Advanced Characterization Technologies for Secondary Batteries

Transmission electron microscopy (TEM) has been widely employed as an important technique for detecting morphology in various secondary battery applications. When integrated with diverse accessories, TEM could attain sub-angstrom level detection, cryogenic TEM (cryo-TEM), and other functionalities, which enables the observation and comprehension of the microstructure of secondary battery materials, as well as structural variations during battery charging and discharging processes. In this chapter, essential structures, main functions, and sample preparation methods of TEM are introduced. Additionally, applications of TEM in characterizing materials used in secondary batteries are discussed and summarized. The aim is to provide essential guidance for employing TEM and to facilitate its future development.

This chapter discusses the major challenges of characterizing the microstructure and morphology of battery materials, as well as the limitations of current characterization techniques in lithium-ion batteries. To address these challenges, the dual-beam system of focused ion beam scanning electron microscopy (FIB-SEM) emerges as one promising solution. The FIB-SEM system enables accurate manipulation and analysis of battery materials from both micro- and nano-scale perspectives, thus providing valuable insights for the development of high-performance and safe lithium-ion batteries.

Atomic Force microscope (AFM) not only reveals the surface morphology of substances at the nanoscale and molecular level but also enables the measurement of extremely weak forces, which allows for the study of weak interactions between molecules. Moreover, the AFM possesses certain spatial resolution ability. As a valuable tool in secondary battery research, AFM could reveal the surface microscopic morphology of the electrode in real time through the interaction between atoms from the tip and the electrode surface. It offers nanoscale surface information of the electrode from both chemical and physical perspectives, thus establishing essential guidance for further modification of electrode materials and electrolytes. This chapter reviews the state-of-art application progress of AFM in the study of secondary batteries, including cathode materials, anode materials and solid electrolyte interface. 

As an important surface analysis technique based on the photoelectric effect, X-ray Photoelectron Spectroscopy (XPS) enables both qualitative and semiquantitative analysis of the elemental composition and chemical state of the solid material surface, and has thus been widely applied in secondary batteries. In this chapter, we first delve into a detailed introduction of the working principle, main functions, analytical capabilities and technical features of XPS. Following this, we outline various types of XPS spectral peaks and elucidate general principles for data analysis. Then, the preparation of diverse XPS specimens along with their packaging and transfer processes are introduced. Last but not least, we comprehensively summarize and discuss the application of XPS in secondary batteries, including the characterization of electrode material composition, charge/discharge mechanism, solid electrolyte interphase (SEI) structure, etc. Additionally, we provide examples of the insightful information acquired through XPS and demonstrate how this data aids researchers in achieving a more profound understanding of secondary batteries, which highlights the increasingly important role of XPS in the development of secondary batteries. 

In recent years, Time of Flight-Secondary Ion Mass Spectrometry (TOFSIMS) has been widely employed as a powerful surface characterization tool in secondary battery investigations. In this chapter, we introduced the essential working principle, fundamental functions, and basic components of TOF-SIMS, which hopefully could provide useful insights for potential users and readers with particular interests in TOF-SIMS measurement. Additionally, state-of-the-art practical applications and research progress of TOF-SIMS in secondary batteries, including electrode materials and electrode/electrolyte interfaces, were thoroughly reviewed and discussed.

As a well-established method, neutron diffraction has been widely adopted to characterize the atomic structure of materials. One of the most distinct advantages of neutron diffraction refers to its high sensitivity to most light elements (e.g., lithium), which could distinguish isotopes and identify adjacent elements. Moreover, magnetic structure may also be probed. More importantly, the penetration depth of neutrons is thick enough for battery detection with centimeter scales. For secondary batteries, neutron diffraction has shown advantages in determining phase structure and ion diffusion in active materials, which are critical issues in battery studies due to the dominant charge and energy transport functions of active ions. Moreover, neutron diffraction also exhibits superior performance in revealing lithium coordinates in lattice and related occupations, as well as visualizing the diffusion path of lithium atoms, which may not be completed via other characterizations. This chapter aims to comprehensively review the working mechanism and main research progress of neutron diffraction in secondary batteries. The essential background, working principle and practical applications of neutron diffraction on the cathode, anode, solid-state electrolytes and full batteries, as well as its data analysis, are introduced and discussed.

Electrode materials undergo complex structural variations during the operation of secondary batteries. Three-dimensional characterization of these changes offers researchers a more in-depth and comprehensive insight into the dynamically evolving complex interactions compared to the conventional two-dimensional characterization. Synchrotron radiation X-ray tomography technology, which is capable of non-destructively conducting multi-scale and 3D imaging of battery components in both static and operational states, has emerged as an indispensable tool for enhancing further understanding of secondary battery research in recent years. Here, in this chapter, the integration of synchrotron radiation X-ray tomography technology and pertinent knowledge within the context of secondary battery research is undertaken, which is aimed at advancing the application of synchrotron radiation X-ray tomography technology in future secondary battery research. This chapter initiates by elucidating the essential principles and experimental apparatus of synchrotron X-ray tomography technology, followed by exploring its applications in both positive and negative electrode materials of secondary batteries. Last, typical application software and cases of data processing are presented and introduced. We anticipate that this chapter will enhance the readers' understanding of synchrotron X-ray tomography technology, and provide novel insights to inspire its application in secondary battery investigations.

Secondary batteries have been widely studied due to their highly efficient electrical and chemical energy-converting performance. Further improvement of these batteries is expected to meet the growing demands of the economy and technology. Various advanced characterization techniques have been applied in secondary batteries to gain a deeper understanding of electrochemical evolution and detection in the discharge/charge process. The ultrasound technique, with its high sensitivity, low cost and real-time detection ability, shows great potential for the characterization of secondary batteries. In this chapter, we introduce the fundamental principles of the ultrasound technique and summarize its applications in secondary batteries.