Handbook of Solid State Batteries

The following sections are included:

• Preface
• Contents

The following sections are included:

• Introduction
• Defects and Disorders
• Structural Features
• Mechanisms of Ion Transport
• Ionic Conduction
• Thermodynamic and Kinetic Measurements on Solid Electrolyte Cells
• References

In this chapter, we review in-situ neutron techniques for studying lithium ion and solid-state rechargeable batteries. Three neutron measurement techniques, neutron powder diffraction (NPD), neutron reflectivity (NR), and neutron depth profiling (NDP) are discussed using specific examples. They are used to quantify the structure and the real-time distribution of Li in active battery components during battery operations, and gain new insights in the function and failure of battery systems. New opportunities of applying in-situ neutron diagnoses for studying the performance and lifetime of secondary batteries are also discussed.

In this chapter, we will discuss the principal advantages of using synchrotron methods for the real-time species-specific structural measurements of the active materials in batteries and related electrochemical devices. Specifically, we will look at the inherent versatility of and the remaining challenges with real-time measurement of X-ray absorption, a core-hole spectroscopy method that probes the local structure. The rich content of structural information using X-ray absorption will be discussed in the context of battery chemistry.

This chapter focuses on the recent development and optimization of analytical electron microscopy to understand the dynamic changes in the bulk and interfaces of electrodes and electrolytes within all solidstate batteries. Three major aspects are covered: (1) design and fabrication of all solid-state batteries that remain functional after careful focused ion beam (FIB) processing; (2) enablement of in-situ biasing in both FIB/SEM and transmission electron microscope and/or scanning transmission electron microscope (TEM/STEM); and (3) development of the fundamental understanding of the dynamic chemical and electronic processes at the solid/solid interfaces of electrode/electrolyte by high resolution imaging and electron energy loss spectroscopy (EELS). Our goal is to apply analytical microscopy to gain new insights that can help us make significant inroads towards understanding the basic science of ion transport, charge transfer and related phase transformations in electrochemical systems at the nanometer scale.

Various time-domain nuclear magnetic resonance (NMR) techniques are highly useful to study Li-ion dynamics in solid electrolytes and electrode materials from an atomic-scale point of view. In particular, by combining lithium NMR techniques being sensitive to Li jump processes on different length scales and time scales detailed information on activation energies, jump rates and diffusion pathways can be collected. This helps understand the relationship between local structure and dynamic parameters and assists in developing new materials for solid-state energy storage. In this chapter, we will review recent examples where NMR relaxation has been successfully applied to both highly conducting solid electrolytes and selected anode materials.

This chapter presents examples of the use of first principles computer simulations in the study of two families of solid electrolyte materials — namely the family of Li phosphate, phospho-nitride, and thiophosphate materials and the family of Li oxide garnet materials. The simulation work together with related experimental studies of these solid electrolytes supports the continued development of all-solid-state battery technology.

The following sections are included:

• Introduction
• Polymer Composites with Insulating Fillers
• Polymer Composites with Conductive Fillers
• Characterization of Interfacial Charge Transport
• Modeling
• Conclusion
• References

Metal fluorides have been considered attractive for a variety of applications due to their particular thermodynamic and ion conducting properties. For electrochemical energy storage their high enthalpy of formation and their relatively high density makes metal fluorides interesting as cathode materials. Moreover, fast fluoride ion conducting materials have been utilized in solid-state electrochemical devices such as solid-state batteries, fuel cells, sensors and electrochromic displays. In sensors, fluorides have been used for sensing various physical and chemical parameters. Recently, it was shown that metal fluorides can also be used as both active materials and solid electrolytes in so-called fluoride ion batteries which are based on reversible anion shuttle. Herein, mechanism of ion conduction in solids, current state of fast fluoride ion conductors based on fluorite and tysonite structures as well as of mixed compounds based on Pb, Sn, Bi and Sb will be reviewed and discussed. The discussion involves recent approaches to further increase the ionic conductivity in particular systems such as nanostructuring and tailoring of grain boundaries.

This chapter presents the state-of-the-art research in the field of thin film solid Li-ion electrolytes, especially materials grown directly onto a supporting electrode surface. These electrolytes are the key to realizing a truly interdigitated three-dimensional (3D) battery. Moving from inorganic materials to polymers, the available materials along with their synthesis techniques are reviewed. Lastly, we comment on the future prospects of thin film solid electrolytes with novel physio-chemical properties for next-generation solid-state Li-ion cells.

Charge-transfer reactions occur at the electrode/solid electrolyte interfaces, which play important roles for all-solid-state batteries with regard to their power density and stability of the cells. This chapter mainly describes recent research and development activities for reducing the charge-transfer resistance.

In this chapter, we provide a review of materials and designs for crystalline sulfide lithium ion conductors and their applications in solid-state batteries. Based on the merits and demerits of these electrolytes, strategies for the selection of materials and the design of crystalline sulfide lithium ion conductors are discussed in detail. Although crystalline sulfide-based solid electrolytes generally have high lithium-ion conductivity and excellent processability, limitations arising from their incompatibility with the electrodes are among the major challenges for practical deployment in solid-state batteries. After a comprehensive survey of the interfacial problems of solid-state batteries incorporating crystalline sulfide electrolytes, this chapter provides guidance on materials and cell designs to address issues of solid-state batteries that use this class of solid electrolytes.

Several ceramic oxide electrolytes exhibit super-ionic conductivity at 298K. However, numerous processing and integration challenges have slowed their adoption into solid-state battery technology. This chapter will discuss state-of-the-art super-ionic conducting oxides (SCO) and the details involved in articulating them into Li batteries.

Sulfide solid electrolytes are generally regarded as among the most promising solid electrolytes to construct bulk-type solid-state lithium batteries because of the high ionic conductivity, wide electrochemical window and low grain boundary resistance. Although ionic conductivities of some sulfides have almost exceeded that of organic solvent electrolytes used in the current lithium-ion batteries, they have not improved the power density of solid-state lithium batteries to be high enough for practical use. The rate-determining step is mass transport in a lithium-depleted layer formed at the interface between the cathode and the sulfide electrolyte. This chapter presents the origin of lithium depletion and some interface structures that enhance the power density on the basis of “nanoionics”. It reveals that interposition of oxide solid electrolytes at the interface suppresses the lithium depletion, reduces the interfacial resistance, and thus successfully enhances the power density.

Glass and glass-ceramic sulfide and oxy-sulfide solid electrolytes are reviewed with the aim to provide a summary of the previous and current state of the art research in this area. The review is limited to the single valent alkali cations Li⁺ and Na⁺ due to their dominant importance in lithium and sodium batteries. Some effort however is given to Ag⁺ and Cu⁺ cations due to their significant interest in specialty batteries. No coverage is given to the monovalent and divalent anions such as F⁻ and O⁼, and to the divalent cations such as Mg⁺⁺ and Ca⁺⁺ due to their very low ionic conductivity and to the lack of significant or indeed any solid state batteries using such chemistries. The focus of this review is on sulfide and oxy-sulfide glassy and glass-ceramic solid electrolytes due to the many orders of magnitude higher ionic conductivities of the sulfide over those of the corresponding oxide materials. Out of this review that will focus mostly on the composition, chemistry, and structure dependence of the ionic conductivity of these electrolytes, it is hoped to establish the current state of the art in this field and provide some comments on future prospects. Break-through advances in the ionic conductivity of solid electrolytes will enable solid state battery systems with improved safety, cost, form factor, current, voltage, and energy and power densities.

In this chapter, we describe crystalline ion-conducting complexes formed by akali metal salts and poly(ethylene oxide). A variety of factors influencing the conductivity of such complexes are presented. Electrochemical testing of these materials in lithium and sodium rechargeable batteries demonstrate that crystalline polymer/salt complexes can be used as electrolytes in all-solid-state energy storage devices.

This chapter discusses polymer electrolytes, their characterization, and their application in solid-state batteries. The concept of a material that acts as both the physical separator and the electrolyte while maintaining good contact with the electrodes through many charge/discharge cycles has motivated research on polymer electrolytes for over three decades. Beginning with poly(ethylene oxide) (PEO) as a host matrix for lithium salts, which is still the focus of many investigations, this review covers a variety of solvent (liquid)-free systems as well as plasticized or gel electrolytes. Several strategies for improving mechanical and electrical properties such as forming blends, organic/inorganic composites, or copolymerization are also described. Some of the most commonly used characterization tools are briefly discussed, including thermal analysis, X-ray diffraction, electrical impedance, and vibrational and nuclear magnetic resonance spectroscopies. Finally, a brief survey of power source applications of polymer electrolytes ranging from microbatteries to large format electric vehicle batteries is given.

All solid-state thin film batteries offer numerous advantages over conventional batteries where a small footprint and very thin profile are required, such as applications for on-board micro-chip power for micro-sensors, small medical implantable devices, radio frequency identification (RFID) cards, among many others. Thin film batteries also offer outstanding cycle life and safety relative to conventional lithium-ion cells, albeit at a cost of high substrate and packaging mass compared to the mass of active electrode material. The thin film battery components can be fabricated by a wide range of deposition and patterning technologies, most of which are compatible with microelectronic fabrication techniques. Many different materials can be used for the anode, cathode and electrolyte, which offer flexibility for tailoring the performance of the cells to a particular application. With ongoing advancements in low power electronics and energy harvesting, coupled with new developments in higher energy thin film electrodes and higher conductivity thin film solid electrolytes, the future prospects are excellent for widespread applications of thin batteries.

Bulk solid-state batteries are uniquely suited to enable the reversible electrochemical utilization of positive conversion materials. In this chapter, we will investigate how the confinement of electro-active species in a solidstate electrolyte improves and changes the electrochemistry of S and FeS₂. Like their conventional liquid cell counterparts, solid-state conversion electrodes often suffer from poor volumetric energy density. We will also survey the recent strategies aimed at increasing the energy density of S and FeS₂ solid-state electrodes.

The following sections are included:

• Abstract
• Introduction
• Multi-functional Efficiency
• Approaches for Creating Multi-functional Energy Storage Devices
• Development of Structural Energy Storage Devices
• Conclusions
• References

Traditional batteries suffer from a fundamental tradeoff between power density and energy density. This chapter introduces a possible solution in the form of three-dimensional batteries. In theory, non-planar electrodes should be able to facilitate ion diffusion and support large mass loadings while preserving a small footprint area. The advantages and disadvantages as well as the progress for a number of designs are described in the upcoming sections.

In this chapter, the consequences of utilizing 3D-structured electrodes in batteries are explored by electrochemical modeling techniques, especially for microbattery applications. It is shown that, contrary to conventional thin-film batteries, 3D-architectures give rise to large current inhomogeneities in the cell. This, in turn, causes inabilities to deliver either the target capacity or power, if not particular measures are taken into account when designing the cell structure. It is also shown that the optimal design is highly dependent on the electrode and electrolyte materials used.

Silver ion conducting electrolytes are being explored as a material to be used in solid state batteries. This chapter provides a review of the advances in silver ion conducting solid electrolytes over the last 20 years. We discuss the advances that have been made in the synthesis of new electrolyte materials and provide conductivity values for new electrolytes reported. We then turn to a summary of the models of the origin and enhancement of silver ion conductivity in solid electrolytes with focus on those that have been proposed more recently. Finally, we review the progress of solid state batteries and include values for the reported energy density and voltage of the cells.

The following section is included:

• Index