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Progress toward the development of current collector-conductive polymer-silver ͑cc-cp-Ag͒ composite cathodes for nonaqueous metal air batteries is presented here, where the contribution of each component toward the overall oxygen reduction activity of the multifunctional cc-cp-Ag composite is studied. First, the effect of the chemical identity of the current collector ͑carbon versus gold͒ on the electrochemical reduction of oxygen is examined, accompanied by a conductive polymer deposition study. These two studies together demonstrate that a conductive polymer deposit can eliminate any competitive electrochemistry due to the current collector. Second, the role of the conductive polymer in improving physical strength of the composite electrode is evaluated using an electrode durability test. Third, a systematic study of the Ag loading effect is undertaken to determine the minimum silver loading required for significant enhancement in oxygen reduction activity.

Magnesium intercalated vanadium oxide xerogels, Mg 0.1 V 2 O 5 ·2.35H 2 O and Mg 0.2 V 2 O 5 ·2.46H 2 O were synthesized using an ion removal sol gel strategy. X-ray diffraction indicated lamellar ordering with turbostratic character. X-ray absorption spectroscopy indicated greater distortion of the vanadium-oxygen coordination environment in Mg In this report, Mg x V 2 O 5 ·nH 2 O were prepared by subtracting cations from a crystalline metal vanadate as an alternative strategy in order to adjust the cation amount, Figure 1a, different than the usual V 2 O 5 ·nH 2 O based sol-gel method.3 The as-prepared materials, x = 0.1 (MVO-1) and x = 0.2 (MVO-2), were characterized and electrochemical activity in lithium and magnesium electrolytes was determined. Post mortem analysis was done to determine the magnesium/vanadium ratio after cycling. Implications for use of Mg x V 2 O 5 ·nH 2 O in lithium and magnesium based batteries will be discussed, with particular focus on the structural role of Mg 2+ . ExperimentalSynthesis and characterization.-Mg x V 2 O 5 ·nH 2 O was synthesized via a sol gel process, 19 where aqueous magnesium vanadate (MgV 2 O 6 ) 20 was treated with an ion exchange resin. Characterization included X-ray diffraction (XRD), thermogravimetric analysis (TGA) and inductively-coupled plasma optical emission spectroscopy (ICP-OES).X-ray absorption spectroscopy (XAS) was acquired at the V Kedge (5.465 keV) in transmission mode at the National Synchrotron Light Source at Brookhaven National Laboratory. XAS scans of each sample and a V 2 O 5 reference were aligned to a vanadium foil measured simultaneously and merged in Athena, 21,22 and normalized utilizing AUTOBK. Theoretical FEFF6 23 models were created using orthorhombic V 2 O 5 crystal structure. 24 Distances are not corrected * Electrochemical Society Fellow. * * Electrochemical Society Member.z E-mail: esther.takeuchi@stonybrook.edu; kenneth.takeuchi.1@stonybrook.edu; amy.marschilok@stonybrook.edu for phase shifts, and are represented to be shorter than the actual interatomic distance.Electrochemical testing.-Working electrodes were prepared using Mg x V 2 O 5 ·nH 2 O, carbon and binder. The electrolytes were 1.0 M LiPF 6 in ethylene carbonate (EC)/dimethyl carbonate (DMC) (v/v 30/70) and 0.5 M magnesium bis(trifluoromethylsulfonylimide) (Mg(TFSI) 2 )/0.5 M dipropylene glycol dimethyl ether (dipro-glyme) in acetonitrile. Cyclic voltammetry (CV) was conducted for Li based system at 2.0 to 4.0 V with lithium auxiliary and reference electrodes with a scan rate of 0.1 mV/s. In Mg 2+ containing electrolyte Ag/AgNO 3 reference and carbon auxiliary were used with voltage limits of −1.0 and +0.85 V using a scan rate of 0.1 mV/s. Two electrode lithium cells were used for galvanostatic cycling between 2.0-3.8 V at rates of 0.1 C and 0.5 C, with 1C set as 200 mA/g. In magnesium based electrolyte a 0.1 C rate for both discharge and charge was used,

A novel three-component composite electrode consisting of a carbon current collector with conductive polymer and silver coating is described here. The composite electrode fabrication strategy is described and the composite electrode is evaluated as a cathode for oxygen reduction in non-aqueous media. This approach is utilized for the first time to prepare three-dimensionally structured carbon–conductive polymer–silver composites, yielding composite electrodes with ∼4× the oxygen reduction capacity of their planar counterparts. Improvement of cathode oxygen reduction activity will increase current capability and power output of metal air batteries, facilitating future development of small, lightweight, and long-life power sources.

The oxygen reduction reaction (ORR) at the carbon-conductive polymer-silver (C-cp-Ag) composite electrode in non-aqueous electrolyte with small amounts of added water is the subject of this study. The contributions of the various components of the composite electrode were assessed by employing four electrodes: (1) glassy carbon (C), (2) polypyrrole coated glassy carbon (C-cp), (3) silver disk (Ag), and (4) carbon-polypyrrole-silver composite (C-cp-Ag). Notably, with 5000 ppm of water in non-aqueous solution, the ORR reaction at Ag and C-cp-Ag shows an n = 4 reduction, while ORR at C and C-cp display an n = 1 reduction. The results show that the use of a multilayer C-cp-Ag composite electrode provides the opportunity to achieve the four electron reduction of one O 2 molecule, with a low precious metal (Ag) loading. In metal air batteries, the cathode consists of the electroactive cathode material, oxygen (O 2 ) and the remainder of the inert electrode consisting of the current collector and oxygen reduction reaction (ORR) catalyst. Metal air batteries fall into a special category as the electroactive cathode material, oxygen (O 2 ), is available in excess from outside the battery. While the cathode current collector, the ORR catalyst and the oxygen reduction products all add mass, 1,2 metal air batteries still provide the opportunity for high energy densities relative to sealed battery technologies. 3,4 Notably, the structures and chemistries of the inert electrode (air electrode) can be varied to address ORR kinetic issues. Typically, a composite air electrode consists of an electrical conductor mixed with an ORR catalyst, often strengthened with a binder 5,6 and a support such as a metal mesh. 7,8 A disadvantage of the conventional air electrode fabrication strategy is that catalyst particles positioned within the electrode interior often have limited access to oxygen.With an earlier article, we introduced a new composite electrode paradigm for metal air batteries, and reported the preparation, characterization, and electrochemical activity of a carbon current collector-conductive polymer-silver (cc-cp-Ag) composite electrode. Enhanced oxygen reduction activity for our composite electrode was observed relative to coated glassy carbon or silver disk electrodes, at a low silver loading of < 0.3 mg cm −2 . Specifically, the role of the current collector toward the electrochemical reduction of oxygen, the role of the conductive polymer in improving the structural integrity of the composite electrode, and a quantitative study of the silver loading effect on ORR activity were all investigated. A notable advantage of the electrodeposition based strategy we developed is the ability to easily generate silver coated three-dimensionally structured composites via use of three dimensional electrically conductive substrates. Three dimensional electrodes can increase the active surface area, enabling reduction of more oxygen per unit planar area. This approach was utilized to prepare three-dimensionally structured carboncondu...