UNIVERSITY OF CALIFORNIA Los Angeles Graphene Supercapacitors: Charging Up the Future A dissertation submitted in partial satisfaction of the requirements for the degree Doctor of Philosophy in Chemistry by Maher El-Kady 2013 © Copyright by Maher El-Kady 2013 ABSTRACT OF THE DISSERTATION Graphene Supercapacitors: Charging Up the Future by Maher El-Kady Doctor of Philosophy in Chemistry University of California, Los Angeles, 2013 Professor Richard B. Kaner, Chair Batteries run just about everything portable in our lives such as smartphones, tablets, computers, etc. While we have become accustomed to the rapid improvement of portable electronics, the slow development of batteries is holding back technological progress. Thus, it is imperative to develop a new energy storage technology providing devices that are compact, reliable, and energy dense, charge quickly, and possess both long cycle life and calendar life. Using a consumer grade LightScribe DVD burner, we have developed graphene supercapacitors with high charge storage capacity while providing 20 times more power than supercapacitors currently available. Interestingly, this direct writing technique offers a way to pattern graphene precisely without using masks or cleanroom operations, thus giving the flexibility to produce supercapacitors in various sizes and architectures at low cost. The miniaturization of the electrodes to the microscale results in enhanced charge storage capacity and rate capability. In addition, by combining graphene with conducting polymers and metal oxides, this work demonstrates pseudo-capacitors and hybrid supercapacitors with enhanced charge storage capacities that rival those of thin film batteries, while they can be recharged in less than a ii second. Great efforts are currently in progress between UCLA and Maxwell Technologies to move this technology from the laboratory to the industrial scale. In addition, this work describes several other applications that take advantage of the fascinating properties of graphene including lithium ion batteries and micro-batteries, sensors and catalysis. iii The dissertation of Maher El-Kady is approved Xiangfeng Duan Paul S. Weiss Yang Yang Richard B. Kaner, Committee Chair University of California, Los Angeles 2013 iv I dedicate this thesis to all my family members for their constant support and unconditional love. I love you all! v Table of Contents 1. OVERVIEW, MOTIVATION AND SCOPE OF THE DISSERTATION .............................................................. 1 1.1 Thesis Overview .................................................................................................................................. 1 1.2 Motivation and Objectives .................................................................................................................. 4 1.3 Scope of the Dissertation .................................................................................................................... 9 Bibliography ............................................................................................................................................ 12 2. INTRODUCTION TO SUPERCAPACITORS ................................................................................................ 14 2.1 How Energy Storage Has Changed Our Lives .................................................................................... 14 2.2 Energy and Power ............................................................................................................................. 16 2.3 What Is a Supercapacitor? ................................................................................................................ 16 2.4 Supercapacitors Performance Characteristics .................................................................................. 19 2.5 Applications of Supercapacitors........................................................................................................ 21 2.5.1 Industrial Applications .......................................................................................................... 21 2.5.2 Transportation ...................................................................................................................... 21 2.5.3 Consumer Electronics ........................................................................................................... 23 2.5.4 Energy Harvesting ................................................................................................................. 24 2.5.5 Grid Storage .......................................................................................................................... 26 2.5.6 Aircraft .................................................................................................................................. 26 2.5.7 Medical.................................................................................................................................. 27 2.5.8 Military .................................................................................................................................. 27 2.6 Capacitive Energy Storage Mechanisms ........................................................................................... 27 2.7 Materials For Supercapacitors .......................................................................................................... 30 2.7.1 Materials for Electric Double Layer Capacitors ..................................................................... 30 2.7.1 Materials for Pseudo-capacitors ........................................................................................... 33 2.7.1 Materials for Hybrid Capacitors ............................................................................................ 35 2.8 Graphene: Potential Candidate for High-Performance Supercapacitors .......................................... 36 2.9 Miniaturization of Energy Storage Units ........................................................................................... 39 2.10 Micropower Sources ....................................................................................................................... 41 2.10.1 Micro-Supercapacitors ........................................................................................................ 42 Bibliography ............................................................................................................................................ 44 vi 3. LASER SCRIBING OF HIGH-PERRFORMANCE AND FLEXIBLE GRAPHENE-BASED ELECTROCHEMICAL CAPACITORS ............................................................................................................................................... 48 3.1 Abstract ............................................................................................................................................. 48 3.2 Introduction ...................................................................................................................................... 48 3.3 Results and Discussion ...................................................................................................................... 50 3.4 Conclusions ....................................................................................................................................... 62 3.5 Materials and Methods ..................................................................................................................... 62 3.6 Appendix to Chapter 3 ...................................................................................................................... 69 Bibliography ............................................................................................................................................ 86 4. SCALABLE FABRICATION OF HIGH-POWER GRAPHENE MICRO-SUPERCAPACITORS FOR FLEXIBLE AND ON-CHIP ENERGY STORAGE ....................................................................................................................... 90 4.1 Abstract ............................................................................................................................................. 90 4.2 Introduction ...................................................................................................................................... 90 4.3 Results and Discussion ...................................................................................................................... 93 4.4 Conclusions ..................................................................................................................................... 108 4.5 Materials and Methods ................................................................................................................... 111 4.6 Appendix to Chapter 4 .................................................................................................................... 114 Bibliography .......................................................................................................................................... 134 5. RATIONAL DESIGN AND ENGINEERING OF THREE-DIMENTIONAL GRAPHENE/MnO2 ELECTRODES FOR HIGH-PERFORMANCE HYBRID SUPERCAPACITORS AND MICRO-SUPERCAPACITORS ........................... 139 5.1 Abstract ........................................................................................................................................... 139 5.2 Introduction ...................................................................................................................................