The cathode/electrolyte interface stability is the key factor for the cyclic performance and the safety performance of lithium ion batteries. Suppression of consuming key elements in the electrode materials is essential in this concern. In this purpose, we investigate a facile strategy to solve interfacial issue for high-voltage lithium ion batteries by adding an oxidable fluorinated phosphate, Bis(2,2,2-trifluoroethyl) Phosphite (BTFEP), as a sacrificial additive in electrolyte. We demonstrate that BTFEP additive could be oxidized at slightly above 4.28 V which is a relatively lower voltage than that of solvents, and the oxidative products facilitate in-situ forming a stable solid electrolyte interphase (SEI) film on the cathode surface. The results manifest the SEI film validly restrains the generation of HF and the interfacial side reaction between high-voltage charged LiNi0.5Mn1.5O4 (LNMO) and electrolyte, hence, the dissolution of Mn and Ni is effectively suppressed. Finally, the cyclic performance of LNMO after 200 cycles was remarkably improved from 68.4% in blank electrolyte to 95% in 1 wt% BTFEP-adding electrolyte.

Micro-sized porous LiMnPO4 nanoflakes constituted by interconnected small-sized LiMnPO4 nanocrystals were synthesized using the novel precursor of (C2N2H10)Mn2(PO4)2·2H2O nanosheets through a facile process. After carbon coating, the LiMnPO4–C presents promising electrochemical properties. The strategy described in this work could be helpful for practical applications of LiMnPO4.

•High voltage cycle performance of the cell is improved by using TPP in electrolyte.•TPP is an effective additive to in situ form a SEI film on cathode.•Electrochemical measurement proved the preferable oxidization of TPP than solvent.•SEM and TEM proved a continuous SEI film was in situ formed on cathode.The cathode/electrolyte interface stability is the key factor for the cycle life and the safety performance of lithium-ion battery. Triphenylphosphine(TPP) is studied as an additive for film-formation on the cathode electrode. TPP additive can be preferably oxidized than the solvent and then a solid electrolyte interphase (SEI) layer is in-situ formed on the cathode surface and it greatly improves the cycle stability of the cathode at high voltage. The capacity retention for the LiMn2O4 cathode, which is cycled up to 4.8 V, is improved from 82% in the blank electrolyte to 93% in the TPP-containing electrolyte after 100 times at the current density of 148 mA/g(1C).

•LiMn1-xFexPO4-C cathode materials were prepared from MnPO4·H2O.•Fe2+ doping was realized by solid-state diffusion at high temperature.•The capacity of LiMn0.7Fe0.3PO4-C reached 140 mAh g-1.We synthesize LiMn1 − xFexPO4-C cathode materials using MnPO4·H2O particles as the precursor. The substitution of Mn2 + with Fe2 + is successfully conducted by the diffusion of Fe2 + after the formation of LiMnPO4. Control experiment confirms that there exists a diffusion of Fe2 + and Mn2 + when LiMnPO4 contacts with LiFePO4 at high temperature. The obtained LiMn0.7Fe0.3PO4-C cathode material has a capacity of 140 mAh/g and good rate performance.

Micrometer LiMn0.7Fe0.3PO4–C particles consisting of nanopores are prepared using MnPO4·H2O as the precursor. The nanopores were formed by the thermal decomposition of the precursor. Fe doping and carbon coating were realized in one step during the heat treatment. Polyethylene glycol (PEG) was used as the carbon source and milled with the other precursor to form the carbon coating throughout the whole micrometer particle sample. Due to the short ion transportation distance of the active materials caused by the nanopores, the composite displays high discharge capacity, and good rate capability and cycle stability. With only 4% carbon, the capacity of LiMn0.7Fe0.3PO4–C reaches 132 mA h g−1 under the galvanostatic charge–discharge mode, and 140 mA h g−1 under the constant current–constant voltage (CC–CV) charge mode.

Micro-sized porous LiMnPO4 nanoflakes constituted by interconnected small-sized LiMnPO4 nanocrystals were synthesized using the novel precursor of (C2N2H10)Mn2(PO4)2·2H2O nanosheets through a facile process. After carbon coating, the LiMnPO4–C presents promising electrochemical properties. The strategy described in this work could be helpful for practical applications of LiMnPO4.