Hetero Nucleus Growth Stabilizing Zinc Anode for High-Biosecurity Zinc-Ion Batteries

Exploring role of microbatteries in enhancing sustainability and functionality of implantable biosensors and bioelectronics

Microbatteries are emerging as a sustainable, miniaturized power source, crucial for implantable biomedical devices. Their significance lies in offering high energy density, longevity, and rechargeability, facilitating uninterrupted health monitoring and treatment within the body. The review delves into the development of microbatteries, emphasizing their miniaturization and biocompatibility, crucial for long-term, safe in-vivo use. It examines cutting-edge manufacturing techniques like physical and chemical vapor deposition, and atomic layer deposition, essential for the precision manufacture of the microbatteries. The paper contrasts primary and secondary batteries, highlighting the advantages of zinc-ion and magnesium-ion batteries for enhanced stability and reduced reactivity. It also explores biodegradable batteries, potentially obviating the need for surgical extraction post-use. The integration of microbatteries into diagnostic and therapeutic devices is also discussed, illustrating how they enhance the efficacy and sustainability of implantable biosensors and bioelectronics.

Modulating solvated structure of Zn2+ and inducing surface crystallography by a simple organic molecule with abundant polar functional groups to synergistically stabilize zinc metal anodes for long-life aqueous zinc-ion batteries

Aqueous zinc-ion batteries (AZIBs) have attracted significant attention owing to their inherent security, low cost, abundant zinc (Zn) resources and high energy density. Nevertheless, the growth of zinc dendrites and side reactions on the surface of Zn anodes during repeatedly plating/stripping shorten the cycle life of AZIBs. Herein, a simple organic molecule with abundant polar functional groups, 2,2,2-trifluoroether formate (TF), has been proposed as a high-efficient additive in the ZnSO4 electrolyte to suppress the growth of Zn dendrites and side reaction during cycling. It is found that TF molecules can infiltrate the solvated sheath layer of the hydrated Zn2+ to reduce the number of highly chemically active H2O molecules owing to their strong binding energy with Zn2+. Simultaneously, TF molecules can preferentially adsorb onto the Zn surface, guiding the uniform deposition of Zn2+ along the crystalline surface of Zn(002). This dual action significantly inhibits the formation of Zn dendrites and side reactions, thus greatly extending the cycling life of the batteries. Accordingly, the Zn//Cu asymmetric cell with 2 % TF exhibits stable cycling for more than 3,800 cycles, achieving an excellent average Columbic efficiency (CE) of 99.81 % at 2 mA cm-2/1 mAh cm-2. Meanwhile, the Zn||Zn symmetric cell with 2 % TF demonstrates a superlong cycle life exceeding 3,800 h and 2,400 h at 2 mA cm-2/1 mAh cm-2 and 5 mA cm-2/2.5 mAh cm-2, respectively. Simultaneously, the Zn//VO2 full cell with 2 % TF possesses high initial capacity (276.8 mAh/g) and capacity retention (72.5 %) at 5 A/g after 500 cycles. This investigation provides new insights into stabilizing Zn metal anodes for AZIBs through the co-regulation of Zn2+ solvated structure and surface crystallography.

Sustainable Electrolytes: Design Principles and Recent Advances

Today, rechargeable batteries are omnipresent and essential for our existence. In order to improve the electrochemical performance of electric fields, the introduction of electrolytes with fluorine (F)-based inorganic elemental compositions is a direction of exploration. However, most fluorocarbons have a high global warming potential and ozone depletion potential, which do not meet the sustainability requirements of the battery industry. Therefore, developing sustainable electrolytes is a viable option for future battery development. Although researchers have made much progress in electrolyte optimization, little attention has been paid to developing low-toxic and safe electrolytes. This review aims to elucidate the design principles and recent advances in this direction for solvents and salts. It concludes with a summary and outlook on future research directions for the molecular design of green electrolytes for practical high-voltage rechargeable batteries.

Interfacial Biomacromolecular Engineering Toward Stable Ah-Level Aqueous Zinc Batteries

Interfacial instability within aqueous zinc batteries (AZBs) spurs technical obstacles including parasitic side reactions and dendrite failure to reach the practical application standards. Here, an interfacial engineering is showcased by employing a bio- derived zincophilic macromolecule as the electrolyte additive (0.037 wt%), which features a long-chain configuration with laterally distributed hydroxyl and sulfate anion groups, and has the propensity to remodel the electric double layer of Zn anodes. Tailored Zn2+-rich compact layer is the result of their adaptive adsorption that effectively homogenizes the interfacial concentration field, while enabling a hybrid nucleation and growth mode characterized as nuclei-rich and space-confined dense plating. Further resonated with curbed corrosion and by-products, a dendrite-free deposition morphology is achieved. Consequently, the macromolecule-modified zinc anode delivers over 1250 times of reversible plating/stripping at a practical area capacity of 5 mAh cm-2, as well as a high zinc utilization rate of 85%. The Zn//NH4V4O10 pouch cell with the maximum capacity of 1.02 Ah can be steadily operated at 71.4 mA g-1 (0.25 C) with 98.7% capacity retained after 50 cycles, which demonstrates the scale-up capability and highlights a "low input and high return" interfacial strategy toward practical AZBs.

Boosting the reversibility of Zn anodes via synergistic cation-anion interface adsorption with addition of multifunctional potassium polyacrylate

Rechargeable aqueous Zn batteries have the edge in resource reserve, cost, energy and conversion efficiency due to the inherent features of metal Zn anodes. However, the application of Zn-based batteries is being seriously hindered by Zn dendrites and water-induced side-reactions. Here, potassium polyacrylate (K-PAM) is proposed as the electrolyte additive to form a synergistic cation-anion interface on Zn surface. The carboxyl anions and K+ cations are preferentially adsorbed on the Zn surface due to the intrinsic surfactant characteristics, which could homogenize Zn plating and suppress parasitic reactions. The synergistic regulation of K-PAM additive endows the ZnZn symmetric cells with excellent cyclic durability of 1250 h at 1 mA cm-2, which is significantly better than the polyacrylic acid additive only with carboxyl anions. Moreover, trace K-PAM addition into traditional ZnSO4 electrolyte endows the ZnCu batteries with a considerable average Coulombic efficiency of 99.2 %. Additionally, higher capacity retention and excellent cycling stability of ZnVO2 cells further mark K-PAM as a potentially impressive aqueous electrolyte additive for high-performance Zn-based batteries. This work will provide a promising method for the synergistic regulation with cations and anions of electrolyte additives to improve the stability and reversibility of Zn anodes.

Hydrophobic Two-Dimensional Layered Superstructure of a Polyoxometalate Cluster as the Cathode Material for Aqueous Zinc-Ion Batteries

Aqueous zinc-ion batteries hold promise for sustainable energy storage, yet challenges in finding high-performance cathode materials persist. Polyoxovanadates (POVs) are emerging as potential candidates due to their structural diversity and robust redox activity. Despite their potential, issues like dissolution in electrolytes, structural degradation, and byproduct accumulation persist. This work introduces a POV-based hydrophobic two-dimensional (2D) layered superstructure that addresses these challenges. The hydrophobic nature minimizes POV dissolution, enhancing structural stability and inhibiting phase transitions during cycling. The 2D arrangement ensures a larger surface area and improved electronic conductivity, resulting in faster kinetics and higher specific capacity. The superstructure demonstrates improved cycle life and an increased operating voltage, marking a significant advancement in POV-based cathode materials for aqueous zinc-ion batteries.

Zigzag Hopping Site Embedded Covalent Organic Frameworks Coating for Zn Anode

Precise design and tuning of Zn hopping/transfer sites with deeper understanding of the dendrite-formation mechanism is vital in artificial anode protective coating for aqueous Zn-ion batteries (AZIBs). Here, we probe into the role of anode-coating interfaces by designing a series of anhydride-based covalent organic frameworks (i.e., PI-DP-COF and PI-DT-COF) with specifically designed zigzag hopping sites and zincophilic anhydride groups that can serve as desired platforms to investigate the related Zn2+ hopping/transfer behaviours as well as the interfacial interaction. Combining theoretical calculations with experiments, the ABC stacking models of these COFs endow the structures with specific zigzag sites along the 1D channel that can accelerate Zn2+ transfer kinetics, lower surface-energy, homogenize ion-distribution or electric-filed. Attributed to these superiorities, thus-obtained optimal PI-DT-COF cells offer excellent cycling lifespan in both symmetric-cell (2000 cycles at 60 mA cm-2) and full-cell (1600 cycles at 2 A g-1), outperforming almost all the reported porous crystalline materials.

Unique solvation structure induced by anionic Cl in aqueous zinc ion batteries

Aqueous zinc ion batteries (AZIBs) have garnered significant attention in large-scale static energy storage battery systems due to their low cost, high safety and environmental friendliness. However, it has some inherent problems during operation, such as the occurrence of side reactions (hydrogen evolution reaction, HER) and anode corrosion, formation of by-products and growth of metal dendrites. To analyze the mechanism of generation from aspect of the electrolyte solvation structure and make cell efficiency further improvements based on it, so we use DFT calculations to find the most stable solvation structure in AZIBs with ZnCl2 as the electrolyte and analyze it. We define the relative concentration C r , and calculate different groups metal cation cluster structures such as [ Zn ( H 2 O ) n ] 2 + , [ ZnCl ( H 2 O ) n ] + , [ ZnCl 2 ( H 2 O ) n ] and [ ZnCl 3 ( H 2 O ) n ] - that exist at different C r . We discuss the effect of different clusters formed due to the C r variations on the battery performance in terms of three aspects: the structural conformation, the cluster characteristics (including the hydrogen bonding network, bond lengths, bond angles, as well as the electrostatic potential ESP) and the cluster performance (including the adsorption energy Ea, binding energy Eb, and desolvation energy Edes). The results shows that the electrolyte metal cation Zn2+ can be coordinated with up to six H2O molecules in first shell, and this metal cation solvation structure contributes to the occurrence and formation of side reactions and by-products, which reduces the battery efficiency. Increasing the electrolyte anion Cl- concentration by appropriately increasing the C r helps to desolvate the metal cation cluster structure, which greatly improves the battery efficiency and suppresses the side reactions and by-products. Yet the improvement effect was not obviously further improved by further increasing the Cl- concentration.

Unveiling Organic Electrode Materials in Aqueous Zinc-Ion Batteries: From Structural Design to Electrochemical Performance

Aqueous zinc-ion batteries (AZIBs) are one of the most compelling alternatives of lithium-ion batteries due to their inherent safety and economics viability. In response to the growing demand for green and sustainable energy storage solutions, organic electrodes with the scalability from inexpensive starting materials and potential for biodegradation after use have become a prominent choice for AZIBs. Despite gratifying progresses of organic molecules with electrochemical performance in AZIBs, the research is still in infancy and hampered by certain issues due to the underlying complex electrochemistry. Strategies for designing organic electrode materials for AZIBs with high specific capacity and long cycling life are discussed in detail in this review. Specifically, we put emphasis on the unique electrochemistry of different redox-active structures to provide in-depth understanding of their working mechanisms. In addition, we highlight the importance of molecular size/dimension regarding their profound impact on electrochemical performances. Finally, challenges and perspectives are discussed from the developing point of view for future AZIBs. We hope to provide a valuable evaluation on organic electrode materials for AZIBs in our context and give inspiration for the rational design of high-performance AZIBs.

Constructing Highly Stable Zinc Metal Anodes via Induced Zn(002) Growth

The nonuniform electric field at the surface of a zinc (Zn) anode, coupled with water-induced parasitic reactions, exacerbates the growth of Zn dendrites, presenting a significant impediment to large-scale energy storage in aqueous Zn-ion batteries. One of the most convenient strategies for mitigating dendrite-related issues involves controlling crystal growth through electrolyte additives. Herein, we present thiamine hydrochloride (THC) as an electrolyte additive capable of effectively stabilizing the preferential deposition of the Zn(002) plane. First-principles calculations reveal that THC tends to adsorb on Zn(100) and Zn(101) planes and is capable of inducing the deposition of Zn ion onto the (002) plane and the preferential growth of the (002) plane, resulting in a flat and compact deposition layer. A THC additive not only effectively suppresses dendrite growth but also prevents the generation of side reactions and hydrogen evolution reaction. Consequently, the Zn||Zn symmetric battery exhibits long-term cycling stability of over 3000 h at 1 mA cm-2/1 mAh cm-2 and 1000 h at 10 mA cm-2/10 mAh cm-2. Furthermore, the NH4V4O10||Zn full battery also displays excellent cycling stability and a high reversible capacity of 210 mAh g-1 after 1000 cycles at 1 A g-1, highlighting a significant potential for practical applications.

A zincophilic separator with directional alignment and pore hydrophilicity towards stable aqueous zinc metal batteries

A zincophilic PAN@Zn(OTF)2 (PZO) separator with an extremely thin thickness of 65.6 μm is introduced. This separator with a low cost of 6.1 $ m-2, exhibiting excellent mechanical and wettability properties. The cell with the PZO separator exhibits impressive electrochemical performances both in symmetrical Zn||Zn cell and Zn||NVO full cell.

Sulfur-Defect-Induced TiS1.94 as a High-Capacity and Long-Life Anode Material for Zinc-Ion Batteries

Aqueous zinc-ion batteries (ZIBs) are competitive among the elective candidates for electrochemical energy storage systems, but the intrinsic drawbacks of zinc metal anodes such as dendrites and corrosion severely hinder their large-scale application. Developing alternative anode materials capable of high reversibility and stability for storing Zn2+ ions is a feasible approach to circumvent the challenge. Herein, a sulfur-defect-induced TiS1.94 (D-TiS1.94) as a promising intercalation anode material for ZIBs is designed. The abundant Zn2+-storage active sites and lower Zn2+ migration barrier induced by sulfur defects endow D-TiS1.94 with a high capacity for Zn2+-storage (219.1 mA h g-1 at 0.05 A g-1) and outstanding rate capability (107.3 mA h g-1 at 5 A g-1). In addition, a slight volume change of 8.1% is identified upon Zn2+ storage, which favors a prolonged cycling life (50.3% capacity remaining in 1500 cycles). More significantly, the D-TiS1.94||ZnxMnO2 full battery demonstrates a high discharge capacity of 155.7 mA h g-1 with a capacity retention of 59.8% in 400 cycles. It has been estimated that the high-capacity, low-operation voltage, and long-life D-TiS1.94 can be a promising component of the ZIB anode material family, and the strategy proposed in this work will provide guidance to the defect engineering of high-performance electrode materials toward energy storage applications.

In situ electrochemical Mn vacancies in CoMnHCF for a high level of zinc storage

CoMnHCF is utilized in aqueous sodium/zinc mixed ion batteries and exhibits a high reversible capacity with good rate and cycle performances. At 0.05 A g-1 current density, the CoMnHCF can deliver a specific capacity for 180.4 mA h g-1, and have 99.3% capacity retention after 300 cycles at 0.3 A g-1. Such high reversible capacity profits from Mn vacancies that generate in situ during the first cycle, which provides more active sites for Zn storage. The de-intercalation of Na+ further elevates this good electrochemical performance. Co atoms in the framework are not only involved in the redox reactions, but help to support the structure, thus achieving better cycle stabilities.

Additives for Aqueous Zinc-Ion Batteries: Recent Progress, Mechanism Analysis, and Future Perspectives

Aqueous zinc-ion batteries (ZIBs) stand out as a promising next-generation electrochemical energy storage technology, offering notable advantages such as high specific capacity, enhanced safety, and cost-effectiveness. However, the application of aqueous electrolytes introduces challenges: Zn dendrite formation and parasitic reactions at the anode, as well as dissolution, electrostatic interaction, and by-product formation at the cathode. In addressing these electrode-centric problems, additive engineering has emerged as an effective strategy. This review delves into the latest advancements in electrolyte additives for ZIBs, emphasizing their role in resolving the existing issues. Key focus areas include improving morphology and reducing side reactions during battery cycling using synergistic effects of modulating anode interface regulation, zinc facet control, and restructuring of hydrogen bonds and solvation sheaths. Special attention is given to the efficacy of amino acids and zwitterions due to their multifunction to improve the cycling performance of batteries concerning cycle stability and lifespan. Additionally, the recent additive advancements are studied for low-temperature and extreme weather applications meticulously. This review concludes with a holistic look at the future of additive engineering, underscoring its critical role in advancing ZIB performance amidst the complexities and challenges of electrolyte additives.

SnS2 quantum dots-coated VO2@carbon nanorods for secondary battery displaying high capacity and rate-performance

Electrode materials optimization is one of the keys to improving the energy storage characteristics of secondary batteries. Herein, a VO2@carbon@SnS2 composite is developed by coating SnS2 quantum dots (QDs) on lamellar VO2@carbon nanorods, yielding a high-performance aluminum-ion battery cathode. SnS2 QDs embedded in VO2@carbon accelerate electron transport, while the in situ coating of carbon improves cycling stability. When cycling at 0.5 A g-1, capacity is maintained at 157.6 mA h g-1 after 200 cycles. Even at 1.0 A g-1, the cathode can be stably cycled 1000 times. Capacity remains at 176.3 mA h g-1 and coulombic efficiency is 99.1% at temperatures below -10 °C after 100 cycles. These findings provide new ideas for the development of QD-modified composites for application in secondary batteries.

Validating Operating Stability and Biocompatibility Toward Safer Zinc-Based Batteries

Wearable and implantable electronics are standing at the frontiers of science and technology, driven by the increasing demands from modernized lifestyles. Zinc-based batteries (ZBs) are regarded as ideal energy suppliers for these biocompatible electronics, but the corresponding biocompatibility validation is still in the initial stage. Meanwhile, complicated working conditions and some extreme electrolyte environments raise strict challenges, leaving less choices for safe ZBs. Toward higher operating stability and biocompatibility, this work proposes a hydrogel electrolyte featuring the moisture maintaining ability and a robust interface, which could further provide a milder environment for Zn-MnO2 batteries and Zn-air batteries. The cytotoxicity and tissue injury of batteries are evaluated with human cell lines and battery implantations on the animal models, which demonstrate the high biocompatibility of ZBs, while preliminary wearable devices implementation further verifies their operating stability. This work may provide a pathway for developing and validating biocompatible ZBs, contributing to their future practical employment in relevant fields.

A Hydrogel Electrolyte toward a Flexible Zinc-Ion Battery and Multifunctional Health Monitoring Electronics

The compact design of an environmentally adaptive battery and effectors forms the foundation for wearable electronics capable of time-resolved, long-term signal monitoring. Herein, we present a one-body strategy that utilizes a hydrogel as the ionic conductive medium for both flexible aqueous zinc-ion batteries and wearable strain sensors. The poly(vinyl alcohol) hydrogel network incorporates nano-SiO2 and cellulose nanofibers (referred to as PSC) in an ethylene glycol/water mixed solvent, balancing the mechanical properties (tensile strength of 6 MPa) and ionic diffusivity at -20 °C (2 orders of magnitude higher than 2 M ZnCl2 electrolyte). Meanwhile, cathode lattice breathing during the solvated Zn2+ intercalation and dendritic Zn protrusion at the anode interface are mitigated. Besides the robust cyclability of the Zn∥PSC∥V2O5 prototype within a wide temperature range (from -20 to 80 °C), this microdevice seamlessly integrates a zinc-ion battery with a strain sensor, enabling precise monitoring of the muscle response during dynamic body movement. By employing transmission-mode operando XRD, the self-powered sensor accurately documents the real-time phasic evolution of the layered cathode and synchronized strain change induced by Zn deposition, which presents a feasible solution of health monitoring by the miniaturized electronics.

Toward Simultaneous Dense Zinc Deposition and Broken Side-Reaction Loops in the Zn//V2 O5 System

The Zn//V2 O5 system not only faces the incontrollable growth of zinc (Zn) dendrites, but also withstands the cross-talk effect of by-products produced from the cathode side to the Zn anode, inducing interelectrode talk and aggravating battery failure. To tackle these issues, we construct a rapid Zn2+ -conducting hydrogel electrolyte (R-ZSO) to achieve Zn deposition modulation and side reaction inhibition in Zn//V2 O5 full cells. The polymer matrix and BN exhibit a robust anchoring effect on SO4 2- , accelerating Zn2+ migration and enabling dense Zn deposition behavior. Therefore, the Zn//Zn symmetric cells based on the R-ZSO electrolyte can operate stably for more than 1500 h, which is six times higher than that of cells employing the blank electrolyte. More importantly, the R-ZSO hydrogel electrolyte effectively decouples the cross-talk effects, thus breaking the infinite loop of side reactions. As a result, the Zn//V2 O5 cells using this modified hydrogel electrolyte demonstrate stable operation over 1,000 cycles, with a capacity loss rate of only 0.028 % per cycle. Our study provides a promising gel chemistry, which offers a valuable guide for the construction of high-performance and multifunctional aqueous Zn-ion batteries.

Fast Reaction Kinetics and Commendable Low-Temperature Adaptability of Zinc Batteries Enabled by Aprotic Water-Acetamide Symbiotic Solvation Sheath

Although rechargeable aqueous zinc batteries are cost effectiveness, intrinsicly safe, and high activity, they are also known for bringing rampant hydrogen evolution reaction and corrosion. While eutectic electrolytes can effectively eliminate these issues, its high viscosity severely reduces the mobility of Zn2+ ions and exhibits poor temperature adaptability. Here, we infuse acetamide molecules with Lewis base and hydrogen bond donors into a solvated shell of Zn[(H2 O)6 ]2+ to create Zn(H2 O)3 (ace)(BF4 )2 . The viscosity of 1ace-1H2 O is 0.032 Pa s, significantly lower than that of 1ace-0H2 O (995.6 Pa s), which improves ionic conductivity (9.56 mS cm-1 ) and shows lower freezing point of -45 °C, as opposed to 1ace-0H2 O of 4.04 mS cm-1 and 12 °C, respectively. The acidity of 1ace-1H2 O is ≈2.8, higher than 0ace-1H2 O at ≈0.76, making side reactions less likely. Furthermore, benefiting from the ZnCO3 /ZnF2 -rich organic/inorganic solid electrolyte interface, the Zn || Zn cells cycle more than 1300 hours at 1 mA cm-2 , and the Zn || Cu operated over 1800 cycles with an average Coulomb efficiency of ≈99.8 %. The Zn || PANI cell cycled over 8500 cycles, with a specific capacity of 99.8 mAh g-1 at 5 A g-1 at room temperature, and operated at -40 °C with a capacity of 66.8 mAh g-1 .

Inducing preferential growth of the Zn (002) plane by using a multifunctional chelator for achieving highly reversible Zn anodes

Aqueous zinc-ion batteries (AZIBs) have demonstrated great potential for large-scale energy storage. However, their practical applications have been restricted by fast Zn dendrite growth and severe side reactions at the Zn/electrolyte interface. Herein, sodium gluconate is incorporated into a mild acidic electrolyte as a multifunctional additive to stabilize the Zn anode. Experiments and theoretical calculations reveal that the SG additive can induce planar growth of Zn along its (002) direction, thereby inhibiting Zn dendrite growth. This dendrite inhibition effect is attributed to the preferential adsorption of Zn2+ on the Zn (002) plane, while the Zn (100) and (101) planes are shielded by gluconate ions. Consequently, Zn||Zn symmetric cells with the electrolyte additive exhibit significantly prolonged cycle lives of 2000 h at 1 mA cm-2, 1 mA h cm-2 and 900 h at 5 mA cm-2, 2.5 mA h cm-2. Futhermore, the Zn||NH4V4O10 full cell retains 95% of its initial capacity after 2000 cycles at a current density of 5 A g-1 with an average CE of nearly 100%. This work offers a cost-effective strategy to enhance the electrochemical performance of AZIBs.

Butterfly-tie like MnCO3@Mn3O4 heterostructure enhanced the electrochemical performances of aqueous zinc ion batteries

Due to the limited exploitation and utilization of fossil energy resources in recent years, it is imperative to explore and develop new energy materials. As an electrode material for batteries, MnCO3 has the advantages of safety, non-toxicity, and wide availability of raw materials. But it also has some disadvantages, such as short cycle period and low conductivity. In order to improve these deficiencies, we designed a MnCO3@Mn3O4 heterostructure material by a simple solvothermal method, which possessed a microstructure of "butterfly-tie". Owing to the introduction of Mn3O4 and the layered structure of "butterfly-tie", MnCO3@Mn3O4 possessed a discharge capacity of 165 mAh/g when the current density was 0.2 A/g and exhibited satisfactory rate performance. The MnCO3@Mn3O4 heterostructure was optimized by density functional theory (DFT), and the deformation charge density was calculated. It was found that the MnCO3@Mn3O4 heterostructure is stable owing to the molecular interaction between the O atoms from MnCO3 and the Mn atoms from Mn3O4 at the interface of heterojunction. Therefore, the MnCO3@Mn3O4 heterostructure material has promising applications as safe and efficient cathode material for energy batteries.