Lithium-Ion Supercapacitors

Fundamentals and Energy Applications

Lei Zhang, David P. Wilkinson, Zhongwei Chen, Jiujun Zhang, Lei Zhang, David P. Wilkinson, Zhongwei Chen, Jiujun Zhang

• Publisher: CRC Press
• Year: 2018
• Print ISBN: 9781138032194
• eBook ISBN: 9780429959592
• Topic: Physical Sciences
• Subtopic: Industrial & Technical Chemistry

The book provides a comprehensive understanding of the principles for operating lithium-ion supercapacitors (LISCs), their challenges, technological trends and perspectives. LISC technology has high potential to replace conventional rechargeable batteries such as lead-acid and nickel metal hydride batteries for automotive, portable electronics, and stationary applications. The book offers detailed analysis of LISCs at the material, component, and system levels to evaluate the different approaches to their integration. It also discusses economics, market, manufacture, and commercialization status of LISCs. It is an up-to-date study of an emerging field, written by experts, ideal for those in academia and industry who want a detailed explanation of the technology.

1 Fundamentals of Lithium-Ion Supercapacitors

Zhenjiang He
Central South University

Yuyu Liu
Shanghai University

CONTENTS

1.1 History

1.2 Lithium-Ion Supercapacitor Physics/Chemistry/Electrochemistry

1.3 Lithium-Ion Supercapacitor Components (Anode, Cathode, Electrolyte, Separator/Membranes, Current Collector)

1.3.1 Lithium-Ion Containing Metal Oxides

1.3.2 Polyanionic Compounds

1.3.3 Graphite

1.3.4 Transition Metal Oxides

1.4 Electrochemical Performance (Energy/Power Densities, Capacity, Charge–Discharge, Cycle Life, Failure Mode Analysis, Modeling, Codes, and Standards)

1.4.1 Cyclic Voltammetry

1.4.2 Chronopotentiometry

1.5 Summary

References

1.1 HISTORY

In the nineteenth century, German scientist Helmholtz discovered the double electric layer that forms on the interface between a charged electrode and an electrolyte solution. In the middle of the twentieth century, Grahame further improved the double electrode layer theory and laid the foundation for the application of supercapacitors. Since the 1990s, with the development and popularity of electric vehicles, development of high-energy pulsed-power sources are receiving more attention. At present, traditional capacitors have low energy density, and lithium-ion batteries have low power density [1–4]. Therefore, a single application of traditional capacitors or lithium-ion batteries can hardly meet these demands of specific electric power tools. To solve this problem, two kinds of methods have been put forward. First, the combined utilization of traditional capacitors and lithium-ion batteries has been proposed to satisfy these demands. Combining the high power density of a traditional capacitor with the high energy density of a lithium-ion battery can satisfy these demands to a certain extent. However, this combination requires other additional accessories to meet regulatory functions, which reduces the overall energy density by increasing the weight of the device. Second, new types of hybrid capacitors based on capacitor technology and the electrochemical principle have been developed to satisfy these demands [5–7].

Since the beginning of the 1990s, many famous research institutions and large corporations moved their research focus from electric double-layer capacitors (EDLCs) to new style capacitors. In 1990, Giner, Inc. reported an aqueous pseudo-capacitor, which used noble metal oxides as electrode materials [8]. In order to further improve the specific capacity of capacitors, D.A. Evans, in 1995, proposed a significant concept of electrochemical hybrid capacitor combining ideal polarized electrodes and Faraday electrodes [9]. In 1997, a Russian company called ESMA publicized a new hybrid capacitor system (NiOOH/activated carbon [AC]), which revealed a novel technology that integrates battery materials and capacitive materials for electrochemical devices. In 2001, G.G. Amamcci reported a nonaqueous hybrid capacitor that used the lithium-ion battery material (Li₄Ti₅O₁₂) and AC as electrode materials, which is regarded as a milestone in the development of electrochemical hybrid capacitor. In 2005, Fuji Heavy Industries (FHI) publicized a novel electrochemical hybrid capacitor, which added lithium-ions to improve energy density that they named the lithium-ion supercapacitor (LISC). The key point of the LISC developed by FHI is doping anode materials (polyacene) with lithium in advance, which resulted in improved energy density of the anode by more than 30 times compared to the AC. In addition, the lithium doping can dramatically decrease the anode potential, which makes the individual cell voltage increase about 1.5 times, further improving the energy density. In 2006, Hatozaki reported a new style LISC, which used AC as the cathode material and a carbon material preintercalated with lithium as the anode material, with the operating voltage of this LISC reaching 3.8 V in organic electrolytes.

In the twenty-first century, increasing attention has been paid to the research of LISC. Nowadays, carbon materials (such as graphene, AC, and graphite), transition metal oxide, and transition metal sulfide have been widely studied and developed as electrode active materials because of the excellent electrochemical performance they display [10–15]. Many methods (such as hydrothermal treating, heat treatment, and atmosphere control) have been applied to design the morphology and structure of electrode materials and to enhance their electrochemical properties. Against the background of conventional energy crisis and environmental damage, the research on LISC becomes a popular area in the twenty-first century, and most of the countries in the world have invested many human and financial resources on it.

1.2 LITHIUM-ION SUPERCAPACITOR PHYSICS/CHEMISTRY/ELECTROCHEMISTRY

The LISC consists of an anode, cathode, electrolyte, separator, current collector, capacitor pack, etc. A LISC, in essence, is a hybrid capacitor, which can be understood as the active material of one or two electrodes of a supercapacitor substituted by a lithium-ion battery material and operated in an electrolyte with the lithium content. Obviously, as a hybrid capacitor, the energy storage mechanism of LISCs includes not only redox reaction of lithium-ion batteries, like lithium intercalation/transformation, alloying, etc. but also electric double layer and faradaic pseudocapacitance.

The energy storage of EDLCs is dependent on the electrostatic adsorption of cations and anions on the surface of an electrode. During the charge process, cations and anions will migrate to the cathode or anode under the electric field, separately. In turn, during the discharge process, these ions will be desorbed from cathode or anode and migrate the opposite way. The reaction process of double layer capacitor can be displayed as follows:

EA+A− ⇋ EA+/A− + e− (1.1)

EC+C+ ⇋ EC−/C+ + e−, (1.2)

where EAandECare the anode and cathode, respectively; A−andC+, the anion and cation; and e−, the electron.

In general, the activated carbons with high specific surface areas are utilized as the electrode material of electric double layer capacitors, and the capacitance of one electrode is calculated using the following equation:

C=A (εrε0)d, (1.3)

where C is the capacitance of one electrode; A, the effective specific surface area of activated carbon; εr, the permittivity of electrolyte solution; ε0, the permittivity of vacuum; and d, the distance of electrodes.

The basis of faradaic pseudocapacitance is the redox reaction between electrode materials and ions in the electrolyte, which can be further subdivided into three different types: redox reaction of transition metal oxides, protonation reaction of conducting polymers, and reversible absorption of hydrogen ions. Take MnO₂ as an example; the reaction process of faradaic pseudocapacitance can be displayed as follows:

MnO2+ M++ e−⇋ MnOOH, (1.4)

where M+=Li, Na, K.

Until now, there are many mechanisms of energy storage in a lithium-ion battery, such as intercalation reactions, alloying reactions, phase transformations, conversion reactions, free radical reactions, electrodeposition, interfacial interactions, and surface adsorption.

The typical principle of different capacitors is illustrated in Figure 1.1 [16]. The configuration of LISCs can be divided into two categories based on the electrolyte medium (aqueous and nonaqueous). Meanwhile, the LISC can be divided into two types, symmetric and asymmetric systems, based on the combination of capacitor materials and lit...

Table of contents

• Cover
• Half Title
• Title Page
• Copyright Page
• Table of Contents
• Editors
• Contributors
• Chapter 1 Fundamentals of Lithium-Ion Supercapacitors
• Chapter 2 Anodes of Lithium-Ion Supercapacitors
• Chapter 3 Cathodes of Lithium-Ion Supercapacitors
• Chapter 4 Electrolytes and Separators of Lithium-Ion Supercapacitors
• Chapter 5 Fabrication of Lithium-Ion Supercapacitors
• Chapter 6 Theoretical Modeling of Lithium-Ion Supercapacitors
• Chapter 7 Applications and Economics of Lithium-Ion Supercapacitors
• Index