Achieving Highly Stable Zn Metal Anodes at Low Temperature via Regulating Electrolyte Solvation Structure.

Zinc metal is an attractive anode material for rechargeable aqueous Zn-ion batteries (ZIBs). However, the dendrite growth, water-induced parasitic reactions, and freezing problem of aqueous electrolyte at low temperatures are the major roadblocks that hinder the widely commercialization of ZIBs. Herein, tetrahydrofuran (THF) is proposed as the electrolyte additive to improve the reversibility and stability of Zn anode. Theoretical calculation and experimental results reveal that the introduction of THF into the aqueous electrolyte can optimize the solvation structure which can effectively alleviate the H2O-induced side reactions and protect the Zn anode from corrosion. Moreover, THF can act as a hydrogen bond acceptor to interact with H2O, which can greatly reduce the activity of free H2O in electrolytes and improve the low-temperature electrochemical performance of Zn anode. As a result, the Zn anodes demonstrate high cyclic stability for 2800 h at 27 °C and over 4000 h at -10 °C at 1.0 mA cm-2 /1.0 mAh cm-2. The full cell exhibits excellent cyclic stability and rate capability at 27 and -10 °C. This work is expected to provide a new approach to regulate the aqueous electrolyte and Zn anode interface chemistry for highly stable and reversible Zn anodes.

Polymer Molecules Adsorption-Induced Zincophilic-Hydrophobic Protective Layer Enables Highly Stable Zn Metal Anodes.

Zn metal, as one of the most promising anode materials for aqueous batteries, suffers from uncontrollable dendrite growth and water-induced parasitic reactions, which drastically compromise its cycle life and Coulombic efficiency (CE). Herein, a nonionic amphipathic additive Tween-20 (TW20) is proposed that bears both zincophilic and hydrophobic units. The zincophilic segment of TW20 preferentially adsorbs on the Zn anode, while the hydrophobic segment is exposed on the electrolyte side, forming an electrolyte-facing hydrophobic layer that shields the anode from active water molecules. Moreover, theoretical calculation and experimental results reveal that the TW20 additive can induce the preferential growth of (002) plane by adsorbing on other facets, enabling dendrite-free Zn anodes. Benefitting from these advantages, the stability and reversibility of Zn anodes are substantially improved, reflected by stable cycling for over 2500 h at 1.0 mA cm-2/1.0 mAh cm-2 and 500 h at 5 mA cm-2/5 mAh cm-2 as well as an average CE of 99.4% at 1.0 mA cm-2/1.0 mAh cm-2. The full cells paired with MnO2 demonstrate a long lifespan for more than 700 cycles at 500 mA g-1. This work is expected to provide a new approach to modulate Zn electrode interface chemistry for highly stable Zn anodes.

Manipulating OH- -Mediated Anode-Cathode Cross-Communication Toward Long-Life Aqueous Zinc-Vanadium Batteries.

The anode-cathode interplay is an important but rarely considered factor that initiates the degradation of aqueous zinc ion batteries (AZIBs). Herein, to address the limited cyclability issue of V-based AZIBs, Al2 (SO4 )3 is proposed as decent electrolyte additive to manipulate OH- -mediated cross-communication between Zn anode and NaV3 O8 ⋅ 1.5H2 O (NVO) cathode. The hydrolysis of Al3+ creates a pH≈0.9 strong acidic environment, which unexpectedly prolongs the anode lifespan from 200 to 1000 h. Such impressive improvement is assigned to the alleviation of interfacial OH- accumulation by Al3+ adsorption and solid electrolyte interphase formation. Accordingly, the strongly acidified electrolyte, associated with the sedated crossover of anodic OH- toward NVO, remarkably mitigate its undesired dissolution and phase transition. The interrupted OH- -mediated communication between the two electrodes endows Zn||NVO batteries with superb cycling stability, at both low and high scan rates.

Interfacial Protection Engineering of Sodium Nanoparticles toward Dendrite-Free and Long-Life Sodium Metal Battery.

The instability of interfacial solid-electrolyte interphase (SEI) layer of metallic sodium (Na) anode during cycles results in the rapid capacity decay of sodium metal batteries (SMBs). Herein, the concept of interfacial protection engineering of Na nanoparticles (Na-NPs) is proposed first to achieve stable, dendrite-free, and long-life SMB. Employing an ion-exchange strategy, conformal Sn-Na alloy-SEI on the interface of Na-NPs is constructed, forming Sn@Na-NPs. The stable alloy-based SEI layer possesses the following three advantages: 1) significantly enhancing the transport dynamics of Na+ ions and electrons; 2) enabling the well-distributed deposition of Na+ ions to avoid the growth of dendrites; and 3) protecting the Sn@Na-NPs anode from the attack of electrolyte, thereby reducing the parasitic reaction and boosting the Coulombic efficiency of SMBs. Because of these virtues, the symmetric Sn@Na-NPs cell shows an ultralow voltage hysteresis of 0.54 V at 10 mA cm-2 after 600 h. Paired with the Na3 V2 (PO4 )2 O2 F (NaVPF) cathode, the NaVPF-Sn@Na-NPs full cell exhibits an initial discharge capacity of 89.2 mAh g-1 at 1 C and a high capacity retention of 81.6% after 600 cycles.

Design Strategies of Si/C Composite Anode for Lithium-Ion Batteries.

Silicon-based materials that have higher theoretical specific capacity than other conventional anodes, such as carbon materials, Li2 TiO3 materials and Sn-based materials, become a hot topic in research of lithium-ion battery (LIB). However, the low conductivity and large volume expansion of silicon-based materials hinders the commercialization of silicon-based materials. Until recent years, these issues are alleviated by the combination of carbon-based materials. In this review, the preparation of Si/C materials by different synthetic methods in the past decade is reviewed along with their respective advantages and disadvantages. In addition, Si/C materials formed by silicon and different carbon-based materials is summarized, where the influences of carbons on the electrochemical performance of silicon are emphasized. Lastly, future research direction in the material design and optimization of Si/C materials is proposed to fill the current gap in the development of efficient Si/C anode for LIBs.

Bi2S3/C nanorods as efficient anode materials for lithium-ion batteries.

Bi2S3 is a promising negative electrode material for lithium storage owing to its high theoretical capacity. Nevertheless, the capacity of Bi2S3 decays very rapidly upon Li cycling. Here, Bi2S3 and Bi2S3/C were successfully synthesized by a novel route. Sulfur powder as a kind of sulfur source reacted with a metal organic framework based on bismuth and trimesinic acid-Bi(BTC)(DMF)·DMF·(CH3OH)2 (denoted as Bi-BTC). Trimesic acid further acted as a new type of carbon source to synthesize the Bi2S3/C composite. The particle sizes of the composite were smaller than those of pure Bi2S3, showing the suppression of Bi2S3 aggregation. Charge-discharge performance and cyclability for both the Bi2S3 and Bi2S3/C composites in lithium-ion batteries were measured. Specifically, the specific capacities of Bi2S3/C and Bi2S3 reached 765 and 603 mA h g-1, respectively, at 100 mA g-1 after 100 cycles. Because of its high capacity and excellent cycle life, Bi2S3/C is a promising energy storage material.