The use of situ TEM in the lithium battery industry

With the vigorous development of new energy sources, the development of energy storage batteries has embarked on a fast track, with a variety of new lithium-ion batteries, sodium/potassium ion batteries and zinc ion batteries and other energy storage devices springing up! However, due to the complexity of the battery reaction during charging and discharging, the traditional characterization means cannot clarify the whole mechanism. Therefore, researchers have been thinking about how to monitor and characterize the morphology and structural evolution of battery materials, the electrochemical reaction process and the solid electrolyte interfacial film.

In recent years, with the development of in situ TEM, the above questions seem to be gradually answered. As a very practical high-end characterization technique, in situ TEM's extremely high resolution is very suitable for "in situ dynamic" observation of the microscopic morphology of various energy storage materials. In addition, in combination with Selected Area Electron Diffraction (SAED), Electron Energy Loss Spectroscopy (EELS) and Energy Spectrometry (EDX), we can obtain structural and chemical information about the material. As a result, the microstructural changes and electrochemical reactions of the entire electrode material during the charging and discharging process can be clearly presented, which allows researchers to easily understand the "heart" of the battery and publish high-level research results! Here we share with you the application of in-situ TEM in the field of energy storage with several high-level papers.

Solid-state battery

Nature: In situ TEM observation of lithium metal deposition-exfoliation behavior in hollow tubes

In solid-state lithium batteries, the deposition of lithium metal generates mechanical stresses as high as 1 GPa at an overpotential of 135 mV. In order to maintain electrochemical stability, solid-state lithium batteries need to be able to accommodate such mechanical stresses and maintain mechanical stability, which is very challenging. In view of this, Mr. Ju Li of MIT, in conjunction with Nobel Laureate Grandpa Goodenough, conducted a detailed study of the deposition-exfoliation behavior of lithium metal in mixed electron/ion conductor (MIEC) hollow tubes using in-situ TEM (Fig. 1). [1] The results of the study show that lithium metal can grow and shrink along phase boundaries in the form of single crystals in the tube via Coble creep. The unique structure of this MIEC hollow tube significantly reduces the mechanical stresses and thus contributes to the cycling performance of the material. In addition to this, the authors have also investigated the phase composition and organization during the deposition of lithium metal using selected area electron diffraction (SAED) technique in in situ TEM.

Figure 1: Deposition/exfoliation behavior of Li inside hollow carbon tubes

Lithium-sulfur batteries

Nature Energy: In-situ TEM observation of the structural evolution of "Li2S-graphene nanocapsules" during charge and discharge

Li-S batteries have received a lot of attention because of their high energy density. However, the cycle life of Li-S batteries is hindered by the large volume change of the cathode material during charging and discharging. Here, Prof. Jun Lu, Prof. Khalil Amine of Argonne National Laboratory, and Prof. Xiulei Ji of Oregon State University collaborated to design a "Li2S-graphene nanocapsule".[2] In order to investigate this structure, the Li2S-graphene nanocapsule was designed to be used as a nanocapsule. [In order to investigate the unique advantages of this structure, the authors used in-situ TEM to study the structural evolution of the material during charging and discharging. As shown in Figure 2, the size of the "Li2S-graphene nanocapsules" regularly increases and decreases during charging and discharging, but the volume change is only 10%. This stabilized structure allows the material to have a long cycle life. In contrast, pure Li2S particles break up quickly during charging and discharging (Fig. 3), and thus the capacity decays quickly.

Figure 2: Morphology of Li2S/graphene nanocapsules in different charging and discharging states

Figure 3: Morphology of pure Li2S material at different charging and discharging states

Lithium-ion/potassium-ion batteries

Advanced Energy Materials: In-situ TEM explains the reasons for the long cycle life of nano-hollow octahedral polyantimonate anode materials

In recent years, researchers have developed a myriad of electrode materials for storing alkali metal ions (e.g., Li+ and K+ ions) in secondary batteries. However, only a few electrode materials can be used as a generalized body material for storing alkali metal ions. Based on this, Prof. Yun Zhang and Prof. Hao Wu from Sichuan University have successfully designed and prepared a novel composite material (PAA⊂N-RGO) of poly(antimonate) nano-octahedra combined with nitrogen-doped graphene with internal voids through a synthesis strategy combining nanostructural modulation and conductive network construction. [3] Electrochemical measurements showed that the composite material could be stably cycled for 800 cycles with a capacity retention of 93.5% when used as an anode in lithium-ion batteries. In order to investigate the reason for the good cycling performance of the material, the authors used in-situ TEM to characterize the material in-situ. As shown in Fig. 4, the material first fills the void inward during lithiation discharge and subsequently expands outward, but due to the limitation of the externally coated graphene, the particle size grows very limited outward, and the total volume expansion is only around 130%, highlighting the advantages of this structural design.

Figure 4: Structural evolution of nano hollow polyantimonate particles upon lithiation

Sodium ion battery

Nano letters: In situ TEM observation of sodiation/desodiation process in Bi@Void@C materials

Metal Bi is a promising anode material for sodium-ion batteries with high mass specific capacity (386 mAh g-1) and volume specific capacity (3800 mAh cm-3). However, the huge volume expansion during sodiation severely impairs its electrochemical performance. Based on this, Mr. Yu Yan from CAS and Mr. Zhang Qiaobao from Xiamen University cooperated to design a Bi@Void@C material with "yolk-shell" structure.[4] The optimized Bi@Void@C material has been used in the design of the "yolk-shell" structure. [4] The optimized Bi@Void@C material has suitable voids, which can not only accommodate the volume expansion of Bi but also avoid compromising the bulk energy density of the material. In order to investigate the unique advantages of the "yolk-shell" structure of the Bi@Void@C material during sodiation, the authors used in situ TEM to study it in detail. From Figs. 5b-h, it can be found that the size of Bi particles gradually increases (from 160/131 to 224/187 nm) and the volume expansion is up to 274%/287% as the sodiation proceeds. On denaturation, the Bi particles then returned to their initial size, and no rupture of the material occurred throughout the denaturation/denaturation process (Video 3). In addition, the authors also used in situ TEM to observe the multiple sodiation/desodiation processes of the Bi@Void@C material (Fig. 5i-o), and no structural disruption was observed in any of them. Thus, Bi@Void@C exhibits excellent cycling stability as an electrode material for sodium-ion batteries.

Figure 5: Structure of Bi Void C material at different time and different number of cycles

At this point, I believe you have already understood the powerful functions of in-situ TEM. Given its dynamic, real-time, and accurate nature, researchers nowadays are increasingly favoring it to study the structural evolution and reaction mechanisms of energy storage materials in order to obtain deep, rich, and correct research results. But a practical question arises: where can we perform in-situ TEM tests?

Don't worry! In order to meet the needs of the majority of users, the domestic professional research team "Test Dog" officially launched the "in-situ TEM" characterization technology for the field of energy storage. Whether you are researching lithium-ion batteries, sodium-ion batteries and potassium-ion batteries or lithium-sulfur batteries, solid-state batteries and zinc-ion batteries, please give us your materials and we will guarantee you an accurate and perfect in-situ TEM data, which will pave the way for you to publish high-level papers!

References

[1] Y. Chen, Z. Wang, X. Li, X. Yao, C. Wang, Y. Li, W. Xue, D. Yu, S.Y. Kim, F. Yang, A. Kushima, G. Zhang, H. Huang, N. Wu, Y.W. Mai, J.B. Goodenough, J. Li, Nature, 578 (2020) 251-255.

[2] G. Tan, R. Xu, Z. Xing, Y. Yuan, J. Lu, J. Wen, C. Liu, L. Ma, C. Zhan, Q. Liu, T. Wu, Z. Jian, R. Shahbazian-Yassar, Y. Ren, D.J. Miller, L.A. Curtiss, X. Ji, K. Amine, Nature Energy, 2 (2017), 17090.

[3] B. Wang, Z. Deng, Y. Xia, J. Hu, H. Li, H. Wu, Q. Zhang, Y. Zhang, H. Liu, S. Dou, Advanced Energy Materials, 10 (2019), 1903119.

[4] H. Yang, L.W. Chen, F. He, J. Zhang, Y. Feng, L. Zhao, B. Wang, L. He, Q. Zhang, Y. Yu, Nano Lett, 20 (2020) 758-767.