CO2 Batteries Research Articles

Highly Surface‐Wrinkled and N‐Doped CNTs Anchored on Metal Wire: A Novel Fiber‐Shaped Cathode toward High‐Performance Flexible Li–CO2 Batteries

AbstractLi–CO2 batteries are regarded as a promising candidate for the next‐generation high‐performance electrochemical energy storage system owing to their ultrahigh theoretical energy density and environmentally friendly CO2 fixation ability. Until now, the majority of reported catalysts for Li–CO2 batteries are in the powder state. Thus, the air electrodes are produced in 2D rigid bulk structure and their electrochemical properties are negatively influenced by binder. The nondeformable feature and unsatisfactory performance of the cathode have already become the main obstacles that hinder Li–CO2 batteries toward ubiquity for wearable electronics. In this work, for the first time, a flexible hybrid fiber is reported comprising highly surface‐wrinkled and N‐doped carbon nanotube (CNT) networks anchored on metal wire as the cathode integrated with high performance and high flexibility for fiber‐shaped Li–CO2 battery. It exhibits a large discharge capacity as high as 9292.3 mAh g−1, an improved cycling performance of 45 cycles, and a decent rate capability. A quasi‐solid‐state flexible fiber‐shaped Li–CO2 battery is constructed to illustrate the advantages on mechanical flexibility of this fiber‐shaped cathode. Experiments and theoretical simulations prove that those doped pyridinic nitrogen atoms play a critical role in facilitating the kinetics of CO2 reduction and evolution reaction, thereby enabling distinctly enhanced electrochemical performance.

Drawing a Pencil‐Trace Cathode for a High‐Performance Polymer‐Based Li–CO2 Battery with Redox Mediator

AbstractLithium–carbon dioxide (Li–CO2) batteries have received wide attention due to their high theoretical energy density and CO2 capture capability. However, this system still faces poor cycling performance and huge overpotential, which stems from the leakage/volatilization of liquid electrolyte and instability of the cathode. A gel polymer electrolyte (GPE)‐based Li–CO2 battery by using a novel pencil‐trace cathode and 0.0025 mol L−1 (M) binuclear cobalt phthalocyanine (Bi‐CoPc)‐containing GPE (Bi‐CoPc‐GPE) is developed here. The cathode, which is prepared by pencil drawing on carbon paper, is stable because of its typical limited‐layered graphitic structure without any binder. In addition, Bi‐CoPc‐GPE, which consists of polymer matrix filled with liquid electrolyte, exhibits excellent ion conductivity (0.86 mS cm−1), effective protection for Li anode, and superior leakproof property. Moreover, Bi‐CoPc acts as a redox mediator to promote the decomposition of discharge products at low charge potential. Interestingly, different from polymer‐shaped discharge products formed in liquid electrolyte–based Li–CO2 batteries, the morphology of products in Li–CO2 batteries using Bi‐CoPc‐GPE is film‐like. Hence, this polymer‐based Li–CO2 battery shows super‐high discharge capacity, low overpotential, and even steadily runs for 120 cycles. This study may pave a new way to develop high‐performance Li–CO2 batteries.

Ru nanosheet catalyst supported by three-dimensional nickel foam as a binder-free cathode for Li–CO2 batteries

Due to the capability of CO2 uptake and the high theoretical energy density, Li–CO2 batteries have attracted a great deal of attention as a novel and promising energy storage system which is based on the reversible reaction between lithium and CO2. However, the insulating Li2CO3 formed upon the discharge process, which is difficult to be decomposed during recharge process due to the lack of effective cathode catalyst, leads to the poor cycling performance and huge overpotential of the Li–CO2 batteries. In this work, the Ru nanosheets were directly grown on one side of the three-dimensional nickel foam through a galvanic replacement reaction to form the Ru/Ni electrode, which was further used in the Li–CO2 batteries. The highly dispersed Ru nanosheets in the Ru/Ni cathode effectively promote the decomposition of discharge product Li2CO3 and thus reduce the charge overpotential. Moreover, the typical porous and binder-free Ru/Ni electrode not only has a sturdy construction to suppress the side reaction in the Li–CO2 batteries, but also enables the rapid permeation of CO2 and electrolyte/electron into the active sites of the Ru/Ni electrode. As a result, the Ru/Ni cathode-based Li–CO2 battery exhibits the superior discharge capacity (9502 mAh g−1), good coulombic efficiency (95.4%) and excellent rate performance (3177 mAh g−1 at 500 mA g−1) at the full discharge/charge condition. When operated at the limited capacity of 1000 mAh g−1, this cell can run for over 100 cycles with the charge potential below 4.1 V. The findings provide a snapshot towards improving the reversibility of Li–CO2 batteries by designing the binder-free stable cathodes.

Exploiting Synergistic Effect by Integrating Ruthenium–Copper Nanoparticles Highly Co‐Dispersed on Graphene as Efficient Air Cathodes for Li–CO2 Batteries

AbstractLi–CO2 batteries are attractive electrical energy storage devices; however, they still suffer from unsatisfactory electrochemical performance, and the kinetics of CO2 reduction and evolution reactions must be improved significantly. Herein, a composite of ruthenium–copper nanoparticles highly co‐dispersed on graphene (Ru–Cu–G) as efficient air cathodes for Li–CO2 batteries is designed. The Li–CO2 batteries with Ru–Cu–G cathodes exhibit ultra‐low overpotential and can be operated for 100 cycles with a fixed capacity of 1000 mAh g−1 at 200 and 400 mA g−1. The synergistic effect between Ru and Cu not only regulates the growth of discharge products, but also promotes CO2 reduction and evolution reactions by changing the electron cloud density of the surface between Ru and Cu. This work may provide new directions and strategies for developing highly efficient air cathodes for Li–CO2 batteries, or even practical Li–air batteries.

A long-life Li-CO2 battery employing a cathode catalyst of cobalt-embedded nitrogen-doped carbon nanotubes derived from a Prussian blue analogue.

A non-precious-metal catalyst, specifically made up of cobalt-embedded nitrogen-doped carbon nanotubes (Co-N-CNTs), was synthesized by subjecting a Prussian blue analogue to annealing decomposition. These Co-N-CNTs were employed as the cathode catalyst of a Li-CO2 battery, and helped this battery deliver a high capacity and outstanding cyclability. Furthermore, we verified the reversibility of this Li-CO2 battery.

Monodispersed MnO nanoparticles in graphene-an interconnected N-doped 3D carbon framework as a highly efficient gas cathode in Li–CO2 batteries

Monodispersed MnO nanoparticles in a 3D conductive carbon framework are designed as an effective cathode for a highly efficient, powerful and stable Li–CO2 battery.

Transient, in situ synthesis of ultrafine ruthenium nanoparticles for a high-rate Li–CO2 battery

Ultrafine Ru nanoparticles anchored on freestanding activated carbon nanofibers with porous structure are synthesized as a high performing cathode for Li–CO2 batteries via a transient, in situ thermal shock method.

Recent advances in understanding Li–CO2 electrochemistry

This review presents a comprehensive understanding of recent advances in Li–CO2 electrochemistry and aims to develop advanced Li–CO2 batteries.

Design strategies toward catalytic materials and cathode structures for emerging Li–CO2 batteries

The state-of-the-art design strategies toward highly active catalytic materials and cathode structures for Li–CO2 batteries are reviewed and discussed.

Frontispiece: Reversible Aqueous Zinc–CO2 Batteries Based on CO2–HCOOH Interconversion

Zinc–CO2 Batteries. A reversible aqueous Zn–CO2 battery is prepared by Y. Wang et al. in their Communication on page 16996 ff. 3D porous Pd interconnected nanosheets act as the cathode and electrocatalyze CO2 reduction and HCOOH oxidation.

Reversible Aqueous Zinc–CO2 Batteries Based on CO2–HCOOH Interconversion

AbstractAs a promising technique for CO2 fixation/utilization and energy conversion/storage, the metal–CO2 battery has been studied to improve its interconversion between CO2 and carbonates/oxalates. Herein, we propose and realize a reversible aqueous Zn–CO2 battery based on the reversible conversion between CO2 and liquid HCOOH on a bifunctional Pd cathode. The 3D porous Pd interconnected nanosheet with enriched edge and pore structure, has a highly electrochemical active surface to facilitate simultaneous selective CO2 reduction and HCOOH oxidation at low overpotentials. The resulting battery has a 1 V charge voltage, a cycling durability over 100 cycles, and a high energy efficiency of 81.2 %. The battery mechanism is proposed as Zn+CO2+2 H++2 OH−↔ ZnO+HCOOH+H2O, through which the reversible conversion between CO2 and liquid HCOOH was realized.

Assessing the Performance of Cobalt Phthalocyanine Nanoflakes as Molecular Catalysts for Li-Promoted Oxalate Formation in Li–CO2–Oxalate Batteries

Removal of O2 molecules from the cathode environment in the Li-based battery has led to introduction of the Li–CO2 battery as the novel and promising source of energy storage. In spite of CO2 capture through the reversible reaction between Li atoms and CO2 molecules at the cathode, the performance of the Li–CO2 battery is hampered by formation of the Li2CO3 insulating product in the discharge process and its difficult decomposition in the charging process. Hereby, we explore the possible improvement of the performance of the Li–CO2 battery through replacement of Li2CO3 by Li2C2O4 as the discharge product. This is achieved by systematic addition of Li and CO2 to a cobalt phthalocyanine (CoPc) nanoflake employed as the molecular catalyst in the cathode of the Li–CO2 battery by means of computational density functional theory-based methods. The present results predict high adsorption energy of the CO2 molecules (−2.16 eV), low Li-intercalation voltage (1.45 V), reveal the important and constructive influence...

Flexible and Tailorable Na−CO2 Batteries Based on an All‐Solid‐State Polymer Electrolyte

AbstractRechargeable Na< C‐>CO2 batteries coupling Na anodes with the greenhouse gas CO2 cathode are promising energy‐storage devices due to the high energy density, environmental friendliness and cost‐effectiveness. However, major challenges impeding the application of Na−CO2 batteries are safety concern regarding the leakage of flammable liquid electrolytes and the instability of the Na anodes. Herein, we construct all‐solid‐state flexible Na−CO2 batteries by designing an integrated structure built of a Na anode, poly(ethylene oxide)/NaClO4/SiO2 electrolyte and multiwall carbon nanotubes cathode. The batteries exhibit much improved safety and good cyclability (240 cycles with an overpotential increase of ∼0.4 V). Remarkably, we fabricated lab scale‐up integrated batteries (8×16 cm2), which display large capacity (450 mAh) and high energy density (173 Wh kg−1). Moreover, the integrated batteries show excellent bendability (≥1,000 times), foldability in individual shapes, as well as stable operation time (80 h) at bending states of 0° to 360°. Our work demonstrates a way to exploit flexible and safe solid‐state Na−CO2 batteries.

Tailoring the Discharge Reaction in Li-CO2 Batteries through Incorporation of CO2 Capture Chemistry

Summary The search for viable end-uses of CO2 has motivated considerable research into CO2 utilization in energy storage devices such as alkali metal-based O2/CO2 and -CO2 batteries. However, efforts have been stymied by the low electrochemical activity of CO2 in most organic media. In this work, we report a mediated CO2 capture and conversion process, based on amine (e.g., 2-ethoxyethylamine) chemisorption, which provides a new electrolyte system for facilitating the discharge reaction in Li-CO2 batteries. Our results indicate that electrochemical reduction of CO2-loaded amines proceeds at significantly higher discharge potentials (∼2.9 V versus Li/Li+) compared with physically dissolved CO2, which is inactive in the amine's absence. The discharge reaction forms solid-phase Li2CO3 as the primary discharge product and yields high discharge capacities (>1,000 mAh/gc), highlighting the coupling of CO2 capture chemistry to nonaqueous batteries as a promising approach for the design and manipulation of CO2 conversion reactions.

Progress and Future Perspectives on Li(Na)–CO2 Batteries

AbstractLi(Na)–CO2 batteries are attracting significant research attention due to contemporary energy and environmental issues. Li(Na)–CO2 batteries make possible the utilization of CO2 and open up a new avenue for energy conversion and storage. Research on this system is currently in its infancy, and its development is still faced with many challenges in terms of high charge potential, weak rate capability, and poor cyclability. Moreover, the reaction mechanism in the battery is still unclear and hard to determine, due to the generation of carbon along with metal carbonates on the cathode. In this review, the authors present the fundamentals and the latest progress related to Li(Na)–CO2 research. Detailed discussions are provided on the electrochemical reactions on cathode, cathode materials, and electrolytes. Current challenges and future perspectives on Li(Na)–CO2 batteries are also proposed.

Singlet Oxygen in Non-Aqueous Battery Chemistries

The redox chemistry of O2 moieties has come into the focus of much of the forefront battery research such as metal-O2 batteries and Li-rich layered oxides (1, 2). O2 evolution is in either case a critical yet not fully understood phenomenon (1, 3). For example, operation of the rechargeable metal-O2 batteries depends crucially on the reversible formation/decomposition of metal (su)peroxides at the cathode on discharge/charge. The greatest challenge facing progress arises from severe parasitic reactions that decompose the electrolyte as well as the porous electrode. These processes have serious consequences. So far these parasitic reactions have been ascribed to the reactivity of superoxide and peroxide. Yet, their reactivity cannot consistently explain the observed irreversible processes. Unsurprisingly, strategies to mitigate the irreversibilities proved only partially successful. Therefore, only better knowledge of parasitic reactions may allow them to be inhibited. Here we discuss our recent insights into irreversible parasitic reactions caused by the highly reactive singlet oxygen (1O2) during cycling of non-aqueous batteries that have so far been overlooked. They account for the majority of the parasitic products on discharge and nearly all on charge in Li-O2 and Na-O2 cells (4-6). Moreover, singlet oxygen forms upon oxidizing Li2CO3 above 3.8 V vs Li/Li+ (7). Li2CO3 is a universal passivating agent in Li-ion battery cathodes and decisive in interfacial reactivity. It is also a common side product in Li-O2 cathodes, as well as the targeted discharge product in Li-O2/CO2 batteries. We will further discuss work on open question with respect to 1O2 non-aqueous battery chemistries such as catalysts, electrolytes, mediators, quenchers and other additives as well as the formation mechanism and the implications for metal-O2 cells and intercalation chemistries. Awareness of the highly reactive singlet oxygen gives a rationale for future research towards achieving highly reversible cell operation in a broad range of cell chemistries. References(1) Bruce, P. G.; Freunberger, S. A.; Hardwick, L. J.; Tarascon, J.-M. Nature Mater. 2012, 11, 19. (2) McCalla, E. et al.. Science 2015, 350, 1516. (3) Luo, K; et al. JACS 2016, 138, 11211 (4) Mahne, N., et al. Nature Energy 2017 , 17036. (5) L. Schafzahl, et al, Angew. Chem. Int. Ed., 2017, 56, 15728. (6) N. Mahne, O. Fontaine, M. Thotiyl, M. Wilkening & S. A. Freunberger, Chem. Sci., 2017, 8, 6716. (7) N. Mahne, S.E. Renfrew, B.D. McCloskey & S.A. Freunberger, Angew. Chem. Int. Ed., doi: 10.1002/anie.201802277.

Polymer electrolyte with composite cathode for solid-state Li–CO2 battery

The rechargeable Li–CO2 battery has attracted much attention for energy storage because of the high energy density and efficient utilization of greenhouse gas. However, it’s still suffered by low safety issue of liquid electrolyte. Herein, a composite cathode consisting of CNTs and polymer electrolytes was fabricated by the in-situ polymerization process for the polymer electrolyte-based solid-state Li–CO2 batteries. With the good dispersion of CNTs and polymer electrolyte, the composite cathode is covered by film-like discharge products Li2CO3. Furthermore, the Li–CO2 battery shows high reversible capacity (~ 11,000 mAh·g−1), excellent cycle stability (1000 mAh·g−1 for 100 cycles) under low charge potential (< 4.5 V), and outstanding rate performances at room temperature, which are much better than those of liquid electrolyte-based battery. Therefore, the polymer electrolyte-based Li–CO2 battery prepared by this strategy can be a promising candidate to meet the demands of high safety and high-performance energy storage devices.

Electrochemical Oxidation of Lithium Carbonate Generates Singlet Oxygen.

Solid alkali metal carbonates are universal passivation layer components of intercalation battery materials and common side products in metal‐O2 batteries, and are believed to form and decompose reversibly in metal‐O2/CO2 cells. In these cathodes, Li2CO3 decomposes to CO2 when exposed to potentials above 3.8 V vs. Li/Li+. However, O2 evolution, as would be expected according to the decomposition reaction 2 Li2CO3→4 Li++4 e−+2 CO2+O2, is not detected. O atoms are thus unaccounted for, which was previously ascribed to unidentified parasitic reactions. Here, we show that highly reactive singlet oxygen (1O2) forms upon oxidizing Li2CO3 in an aprotic electrolyte and therefore does not evolve as O2. These results have substantial implications for the long‐term cyclability of batteries: they underpin the importance of avoiding 1O2 in metal‐O2 batteries, question the possibility of a reversible metal‐O2/CO2 battery based on a carbonate discharge product, and help explain the interfacial reactivity of transition‐metal cathodes with residual Li2CO3.

Electrochemical Reduction of CO2 Mediated by Quinone Derivatives: Implication for Li–CO2 Battery

The pivotal role of CO2 played in global temperature cycles has motivated the ongoing research on carbon capture and storage (CCS). Within this context, Li–CO2 battery, alike the configuration of Li–O2 battery, has been proposed as a novel energy storage device with the potential to reduce CO2. Nevertheless, the highly negative potential required for the electrochemical reduction of CO2 adds difficulty to the achievement of energy efficient Li–CO2 battery. Facilitating the electron transfer to this inert molecule, which largely dictates the discharge voltage and rate capability of a Li–CO2 battery, is therefore necessary. Herein, three types of quinones have been surveyed, aiming to mediate the reduction of CO2, which is expected to result in lower overpotential than with a direct electron transfer. We demonstrate by cyclic voltammetry that, in the presence of quinones, CO2 reduction proceeds through an intermolecular interaction between CO2 and quinone dianion. Importantly, such catalytic CO2 reduction r...

A porous Zn cathode for Li–CO2 batteries generating fuel-gas CO

A porous fractal Zn cathode with high electrocatalytic activity and selectivity to CO2-to-CO conversion enables Li–CO2 batteries that produce fuel gas CO.