Zinc metal is widely used as an anode in various aqueous systems. However, zinc anode suffers from the dendrite formation on the surface upon cycling leading to a poor cyclability of a cell and its termination due to short circuit. In this work, the effect of tetrapropylammonium hydroxide (TPAH) was studied as an electrolyte additive for aqueous Zn//ZnCl2 + LiCl//LiFePO4 battery. TPAH additive prolongs the battery cycle life depending on its concentration (0.01–0.1 M). The better capacity retention over 350 cycles was observed for a symmetrical Zn//ZnCl2 + LiCl//Zn cell with 0.05 M TPAH whereas without additives the cell worked for only 110 cycles. The mechanism of TPAH influence on capacity retention is proposed based on the results of SEM and XRD analysis of the Zn anode and FTIR and NMR studies of the electrolyte. The XRD patterns of the negative electrode of the cell with TPAH indicates that zinc was preferentially deposited in a highly oriented (002) direction, which is more resistant against dendrite formation. These differences in deposited structure of Zn dendrites were confirmed by SEM images as well. FTIR and NMR spectra showed that TPAH decomposes to propylamine (RnN+H) and propene during cycling. TPAH also has an effect on the size and uniform distribution of Zn growth sides.

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Rechargeable sodium-ion batteries are considered an alternative to Li-ion batteries in terms of largescale grid storage applications. Finding a cathode material with excellent performance plays a vital role in batteries. Cation doping is one of the methods to stabilize the crystal structure of layered cathode materials for sodium-ion batteries (SIBs) and enhance their electrochemical performance. In this work, we studied the effect of Fe doping on the properties of the Na2FexMn2-xO7 (x=0.0, 0.5) layered material, which was synthesized via a conventional solid-state method at 600 °C. The X-ray diffraction (XRD) analysis showed that the as-synthesized material was crystallized in a pure P2-type structure, except for the nondoped sample. The Fe-doped cathode samples delivered more stable cycle performance than a nondoped cathode material. An initial charge capacity of over 200 mAh g -1 was achieved for the Fedoped electrode. Meanwhile, the nondoped electrode delivered approximately 90 mAh g -1 of initial charge capacity. After 25 continuous charge-discharge cycles at a constant current (20 mA g -1 ), approximately 70% and 60% of the initial capacity remained for Fe-doped and nondoped electrodes, respectively.

Advanced cathode materials play a key role in enhancing the performance of Sodium-ion batteries (SIBs) [1]. Owing to their special layered structure, good electrochemical activity and appealing rate capabilities with stable cycling performance the layered transition metal oxides have been extensively studied. Among them Na2Mn3O7 is one of the promising cathode materials due to the low cost and high capacity [2]. However, the Jahn-Teller effect caused by Mn3+ leads to rapid capacity fading [3]. In this regard, partially substitution of transition metal elements into Mn-rich layered oxides were successfully reported as an effective method to inhibit the Jahn–Teller effect and improve cyclability [4].This research investigates developing Ni-substituted P1-type Na2Mn3-xNixO7 material where they are synthesized via sol-gel method. The effects of Ni-substitution amount on the structure / morphology and electrochemical properties of the cathode material are systematically studied. Acknowledgment This work was supported by the Nazarbayev University Faculty-development competitive research grant (080420FD1914) “Rational design of new anionic-redox based active material for rechargeable sodium-ion batteries” and by the Ministry of Education and Science of the Republic of Kazakhstan Grant (AP08856179), “Boosting the electrochemical performance of the cathode material for beyond lithium-ion batteries”. The author (AK) thank the social policy grant awarded to him by Nazarbayev University. References [1] T. Chen, W. Liu, Y. Zhuo, H. Hu, J. Guo, Y. Liu, J. Yan, K. Liu Mater. Chem. Front., 2019, 3, 2374 [2] J.Yang, M. Tang, H. Liu, X.Chen, Z. Xu, J. Huang, Q. Su, Y. Xia, Small 2019, 15, 1905311 [3] X. Ma, H. Chen, G.J. Ceder, J. Electrochem.Soc. 158 (2011) [4] D. Yuan, W.He, F.Pei, F. Wu, Y. Wu , J. Qian , Y. Cao, X. Ai , H. Yang ,J. Mater. Chem.A 1 (2013) 3895–3899.