Electronically conductive phospho-olivines as lithium storage electrodes

Single nanorod devices for battery diagnostics: a case study on LiMn2O4

This paper presents single nanostructure devices as a powerful new diagnostic tool for batteries with LiMn(2)O(4) nanorod materials as an example. LiMn(2)O(4) and Al-doped LiMn(2)O(4) nanorods were synthesized by a two-step method that combines hydrothermal synthesis of beta-MnO(2) nanorods and a solid state reaction to convert them to LiMn(2)O(4) nanorods. lambda-MnO(2) nanorods were also prepared by acid treatment of LiMn(2)O(4) nanorods. The effect of electrolyte etching on these LiMn(2)O(4)-related nanorods is investigated by both SEM and single-nanorod transport measurement, and this is the first time that the transport properties of this material have been studied at the level of an individual single-crystalline particle. Experiments show that Al dopants reduce the dissolution of Mn(3+) ions significantly and make the LiAl(0.1)Mn(1.9)O(4) nanorods much more stable than LiMn(2)O(4) against electrolyte etching, which is reflected by the magnification of both size shrinkage and conductance decrease. These results correlate well with the better cycling performance of Al-doped LiMn(2)O(4) in our Li-ion battery tests: LiAl(0.1)Mn(1.9)O(4) nanorods achieve 96% capacity retention after 100 cycles at 1C rate at room temperature, and 80% at 60 degrees C, whereas LiMn(2)O(4) shows worse retention of 91% at room temperature, and 69% at 60 degrees C. Moreover, temperature-dependent I-V measurements indicate that the sharp electronic resistance increase due to charge ordering transition at 290 K does not appear in our LiMn(2)O(4) nanorod samples, suggesting good battery performance at low temperature.

Electrochemical reduction of silver vanadium phosphorous oxide, Ag(2)VO(2)PO(4): the formation of electrically conductive metallic silver nanoparticles

As a cathode material, silver vanadium phosphorous oxide (Ag(2)VO(2)PO(4)) displays several notable electrochemical properties: large capacity, high current capability, and an effective delivery of high current pulses. These cell performance characteristics can be attributed to the presence of silver nanoparticles formed in-situ during the electrochemical reduction of Ag(2)VO(2)PO(4). Specifically, changes in the composition and structure of Ag(2)VO(2)PO(4) with reduction, especially the formation of silver nanoparticles, are detailed to rationalize a 15,000 fold increase in conductivity with initial discharge, which can be related to the power characteristics associated with Ag(2)VO(2)PO(4) cathodes in primary lithium batteries.

Novel Nanocomposite Materials for Advanced Li-Ion Rechargeable Batteries

Nanostructured materials lie at the heart of fundamental advances in efficient energy storage and/or conversion, in which surface processes and transport kinetics play determining roles. Nanocomposite materials will have a further enhancement in properties compared to their constituent phases. This Review describes some recent developments of nanocomposite materials for high-performance Li-ion rechargeable batteries, including carbon-oxide nanocomposites, polymer-oxide nanocomposites, metal-oxide nanocomposites, and silicon-based nanocomposites, etc. The major goal of this Review is to highlight some new progress in using these nanocomposite materials as electrodes to develop Li-ion rechargeable batteries with high energy density, high rate capability, and excellent cycling stability.

LiFePO4 Nanoparticles Embedded in a Nanoporous Carbon Matrix: Superior Cathode Material for Electrochemical Energy-Storage Devices

An optimized nanostructure design for high-power, high-energy lithium-ion batteries and supercapacitors is realized by fabricating a nanocomposite with highly dispersed nanoparticles of active materials in a nanoporous carbon matrix. A nano-LiFePO₄ /nanoporous carbon matrix nanocomposite forms a bridge between a supercapacitor and a battery electrode and offers a reasonable compromise between rate and capacity.

Combination of lightweight elements and nanostructured materials for batteries

In a society that increasingly relies on mobile electronics, demand is rapidly growing for both primary and rechargeable batteries that power devices from cell phones to vehicles. Existing batteries utilize lightweight active materials that use electrochemical reactions of ions such as H(+), OH(-) and Li(+)/Mg(2+) to facilitate energy storage and conversion. Ideal batteries should be inexpensive, have high energy density, and be made from environmentally friendly materials; batteries based on bulk active materials do not meet these requirements. Because of slow electrode process kinetics and low-rate ionic diffusion/migration, most conventional batteries demonstrate huge gaps between their theoretical and practical performance. Therefore, efforts are underway to improve existing battery technologies and develop new electrode reactions for the next generation of electrochemical devices. Advances in electrochemistry, surface science, and materials chemistry are leading to the use of nanomaterials for efficient energy storage and conversion. Nanostructures offer advantages over comparable bulk materials in improving battery performance. This Account summarizes our progress in battery development using a combination of lightweight elements and nanostructured materials. We highlight the benefits of nanostructured active materials for primary zinc-manganese dioxide (Zn-Mn), lithium-manganese dioxide (Li-Mn), and metal (Mg, Al, Zn)-air batteries, as well as rechargeable lithium ion (Li-ion) and nickel-metal hydride (Ni-MH) batteries. Through selected examples, we illustrate the effect of structure, shape, and size on the electrochemical properties of electrode materials. Because of their numerous active sites and facile electronic/ionic transfer and diffusion, nanostructures can improve battery efficiency. In particular, we demonstrate the properties of nanostructured active materials including Mg, Al, Si, Zn, MnO(2), CuV(2)O(6), LiNi(0.8)Co(0.2)O(2), LiFePO(4), Fe(2)O(3), Co(3)O(4), TiS(2), and Ni(OH)(2) in battery applications. Electrochemical investigations reveal that we generally attain larger capacities and improved kinetics for electrode materials as their average particle size decreases. Novel nanostructures such as nanowires, nanotubes, nanourchins, and porous nanospheres show lower activation energy, enhanced reactivity, improved high-rate charge/discharge capability, and more controlled structural flexibility than their bulk counterparts. In particular, anode materials such as Si nanospheres and Fe(2)O(3) nanotubes can deliver reversible capacity exceeding 500 mA.h/g. (Graphite used commercially has a theoretical capacity of 372 mA x h/g.) Nanocomposite cathode materials such as NiP-doped LiFePO(4) and metal hydroxide-coated Ni(OH)(2) nanotubes allow us to integrate functional components, which enhance electrical conductivity and suppress volume expansion. Therefore, shifting from bulk to nanostructured electrode materials could offer a revolutionary opportunity to develop advanced green batteries with large capacity, high energy and power density, and long cycle life.

Fabricating genetically engineered high-power lithium-ion batteries using multiple virus genes

Development of materials that deliver more energy at high rates is important for high-power applications, including portable electronic devices and hybrid electric vehicles. For lithium-ion (Li+) batteries, reducing material dimensions can boost Li+ ion and electron transfer in nanostructured electrodes. By manipulating two genes, we equipped viruses with peptide groups having affinity for single-walled carbon nanotubes (SWNTs) on one end and peptides capable of nucleating amorphous iron phosphate(a-FePO4) fused to the viral major coat protein. The virus clone with the greatest affinity toward SWNTs enabled power performance of a-FePO4 comparable to that of crystalline lithium iron phosphate (c-LiFePO4) and showed excellent capacity retention upon cycling at 1C. This environmentally benign low-temperature biological scaffold could facilitate fabrication of electrodes from materials previously excluded because of extremely low electronic conductivity.