The rechargeable lithium-ion cell is an advanced energy-storage system. However, high cost, safety hazards, and chemical instability prohibit its use in large-scale applications. An alternative cathode material, LiFePO(4), solves these problems, but has a kinetic problem involving strong electron/hole localization. One reason for this is believed to be the limited carrier density in the fixed monovalent Fe(3+)PO(4)/LiFe(2+)PO(4) two-phase electrode reaction in LixFePO4. Here, we provide experimental evidence that LixFePO4, at room temperature, can be described as a mixture of the Fe(3+)/Fe(2+) mixed-valent intermediate LialphaFePO4 and Li1-betaFePO4 phases. Using powder neutron diffraction, the site occupancy numbers for lithium in each phase were refined to be alpha=0.05 and 1-beta=0.89. The corresponding solid solution ranges outside the miscibility gap (0

A huge kinetic difference in olivine Li x MPO 4 (M ϭ Fe,Mn) is demonstrated in a quantitative manner. Galvanostatic discharge profiles and the current relaxation to the stepwise anodic overvoltage ͑chronoamperometry͒ are comparatively measured for the Li x FePO 4 and Li x MnPO 4 under identical extrinsic conditions, which are carefully controlled and confirmed using Rietveld refinement for the X-ray diffraction profiles, direct texture observation by scanning electron microscope, Brunauer-Emmett-Teller surface area measurements, and tap density measurements. The current durability for Li x MnPO 4 is orders-of-magnitude inferior to that of Li x FePO 4 , the origin of which is clearly attributed to their intrinsic crystallographic and transport property differences. Heavy polaronic holes localized on the Mn 3ϩ sites are suggested as an important rate-limiting factor. In spite of the higher open-circuit voltage of Mn 3ϩ /Mn 2ϩ ͑4.05 V͒ compared to that of Fe 3ϩ /Fe 2ϩ ͑3.45 V͒ in the olivine framework, the abnormally large polarization may eliminate pure LiMnPO 4 as a practical lithium battery cathode due to much lower effective energy density than LiFePO 4 .

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Release of alkali and alkaline earth metallic (AAEM) species was examined during pyrolysis of pulverized pine and sugarcane bagasse. The use of a wire-mesh reactor enabled the investigation of the primary release of AAEM species from pyrolyzing particles suppressing secondary interaction between them. Upon heating the pine at 1000°C s -1 up to 800°C, 15-20% of each AAEM species was released during the tar evolution and afterward. Further isothermal heating caused nearly complete release of alkalis within 150 s, while the release of alkaline earths terminated at levels of 20-40%. Heating the pine at 1°C s -1 up to 800°C brought about the release of AAEM species mainly after the tar evolution. Chlorides of AAEM species were found to be very minor volatiles over the range of conditions. Variations in K release with operating variables were reasonably explained by considering that elemental K volatilized from the charbonded AAEM species was a major volatile K species. None of AAEM species were significantly released when a fixed bed of the pine was heated at 1°C s -1 up to 900°C without forced gas flow through the bed. It was suggested that repeated desorption from and adsorption onto the char surface within the fixed bed inhibited the release of AAEM species from the fixed bed and resultantly allowed them to transform into thermally stable char-bonded ones and/or nonvolatiles such as silicates.

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A series of synthetic heterosite-purpurite, (Mn y Fe 1-y )PO 4 (y < 0.8), with negligible disorder and impurities, was obtained by chemical oxidation of the well-crystallized isotypic tryphillite-lithiophilite series, Li(Mn y Fe 1-y )PO 4 (ordered olivine structure, space group Pnma). Comparative magnetic and X-ray/ neutron powder diffraction investigations of the two solid-solution lines were performed as a function of Mn content to increase understanding of the electrochemical activity loss of Mn 3+ /Mn 2+ in the Li x (Mn y Fe 1-y )PO 4 electrode system. Introducing Mn ions into the 4c site did not cause significant change in the local geometry of M 2+ O 6 and PO 4 polyhedra, while the M 3+ O 6 octahedra became severely distorted with an increase in the number of Jahn-Teller active Mn 3+ ions. The edge-sharing geometry of M 3+ O 6 and PO 4 polyhedra fixed the shared O3′-O3′ interatomic distance, causing selective strong elongation of the M 3+ -O3′ distance with small shrinkage of other M 3+ -O1, M 3+ -O2, and M 3+ -O3 bond lengths. The overall distortion of the MO 6 octahedra with M ) Mn 3+ was much larger than the corresponding change in the unit-cell orthorombicity and significantly increased asymmetry in the M-O-M superexchange interaction. All samples exhibited antiferromagnetism; however, the trivalent series had more than a sevenfold larger decrease in Neel temperature T N (from ca. 130 K at y ) 0 to ca. 50 K at y ) 0.8) compared to the divalent series (from ca. 52 K at y ) 0 to ca. 35 K at y )1) as a function of the Mn content y.

Structural changes at electrode/electrolyte interface of a lithium cell were studied by X-ray reflectometry and two-dimensional model electrodes with a restricted lattice plane of LiMn 2 O 4 . The electrodes were constructed with an epitaxial film synthesized by the pulsed laser deposition method. The orientation of the film depends on the substrate plane; the ͑111͒, ͑110͒, and ͑100͒ planes of LiMn 2 O 4 grew on the ͑111͒, ͑110͒, and ͑100͒ planes of the SrTiO 3 substrates, respectively. The ex situ reflectometry indicated that a thin impurity layer covered the lattice plane of the as-grown film. The impurity layer was dissolved and a solid-electrolyteinterface-like phase appeared after the electrode was soaked into the electrolyte. A defect layer was formed in the ͑111͒ plane, whereas no density changes were detected for the other lattice planes. The in situ observation clarified that the surface reactivity depended on the lattice planes of the spinel; the defect layer at the ͑111͒ plane was stable during the electrochemical reaction, whereas a slight decrease in the film thickness was observed for the ͑110͒ plane. Our surface characterization of the intercalation electrode indicated that the surface structure changes during the pristine stage of the change-discharge processes and these changes are dependent on the lattice orientation of LiMn 2 O 4 .Because the lithium-ion configuration composed of carbon anodes and intercalation cathodes has been widely accepted for lithium secondary batteries, significant efforts have been devoted to attain high energy and power densities to produce an excellent energy storage system. 1 In particular, recent progress in pure electric vehicles ͑EVs͒ and hybrid electric vehicles ͑HEVs͒ require high power density operation for the current battery systems. The power characteristics of the battery system are closely related to the nature of electrode reactions, which is composed of several reaction steps proceeded in series: lithium diffusion in the electrolyte, adsorption of solvated lithium on the cathode surface, desolvation, surface diffusion, charge-transfer reaction, intercalation from the surface to the bulk, and the bulk diffusion of lithium in the electrode material. Recent electrochemical studies have claimed that the desolvation process was the rate-determining step of the whole electrode reaction. 2,3 It is well known that electrode surfaces are almost covered with a passive surface layer, which is generally called the solid electrolyte interface ͑SEI͒. The idea of the SEI layer was originally introduced on the alkali and alkaline earth metal in organic electrolytes, 4 and then it is believed that the layer plays a key role in the electrochemical performance, particularly the calendar life of lithium batteries. Many experimental techniques such as X-ray photoelectron spectroscopy ͑XPS͒, 5-8 IR spectroscopy, 9,10 nuclear magnetic resonance ͑NMR͒, 11 and ellipsometry 12 have been employed to study the nature and formation mechanism of the SEI layer.Among the materials prop...

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