Solid Electrolyte Interface in Zn-Based Battery Systems

Abstract

Due to its high theoretical capacity (820 mAh g^-1), low standard electrode potential (- 0.76 V vs. SHE), excellent stability in aqueous solutions, low cost, environmental friendliness and intrinsically high safety, zinc (Zn)-based batteries have attracted much attention in developing new energy storage devices. In Zn battery system, the battery performance is significantly affected by the solid electrolyte interface (SEI), which is controlled by electrode and electrolyte, and attracts dendrite growth, electrochemical stability window range, metallic Zn anode corrosion and passivation, and electrolyte mutations. Therefore, the design of SEI is decisive for the overall performance of Zn battery systems. This paper summarizes the formation mechanism, the types and characteristics, and the characterization techniques associated with SEI. Meanwhile, we analyze the influence of SEI on battery performance, and put forward the design strategies of SEI. Finally, the future research of SEI in Zn battery system is prospected to seize the nature of SEI, improve the battery performance and promote the large-scale application.

Keywords: Artificial SEI; In situ SEI; Solid electrolyte interface; Solvated structure; Zn-based battery.

Fig. 1

Part of the development history of Zn batteries

Fig. 2

a Schematic diagram of traditional SEI mosaic model; b Schematic diagram of SEI Inlaid model [29]; Copyright 2020, Wiley–VCH. c Schematic diagram of multilayer SEI structure [29]. Copyright 2020, Wiley–VCH

Fig. 3

a Helmholtz model, the distance between positive and negative charges is a definite data; b Gouy–Chapman model considering diffuse layer, the distance between positive and negative charges is a variable; c Gouy–Chapman–Sternsilver model, ions have dimensions; d Electric double layer structure involving cation solvation

Fig. 4

Schematic diagram of energy band of electrolyte

Fig. 5

a SEM images of the morphologies grown at the Zn anode after plating/stripping [59]; Copyright 2019, Wiley–VCH. b In situ AFM images of Zn electrodeposits [61]; Copyright 2021, Royal Society of Chemistry. c TOF–SIMS mapping images (ZnO⁺ species) of the bare Zn (top) and ILG-Zn (bottom) [63]; Copyright 2021, Wiley–VCH. d 2D patterns of in situ ATR-FTIR spectra in first discharge and charge cycle [64]; Copyright 2022, Elsevier. e HAADF cryo-STEM imaging reveals an extended SEI layer on the dendrite, and element distribution in dendrite [66]; Copyright 2018, Elsevier. f Schematic illustration of Zn-ion diffusion pathway in EDA-VO crystal [69]; Copyright 2022, Wiley–VCH. g MD simulation of the desolvation process at the CNW surface [70]. Copyright 2021, Royal Society of Chemistry

Fig. 6

Schematic diagram of factors influencing SEI formation

Fig. 7

a The electrode surface before and after adding PDMS/TiO_2-x coating about distribution of Zn-ion concentration [75]; Copyright 2022, Wiley–VCH. b Function mechanism of the MOF coating layer to reject H₂O and construct a super-saturated front surface [76]; Copyright 2020, Wiley–VCH. c Cross-sectional SEM image of the Zn soaked in the electrolyte and the corresponding EDX maps. Scale bar, 2 μm [77]; Copyright 2021, Springer Nature. d Schematics of the behavior of bare Zn and Zn|In anodes in an aqueous ZnSO₄ electrolyte [78]. Copyright 2020, Wiley–VCH

Fig. 8

a Solvation structure of Zn ions in electrolytes with different concentrations [35]; Copyright 2018, Springer Nature. b Schematic illustration of Zn surface evolution and the SEI formation mechanism [38]; Copyright 2021, Wiley–VCH. c Schematic diagram of proposed Zn²⁺ conducting SEI [39]; Copyright 2021, Springer Nature. d The schematic descriptions of EDL structure after introducing Sac (Sac⁻ represents free Sac anions, Sac* represents the Sac anions chemically bonded with Zn surface) [40]; Copyright 2021, Wiley–VCH. e Schematic illustration of the interphase chemistry on Zn electrode [87]. Copyright 2022, Elsevier

Fig. 9

a Long-term galvanostatic cycling of symmetrical Zn cells with coated Zn plates and bare Zn plates [47]; Copyright 2019, Royal Society of Chemistry. b The rate performance of the full cells with varying Zn anodes operating [94]; Copyright 2021, ACS Publication. c LSV curves (HER) in ZnSO₄ electrolyte with different TMBAC concentrations [96]; Copyright 2022, Wiley–VCH. d The electrochemical stability window of aqueous electrolytes measured using polarization scanning on non-active Ti electrodes versus Zn/Zn²⁺ [39]. Copyright 2021, Springer Nature