Organic Cations Texture Zinc Metal Anodes for Deep Cycling Aqueous Zinc Batteries

Reconfiguring solvation network and interfacial engineering of Zn metal anode with biomass carbon quantum dot

The implementation of aqueous zinc-ion batteries (AZIBs) in energy storage systems has uneven Zn dendrites and side reactions seriously at the zinc anode and electrolyte interface. A novel green biomass carbon quantum dot (BCDs) additive influenced the hydrogen bonding network of the electrolyte, reduced water activity, and suppressed hydrogen evolution corrosion of the zinc anode. At the same time, we proposed a buffer redistribution effect that BCDs can act as the support of SO42-, and the linkage mechanism can further prolong the residence time of Zn2+ on SO42--BCDs. This effectively allows more time for the adsorbed Zn2+ to migrate to the most stable position on Zn (0 0 2) and form a perfect pattern, it regulated the Zn2+ solvation network and interfacial chemistry of zinc anodes. In addition, the Zn||Zn-symmetric battery with a current density of 1 mA cm-2/1 mAh cm-2 can cycling 3450 h. And the constructed full Zn||PANI full battery can be stably cycled 5000 cycles at a current density of 0.5 and 5 A g-1. This study reveals the principle of maximizing zinc utilization solvate structural interface design, and highlights the commercial potential of BCDs additives in the design for efficient and durable AZIBs.

Coupling Zn2+ Ferrying Effect With Anion-π Interaction to Mitigate Space Charge Layer Enables Ultra-High Utilization Rate Zn Anode

A major dilemma faced by Zn anodes at a high zinc utilization rate (ZUR) is the insufficient supply of ionic carriers that initiate the space charge layer (SCL) subject to the rampant growth of Zn dendrites. Herein, an "anion-cation co-regulation" strategy, associated with a fundamental principle for screening potential electrolyte additives coupling the Zn2+ ferrying effect with anion-retention capability, is put forward to construct dendrite-free, high-ZUR Zn anode. Taking ninhydrin-modified ZnSO4 system as a proof-of-concept, the multiple zincophilic polar groups of ninhydrin facilitate the transport of Zn2+ ions, while its electron-deficient aromatic ring retains SO4 2- counterions via anion-π interaction, constructing an ion-rich interface that minimizes the SCL-driven Zn deterioration. Consequently, the Zn anode can endure ∼240 h continuous cycling at an ultrahigh ZUR of 87.3%. The superiority brought by ninhydrin is further reflected by the ultralong cycling durability of Zn-I2 batteries (over 100 000 cycles). Even at an ultralow N/P ratio of 1.1 (∼90.6% ZUR), the battery with a capacity of ∼5.27 mAh cm-2 can still sustain for 350 cycles, which has been hardly achieved in aqueous Zn batteries. Furthermore, the effectiveness of this strategy is fully validated by a series of additives sharing similar fundamentals.

Zinc-Ion Conductive Metal-Organic Framework Interfaces for Comprehensive Anode Protection in High-Performance Aqueous Zinc-Ion Batteries

Aqueous zinc-ion batteries have attracted intensive attention because of their safety, low cost, and high theoretical capacity; however, their practical application is hindered by challenges, such as Zn dendrite formation, the hydrogen evolution reaction, and a limited cycle life. Herein, a zinc anode interface is prepared by combining sodium alginate (SA) with hydroxyl and carboxyl groups as a binder and zeolite imidazole framework (ZIF-7) as the ion transport channel. The carboxyl groups in SA exhibit strong Zn2+-ion affinity, forming a cross-linked structure with ZIF-7 and creating a self-reinforcing coating that promotes uniform Zn2+ ion flux while the ZIF-7 provides suitable ionic channels to enable oriented deposition. A ZIF-7/SA coated Zn anode (ZIF-7/SA@Zn) exhibited a high Coulombic efficiency of 99.7% after 1500 cycles at 10 mA cm-2 and 1 mA h cm-2. Even under high-current and high-capacity conditions (20 mA cm-2, 20 mA h cm-2), ZIF-7/SA@Zn maintained stable cycling for 500 h. When ZIF-7/SA@Zn was paired with a Zn0.25V2O5 cathode, the resultant full cell retained more than 77.2% of its capacity after 10,000 cycles at 3000 mA g-1. This work proposes a strategy to stabilize Zn anodes under high currents, advancing high-performance Zn-based energy storage systems.

Breaking Performance Limits of Zn Anodes in Aqueous Batteries by Tailoring Anion and Cation Additives

Crystallographic engineering of Zn anodes to favor the exposure of (002) planes is an effective approach for improving stability in aqueous electrolytes. However, achieving non-epitaxial electrodeposition with a pronounced (002) texture and maintaining this orientation during extended cycling remains challenging. This study questions the prevailing notion that a single (002)-textured Zn anode inherently ensures superior stability, showing that such anodes cannot sustain their texture in ZnSO4 electrolytes. We then introduced a novel electrolyte additive, benzyltriethylammonium chloride (TEBAC), which preserves the (002) texture over prolonged cycling. Furthermore, we successfully converted commercial Zn foils into highly crystalline (002)-textured Zn without any pretreatment. Experiments and theoretical calculations revealed that the cationic TEBA+ selectively adsorbs onto the anode surface, promoting the exposure of the Zn(002) plane and suppressing dendrite formation. A critical discovery was the pitting corrosion caused by chloride ions from TEBAC, which we mitigated by anion substitution. This modification leads to a remarkable lifespan of 375 days for the Zn||Zn symmetric cells at 1 mA cm-2 and 1 mAh cm-2. Furthermore, a TEBA+-modified Zn||VO2 full cell demonstrates high specific capacity and robust cycle stability at 10.0 A g-1. These results provide valuable insights and strategies for developing long-life Zn ion batteries.

Enabling Targeted Zinc Growth via Interface Regulation Toward Binder Free and High Areal Capacity Zinc Metal Anode

Owing to the low redox potential, abundant nature, and widespread availability, aqueous zinc-ion batteries (AZIBs) have attracted extensive investigation. Nevertheless, the commercialization of the batteries is severely hindered by negative side reactions, catastrophic dendrite growth, and uneven Zn2+ diffusion. Here, 3D self-assembled necklace-like nanofibers are developed by a simple electrospinning technique, in which SiO2@SiO2/C nanospheres are sequentially aligned on interconnected nitrogen/carbon networks (SSA/NCF) to achieve binder-free, high-performance, and dendrite-free growth of APLs. The design structure combines excellent interfacial ion transfer, corrosion resistance, and unique planar deposition regulation. The protective layer of SSA/NCF paper exhibits a high affinity for Zn2+, thereby reducing the nucleation barrier of Zn2+ and ensuring a more homogeneous Zn deposit. More importantly, this multifunctional interfacial layer induces preferential crystalline (101) oriented electroplating growth and promotes oriented dense Zn deposition. Consequently, the SSA/NCF paper layer endowed the cell with remarkable cycling stability, achieving an extended cycle life of 3000 h at 5 mA cm-2/1.25 mAh cm-2. This study offers novel insights into the development of high-performance zinc anodes.

Insights into the enhanced electrochemical performance and energy storage mechanism of a manganese vanadate cathode for rechargeable aqueous zinc ion batteries

An N-doped reduced graphene oxide sheet wrapped MnV2O6 nanrod composite was designed and prepared by a co-precipitation reaction and subsequent calcination method, which delivered stable reversible capacity, low charge transfer resistance and high diffusion coefficients during the Zn2+ insertion and extraction processes.

Weak Dipole Effect Customized Zinc Ion-Rich Protective Layer for Lean-Electrolyte Zinc Metal Batteries

The industrial development of Zn-ion batteries requires high performance even with lean-electrolyte. Nevertheless, lean-electrolyte can exacerbate concentration polarization at the interface of electrode/electrolyte, leading to significant Zn corrosion and battery failure. Here, a stable Zn ion-rich protective layer (TMAO-Zn) is constructed by a unique zwitterion structure of trimethylamine N-oxide (TMAO). The TMAO is characterized by the direct connection between positive and negative charges (N+-O-) with minimal dipole moment, which renders weak dipole interactions to form the TMAO-Zn layer with Zn2+, thereby reducing concentration polarization and promoting the rapid and uniform deposition of Zn2+. Furthermore, the O of TMAO-Zn exhibits the higher electrophilic index, indicating a stronger propensity for stable hydrogen bond interactions with active free water in the inner Helmholtz layer (IHL), thereby mitigating corrosion under extreme conditions of low electrolyte-to-capacity ratio (E/C ratio). Consequently, the symmetrical Zn battery with TMAO-Zn enables stable cycling for over 250 h with lean-electrolyte of 15 µL mA h-1. Additionally, Zn/I₂ pouch battery with a low E/C ratio of 21.2 µL mA h-1 provides ultra-high stable specific capacity of 96 mA h for over 250 cycles (capacity retention rate of 98.3%). This study offers a new concept to propel the practical application of Zn batteries with lean-electrolyte.

Hydrogel Electrolytes-Based Rechargeable Zinc-Ion Batteries under Harsh Conditions

Rechargeable zinc (Zn)-ion batteries (RZIBs) with hydrogel electrolytes (HEs) have gained significant attention in the last decade owing to their high safety, low cost, sufficient material abundance, and superb environmental friendliness, which is extremely important for wearable energy storage applications. Given that HEs play a critical role in building flexible RZIBs, it is urgent to summarize the recent advances in this field and elucidate the design principles of HEs for practical applications. This review systematically presents the development history, recent advances in the material fundamentals, functional designs, challenges, and prospects of the HEs-based RZIBs. Firstly, the fundamentals, species, and flexible mechanisms of HEs are discussed, along with their compatibility with Zn anodes and various cathodes. Then, the functional designs of hydrogel electrolytes in harsh conditions are comprehensively discussed, including high/low/wide-temperature windows, mechanical deformations (e.g., bending, twisting, and straining), and damages (e.g., cutting, burning, and soaking). Finally, the remaining challenges and future perspectives for advancing HEs-based RZIBs are outlined.

A two-dimensional amorphous VOPO4/graphene heterostructure for high-voltage aqueous Zn-ion batteries

A novel two-dimensional (2D) amorphous VOPO4/graphene (A-VOP/G) heterostructure, which features rapid ion diffusion pathways, numerous active sites, high conductivity, and superior stability, serves as a high-voltage cathode for zinc-ion batteries (ZIBs). The A-VOP/G cathode achieves a high-voltage platform (1.50 V) and is stable over 2000 cycles at 5 A g-1.

Single (002)-Textured Zinc Anode via Nonepitaxial Electrodeposition with In Situ Texture Maintenance for Stable Aqueous Zinc Batteries

Crystallography regulation of a zinc (Zn) metal substrate to expose more (002) textures holds great promise for stabilizing Zn anodes. However, significant challenges remain in directly constructing a single (002)-plane-textured Zn metal anode (S-(002)-Zn) and realizing a sustainable (002)-texture exposure in working batteries. Herein, we report an anion and cation coregulated nonepitaxial electrodeposition to fabricate S-(002)-Zn by introducing 1-ethyl-3-methylimidazolium iodide (EmimI) additives in low-cost ZnSO4 aqueous electrolyte (ZS). Mechanistic studies reveal that the cooperation of Emim+ and I- with oriented adsorption behaviors on Zn can synergistically boost the (100) plane growth, depress the (002) plane growth, and suppress H2 evolution, thus enabling compact S-(002)-Zn electrodeposition. Moreover, other similar organic iodides (e.g., dimethyl-imidazolium iodide and 1-propyl-3-methylimidazolium iodide) are applicable to this scalable electrodeposition. On the other hand, the as-designed ZS-EmimI electrolyte can be directly applied in working Zn batteries, thus effectively sustaining the smooth (002) texture of S-(002)-Zn and inhibiting HER during cycling. Consequently, the combination of single-(002)-texture and ZS-EmimI electrolyte endows the S-(002)-Zn anode with an ultralong lifespan over 10,100 h (>14 months) at 1 mAh cm-2 and superior deep-cycling stability under 88.0% utilization (25 mAh cm-2) over 500 h and assures the stable operation of full Zn batteries.

Salt-Based Electrolyte Additives for Regulating the Interface Chemistry of Zinc Metal Anodes in High-Performance Aqueous Zinc Batteries

Aqueous zinc-metal batteries (AZMBs) are emerging as a promising green and low-cost energy storage solution, distinguished by their high safety and environmental friendliness. However, the industrialization of AZMBs is currently hindered by significant challenges, particularly uncontrollable dendritic growth and side reactions at the zinc metal anode interface, which severely limit their large-scale application. To address these issues, salt-based electrolyte additives have emerged as a straightforward, economical, and practical solution. This review systematically classifies and analyzes the working mechanisms of inorganic, organic, and ammonium salt-based additives, elucidating their roles in regulating solvation structures, hydrogen bond networks, pH levels, interfacial protective layers, electric fields, and Zn2+ deposition behaviors. These additives enhance anode stability and mitigate side reactions, thereby improving overall electrochemical performance. Additionally, the review offers valuable insights into future directions for the development of salt-based electrolyte additives, providing essential guidance for advancing research in this field.

Tailoring Crystalline States of Alloy Coating for High Current Density and Large Areal Capacity of Zn

Due to issues of hydrogen evolution, corrosion, and uncontrolled deposition behaviors at the Zn anode, the practical implementation of Zn-ion batteries has faced significant obstacles. Very limited attention is directed toward various alloy crystalline states for the Zn anode protection primarily due to the challenge of synthesizing high-quality alloy coatings with diverse crystalline states. In this study, the crystalline state of NiCr alloy coating is precisely manipulated using magnetron sputtering, revealing distinct thermodynamic and kinetic changes induced by variation in the crystalline state. This research emphasizes the fundamental understanding of microstructure dynamics and achieves a highly reversible Zn anode at harsh conditions of high current density (80 mA cm-2) and large areal capacity (40 mAh cm-2), thus enabling high-capacity and longevous pouch battery.

Zn2+ flux regulator to modulate the interface chemistry toward highly reversible Zn anode

The persistent challenges of diminished coulombic efficiency (CE) and the formation of Zn dendrites at the Zn anode interface substantially hinder the cycle life of aqueous Zn-ion batteries (AZIBs), thereby impeding their widespread deployment. To address these issues, multifunctional 2-amino-5-guanidino-pentanoic acid (AGPA) additive is introduced into the electrolyte, as a novel Zn2+ flux regulator (ZFR) to improve the reversibility and durability of Zn anodes. The distinctive zincophilicity of amino groups empowers such ZFR with a higher adsorption energy, enabling the construction of a multifunctional molecular adsorption layer on Zn electrode surface. Simultaneously, leveraging the exceptional nucleophilic characteristics of polar carboxyl groups, AGPA molecules tend to form chelating bonds with Zn2+ for manipulating the interface chemistry and solvation chemistry. The functional groups in ZFR work in synergy to attract zinc ions for homogenizing Zn2+ flux and suppress the interfacial side reactions, resulting in uniform dendrite-free Zn deposition. Consequently, the Zn//Zn symmetrical cell achieves an extended cycle life of 5500 h. Moreover, the ZFR enables stable operation of the full batteries with an ultra-long cycling lifespan of 6000 cycles at 5 A/g, showcasing the effectiveness of ZFR in advancing the commercialization of AZIBs.

Metallic vanadium activated by an in situ dissolution-deposition process for a superior aqueous zinc ion battery cathode

Metallic vanadium is innovatively introduced for a superior aqueous zinc-ion battery cathode material, which is activated through in situ dissolution-deposition transition to amorphous V2O5·3H2O and delivers an excellent capacity of 610 mA h g-1 at 0.1 A g-1 and remarkable capacity retention rate of 80.3% after 1000 cycles at 1 A g-1.

Stress Release of Zincophilic N-Doped Carbon@Sn Composite on High-Curvature Surface of Zinc Foam for Dendrite-Free 3D Zinc Anode

Commercial 3D zinc foam anodes with high deposition space and ion permeation have shown great potential in aqueous ion batteries. However, the local accumulated stress from its high-curvature surface exacerbates the Zn dendrite issue, leading to poor reversibility. Herein, we have employed zincophilic N-doped carbon@Sn composites (N-C@Sn) as nano-fillings to effectively release the local stress of high curvature surface of 3D Zn foams toward dendrite-free anode in aqueous zinc ion battery (AZIB). These electronegative and conductive N-C@Sn nano-fillings as supporters can provide a highly zincophilic channel for initial Zn nucleation and reduce local current density for regulating Zn deposition. Uniform Zn deposition further assists homogenous stress distribution on the platting surface, which gives a positive feedback loop to improve anode reversibility. As a result, zinc foam with N-C@Sn composite (ZCSn Foam) symmetric cell achieves a long cycle lifespan of 1100h at 0.5 mA cm-2, much more than that of Zn Foam (∼80 h lifespan). The full cell ZCSn Foam||MnO2 exhibits remarkable reversibility with 67% retention after 1000 cycles at 0.8 A g-1 and 76% after 1600 cycles at 2 Ag-1. This 3D-constructing strategy may offer a promising and practical pathway for metal anode application.

Customizing H2O-Poor Electric Double Layer and Boosting Texture Exposure of Zn (101) Plane towards Super-High Areal Capacity Zinc Metal Batteries

The catastrophic dendrite hyperplasia and parasitic reactions severely impede the future deployment of aqueous Zn-ion batteries. Controlling zinc orientation growth is considered to be an effective method to overcome the aforementioned concerns, especially for regulating the (002) plane of deposited Zn. Unfortunately, Zn (002) texture is difficult to obtain stable cycling under high deposition capacity resulting from its large lattice distortion and nonuniform distribution in electric field. Herein, different from traditional cognition, a crystallization orientation regulation tactic is proposed to boost Zn (101) texture exposure and inhibit zinc dendrite proliferation during plating/stripping. Experimental results and theoretical calculations demonstrate the malate molecules preferentially adsorb on the Zn (002) facet, leading to the texture exposure of distinctive Zn (101) plane. Meanwhile, the -COOH and -OH groups of malate molecules exhibit strong adsorption on the Zn anode surface and chelate with Zn2+, achieving H2O-poor electrical double layer. Very impressively, the multifunctional malate additive enlists zinc anode to survive for 600 h under a harsh condition of 15 mA cm-2/15 mAh cm-2. Moreover, the symmetric cell harvests highly-reversible cycling life of 6600 h at 5 mA cm-2/1.25 mAh cm-2, remarkably outperforming the ZnSO4 electrolyte. The assembled Zn//MnO2 full cells also demonstrate prominent electrochemical reversibility.

Synergistic Cationic Shielding and Anionic Chemistry of Potassium Hydrogen Phthalate for Ultrastable Zn─I2 Full Batteries

Electrolyte additives are investigated to resolve dendrite growth, hydrogen evolution reaction, and corrosion of Zn metal. In particular, the electrostatic shielding cationic strategy is considered an effective method to regulate deposition morphology. However, it is very difficult for such a simple cationic modification to avoid competitive hydrogen evolution reactions, corrosion, and interfacial pH fluctuations. Herein, multifunctional additives of potassium hydrogen phthalate (KHP) based on the synergistic design of cationic shielding and anionic chemistry for ultrastable Zn||I2 full batteries are demonstrated. K cations, acting as electrostatic shielding cations, constructed the smooth deposition morphology. HP anions can enter the first solvation shell of Zn2+ for the reduced activities of H2O, while they remain in the primary solvation shell and are finally involved in the formation of SEI, thus accelerating the charge transfer kinetics. Furthermore, by in situ monitoring the near-surface pH of the Zn electrode, the KHP additives can effectively inhibit the accumulation of OH- and the formation of by-products. Consequently, the symmetric cells achieve a high stripping-plating reversibility of over 4500 and 2600 h at 1.0 and 5 mA cm-2, respectively. The Zn||I2 full cells deliver an ultralong term stability of over 1400 cycles with a high-capacity retention of 78.5%.

The ZnO-SiO2 Composite Phase with Dual Regulation Function Enables Uniform Zn2+ Flux and Fast Zinc Deposition Kinetics Toward Zinc Metal Batteries

As an important candidate for rechargeable energy storage devices, the large-scale development of aqueous zinc ion batteries has been hindered by hydrogen evolution and uncontrollable dendrites of metal anodes. A novel ZnO-SiO2 composite interface phase (Zn@ZSCP) with a double protective effect based on in situ synthesis by hydrothermal method is used to improve these difficulties. The hydrophilic SiO2 layer is beneficial to the dissolution of hydrated zinc ions and reduces the nucleation barrier during zinc deposition, while the stable ZnO layer helps to adjust the electric field distribution on the surface of the metal anode to further induce uniform zinc nucleation. The cycle life of the Zn@ZSCP||Zn@ZSCP symmetric battery based on this innovative interface phase modification is up to 2500 h. Even at a high current density of 8 mA cm-2, the symmetric battery still has a stable cycle life of more than 2000 h. The zinc-iodine full battery based on Zn@ZSCP anode and low-cost biomass-derived porous carbon exhibits an excellent specific capacity and outstanding cycle stability. This simple and reasonable battery structure design not only improves the practicability of aqueous zinc ion batteries to a certain extent but also helps to develop more efficient and environmentally friendly zinc metal batteries.

Screening Ammonium-Based Cationic Additives to Regulate Interfacial Chemistry for Aqueous Ultra-Stable Zn Metal Anode

The interfacial dynamics and chemistry at the electrolyte/metal interface, particularly the formation of an adsorption interphase, is paramount in dictating the reversibility of Zn metal deposition and dissolution processes in battery systems. Herein, a series of different cationic ammonium-based electrolyte additives are screened that effectively modulate the interfacial chemistry of zinc anodes in aqueous electrolytes, significantly improving the reversibility of Zn metal plating/stripping processes. As initially comprehensive investigation by combining theoretical calculation and molecular dynamic simulation, the tetramethylammonium cation, with its specific molecular structure and charge distribution, is identified as pivotal in mediating the Zn(H2O)6 2+ solvation shell structure at the electrode/electrolyte interface and shows the strong resistance against electrolyte corrosion as revealed by X-ray and optical measurements. As a result, the Zn||Zn symmetric cell with optimal electrolyte lasts for over 4400 h of stable plating/stripping behaviors, and the Zn||Cu asymmetric cell stabilizes for 2100 cycles with an average Coulombic efficiency of 99.8%, which is much better than the-state-of-art progress. Consequently, full-cells coupled with various cathodes showcase improved electrochemical performance, displaying high capacity-retention and low self-discharge behaviors. These findings offer essential insights of cationic additives in ameliorating zinc anode performance.