Thierry Drezen

LiMnPO4 as an Advanced Cathode Material for Rechargeable Lithium Batteries

LiMnPO4 nanoparticles synthesized by the polyol method were examined as a cathode material for advanced Li-ion batteries. The structure, surface morphology, and performance were characterized by X-ray diffraction, high resolution scanning electron microscopy, high resolution transmission electron microscopy, Raman, Fourier transform IR, and photoelectron spectroscopies, and standard electrochemical techniques. A stable reversible capacity up to 145 mAh g(-1) could be measured at discharge potentials > 4 V vs Li/Li+, with a reasonable capacity retention during prolonged charge/discharge cycling. The rate capability of the LiMnPO4 electrodes studied herein was higher than that of LiNi0.5Mn0.5O2 and LiNi0.8Co0.15Al0.05O2 (NCA) in similar experiments and measurements. The active mass studied herein seems to be the least surface reactive in alkyl carbonate/LiPF6 solutions. We attribute the low surface activity of this material, compared to the lithiated transition-metal oxides that are examined and used as cathode materials for Li-ion batteries, to the relatively low basicity and nucleophilicity of the oxygen atoms in the olivine compounds. The thermal stability of the LiMnPO4 material in solutions (measured by differential scanning calorimetry) is much higher compared to that of transition-metal oxide cathodes. This is demonstrated herein by a comparison with NCA electrodes

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

Enhanced Electrochemical Performance of Mesoparticulate LiMnPO4 for Lithium Ion Batteries

LiMnPO 4 was synthesized using a sol-gel method and tested as a cathode material for lithium ion batteries. After calcination at temperatures between 520 and 570°C particle sizes in the range of 140 to 160 nm were achieved. Subsequent dry ballmilling reduced the diameter to 130 ± 10 nm. Reversible capacities of 156 mAh/g at C/100 and 134 mAh/g at C/10 were measured. At 92 and 79% of the theoretical values, respectively, these are the highest values reported to data for this material. At faster charging rates, the electrochemical performance was found to be improved when smaller particles were used.

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).

Li Insertion into Li[sub 4]Ti[sub 5]O[sub 12] (Spinel)

Li 4 Ti 5 O 1 2 (spinel) materials were prepared with Brunauer-Emmett-Teller surface areas ranging from 1.3 to 196 m 2 /g. The corresponding average particle sizes varied from ca. 1 μm to ca. 9 nm. Twenty-five different materials were tested as Li insertion hosts in thin-film electrodes (2-4 μm) made from a pure spinel. Trace amounts of anatase in Li 4 Ti 5 O 1 2 were conveniently determined by cyclic voltammetry of Li insertion. Electrodes from nanocrystalline Li 4 Ti 5 O 1 2 exhibited excellent activity towards Li insertions even at charging rates as high as 250C. The charge capability at 50-250C was proportional to the logarithm of surface area for coarse particles (surface areas smaller than ca. 20 m 2 /g). With increasing charge/discharge rates, a narrowing plateau in performance was observed for materials with surface areas between ca. 20 to 100 m 2 /g. These materials can be charged/discharged nearly to the nominal capacity of L1 4 Ti 5 O 1 2 (175 mAh/g) within a wide range of the rates. Very small particles (surface areas > 100 m 2 /g) exhibit a growing decrease of charge capability at 50-250C. The Li-diffusion coefficients, calculated from chronoamperometry, decrease by orders of magnitude if the average particle size drops from ca. I μm to ca. 9 nm. However, the sluggish Li + transport in small particles is compensated by the increase in active electrode area. Materials having surface areas larger than ca. 100 m 2 /g also tend to show increased charge irreversibility. This could be caused by parasitic cathodic reactions, due to enhanced adsorption of reducible impurities (humidity) or the quality of the spinel crystalline lattice itself. The optimum performance of thin-film Li 4 Ti 5 O 1 2 electrodes is achieved, if the parent materials have surface areas between ca. 20 to 110 m 2 /g, with the maximum peak at 100 m 2 /g.Reference LPI-ARTICLE-2003-015doi:10.1149/1.1581262View record in Web of Science Record created on 2006-02-21, modified on 2017-05-12

Li Insertion into Li4Ti5 O 12 (Spinel) Charge Capability vs. Particle Size in Thin-Film Electrodes

Li 4 Ti 5 O 1 2 (spinel) materials were prepared with Brunauer-Emmett-Teller surface areas ranging from 1.3 to 196 m 2 /g. The corresponding average particle sizes varied from ca. 1 μm to ca. 9 nm. Twenty-five different materials were tested as Li insertion hosts in thin-film electrodes (2-4 μm) made from a pure spinel. Trace amounts of anatase in Li 4 Ti 5 O 1 2 were conveniently determined by cyclic voltammetry of Li insertion. Electrodes from nanocrystalline Li 4 Ti 5 O 1 2 exhibited excellent activity towards Li insertions even at charging rates as high as 250C. The charge capability at 50-250C was proportional to the logarithm of surface area for coarse particles (surface areas smaller than ca. 20 m 2 /g). With increasing charge/discharge rates, a narrowing plateau in performance was observed for materials with surface areas between ca. 20 to 100 m 2 /g. These materials can be charged/discharged nearly to the nominal capacity of L1 4 Ti 5 O 1 2 (175 mAh/g) within a wide range of the rates. Very small particles (surface areas > 100 m 2 /g) exhibit a growing decrease of charge capability at 50-250C. The Li-diffusion coefficients, calculated from chronoamperometry, decrease by orders of magnitude if the average particle size drops from ca. I μm to ca. 9 nm. However, the sluggish Li + transport in small particles is compensated by the increase in active electrode area. Materials having surface areas larger than ca. 100 m 2 /g also tend to show increased charge irreversibility. This could be caused by parasitic cathodic reactions, due to enhanced adsorption of reducible impurities (humidity) or the quality of the spinel crystalline lattice itself. The optimum performance of thin-film Li 4 Ti 5 O 1 2 electrodes is achieved, if the parent materials have surface areas between ca. 20 to 110 m 2 /g, with the maximum peak at 100 m 2 /g.Reference LPI-ARTICLE-2003-015doi:10.1149/1.1581262View record in Web of Science Record created on 2006-02-21, modified on 2017-05-12

Li Insertion into Li4Ti5O12 (Spinel)

Li 4 Ti 5 O 1 2 (spinel) materials were prepared with Brunauer-Emmett-Teller surface areas ranging from 1.3 to 196 m 2 /g. The corresponding average particle sizes varied from ca. 1 μm to ca. 9 nm. Twenty-five different materials were tested as Li insertion hosts in thin-film electrodes (2-4 μm) made from a pure spinel. Trace amounts of anatase in Li 4 Ti 5 O 1 2 were conveniently determined by cyclic voltammetry of Li insertion. Electrodes from nanocrystalline Li 4 Ti 5 O 1 2 exhibited excellent activity towards Li insertions even at charging rates as high as 250C. The charge capability at 50-250C was proportional to the logarithm of surface area for coarse particles (surface areas smaller than ca. 20 m 2 /g). With increasing charge/discharge rates, a narrowing plateau in performance was observed for materials with surface areas between ca. 20 to 100 m 2 /g. These materials can be charged/discharged nearly to the nominal capacity of L1 4 Ti 5 O 1 2 (175 mAh/g) within a wide range of the rates. Very small particles (surface areas > 100 m 2 /g) exhibit a growing decrease of charge capability at 50-250C. The Li-diffusion coefficients, calculated from chronoamperometry, decrease by orders of magnitude if the average particle size drops from ca. I μm to ca. 9 nm. However, the sluggish Li + transport in small particles is compensated by the increase in active electrode area. Materials having surface areas larger than ca. 100 m 2 /g also tend to show increased charge irreversibility. This could be caused by parasitic cathodic reactions, due to enhanced adsorption of reducible impurities (humidity) or the quality of the spinel crystalline lattice itself. The optimum performance of thin-film Li 4 Ti 5 O 1 2 electrodes is achieved, if the parent materials have surface areas between ca. 20 to 110 m 2 /g, with the maximum peak at 100 m 2 /g.Reference LPI-ARTICLE-2003-015doi:10.1149/1.1581262View record in Web of Science Record created on 2006-02-21, modified on 2017-05-12