Applications of advanced electron microscopy to study charge transfer and lithium-ion migration mechanisms in commercial lithium-ion batteries

On September 5, 2022, Tianjin University of Technology published a paper entitled "Elucidating the charge-transfer and Li-ion-migration mechanisms in commercial ^lithium-ion batteries with advanced electron" in Nano Research Energy microscopy"
.

Figure 1: (a) Principles of traditional characterization methods (GITT, EIS, CV curves, XRD spectra, XPS, Raman and NMR spectra) and the information obtained in the
cell.
(b) The principles of advanced electron microscopy (atomic imaging, EDS, EELS, differential phase contrast, electron holography) and the information
obtained from lithium-ion batteries.

Commercial lithium-ion batteries face different challenges
in different application areas.
In portable electronic products, the energy density of the battery is the core technical index; For electric vehicles, battery cost, cycle life and safety, and energy density (which determines the range per charge) are key parameters; In energy storage applications, battery cost, cycle life and safety are the three core influencing factors
in design.
In the electrochemical system of lithium-ion batteries, the electrode material is the core component of the battery, which has a significant impact on
the performance of commercial batteries.
In order to meet the performance requirements of the new generation of commercial lithium-ion batteries for long cycle life, high energy density and high safety, in addition to studying the inherent physical and chemical properties of materials, the most critical scientific problem is to clarify the structural evolution/dynamics of lithium ion embedding and extraction, and its influence on the electrode-electrolyte interface, and the solution of these problems plays an important role in supporting and guiding the material optimization and full battery design of commercial lithium-ion batteries
.

In this paper, the structure-activity relationship of commercial lithium-ion batteries is summarized into two categories: charge transfer and lithium-ion migration mechanisms, and the research progress of advanced electron microscopy in these two key processes is reviewed (Figure 1).

。 By comparing the characterization results obtained by traditional characterization techniques (such as XRD, XPS, etc.
), the advantages and limitations of commonly used electron microscopy (such as atomic imaging, electron diffraction, energy spectrum, electron energy loss spectroscopy, etc.
) and recently developed advanced electron microscopy characterization techniques (such as electron holography, differential phase contrast and in situ electron microscopy) in studying the charge transfer and ion migration mechanisms in commercial lithium-ion batteries are clarified, and the necessity of electron microscopy in combination with other technologies to obtain more comprehensive information is pointed out
。 This paper summarizes several important issues that have been paid attention to in recent years for commercial lithium-ion batteries: (1) the mechanism of transition metal dissolution and charge transfer during the charging and discharging of the cathode; (2) the structure and evolution of CEI and SEI in the long-term cycle; (3) The influence of
electrode structure and interface on lithium ion migration.
This paper can help researchers to better understand the relevant mechanisms on the microscopic scale of commercial lithium-ion batteries, and provide design strategies for the practical application of a new generation of high-performance batteries, which has certain guiding significance
.

Related Paper Information:

Li, C.
； Liu, B.
W.
； Jiang, N.
Y.
； Ding, Y.
Elucidating the charge-transfer and Li^- ion-migration mechanisms in commercial lithium-ion batteries with advanced electron microscopy.
Nano Res.
Energy 2022, 1: e9120031.
DOI: 10.
26599/NRE.
2022.
9120031.
https://doi.
org/10.
26599/NRE.
2022.
9120031.