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Layer-Structured Transition Metal Oxides as Cathodes for K-Ion Batteries

Layer-Structured Transition Metal Oxides as Cathodes for K-Ion Batteries. Abstract #: ES04.23.057. Dec. 01 2017 04:45 PM. Haegyeom Kim , Jae Chul Kim, Dong-Hwa Seo , Shou -Hang Bo, Deok -Hwang Kwon, Tan Shi, and Gerbrand Ceder * Post-doc Fellow in Ceder group

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Layer-Structured Transition Metal Oxides as Cathodes for K-Ion Batteries

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  1. Layer-Structured Transition Metal Oxides as Cathodes for K-Ion Batteries Abstract #: ES04.23.057 Dec. 01 2017 04:45 PM Haegyeom Kim, Jae Chul Kim, Dong-Hwa Seo, Shou-Hang Bo, Deok-Hwang Kwon, Tan Shi, and GerbrandCeder* Post-doc Fellow in Ceder group Materials Sciences Division Lawrence Berkeley National Laboratory H. Kimet al. Adv. Energy Mater. 1700098 (2017) H. Kimet al. Adv. Mater. 1702480 (2017) Download these slides at http://ceder.berkeley.edu

  2. K-Ion Batteries: Alternative option for large scale ESS • Earth Abundant • Low standard potential • Graphite anode Komaba et al. Electrochem. Commun. 2015, 60, 172, http://periodictable.com/Properties/A/CrustAbundance.html Accessed May 2017.

  3. Academic activities in K-ion batteries Search at May 20th, 2017 • Recently, K-ion batteries attract much attention. H. Kim et al. Adv. Energy Mater. Accepted (2017)

  4. Layered transition metal oxides as promising candidates • Transition metal component • High redox activity • 2-dimensional K migration pathways • Good rate capability • Rigid oxide framework •  Good cycle stability Layered transition metal oxides (KxTMO2, TM= Transition Metal) can be promising cathode candidates for K-ion batteries. Xiang et al. J. Electrochem. Soc. 2015, 162, A1662

  5. The P2-type K0.6CoO2 is synthesized by solid-state method • P2-type K0.6CoO2 was synthesized by a conventional solid-state method. • The smaller K content (compared to Na and Li) likely results from the larger ionic size of K. H. Kim et al. Adv. Energy Mater. 1700098 (2017)

  6. K storage properties in K0.6CoO2 K metal anode 0.7 M KPF6 in EC/DEC electrolyte • Reversible K storage in K0.6CoO2 is observed in the electrochemical cells. H. Kim et al. Adv. Energy Mater. 1700098 (2017)

  7. In-situ XRD demonstrates reversible K de/intercalation Time (Hours) Voltage (V vs. K) Two theta (Deg. Mo) • Reversible K release/storage in K0.6CoO2 is observed in the electrochemical cells. H. Kim et al. Adv. Energy Mater. 1700098 (2017)

  8. In-situ XRD demonstrates reversible K de/intercalation • Upon charge, (008) peak moves to lower angle, indicating the increase of CoO2 slab distance. • (008) peak moves back to the original position, indicating reversible reactions. H. Kim et al. Adv. Energy Mater. 1700098 (2017)

  9. The slope of voltage curves increases as the size of alkali ions increases LiCoO2 1 V per 0.6 Li transfer (1.66 V/Li+) 1.8 V per 0.52 Na transfer (3.46 V/Na+) Voltage step of ~0.08 V at Li0.5CoO2 2.3 V per 0.35 K transfer (6.57 V/K+) T. Ohzuku et al. J. Electrochem. Soc. 1994, 141, 2972 R. Berthelot et al. Nat. Mater. 2011, 10, 74 Y. –I. Jang et al. J. Electrochem. Soc. 2002, 149, A1442

  10. Strong K+-K+ repulsion makes more sloped voltage curves Alkali ions LixCoO2 KxCoO2 NaxCoO2 Transition metals Oxygen Ionic size of alkali ions • Less screening of electrostatics between K ions by oxygen results in strong K+/vacancy ordering at given K concentrations, forming remarkable amount of phase transitions. Li+ (0.76 Å) Na+ (1.02 Å) K+(1.38 Å) Slab distance for alkali ions in LixCoO2 (2.64 Å) NaxCoO2 (3.43 Å) KxCoO2(4.25 Å) T. Ohzuku et al. J. Electrochem. Soc. 1994, 141, 2972 R. Berthelot et al. Nat. Mater. 2011, 10, 74

  11. The P3-type K0.5MnO2 is synthesized by solid-state method • P3-type K0.5MnO2 was synthesized by a conventional solid-state method. H. Kim et al. Adv. Mater. 170248 (2017)

  12. Difference between KxCoO2 and KxMnO2 :Multiple steps vs. smooth profiles P2-K0.6CoO2 P3-K0.5MnO2 • Strong K+/vacancy ordering is responsible for stair-like voltage curves. • (i) lower K diffusivity and (ii) defects of KxMnO2 may cause the disturb of K+/vacancy ordering. H. Kim et al. Adv. Energy Mater. 1700098 (2017) H. Kim et al. Adv. Mater. 170248 (2017)

  13. Similarity between KxCoO2 and KxMnO2 :Sloped voltage curves P2-K0.6CoO2 P3-K0.5MnO2 • The overall steep voltage slop is attributable to strong K+-K+ repulsion. • The sloped voltage of K-layered oxides limits their reversible capacities and working voltages. H. Kim et al. Adv. Energy Mater. 1700098 (2017) H. Kim et al. Adv. Mater. 170248 (2017)

  14. Summary • New P2-type K0.6CoO2 and P3-type K0.5MnO2 cathodes are proposed for KIBs. • P2-type K0.6CoO2 shows stair-like voltage curves, but P3-type K0.5MnO2 has smooth voltage profiles. • However, K-layered oxide frameworks result in low specific energy (low capacity and low voltage). • Our preliminary study demonstrates the polyanionic frameworks can be promising candidates for high-energy cathode for KIBs.

  15. Acknowledgement GerbrandCeder, Chancellor’s Professor Department of Materials Science and Engineering Dr. Jae Chul Kim Dr. Dong-Hwa Seo Prof. Shouhang Bo The Laboratory Directed Research and Development Program of Lawrence Berkeley National Laboratory under U. S. Department of Energy (DE-AC02-05CH11231) Mr. Tan Shi Dr. Deok-Hwang Kwon

  16. Thank you H. Kim et al. “K‐Ion Batteries Based on a P2‐Type K0.6CoO2 Cathode.” Adv. Energy Mater. 1700098 (2017) H. Kim et al. “Investigation of Potassium Storage in Layered P3‐Type K0.5MnO2 Cathode.” Adv. Mater. 1702480 (2017) Download these slides at http://ceder.berkeley.edu

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