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 .

No abstract

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.