Synthesis Of LiMn0 Research Articles

New Insights into the Chemistry of the Hydrothermal Synthesis of Olivine Lithium Metal Phosphates

AbstractThe effect of alkali ions (Na+ and K+) on the hydrothermal synthesis of olivine lithium metal phosphates in the P excess system was investigated by taking the synthesis of LiMn0.8Fe0.19Mg0.01PO4 as a case study. It is found that the coexisting Na+ can compete with Li+ to partly form NaMnPO4 as an impurity when the Na+/Li+ ratio exceeds the critical value, and this is not the case for the coexisting K+. These behaviors should be related to the difference in the ionic size of the alkali ions which also leads to a very different process of LiMn0.8Fe0.19Mg0.01PO4 formation. The samples derived from the K+‐coexisting reaction system can deliver much higher reversible capacities as compared with the sample derived from the Na+‐coexisting reaction system. This study provides new insights into the chemistry of the hydrothermal synthesis of olivine lithium metal phosphates, with an important implication for controllable synthesis and property manipulation.

Synthesis of Cathode Active Material LiMn0.5Fe0.5PO4F/C with Sintering Time Variation

Research has been carried out on the synthesis of LiMn0.5Fe0.5PO4F/C, the cathode active materials with variations in sintering time. The process of producing the LiMn0,5Fe0,5PO4F/C as an active material in lithium battery cathodes has been successfully carried out by the first forming host structure and then infiltrating the lithium Li ions and the flour F ions. In this study, the synthesis was carried out with various sintering time, 6 hours, 8 hours and 10 hours. The raw materials used in this study are manganese dioxide (“MnO2”), iron (III) oxide (“Fe2O3”), lithium fluoride (“LiF”) and phosphoric acid (“H3PO4”) as the solvents. The synthesis was carried out at a calcination temperature of 720°C for 8 hours. The first mashed use a milling process for about 180 minutes, and placed into the oven, then mashed using a mortar. Then the Mn0.5Fe0.5PO4 sample was added with LiF, mixed with the milling process, placed into a drying oven and was varied with the sintering time of 6 hours for the first sample, 8 hours for the second sample and 10 hours for the third sample. As to produce LiMn0.5Fe0.5PO4F material, followed by carbon coating, namely tapioca and sugar (8%:4%). All three samples were calcined at a temperature of 720°C for 4 hours. The results of XRD analysis showed that the three samples did not experience a phase of change, however only shows a few differences in intensity. The results of FESEM analysis show that grain growth occurs vertically and horizontally due to the presence of the Mn and Fe, and with an exact enough amount of tapioca function as a carbon source to coat the active material, it help to creates pores in the powder so that the presence of these pores could provide an intercalation pathway for the lithium ions. At the end the results of the EIS analysis showed that the highest conductivity value of this study was 0.62 x 10-5 S/cm.

Facile synthesis of LiMn0·75Fe0·25PO4/C composite cathode material and electronic conductivity of carbon coating

LiMn0·75Fe0·25PO4/C powders were prepared by a facile hydrothermal and ball-milling method, and then calcined. X-ray diffraction and scanning electron microscopy revealed that the calcination temperature had a strong effect on the structure and morphology of the as-prepared powder, and thus, on the subsequent electrochemical performance of the material. When the calcination temperature was increased from 550 to 700°C, the grain size of LiMn0·75Fe0·25PO4/C increased greatly. The electronic conductivities of the carbon coatings, which were obtained from sucrose and calcined at 550 and 700°C, were investigated. The discharge capacities of LiMn0·75Fe0·25PO4/C decreased with increasing calcination temperature, but electrochemical impedance spectroscopy showed that the charge-transfer resistances of LiMn0·75Fe0·25PO4/C electrodes decreased owing to the increase in the electronic conductivity of the carbon coating. Grain growth played a more important role than the electronic conductivity of the carbon coating in the discharge capacity of the electrode. The powder calcined at 550°C exhibited the best electrochemical performance, with a discharge capacity of 131·9 mAh g−1 at a rate of 0·1 C.

Synthesis of LiMn0.8Fe0.2PO4 Mesocrystals for High-Performance Li-Ion Cathode Materials

The micron-sized LiMn0.8Fe0.2PO4 (LMFP) mesocrystals with high volumetric density were successfully synthesized via a solvothermal method. The LMFP mesocrystals, composed of ∼30-nm-sized nanocrystallites, exhibit a high tap density of ∼1.2g/cm3. The synthesis of such nano-sized crystals was rendered by ascorbic acid which serves as surface-energy modifier. Interestingly, the ascorbic acid also directed the primary nanocrystals to anisotropic aggregations, and the growth mechanisms were rationally identified by TEM and x-ray diffraction. For reversible Li insertion/extraction, the interconnected particles within the mesocrystals were coated by conductive carbon, and the enhancement of the electrochemical properties (i.e. high specific capacity and good rate capability) was assessed by galvanostatic cycling. We believe that this work provides one of the routes to design electrochemically-favorable meso/nano-structures, which is of great potential for improving the battery performance by tuning the morphology of particles at the multi-length scale.

Synthesis LiMn0.7Fe0.2Ni0.1PO4 and Carbon Coating with Cassava Powder and Citric Acid as Carbon Source

Synthesis of LiMn0.7Fe0.2Ni0.1PO4 was carried out by using powder metallurgy method with stoichiometric composition of technical raw materials: MnO2 and Fe2O3 from China, Ni from Merck, H3PO4 and LiOH.H2O from Germany. The powder was milled with tapioca powder under comparison between tapioca and active material 1:7, 1:8, 1:9 for one hour and heated again at 800°C in two hours under nitrogen gasses. The produced powder had black color under coated carbon and had crystal structure of olivine Lithiophilite. The conductivity was around 0.4 S/cm while its capacity was around 5 Amh/g.

Synthesis of LiMn0.9Ni0.1PO4/C as New Cathode Material for Lithium Battery

<p>Lithium ion battery has high energy density and good application for electrical vehicle and power grid under combination with photovoltaic. Carbon coated lithium manganese phosphate is the new cathode active material. In this experiment LiMn0.9Ni0.1PO4\C was carried out with stoichiometric composition of technical raw materials, MnO2 from China, Ni from Merck, H3PO4 and LiOH.H2O from Germany. After calcinations process at 7000C in 2 hours by powder metallurgy method, sintering was done during of 2 hours. Before sintering process calcinations powder was milled and mixed with tapioca powder under comparison between tapioca and active material 1:3 in 72 hours. The sintered powders was analyzed the characteristic of crystal structure, SEM, conductivity, cyclic voltammeter and charge – discharge. The sintered powder has black color under coated carbon from tapioca. The crystal structure of LiMn0.9Ni0.1PO4\C has the same olivine structure of LiMnPO4\C. Networking structure of phosphate in LiMn0.9Ni0.1PO4\C was formed in the FTIR analysis. Conductivity of active material was 7.96 x 10-6 S/cm. Workings voltage of LiMn0.9Ni0.1PO4\C was 4.2 volt with capacity of round 40mAh/g. </p><p><strong>Keywords</strong>: <em>cathode, LiMnPO4, lithium battery, powder metallurgy, tapioca</em></p>

Synthesis of LiMn0.8Fe0.2PO4/C by co-precipitation method and its electrochemical performances as a cathode material for lithium-ion batteries

A nano-crystalline LiMn0.8Fe0.2PO4/C composite cathode material for lithium-ion batteries was prepared by a co-precipitation method. A precursor Mn0.8Fe0.2C2O4·2H2O was prepared by using an oxalic acid solution as the precipitator. And the final product LiMn0.8Fe0.2PO4 was in the size of about 30–50 nm, coated by a 2–3 nm carbon layer. The electrochemical performance tests indicated that this type of composite had excellent electrochemical performance, with an initial discharge capacity of 151.1 mAh g−1 at 0.1 C and 148 mAh g−1 for the 60th cycle. The composite showed a wonderful rate performance with 98.4 and 82 mAh g−1 at 5 C and 10 C rates, respectively.