Boone B. Owens

Doped Vanadium Oxides as Host Materials for Lithium Intercalation

An improved cathodic material has been obtained by doping vanadium oxide hydrogel with silver. Silver-doped vanadium pentoxides with a silver molar fraction ranging from 0.01 to 1 were synthesized. With the successful doping, the electronic conductivity of V{sub 2}O{sub 5} was increased by 2 to 3 orders of magnitude. The electrochemical performance of the silver doped materials is very high, up to 4 moles of lithium per mole of silver-doped V{sub 2}O{sub 5} were found to be reversibly intercalated. In addition, the lithium diffusion coefficient is found to be high in the silver-doped material and with a smaller dependence on the lithium intercalation level. These enhancements resulted in high rates of insertion and delivered capacities.

High Surface Area V 2 O 5 Aerogel Intercalation Electrodes

Supercritical drying of gels yields amorphous aerogels (ARG) that serve as reversible, high capacity hosts for lithium ion intercalation. We have found that ARG material consists of a highly interconnected solid network that has a surface area up to 450 m2/g and a specific pore volume of 2.3 cm3/g. The material hosts at least per mole of (ARG) as determined by both galvanostatic intermittent titration (GITT) and chemical lithiation (CL) techniques. The equilibrium voltage‐composition curve is identical for both GITT and CL techniques as well. (ARG) has a specific energy in excess of 1600 Wh/kg, the highest ever reported for any vanadium oxide host.

Lithium ion insertion in porous metal oxides

Abstract Sol–gel processing of transition metal oxide precursors has been used to produce porous materials of high surface area. The technique has permitted the synthesis of solid amorphous vanadium and manganese oxides that are capable of reversibly intercalating large amounts of lithium ions. Therefore, these materials may function as high capacity (500–600 mAh/g), high-energy positive electrodes in lithium batteries. Methods to improve the kinetics and the cycle performance of these positive electrodes are showing promise.

High rate electrodes of V2O5 aerogel

Abstract In the present paper we report on high rate electrodes made from a conventional battery cathode material, vanadium pentoxide. The electrodes were obtained through a sol–gel process by which the active materials were coated in the form of thin, highly porous, layers on appropriate conducting substrates. The composite electrodes are characterized by very short ionic and electronic paths throughout the intercalation compound. Aerogel films deposited on a Hastelloy felt substrate had specific surface areas of 40 m 2 /g with pores of 20–200 nm diameter and wall thicknesses of 10–20 nm. Electrochemical impedance analysis revealed the expected response for intercalation, except that there was no Warburg (diffusion) component. The latter demonstrates that we successfully eliminated one of the primary limitations of intercalation materials, i.e. diffusion in the solid phase, by the design of the composite electrodes.

Solid state electrolytes: overview of materials and applications during the last third of the Twentieth Century

Abstract Solid state ionics has been a very active field of science during the last third of the century. However, the first observations of conductivity in solid electrolytes occurred over 150 years ago. Faraday reported the transport of silver ions through silver sulfide in 1834. The present report describes some of the more recent investigations of solid state ionic materials and devices, with emphasis on room temperature materials and solid state batteries. Prof. Osamu Yamamoto and his colleagues discovered the most conductive room temperature solid ionic material that is known up to the present time. This compound is Rb 4 Cu 16 I 7 Cl 13 with a specific conductivity of 0.34 S/cm at 25°C.

Amorphous Manganese Dioxide: A High Capacity Lithium Intercalation Host

Amorphous manganese dioxide has been synthesized via a room‐temperature sol‐gel route. The material is a stable intercalation host for lithium and the intercalation capacity is greater than . The host remains amorphous in the entire intercalation range and the insertion process is reversible. When used as an intercalation electrode, the material stores energy at the level of . The latter represents an improvement over crystalline manganese oxide materials by factors of two to three. ©1998 The Electrochemical Society

Complexes of Lithium Imide Salts with Tetraglyme and Their Polyelectrolyte Composite Materials

Complexes of amorphous tetraglyme (G4) and lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) or lithium bis(perfluoroethyl-sulfonyl)imide (LiBETI) were prepared as pol(yethylene) oxide-type electrolytes. Addition of equimolar amounts of LiTFSI and tetraglyme results in a room temperature ionic liquid with the general formula [Li(G4)]TFSI. Differential scanning calorimetry analysis of [Li(G4)]TFSI reveals that it has a T g = -61°C, and the complex remains amorphous over a wide temperature range (-100 to 200°C), and has a very low vapor pressure for tetraglyme at room temperature. The corresponding BETI complex, [Li(G4)]BETI, crystallizes upon cooling and displays a T m = 31°C. Room temperature conductivities (25°C) of [LilG4)]TFSI and [Li(G4)]BETI were 1.13 and 0.63 mS/cm, respectively. Composite polymer electrolytes were prepared by addition of the complexes to polycations possessing TFSI or BETI anions. The composites afforded thin flexible membranes at polymer concentrations ≥50 mol % polymer with room temperature conductivities greater than 10 -4 S/cm. In general, increased concentrations of BETI anions in these materials resulted in increased mechanical stability but decreased ionic mobility. The complexes and composite polymer electrolytes displayed excellent anodic stability up to +4.5 V (vs. Li + /Li) and exhibited breakdown voltages ≥+5.5 V (vs. Li + /Li) on stainless steel electrodes.

Thermal Stability of the Polymer Electrolyte ( PEO ) 8LiCF3 SO 3

We studied the poly(ethylene oxide)-LiCF 3 SO 3 system in order to determine the stability of the polymer electrolyte when applied to various electrode pairs. We investigated the thermal stability of the polymer electrolyte (PEO) 8 LiCF 3 SO 3 in contact with lithium metal and the cathode materials, amorphous V 2 O 5 , LiV 3 O 8 , V 6 O 13 , and LiCoO 2 . The properties of the electrolyte were measured by complex impedance analysis and TG-DTA. It was demonstrated that the electrolyte was stable with lithium metal up to 220 o C, and also was stable with the above mentioned cathode materials at temperatures below about 160 o C. The decomposition rate of the polymer electrolyte was faster in air than in Ar gas

Performance of Lithium/ V 2 O 5 Xerogel Coin Cells

Vanadium pentoxide xerogel (XRG) materials have shown promise for use as cathodes in high energy density batteries. A composite cathode was formed from a mixture of the XRG, carbon, and two binders and studied in a coin cell configuration. The cathode, separator, and lithium anode were stacked in a 2,016 coil cell container, and a liquid electrolyte was used for the investigation. In contrast to thin film configurations where 4 Li{sup +} ions may be inserted per mole of the XRG host, the composite cathode supported the insertion of less than 2 Li{sup +} ions per mole of V{sub 2}O{sub 5} (XRG). It appears that morphology, electronic conductivity, and solid-state diffusivity combined to limit the performance of the cathodes.

Performance of polymer electrolyte cells at +25 to +100°C

Solid-state rechargeable polymer-electrolyte batteries utilizing lithium anodes and V/sub 6/0/sub 13/ composite cathodes were investigated at 100 C. The polymer electrolyte was a complex formed between polyethylene oxide (PEO) and LiCF/sub 3/SO/sub 3/. Over a hundred cycles were obtained at the C/5 rate (45% depth of discharge) with greater than 75% of the initial capacity of V/sub 6/0/sub 13/ being maintained at cycle number one-hundred. Cells made with propylene carbonate (PC)-doped polymer electrolyte also showed good performance at room temperature.