Intercalation Capacity Research Articles

Mn2+ Ions Confined by Electrode Microskin for Aqueous Battery beyond Intercalation Capacity

AbstractIn aqueous rechargeable zinc–manganese dioxide batteries (ZMBs), some irreversible side reactions, such as Mn2+ dissolution, often lead to capacity fading over cycling. These side reactions play a crucial role in the capacity and cycle performance of the battery. The implementation of a bionic electrode microskin (EMS) composed of collagen hydrolysate to convert the irreversible side reactions into reversible reactions is reported. The proposed EMS effectively adsorbs and confines the Mn2+ ions around the cathode through van der Waals forces, hydrogen bonds, and/or ionic interactions, which makes the MnO2/Mn2+ reactions reversible during the charge/discharge process. Such Mn2+ dissolution reactions, with an ultrahigh theoretical capacity (617 mAh g‐1), contribute a large amount of capacity, ≈44% of the total specific capacity at a low scan rate. Based on these fundamental findings, the assembled ZMBs with an EMS display an unprecedented discharge capacity of 415 mAh g‐1 at 20 mA g‐1, which overcomes the theoretical capacity (308 mAh g‐1) limitation of the Zn2+ intercalation mechanism. More significantly, the EMS on all α‐, β‐, and γ‐MnO2 cathodes exhibits similar high capacity beyond the theoretical capacity of Zn intercalation and capacity retention enhancement after 3000 cycles.

Rational Route for Increasing Intercalation Capacity of Hard Carbons as Sodium-Ion Battery Anodes.

Hard carbon (HC) is the most promising candidate for sodium-ion battery anode materials. Several material properties such as intensity ratio of the Raman spectrum, lateral size of HC crystallite (La ), and interlayer distance (d002 ) have been discussed as factors affecting anode performance. However, these factors do not reflect the bulk property of the Na+ intercalation reaction directly, since Raman analysis has high surface sensitivity and La and d002 provide only one-dimensional crystalline information. Herein, it was proposed that the crystallite interlayer area (Ai ) defined using La , d002 , and stacking height (Lc ) governs Na+ intercalation behavior of various HCs. It was revealed that various wood-derived HCs exhibited the similar total capacity of approximately 250 mAh g-1 , whereas the Na+ intercalation capacity (Ci ) was proportional to Ai with the correlation coefficient of R2 =0.94. The evaluation factor of Ai was also adaptable to previous reports and strongly correlated with their Ci , indicating that Ai is more widely adaptable than the conventional evaluation methods.

Controlling at Elevated Temperature the Sodium Intercalation Capacity and Rate Capability of P3‐Na2/3Ni1/2Mn1/2O2 through the Selective Substitution of Nickel with Magnesium

AbstractThe integration of sodium‐ion batteries into large‐scale energy storage systems will become feasible in the case when their performance becomes less sensitive towards ambient temperature. Herein, we demonstrate the elaboration of the oxide‐based electrode material with an optimized layered structure and composition that is designed to work at elevated temperatures. Through selective substitution of Mg2+ ions for Ni2+ in the three‐layered oxide, P3‐Na2/3Ni1/2Mn1/2O2, the oxidation state of Ni ions, the cationic distribution in the layers, the sodium intercalation capacity, and the rate capability is manipulated. The electrochemical behavior of P3‐Na2/3Ni1/3Mg1/6Mn1/2O2 is discussed on the basis of ex situ diffraction as well as microscopic and spectroscopic methods in terms of redox activity of the lattice oxygen, the reversible transfer of Mg2+ and Ni2+ ions between layers during Na+ intercalation, thermal stability of cycled electrodes, and surface reactivity of the layered oxide towards the ionic liquid (IL) electrolyte. At 40 °C, the rate capability of the oxide is improved upon using an IL electrolyte rather than the carbonate‐based electrolyte.

Highly Concentrated Electrolyte towards Enhanced Energy Density and Cycling Life of Dual‐Ion Battery

AbstractDual‐ion batteries (DIBs) have attracted much attention owing to their low cost, high voltage, and environmental friendliness. As the source of active ions during the charging/discharging process, the electrolyte plays a critical role in the performance of DIBs, including capacity, energy density, and cycling life. However, most used electrolyte systems based on the LiPF6 salt demonstrate unsatisfactory performance in DIBs. We have successfully developed a 7.5 mol kg−1 lithium bis(fluorosulfonyl)imide (LiFSI) in a carbonate electrolyte system. Compared with diluted electrolytes, this highly concentrated electrolyte exhibits several advantages: 1) enhanced intercalation capacity and cycling stability of the graphite cathode, 2) optimized structural stability of the Al anode, and 3) significantly increased battery energy density. A proof‐of‐concept DIB based on this concentrated electrolyte exhibits a discharge capacity of 94.0 mAh g−1 at 200 mA g−1 and 96.8 % capacity retention after 500 cycles. By counting both the electrode materials and electrolyte, the energy density of this DIB reaches up to ≈180 Wh kg−1, which is among the best performances of DIBs reported to date.

Graphdiyne and Hydrogen-Substituted Graphdiyne as Potential Cathode Materials for High-Capacity Aluminum-Ion Batteries

In chloroaluminate ion based aluminum-ion batteries, a graphite cathode shows promising electrochemical performance. However, its low capacity and high volume expansion is a major hindrance. This is because of the limited intercalation of the AlCl4- ion into the graphite layers. As a possible solution to this, graphdiyne (GDY) and hydrogen-substituted graphdiyne (HsGDY), two-dimensional carbon allotropes with large pores, are tested here as potential cathode materials by density functional theory calculations. We find that both materials exhibit better performance than graphite, in terms of easiness of AlCl4 intercalation, voltage profile, and storage capacity. To ensure AlCl4 intercalation during charging, the cathode materials must expand to accommodate the AlCl4. The energy required for the expansion is defined as the distortion energy. Both GDY and HsGDY require a lower distortion energy (0.006 and 0.003 eV/angstrom(2), respectively) than graphite (0.014 eV/angstrom(2)) meaning it will be easier for the AlCl4 to intercalate into the cathode during charging. The average voltage for the AlCl4 intercalated single layer of GDY and HsGDY is around 2.15 V, which is higher than that of graphite (2 V). Finally, the storage capacity of the bilayer system of GDY and HsGDY based on stage-1 storage (AlCl4 intercalation between every layer of the cathode material) is 124 and 456 mA h g(-1), respectively; whereas a bilayer graphene system has a capacity of 155 mA h g(-1). Therefore, HsGDY has a significantly higher storage capacity than graphite.

Understanding mesopore volume-enhanced extra-capacity: Optimizing mesoporous carbon for high-rate and long-life potassium-storage

The relationship between pore volume within pore structure and electrochemical performance is rarely studied, especially for potassium-ion batteries (PIBs). Herein, a series of porous carbon (MPC-Ts) with various pore structures including surface area, pore size and pore volume are fabricated in the closed autoclave by regulating the pressure medium and carbonization temperature. Combined with structural characterization, ex situ tests, electrochemical measurements and DFT calculations, it is demonstrated that the intercalation capacity is positively correlated with IG/ID ratio rather than interlayer distance, and adsorption capacity is positively correlated with mesopore volume rather than surface area or pore size. Mesopores can not only serve as active sites for potassium ion storage with low potential plateau but also promote ions migration and accommodate the huge volume expansion during (de)potassiation process. As a result, the optimized sample (APC-700) with the largest mesopore volume and appropriate surface area exhibits a high capacity of 633.2 ​mA ​h ​g−1 at 50 ​mA ​g−1, and maintains a reversible capacity of 263.9 ​mA ​h ​g−1 at 1000 ​mA ​g−1 after 1000 cycles. Even at 2000 ​mA ​g−1 and 5000 ​mA ​h ​g−1 after 10000 cycles, the capacities of 124.1 and 100.3 ​mA ​h ​g−1 can still be obtained, respectively.

Controlled WS2 crystallinity effectively dominating sodium storage performance

WS2 exhibits tremendous potentials for Na-ions storage owing to high capacity (433 mAh g−1). Nevertheless, WS2 layered structure is often exfoliated with rapid capacity decay and sluggish reaction kinetics. In this work, WS2 nanosheets with different crystallinities are controlled by different synthesis methods. The high crystallinity WS2 exhibits high degree of interlayer order and strong interlayer force. It exhibits superior electrochemical properties, at the current density of 200 mA g−1 after 300 cycles with reversible capacity of 471 mAh g−1. Even at 5.0 A g−1, the capacities can still arrive at 240 mAh g−1 after 250 cycles, exhibiting stable cycling performance. Further electrochemical research finds that the high degree of interlayer order of layered WS2 structure can perform highly conducive Na+ insertion/extraction with greatly improved contribution of intercalation capacity. Moreover, the strong interlayer force can effectively restrain the exfoliating of the WS2 nanosheets, guaranteeing the stability of the structure. Combining the above result reveals that controlling the order and force of the interlayer is an effective way to enhance the electrochemical properties of WS2 as SIBs anode materials. This work can provide new insight for inhibiting the exfoliation of layered compounds to pursue excellent electrochemical performance in Na-ion storage systems.

An Aqueous Al-Ion Battery Boosted by Triple-Ion Intercalation Chemistry with a High-Energy MnAl <sub>2</sub>O <sub>4</sub> Nanosphere Cathode

AlCl3 water-in-salt electrolyte has successfully expanded the electrochemical window of aqueous Al-ion battery to 4 volts, however, the limited Al intercalation capacity of graphite (165 mAh g-1 ) preclude higher energy density. A high-energy MnAl2O4 cathode was synthesized by a simple two-step hydrothermal method, which can utilize triple-ion intercalation chemistry to achieve a high specific capacity of 330 mAh g-1 with an average discharge voltage of 1.68V versus Al/Al3+ (a record energy density of 555 Wh kg-1 ). Besides, a higher discharge capacity of 830 Wh kg-1 was achieved with higher-concentration electrolyte, showing a potential capacity for cation intercalation. Unique triple-ion intercalation chemistry was firstly investigated thoroughly. Experimental characterization attributes this high voltage to the intercalation of anions, e.g., AlCl4- and Cl- , and Cl- was also revealed an interaction function with intercalated Al3+ cations, which can benefit the design of Aluminium-ion batteries (AIBs) in the future.

Studies on kinetics and diffusion characteristics of lithium ions in TiNb2O7

The diffusion coefficients and kinetics of lithium ion transport in TiNb2O7 nanocrystals at different charge-discharge potentials are determined by using Galvanostatic Intermittent Titration Technique (GITT), Electrochemical Impedance Spectroscopy (EIS) and Cyclic Voltammetry (CV). The chemical diffusion coefficient values (Dchem) at different intercalation and de-intercalation potentials vary in a range of 10−15 - 10−16 cm2 s−1 and exhibit a ‘W’- type behavior. The differential intercalation capacity (Cint) derived from various electrochemical techniques are compared, which showed maximum value at the lowest chemical diffusion coefficient. Cyclic voltammograms recorded at different scan rates are used to study the kinetics of Li-ions, which showed a capacitive behavior of 53% at 0.10 mV s−1 for TiNb2O7, demonstrating its suitability as high rate anode material in lithium ion batteries.

Restriction‐Induced Luminescence Enhancement in 2D Interlayer Supramolecular Infinite Solid Solution for Cell Imaging

AbstractConsidering the anionic intercalation capacities of layered double hydroxides (LDH), 2‐hydroxy‐4‐methoxybenzophenone‐5‐sulfonate (BP4) and decanesulfonate (DES) anions are cointercalated into the interlayers of Mg2Al‐LDH to form DES–BP4 (x%)/LDH composites, which can be regarded as 2D interlayer supramolecular infinite solid solutions (2D ISISSs), according to a structural analysis. Compared to those of pristine BP4, the fluorescence properties of DES–BP4 (x%)/LDH 2D ISISSs are significantly improved and their emission peak wavelengths are adjustable in the range of 491–510 nm by varying x. DES–BP4 (8%)/LDH exhibits the optimal fluorescence properties. Its quantum yield, lifetime, and fluorescence intensity are increased ≈14, 4, and 45 times, respectively. Moreover, its nonradiative relaxation rate constant is decreased five times, while its radiative relaxation rate constant is increased three times. The luminescence enhancement can be attributed to the formation of the 2D ISISSs system, which effectively restricted the intramolecular movements of BP4 anions. Owing to its enhanced fluorescence properties, DES–BP4 (8%)/LDH exhibits outstanding performances for cell penetration and confocal fluorescence imaging and lifetime imaging of lysosome in HeLa cells. Therefore, the 2D ISISSs based on the LDH matrix provide a novel route to optimize the performances of functional molecules and expand their applications.

Impact of Surface Modification on the Lithium, Sodium, and Potassium Intercalation Efficiency and Capacity of Few-Layer Graphene Electrodes.

In a conventional lithium-ion battery (LIB), graphite forms the negative electrode or anode. Although Na is considered one of the most attractive alternatives to Li, achieving reversible Na intercalation within graphitic materials under ambient conditions remains a challenge. More efficient carbonaceous anode materials are desired for developing advanced LIBs and beyond Li-ion battery technologies. We hypothesized that two-dimensional materials with distinct surface electronic properties create conditions for ion insertion into few-layer graphene (FLG) anodes. This is because modification of the electrode/electrolyte interface potentially modifies the energetics and mechanisms of ion intercalation in the thin bulk of FLG. Through first-principles calculations; we show that the electronic, structural, and thermodynamic properties of FLG anodes can be fine-tuned by a covalent heteroatom substitution at the uppermost layer of the FLG electrode, or by interfacing FLG with a single-side fluorinated graphene or a Janus-type hydrofluorographene monolayer. When suitably interfaced with the 2D surface modifier, FLG exhibits favorable thermodynamics for the Li+, Na+, and K+ intercalation. Remarkably, the reversible binding of Na within carbon layers becomes thermodynamically allowed, and a large storage capacity can be achieved for the Na intercalated modified FLG anodes. The origin of charge-transfer promoted electronic tunability of modified FLGs is rationalized by various theoretical methods.

Low-cost lignite-derived hard carbon for high-performance sodium-ion storage

Sodium-ion batteries are regarded as the most promising alternative candidates for lithium-ion batteries. Hard carbon, as a kind of anode materials, has been demonstrated to deliver high specific capacity and stable cycling performance. However, it is still difficult to strike the balance between the relatively high cost and the superior electrochemical performance. We successfully fabricated low-cost lignite-derived hard carbons (a-LCs) with easy scale-up method. The microstructure, morphology and surface information of the obtained a-LCs are evaluated by X-ray diffraction, Raman spectrum and Fourier transform infrared spectrometer. By changing carbonization temperature, a-LCs’ microstructure and defect composition can be tuned and quite different sodium-ion storage behaviors can be seen. When carbonization temperature increases, the carbon microcrystallites grow and defects decay, resulting in a decrease in defect absorption capacity and an increase in graphitic-like nanodomain intercalation capacity. Particularly, a-LC carbonized at 1200 °C (a-LC-1200) can deliver a high capacity of 256 mAh g−1 with the initial Coulombic efficiency of 82%. Besides, it also exhibits a superior rate performance of 210, 197, 180, 168 and 146 mAh g−1 at current rates of 1, 2, 5, 10 and 20C (defined that 1C = 200 mA g−1), respectively. It solves the above problems very well and displays great commercial value.

Multi carbonyl polyimide as high capacity anode materials for lithium ion batteries

Organic materials are prominent alternative materials for lithium-ion batteries due to their stable cycling, large flexibility, high capacity and various molecular structures. Here, we report a multi carbonyl polyimide material with six carbonyl groups per polymer unit denoted as PMTA, showing super high lithium intercalation capacity and favorable cycling performance as lithium-ion anode material. The as-synthesized PMTA can deliver a capacity of 1638 mAh g−1 at current density of 100 mA g−1, and remain a reversible capacity of 698 mAh g−1 after 50 cycles at a temperature of 30 °C. Excellent durability, capacity and reversibility can also be observed at 60 °C. The as-prepared PMTA anode electrode material can embed 22 lithium-ions per polymer unit, displaying a theoretical specific capacity of 1704 mAh g−1, maintaining a discharge capacity of 994 mAh g−1 after 500 charge and discharge cycles at current density of 1000 mA g−1 at 60 °C, and a coulomb efficiency of approximately 99%. The outstanding performance of the as-synthesized PMTA suggests that introduction of more carbonyl groups will be an effective way to promote lithium intercalation capacity and realize the practical application of high energy density polymer electrodes materials for lithium ion batteries.

A Site-Selective Doping Strategy of Carbon Anodes with Remarkable K-Ion Storage Capacity.

The limited potassium-ion intercalation capacity of graphite hampers development of potassium-ion batteries (PIB). Edge-nitrogen doping is an effective approach to enhance K-ion storage in carbonaceous materials. One shortcoming is the lack of precise control over producing the edge-nitrogen configuration. Here, a molecular-scale copolymer pyrolysis strategy is used to precisely control edge-nitrogen doping in carbonaceous materials. This process results in defect-rich, edge-nitrogen doped carbons (ENDC) with a high nitrogen-doping level (up to 10.5 at %) and a high edge-nitrogen ratio (87.6 %). The optimized ENDC exhibits a high reversible capacity of 423 mAh g-1 , a high initial Coulombic efficiency of 65 %, superior rate capability, and long cycle life (93.8 % retention after three months). This strategy can be extended to design other edge-heteroatom-rich carbons through pyrolysis of copolymers for efficient storage of various mobile ions.

Nanoporous coal via Ni-catalytic graphitization as anode materials for potassium ion battery

Potassium-ion batteries (PIBs), with advantages of abundant and easily accessible raw materials of potassium, are receiving increasing attention. Carbon-based materials are perceived as one of the most prospective PIBs anode materials due to their rational intercalation capacity and abundant resources. However, their intercalation chemistry reaction involving potassium intercalation/deintercalation can lead to a large irreversible volume change of anode, resulting in poor cycle performance. Herein, coal, with a natural pore structure which can eliminate negative effects of volume change in the intercalation processes, is explored for the anode in PIBs after a catalytically graphitized process. Graphitized coal via annealing catalysis with NiCl2·6H2O displays a superior K+ storage performance of 248.0 mAh g−1 at 50 mA g−1 after 100 cycles, which is 1.5 times as that of raw coal and 5.9 times as that of reference graphite.

Preparation of novel morning glory structure γ-MnO2/carbon nanofiber composite materials with the electrospinning method and their high electrochemical performance.

A novel γ-MnO2/carbon nanofiber composite electrode material with a morning glory structure was prepared for the first time by electrospinning a mixture solution of Mn(CH3COO)2 salt and polyacrylonitrile and subsequently treating it with NH3 atmosphere. The resultant materials were applied in supercapacitors, exhibiting a high voltage of 2 V and high energy density of 15.7 W h kg−1 at the current density of 0.5 A g−1 in 1 M Na2SO4 solution. In this study, precisely controlling the concentration and time of the reaction resulted in the novel morning glory structure. And the morning glory structure at the surface of the carbon nanofibers increased the specific surface area and shortened the diffusion path for charge transport, increasing the Na+/H+ ion intercalation capacity, accounting for the high voltage and energy density of the present supercapacitors. These results demonstrated that this new-type of carbon nanofiber with morning glory structure electrode material is potentially superior in obtaining a high voltage for electrode materials and supercapacitors. We hope that these novel materials can expand to different applications in the energy or catalytic field.

Chitosan and chitosan oligosaccharide: Advanced carbon sources are used for preparation of N-doped carbon-coated Li2ZnTi3O8 anode material

Novel N-doped carbon coated Li2ZnTi3O8 anode active materials are synthesized via one step high temperature calcination solid state reaction method using chitosan and chitosan oligosaccharide as advanced carbon sources. Coating a nano-thickness conductive N-doped carbon layer between particles is beneficial to enhance the electronic transmission speed. Physical characterization results show that all as-prepared samples have a cubic spinel structure with a P4332 space group without any impurities, and the Li2ZnTi3O8 with chitosan additive (molecular weight: 5000) has the best dispersity and smallest particle size in all as-prepared electrode materials. The length of organic compound molecular chain has a direct impact on the agglomeration of particles and reversible lithium intercalation capacity. When tested as the anode for lithium ion batteries, the optimal electrode material shows the largest discharge capacities and remarkable long-term cycling stability at a current density of 1.0, 2.0, and 5.0 A g−1 over 500 cycles, respectively. Combining structural characterization with electrochemical performance, N-doped carbon layer, high degree of particle dispersibility and larger interface contact area are contributed to the enhancement of both electronic and ionic conductivities and of Li2ZnTi3O8.

BC2N/Graphene Heterostructure as a Promising Anode Material for Rechargeable Li-Ion Batteries by Density Functional Calculations

We performed density functional calculations to systematically investigate the adsorption and diffusion properties of Li atoms in three different structures of BC2N and the heterostructures (I-BN and I-HH) formed by a combination of BC2N-I and graphene as anode materials. The theoretical calculations predicted that monolayer BC2N-I has a high capacity (546 mAh/g) with an average voltage of 0.32 eV. However, Li adsorptions on the BC2N-II and BC2N-III monolayers are not energetically favorable reactions. After combining with graphene, the capacity of the heterostructure I-BN has been greatly enhanced to 691 mAh/g and the lowest energy barrier of diffusion pathways is also obviously reduced to 0.073 eV. In theory, the fastest Li diffusion mobility in the interface of I-BN is about 6.6 × 102 times faster than that on a BC2N-I sheet at room temperature. In this work, we made a comparison of monolayer BC2N and the heterostructures of BC2N/G, and suggest that I-BN is a promising anode material for lithium-ion batteries due to its high intercalation capacity and fast charge/discharge rates.

Defect Engineering of Iron-Rich Orthosilicate Cathode Materials with Enhanced Lithium-Ion Intercalation Capacity and Kinetics

Defect engineering via nonstoichiometric composition control can serve as an effective strategy to tune the electronic and crystal structures of intercalation compounds, as has been recently eviden...

Mn/Ti layered double hydroxide: an investigation into the structure and electron transport through combinatorial experimental and theoretical approaches

Layered double hydroxides (LDH) also known as hydrotalcite-like compounds that represent a broad class of lamellar basic inorganic compound possessing high capacity for anion intercalation. In this work, Mn/Ti LDH has been synthesized through a single step hydrothermal route using commercially available Mn(NO3)2.4H2O, TiCl4 and urea for investigation into the morphological and electron transport properties. The structural aspects and electron transport within the Mn/Ti LDH, has been investigated through a combinatorial approach of co-relating the experimental results with theoretical studies. The data mined crystal structure of the material, has been presented after comparison of the experimental XRD with the data mined XRD parameters. The characterizations suggest the material to possess crystallinity, layered structure, hexagonal morphology, good potentiodynamic electrochemical response, narrow multiple direct band gaps. The multiple narrow band gaps and electron transport properties could be evident through the UV-visible DRS and cyclic voltammetry analyses of the material. In order to theoretically establish electron transport, the experimental values of band gaps and ξ-potential results have been incorporated into the expression for the conduction-band energy (Ec) for generating the density patterns of the LDH through Monte Carlo simulations. Fermi–Dirac statistics presented the probability of transfer of electrons from VB to CB at different temperatures and for given energies for Mn/Ti LDH material. This work emphasized on the methodological advances associated with the structural and electron transport aspects of Mn/Ti LDH.