Improving the cycling stability and rate capability of LiMn_(0.5)Fe_(0.5)PO_(4)/C nanorod as cathode materials by LiAlO_(2) modification

LiMn_(0.5)Fe_(0.5)PO_(4)(LMFP)@C and LMFP@LiAlO_(2)@C nanorods are successfully synthesized by a solvothermal process followed by a calcination at H2/Ar atmosphere.The carbon coating and LiAlO_(2) coating does not change the morphology and particle size of LMFP,and all samples show nanorod morphology with 50-100 nm in width and 200-300 nm in length.The results show that LiAlO_(2) coating can offer rapid charge transfer channels with improved intercalation/de-intercalation kinetics of Li ions,which make an outstanding rate capability and cycling stability of as-synthesized LMFP@LiAlO_(2)@C cathodes.As a result,LiAlO_(2) coating effectively improves the rate capability and cycling stability of LMFP cathode even at high discharge rates.Hence,LMFP@LiAlO_(2)(5 wt%)@C indicates an outstanding rate performance with a reversible discharge capacity of 137.6 and 113.2 mAh g^(-1) discharged at 0.05 C and 5 C rates,and the composite also shows a good cycle performance with an excellent capacity of 107 mAh g^(-1) and 86.4% capacity retention rate at 5 C rate after 100 cycles.Therefore,the LiAlO_(2) coating can be considered as an effective way to improve the electrochemical properties of LMFP.

Progressive steps and catalytic cycles in methanol-to-hydrocarbons reaction over acidic zeolites

Understanding the complete reaction network and mechanism of methanol to-hydrocarbons remains a key chal-lenge in the field of zeolite catalysis and C1 chemistry.Inspired by the identification of the reactive surface methoxy species on solid acids,several direct mechanisms associated with the formation of the first C-C bond in methanol conversion have been recently disclosed.Identifying the stepwise involvement of the initial intermedi-ates containing the first CC bond in the whole reaction process of methanol to-hydrocarbons conversion becomes possible and attractive for the further development of this important reaction.Herein,several initial unsaturated aldehydes/ketones containing the C-C bond are identified via complementary spectroscopic techniques.With the combination of kinetic and spectroscopic analyses,a complete roadmap of the zeolite catalyzed methanol-to-hydrocarbons conversion from the initial CC bonds to the hydrocarbon pool species via the oxygen-containing unsaturated intermediates is clearly ilustrated.With the participation of both Bronsted and Lewis acid sites in H-ZSM-5 zeolite,an initial aldol-cycle is proposed,which can be closely connected to the well-known dual-cycle mechanism in the methanol-to-hydrocarbons conversion.