Anion Storage Research Articles

Mesoporous vanadium nitride as anion storage electrode for reverse dual-ion hybrid supercapacitor

SummaryIn traditional dual-ion systems, the cathode usually is employed as anion-storage materials. Herein, we propose a new dual-ion hybrid supercapacitor with reverse anion/cation-storage mechanism, consisting of a mesoporous (MPs) VN anode as a pivotal anion-storage material and K2-xMn8O16 nanosheet arrays grown on carbon cloth (NSs/CC) as (K-storage) cathode. During charge/discharge, the anode and cathode reversibly store/release OH− ions and K+ ions, respectively. Herein, the MPs VN as anion-storage electrode can operate in an alkaline condition and deliver a high capacitance of 251 mF cm−2 with desired low-voltage plateau. More importantly, benefiting from unique reverse dual-ion mechanism, the (MPs VN-K2-xMn8O16 NSs/CC) hybrid device displays excellent rate performance and satisfying area capacitance along with good durability of 92.2% after 10,000 cycles at a scan rate of 100 mV s−1. It offers new ideas to expand the range of anion-storage materials in dual-ion hybrid supercapacitors.

The potential for phosphorus loss to groundwater from soils irrigated with dairy factory wastewater

ABSTRACT Soils irrigated with phosphorus (P)-rich wastewater can increase the risk of P losses from land to water. We investigated if wastewater-irrigated soils can leach P through the soil profile and enrich groundwater. Soils were sampled annually for 20 years to 7.5 cm depth and for one year to 2.2 and 15 m. A mass balance showed that topsoils >200 mg L−1 Olsen P (and <50% anion storage capacity, ASC) were no longer accumulating P and had very high concentrations of water and CaCl2-extractable P (designed to indicate loss to runoff and leaching, respectively). Samples in five paddocks showed substantial P leaching to 2.2 m, while sampling to 15 m showed leaching to 4.5 m depth. Deeper layers, especially in the 15 m deep cores, had a coarse texture and low capacity to sorb P, which caused high P concentrations (1.9 mg L−1) at one groundwater site. Based on these data preventing soils from reaching the thresholds of 200 mg L−1 Olsen P and 50% ASC is necessary to prevent excessive P losses.

Mesoporous and defective activated carbon cathode for AlCl4− anion storage in non-aqueous aluminium-ion batteries

Most commercial rechargeable battery types suffer from several drawbacks, including high cost, toxic and hazardous materials, poor performance and general non-sustainability. Aluminium-ion batteries (AIBs), with aluminium as the most common metal in the Earth's crust, can theoretically overcome almost all these shortcomings. However, the intercalation of large-sized chloroaluminate (AlCl4−) active ions into a host cathode, such as graphite, leads to poor capacity with volume expansion restricting practical applications. Finding a suitable cathode material for such large anions is a great challenge. We demonstrate a highly porous activated carbon derived from coconut shell chars as a promising cathode material. Activated carbon possesses a high mesoporosity and defect concentration with a specific area of 2686 m2 g−1. Its high surface area along with a great degree of mesoporosity and defects, activated carbon provides sufficient space and efficient transport channels for these active ions. Activated carbon cathodes show a specific discharge capacity of 150 mAh g−1 at 0.1 A g−1 with a good rate capability and cycling stability over 1500 cycles at 1 A g−1. This work illustrates that the mesoporosity and defect structures in this low-cost carbon material allow good AlCl4− anion storage capability, which supports the design principles for electrode materials storing large ion species.

High‐performance Li‐ion capacitor via anion‐intercalation process

AbstractSupercapacitors are characterized by their fast charge/discharge capability, high‐power capability, and long cycle life, but low‐energy‐density impedes their practical application. The requirement of achieving a highly efficient energy storage system demands the hybridization of supercapacitors and batteries. The anion‐intercalation chemistry of graphite with high insertion potential creates a possibility of using graphite as a cathode, which works as an acceptor‐type graphite intercalation compound. Herein, we report the reversible PF6– anion storage on the graphite cathode, which occurs by the combination of pseudocapacitive and diffusion‐limited redox reaction at a higher working potential. Furthermore, a dual carbon lithium‐ion capacitor (LIC) using commercial graphite as anion‐intercalation type, battery type cathode, and commercial‐activated carbon (AC) as supercapacitor type anode is designed. The assembled preanion intercalated Graphite/AC‐based LIC assembly displayed a high‐energy density of 90.73 Wh kg–1. Moreover, the device with low‐temperature stability is advantageous over traditional electrical double‐layer capacitors, mainly in terms of its energy and low cost with much more safety features than commercial lithium‐ion batteries.

A unique co-recovery strategy of cathode and anode from spent LiFePO4 battery

Along with the explosive growth in the market of new energy electric vehicles, the demand for Li-ion batteries (LIBs) has correspondingly expanded. Given the limited life of LIBs, numbers of spent LIBs are bound to be produced. Because of the severe threats and challenges of spent LIBs to the environment, resources, and global sustainable development, the recycling and reuse of spent LIBs have become urgent. Herein, we propose a novel green and efficient direct recycling method, which realizes the concurrent reuse of LiFePO4 (LFP) cathode and graphite anode from spent LFP batteries. By optimizing the proportion of LFP and graphite, a hybrid LFP/graphite (LFPG) cathode was designed for a new type of dualion battery (DIB) that can achieve co-participation in the storage of both anions and cations. The hybrid LFPG cathode combines the excellent stability of LFP and the high conductivity of graphite to exhibit an extraordinary electrochemical performance. The best compound, i.e., LFP:graphite = 3:1, with the highest reversible capacity (∼130 mA h g−1 at 25 mA g−1), high voltage platform of 4.95 V, and outstanding cycle performance, was achieved. The specific diffusion behavior of Li+ and PF6− in the hybrid cathode was studied using electrode kinetic tests, further clarifying the working mechanism of DIBs. This study provides a new strategy toward the large-scale recycling of positive and negative electrodes of spent LIBs and establishes a precedent for designing new hybrid cathode materials for DIBs with superior performance using spent LIBs.

A Desolvation-Free Sodium Dual-Ion Chemistry for High Power Density and Extremely Low Temperature.

The development of conventional rechargeable batteries based on intercalation chemistry in the fields of fast charge and low temperature is generally hindered by the sluggish cation-desolvation process at the electrolyte/electrode interphase. To address this issue, a novel desolvation-free sodium dual-ion battery (SDIB) has been proposed by using artificial graphite (AG) as anode and polytriphenylamine (PTPAn) as cathode. Combining the cation solvent co-intercalation and anion storage chemistry, such a SDIB operated with ether-based electrolyte can intrinsically eliminate the sluggish desolvation process. Hence, it can exhibit an extremely fast kinetics of 10 Ag-1 (corresponding to 100C-rate) with a high capacity retention of 45 %. Moreover, the desolvation-free mechanism endows the battery with 61 % of its room-temperature capacity at an ultra-low temperature of -70 °C. This advanced battery system will open a door for designing energy storage devices that require high power density and a wide operational temperature range.

A Desolvation‐Free Sodium Dual‐Ion Chemistry for High Power Density and Extremely Low Temperature

AbstractThe development of conventional rechargeable batteries based on intercalation chemistry in the fields of fast charge and low temperature is generally hindered by the sluggish cation‐desolvation process at the electrolyte/electrode interphase. To address this issue, a novel desolvation‐free sodium dual‐ion battery (SDIB) has been proposed by using artificial graphite (AG) as anode and polytriphenylamine (PTPAn) as cathode. Combining the cation solvent co‐intercalation and anion storage chemistry, such a SDIB operated with ether‐based electrolyte can intrinsically eliminate the sluggish desolvation process. Hence, it can exhibit an extremely fast kinetics of 10 Ag−1 (corresponding to 100C‐rate) with a high capacity retention of 45 %. Moreover, the desolvation‐free mechanism endows the battery with 61 % of its room‐temperature capacity at an ultra‐low temperature of −70 °C. This advanced battery system will open a door for designing energy storage devices that require high power density and a wide operational temperature range.

Hexafluorophosphate Anion Intercalation into Graphite Electrodes from Propylene Carbonate/Gamma-Butyrolactone Solutions.

The PF6- intercalation behavior of graphite positive electrodes has been investigated in the solutions of 1 M LiPF6-propylene carbonate (PC)/gamma-butyrolactone (GBL). Conventional electrochemical tests including galvanostatic charge-discharge and cyclic voltammetry are conducted on Li/graphite cells to assess the anion storage capability of the graphite electrode in these solutions. We find an abnormal undulation of capacity with the rise in GBL content. Ex situ and in situ X-ray diffraction (XRD) measurements are performed on graphite electrodes to identify the co-intercalating solvents and stage transitions. The intercalation of the anion cosolvated by both GBL and PC into the graphite electrode has been discovered at low GBL contents. Infrared (IR) spectroscopy and nuclear magnetic resonance (NMR) spectroscopic studies on the solutions are carried out to evaluate interactions between ions and solvents inside. The intercalation behavior of the anion in the graphite electrode is correlated with the solvation environments of the solution.

A sustainable LiFePO4/graphite hybrid cathode capable of stepwise cation and anion storage

Dual ion battery (DIB) with graphite cathode is a renewable energy storage system but suffers from low capacity. Addition of lithium ion battery (LIB) cathode to graphite cathode not only facilitates capacity increment but also serves as proof-of-concept for LIB-DIB hybridization. In this study, a hybrid cathode, incorporating a physical mixture of high working potential graphite and nontoxic lithium iron phosphate (LiFePO4, LFP), is proposed and examined. The graphite interacts with anion and works as electrically conductive matrix. While additive LFP is active to cation, serving as capacity facilitator. Characterization results reveal that, during charging, the hybrid cathode starts with LFP delithiation in lower voltage region and finishes with anion intercalation in graphite at higher voltage region. During discharging, processes are reversed with stepwise anion deintercalation and cation insertion, without interfering individual constituent's proper functioning. The transfer of two polarity distinct ions inside the hybrid cathode maintains high independence, without any added kinetical difficulties. Such hybrid cathode is demonstrated to work stably with varied LFP-graphite proportions. The addition of 40 wt% LFP to graphite cathode shows doubled capacity and excellent long-term cyclability. And the hybrid cathode is also cyclable in a full cell configuration.

Successive Storage of Cations and Anions by Ligands of π–d‐Conjugated Coordination Polymers Enabling Robust Sodium‐Ion Batteries

AbstractThe oxidation of π–d‐conjugated coordination polymers (CCPs) accompanied with anion insertion has the merits of increasing the capacity and elevating the discharge voltages. However, previous reports on this mechanism either required more investigations or showed low capacity and poor cyclablity. Herein, triphenylene‐catecholate‐based two‐dimensional CCPs are constructed by employing inactive transition‐metal ions (Zn2+) as nodes, forming Zn‐HHTP. Substantial characterizations and theoretical calculations indicate the successive storage of cations and anions by redox reactions of only ligands, leading to a high reversible capacity of ≈150 mAh g−1 at 100 mA g−1 and a remarkable capacity retention of 90 % after 1000 cycles. On the contrary, as a control experiment, the analogous CCPs (Cu‐HHTP) with Cu2+ nodes, where both ligands and metal ions undergo redox reactions, accompanied by the storage of only Na+ cations, show a much poorer cyclability. These results highlight the importance of redox reactions of only ligands for long‐term cycle life and the insight into the storage mechanisms deepens our understanding on CCPs for the further design of CCPs with high performance.

Successive Storage of Cations and Anions by Ligands of π-d-Conjugated Coordination Polymers Enabling Robust Sodium-Ion Batteries.

The oxidation of π-d-conjugated coordination polymers (CCPs) accompanied with anion insertion has the merits of increasing the capacity and elevating the discharge voltages. However, previous reports on this mechanism either required more investigations or showed low capacity and poor cyclablity. Herein, triphenylene-catecholate-based two-dimensional CCPs are constructed by employing inactive transition-metal ions (Zn2+ ) as nodes, forming Zn-HHTP. Substantial characterizations and theoretical calculations indicate the successive storage of cations and anions by redox reactions of only ligands, leading to a high reversible capacity of ≈150 mAh g-1 at 100 mA g-1 and a remarkable capacity retention of 90 % after 1000 cycles. On the contrary, as a control experiment, the analogous CCPs (Cu-HHTP) with Cu2+ nodes, where both ligands and metal ions undergo redox reactions, accompanied by the storage of only Na+ cations, show a much poorer cyclability. These results highlight the importance of redox reactions of only ligands for long-term cycle life and the insight into the storage mechanisms deepens our understanding on CCPs for the further design of CCPs with high performance.

A COF-Like N-Rich Conjugated Microporous Polytriphenylamine Cathode with Pseudocapacitive Anion Storage Behavior for High-Energy Aqueous Zinc Dual-Ion Batteries.

Conducting polymers with good electron conductivity and rich redox functional groups are promising cathode candidates for constructing high-energy aqueous zinc batteries. However, the glaring flaw of active-site underutilization impairs their electrochemical performance. Herein, wereport a poriferous polytriphenylamine conjugated microporous polymer (CMP) cathode capable of accommodating Cl- anions in a pseudocapative-dominated manner for energy storage. Its specific 3D, covalent-organic-framework-like conjugated network ensures high accessibility efficacy of N active sites (up to 83.2% at 0.5 A g-1 ) and distinct physicochemical stability (87.6% capacity retention after 1000 cycles) during repeated charging/discharging courses. Such a robust CMP electrode also leads to a zinc dual-ion battery device with a high energy density of 236 W h kg-1 and a maximum power density of 6.8kW kg-1 , substantially surpassing most recently reported organic-based zinc batteries. This study paves the way for the rational design of advanced CMP-based organic cathodes for high-energy devices.

Dual-Redox-Sites Enable Two-Dimensional Conjugated Metal-Organic Frameworks with Large Pseudocapacitance and Wide Potential Window.

Advanced supercapacitor electrodes require the development of materials with dense redox sites embedded into conductive and porous skeletons. Two-dimensional (2D) conjugated metal-organic frameworks (c-MOFs) are attractive supercapacitor electrode materials due to their high intrinsic electrical conductivities, large specific surface areas, and quasi-one-dimensional aligned pore arrays. However, the reported 2D c-MOFs still suffer from unsatisfying specific capacitances and narrow potential windows because large and redox-inactive building blocks lead to low redox-site densities of 2D c-MOFs. Herein, we demonstrate the dual-redox-site 2D c-MOFs with copper phthalocyanine building blocks linked by metal-bis(iminobenzosemiquinoid) (M2[CuPc(NH)8], M = Ni or Cu), which depict both large specific capacitances and wide potential windows. Experimental results accompanied by theoretical calculations verify that phthalocyanine monomers and metal-bis(iminobenzosemiquinoid) linkages serve as respective redox sites for pseudocapacitive cation (Na+) and anion (SO42-) storage, enabling the continuous Faradaic reactions of M2[CuPc(NH)8] occurring in a large potential window of -0.8 to 0.8 V vs Ag/AgCl (3 M KCl). The decent conductivity (0.8 S m-1) and high active-site density further endow the Ni2[CuPc(NH)8] with a remarkable specific capacitance (400 F g-1 at 0.5 A g-1) and excellent rate capability (183 F g-1 at 20 A g-1). Quasi-solid-state symmetric supercapacitors are further assembled to demonstrate the practical application of Ni2[CuPc(NH)8] electrode, which deliver a state-of-the-art energy density of 51.6 Wh kg-1 and a peak power density of 32.1 kW kg-1.

Ultrafast and reversible anion storage of spinel nanoarchitecture for high-performance alkaline zinc full cells

Rechargeable alkaline zinc batteries are considered to be potential energy-storage systems owing to their natural abundance, low toxicity, and high capacity. However, their performance and efficiency are limited by the sluggish kinetics and irreversibility of the anode and cathode. In particular, high-capacity binary transition metal-based spinel materials that can store OH− anions are expected to replace commercial MnO cathodes owing to their abundant active sites of two or more transition metals. Herein, we report an ultrafast and reversible anion storage mechanism of spinel NiCo2O4 nanoarchitectures decorated onto N-doped reduced graphene oxide (NCO@N-rGO) for high-performance rechargeable alkaline zinc full cells. The NCO@N-rGO electrode exhibits high specific and rate capacities of 191 mA h g−1 at 1000 mA g−1 and 151 mA h g−1 even at 20 000 mA g−1, respectively, much higher than those of NCO@rGO and NCO. The as-designed cells achieve a record-high volumetric power density (7.20 W cm−3) among alkaline zinc full cells, along with a high energy density (14.93 mW h cm−3) and a capacity retention of 77% over 3000 cycles at 6000 mA g−1. These results are attributed to the facile charge-storage kinetics of the spinel framework, multiple Ni3+/Ni2+ and Co3+/Co2+ redox couples with OH−, and structural integrity of N-rGO as verified by electrochemical, ex situ XRD and XPS, and postmortem analyses. This work proposes a rational design of nanoarchitectured electrode materials for high volumetric performances and long-cycle life of rechargeable alkaline zinc batteries.

Hexafluorophosphate Intercalation into the Graphite Electrode from Mixed Cyclic Carbonates

The storage of anions in the graphite electrode depends upon the composition of electrolyte solutions. LiPF6 and cyclic carbonates are the most common components of nonaqueous electrolyte solutions...

Hexafluorophosphate intercalation into graphite electrode from propylene carbonate/methyl acetate solutions

The electrolyte solutions based on binary solvent mixtures have shown considerable promise in dual-ion batteries. In order to make the best use of advantages of both propylene carbonate (PC) and methyl acetate (MA), LiPF6-PC and MA solutions are mixed together to pursue an optimized performance of anion storage in graphite electrode. The electrochemical behavior of PF6– storage in graphite has been studied in 1 M LiPF6 PC/MA solutions by galvanostatic charge-discharge test, in-situ or ex-situ measurements. On the other hand, the solutions have been characterized by FTIR and NMR to assess the interactions between ions and solvents. The underlying mechanisms have been explored.

A Review of Emerging Dual‐Ion Batteries: Fundamentals and Recent Advances

AbstractDual‐ion batteries (DIBs), based on the working mechanism involving the storage of cations and anions separately in the anode and cathode during the charging/discharging process, are of great interest beyond lithium‐ion batteries (LIBs) in high‐efficiency energy storage due to the merits of high working voltage, material availability, as well as low cost and excellent safety. Despite the progress achieved, the practical applications of DIBs are still hindered by negative issues, such as limited capacity and cyclic stability, which triggers the development of suitable electrode materials with highly reversible capacities, and corresponding electrolytes with high oxidative stability as well as sufficient reaction kinetics of active ions. Herein, in this article, a systematic and comprehensive review of fundamentals and recent advances in current DIBs with subcategories of cathode materials, anode materials, and electrolytes are presented. In particular, their energy storage mechanisms, as well as their respective features, are dissected. Furthermore, some strategies and perspectives are proposed for facilitating the further development of DIBs in the future.

Tetrafluoroborate Anion Intercalation into Graphite Electrode from Sulfolane

Electrolyte solutions of lithium tetrafluoroborate dissolved in sulfolane are applied in dual-ion batteries. A graphite positive electrode in this kind of solutions delivers a reversible anion storage capacity over 80 mAh g−1 at potentials over 4.5 V vs. Li/Li+. The structures of anion-graphite intercalation compounds are investigated in detail by the combination of in situ X-ray diffraction (XRD) and in situ Raman spectroscopic measurements.

Locally Ordered Graphitized Carbon Cathodes for High-Capacity Dual-Ion Batteries.

Dual-ion batteries (DIBs) inherently suffer from limited energy density. Proposed here is a strategy to effectively tackle this issue by employing locally ordered graphitized carbon (LOGC) cathodes. Quantum mechanical modeling suggests that strong anion-anion repulsions and severe expansion at the deep-charging stage raise the anion intercalation voltage, therefore only part of the theoretical anion storage sites in graphite is accessible. The LOGC interconnected with disordered carbon is predicted to weaken the interlaminar van der Waals interactions, while disordered carbons not only interconnect the dispersed nanographite but also partially buffer severe anion-anion repulsion and offer extra capacitive anion storage sites. As a proof-of-concept, ketjen black (KB) with LOGC was used as a model cathode for a potassium-based DIB (KDIB). The KDIB delivers an unprecedentedly high specific capacity of 232 mAh g-1 at 50 mA g-1 , a good rate capability of 110 mAh g-1 at 2000 mA g-1 , and excellent cycling stability of 1000 cycles without obvious capacity fading.

Locally Ordered Graphitized Carbon Cathodes for High‐Capacity Dual‐Ion Batteries

AbstractDual‐ion batteries (DIBs) inherently suffer from limited energy density. Proposed here is a strategy to effectively tackle this issue by employing locally ordered graphitized carbon (LOGC) cathodes. Quantum mechanical modeling suggests that strong anion–anion repulsions and severe expansion at the deep‐charging stage raise the anion intercalation voltage, therefore only part of the theoretical anion storage sites in graphite is accessible. The LOGC interconnected with disordered carbon is predicted to weaken the interlaminar van der Waals interactions, while disordered carbons not only interconnect the dispersed nanographite but also partially buffer severe anion–anion repulsion and offer extra capacitive anion storage sites. As a proof‐of‐concept, ketjen black (KB) with LOGC was used as a model cathode for a potassium‐based DIB (KDIB). The KDIB delivers an unprecedentedly high specific capacity of 232 mAh g−1 at 50 mA g−1, a good rate capability of 110 mAh g−1 at 2000 mA g−1, and excellent cycling stability of 1000 cycles without obvious capacity fading.