Electrochemical Capacity Research Articles

Efficient synergy of MOF-derived CoTe2 polyhedron anchoring on CNTs as anode materials for Na-ion storages

The transition metal chalcogenides (TMCs) are promising anode materials with excellent theoretical capacity and controllable synthesis approaches for Sodium ion batteries. However, the obvious volume effects and sluggish kinetics in the long-term sodiation/desodiation reaction limit the stability and high-capacity. Herein, the CoTe2 @carbon nanocomposite electrodes (CoTe2 @CNTs) are designed by ZIF-67 derived to conquer the volume expansion, synchronously, and CNTs anchored strategy are adopted to promote Na+ diffusion dynamics, and ensure cyclic stability and long cycle life of anode materials. Specifically, the as prepared nanocomposite constructed by CoTe2 and CNT has displayed efficient Na+ storage mechanism by providing multiple adsorption sites, interconnected conductive network and abundant ions transport pathways, which are revealed by the density functional theory calculations. Furthermore, the in-situ CNTs anchored of CoTe2 polyhedron have significantly enhanced the charge transfer capacity for Na+/electron and metallic properties of CoTe2 @CNT composites, which exhibit outstanding electrochemical capacities (112.7 mAh g−1 at 2 A g−1 after 500 cycles) and pseudocapacitive-dominated behaviors when used as anodes. This work is expected to provide a legitimate and convenient approach with the controllable preparation of nanocomposite in energy storge devices.

Ultrafast Nucleation Reverses Dissolution of Transition Metal Ions for Robust Aqueous Batteries.

The dissolution of transition metal ions causes the notorious peeling of active substances and attenuates electrochemical capacity. Frustrated by the ceaseless task of pushing a boulder up a mountain, Sisyphus of the Greek myth yearned for a treasure to be unearthed that could bolster his efforts. Inspirationally, by using ferricyanide ions (Fe(CN)63-) in an electrolyte as a driving force and taking advantage of the fast nucleation rate of copper hexacyanoferrate (CuHCF), we successfully reversed the dissolution of Fe and Cu ions that typically occurs during cycling. The capacity retention increased from 5.7% to 99.4% at 0.5 A g-1 after 10,000 cycles, and extreme stability of 99.8% at 1 A g-1 after 40,000 cycles was achieved. Fe(CN)63- enables atom-by-atom substitution during the electrochemical process, enhancing conductivity and reducing volume change. Moreover, we demonstrate that this approach is applicable to various aqueous batteries (i.e., NH4+, Li+, Na+, K+, Mg2+, Ca2+, and Al3+).

Flexible CoFe2O4 nanoparticles/N-doped carbon nanofibers membrane as self-standing anode for lithium-ion batteries

The development of new generation wearable electronic devices requires the power supply with high power density, long-term cycling performance, and excellent flexibility and mechanical stability that would enhance the durability of flexible devices during use. Herein, we designed a novel strategy for the preparation of flexible self-supporting nanofiber membrane with highly dispersed CoFe2O4 nanoparticles embedded in one-dimensional (1D) N-doped carbon nanofibers (denoted as [email protected]) by electrospinning and subsequent thermal treatment process, which possesses unique hierarchical structure containing zero-dimensional [email protected] carbon nanospheres and cross-linked three-dimensional (3D) fiber network. The rational combination of the nano-sized CFO particles with high theoretical capacity and a N-doped carbon nanofiber conductive skeleton with interconnected 3D open microstructure facilitates the robust penetration of electrolyte into the electrode, improves the overall electrical conductivity of the electrode, shortens the diffusion pathways of Li+ ions, and buffers the volume change of active materials during lithiation/delithiation. As a consequence, the optimized [email protected] exhibits relatively high electrochemical reversible capacity (611.4 mA h g−1 at 100 mA g−1 after 100 cycles) and good cycling stability, as well as satisfactory rate capability.

Enhanced lithium storage capability of Ni-rich LiNi0.9CoxMn0.1−xO2(0 ≤ x ≤ 0.1) cathode by co-operation of Al-doping and V-coating

The Nickel-rich layer materials LiNixCoyMn1−x−yO2 (x ≥ 0.9) are usually accompanied by structural instability and inevitable capacity loss due to surface degradation during long cycles. The Al-V dual-modification is used in this research to enhance the stability of the structure and the electrochemical capacity of LiNi0.9Co0.05Mn0.05O2 (NCM). First, Al source was added during the co-precipitation synthesis of the precursors. Then, the Al-doped precursors were treated at 720 ℃ for 10 h with slight excess lithium to prevent volatilization of lithium during the sintering process. Finally, Al-doped LiNi0.9Co0.04Mn0.03Al0.03O2 (NCMA) materials were treated with V2O5 at 450 ℃ for 4 h. During calcination, Li3VO4-coated LiNi0.9Co0.04Mn0.03Al0.03O2 materials (NCMAV) were generated by employing residual lithium. Meantime, the Al-V dual-modification helps reduce the mingling degree of Ni2+/Li+ and promotes the diffusion of Li+. Hence, the Al-V dual-modified NCMAV displays a superior rate capability of 162.2 mAh g−1 at 5 C, remaining predominant capability retention of 90.5% after 100 cycles at 4.3 V. Compared with NCMAV, the discharge capability of pure NCM is 140.3 mAh g−1 and its capability retention is 81.6% at 5 C. This dual-modification strategy provides a facile and scalable method to achieve massive application of NCM LIBs with high density and excellent cycling stability.

Self-assembled nano Co-Ni pompon structured hierarchical porous carbon and the excellent electrochemical capacity

Supercapacitor is an energy storage device with excellent performance which has been studied in recent years. Biomass-based porous carbon materials are widely used as electrode materials for supercapacitors because of their good pore structure and electrical conductivity. A unique nanoscale pompon with structured porous carbon as core was synthesized by a two-stage activation of H3PO4-K2C2O4 combined with hydrothermal self-assembly in this research. Results showed that the specific surface area of the hierarchical porous carbon sample was up to 1608.1 m2/g with the mesoporous ratio of 54.26%. The self-doped Co-Ni elements were successfully entered into the channel of carbon core and then the self-assembled nano pompon epidermis was formed. Interleaving nanorods with unique characteristics as dispersion at the bottom and aggregation at the top were evenly grown on the surface of the pompon, forming a 3D network structure with a mass of cavities, which brought with excellent faradaic pseudocapacitance of electrode materials. The energy density and power density of the asymmetric supercapacitor assembled by nano pompom and porous carbon reach 30.4 Wh/kg and 1367.1 W/kg respectively.

Boosting catalytic and CO2 adsorption ability by in situ Cu nanoparticle exsolution for solid oxide electrolysis cell cathode

Solid oxide electrolysis cell (SOEC) is recognized as an effective means to accomplish sustainable development since it is an efficient electrochemical technology for CO2 emission reduction. However, the electrocatalytic reduction activity of the cathode for CO2 restricts the development of SOEC. Herein, an A-site deficient perovskite Sr1·9Fe1·3Cu0·2Mo0·4Ti0·1O6-δ (SFCMT) was proposed as cathode material that can in situ exsolve uniform Cu nanoparticles. The exsolution of Cu increases the concentration of oxygen vacancies and provides abundant adsorption sites for CO2, resulting in excellent electrochemical catalytic capacity. Cu@SFCMT-based single cells exhibit excellent electrolytic performance under pure CO2, with current densities up to 3.21 A cm−2 at 1.8 V and 800 °C and interface polarization resistance (Rp) as low as 0.20 Ω cm2 at 800 °C. Furthermore, the current density changes slightly after the 140 h stability test at 1.2 V. Cu@SFCMT exhibits outstanding electrochemical activity and durability, making it a viable SOEC cathode material.

Ab-initio analysis of Li adsorption on boron doped armchair silicon carbide nanoribbon for lithium ion batteries (LIBs)

It is well known that the electrochemical storage capacity of anode materials can be modified by the doping of heteroatom. Here, first-principles approach is used to investigate the adsorption energy (Eads), open circuit voltage (OCV), and storage capacity of boron co-doped armchair silicon carbide anode (B-ASiCNR) material for Li ion battery. When B atoms are doped at the center of the armchair silicon carbide nanoribbon (ASiCNR), new energy states emerge and it results in Fermi-Level shift towards the valence band. The binding strength of a single Li atom is significantly higher in B-ASiCNR because of B atom doping. The open circuit voltage decreases from 3.76 V to 2.34 V when Li atoms adsorbed from first hexagonal position to all hole position of the substrate. Calculations reveal that the storage capacity of B-ASiCNR reached to the maximum value of 836 mAhg−1 when all hole positions are adsorbed by Li atoms. Calculated Eads, OCV, storage capacity suggest that the B-ASiCNR can be used as future anode materials for Li ion battery.

A review of current problems and plausible solutions of lithium-based battery

The lithium-based battery has become the hottest topic and could be attractive technologies for electrical energy storage that have higher electrochemical stability and make long-range electric vehicles possible. However, many technical obstacles about electrochemical stability and energy capacity are needed to be mitigated or solved. In this article, the possible solutions of the nanometer anode materials in the lithium-based battery and advanced techniques for improving capacity and safety of the battery are summarized.

Lithium (Poly)sulfide Phase Conversion in Working Lithium–Sulfur Batteries: The Insight from the Equilibrium Potential Model

The commercialization of lithium–sulfur (Li–S) batteries is currently hindered by the electrochemical instability and capacity loss, due to the ultracomplex phase conversion of lithium polysulfides (LPSs) and lithium sulfide (Li2S). Revealing the mechanism is critical to rational regulation of the cathode reaction process so as to improve the cycling stability and capacity retention. Herein, we develop an equilibrium potential model to reveal the two conversion pathways under different electrolyte/sulfur ratios of working Li–S batteries. The model predicts that the supersaturation of Li2S and the precipitation of LPSs are responsible for the potential drop at the onset of the second plateau and the emergence of the third plateau, respectively, deviating from the typical discharge profiles. Furthermore, quantitative guidance for electrolyte screening and battery assembling is presented to selectively control LPS precipitation. The description of equilibrium potential could be used as a foundation for mechanism study and battery monitoring system development.

A Polyacrylonitrile Shutdown Film for Prevention of Thermal Runaway in Lithium-Ion Cells

The electrodeposition of a polymer (polyacrylonitrile, PAN) is used to reduce the risk of thermal runaway in lithium-ion batteries, which is the most important cause of battery accidents and fires. PAN was electrodeposited on a graphite battery electrode, using cyclic voltammetry or chronoamperometry, in a solution with acrylonitrile as the solvent. The electrodeposited PAN film was characterised by Raman spectroscopy, microscopy, energy dispersive X-ray analysis, and thermogravimetric analysis, and it was found that the film thickness could be controlled by the amount of charge passed in the electrochemical experiments. The PAN-coated graphite battery electrode was then tested in lithium half-cells, obtaining capacities close to the uncoated graphite sample (ca. 360 mA h g−1) for thin (<10 µm) polymer coatings at 25 °C. Interestingly, for thicker polymer coatings (>20 µm) it was found that the capacity decreased drastically as the temperature increased beyond 80 °C. Such suppression in capacity has applications for thermal runaway protection since the electrochemical reactions of degradation of the electrolyte in contact with the electrode are the root cause of the thermal runaway process. Further work should look into alternative polymer and liquid electrolyte formulations to achieve the desired suppression of electrochemical capacity at high temperatures while retaining high capacities at the operational temperature range.

π-Conjugated electrochemically stable covalent quinazoline network for lithium ion storage

Covalent organic frameworks (COFs) have been widely used as electrode materials for lithium ion batteries due to their adjustable structure, abundant porous structure and large specific surface area. In this work, 2D porous covalent quinazoline organic network (CQN) materials, with abundant mesoporous and nitrogen-containing active sites, were synthesized by a simple ionic thermal reaction. Due to the abundant active sites in the structure of CQN, CQN anodes show excellent electrochemical capacity (975 mAh g−1) and at 1.0 A g−1current density, the capacity retention rate is 82 % after 1000 cycles. The theoretical calculation results show that the N of the quinazoline group is an effective active site. However, due to hindrance by H+, the Li+ diffusion channel is mainly a 2D interlayer. Furthermore, the structure of the CQN material is similar to that of nitrogen-doped graphene and has good electronic conductivity; thus, leading to outstanding rate performance.

Nickel-rich layered cathode LiNi0.8Co0.1Mn0.1O2 mediated by a selective lattice doping towards high-performance lithium ion battery

Rapid capacity loss and voltage fading pose a significant barrier to the commercialization of nickel-rich materials with layered structures due to particle cracking and structure degradation. Double element selective lattice modification strategy that can balance multiple performance requirements is gaining attention. Here, we proposed a selective lattice doping strategy to enhance the lattice stability of LiNi0.8Co0.1Mn0.1O2 via a double element co-doping of Mg and W. Impressively, the Mg/W co-doping improved electrochemical reaction kinetics and discharge capacity, and largely suppressed structure degradation simultaneously. In situ X-ray diffraction (XRD) results demonstrated that W/Mg co-doping can tune H2−H3 phase transition, relieving the lattice stress and mechanical degradation. These improvements can be attributed to a synergistic effect of W and Mg, in which high valence state W6+ induced the formation of Ni2+ and strong W−O bonds increased layer structure stability, meanwhile Mg2+ as a pillar inhibited Li+/Ni2+ mixing and maintained structural stability. This work provides selective lattice dual-doping strategic guidelines for the use of high energy efficiency and robust stability high-nickel low-cobalt cathodes in lithium-ion batteries.

Synthesis and Nanostructure Investigation of Hybrid β‐Ga2O3/ZnGa2O4 Nanocomposite Networks with Narrow‐Band Green Luminescence and High Initial Electrochemical Capacity (Small 18/2023)

Network Materials In article number 2207492, Niklas Wolff, Ion Tiginyanu, Lorenz Kienle, and co-workers report on the synthesis and structural characterization of a hybrid wide-band-gap semiconductor nanocomposite network of interconnected hollow microtubes composed of β-Ga2O3/ZnGa2O4 phases using X-ray powder diffraction and transmission electron microscopy. The aero-network morphology shows ZnGa2O4-dominated narrow band green light emission under UV light excitation and high initial electrochemical capacity versus Li-ion loading.

The Effect of Y Content on Structural and Sorption Properties of A2B7-Type Phase in the La-Y-Ni-Al-Mn System.

Metal hydrides are an interesting group of chemical compounds, able to store hydrogen in a reversible, compact and safe manner. Among them, A2B7-type intermetallic alloys based on La-Mg-Ni have attracted particular attention due to their high electrochemical hydrogen storage capacity (∼400 mAh/g) and extended cycle life. However, the presence of Mg makes their synthesis via conventional metallurgical routes challenging. Replacing Mg with Y is a viable approach. Herein, we present a systematic study for a series of compounds with a nominal composition of La2-xYxNi6.50Mn0.33Al0.17, x = 0.33, 0.67, 1.00, 1.33, 1.67, focusing on the relationship between the material structural properties and hydrogen sorption performances. The results show that while the hydrogen-induced phase amorphization occurs in the Y-poor samples (x < 1.00) already during the first hydrogen absorption, a higher Y content helps to maintain the material crystallinity during the hydrogenation cycles and increases its H-storage capacity (1.37 wt.% for x = 1.00 vs. 1.60 wt.% for x = 1.67 at 50 °C). Thermal conductivity experiments on the studied compositions indicate the importance of thermal transfer between powder individual particles and/or a measuring instrument.

High-efficiency electrochemical removal of Cd(II) from wastewater using birnessite-biochar composites: Performance and mechanism.

Birnessite has been widely used for electrochemical removal of heavy metals due to its high pseudocapacitance. Incorporation of carbon-based materials into birnessite can enhance its conductivity and stability, and synergistically improve the electrochemical adsorption capacity due to the double-layer capacitor reaction derived from carbon-based materials. In this study, biochar was successfully incorporated with birnessite at various ratios to synthesize composites (BC-Mn) for effective electrochemical removal of cadmium (Cd(II)) from water. The effects of cell voltage, initial pH, and recycling performance of BC-Mn were evaluated. As a result, the electrosorption capacity of BC-Mn for Cd(II) exhibited gradual increases with increasing birnessite content and reached equilibrium at a Mn content of 20% (BC-Mn20). The Cd(II) adsorption capacity of BC-Mn20 rose at higher cell voltage, and reached the maximum at 1.2V. At pH 3.0-6.0, the electrosorption capacity initially rose until pH 5.0 and then approached equilibrium with a further increase in pH value. The Cd(II) electrochemical adsorption capacity of BC-Mn20 in the solution could reach 104.5mgg-1 at pH 5.0 for 8h at 1.2V. Moreover, BC-Mn20 exhibited excellent reusability with a stability of 95.4% (99.7mgg-1) after five cycles of reuse. Due to its superior heavy metal adsorption capacity and reusability, BC-Mn20 may have a promising prospect in the remediation of heavy metal polluted water.

Electrochemical Energy Storage Capacity of Surface Engineered Renewable Carbon Derived from Industrial Tea Waste by HNO3 and K2CO3

Electrochemical Energy Storage Capacity of Surface Engineered Renewable Carbon Derived from Industrial Tea Waste by HNO3 and K2CO3

Effect of tension during stabilization on carbon fiber multifunctionality for structural battery composites

Here we demonstrate carbon fibers with tailorable multifunctional properties for energy storage composites. Carbon fibers made from the same precursor but with different processing tensions are investigated. The applied tension during the stabilization/oxidation stage of fiber manufacturing determines the microstructure and the resulting mechanical and electrochemical performance. Understanding of the interconnected effects enables tailoring of fibers to function as electrodes in structural battery composites. The study reveals that both amorphous and crystalline phases affect the electrochemical capacity, as higher capacity is achieved by larger d-spacing as well as higher void content. Further, the study confirms the trade-off between high tensile strength and high electrochemical capacity that needs to be taken into consideration when designing multifunctional carbon fibers.

First-principles analysis of electrochemical hydrogen storage behavior for hydrogenated amorphous silicon thin film in high-capacity proton battery

Silicon material electrodes as proton carriers for high-capacity proton battery have only been proposed for such a short period of time that their physicochemical properties and electrochemical hydrogen storage behavior during charge and discharge processes remain nearly uncharted territory. Herein, the hydrogenated amorphous silicon (a-Si:H) thin film electrodes are prepared by radio frequency sputtering followed by ex-situ hydrogenation. The electrochemical properties of a-Si:H electrodes are tested experimentally, and the electrochemical hydrogen storage behaviors of a-Si:H electrodes are analyzed by first-principles calculations. The results show that the hydrogenation process significantly increases the electrochemical capacity of the electrodes and reduces the band gap of the electrode structure. The electrode exhibits weak conductivity during the initial charging, but the instability of the electrode electronic structure during the later charging results in a slight fluctuation of the electrochemical charging process. The a-Si:H electrode have better electrochemical hydrogen storage/release reversibility than non-hydrogenated electrodes, but this reversibility is weakened by oxygen atoms covered on the electrode surface. The electrochemical hydrogen storage process is easier to accomplish than the electrochemical desorption process of hydrogen evolution reaction for the a-Si:H electrodes. The a-Si:H thin film electrode is more stable on the Ni(111) substrate surface and the good conductivity of the electrode/substrate interface provides convenient conditions for the free transport of electrons in the electrochemical charge/discharge processes. We believe that these results perfectly explain the microscopic mechanisms responsible for the electrode reaction and electrochemical behavior of a-Si:H electrodes in this type of proton battery, and have a certain reference value in understanding the physicochemical properties and electrochemical hydrogen storage behavior of silicon material electrodes applied to other types of batteries during charge/discharge processes.

Properties of AB5 type hydrogen storage alloy after α-AlH3 alloying

AB5 type hydrogen storage alloys have been widely used in Ni-MH batteries due to their high electrochemical capacity, excellent rate performance, and low pollution. However, the high activation difficulty limited their development in the solid-state hydrogen storage field. Mechanical alloying to synthesize composites is an effective way to reduce activation energy. In this paper, the structure and hydrogen storage properties of the LaNi5+nAlH3 (n = 0, 1, 3 wt.%) composites were investigated. The results show that with the incremental of AlH3 alloying content, the lattice constant a, b, and c and the volume (V) of the LaNi5 unit cell tend to increase, the hydrogen absorption platform pressure of the composite material gradually decreased, and the hydrogen release platform pressure gradually increased. It resulted in a reduction in the hysteresis factor (Hf) of the composite from 0.66 to 0.35. This will reduce energy waste during energy conversion. In addition, the activation property of the alloy was improved after AlH3 alloying. This will facilitate the application of AB5 type hydrogen storage alloys.

Experimental and numerical studies of slurry-based coextrusion deposition of continuous carbon fiber micro-batteries to additively manufacture 3D structural battery composites

Carbon fiber structural battery composites have recently attracted growing interests due to their potentials of simultaneously carrying mechanical loads and storing electrical energy for lightweight application. In this study, we present a slurry-based coextrusion deposition method to additively manufacture 3D structural battery composites from carbon fiber micro-batteries. Cathode slurry is coextruded together with solid polymer electrolyte-coated carbon fibers in a single deposition. A network of carbon fiber micro-batteries is achieved within the fabricated structural battery composites. Electrochemical tests show a stable charge-discharge performance up to 100 cycles. The rheological behavior of the cathode slurry is found to govern the coextrusion process and the obtained electrochemical-mechanical properties. The rheological measurements are first used to identify printability windows in terms of solid loadings and binder contents in the cathode slurry. Increasing binder contents improve the mechanical properties, with maximum 1.1 GPa and 124 GPa obtained for tensile strength and modulus, respectively, but lowers the obtained electrochemical performance. Lowering solid loadings improves printability, simultaneously increasing electrochemical capacity (by 106%) and tensile modulus (by 108%) and strength (by 40%). Further microstructural characterization shows that residual voids play a major role in the obtained electrochemical and mechanical properties. A meso-scale computational fluid dynamics simulation is used to understand void formation during the coextrusion process. The cathode slurry rheology mainly affects degree of impregnation. The findings help understand the effects of the cathode slurry on 3D printing and how to further improve multifunctional performance for electrically powered structural systems where lightweight materials are in strong demands.