Development of Electrode Architectures for High Energy Density Electrochemical Capacitors Majid Beidaghi 1 , Maria Lukatskaya 1 , Emilie Perre 2 , Ryan P. Maloney 2 , Yury Gogotsi 1 , Bruce Dunn 2 1 Department of Materials Science and Engineering and A.J. Drexel Nanotechnology InsItute, Drexel University, USA 2 Department of Materials Science and Engineering, University of California – Los Angeles, Los Angeles, CA, USA Introduc;on Experimental Results Conclusions Acknowledgements References 1 10 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.00 0.05 0.10 0.15 0.20 0.0 0.1 0.2 0.3 0.4 0.5 "Blocked Pore Distribution" = Before - After After hydrothermal synthesis dV/d (cc/nm/g) Pore diameter (nm) Before hydrothermal synthesis Without bonding agent – 100’s nm With bonding agent -10’s nm Smaller par;cles fill micro and mesoporosity of CarbideDerived Carbon (CDC) Phenylphosphonic Acid bonding agent dras;cally reduces metaloxide par;cle size The Nb 2 O 5 CDC composite electrodes demonstrate higher capaci;es at different scan rates compared to CDC alone. At a scan rate of 50 mV/s, with 1M LiClO 4 in acetonitrile electrolyte, the Nb 2 O 5 CDC composites (with various C:Nb raIos) display increased capaciIes compared with the CDC alone. Other aqueous and non aqueous electrolytes proved undesirable, either due to instability of the solvent at the required potenIals or lower ionic conducIviIes. Carbide Derived Carbon (CDC) has a high surface area due to small pores. The pore size is tailorable, from a few nanometers up to tens of nanometers wide, by controlling pyrolisis temperature. The size of the oxide parIcles must be tailored to match the pore size of the CDC. Too large parIcles will occlude the pores, prevenIng uIlizaIon of the CDC’s high surface area. Oxide parIcles tuned to fit within the small pores make effecIve use of the high surface area of the CDC (MeOx) ChlorinaIon temperature allows tailoring of carbon mesoporosity while maintaining macrostructure SiCNCDC TiCNanofelt CDC Nb 2 O 5 CDC Composite CDC nanofelts tested as fiberelectrodes outperform the power handling ability of carbon onions at intermediate scan rates (up to 2 V/s) Increasing the pyrolysis temperature increased the amount of mesopores in the resulIng CDC. CDC CDC CDC • CDC with hierarchical pore structure (micropores & mesopores with mean pore size, 3–10 nm) and large BET surface area, up to 2400 m 2 g 1 , were synthesized by etching amorphous or crystalline polymerderived SiCN ceramics. • Micropores form by etching Si atoms from the SiC phase, while mesopores derive from the eliminaIon of Si–N moieIes. The resulIng morphology (pore size, PSD, and SSA) strongly depends on pyrolysis temperature of the preceramic polymer, as well as on etching condiIons. • Mechanically flexible TiCCDC nanofelts were developed through chlorinaIon of electrospun TiC nanofibrous felts. The TiCCDC nanofelts retained the morphological properIes of the precursor, while had substanIally higher values of SSA and pore volume. • Nanoscale Nb 2 O 5 can be easily synthesized within the pores of CDC support. • Capacitance measurements for the Nb 2 O 5 CDC material shows a high level of energy storage, significantly higher than CDC. 1. S.H. Yeon, P. Reddington, Y. Gogotsi, J. E. Fischer, C. Vakifahmetoglu and P. Colombo, Carbon, 2010, 48, 201210 2. V. Presser, L. Zhang, J. J. Niu, J. McDonough, C. Perez, H. Fong and Y. Gogotsi, Advanced Energy Materials, 2011, 1, 423430 3. Y. Gao, V. Presser, L. Zhang, J. J. Niu, J. K. McDonough, C. R. Pérez, H. Lin, H. Fong and Y. Gogotsi, Journal of Power Sources, 2012, 201, 368375 4. V. Presser, M. Heon and Y. Gogotsi, Advanced Func<onal Materials, 2011, 21, 810833 5. X. Wang, G. Li, Z. Chen, V. Augustyn, X. Ma, G. Wang, B. Dunn and Y. Lu, Advanced Energy Materials, 2011, 1, 10891093 6. J. W. Kim, V. Augustyn and B. Dunn, Advanced Energy Materials, 2012, 2, 141148 7. Y. Zhao, J. Li, C. Wu and L. Guan, Nanoscale Res Len, 2011, 6, 71 The principal goal of the present research is to create an electrode architecture for electrochemical capacitors (ECs) that possesses both the high specific power of carbon supercapacitors and the high specific energy of pseudocapacitive materials. The design and fabrication of these electrodes are based on the nanoscale deposition of transition metal oxides onto mesoporous carbon-based supports. Extraction of metals from carbides can generate a broad range of carbon nanostructures, which are known as Carbide-Derived Carbons (CDCs). The structures of CDCs as well as their pore size distribution depend on the crystal structure of the carbide precursor as well as process parameters including temperature, time and environment. Nanoscale transition metal oxides such as niobium oxide (Nb 2 O 5 ) can be easily synthesized on the CDC surface via an aqueous hydrothermal route. The oxide size can be tailored to match the CDC porosity, allowing for optimization of ionic and electronic transport within the electrode. A key feature with these architectures is that each component possesses interconnected mesoporosity to facilitate electrolyte access to both phases. -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 -60 -40 -20 0 20 40 Current (A/g) Potential (V vs. Ag) CDC C/Nb=0.5 C/Nb=1 C/Nb=2 Nb 2 O 5 2 4 6 8 10 12 14 16 18 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 SiCN-CDC (pyrolyzed at 800 °C) SiCN-CDC (pyrolyzed at 1200 °C) dv(d) (cc/nm/g) Pore Width (nm) SiCN-CDC (pyrolyzed at 1400 °C) 0.01 0.1 1 10 0.0 0.2 0.4 0.6 0.8 1.0 C/C 0 Scan rate (V/s) CDC nano-felt (600 °C, film) CDC nano-felt (600 °C, powder) Carbon Onions (1800 °C, powder) Graphene (Stoller et al., Nano Letters, 2008) 0 100 200 300 400 500 0 200 400 600 800 1000 1200 Capacity (C/g) Scan rate (mV/s) CDC Nb 2 O 5 -CDC Nb 2 O 5 Nb 2 O 5 -CNT TEM 5 nm SEM SEM TEM TEM TiC Disordered carbon Disordered carbon Graphitic shell TiCCDC 2 µm 2 µm 5 nm 5 nm Cl 2 Cl 2 100 nm The authors gratefully acknowledge the support of the Department of Energy / Office of Electricity’s Energy Storage Program Future Work • Scale up producIon of Nb 2 O 5 CDC composite powder • Incorporate powder into coin cell devices • OpImize coin cell electrode loading and morphology for enhanced specific energy and power 100 nm Carbide Powder Carbide Derived Carbon (CDC) Cl 2 2001200°C Nb 2 O 5 -CDC Composite H 2 200600°C Remove metals via chlorinaIon Anneal structure in flowing hydrogen Begin with a carbide precursor, such as SiCN, Ti 3 SiC 2 , or TiAlC 2 ResulIng Carbide Derived Carbon with tailored morphology Deposit metaloxide onto CDC Hydro thermal Synthesis 200°C 96 hours • Ammonium niobate oxalate hydrate • Phenylphsophonic acid • Urea ResulIng Carbide Derived Carbon with metaloxide nanoparIcles for increased specific energy Electrode 1 Electrode 2 Separator + Electrolyte Microcavity Electrodes Swagelok cells Coincells 100 nm 100 nm