Electrolyte

Additives In Aqueous Electrolytes

Electrolyte

Additives In Aqueous Electrolytes

Additives in aqueous electrolytes increase performance in Zn batteries Aqueous electrolytes continue to attract attention, especially for post-lithium ion chemistries. Zinc-ion batteries have a high energy density, but parasitic side-reactions and non-uniform dendrite growth on Zn anodes limit their usage. Zhang et al. used a NH4H2PO4 additive to regulate the Zn+ deposition and avoid dendrite formation. In this case, the NH4+ is preferentially absorbed on the Zn to block free water molecules, in what the authors call “shielding effect”, while the H2PO4- forms a buffer that maintains a favorable pH (Figure 1). This results in more uniform and stable deposition/stripping of the Zn ion, resulting in improved capacity retention in Zn//Zn and Zn//Cu cells. Highly reversible Zn plating/stripping behaviors were observed; the Zn//Zn symmetric cell stably cycled 2100h at 1 mA cm-2, 1900 h at 4 mA cm-2 and 930 h at 10 mA cm-2. A Zn//Cu asymmetric cell displayed a high average coloumbic efficiency of 99.4% over 1000 cycles. The NHP additive also boosted teh electric chemical performance of Zn//MnO2 full cells and Zn//activated carbon capacitors.

Additives such as NH4H2PO4 (NHP) can reduce dendrite growth and parasitic side reactions in aqueous zinc batteries.

Figure 1.

Academia | P. 220 Source: W. Zhang, Y. Dai, R. Chen, Z. Xu, J. Li, W. Zong, H. Li, Z. Li, Z. Zhang, J. Zhu, F. Guo, X. Gao, Z. Du, J. Chen, T. Wang, G. He, I. P. Parkin

Figure 2.

Extracted from the PDF; charts and images may read imperfectly.