Toward Efficiently Rechargeable Li-O2 Batteries Utilizing Lithium Nitrate Based Electrolytes Wesley Walker, Vincent Giordani, Vyacheslav Bryantsev, Jasim Uddin, Dan Addison, Gregory V. Chase 10/29/2013 Liox Power, Inc., 129 N. Hill Ave., Suite 103, Pasadena, CA 91106 224th ECS Meeting in San Francisco, October 27 – November 1, 2013

Rechargeable non-aqueous Li-O2 cells: Where are we now? OCV discharge OCV charge OCV 2Li + O2  Li2O2 Ecell = 2.96 V Specific energy: 3458 Wh/kg O2 Most Li-ion battery materials are unstable in the O2 electrode including: Solvents [1]: carbonates, ethers, esters, lactones, sulfones Salts [2]: LiPF6, LiClO4 Binders [3]: PVDF Current collectors [4]: nickel Carbon [5] CO2 O2 electrode (Super P Carbon:PTFE 9:1wt.%) cycling at 50 mA/gcarbon (~0.25 mA/cm2) in 0.5 M LiTFSI/TEGDME Massive overpotential during charge Side reactions eventually dominate the cell reaction Power density is too low for practical purposes Capacity fades rapidly 1 Freunberger SA et al. (2011) J. Am. Chem. Soc. Freunberger SA et al. (2011) Angew. Chem. Int. Ed. Bryantsev VS et al. (2011) J. Phys. Chem. A 2 Veith GM et al. (2012) J. Phys. Chem. Lett. 3 Black R et al. (2012) J. Am. Chem. Soc. 4 Veith GM et al. (2011) J. Electrochem. Soc. 5 McCloskey BD et al. (2012) J. Phys. Chem. Lett.

Analytical Techniques at LIOX Airtight electrochemical cell with pressure sensor operated at a constant temperature of 30 °C 3-electrode Cell Automated, multi-cell electrochemical mass spectrometry Pressure sensor Valve ~10-12 mL gas volume cell Reference Electrode

DMA/LiNO3 and the Reactions of the Cathode Outline of the talk DMA/LiNO3 and the Reactions of the Cathode Cycling and Gas Analysis Effect of Concentration of LiNO3 on the Reactions of the Cathode DMA/LiNO3 and the Reactions of the Anode LiNO3 vs. LiTFSI Oxygen vs Argon Environment Effect of Concentration of LiNO3 on the Reactions of the Anode

1 M LiNO3 in DMA Li/1 M LiNO3 DMA (150 μL)/Csp, RT, 0.1 mA/cm2 3-electrode cell galvanostatic cycling utilizing a Csp cathode, a Li disk anode, a lithium reference electrode, and 1 M LiNO3/DMA electrolyte. 0.1 mA/cm2 = 20 mA/gcarbon (200 mAh/gcarbon) 1 M LiNO3 in DMA proves to be an effective electrolyte system in cells when utilizing a low current density and shallow cycling of the Li and carbon electrodes. Oxidation processes above 3.7 V result from the oxidation of LiNO2 which forms from the reduction of LiNO3 on lithium. Prolonged cycling of the system results in an increase in charge/discharge polarization and a sharper end to the charging process. Walker, W.; Giordani, V.; Uddin, J.; Bryantsev, V. S.; Chase, G. V; Addison, D. A. Rechargeable Li-O2 Battery Using a Lithium Nitrate/N,N-Dimethylacetamide Electrolyte. J. Am. Chem. Soc. 2013, 135, 2076−2079.

In-Situ Gas Analysis of 1M LiNO3 DMA Gas Profiles of the 1st, 40th, and 80th cycles of a Li/1 M LiNO3 DMA (150 μL)/Csp, RT, cycled at 0.1mA/cm2. 1st Cycle 40th Cycle 80th Cycle During each cycle the cell was discharged 10 hours under O2, followed by a 4 hour OCV to swap gases from O2 to Ar, followed by a charge to 4.2 V under Ar, and finally a 2 hour OCV to switch from Ar to O2 environment. Oxygen is the dominate gas upon charging, with a small production of hydrogen throughout, and carbon dioxide at the end of charge. The 80th cycle shows no carbon dioxide production, which may result from the fact that this is an open cell and evaporation of the solvent (ie. increasing LiNO3 concentration) may have a stabilizing effect.

Effect of Concentration of LiNO3 on Cathode Li/LiNO3 DMA/Csp (first cycle) under ~1 atm of O2, RT, 0.1 mA/cm2. 1 M Coulombic efficiency as a function of cycle number. 3 M 5 M Increasing the concentration of LiNO3 results in: Less production of carbon dioxide gas. A sharper end of charge. Less oxidation processes. Higher Coulombic efficiency.

Effect of Concentration of LiNO3 on Cathode In situ pressure analysis (1st cycle) Li/LiNO3 DMA/Csp under ~1.3 atm of O2, 30° C, 0.1 mA/cm2. Discharge limited to 10 hours. 1 M 3 M 5 M Pressure efficiency, ex situ quantification of evolved gases during charge (1st cycle) and rate of O2 consumption for Li/O2 cells cycled in 1M, 3M and 5M LiNO3 DMA electrolytes. Electrolyte ΔPcharge/ΔPdischarge (%) Gas quantification (mol.%) O2 consumption (mol.s-1) 1st cycle 30th cycle H2 O2 CO2 1M LiNO3 DMA 79.8 % 74.5 % 5% 91% 4% 4.71x10-11 3M LiNO3 DMA 85.9 % 81.0 % 94% 2% 4.29x10-11 5M LiNO3 DMA 90.8 % 82.9 % 3% 96% 1% 3.61x10-11 A higher concentration of LiNO3 in DMA inhibits both the consumption of oxygen on cycling and the production of hydrogen and carbon dioxide.

Effect of Concentration of LiNO3 on Cathode Li 1s, O 1s, and C 1s spectra as a function of sputtering time for carbon electrodes harvested from Li/O2 cells cycled in 1M and 5M LiNO3 DMA electrolytes for 30 cycles In situ electrochemical mass spectrometry analysis (1st cycle) of Li/O2 cells cycling in LiNO3 DMA using 13C air cathode, RT, 0.1 mA/cm2. 1 M 5 M Csp electrodes from 5 M LiNO3/DMA cells show decreases in signals from Li (salt), O (Li2CO3), C (CO3) and an increase in C (C-C) at lower sputtering times then 1 M LiNO3/DMA. Cells constructed with 13C labeled carbon evolved more 13CO2 in 1 M cells then in the 5 M cells. Both results are consistent with higher concentrations of LiNO3 in DMA diminishing side reactions on the air electrode.

DMA/LiNO3 and the Reactions of the Cathode Outline of the talk DMA/LiNO3 and the Reactions of the Cathode Cycling and Gas Analysis Effect of Concentration of LiNO3 on the Reactions of the Cathode DMA/LiNO3 and the Reactions of the Anode LiNO3 vs. LiTFSI Oxygen vs Argon Environment Effect of Concentration of LiNO3 on the Reactions of the Anode

Anode: LiTFSI vs. LiNO3 in DMA Li/electrolyte (100µL)/Li stored under Ar at 30 C at OCV LiTFSI LiNO3 Pressure and voltage profiles of symmetric Li/Li cells cycled in 1 M LiTFSI (a) and 1 M LiNO3 (b) DMA under O2. Current density: 0.2 mA/cm2. Li plating/stripping limited to 10 h per half-cycle LiTFSI LiNO3 LSV and Li/Li cycling measurements show that the use of LiNO3 inhibits the reaction between DMA and lithium metal.

Possible Decomposition Mechanism of DMA on Li Dimethylamine is a gas and should be detectable via pressure and gas analysis. Solid products (if not soluble) should be detectable via SEM and EDX analysis. Giordani, V.; Walker, W.; Bryantsev, V. S.; Uddin, J.; Chase, G. V.; Addison, D. Synergistic Effect of Oxygen and LiNO3 on the Interfacial Stability of Lithium Metal in a Li/O2 Battery. J. Electrochem. Soc. 2013, 160, A1544−A1550.

DMA Decomposition via Ex-Situ Gas Analysis Main Mass Fragments of Dimethyl Amine Mass (amu) Response (%) 45 27% 44 33% In situ pressure analysis of symmetric Li/Li cells kept at OCV for 3 days Ex situ mass spectrometry analysis of symmetric Li/Li cells 1 2 3 4 Addition of LiNO3 inhibits the production of dimethylamine gas. Additionally, the presence of O2 has a positive effect on DMA decomposition.

DMA Decomposition via SEM and EDX SEM / EDX analysis of a lithium electrode cycled in a symmetric Li/Li cell containing 1 M LiNO3 DMA electrolyte for 10 cycles. Current density: 0.2 mA/cm2. Li stripping/plating limited to 5 h per half-cycle. Ar Cycling 1 M LiNO3 DMA under Ar results in a build up a solid material both visually and via SEM. Additionally, the elemental composition of this film as determined via EDX is consistent with the proposed DMA decomposition mechanism. Elemental composition of the cell cycled under O2 is consistent with Lithium oxide species forming the SEI. Oxygen Carbon Nitrogen O2 Oxygen Carbon

Effect of an Oxygen Environment vs. an Argon Environment Voltage profile a symmetric Li/Li cell cycled in 1 M LiNO3 DMA electrolyte under Ar, 0.2 mA/cm2, 5 h half cycles. Voltage profile (first and last 100 hours) of a symmetric Li/Li cell cycled in 1 M LiNO3 DMA electrolyte under O2. Argon Oxygen SEI formation reaction: 2Li + LiNO3  Li2O + LiNO2

Effect of Concentration of LiNO3 on Anode In situ pressure analysis of symmetric Li/Li cells kept at OCV under ~1 atm of Ar for 2 weeks. Nyquist plots obtained from the symmetric Li/Li cell containing 1M LiNO3 DMA electrolyte during the storage experiment. Nyquist plots obtained from the cell using the 5M LiNO3 DMA electrolyte. 1 M 5 M

Effect of Concentration of LiNO3 on Anode XRD of lithium from Li/LiNO3 DMA/Csp cycled 30 times at 0.1mA/cm2 under O2 10h discharge Corresponding ex-situ gas analysis. Li Li Li LiOH was not detected by XRD on Li anodes post cycling with higher molarity LiNO3/DMA electrolytes which suggests superior stability of the electrolyte and this is consistent with the ex situ gas quantification of cycled Li/O2 cells with Csp cathode that showed less H2 being produced as you go from 1 to 3 to 5M LiNO3 DMA.

Comparison of load curves for Li/LiNO3 DMA/Csp 0.1 mA/cm2. Conclusion Comparison of load curves for Li/LiNO3 DMA/Csp 0.1 mA/cm2. LiNO3 DMA is an effective electrolyte system for Li-O2 cells cycled at low current densities and low utilization of the Li and Carbon electrodes. Increasing the concentration of LiNO3 Increases the cycling efficiency and charge profiles. Decreases side reactions of the solvent with the anode and the discharge products with the cathode as determined via XRD, SEM, XPS, EIS, in situ and ex situ gas, and pressure measurements. However even at high concentrations of LiNO3 there remains a constant consumption of O2 gas upon cycling in both full cells and symmetric Li cells. 1 M 5 M Li/1M LiNO3 DMA/Csp Li/1M LiNO3 DMA/Li

Liox Power, Inc., 129 N. Hill Ave., Suite 103, Pasadena, CA 91106, USA Predicting the Electrochemical Behavior of Lithium Nitrite in Aprotic Solvents Vyacheslav S. Bryantsev, Jasim Uddin, Vincent Giordani, Wesley Walker, Gregory V. Chase, Dan Addison 10/30/2013 Liox Power, Inc., 129 N. Hill Ave., Suite 103, Pasadena, CA 91106, USA B4: Computational Science of Battery Materials Wednesday, October 30, 2013: 15:00 Sutter Room, Tower 3, 6th Floor (Hilton San Francisco Union Square)

The use of LiNO3 salt in Li-O2 rechargeable cells SEI formation reaction: 2Li + LiNO3  Li2O + LiNO2 Li/electrolyte (100µL)/Li (untreated) stored under Ar at 30 C at OCV untreated Li/P75 carbon paper LSV, OCV to 4.3 V, v= 0.05 mV/s, RT, 1 atm O2 EIS studies illustrate the role of LiNO3 in improving the interfacial properties of the cell. LSV measurements show that the use of LiNO3 inhibits the reaction between DMA and lithium metal which leads to the oxidation of soluble electrolyte decomposition products.

Combination of LiNO3 and O2 provide better SEI Voltage profile (first and last 100 hours) of a symmetric Li/Li cell cycled in 1 M LiNO3 DMA electrolyte under O2. Inset: under Ar. Current density: 0.2 mA/cm2. Nyquist plots obtained from symmetric Li/Li cells after cycling. Inset: Nyquist plots obtained from the cell cycled under O2. SEI formation reaction: 2Li + LiNO3  Li2O + LiNO2

Anode: LiTFSI vs. LiNO3 Li/electrolyte (100µL)/Li stored under Ar at 30 C at OCV Li/P75 carbon paper LSV, OCV to 4.3 V, v= 0.05 mV/s, RT, 1 atm O2 Pressure and voltage profiles of symmetric Li/Li cells cycled in 1 M LiTFSI (a) and 1 M LiNO3 (b) DMA under O2. Current density: 0.2 mA/cm2. Li plating/stripping limited to 10 h per half-cycle LSV and Li/Li cycling measurements show that the use of LiNO3 inhibits the reaction between DMA and lithium metal.