Proton-Reservoir Hydrogel Electrolyte for Long-Term Cycling Zn/PANI Batteries in Wide Temperature Range

Advanced aqueous batteries are promising for next generation flexible devices owing to the high safety, yet still requiring better cycling stability and high capacities in wide temperature range. Herein, a polymeric acid hydrogel electrolyte (PAGE) with 3 M Zn(ClO₄)₂ was fabricated for high performance Zn/polyaniline (PANI) batteries. With PAGE, even at −35 °C the Zn/Zn symmetrical battery can keep stable for more than 1 500 h under 2 mA cm⁻², and the Zn/PANI battery can provide ultra-high stable specific capacity of 79.6 mAh g⁻¹ for more than 70 000 cycles at 15 A g⁻¹. This can be mainly ascribed to the −SO₃⁻H⁺ function group in PAGE. It can generate constant protons and guide the (002) plane formation to accelerate the PANI redox reaction kinetics, increase the specific capacity, and suppress the side reaction and dendrites. This proton-supplying strategy by polymeric acid hydrogel may further propel the development of high performance aqueous batteries.     

Solvation Modulation Enhances Anion-Derived Solid Electrolyte Interphase for Deep Cycling of Aqueous Zinc Metal Batteries

Stable Zn anodes with a high utilization efficiency pose a challenge due to notorious dendrite growth and severe side reactions. Therefore, electrolyte additives are developed to address these issues. However, the additives are always consumed by the electrochemical reactions over cycling, affecting the cycling stability. Here, hexamethylphosphoric triamide (HMPA) is reported as an electrolyte additive for achieving stable cycling of Zn anodes. HMPA reshapes the solvation structures and promotes anion decomposition, leading to the in situ formation of inorganic-rich solid-electrolyte-interphase. More interestingly, this anion decomposition does not involve HMPA, preserving its long-term impact on the electrolyte. Thus, the symmetric cells with HMPA in the electrolyte survive ≈500 h at 10 mA cm⁻² for 10 mAh cm⁻² or ≈200 h at 40 mA cm⁻² for 10 mAh cm⁻² with a Zn utilization rate of 85.6 %. The full cells of Zn||V₂O₅ exhibit a record-high cumulative capacity even under a lean electrolyte condition (E/C ratio=12 μL mAh⁻¹), a limited Zn supply (N/P ratio=1.8) and a high areal capacity (6.6 mAh cm⁻²).     

High-Voltage Rechargeable Alkali–Acid Zn–PbO2 Hybrid Battery

Aqueous rechargeable batteries have attracted attention owning to their advantages of safety, low cost, and sustainability, while the limited electrochemical stability window (1.23 V) of water leads to their failure in competition with organic-based lithium-ion batteries. Herein, we report an alkali–acid Zn–PbO₂ hybrid aqueous battery obtained by coupling an alkaline Zn anode with an acidic PbO₂ cathode. It shows the capability to deliver an impressively high open-circuit voltage (V_oc) of 3.09 V and an operate voltage of 2.95 V at 5 mA cm⁻², thanks to the contribution of expanding the voltage window and the electrochemical neutralization energy from the alkali–acid asymmetric-electrolyte hybrid cell. The hybrid battery can potentially deliver a large area capacity over 2 mAh cm⁻² or a high energy density of 252.39 Wh kg⁻¹ and shows almost no fading in area capacity over 250 charge–discharge cycles.     

Amphoteric Cellulose-Based Double-Network Hydrogel Electrolyte Toward Ultra-Stable Zn Anode

Zinc (Zn) metal anode suffers from uncontrollable Zn dendrites and parasitic side reactions at the interface, which restrict the practical application of aqueous rechargeable zinc batteries (ARZBs). Herein, an amphoteric cellulose-based double-network is introduced as hydrogel electrolyte to overcome these obstacles. On one hand, the amphoteric groups build anion/cation transport channels to regulate electro-deposition behavior on Zn (002) crystal plane enabled by homogenizing Zn²⁺ ions flux. On the other hand, the strong bonding between negatively charged carboxyl groups and Zn²⁺ ions promote the desolvation process of [Zn(H₂O)₆]²⁺ to eliminate side reactions. Based on the above two functions, the hydrogel electrolyte enables an ultra-stable cycling with a cumulative capacity of 7 Ah cm⁻² at 20 mA cm⁻²/20 mAh cm⁻² for Zn||Zn cell. This work provides significant concepts for developing hydrogel electrolytes to realize stable anode for high-performance ARZBs.     

Boosting Zn Anode Utilization by Trace Iodine Ions in Organic-Water Hybrid Electrolytes through Formation of Anion-rich Adsorbing Layers

Aqueous Zn batteries are attracting extensive attentions, but their application is still hindered by H₂O-induced Zn-corrosion and hydrogen evolution reactions. Addition of organic solvents into aqueous electrolytes to limit the H₂O activity is a promising solution, but at the cost of greatly reduced Zn anode kinetics. Here we propose a simple strategy for this challenge by adding 50 mM iodine ions into an organic-water (1,2-dimethoxyethane (DME)+water) hybrid electrolyte, which enables the electrolyte simultaneously owns the advantages of low H₂O activity and accelerated Zn kinetics. We demonstrate that the DME breaks the H₂O hydrogen-bond network and exclude H₂O from Zn²⁺ solvation shell. And the I⁻ is firmly adsorbed on the Zn anode, reducing the Zn²⁺ de-solvation barrier from 74.33 kJ mol⁻¹ to 32.26 kJ mol⁻¹ and inducing homogeneous nucleation behavior. With such electrolyte, the Zn//Zn symmetric cell exhibits a record high cycling lifetime (14.5 months) and achieves high Zn anode utilization (75.5 %). In particular, the Zn//VS₂@SS full cell with the optimized electrolyte stably cycles for 170 cycles at a low N : P ratio (3.64). Even with the cathode mass-loading of 16.7 mg cm⁻², the full cell maintains the areal capacity of 0.96 mAh cm⁻² after 1600 cycles.     

Organic pH Buffer for Dendrite-Free and Shuttle-Free Zn-I2 Batteries

Aqueous Zn-Iodine (I₂) batteries are attractive for large-scale energy storage. However, drawbacks include, Zn dendrites, hydrogen evolution reaction (HER), corrosion and, cathode “shuttle” of polyiodines. Here we report a class of N-containing heterocyclic compounds as organic pH buffers to obviate these. We evidence that addition of pyridine /imidazole regulates electrolyte pH, and inhibits HER and anode corrosion. In addition, pyridine and imidazole preferentially absorb on Zn metal, regulating non-dendritic Zn plating /stripping, and achieving a high Coulombic efficiency of 99.6 % and long-term cycling stability of 3200 h at 2 mA cm⁻², 2 mAh cm⁻². It is also confirmed that pyridine inhibits polyiodines shuttling and boosts conversion kinetics for I⁻/I₂. As a result, the Zn-I₂ full battery exhibits long cycle stability of >25 000 cycles and high specific capacity of 105.5 mAh g⁻¹ at 10 A g⁻¹. We conclude organic pH buffer engineering is practical for dendrite-free and shuttle-free Zn-I₂ batteries.     

Proton Intercalation/De-intercalation Chemistry in Phenazine-based Anode for Hydronium-ion Batteries

Hydronium-ion batteries have received significant attention owing to the merits of extraordinary sustainability and excellent rate abilities. However, achieving high-performance hydronium-ion batteries remains a challenge due to the inferior properties of anode materials in strong acid electrolyte. Herein, a hydronium-ion battery is constructed which is based on a diquinoxalino [2,3-a:2’,3’-c] phenazine (HATN) anode and a MnO₂@graphite felt cathode in a hybrid acidic electrolyte. The fast kinetics of hydronium-ion insertion/extraction into HATN electrode endows the HATN//MnO₂@GF battery with enhanced electrochemical performance. This battery exhibits an excellent rate performance (266 mAh g⁻¹ at 0.5 A g⁻¹, 97 mAh g⁻¹ at 50 A g⁻¹), attractive energy density (182.1 Wh kg⁻¹) and power density (31.2 kW kg⁻¹), along with long-term cycle stability. These results shed light on the development of advanced hydronium-ion batteries.     

Synergistic Modulation of In-Situ Hybrid Interface Construction and pH Buffering Enabled Ultra-Stable Zinc Anode at High Current Density and Areal Capacity

In aqueous electrolytes, the uncontrollable interfacial evolution caused by a series of factors such as pH variation and unregulated Zn²⁺ diffusion would usually result in the rapid failure of metallic Zn anode. Considering the high correlation among various triggers that induce the anode deterioration, a synergistic modulation strategy based on electrolyte modification is developed. Benefitting from the unique pH buffer mechanism of the electrolyte additive and its capability to in situ construct a zincophilic solid interface, this synergistic effect can comprehensively manage the thermodynamic and kinetic properties of Zn anode by inhibiting the pH variation and parasitic side reactions, accelerating de-solvation of hydrated Zn²⁺, and regulating the diffusion behavior of Zn²⁺ to realize uniform Zn deposition. Thus, the modified Zn anode can achieve an impressive lifespan at ultra-high current density and areal capacity, operating stably for 609 and 209 hours at 20 mA cm⁻², 20 mAh cm⁻² and 40 mA cm⁻², 20 mAh cm⁻², respectively. Based on this exceptional performance, high loading Zn||NH₄V₄O₁₀ batteries can achieve excellent cycle stability and rate performance. Compared with those previously reported single pH buffer strategies, the synergistic modulation concept is expected to provide a new approach for highly stable Zn anode in aqueous zinc-ion batteries.     

Regulated Ion/Electron-Conducting Interphase Enables Stable Zinc-Metal Anodes for Aqueous Zinc-Ions Batteries

Metallic Zinc (Zn) is considered as a remarkably promising anode for aqueous Zn-ion batteries due to its high volumetric capacity and low redox potential. Unfortunately, dendritic growth and severe side reactions destabilizes the electrode/electrolyte interface, and ultimately reduce the electrochemical performance. Here, an artificial protective layer (APL) with a regulated ion and electron-conducting interphase is constructed on the Zn-metal anode to provide excellent interfacial stability in high-rate cycling. The superior ionic and moderate electronic conductivity of the APL derives from the co-embedding of MXene and Zn(CF₃SO₃)₂ salts into the polyvinyl alcohol hydrogel, which enables a synergistic effect of local current density reduction during plating and ion transport acceleration during stripping for Zn anode. Furthermore, the high Young's modulus of the protective layer and dendrite-free deposition morphology during cycling suppresses hydrogen evolution reactions (2.5 mmol h⁻¹ cm⁻²) and passivation. As a result, in symmetrical cell tests, the modified battery presents a stable life of over 2000 cycles at ultra-high current density of 20 mA cm⁻². This research presents a new insight into the formation and regulation of stable electrode-electrolyte interface for the Zn-metal anode.     

A Full Li–S Battery with Ultralow Excessive Li Enabled via Lithiophilic and Sulfilic W2C Modulation

The practical application of Li–S batteries demands low cell balance (Li_capacity/S_capacity), which involves uniform Li growth, restrained shuttle effect, and fast redox reaction kinetics of S species simultaneously. Herein, with the aid of W₂C nanocrystals, a freestanding 3D current collector is applied as both Li and S hosts owing to its lithiophilic and sulfilic property. On the one hand, the highly conductive W₂C can reduce Li nucleation overpotentials, thus guiding uniform Li nucleation and deposition to suppress Li dendrite growth. On the other hand, the polar W₂C with catalytic effect can enhance the chemisorption affinity to lithium polysulfides (LiPSs) and guarantee fast redox kinetics to restrain S species in cathode region and promote the utilization of S. Surprisingly, a full Li–S battery with ultralow cell balance of 1.5:1 and high sulfur loading of 6.06 mg cm⁻² shows obvious redox plateaus of S and maintains high reversible specific capacity of 1020 mAh g⁻¹ (6.2 mAh cm⁻²) after 200 cycles. This work may shed new sights on the facile design of full Li–S battery with low excessive Li supply.     

Constructing a Super-Saturated Electrolyte Front Surface for Stable Rechargeable Aqueous Zinc Batteries

Rechargeable aqueous zinc batteries (RAZB) have been re-evaluated because of the superiority in addressing safety and cost concerns. Nonetheless, the limited lifespan arising from dendritic electrodeposition of metallic Zn hinders their further development. Herein, a metal–organic framework (MOF) was constructed as front surface layer to maintain a super-saturated electrolyte layer on the Zn anode. Raman spectroscopy indicated that the highly coordinated ion complexes migrating through the MOF channels were different from the solvation structure in bulk electrolyte. Benefiting from the unique super-saturated front surface, symmetric Zn cells survived up to 3000 hours at 0.5 mA cm⁻², near 55-times that of bare Zn anodes. Moreover, aqueous MnO₂–Zn batteries delivered a reversible capacity of 180.3 mAh g⁻¹ and maintained a high capacity retention of 88.9 % after 600 cycles with MnO₂ mass loading up to 4.2 mg cm⁻².     

Zincophilic Interfacial Manipulation against Dendrite Growth and Side Reactions for Stable Zn Metal Anodes

Constructing multifunctional interphases to suppress the rampant Zn dendrite growth and detrimental side reactions is crucial for Zn anodes. Herein, a phytic acid (PA)-ZnAl coordination compound is demonstrated as a versatile interphase layer to stabilize Zn anodes. The zincophilic PA-ZnAl layer can manipulate Zn²⁺ flux and promote rapid desolvation kinetics, ensuring the uniform Zn deposition with dendrite-free morphology. Moreover, the robust PA-ZnAl protective layer can effectively inhibit the hydrogen evolution reaction and formation of byproducts, further contributing to the reversible Zn plating/stripping with high Coulombic efficiency. As a result, the Zn@PA-ZnAl electrode shows a lower Zn nucleation overpotential and higher Zn²⁺ transference number compared with bare Zn. The Zn@PA-ZnAl symmetric cell exhibits a prolonged lifespan of 650 h tested at 5 mA cm⁻² and 5 mAh cm⁻². Furthermore, the assembled Zn battery full cell based on this Zn@PA-ZnAl anode also delivers decent cycling stability even under harsh conditions.     

An Environmentally Friendly and Flexible Aqueous Zinc Battery Using an Organic Cathode

Rechargeable batteries have been used to power various electric devices and store energy from renewables, but their toxic components (namely, electrode materials, electrolyte, and separator) generally cause serious environment issues when disused. Such toxicity characteristic makes them difficult to power future wearable electronic devices. Now an environmentally friendly and highly safe rechargeable battery, based on a pyrene‐4,5,9,10‐tetraone (PTO) cathode and zinc anode in mild aqueous electrolyte is presented. The PTO‐cathode shows a high specific capacity (336 mAh g^?1) for Zn²⁺ storage with fast kinetics and high reversibility. Thus, the PTO//Zn full cell exhibits a high energy density (186.7 Wh kg^?1), supercapacitor‐like power behavior and long‐term lifespan (over 1000 cycles). Moreover, a belt‐shaped PTO//Zn battery with robust mechanical durability and remarkable flexibility is first fabricated to clarify its potential application in wearable electronic devices.     

In Situ Electrochemical Activation of Hydroxyl Polymer Cathode for High-Performance Aqueous Zinc–Organic Batteries

The slow reaction kinetics and structural instability of organic electrode materials limit the further performance improvement of aqueous zinc-organic batteries. Herein, we have synthesized a Z-folded hydroxyl polymer polytetrafluorohydroquinone (PTFHQ) with inert hydroxyl groups that could be partially oxidized to the active carbonyl groups through the in situ activation process and then undertake the storage/release of Zn²⁺. In the activated PTFHQ, the hydroxyl groups and S atoms enlarge the electronegativity region near the electrochemically active carbonyl groups, enhancing their electrochemical activity. Simultaneously, the residual hydroxyl groups could act as hydrophilic groups to enhance the electrolyte wettability while ensuring the stability of the polymer chain in the electrolyte. Also, the Z-folded structure of PTFHQ plays an important role in reversible binding with Zn²⁺ and fast ion diffusion. All these benefits make the activated PTFHQ exhibit a high specific capacity of 215 mAh g⁻¹ at 0.1 A g⁻¹, over 3400 stable cycles with a capacity retention of 92 %, and an outstanding rate capability of 196 mAh g⁻¹ at 20 A g⁻¹.     

Highly Reversible Cuprous Mediated Cathode Chemistry for Magnesium Batteries

Sluggish kinetics and poor reversibility of cathode chemistry is the major challenge for magnesium batteries to achieve high volumetric capacity. Introduction of the cuprous ion (Cu⁺) as a charge carrier can decouple the magnesiation related energy storage from the cathode electrochemistry. Cu⁺ is generated from a fast equilibrium between copper selenide electrode and Mg electrolyte during standing time, rather than in the electrochemical process. A reversible chemical magnesiation/de‐magnesiation can be driven by this solid/liquid equilibrium. During a typical discharge process, Cu⁺ is reduced to Cu and drives the equilibrium to promote the magnesiation process. The reversible Cu to Cu⁺ redox promotes the recharge process. This novel Cu⁺ mediated cathode chemistry of Mg battery leads to a high reversible areal capacity of 12.5 mAh cm^?2 with high mass loading (49.1 mg cm^?2) of the electrode. 80 % capacity retention can be achieved for 200 cycles after a conditioning process.     

Phenol-Catalyzed Discharge in the Aprotic Lithium-Oxygen Battery

Discharge in the lithium-O₂ battery is known to occur either by a solution mechanism, which enables high capacity and rates, or a surface mechanism, which passivates the electrode surface and limits performance. The development of strategies to promote solution-phase discharge in stable electrolyte solutions is a central challenge for development of the lithium-O₂ battery. Here we show that the introduction of the protic additive phenol to ethers can promote a solution-phase discharge mechanism. Phenol acts as a phase-transfer catalyst, dissolving the product Li₂O₂, avoiding electrode passivation and forming large particles of Li₂O₂ product—vital requirements for high performance. As a result, we demonstrate capacities of over 9 mAh cm⁻²_areal, which is a 35-fold increase in capacity compared to without phenol. We show that the critical requirement is the strength of the conjugate base such that an equilibrium exists between protonation of the base and protonation of Li₂O₂.     

Beyond the Polysulfide Shuttle and Lithium Dendrite Formation: Addressing the Sluggish Sulfur Redox Kinetics for Practical High-Energy Li-S Batteries

Electrolyte modulation simultaneously suppresses polysulfide the shuttle effect and lithium dendrite formation of lithium–sulfur (Li-S) batteries. However, the sluggish S redox kinetics, especially under high S loading and lean electrolyte operation, has been ignored, which dramatically limits the cycle life and energy density of practical Li-S pouch cells. Herein, we demonstrate that a rational combination of selenium doping, core–shell hollow host structure, and fluorinated ether electrolytes enables ultrastable Li stripping/plating and essentially no polysulfide shuttle as well as fast redox kinetics. Thus, high areal capacity (>4 mAh cm⁻²) with excellent cycle stability and Coulombic efficiency were both demonstrated in Li metal anode and thick S cathode (4.5 mg cm⁻²) with a low electrolyte/sulfur ratio (10 μL mg⁻¹). This research further demonstrates a durable Li-Se/S pouch cell with high specific capacity, validating the potential practical applications.     

Engineering Fluorine-rich Double Protective Layer on Zn Anode for Highly Reversible Aqueous Zinc-ion Batteries

The high thermodynamic instability and side reactions of Zn-metal anode (ZMA), especially at high current densities, greatly impede the commercialization of aqueous zinc-ion batteries (AZIBs). Herein, a fluorine-rich double protective layer strategy is proposed to obtain the high reversibility of AZIBs through the introduction of a versatile tetradecafluorononane-1,9-diol (TDFND) additive in aqueous electrolyte. TDFND molecule with large adsorption energy (−1.51 eV) preferentially absorbs on the Zn anode surface to form a Zn(OR)₂⁻ (R=−CH₂−(CF₂)₇−CH₂−) cross-linking complex network, which balances space electric field and controls the Zn²⁺ ion flux, thus enabling the uniform and compact deposition of Zn (002) crystal planes. Meanwhile, TDFND with low Lowest unoccupied molecular orbital (LUMO, 0.10 eV) energy level is priorly decomposed to regulate the interfacial chemistry of ZMA by building a ZnF₂-rich solid electrode/electrolyte interface (SEI) layer. It is found that a 14 nm-thick SEI layer delivers excellent structural integrity to suppress parasitic reactions by blocking the direct contact of active water and ZMA. Consequently, the Zn electrode exhibits a superior cycling life over 430 h at 10 mA cm⁻² and a high average Coulombic efficiency of 99.8 % at 5 mA cm⁻². Furthermore, a 68 mAh pouch cell delivers 80.3 % capacity retention for 1000 cycles.     

可充锌电池电解(质)液调控策略

高安全、低成本、长寿命的大规模储能新技术的突破事关未来能源结构调整以及智能电网建设。可充锌电池由于其安全性高、环境友好、成本低等优势而成为将来储能系统的重要选择。然而,常规水系电解液的应用通常导致正极活性物质溶解、水溶剂分解、锌负极腐蚀、枝晶等问题。因此,本文对水系电解质（液）体系导致的问题及相应的调控方案进行了讨论与总结。主要从电解质（液）改性角度分析了通过调控组成成分、浓度、添加剂等变量以达到改变自由水含量和锌离子溶剂化结构的目的。另外,对可充电锌电池这一新兴技术实现应用所面临的挑战进行了总结与展望。     

Electrocrystallization Regulation Enabled Stacked Hexagonal Platelet Growth toward Highly Reversible Zinc Anodes

Realizing durative flattened and dendrite-free zinc (Zn) metal configuration is the key to resolving premature battery failure caused by the internal short circuit, which is highly determined by the crystal growth in the electrocrystallization process. Herein, we report that regulating the molecular structure of the inner Helmholtz plane (HIP) can effectively convert the deposition into activation control by weakening the solvated ion adsorption at the interface. The moderated electrochemical reaction kinetics lower than the adatom self-diffusion rate steers conformal stratiform Zn growth and dominant Zn (0001) texture, achieving crystallographic optimization. Through in situ mediation of electrolyte engineering, orientational plating and stripping behaviors at edge-sites and tailored solvation structure immensely improve the utilization efficiency and total charge passed of Zn metal, even under extreme conditions, including high areal capacity (3 mAh cm⁻²) and wide temperature range (−40–60 °C).