Improvement of Li Metal Anode Cycleability By Na+ Addition in Electrolyte

Li metal is an ideal anode material for Li batteries because of its low redox potential, lightest equivalent weight, and high specific capacity^[1]. However, in aprotic electrolytes, dendrite formation and low coulomb efficiency of Li in charge-discharge cycles have been reported to primarily limits the development of rechargeable Li metal batteries^[2]. Adding selected cations into electrolyte, such as Na⁺, Al³⁺, Sn²⁺, Mg²⁺, has been studied as an effective method to suppress dendrite growth and increase the coulombic efficiency ^[3-5].

In this work, Li deposition and oxidation characteristics in electrolyte of 1M LiClO₄ / EC+DMC (1:1) added with 0.1M NaClO₄ was studied on a novel substrate, this substrate was a Li-Zn alloy substrate prepared via in-situ deposition of Li on ultrasonic assisted electrodeposited Zn layer. The galvanostatic charge-discharge testing results indicate that adding of a small amount of Na⁺ into the electrolyte can increase the potential of Li deposition and reduce the oxidation potential of the deposited Li, and the Li-Zn alloy substrate formed in this way can effectively improve the morphology of the Li deposit. On the basis of both of these two efforts, the charge-discharge cycleability of Li is thus greatly improved with high coulombic efficiency. The effect and cycleability of the substrate formation on the morphology of the deposited Li layer , the mechanism of the addition of Na⁺in electrolyte on Li deposition and the characteristics of the SEI film formed on the Li-Zn alloy are studied in detail.

Fig. 1 Charge/discharge profile of Li on Li-Zn substrate in different electrolytes.

References

[1] S. Chandrashekar, Nicole M. Trease, Hee Jung Chang, Lin-Shu Du, Clare P. Grey, A. Jerschow, Nat. Mater. 11 (2012) 311-315.

[2] Y. Lu, S. K. Das, S. S. Moganty, L. A. Archer, Adv. Mater. 24 (2012) 4430-4435.

[3] J. K. Stark, Y. Ding, P. A. Kohl, J. Electrochem. Soc. 160 (2013) D337-D342.

[4] M. Ishikawa, M. Morita, Y. Matsuda, J. Power Sources 68 (1997) 501-505.

[5] M. Ishikawa, S.-i. Machino, M. Morita, J. Electroanal. Chem. 473 (1999) 279-284.

Statement:

The novelty of this work: (1) in-site formation of Li-Zn alloy substrate is a novel substrate for Li cycling with improved morphology; (2) Na⁺ addition into the electrolyte can improve the cycling performance of Li.

Relating topic: Electrode Materials (Li batteries anode)