An All-Climate Nonaqueous Hydrogen Gas-Proton Battery.

Rechargeable hydrogen gas batteries, driven by hydrogen evolution and oxidation reactions (HER/HOR), are emerging grid-scale energy storage technologies owing to their low cost and superb cycle life. However, compared with aqueous electrolytes, the HER/HOR activities in nonaqueous electrolytes have rarely been studied. Here, for the first time, we develop a nonaqueous proton electrolyte (NAPE) for a high-performance hydrogen gas-proton battery for all-climate energy storage applications. The advanced nonaqueous hydrogen gas-proton battery (NAHPB) assembled with a representative V2(PO4)3 cathode and H2 anode in a NAPE exhibits a high discharge capacity of 165 mAh g-1 at 1 C at room temperature. It also efficiently operates under all-climate conditions (from -30 to +70 °C) with an excellent electrochemical performance. Our findings offer a new direction for designing nonaqueous proton batteries in a wide temperature range.

Rechargeable Batteries for Grid Scale Energy Storage.

Ever-increasing global energy consumption has driven the development of renewable energy technologies to reduce greenhouse gas emissions and air pollution. Battery energy storage systems (BESS) with high electrochemical performance are critical for enabling renewable yet intermittent sources of energy such as solar and wind. In recent years, numerous new battery technologies have been achieved and showed great potential for grid scale energy storage (GSES) applications. However, their practical applications have been greatly impeded due to the gap between the breakthroughs achieved in research laboratories and the industrial applications. In addition, various complex applications call for different battery performances. Matching of diverse batteries to various applications is required to promote practical energy storage research achievement. This review provides in-depth discussion and comprehensive consideration in the battery research field for GSES. The overall requirements of battery technologies for practical applications with key parameters are systematically analyzed by generating standards and measures for GSES. We also discuss recent progress and existing challenges for some representative battery technologies with great promise for GSES, including metal-ion batteries, lead-acid batteries, molten-salt batteries, alkaline batteries, redox-flow batteries, metal-air batteries, and hydrogen-gas batteries. Moreover, we emphasize the importance of bringing emerging battery technologies from academia to industry. Our perspectives on the future development of batteries for GSES applications are provided.

Reversible, Dendrite-Free, High-Capacity Aluminum Metal Anode Enabled by Aluminophilic Interface Layer.

Aluminum (Al) metal is an attractive anode material for next-generation rechargeable batteries, because of its low cost and high capacities. However, it brings some fundamental issues such as dendrites, low Coulombic efficiency (CE), and low utilization. Here, we propose a strategy for constructing an ultrathin aluminophilic interface layer (AIL) to regulate the Al nucleation and growth behaviors, which enables highly reversible and dendrite-free Al plating/stripping under high areal capacity. Metallic Al can maintain stable plating/stripping on the Pt-AIL@Ti for over 2000 h at 10 mAh cm-2 with an average CE of 99.9%. The Pt-AIL also enables reversible Al plating/stripping at a record high areal capacity of 50 mAh cm-2, which is 1-2 orders of magnitude higher than the previous studies. This work provides a valuable direction for further construction of high-performance rechargeable Al metal batteries.

Organocatalytic Lithium Chloride Oxidation by Covalent Organic Frameworks for Rechargeable Lithium-Chlorine Batteries.

Rechargeable Li-Cl2 battery is a promising high energy density battery system. However, reasonable cycle life could only be achieved under low specific capacities due to the sluggish oxidation of LiCl to Cl2 . Herein, we propose an amine-functionalized covalent organic framework (COF) with catalytic activity, namely COF-NH2 , that significantly decreases the oxidation barrier of LiCl and accelerates the oxidation kinetics of LiCl in Li-Cl2 cell. The resulting Li-Cl2 cell using COF-NH2 (Li-Cl2 @COF-NH2 ) simultaneously exhibits low overpotential, ultrahigh discharge capacity up to 3500 mAh/g and a promoted utilization ratio of deposited LiCl at the first cycle (UR-LiCl) of 81.4 %, which is one of the highest reported values to date. Furthermore, the Li-Cl2 @COF-NH2 cell could be stably cycled for over 200 cycles when operating at a capacity of 2000 mAh/g at -20 °C with a Coulombic efficiency (CE) of ≈100 % and a discharge plateau of 3.5 V. Our superior Li-Cl2 batteries enabled by organocatalyst enlighten an arena towards high-energy storage applications.

Bidentate Coordination Structure Facilitates High-Voltage and High-Utilization Aqueous Zn-I2 Batteries.

The zinc-iodine aqueous battery is a promising energy storage device, but the conventional two-electron reaction potential and energy density of the iodine cathode are far from meeting practical application requirements. Given that iodine is rich in redox reactions, activating the high-valence iodine cathode reaction has become a promising research direction for developing high-voltage zinc-iodine batteries. In this work, by designing a multifunctional electrolyte additive trimethylamine hydrochloride (TAH), a stable high-valence iodine cathode in four-electron-transfer I-/I2/I+ reactions with a high theoretical specific capacity is achieved through a unique amine group, Cl bidentate coordination structure of (TA)ICl. Characterization techniques such as synchrotron radiation, in-situ Raman spectra, and DFT calculations are used to verify the mechanism of the stable bidentate structure. This electrolyte additive stabilizes the zinc anode by promoting the desolvation process and shielding mechanism, enabling the zinc anode to cycle steadily at a maximum areal capacity of 57 mAh cm-2 with 97% zinc utilization rate. Finally, the four-electron-transfer aqueous Zn-I2 full cell achieves 5000 stable cycles at an N/P ratio of 2.5. The unique bidentate coordination structure contributes to the further development of high-valence and high capacity aqueous zinc-iodine batteries.

Enrichment of Chlorine in Porous Organic Nanocages for High-Performance Rechargeable Lithium-Chlorine Batteries.

Rechargeable Li-Cl2 batteries are recognized as promising candidates for energy storage due to their ultrahigh energy densities and superior safety features. However, Li-Cl2 batteries suffer from a short cycle life and low Coulombic efficiency (CE) at a high specific cycling capacity due to a sluggish and insufficient Cl2 supply during the redox reaction. To achieve Li-Cl2 batteries with high discharge capacity and CE, herein, we propose and design an imine-functionalized porous organic nanocage (POC) to enrich Cl2 molecules. Based on density functional theory (DFT) calculations, the imine group sites in host cages strongly interact with Cl2 molecules, facilitating the rapid capture of Cl2. As a result, the output capacity of the Li-Cl2 battery using POC (Li-Cl2@POC) is significantly boosted, achieving an ultrahigh discharge capacity of 4000 mAh/g at ∼100% CE. Benefiting from the designed POC, the highest utilization ratio of deposited LiCl at the first cycle in the Li-Cl2@POC battery reaches as high as 85%, superior to all reported values. The Li-Cl2@POC battery exhibits excellent electrochemical performance even at low temperatures, delivering stable cycling over 200 cycles under a capacity of 2000 mAh/g at -20 °C with a voltage plateau of 3.5 V and an average CE of 99.7%. We also demonstrate that the Li-Cl2@POC cells can be assembled and well-operated in a dry room, showing advantages for mass production. Our designed POC promotes the practical deployment of rechargeable Li-Cl2 batteries.

Rechargeable Hydrogen-Chlorine Battery Operates in a Wide Temperature Range.

Hydrogen-chlorine (H2-Cl2) fuel cells have distinct merits due to fast electrochemical kinetics but are afflicted by high cost, low efficiency, and poor reversibility. The development of a rechargeable H2-Cl2 battery is highly desirable yet challenging. Here, we report a rechargeable H2-Cl2 battery operating statically in a wide temperature ranging from -70 to 40 °C, which is enabled by a reversible Cl2/Cl- redox cathode and an electrocatalytic H2 anode. A hierarchically porous carbon cathode is designed to achieve effective Cl2 gas confinement and activate the discharge plateau of Cl2/Cl- redox at room temperature, with a discharge plateau at ∼1.15 V and steady cycling for over 500 cycles without capacity decay. Furthermore, the battery operation at an ultralow temperature is successfully achieved in a phosphoric acid-based antifreezing electrolyte, with a reversible discharge capacity of 282 mAh g-1 provided by the highly porous carbon at -70 °C and an average Coulombic efficiency of 91% for more than 300 cycles at -40 °C. This work offers a new strategy to enhance the reversibility of aqueous chlorine batteries for energy storage applications in a wide temperature range.

Facile Fabrication of Bifunctional Hydrogen Catalytic Electrodes for Long-Life Nickel-Hydrogen Gas Batteries.

The renaissance of long-lasting nickel-hydrogen gas (Ni-H2) battery by developing efficient, robust, and affordable hydrogen anode to replace Pt is particularly attractive for large-scale energy storage applications. Here, we demonstrate an extremely facile corrosion induced fabrication approach to achieve a self-supporting hydrogen evolution/oxidation reaction (HER/HOR) bifunctional nanosheet array electrode for Ni-H2 battery. The electrode is constituted by ultrafine Ru nanoparticles on Ni(OH)2 nanosheets grown on nickel foam. Experimental and theoretical calculation results reveal that the electrode with optimized geometric and electronic structures ensures the efficient and robust catalytic hydrogen activities. The fabricated Ni-H2 battery using the Ru-Ni(OH)2/NF anode with an industrial scale areal capacity of 16 mAh cm-2 demonstrates a high energy density, good rate capability and excellent durability without capacity decay over 1800 h. This study casts light on the development of low manufacturing cost and high performance bifunctional hydrogen catalytic electrodes for future hydrogen energy applications.

Balancing Interfacial Reactions through Regulating p-Band Centers by an Indium Tin Oxide Protective Layer for Stable Zn Metal Anodes.

Metallic zinc (Zn) is considered as one of the most attractive anode materials for the post-lithium metal battery systems owing to the high theoretical capacity, low cost, and intrinsic safety. However, the Zn dendrites and parasitic side reaction impede its application. Herein, we propose a new principle of regulating p-band center of metal oxide protective coating to balance Zn adsorption energy and migration energy barrier for effective Zn deposition and stripping. Experimental results and theoretical calculations indicate that benefiting from the uniform zincophilic nucleation sites and fast Zn transport on indium tin oxide (ITO), highly stable and reversible Zn anode can be achieved. As a result, the I-Zn symmetrical cell achieves highly reversible Zn deposition/stripping with an extremely low overpotential of 9 mV and a superior lifespan over 4000 h. The Cu/I-Zn asymmetrical cell exhibits a long lifetime of over 4000 cycles with high average coulombic efficiency of 99.9 %. Furthermore, the assembled I-Zn/AC full cell exhibits an excellent lifetime for 70000 cycles with nearly 100 % capacity retention. This work provides a general strategy and new insight for the construction of efficient Zn anode protection layer.

High-Capacity Zinc Anode with 96 % Utilization Rate Enabled by Solvation Structure Design.

Aqueous zinc-ion batteries (AZBs) show promises for large-scale energy storage. However, the zinc utilization rate (ZUR) is generally low due to side reactions in the aqueous electrolyte caused by the active water molecules. Here, we design a novel solvation structure in the electrolyte by introduction of sulfolane (SL). Theoretical calculations, molecular dynamics simulations and experimental tests show that SL remodels the primary solvation shell of Zn2+ , which significantly reduces the side reactions of Zn anode and achieves high ZUR under large capacities. Specifically, the symmetric and asymmetric cells could achieve a maximum of ∼96 % ZUR at an areal capacity of 24 mAh cm-2 . In a ZUR of ∼67 %, the developed Zn-V2 O5 full cell can be stably cycled for 500 cycles with an energy density of 180 Wh kg-1 and Zn-AC capacitor is stable for 5000 cycles. This electrolyte structural engineering strategy provides new insight into achieving high ZUR of Zn anodes for high performance AZBs.

Breaking Local Charge Symmetry of Iron Single Atoms for Efficient Electrocatalytic Nitrate Reduction to Ammonia.

The electrochemical conversion of nitrate pollutants into value-added ammonia is a feasible way to achieve artificial nitrogen cycle. However, the development of electrocatalytic nitrate-to-ammonia reduction reaction (NO3 - RR) has been hampered by high overpotential and low Faradaic efficiency. Here we develop an iron single-atom catalyst coordinated with nitrogen and phosphorus on hollow carbon polyhedron (denoted as Fe-N/P-C) as a NO3 - RR electrocatalyst. Owing to the tuning effect of phosphorus atoms on breaking local charge symmetry of the single-Fe-atom catalyst, it facilitates the adsorption of nitrate ions and enrichment of some key reaction intermediates during the NO3 - RR process. The Fe-N/P-C catalyst exhibits 90.3 % ammonia Faradaic efficiency with a yield rate of 17980 µg h-1 mgcat -1 , greatly outperforming the reported Fe-based catalysts. Furthermore, operando SR-FTIR spectroscopy measurements reveal the reaction pathway based on key intermediates observed under different applied potentials and reaction durations. Density functional theory calculations demonstrate that the optimized free energy of NO3 - RR intermediates is ascribed to the asymmetric atomic interface configuration, which achieves the optimal electron density distribution. This work demonstrates the critical role of atomic-level precision modulation by heteroatom doping for the NO3 - RR, providing an effective strategy for improving the catalytic performance of single atom catalysts in different electrochemical reactions.

An Ultrafast and Ultra-Low-Temperature Hydrogen Gas-Proton Battery.

Aqueous proton batteries are regarded as one of the most promising energy technologies for next-generation grid storage due to the distinctive merits of H+ charge carriers with small ionic radius and light weight. Various materials have been explored for aqueous proton batteries; however, their full batteries show undesirable electrochemical performance with limited rate capability and cycling stability. Here we introduce a novel aqueous proton full battery that shows remarkable rate capability, cycling stability, and ultralow temperature performance, which is driven by a hydrogen gas anode and a Prussian blue analogue cathode in a concentrated phosphoric acid electrolyte. Its operation involves hydrogen evolution/oxidation redox reactions on the anode and H+ insertion/extraction reactions on the cathode, in parallel with the ideal transfer of only H+ between these two electrodes. The fabricated aqueous hydrogen gas-proton battery exhibits an unprecedented charge/discharge capability of up to 960 C with a superior power density of 36.5 kW kg-1, along with an ultralong cycle life of over 0.35 million cycles. Furthermore, this hydrogen gas-proton battery is able to work well at an ultralow temperature of -80 °C with 54% of its room-temperature capacity and under -60 °C with a stable cycle life of 1150 cycles. This work provides new opportunities to construct aqueous proton batteries with high performance in extreme conditions for large-scale energy storage.

Electrode-Less MnO2 -Metal Batteries with Deposition and Stripping Chemistry.

Electrode materials are key components in typical batteries, where the electrodes are generally fabricated onto current collectors in solid forms and are isolated by a separator. However, the preparation of the electrodes increases the fabrication complexity, which speeds down their large-scale production. Here, series of static electrode-less MnO2 -metal batteries are presented that are facilely fabricated by using carbon current collectors and electrolytes. The MnO2 -metal batteries are operated in dual-deposition/stripping chemistries of Mn2+ /MnO2 on the cathode and M/Mx+ on the anode. The MnO2 -Cd/Zn/Cu batteries exhibit remarkable rates up to 200 C, excellent reversibility of 15 000 cycles, and realistic gravimetric and volumetric energy densities of 93.7 Wh kg-1 and 134 Wh L-1 , respectively. Impressively, the MnO2 -Cd battery can achieve over 160 000 cycles in the high current pulse test, showing promises in the applications of electrical vehicle's start-stop and large-scale energy storage.

A High-Rate Lithium Manganese Oxide-Hydrogen Battery.

Rechargeable hydrogen gas batteries show promises for the integration of renewable yet intermittent solar and wind electricity into the grid energy storage. Here, we describe a rechargeable, high-rate, and long-life hydrogen gas battery that exploits a nanostructured lithium manganese oxide cathode and a hydrogen gas anode in an aqueous electrolyte. The proposed lithium manganese oxide-hydrogen battery shows a discharge potential of ∼1.3 V, a remarkable rate of 50 C with Coulombic efficiency of ∼99.8%, and a robust cycle life. A systematic electrochemical study demonstrates the significance of the electrocatalytic hydrogen gas anode and reveals the charge storage mechanism of the lithium manganese oxide-hydrogen battery. This work provides opportunities for the development of new rechargeable hydrogen batteries for the future grid-scale energy storage.

Ultralow-Temperature Aqueous Conductive Polymer-Hydrogen Gas Battery.

Hydrogen gas batteries are regarded as one of the most promising rechargeable battery systems for large-scale energy storage applications due to their advantages of high rates and long-term cycle lives. However, the development of cost-effective and low-temperature-tolerant hydrogen gas batteries is highly desirable yet very challenging. Herein, we report a novel conductive polymer-hydrogen gas battery that is suitable for ultralow-temperature energy storage applications and consists of a hydrogen gas anode, a conductive polymer cathode using polyaniline (PANI) or polypyrrole as examples, and protonic acidic electrolytes. The PANI-H2 battery using 1 M H2SO4 as the electrolyte exhibits a capacity of 67 mA h/g, a remarkable rate up to 15 A/g, a Coulombic efficiency around 100%, and an ultra-long life of 10,000 cycles. Using the anti-freezing 9 M H3PO4 electrolyte, the PANI-H2 battery can operate well at temperatures down to -70 °C, which maintains ∼70% of the capacity at room temperature and shows an excellent cycle stability under -60 °C. Benefiting from the fast redox kinetics of both electrodes, this work demonstrates excellent rate performance and low-temperature feasibility of conductive polymer-H2 batteries, providing a new avenue for further development of low-cost and reliable polymer-H2 batteries for large-scale energy storage.

pH-Universal Decoupled Water Electrolysis Enabled by Electrocatalytic Hydrogen Gas Capacitive Chemistry.

In conventional water electrolysis (CWE), the H2 and O2 evolution reactions (HER/OER) are tightly coupled, making the generated H2 and O2 difficult to separate, thus resulting in complex separation technology and potential safety issues. Previous efforts on the design of decoupled water electrolysis mainly concentrated on multi-electrode or multi-cell configurations; however, these strategies have the limitation of involving complicated operations. Here, we propose and demonstrate a pH-universal, two-electrode capacitive decoupled water electrolyzer (referred to as all-pH-CDWE) in a single-cell configuration by utilizing a low-cost capacitive electrode and a bifunctional HER/OER electrode to separate H2 and O2 generation for decoupling water electrolysis. In the all-pH-CDWE, high-purity H2 and O2 generation alternately occur at the electrocatalytic gas electrode only by reversing the current polarity. The designed all-pH-CDWE can maintain a continuous round-trip water electrolysis for over 800 consecutive cycles with an electrolyte utilization ratio of nearly 100%. As compared to CWE, the all-pH-CDWE achieves energy efficiencies of 94% in acidic electrolytes and 97% in alkaline electrolytes at a current density of 5 mA cm-2. Further, the designed all-pH-CDWE can be scaled up to a capacity of 720 C in a high current of 1 A for each cycle with a stable HER average voltage of 0.99 V. This work provides a new strategy toward the mass production of H2 in a facilely rechargeable process with high efficiency, good robustness, and large-scale applications.

Anions Regulation Engineering Enables a Highly Reversible and Dendrite-Free Nickel-Metal Anode with Ultrahigh Capacities.

The development of safe and high-energy metal anodes represents a crucial research direction. Here, the achievement of highly reversible, dendrite-free transition metal anodes with ultrahigh capacities by regulating aqueous electrolytes is reported. Using nickel (Ni) as a model, theoretical and experimental evidence demonstrating the beneficial role of chloride ions in inhibiting and disrupting the nickel hydroxide passivation layer on the Ni electrode is provided. As a result, Ni anodes with an ultrahigh areal capacity of 1000 mAh cm-2 (volumetric capacity of ≈6000 mAh cm-3 ), and a Coulombic efficiency of 99.4% on a carbon substrate, surpassing the state-of-the-art metal electrodes by approximately two orders of magnitude, are realized. Furthermore, as a proof-of-concept, a series of full cells based on the Ni anode is developed. The designed Ni-MnO2 full battery exhibits a long lifespan of 2000 cycles, while the Ni-PbO2 full battery achieves a high areal capacity of 200 mAh cm-2 . The findings of this study are important for enlightening a new arena toward the advancement of dendrite-free Ni-metal anodes with ultrahigh capacities and long cycle life for various energy-storage devices.

Ultrafast Electrical Pulse Synthesis of Highly Active Electrocatalysts for Beyond-Industrial-Level Hydrogen Gas Batteries.

The high reliability and proven ultra-longevity make aqueous hydrogen gas (H2 ) batteries ideal for large-scale energy storage. However, the low alkaline hydrogen evolution and oxidation reaction (HER/HOR) activities of expensive platinum catalysts severely hamper their widespread applications in H2 batteries. Here, cost-effective, highly active electrocatalysts, with a model of ruthenium-nickel alloy nanoparticles in ≈3 nm anchored on carbon black (RuNi/C) as an example, are developed by an ultrafast electrical pulse approach for nickel-hydrogen gas (NiH2 ) batteries. Having a competitive low cost of about one fifth of Pt/C benckmark, this ultrafine RuNi/C catalyst displays an ultrahigh HOR mass activity of 2.34 A mg-1 at 50 mV (vs RHE) and an ultralow HER overpotential of 19.5 mV at a current density of 10 mA cm-2 . As a result, the advanced NiH2 battery can efficiently operate under all-climate conditions (from -25 to +50 °C) with excellent durability. Notably, the NiH2 cell stack achieves an energy density up to 183 Wh kg-1 and an estimated cost of ≈49 $ kWh-1 under an ultrahigh cathode Ni(OH)2 loading of 280 mg cm-2 and a low anode Ru loading of ≈62.5 µg cm-2 . The advanced beyond-industrial-level hydrogen gas batteries provide great opportunities for practical grid-scale energy storage applications.

Solid-Liquid-Gas Management for Low-Cost Hydrogen Gas Batteries.

Aqueous nickel-hydrogen gas (Ni-H2) batteries with excellent durability (>10,000 cycles) are important candidates for grid-scale energy storage but are hampered by the high-cost Pt electrode with limited performance. Herein, we report a low-cost nickel-molybdenum (NiMo) alloy as an efficient bifunctional hydrogen evolution and oxidation reaction (HER/HOR) catalyst for Ni-H2 batteries in alkaline electrolytes. The NiMo alloy demonstrates a high HOR mass-specific kinetic current of 28.8 mA mg-1 at 50 mV as well as a low HER overpotential of 45 mV at a current density of 10 mA cm-2, which is better than most nonprecious metal catalysts. Furthermore, we apply a solid-liquid-gas management strategy to constitute a conductive, hydrophobic network of NiMo using multiwalled carbon nanotubes (NiMo-hydrophobic MWCNT) in the electrode to accelerate HER/HOR activities for much improved Ni-H2 battery performance. As a result, Ni-H2 cells based on the NiMo-hydrophobic MWCNT electrode show a high energy density of 118 Wh kg-1 and a low cost of only 67.5 $ kWh-1. With the low cost, high energy density, excellent durability, and improved energy efficiency, the Ni-H2 cells show great potential for practical grid-scale energy storage.

Aqueous Zinc-Chlorine Battery Modulated by a MnO2 Redox Adsorbent.

Aqueous zinc-chlorine battery with high discharge voltage and attractive theoretical energy density is expected to become an important technology for large-scale energy storage. However, the practical application of Zn-Cl2 batteries has been restricted due to the Cl2 cathode with sluggish kinetics and low Coulombic efficiency (CE). Here, an aqueous Zn-Cl2 battery using an inexpensive and effective MnO2 redox adsorbent (referred to Zn-Cl2 @MnO2 battery) to modulate the electrochemical performance of the Cl2 cathode is developed. Density functional theory calculations reveal that the existence of the intermediate state Clads free radical catalyzed by MnO2 on the Cl2 cathode contributes to the charge storage capacity, which is the key to modulate the electrode and improve the electrochemical performance. Further analysis of the Cl2 cathode kinetics discloses the adsorption and catalytic roles of the MnO2 redox adsorbent. The Zn-Cl2 @MnO2 battery displays an enhanced discharge voltage of 2.0 V at a current density of 2.5 mA cm-2 , and stable 1000 cycles with an average CE of 91.6%, much superior to the conventional Zn-Cl2 battery with an average CE of only 66.8%. The regulation strategy to the Cl2 cathode provides opportunities for the future development of aqueous Zn-Cl2 batteries.