US 2016.0006089A1 (19) United States (12) Patent Application Publication (10) Pub. No.: US 2016/0006089 A1 Wu et al. (43) Pub. Date: Jan. 7, 2016 (54) POTASSIUM-OXYGEN BATTERIES BASED Publication Classification ON POTASSIUMSUPEROXDE (51) Int. Cl. (71) Applicants: Yiying WU, Columbus, OH (US); EY 2. 3. Xiaodi REN, Columbus, OH (US) HOLM. I.2/02 (2006.01) HOLM 4/96 2006.O1 (72) Inventors: Yiying Wu, Columbus, OH (US); Xiaodi (52) U.S. Cl. ( ) Ren, Columbus, OH (US) CPC ................ H0IM 12/08 (2013.01); H01 M 4/96 (2013.01); H0IM 4/9041 (2013.01); H0IM (21) Appl. No.: 14/762,768 12/02 (2013.01); HOIM2220/30 (2013.01); HOIM 2300/0028 (2013.01) (22) PCT Fled: Jan. 23, 2014 (57) ABSTRACT Potassium-oxvgenygen (K( O.)2) batteries based on ppotassium (86). PCT No.: PCT/US14/12730 superoxide (KO) are provided. The K-O batteries can S371 (c)(1), exhibit high specific energy a low discharge?charge potential (2) Date: UL 22, 2015 gap (e.g., a discharge?charge potential gap of less than 50 mV. 9 at a current density of 0.16 mA/cm) without the use of any catalysts. The discharge product of the K-O batteries is O O K—O, which is both kinetically stable and thermodynami Related U.S. Application Data cally stable. As a consequence of the stability of the discharge (60) Provisional application No. 61/755,753, filed on Jan. product, the K-O batteries can exhibit improved opera 23, 2013. tional stability relative to other metal-air batteries. DISCHARGE K+e CHARGE K"+O+e DISCHARGE K K" ELECTROLYTE POROUS CARBON Patent Application Publication Jan. 7, 2016 Sheet 1 of 10 US 2016/0006089 A1 Patent Application Publication Jan. 7, 2016 Sheet 2 of 10 US 2016/0006089 A1 O D E O O CC Y Z <C O CO (u0/Wu)ALISN3OLN3&Juno Patent Application Publication Jan. 7, 2016 Sheet 3 of 10 US 2016/0006089 A1 Q D E C CN lii s Z CC O CMO (u0/Wu) ALISN3OLN3&Yno Patent Application Publication Jan. 7, 2016 Sheet 4 of 10 US 2016/0006089 A1 AHELIVEºo-) (W) WLOA Patent Application Publication Jan. 7, 2016 Sheet 5 of 10 US 2016/0006089 A1 (W) WITOW Patent Application Publication Jan. 7, 2016 Sheet 6 of 10 US 2016/0006089 A1 (n'e) ALISNLN Patent Application Publication Jan. 7, 2016 Sheet 7 of 10 US 2016/0006089 A1 s L L 2 CD a. Y C a. O 5 C/O S. C/O ?h OO ?h Y O L L a. ? O O S (n'e) ALISNLN Patent Application Publication Jan. 7, 2016 Sheet 8 of 10 US 2016/0006089 A1 g s ?h Z s co E Y is Lo Y O O d N cy cN N (W) SWIION Patent Application Publication Jan. 7, 2016 Sheet 9 of 10 US 2016/0006089 A1 LL CD Y cC C CD |CO d St. cy CN ce (W) SWITOW Patent Application Publication Jan. 7, 2016 Sheet 10 of 10 US 2016/0006089 A1 S CN E CD - E CO Sto E. c i? N FH is O O s s (W) SWLION US 2016/0006089 A1 Jan. 7, 2016 POTASSUM-OXYGEN BATTERIES BASED potassium salt can be, for example, KPF. The K-O batter ON POTASSIUMSUPEROXDE ies can further comprise a separator that mechanically sepa rates the first electrode and the second electrode (e.g., a glassy STATEMENT REGARDING FEDERALLY fiber separator). SPONSORED RESEARCH ORDEVELOPMENT 0008. The K-O batteries are based on the one-electron 0001. This invention was made with Government Support reduction of oxygen to Superoxide. During discharge of the under Grant No. DMR-0955471 awarded by the National potassium-oxygen battery, a discharge product can beformed Science Foundation. The Government has certain rights in the at the second electrode that is thermodynamically stable and invention. kinetically stable. During discharge of the K-O batteries, the one-electron reduction of oxygen at the second electrode TECHNICAL FIELD can form a Superoxide (O). Once formed, the Superoxide is captured by potassium ions, forming KO. During discharge 0002 This application relates generally to potassium-oxy of the K-O battery, reaction (1) occurs at the second elec gen (K-O.) batteries based on potassium Superoxide (KO). trode BACKGROUND 0003 Metal-air batteries (MABs) have attracted interest and during charge of the K-O battery, reaction (2) occurs at for a variety of energy storage applications, largely because the second electrode MABs exhibit much larger specific energies than current KO-->O+e +K" (2). Li-ion batteries. In particular, Li-O batteries have attracted attention from researchers due to their high specific energy. The net discharge reaction for the K-O battery is 0004. In spite of their potential, lithium-oxygen batteries K+O->KO (AG'=-239.4 kJ/mol, E=2.48 V), correspond have significant shortcomings that have hampered their wide ing to a theoretical energy density of 935 Wh/kg for the spread adoption. The discharge process in Li-O batteries battery (based on the mass of KO). involves the reduction of oxygen to Superoxide (O), the 0009. By exploiting the one-electron quasi-reversible formation of LiO, and subsequent disproportionation of the O/O redox couple, K-O batteries can be designed that LiO into LiO and O, the charge process in Li-O batter possess a high specific energy, a low discharge?charge poten ies is the direct oxidation of LiO into O. As a result of the tial gap (e.g., a discharge?charge potential gap of less than 50 asymmetric reaction mechanism, the charge reaction in mV at a current density of 0.16 mA/cm), high round-trip Li O batteries has a much higher overpotential (-1-1.5V) energy efficiency (e.g., that possess a round-trip energy effi than the discharge reaction (-0.3 V). As a consequence, ciency of >95%), and good recyclability (e.g., that are Li O batteries exhibit a relatively low round-trip energy rechargeable). efficiency of around 60%. In addition, the instability of the electrolyte and carbon electrode under the high charging DESCRIPTION OF DRAWINGS potential (>3.5 V) contributes to the low rechargeability of 0010 FIG. 1 is a schematic illustration of a K-O battery. Li-O batteries. In addition, the insulating nature of LiO. 0011 FIG. 2A is a plot of cyclic voltammograms for oxy hinders the charge transfer reactions and result in a limited gen reduction and oxidation on a glassy carbon electrode battery capacity. (three-electrode setup) in oxygen-Saturated acetonitrile con 0005 Improved battery designs are needed to provide taining 0.1 MTBAPF, 0.1 M LiCIO, and 0.1 M KPF. The MABs that overcome the shortcomings of existing Li-O. current density of the oxygen reduction and oxidation in the battery designs. presence of the LiClO electrolyte was enlarged three times for clarity. Good reversibility of the O/O redox couple can SUMMARY be observed in the presence of the tetrabutylammonium cat 0006 Potassium-oxygen (K-O.) batteries based on ion (TBA) due to its large size (and thus low charge density). potassium Superoxide (KO) are provided. Potassium-oxy 0012 FIG. 2B is a plot of cyclic voltammograms for oxy gen batteries can comprise a first electrode comprising potas gen reduction and oxidation on a porous carbon electrode sium, a second electrode, and an electrolyte disposed between (two-electrode battery setup) in oxygen-Saturated the first electrode and the second electrode. dimethoxyethane (DME) containing 0.5 M KPF6. Oxygen 0007. The first electrode can comprise potassium metal pressure during measurement was 1 atm. (e.g., potassium metal foil). The second electrode can com (0013 FIG. 3A is a plot of voltage over time for the first prise a porous carbon electrode. The porous carbon electrode discharge and the first charge cycle of a K-O battery includ can comprise a metal foam framework (e.g., a Nifoam frame ing 0.5 M KPF in DME as an electrolyte. Following mea work), carbon (e.g., a carbon black powder), and a binder surement of the first discharge curve, the K metal electrode (e.g., a polymeric binder Such as polytetrafluoroethylene was replaced with a fresh K metal electrode prior to measure (PTFE)). After discharge of the K-O battery, the second ment of the first charge curve. Both the first discharge curve electrode can further comprise KO. The electrolyte can be a and the first charge curve were measured at a current density liquid electrolyte comprising potassium cations and an apro of 0.16 mA/cm. The electrode geometric area was 0.64 cm. tic solvent. For example, the electrolyte can be a K" electro The horizontal dash line indicates the calculated thermody lyte solution comprising an ether solvent and a potassium salt. namic potential of the K-O battery. In some embodiments, the ether solvent can comprise a sol (0014 FIG. 3B is a plot of voltage over time for the first vent selected from the group consisting of dimethoxyethane discharge and the first charge cycle of a Li-O battery (DME), diglyme, tetraglyme, and butyl diglyme. In certain including 1 M LiCFSO intetraglyme as an electrolyte. Both embodiments, the ether solvent can comprise a mixture of the first discharge curve and the first charge curve were mea diglyme and butyl diglyme (e.g., in a Volume ratio of 2:5). The sured at a current density of 0.16 mA/cm. The electrode US 2016/0006089 A1 Jan. 7, 2016 geometric area was 0.64 cm.