The electrode structure affects the charge-transfer process, electronic conduction, mass transport within pores, and therefore electrochemical performance of batteries ¹. In this study, a hierarchical carbon network with hollow core and mesoporous shell (HCMS) ^2,3 and activated carbon (AC) are employed as supports for Li₄Ti₅O₁₂ (LTO) anode material. LTO/HCMS composite shows higher capacity than LTO/AC composite under high-rate and low-temperature conditions. In order to study the performance-structure relationship, electrochemical impedance spectroscopy (EIS) technique with transmission line model (TLM), together with material characterization, are utilized to study the electronic conduction process, mass transport within the pores and the charge-transfer process of LTO/C composites and carbon supports.

Fig. 1 TEM images of (a) HCMS and (b) AC carbon supports; (c) Nyquist plots (symbol), and plots (line) fitted with equivalent circuit model for symmetric HCMS/HCMS (○, solid line) and AC/AC (□, broken line) coin-cells in 1M LiPF₆ in EC/EMC/DMC (1:1:1).

References

[1] N. Ogihara, S. Kawauchi, C. Okuda, Y. Itou, Y. Takeuchi, and Y. Ukyo, J. Electrochem. Soc., 159, A1034 (2012)

[2] F. Li, M. Morris, and K.Y. Chan, J. Mater. Chem., 21, 8880 (2011)

[3] C. Yang, C.Y.V. Li, F. Li, and K.Y. Chan, J. Electrochem. Soc., 160, H271 (2013)

Acknowledgements

This project is financially supported by Innovation and Technology Commission, Hong Kong (Project No.: ITS/076/11), HKU Seed Fund for Basic Research (Project No.: 201605159011), and University Development Fund for Clean Energy and Environment.