Electronically conductive phospho-olivines as lithium storage electrodes

Coaxial MnO2/carbon nanotube array electrodes for high-performance lithium batteries

Coaxial manganese oxide/carbon nanotube (CNT) arrays deposited inside porous alumina templates were used as cathodes in a lithium battery. Excellent cyclic stability and capacity of MnO2/CNT coaxial nanotube electrodes resulted from the hybrid nature of the electrodes with improved electronic conductivity and dual mechanism of lithium storage. The reversible capacity of the battery was increased by an order compared to template grown MnO2 nanotubes, making them suitable electrodes for advanced Li ion batteries.

Structural and Electrochemical Characterization of PureLiFePO4and Nanocomposite C-LiFePO4Cathodes for Lithium Ion Rechargeable Batteries

Pure lithium iron phosphate (LiFePO4) and carbon-coatedLiFePO4(C-LiFePO4) cathode materials were synthesized for Li-ion batteries. Structural and electrochemical properties of these materials were compared. X-ray diffraction revealed orthorhombic olivine structure. Micro-Raman scattering analysis indicates amorphous carbon, and TEM micrographs show carbon coating onLiFePO4particles. Ex situ Raman spectrum of C-LiFePO4at various stages of charging and discharging showed reversibility upon electrochemical cycling. The cyclic voltammograms ofLiFePO4and C-LiFePO4showed only a pair of peaks corresponding to the anodic and cathodic reactions. The first discharge capacities were 63, 43, and 13 mAh/g for C/5, C/3, and C/2, respectively forLiFePO4where as in case of C-LiFePO4that were 163, 144, 118, and 70 mAh/g for C/5, C/3, C/2, and 1C, respectively. The capacity retention of pureLiFePO4was 69% after 25 cycles where as that of C-LiFePO4was around 97% after 50 cycles. These results indicate that the capacity and the rate capability improved significantly upon carbon coating.

Stamped microbattery electrodes based on self-assembled M13 viruses

The fabrication and spatial positioning of electrodes are becoming central issues in battery technology because of emerging needs for small scale power sources, including those embedded in flexible substrates and textiles. More generally, novel electrode positioning methods could enable the use of nanostructured electrodes and multidimensional architectures in new battery designs having improved electrochemical performance. Here, we demonstrate the synergistic use of biological and nonbiological assembly methods for fabricating and positioning small battery components that may enable high performance microbatteries with complex architectures. A self-assembled layer of virus-templated cobalt oxide nanowires serving as the active anode material in the battery anode was formed on top of microscale islands of polyelectrolyte multilayers serving as the battery electrolyte, and this assembly was stamped onto platinum microband current collectors. The resulting electrode arrays exhibit full electrochemical functionality. This versatile approach for fabricating and positioning electrodes may provide greater flexibility for implementing advanced battery designs such as those with interdigitated microelectrodes or 3D architectures.

Spinel LiMn2O4 nanorods as lithium ion battery cathodes

Spinel LiMn2O4 is a low-cost, environmentally friendly, and highly abundant material for Li-ion battery cathodes. Here, we report the hydrothermal synthesis of single-crystalline beta-MnO2 nanorods and their chemical conversion into free-standing single-crystalline LiMn2O4 nanorods using a simple solid-state reaction. The LiMn2O4 nanorods have an average diameter of 130 nm and length of 1.2 microm. Galvanostatic battery testing showed that LiMn2O4 nanorods have a high charge storage capacity at high power rates compared with commercially available powders. More than 85% of the initial charge storage capacity was maintained for over 100 cycles. The structural transformation studies showed that the Li ions intercalated into the cubic phase of the LiMn2O4 with a small change of lattice parameter, followed by the coexistence of two nearly identical cubic phases in the potential range of 3.5 to 4.3 V.

Experimental visualization of lithium diffusion in LixFePO4

Chemical energy storage using batteries will become increasingly important for future environmentally friendly ('green') societies. The lithium-ion battery is the most advanced energy storage system, but its application has been limited to portable electronics devices owing to cost and safety issues. State-of-the-art LiFePO4 technology as a new cathode material with surprisingly high charge-discharge rate capability has opened the door for large-scale application of lithium-ion batteries such as in plug-in hybrid vehicles. The scientific community has raised the important question of why a facile redox reaction is possible in the insulating material. Geometric information on lithium diffusion is essential to understand the facile electrode reaction of LixFePO4 (0<x<1), but previous approaches have been limited to computational predictions. Here, we provide long-awaited experimental evidence for a curved one-dimensional chain for lithium motion. By combining high-temperature powder neutron diffraction and the maximum entropy method, lithium distribution along the [010] direction was clearly visualized.

Dispersion properties of aqueous-based LiFePO4 pastes and their electrochemical performance for lithium batteries

Aqueous-based LiFePO(4) pastes to fabricate the cathode of lithium-ion battery were investigated with an emphasis on chemical control of suspension component interactions among LiFePO(4) particulates, carbon black, carboxymethyl cellulose (CMC), and poly(acrylic acid) (PAA). The dispersion properties of LiFePO(4) were characterized using electroacoustic, flow behavior and green microstructural observation. Correlation was made between the dispersion properties and electrochemical performance of the particles. It was found that the addition of PAA significantly decreases the viscosity of the LiFePO(4) paste. The decrease of viscosity leads to increasing the solid concentration, which affects the electrochemical properties. The electrochemical characteristics of formulated pastes were evaluated using coin-type half cells. Although there is no significant difference between coin cells fabricated with CMC only and CMC/PAA combination in electrochemical cycling test, the dispersion properties of pastes indicate that the electrode fabricated with CMC/PAA, potentially, has much improved discharge capacity compared to that with CMC alone because of the possibility to increase active mass portion in electrode paste.

Atomic-scale visualization of antisite defects in LiFePO4

We visualize the antisite exchange defects in LiFePO4 crystals with an ordered olivine structure by using annular dark-field scanning transmission electron microscopy (STEM). A recognizable bright contrast is observed in some of the Li columns of STEM images in a sample annealed at a lower temperature, which directly demonstrates the disordered occupations by Fe atoms. Furthermore, such exchange defects appear to be locally aggregated rather than homogeneously dispersed in the lattice, although their overall concentration is fairly low. The present study emphasizes the significance of atomic-level observations for the defect distribution that cannot be predicted by macroscopic analytical methods.