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Dual-intercalation batteries implement graphite electrodes as both cathodes and anodes and offer high specific energy, inexpensive and environmentally sustainable materials, and high operating voltages. Our research investigated the influence of surface composition on capacities and cycling efficiencies of chemically functionalized all-graphite battery electrodes. We subjected core-shell spherical particles and synthetic graphite flakes to high-temperature air oxidation, and hydrogenation to introduce, respectively, -OH, and -H surface functional groups. We identified noticeable influences of electrode surface chemistry on first-cycle efficiencies and charge storage densities of anion and cation intercalation into graphite electrodes. We matched oxidized cathodes and hydrogenated anodes in dual-ion batteries and improved their overall performance. Our approach provides novel fundamental insight into the anion intercalation process and suggests inexpensive and environmentally sustainable methods to improve performance of these grid-scale energy storage systems., Funding Agencies|U.S. Army Research LaboratoryUnited States Department of DefenseUS Army Research Laboratory (ARL); College Qualified Leaders (CQL) Army Educational Outreach Program

In this work we study heat-treated FeCu-phthalocyanine (FeCuPc) complexes as the catalyst for oxygen reduction in non-aqueous electrolyte Li/air cells by supporting the catalyst on a high surface area Ketjenblack EC-600JD carbon black. It is shown that the resultant FeCu/C catalyst not only accelerates the two-electron reduction of oxygen as "O2 + 2Li+ +2e Li2O2" but also catalyzes the chemical disproportionation of Li2O2 as "2Li2O2 2Li2O+O2" In Li/air cells, the catalyst reduces polarization on discharge while simultaneously reducing the fraction of Li2O2 in the final discharged products. In a 0.2 mol LiSO3CF3 7:3 (wt.) propylene carbonate (PC)/tris(2,2,2-trifluoroethyl) phosphate (TFP) electrolyte, the Li/air cells with FeCu/C show at least 0.2V higher discharge voltage at 0.2 8722 than those with pristine carbon., Published in Electrochimica Acta v56 p4544-4548, 2011. The original document contains color images.

In this work, we study methyl nonafluorobutyl ether (MFE) and tris(2,2,2-trifluoroethyl) phosphite (TTFP), respectively, as a co-solvent for the non-aqueous electrolyte of Li/air battery. Results show that in certain solvent ratios, both solvents are able to increase the specific capacity of carbon in Li/O2 and Li/air cells. More interestingly, the improvement in discharge performance of the Li/air cells increases with discharge current density. These results cannot be explained by the ionic conductivity and viscosity data of the electrolytes since the participation of fluorinated co-solvents hardly changes viscosity of the solvent blends while reversely reduces ionic conductivity of the electrolyte. In particular, we find that a 30 wt.% (vs. solvent) addition of TTFP into a 0.2m (molality) LiSO3CF3 PC electrolyte can significantly improve the discharge performance of Li/air cells, and that the resultant electrolyte is able to support long-term operation of Li/air cells in dry ambient environments due to its low volatility. We believe that the observed performance improvement is associated with the increased dissolution kinetics and solubility of oxygen in fluorinated solvent containing electrolyte., Journal of Power Sources, v196 n5 p2867-2870, 1 Mar 2011; published online 11 Nov 2010. The original document contains color images.

The effect of quaternary ammonium on discharge characteristic of Li/O2 cells was studied by using Super-P carbon as air cathode, a 0.2 mol kg(-1) LiSO3CF3 1:3 (wt.) PC/DME solution as baseline electrolyte, and tetrabutylammonium triflate (NBu4SO3CF3) as an electrolyte additive or a co-salt. Results show that Li/O2 cells can run normally in an electrolyte with NBu4SO3CF3 as the sole conductive salt. However, such cells suffer lower voltage and capacity as compared with those using the lithium ionic baseline electrolyte. This is due to the larger molar volume of quaternary ammonium cation, which results in less deposition of oxygen reduction products on the surface of carbon. When used as an electrolyte additive or a co-salt, the ammonium is shown to increase capacity of Li/O2 cells. The plot of differential capacity versus cell voltage shows that the Li/O2 cell with ammonium added has broad and scatted differential capacity peaks between the voltages of two reactions of "2Li +O->Li2O2" and "2Li + Li2O2->2Li2O". This phenomenon can be attributed to the phase transfer catalysis (PTC) property of quaternary ammonium on the second reaction. Due to inverse effects of the cation geometric volume and the PTC property of ammonium ions on the discharge capacity, there is an optimum range for the concentration of ammonium. It is shown that the addition of NBu4SO3CF3 increases discharge capacity of Li/O2 cell only when its concentration is in a range from 5 mol% to 50 mol% vs. the total of Li/ammonium mixed salt, and that the optimum concentration is about 5 mol%. In this work we show that the addition of 5 mol% NBu4SO3CF3 into the baseline electrolyte can increase discharge capacity of a Li/O2 cell from 732mAhg(-1) to 1068mAhg(-1) (in reference to the weight of Super-P carbon) when the cell is discharged at 0.2mAcm(-2)., Published in Electrochimica Acta, v56 n3 p1283-1287, 1 Jan 2011; available online 23 Oct 2010. The original document contains color images.

The Li-CFx chemistry has been traditionally used for low rate applications at discharge rates of C/1000 or lower. The Army is supporting efforts to engineer Li/CFx batteries for Soldier applications that operate at higher rates, closer to C/10. This effort is based on the favorable specific energy and storage characteristics offered by this chemistry. Heat generation under high rate discharge is one potential concern in these batteries and, therefore, further study of the mechanism of heat generation and the differences in heat generation between various CFx materials is warranted. We demonstrate that the thermal power generated when a Li-CFx cell is discharged appears nearly instantaneously in the cell and ceases nearly as quickly when discharge is interrupted. Extrapolation of the running potential to zero heat results in a predicted voltage for the Li/CFx cell of 4.25 V, very near the theoretical potential calculated by Wood, et al. (1). The microcalorimetry results support the two phase model for discharge where a large overpotential, presumably due to the highly disfavored process of breaking covalent C-F bonds, dominates the OCV and running potential of the cell.

The performance of six different commercially available carbon monofluoride (CFx) materials were evaluated at four different discharge rates. The physical and chemical properties of the CFx materials were correlated to cell performance in lithium coin cells. This study was undertaken to determine if there are specific physical or chemical properties that can be tied to performance and if modification of these properties could lead to an improved carbon monofluoride material., The original document contains color images.

Tantalum (Ta) doping in lithium titanium oxide, Li4Ti5O12 (Li4Ti4.95Ta0.05O12), as function of different heat-treatment atmospheres (oxidizing/reducing) was investigated and compared to Li4Ti5O12 to determine its effect on electrical conductivity and rate capability. The ionic conductivity value of the white colored Li4Ti4.95Ta0.05O12 heated under an oxidizing atmosphere was ~3 x 10-8 S/cm with a DC electronic conductivity value of ~1 x 10-9 S/cm. These values are similar to values observed for Li4Ti5O12 heated under the same oxidizing atmosphere. These results suggest that both materials are predominately ionic conductors, with the extra charge of Ta compensated by a lattice defect, most likely titanium (Ti) vacancies. For the case of Li4Ti4.95Ta0.05O12 heated under a reducing atmosphere, it was purple colored with an electronic conductivity value of ~1 x 10-3 S/cm. Li4Ti5O12 heated under a reducing atmosphere was also purple colored with an electronic conductivity value of ~3 x 10-5 S/cm. These results suggest both of these materials are predominately electronic conductors where the electronic conductivity is a result of the reduction of some Ti+4 ions into Ti+3 ions. For Li4Ti4.95Ta0.05O12 this reduction is a result of the extra charge of the Ta whereas for Li4Ti5O12 it is a result of nonstoichiometry.

Cells from the new Nexelion battery from Sony Corporation were tested for capacity, low temperature performance, high power capability, high temperature storage, rapid recharge and cycle life on deep discharge. The Nexelion 14430 size cells were found to perform equal or better to conventional size 14430 cells in all areas tested but cycle life. The cycle life tests showed that the Nexelion cells loose capacity slightly faster than the conventional cell with deep cycling. However, because of the additional capacity provided by the Nexelion battery chemistry, the Nexelion cell still had more capacity than the conventional 14430 cell after 220 cycles., The original document contains color images.

For this project we constructed an inexpensive air cathode free of catalyst, capable of functioning in both acidic and neutral electrolytes, for use in a lithium/air-water battery. The use of acidic electrolyte is necessitated by the formation of the discharge product LiOH from the lithium/air-water reaction. We present a procedure for the construction of a carbon/PTFE air cathode for use with both acidic and neutral electrolytes. We evaluated the performance of the cathode in electrolytes ranging from pH=0 to pH=8 by applying voltage to a half cell, in reference to a Ag/AgCl reference electrode, and then measuring the steady state current. Current densities were found to be the highest in 1M H(sub2)SO(sub4), the most acidic electrolyte tested, and decreased as the pH of the electrolyte increased. The cathode performed well enough over the entire pH range to be useful for the lithium/air-water battery., 7NEYY2.

The purpose of this project was to construct an inexpensive air cathode free of catalyst that is capable of functioning in both acidic and basic electrolytes. The performance of an uncatalyzed air cathode for use in a Li-Air battery was evaluated over the pH range from 0 to 14. This study was undertaken to determine if air cathodes constructed solely from carbon black and polytetrafluoroethylene (PTFE) can function at a sufficient rate in sulfate based electrolytes to be useful in Li-Air batteries. Layered cathodes were constructed with a hydrophobic wet-proofing layer and an active hydrophilic layer that utilizes a high surface area carbon black. Electrolytes were formulated using H2SO4, Na2SO4, and NaOH in various combinations giving pH values ranging from 0 to 14. Electrolytes were also formulated using H2SO4, Li2SO4, and LiOH in combination, and HCl, LiCl, and LiOH in combination giving electrolytes with pH values ranging from 0 to 14. The cathodes were discharged in a three electrode cell from 0.0 V to -0.6 V vs. a Ag/AgCl reference electrode. The cathode performed well and met the requirement that a current density of at least 1-2 mA/cm2 was maintained at -0.3 V vs. Ag/AgCl.