James H. Miners

LiMn0.8Fe0.2PO4: An Advanced Cathode Material for Rechargeable Lithium Batteries†

Keywords: cathode materials ; lithium batteries ; nanoparticles ; surface chemistry ; thermal stability ; Performance ; Electrodes Reference EPFL-ARTICLE-159236doi:10.1002/anie.200903587View record in Web of Science Record created on 2010-11-30, modified on 2017-05-12

Improving the Electrochemical Activity of LiMnPO4 Via Mn-Site Substitution

HPL SA report the modification of the electrochemical performance of lithium manganese phosphate (LiMnPO4) via Mn-site bivalent substitution. Manganese (10%) is substituted with iron, nickel, magnesium, or zinc. These substituents are shown via an X-ray to form solid solutions. The choice of substituent is demonstrated to have a strong influence on the electrochemical performance. The optimum performance improvement was achieved when 10% of Fe is substituted. This is ascribed to a smaller crystallite and a higher electronic conductivity observed in this material: Presumably Fe plays a role in hindering the crystallite growth and in increasing the carriers transportation. Electronic structures were calculated by density function theory to understand the different influences of substitute cations.

On the Thermal Stability of Olivine Cathode Materials for Lithium-Ion Batteries

The thermal stability of pristine and electrochemically delithiated LiMPO4 (Carbon coated-LiMnPO4, Carbon coated-LiMn0.8Fe0.2PO4, and Carbon coated-LiFePO4), LiCoO2 and LiNi0.8Co0.15Al0.05O2 (NCA) composite electrodes with LiPF6 solutions in ethylene carbonate (EC)/dimethyl carbonate (DMC) and EC/propylene carbonate (PC), was investigated by differential scanning calorimetry (DSC) and thermogravimetric analysis, coupled with mass spectrometry. The thermal reactions products were measured by XRD and electron microscopy. The LiFePO4 and LiMnPO4 cathode materials were found to have comparable thermal stability in their pristine and fully delithiated states. The onset temperatures of the thermal reactions are lower in EC/DMC than in EC/PC solutions but the specific heat evolution of all the thermal reactions are higher with EC-PC solutions. No evidence was found that delithiated LiMnPO4 or Li[MnFe]PO4 have lower thermal stability than delithiated LiFePO4. The thermal reactivity of the layered LiCoO2 and LiNi0.8Co0.15Al0.05O2 cathode materials was found to be comparable to that of the LiMPO4 materials. Oxygen release was detected from the layered compounds upon their heating around 200°C.

Li4Ti5O12/LiMnPO4 Lithium-Ion Battery Systems for Load Leveling Application

A new type of lithium-ion cell based on the combination of spinel Li4Ti5O12 anode with a high voltage olivine LiMnPO4 cathode, which can be promising for load leveling applications, is demonstrated for the first time. The power and safety characteristics of this battery system were found to meet the requirement for this application. The structure, surface morphology, and the performance were characterized by X-ray diffraction (XRD), high-resolution scanning electron microscopy (HRSEM) and standard electrochemical techniques. A stable reversible capacity up to 125 mAh g � 1 of the cathode in full cell could be measured at discharge potentials >2.5 V with a reasonable capacity retention during prolonged charge/discharge cycling. The thermal stability of pristine and electrochemically delithiated LiMnPO4-Li4Ti5O12 composite cathodes and anodes in contact with the electrolyte solution was investigated by differential scanning calorimetry (DSC). The electrodes were also studied by thermogravimetric analysis, coupled with mass spectrometry. We did not found appreciable changes in the thermal stability of the electrodes in their pristine and charged states, in contact with LiPF6 solution in mixtures of ethylene carbonate (EC) and dimethyl carbonate (DMC).