High-rate Electrochemical Performance Research Articles

Protective layer constructed by liquid phase quenching for long lifespan potassium ion batteries

Manganese-based transition metal layered oxides have garnered considerable attention for potassium-ion batteries (KIBs) due to their high energy density, high conversion efficiency, long lifespan and simple manufacturing processes. However, the slow K+ diffusion rate and poor stability fail to meet the increasing requirements of the energy storage system. The quenching technology was employed herein to in-situ form a thin protective layer of KMn4(PO4)3 with a high K+ diffusion rate on the surface of K0.5Mn0.85Co0.1Fe0.05O2. The introduction of the protective layer enhances electrochemical kinetics to promote high-rate electrochemical performance and reinforcing the ion diffusion dynamics, thus alleviating stress caused by uneven K+ distribution. Meanwhile, the reduction in Mn3+ content plays a crucial role in suppressing the Jahn-Teller distortion effect, contributing to enhanced cyclic stability. It exhibits an excellent electrochemical performance with a reversible specific capacity of 100.5 mAh g−1 at 0.2C, maintaining 72.97 % capacity after 500 cycles at 2C (1C=100 mA g−1). Coupled with graphite as the anode, the full cell shows a capacity retention of 73.53 % after 650 cycles at 2C, highlighting the potential for future practical applications.

Morphology-tuned synthesis of MgCo2O4@NiO arrays coated on nickel foam for high-rate supercapacitor electrode

In this study, hydrothermal synthesis and calcination strategies were used to grow MgCo2O4@NiO composites on nickel foam. NiO nanosheets were loaded onto rod-shaped MgCo2O4 to form a 3D MgCo2O4@NiO structure, which can intimate electrode/electrolyte contact and accelerate electron transport during a Faradic reaction. The MgCo2O4@NiO electrode exhibits superior high-rate electrochemical performance, which provides optimal capacities for the preparation. The cathode material exhibited a maximum capacity of 900.0 C g−1 at a current density of 1 A g−1. The composite material showed good long-cycle stability, retaining 96.3 % of capacities after 3000 cycles. The assembled supercapacitor achieved an energy density of 39.5 Wh kg−1 at a power density of 850.0 W kg−1. This study suggests that MgCo2O4@NiO is an encouraging candidate for the next-generation energy storage devices.

Honeycomb-like porous carbon embedded ferrous sulfide nanoparticles as bifunctional separator modifier by forming sulfur bonds with polysulfides in advanced lithium-sulfur batteries

To develop practical and outstanding lithium-sulfur (Li-S) batteries, it is advisable to adsorb soluble polysulfides and catalyze insoluble Li2S2/Li2S. Herein, a ferrous sulfide decorated honeycomb-like porous carbon (FeS/HMPC) was synthesized by sulfuration strategy to act as a separator modifier in Li-S batteries. Owing to the positive migration of the Fe d-band center, the binding of FeS to polysulfides is dominated by the S bond (Fe-SLiPSs), which makes FeS have strong adsorption capacity for various types of polysulfides. Moreover, FeS shows the minimum energy path for the migration of typical polysulfide Li2S. In other words, it has the smallest diffusion barrier. Hence, the FeS/HMPC-PP not only realizes the efficient suppression of the shuttle effect but also catalyzes the redox reaction of polysulfides. Benefiting from the above advantages, the FeS/HMPC-PP based cells exhibit a high initial capacity of 1673 mAh g−1 at 0.2 C and a reversible capacity of 686.7 mAh g−1 at 3 C after 500 cycles. Moreover, the cell with a high sulfur loading of 2.4mg cm−2 demonstrates an ultra-low-capacity decay of 0.007% per cycle at 0.2 C. This work provides novel insights and promising candidates to act as a functional separator for Li-S batteries with long life and high-rate electrochemical performance.

Massive anionic fluorine substitution two-dimensional δ-MnO2 nanosheets for high-performance aqueous zinc-ion battery

As one of the most promising materials for rechargeable aqueous zinc ion batteries (AZIBs), manganese oxide (δ-MnO2) need overcome the fatal limitations of structural instability and manganese dissolution for future practical application. Crystal high-orientated two-dimensional δ-MnO2 nanosheets with massive anionic fluorine were synthesized by a lava method with quenching treatment. When employed as a cathode material for zinc ion batteries, it exhibits a long cycling lifespan and high multiplicity performance. The fluorine atoms substitution can not only stabilize the manganese‑oxygen octahedron [MnO6] structure by introducing fluorine‑manganese chemical bonding, but also regulate the Mn3+/Mn4+ ratio by increasing the Mn3+ concentration content. Meanwhile, the obtained high-orientated 2D nanosheets structure can accelerate the ions kinetic behaviors for high rate electrochemical performance by shortening the ion translation and increasing the electronic conductivity. The optimized δ-MnO2 nanosheets exhibit a superior electrochemical performance of 288 mAh g−1 at current densities of 100 mA g−1. An excellent cycling lifespan up to 96 % capacity retention is indicated as well after 200 cycles at a current density of 200 mA g−1. This element doping strategy by molten salt quenching method has the benefits of simple synthesis steps and high yield with high economic efficiency.

Multiscale strain alleviation of Ni-rich cathode guided by in situ environmental transmission electron microscopy during the solid-state synthesis

Ni-rich layered oxides are one of the most promising cathode materials for Li-ion batteries due to their high energy density. However, the chemomechanical breakdown and capacity degradation associated with the anisotropic lattice evolution during lithiation/delithiation hinders its practical application. Herein, by utilizing the in situ environmental transmission electron microscopy (ETEM), we provide a real time nanoscale characterization of high temperature solid-state synthesis of LiNi0.8Co0.1Mn0.1O2 (NCM811) cathode, and unprecedentedly reveal the strain/stress formation and morphological evolution mechanism of primary/secondary particles, as well as their influence on electrochemical performance. We show that stress inhomogeneity during solid-state synthesis will lead to both primary/secondary particle pulverization and new grain boundary initiation, which are detrimental to cathode cycling stability and rate performance. Aiming to alleviate this multiscale strain during solid-state synthesis, we introduced a calcination scheme that effectively relieves the stress during the synthesis, thus mitigating the primary/secondary particle crack and the detrimental grain boundaries formation, which in turn improves the cathode structural integrity and Li-ion transport kinetics for long-life and high-rate electrochemical performance. This work remarkably advances the fundamental understanding on mechanochemical properties of transition metal oxide cathode with solid-state synthesis and provides a unified guide for optimization the Ni-rich oxide cathode.

Synthesis of co-doped high voltage lithium cobalt oxide with high rate electrochemical performance

LiCoO2 can further develops its capacity potential by increasing cut-off voltage, but the irreversible phase transition and structural damage at high voltage will lead to severe capacity fading. Here, we propose a method of multi-doping of four elements Ti, Mg, Al, and Y, which realizes the stable cycling of LiCoO2 at a cut-off voltage of 4.5 V through the synergistic effect among the four elements. The cell delivers the increased initial discharge capacity of 173.5 mAh/g, with the capacity retention rate as high as 91.1% after 100 charging-discharging cycles at the rate of 1 C in the voltage ranging from 3.0 to 4.5 V. Moreover, the capacity retention is still as high as 74.2% after 300 cycles. At the same time, the capacity can still be maintained close to 70% after 100 cycles at the temperature of 50 ℃. The specific discharge capacity of the cathode is 130.0 mAh/g, even if at high rate of 5 C. More than 5 times that of unmodified LiCoO2. We verified the effect of four-element co-doping on phase and surface stability by characterizing the materials before and after the cycle. At the same time, the positive effects of four doping elements on structural stability and electronic conductivity were clarified by DFT method. This work provides a promising idea of multi-element synergistic doping and contributes to solving problem of stable high voltage LiCoO2.

High-rate electrochemical performance and structure elucidation of hydrothermally synthesized nickel zincate nanorods

High-rate electrochemical performance and structure elucidation of hydrothermally synthesized nickel zincate nanorods

Smart Manufacturing Processes of Low-Tortuous Structures for High-Rate Electrochemical Energy Storage Devices.

To maximize the performance of energy storage systems more effectively, modern batteries/supercapacitors not only require high energy density but also need to be fully recharged within a short time or capable of high-power discharge for electric vehicles and power applications. Thus, how to improve the rate capability of batteries or supercapacitors is a very important direction of research and engineering. Making low-tortuous structures is an efficient means to boost power density without replacing materials or sacrificing energy density. In recent years, numerous manufacturing methods have been developed to prepare low-tortuous configurations for fast ion transportation, leading to impressive high-rate electrochemical performance. This review paper summarizes several smart manufacturing processes for making well-aligned 3D microstructures for batteries and supercapacitors. These techniques can also be adopted in other advanced fields that require sophisticated structural control to achieve superior properties.

Al-doping driven electronic structure of α-NiS hollow spheres modified by rGO as high-rate electrode for quasi-solid-state capacitor

Developing an optimized electronic structure of α-NiS electrode material is critical for its high-rate electrochemical performance of quasi-solid-state capacitor. Herein, Al3+ have been doped into α-NiS lattice and the reduced graphene oxide (rGO) is employed to modify Al-doping α-NiS, to alleviate the low-mobility charge of α-NiS. The electronic structure and electrochemical properties of α-NiS hollow spheres induced by Al-doping and rGO modification are investigated, both experimental characterization and theoretical results confirm Al-doping affect the electronic structure and electrochemical performance of α-NiS hollow spheres. In the composite of Al-doping α-NiS and rGO (named as AlxNi1-xS/rGO), the doped heteroatom improves the intrinsic electronic structure of α-NiS and the rGO provides a good electric conducting network, leading to an enhanced electrochemical performance of α-NiS as high-rate electrode material. After evaluation, the optimized Al0.2Ni0.8S/rGO composite shows a superior reversible capacity of 1096 C g−1 at 2 A g−1, and retains a capability of 471 C g−1 at a high-rate of 30 A g−1. Moreover, an asymmetric quasi-solid-state hybrid capacitors assembled by Al0.2Ni0.8S/rGO and activated carbon presents a high energy density of 30.6 Wh kg−1. This work provides a foundational strategy for the modification of α-NiS through Al-doping and combining with rGO, which has a positive effect on α-NiS electrode material in quasi-solid-state hybrid capacitors.

Optimizing the Electrolyte Systems for Na3 (VO1-x PO4 )2 F1+2x (0≤x≤1) Cathode and Understanding their Interfacial Chemistries Towards High-Rate Sodium-Ion Batteries.

Invited for this month's cover is the group of Prof. Dr. Zhipeng Sun at the Guangdong University of Technology. The image shows how electrolyte composition and their interfacial chemistries play a crucial role in manipulating the cathode/electrolyte interphases (CEI) and their corresponding high-rate electrochemical performance for sodium-ion batteries. The Research Article itself is available at 10.1002/cssc.202102522.

Long-cycling and high-rate electrochemical performance of expanded graphite cathode materials with a two-stage aluminum storage mechanism

The expanded graphite (EG) with the large interlayer spacing provides more transmission channel for AlCl4− anions. The two-stage aluminum storage mechanism of EG was confirmed by electrochemical technology and in situ X-ray diffraction technique.

Modification of Li- and Mn-Rich Cathode Materials via Formation of the Rock-Salt and Spinel Surface Layers for Steady and High-Rate Electrochemical Performances.

We demonstrate a novel surface modification of Li- and Mn-rich cathode materials 0.33Li2MnO3·0.67LiNi0.4Co0.2Mn0.4O2 for lithium-ion batteries (high-energy Ni-Co-Mn oxides, HE-NCM) via their heat treatment with trimesic acid (TA) or terephthalic acid at 600 °C under argon. We established the optimal regimes of the treatment-the amounts of HE-NCM, acid, temperature, and time-resulting in a significant improvement of the electrochemical behavior of cathodes in Li cells. It was shown that upon treatment, some lithium is leached out from the surface, leading to the formation of a surface layer comprising rock-salt-like phase Li0.4Ni1.6O2. The analysis of the structural and surface studies by X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy confirmed the formation of the above surface layer. We discuss the possible reactions of HE-NCM with the acids and the mechanism of the formation of the new phases, Li0.4Ni1.6O2 and spinel. The electrochemical characterizations were performed by testing the materials versus Li anodes at 30 °C. Importantly, the electrochemical results disclose significantly improved cycling stability (much lower capacity fading) and high-rate performance for the treated materials compared to the untreated ones. We established a lower evolution of the voltage hysteresis with cycling for the treated cathodes compared to that for the untreated ones. Thermal studies by differential scanning calorimetry also demonstrated lower (by ∼32%) total heat released in the reactions of the materials treated with fluoroethylene carbonate (FEC)-dimethyl carbonate (DEC)/LiPF6 electrolyte solutions, thus implying their significant surface stabilization because of the surface treatment. It was established by a postmortem analysis after 400 cycles that a lower amount of transition-metal cations dissolved (especially Ni) and a reduced number of surface cracks were formed for the 2 wt % TA-treated HE-NCMs compared to the untreated ones. We consider the proposed method of surface modification as a simple, cheap, and scalable approach to achieve a steady and superior electrochemical performance of HE-NCM cathodes.

High-rate electrochemical performance of Li4Ti5O12 obtained from TiCl4 by means of a citric acid aided route

Li4Ti5O12 precursors have been synthesized by means of a citric acid aided route using TiCl4 as a raw material. The pyrolysis of the precursors has been performed in air and in argon. Comparison shows that pyrolyzing citrate precursors in argon instead of air one can obtain a material having twice smaller particle size and much better electrochemical properties (specific capacity and discharge rate). Specifically, Li||Li4Ti5O12 cells with Li4Ti5O12 pyrolyzed in argon return 148 mА·h/g upon 1.0C current load, 70 mA h/g upon 30C current load and 32 mA h/g upon 60C current load. These values exceed those obtained with a commercial Li4Ti5O12 material. For Li4Ti5O12 pyrolyzed in air, increasing discharge currents from 1.0C to 30C decreases discharge capacity from 125 to 40 mA h/g.

Improving High Rate Electrochemical Performance of Patterned Lithium Metal Anode for Lithium Secondary Batteries By Using Dual Salt Electrolyte System

Recently, demand for lithium (Li) secondary batteries has been increasing as the market for mid- to large-size batteries such as electric vehicles (EV) and energy storage systems (ESSs) is expanding. Especially in order to popularize EVs, it is essential to improve the energy density in order to secure mileage. However, using commercialized graphite as an anode material is difficult to increase energy density due to their limited capacity. Li metal is an ideal anode material due to its extremely high theoretical specific capacity (3860 mAh g-1), low density (0.59 g cm-3) and the lowest negative electrochemical potential (‒3.040 V vs. the standard hydrogen electrode). For instance, Li/air and Li/S batteries enable to increase dramatically energy density. However, Li metal has been proposed as a problem of deterioration of cell performance due to dendrite caused by charging / discharging process and battery short circuit. More importantly, Li dendrite-growth lead to safety issue, i.e., thermal runaway, causing a catastrophic satety failure accompanied by fire and smoke. To overcome this problem, many efforts have been devoted to suppress lithium dendrite-growth. Recently, we demonstrated the possibility of using mechanically surface-patterned Li-metal for Li secondary batteries. In our previous work (J. N. Park et. Al), patterned Li-metal anode showed good cycle life at low current density cycling. Still, high current density cycling showed limited cycle life because of bulky Li dendrite formation in the micro-patterned Li-metal holes. These consume more amount of electrolytes during charging/discharging processes. In this work, we applied dual salt system electrolyte on the micro-patterned Li metal to suppress mechanically bulky Li deposition in the micro-patterned Li-metal holes during charging/discharging processes. And then, their electrochemical properties are investigated in detail.

In situ LiFePO4 nano-particles grown on few-layer graphene flakes as high-power cathode nanohybrids for lithium-ion batteries

We have realized a Lithium Iron Phosphate (LFP)-graphene nanohybrid obtained by a direct LFP crystal colloidal synthesis on few-layer graphene (FLG) flakes produced by the liquid phase exfoliation (LPE) of pristine graphite. This hybrid material has been tested as a cathode in Li-ion batteries, achieving fast charge/discharge responses to high specific currents. We demonstrate a specific capacity exceeding 110 mAh g−1 at 20 C, with no electrode damaging. Our LFP-FLG electrodes display a low charge transfer resistance, chemical stability and steady electrochemical behavior even under stressful conditions, such as impulsive charges at a high-rate (5 C) and long cycles at 1 C (> 700 cycles). The LFP colloidal synthesis combined with the FLG production by LPE allows for tuning both the LFP-platelets like and FLG flake morphologies in order to promote an optimal connection between the LFP and FLG flakes, ensuring fast charge transfers and consequently high-rate electrochemical performances. The method here proposed yields a scalable production path, which can be easily extended to silicate-, phosphate- and fluorophosphates-based cathode materials for the next generation of high-power lithium batteries.

Carbon nanotubes branch on cobalt oxide nanowires core as enhanced high-rate cathodes of alkaline batteries

Directional synthesis of carbon/metal oxide core-branch arrays is of great importance for development of advanced high-rate alkaline batteries. In this work, we report a facile hydrothermal-chemical vapor deposition (CVD) method for controllable fabrication of Co3O4 @CNTs core-branch arrays. Interestingly, free-standing Co3O4 core nanowires are intimately decorated by cocoon-like branch CNTs with diameters of 20–30 nm, which act as a highly conductive network and structure stabilizer. The electrochemical performance of the designed Co3O4 @CNTs core-branch arrays are tested as cathodes of alkaline batteries. Arising from enhanced electrical conductivity, larger surface area and improved structural stability, the Co3O4 @CNTs arrays show superior high-rate electrochemical performance with a higher capacity (116 mAh g−1 at 2.5 A g−1), lower polarization and better cycling stability than the pure Co3O4 nanowires arrays (76 mAh g−1 at 2.5 A g−1). Our directional composite strategy can be extended to preparation of other carbon-based core-branch arrays for applications in electrochemical batteries and catalysis.

Naphthalene-modulated microporous carbon layers of LiFePO4 improve the high-rate electrochemical performance

Abstract Carbon layers with microporous structures fine-modulated by naphthalene (NAP) were prepared to coat on LiFePO4, aiming to enhance the Li+ diffusion coefficient for Li-ion batteries. Characterized by BET, XRD, TEM, EIS, etc., it is indicated that in the presence of NAP, the carbon-coated LiFePO4/C-NAP composites have the enlarged micropore size of 1.66 nm and the enhanced Li+ diffusion coefficient of 2.83 × 10−12 cm2 s−1, which is about five times higher than that of LiFePO4/C prepared in the absence of NAP. At a high rate of 20 C, the discharge capacity of the LiFePO4/C-NAP is up to 120.1 mA h g−1 and maintains a good retention rate of 93.2% after 400 cycles. It is suggested that the NAP-modulated carbon coating is a promising route to accelerate the Li-ion diffusion rate and enhance the electrochemical performance for lithium ion batteries.

Boron and nitrogen co-doped CNT/Li4Ti5O12 composite for the improved high-rate electrochemical performance of lithium-ion batteries

A novel Li4Ti5O12 (LTO) composite with multiwalled carbon nanotubes (CNTs) co-doped with nitrogen (N) and boron (B) (B,N-CNT), denoted N-B-C-LTO, was successfully obtained from a mixture of N,B-CNT and LTO after calcination. For comparison, LTO, C-LTO (LTO/CNT), N-doped N,C-LTO (LTO/N,CNT) and B-doped B,C-LTO (LTO/B,CNT) were also synthesized. Among the samples, N-B-C-LTO demonstrated the best performance in electrochemical measurements. The reversible capacity of N-B-C-LTO could reach 120 mAh/g, even at a rate of 20 C. After 150 cycles at 20 C, 97.5% of the capacity was retained with negligible capacity fading. The excellent electrochemical performance was possibly due to the separate forms of N and B in the co-doped CNTs, which not only maintained the benefits of the N and B additives, i.e., good electron-donating and electron-accepting capabilities, but also led to a synergistic effect from the unique electronic structure.

Structural Evolution of LixNiyMnzCo1-y-zO2 Cathode Materials during High-Rate Charge and Discharge.

Ni-rich lithium transition metal oxides have received significant attention due to their high capacities and rate capabilities determined via theoretical calculations. Although the structural properties of these materials are strongly correlated with the electrochemical performance, their structural stability during the high-rate electrochemical reactions has not been fully evaluated yet. In this work, transmission electron microscopy is used to investigate the crystallographic and electronic structural modifications of Ni-based cathode materials at a high charge/discharge rate of 10 C. It is found that the high-rate electrochemical reactions induce structural inhomogeneity near the surface of Ni-rich cathode materials, which limits Li transport and reduces their capacities. This study establishes a correlation between the high-rate electrochemical performance of the Ni-based materials and their structural evolution, which can provide profound insights for designing novel cathode materials having both high energy and power densities.

Controllable synthesis of Fe3O4 polyhedron possessing excellent high-rate electrochemical performance for lithium-ion batteries

Fe3O4 nanocrystals (NCs) composed of different proportion of {100} and {111} facets were prepared using oleic acid and decanoic acid as surfactant to mediate their growth process. It has been found that the morphology of Fe3O4 NCs can be tuned by changing the ratio of oleic acid and decanoic acid. When tested as the anode materials in LIBs, the Fe3O4 octahedrons obtained after annealing at 450°C was found to exhibit superior electrochemical performances with a high reversible capacity of 882.6mAhg−1 at 1Ag−1 over 200 cycles, whereas the Fe3O4 cubooctahedron and cubes bearing poor electrochemical performances. The present results prove that the surface structure of Fe3O4 polyhedrons significantly influence the utilization of Fe3O4 active materials and hence their electrochemical performance although the morphology will be destroyed during cycling.