Strategies to optimize lithium-ion supercapacitors achieving high- performance: Cathode configurations, lithium loadings on anode, and types of separator Wanjun Cao a, b , Yangxing Li d, * , Brian Fitch d , Jonathan Shih a, b , Tien Doung e , Jim Zheng a, b, c a Department of Electrical and Computer Engineering, Florida A&M University and Florida State University, Florida State University, Tallahassee, FL 32310, USA b Aero-Propulsion, Mechatronics and Energy (AME) Center, Florida State University, Tallahassee, FL 32310, USA c Center for Advanced Power Systems (CAPS), Florida State University, Tallahassee, FL 32310, USA d FMC Lithium Division, Highway 161, Bessemer City, NC 28016, USA e Office of Vehicle Technologies, U.S. Department of Energy, Annandale, VA 22003, USA highlights  PTFE binder for activated carbon cathode offers improved capacitor performances.  The optimized mass ratio of SLMP to hard carbon electrode is about 1:7.  Cellulose separator is proven to be preferred for LICs compared to polymer based. article info Article history: Received 25 March 2014 Received in revised form 27 May 2014 Accepted 17 June 2014 Available online 25 June 2014 Keywords: Li-ion capacitor Activated carbon Hard carbon Cathode binder SLMP loadings Types of separator abstract The Li-ion capacitor (LIC) is composed of a lithium-doped carbon anode and an activated carbon cathode, which is a half Li-ion battery (LIB) and a half electrochemical double-layer capacitor (EDLC). LICs can achieve much more energy density than EDLC without sacrificing the high power performance advan- tage of capacitors over batteries. LIC pouch cells were assembled using activated carbon (AC) cathode and hard carbon (HC) þ stabilized lithium metal power (SLMP ® ) anode. Different cathode configurations, various SLMP loadings on HC anode, and two types of separators were investigated to achieve the optimal electrochemical performance of the LIC. Firstly, the cathode binders study suggests that the PTFE binder offers improved energy and power performances for LIC in comparison to PVDF. Secondly, the mass ratio of SLMP to HC is at 1:7 to obtain the optimized electrochemical performance for LIC among all the various studied mass ratios between lithium loading amounts and active anode material. Finally, compared to the separator Celgard PP 3501, cellulose based TF40-30 is proven to be a preferred separator for LIC. © 2014 Elsevier B.V. All rights reserved. 1. Introduction People are always pursuing more efficient energy storage de- vices which can provide high energy density, good power perfor- mance and long cycle life. The electrochemical double-layer capacitor (EDLC) contains two symmetrical activated carbon elec- trodes with high surface area and porous structure. Although the EDLC has the characteristics of high power and long cycle life, the energy density of a EDLC is less than 10% of that of a Li-ion battery (LIB), which restricts its application in the field of hybrid electric vehicles (HEVs), electric vehicles (EVs) and other large-scale energy storage systems. Therefore, in recent years considerable research has been focused on the development of a high energy density EDLC. Among all the energy storage systems that have been investigated and developed in the last few years, Li-ion Capacitors (LICs) have emerged to be one of the most promising because LICs achieve higher energy density than conventional EDLCs, and better power performance than LIBs as well being capable of long cycle * Corresponding author. Fax: þ1 704 868 5496. E-mail address: Yangxing.li@fmc.com (Y. Li). Contents lists available at ScienceDirect Journal of Power Sources journal homepage: www.elsevier.com/locate/jpowsour http://dx.doi.org/10.1016/j.jpowsour.2014.06.090 0378-7753/© 2014 Elsevier B.V. All rights reserved. Journal of Power Sources 268 (2014) 841e847