Compared with the electrochemical properties of the carbon-coating sample Li3V2(PO4)3, the carbon-free sample MW5m presents well electrochemical properties. In the cut-off voltage of 3.0–4.3V, MW5m sample presents a specific charge capacity of 132mAhg−1, almost equivalent to the reversible cycling of two lithium ions per Li3V2(PO4)3 formula unit (133mAhg−1), and specific discharge capacity of 126.4mAhg−1. In the cut-off voltage of 3.0–4.8V, MW5m shows an initial specific discharge capacity of 183.4mAhg−1 at 0.1C, near the theoretical discharge capacity. In the cycle performance, the capacity fade of Li3V2(PO4)3 is dependent on the cut-off voltage and the preparation method, more capacity lost at relatively higher charge/discharge voltage. The reasons for the excellent electrochemical properties of Li3V2(PO4)3 rapidly synthesized in microwave field are discussed in detail. [Copyright &y& Elsevier]