•An iron-assisted carbon coating strategy is developed for uniform and highly graphitized carbon.•The Fe atoms contributed to formation of uniformly carbon coating on LMFP.•The resulting LMFP/Fe/C exhibits excellent electrochemical performance.An iron-assisted carbon coating strategy is developed to guide the formation of uniform and highly graphitized carbon layers on surfaces of the LiMn0.8Fe0.2PO4 (LMFP) to yield cathode materials with improved electrochemical performance. A small amount of iron oxalate is added as a catalyst precursor, which decomposes into ferrous oxide (FeO) at high temperature. During the calcination process, FeO is reduced to iron (Fe) that helps to transform amorphous carbon into graphitized carbon which is deposited uniformly and tightly on surfaces of LMFP materials. The impact of Fe atoms on the formation of highly graphitized carbon layers as well as the electrochemical performances of the resulting LMFP/Fe/Carbon (LMFP/Fe/C), is evaluated. Compared to LMFP/C without iron oxalate, LMFP/Fe/C exhibited substantial discharge capacity and better rate and cycling performances. Discharge capacities of 152.3, 141.9, 132.1, 105.6 and 76.0 mAh g−1 are recorded at 0.2, 0.5, 1, 5 and 10 C, respectively. The retention capacity remained 78.6% at 10 C after 60 cycles. Furthermore, the conductivity and the lithium ion diffusion processes of LMFP/Fe/C are improved.The schematic preparation of the LMFP/Fe/C.

The well-distribution spindle LiFePO4 (LFP) nanoparticles as cathode of lithium secondary batteries were synthesized by a solvothermal reaction route at low temperature (180 °C) in which the ascorbic acid was used as reducing agent. In order to guarantee that the pH values of thermal systems were not affected too much and the reducibility of the system was enhanced at the same time, glucose was chosen as an auxiliary reductant in this reaction. The obtained powders were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and laser particle analyzer. The results show that the carbon-coated uniform spindle olivine LiFePO4/C-glucose particles (glucose as auxiliary reductant, LFP/C-G) are prepared with the size 500–600 nm and without any impurity phases. Their electrochemical properties were evaluated by electrochemical impedance spectroscopy, cyclic voltammetry, and galvanostatic charge/discharge tests. LFP/C-G has a higher conductivity and better reversible capability than carbon-coated LFP (LFP/C). The highest discharge capacity of LFP/C-G is 161.3 mAh·g−1 at 0.1C and 108.6 mAh·g−1 at 5.0C, respectively. The results imply that the neat crystal nanostructure of LFP/C-G has excellent capacity retention and cycling stability. The adding of glucose is the key factor for the well-distribution and neat crystal structure of nanoparticles, thus the electrochemical performances of materials are improved.

•Graphene–LiMn0.8Fe0.2PO4/C composite was synthesized via solvothermal method.•Adding of a tiny amount graphene enhances electrochemical performances of LiMnPO4.•Property enhancement depends on high surface area and conductivity of graphene.The high energy density graphene–LiMn0.8Fe0.2PO4/C(graphene–LMFP/C) composite material with ordered olivine structure was synthesized in 5:3(v/v) ethylene glycol–water mixed solvent in the presence of ascorbic acid/glucose as the reducing agent at 240 °C for 4 h. The crystalline structure, morphology, micro-structure and particle size were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM). Its electrochemical properties were also studied. Because of the addition of graphene, the material exhibits high discharge capacity, good rate performance and high cycling stability. It delivers an initial discharge capacity of 160 mAh g−1 at 0.05C, which is 94.2% of the theoretical value of 170 mAh g−1. It also delivers excellent rate property, achieving a discharge capacity of 156, 123 and 106 mAh g−1 at 0.1C, 5C and 10C at 25 °C. Moreover, it has good cycling stability, it retains 92.9% of the initial capacity over 80 cycles at 1C, which are comparable to carbon-coated LiMn0.8Fe0.2PO4/C (LMFP/C). The better cycling stability of graphene–LMFP/C is believed to be associated with the using of graphene.

Polyaniline(PANI) micro/nanotubes doped with novel dopant acid mordant dark yellow GG (AMY GG) were prepared by soft template method in the presence of ammonium persulfate (APS) as an oxidant. It was found that the molar ratio of HCl to aniline and washing method of the products played key roles in the formation of PANI micro/nanotubes. Changing the molar ratio of HCl to aniline, the typical morphology of PANI could be changed from nanotubes to microtubes. In order to get the final product, different solvents were tried to wash away the by-products. After the by-products were removed by water/methonal/ether, the PANI micro/nanotubes appeared. The morphology of PANI micro/nanotubes was confirmed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The chemical structure and thermal stability of PANI micro/nanotubes were examined by Fourier transform infrared (FT-IR) spectra, X-ray diffraction (XRD) and the thermogravimetric analysis (TGA). The formation mechanism of PANI micro/nanotubes was also discussed.

A soft template method for fabrication of polyaniline (PANI) microtubes is presented in this paper. It was found that methyl orange in acidic solution can be effectively self-assembled into supramolecular aggregates like flake and dendrite and they were used as soft templates to prepare PANI microtubes in the present of aniline monomer and ammonium peroxydisulfate. The morphology and chemical structure of the PANI microtubules were characterized by means of transmission electron microscopy, scanning electron microscopy, Fourier transformed infrared spectra, UV–vis absorption spectra (UV–vis) and elemental analysis. The results showed prepared PANI microtubes were in conductive emeraldine state.