Abstract
Lithium-ion batteries (LIBs) technology has come a long way from its inception to widespread deployment in a multitude of applications. Despite decades of research and development, the LIB industry remains bogged down by multi-steps fabrication, high cost of raw materials, and safety issues associated with Li ions. In recent years, the increasing demand for high-capacity and safer energy storage has attracted research attention on aqueous zinc-ion batteries (AZIBs), which is featured with suitable voltage, high capacity and much lower raw materials and production costs. However, as the Zn/electrolyte interface is not stable, they are plagued by undesired reactions and Zn dendrite growth, leading to compromised coulombic efficiency and cycle life. To solve these problems and speed up the commercialization process, stable Zn/electrolyte interfaces must be built, especially at harsh test conditions close to industrial level that few studies focus on. Here, we have proposed four distinct strategies aimed at stabilizing the anodic interface, thereby achieving superior Zn reversibility and battery cycling stability. These strategies can be classified into two main categories: electrolyte additive (Chapter 2-4) and surface modification (Chapter 5). The main contributions are summarized below: 1) Unlike most efforts focused on costly super-concentrated electrolytes and single additive species, we proposed a universal strategy to boost Zn reversibility in dilute electrolytes via adding carbonyl-containing organic solvents. Based on experimental investigations and multiscale simulations, the representative electrolyte with N-Methyl-2-pyrrolidone (NMP) polar additive is proved to assist in structural reshaping of Zn2+-solvation and stabilizing hydrogen bond network of water. This synergy is instrumental in contributing to suppressed water-induced parasitic reactions and dendrite formation, which enables high average coulombic efficiency of 99.7 % over 1000 cycles in Zn/Cu asymmetric cell, and an ultra-long cycling lifespan of 2000 cycles with 99.4 % capacity retention in Zn/VS2@SS full cell. Even with elevating cathodic mass loading (up to 9.5 mg cm-2), the cycling stability is still maintained. The proposed strategy provides new insight into electrolyte additive design and sheds the light on high-performance Zn-ion batteries. 2) Unlike the traditional solvation structure design, an efficient adsorptive additive strategy is proposed here to reshape the electric double layer and regulate Zn interfacial chemistry. 2-Hydroxy-4’-(2-hydroxyethoxy)-2-methylpropiophenone (Irgacure 2959) was selected owing to its strong adsorption ability, intermolecular hydrogen bonding and exposed strong electronegative carbonyl group. The constructed self-adaptive adlayer contributes to localized H2O, SO42--poor environment and horizontal alignment of Zn deposits along the (002) plane, thus endowing thermodynamically stable and highly reversible Zn electrochemistry. As a result, steady plating/stripping up to 3800 h and high coulombic efficiency of 99.8 % are achieved at 1 mA cm-2. Intriguingly for practical application, the economical additive (0.016 USD L-1) enables 330 h cycling life under 65% depth of discharge in Zn/Zn cells and stable discharge output for 500 cycles in Zn/VS2 cells at a low negative-to-positive capacity ratio of 2.5 (cathode mass loading: 10.8 mg cm-2), holding great promise in a scalable, low-cost, rechargeable battery. 3) Electrolyte additive, with convenient operation and remarkable functions, has been regarded as an effective strategy to prolong the cycle life of aqueous zinc ion batteries. However, it is still difficult to dynamically regulate the unstable Zn interface during long-term cycling. Herein, tricine was introduced as an efficient regulator to achieve the pH-stable and by-product-free interface. The functional zwitterion of tricine not only inhibits interfacial pH perturbation and parasitic reactions by the trapping effect of anionic group (-COO-), but also simultaneously uniformizes the electric field by the electrostatic shielding effect of cationic group (-NH2+). Such synergy accordingly eliminates the dendrite formation and creates a chemical equilibrium in the electrolyte, which endows the Zn||Zn symmetric cell with long-term Zn plating/stripping for 2060 h at 5 mA cm-2 and 720 h at 10 mA cm-2. As a result, the Zn||VS2 full cell under high cathodic loading mass (8.6 mg cm-2) exhibits exceptional capacity retention of 93% after 1000 cycles. 4) In addition to electrolyte optimization, surface modification is also an effective way to stabilize the anodic interface. Here, we proposed a modified Zn foil with a zincophilic ZnSe layer deposited by a simple selenization process. An order of magnitude stronger adsorption capability towards Zn2+ ions and uniform ion diffusion tunnels of ZnSe enables lower nucleation energy barrier and faster ion-diffusion kinetics. Meanwhile, detrimental Zn corrosion in aqueous system is also effectively mitigated. As a result, ZnSe@Zn anode shows reversible Zn plating/stripping (1700 h at 1 mA cm-2) with ultra-low voltage hysteresis (41 mV), contributing to exceptional cycling stability over 500 cycles with negligible capacity fading for the ZnSe@Zn/MnO2 full cell.