Electrochemical Kinetic Properties Research Articles

Effect of Ce replacing La on the electrochemical performance of amorphous grain boundaries Mg-Ni-based materials

Aiming at enhancing the electrochemical characteristic of RE-Mg-based composite, the partial substituting La with Ce experiment in the composites was conducted, and the surface modification treatment of the alloys was performed by mechanical coating Ni. By means of mechanical trituration, The La10-xCexMg80Ni5 (x = 0–2) + y wt% Ni (y = 50–200) compound materials which have the structures of nanocrystalline and amorphous were synthesized. In order to make sense of the principle action of Ce and Ni elements in structural and electrochemical properties of the material, some deep research were carried out. According to the final results, the as-milled composites have the electrochemical hydrogen absorption and hydrogen desorption abilities at room temperature. Having no use for activation, the as-milled composites can reach the maximum discharge capacities when the first cycling was carried out. With the Ni value x changed from 50 to 200, the discharge capacity was varied from 70.5 mAh/g to 902.1 mAh/g; moreover, the capacity retention rate at 20th cycle (S20) and high rate dischargeability (HRD) of the (x = 0) composite were heightened from 67.2 % to 82.3 %, from 50.6 % to 55.7 % respectively. The composites' (y = 100) discharge capacity has a maximum value 118.5 mAh/g when the Ce value x is 1. The capacity retention rate (S20) is enhanced from 53.3 % to 68.5 % by lifting Ce content from x = 0 to x = 2. what's more, the high-rate discharge ability (HRD), the electrochemical impedance spectrum (EIS), potentiodynamic polarization curves, and potential-step measurements all intimate that substituting La with Ce clearly promotes the composites' electrochemical kinetic properties, but maximum values emerge only when the x value is 1.

A Comparative Study of the Structural and Electrochemical Properties of Na3V2(PO4)3/C Cathode Materials for Na‐ion Batteries Prepared by Sol‐Gel vs. Solid‐State Methods

AbstractNa‐ion batteries have attracted much attention as one of the most promising alternatives to lithium‐ion batteries. Na3V2(PO4)3 has been widely investigated as a cathode material for Na‐ion batteries because of its high structural and thermal stability, leading to high cycling performance and safety. The cathode material also possesses a three‐dimensional open framework and consequently provides high ionic conductivity, as well as high‐rate capability. However, the cathode type experiences poor electronic conductivity, affecting its electrochemical properties. It is well established that preparation methods have remarkable effects on the crystal structure and morphology of electrode materials, altering their electrochemical performance. Thus, this work focuses on a comparative study of the morphology, structures, electrochemical performance, and kinetic properties of Na3V2(PO4)3/C cathodes prepared by sol‐gel and solid‐state methods, which are simple and scalable. The results reveal that sol‐gel and solid‐state reaction processes provide Na3V2(PO4)3/C cathode materials with different structural and morphological characteristics, significantly affecting their electrochemical performance and kinetic properties. This is a crucial key to finding a proper synthesis method to achieve Na3V2(PO4)3/C with high performance for commercial large‐scale production.

Synergistic Corrosion Engineering on Metallic Manganese Toward High‐Performance Electrochemical Energy Storage

AbstractMnO/rGO with enhanced electrochemical kinetic properties is widely investigated as electrode for high‐performance electrochemical energy storage (EES) devices. However, the synthesis of MnO/rGO via traditional methods suffers from low atomic utilization and complex techniques that are undesirable for practical implementation. Different from existing fabrication strategies, here using metallic manganese as Mn source, a novel, eco‐friendly, and corrosion engineering‐based approach to address the above issues is demonstrated. It is thermodynamically feasible as supported by the E‐pH analysis and for the first time, a significant synergetic effect is observed between NH4+ and GO in strengthening the metallic Mn corrosion reaction. Particularly, in the “ammonia circulation” process, the NH3 molecule, derived from NH4+, acts as a “carrier” for Mn2+ to facilitate its transfer by forming [Mn(NH3)2]2+, which effectively prevents “in situ corrosion”. The phase and structure evolution during the reaction are clarified, and the synergistic corrosion mechanism is also proposed. Benefiting from the efficient lithium‐ion evolution kinetics, Mn─O─C bond formed between MnO and rGO and outstanding structural integrity, the resultant MnO/rGO demonstrates exceptional EES performances in both lithium‐ion batteries and lithium‐ion capacitors. This finding will offer potential for mild, cost‐effective, and environmentally friendly fabrication of other graphene‐based metal oxide electrodes using corrosion engineering.

Simultaneous Mn and Cl doping on Na3V2(PO4)3 with high performance for full sodium-ion batteries.

Nowadays, the poor conductivity and unstable structure have become obstacles for the popularization of Na3V2(PO4)3 (NVP). In the current work, a dual-modified Mn0.1Cl0.3-NVP composite doped with Mn and Cl is prepared by a facile sol-gel method. When Mn2+ with a large ionic radius replaces small V3+, it can improve the stability of the NVP crystal structure. In addition, the replacement of V3+ by Mn2+ in a low valence state can generate redundant hole carriers, which is conducive to the rapid transport of electrons. The substitution of PO43- by Cl-, which is more electronegative, can reduce the impedance and facilitate the movement of Na+. Owing to the synergistic effect of Mn and Cl co-substitution, the structural stability of NVP was systematically enhanced, and the electron transfer and ion diffusion were effectively improved. Consequently, the optimized Mn0.1Cl0.3-NVP sample demonstrated superior electrochemical performance and kinetic properties. It exhibited a high reversible capacity of 109.2 mA h g-1 at 0.1C. Even at 15 and 30C, high discharge capacities of 70.3 mA h g-1 and 68.2 mA h g-1 were observed after 2000 cycles with capacity retention above 80%. Moreover, it delivered remarkable capacities of 77.1 and 73.4 mA h g-1 at 100 and 200C with retained capacity values of 50.3 and 47 mA h g-1, respectively, after 2000 cycles. Furthermore, the assembled Mn0.1Cl0.3-NVP//HC full cell delivered a high value of 94.7 mA h g-1 and lit LED bulbs, indicating its excellent application potential.

Electropolymerization nanoarchitectonics of polyaminoanthraquinone/carbon cloth flexible electrode with nano-spines array structure for high-performance supercapacitor

The construction of integrated flexible electrode materials with high density active sites, satisfactory and ideal nanostructures is of great significance for flexible supercapacitors, but it is still a huge challenge. Herein, we targeted select 1,5-diaminoquinone (DAAQ) with high theoretical capacity as monomer and used in-situ electropolymerization strategy to prepare the binder-free flexible poly (1,5-diaminoquinone)/carbon cloth electrode (EP-PDAAQ/CC). In the SEM images of EP-PDAAQ/CC, PDAAQ is uniformly covered on CC with nano-spines array structure. DFT calculations further demonstrate that the polymerization process can effectively reduce band gaps and improve the overall conductivity of electrode materials. Subsequently, we systematically investigate the core influencing factors affecting the electropolymerization process, such as monomer concentration, supporting electrolyte types, polymerization voltage and charge density. Under optimal preparation conditions, we found that EP-PDAAQ/CC exhibited a higher energy storage capacity (about 2.2 times) than PDAAQ/CC (prepared by chemical oxidative polymerization). And the flexible electrodes show the maximum specific capacitance of 645 mF cm−2 at 1 mA cm−2 and superior cycling stability (83.5 % of the initial capacity after 10,000 cycles). The kinetic analysis shows that the capacitance contribution of EP-PDAAQ/CC flexible electrode is as high as 78.1 % at 100 mV s−1, exhibiting fast electrochemical kinetic properties. Finally, we assemble the symmetrical supercapacitor and test its practical application.

Strengthening Fe(II)/Fe(III) Dynamic Cycling by Surface Sulfation to Achieve Efficient Electrochemical Uranium Extraction at Ultralow Cell Voltage.

Electrochemically mediated Fe(II)/Fe(III) redox-coupled uranium extraction can efficiently reduce the cell voltage of electrochemical uranium extraction (EUE). How to regulate the surface structure to enhance the uranium acyl ion adsorption capacity and strengthen the Fe(II)/Fe(III) redox cycle process is crucial for EUE. In this work, we developed surface sulfated nanoreduced iron (S-NRI) for EUE and exhibited improved properties for EUE at an ultralow cell voltage (-0.1 V). Compared with a nanoreduced iron (NRI) adsorbent, S-NRI displayed faster electrochemical extraction kinetics properties and higher extraction efficiency and capacity for uranium. In a more complex seawater electrolyte containing uranyl ion concentration ranging from 1 to 20 ppm, the removal efficiency could reach almost ∼100% after EUE for 24 h. At a higher 50 ppm uranium acyl ion concentration in a seawater electrolyte, S-NRI exhibited higher extraction capacity (755.03 mg/g), which is better than 528.53 mg/g of NRI at a cell voltage of -0.1 V. Outstanding EUE property could be attributed to the fact that sulfate species (M-SO42-) on the S-NRI surface not only enhanced selective adsorption of uranyl ions but also strengthened the Fe(II)/Fe(III) redox cycle, which accelerated electron transfer between Fe(II) and U(VI), promoted the regeneration of Fe(II) active sites, and finally enhanced the EUE property.

Novel Spinel Multicomponent High‐Entropy Oxide as Anode for Lithium‐Ion Batteries with Excellent Electrochemical Performance

High‐entropy spinel oxides (HESOs) are a promising anode material for lithium‐ion batteries (LIBs) due to their high structural stability and theoretical capacity. However, the development of HESOs is mainly limited to five‐component equimolar systems, and the lithium‐storage mechanism is still controversial. A nonequimolar six‐component oxide, (CoMnZnNiMg)2CrO4, is synthesized using a solution combustion method. The prepared material is a HESOs, consisting of homogeneous nanoparticles with a mesoporous structure. (CoMnZnNiMg)2CrO4 exhibits high rate performance (371 mAh g−1 at 2000 mA g−1) and long cycling stability (608 mAh g−1 after 200 cycles at 200 mA g−1). A variety of constituent elements exist uniformly and stably in a spinel phase due to the high‐configuration entropy‐induced phase‐stabilization effect, and the synergistic effect of the various valence elements in the material results in the excellent electrochemical performance. The outstanding electrochemical kinetic properties of the HESOs are mainly attributed to the high‐ionic‐diffusion coefficients and pseudocapacitance contributions. In addition, the HESOs electrodes undergo an amorphous conversion during the initial charge/discharge process. It is shown that the rational design and modulation of the active component is an effective way to obtain high‐performance HESOs for LIBs.

Lignin-based nitrogen/sulfur dual-doped nanosheets decorated with Co1−xS nanoparticles as efficient bifunctional oxygen electrocatalysts

The development of efficient, cost-effective, bifunctional cathode catalyst materials to replace precious metals is highly attractive for the fabrication of Zn–air battery. Here, the three–dimensional N and S co–doped carbon nanosheets loaded with cobalt sulfide nanoparticles (Co1-xS@SNFC) for bifunctional oxygen electrocatalysis were synthesized with Co(NO3)2·6H2O as the Co source, lignin as the carbon source, thiourea as the nitrogen/ sulfur source, and MgO as the template. The synergistic effect of multiple active sites gives the Co1-xS@SNFC fast electrochemical kinetic properties and excellent stability to oxygen reduction reactions (ORR) and oxygen evolution reactions (OER). The half-wave potential and overpotential of Co1-xS@SNFC were 0.84 mV and 306 mV, respectively, which is closed to commercial noble metal catalysts. In addition, Co1-xS@SNFC exhibited four–electron transfer characteristics and ultra–low tafel slope. Compared with commercial Pt/C, the Zn–air battery assembled from Co1-xS@SNFC exhibited a low voltage gap of polarization curve (0.75 V) between charging and discharge and high power density (207 mWcm−2) in alkaline electrolyte. This work developed a green and novel fabrication approach for the synthesis of bifunctional electrocatalyst and provides a new idea for high-value utilization of biomass.

Surface modification with cobalt oxide nanocluster for enhanced surface oxygen exchange reactions of GDC-LSCF membrane: fabrication, electrochemical kinetic properties, and stability

Surface modification with cobalt oxide nanocluster for enhanced surface oxygen exchange reactions of GDC-LSCF membrane: fabrication, electrochemical kinetic properties, and stability

Design and fabrication of high-entropy oxide anchored on graphene for boosting kinetic performance and energy storage

The rock salt structure of high entropy oxide (HEO) (Mg 0.2 Co 0.2 Ni 0.2 Cu 0.2 Zn 0.2 )O has promising prospects for energy materials. Here, we prepare HEO and calculate the entropy value S m i x ≥ 1.5R (R represents the gas constant), thus proving that HEO is obtained. In addition, we design and obtain HEO@G (HEO@Graphene) through the surface modification of HEO with graphene, which is analysed by X-ray diffraction, X-ray photoelectron spectroscopy, and high-resolution transmission electron microscopy to reveal the rock salt structure of HEO@G and the formation of a planar layer architecture on the surface of HEO by graphene. The electrode well design with HEO@G as the anode material for lithium-ion batteries provides a high capacity of 1225 mA h g −1 in the first discharge at 100 mA g −1 and maintains a discharge capacity of ∼950 mA h g −1 after 200 cycles. A reversible cycling capacity of 460 mA h g −1 is obtained under the condition of multiple cycles at high speed. In terms of expansion, electrochemical impedance spectrometry and pseudocapacitance investigations deeply demonstrate that the addition of graphene enhances the diffusion dissemination coefficient of lithium ions in the composite electrode and changes the electrochemical kinetic properties of the composite anode. Such a modification approach for HEO will provide a reference in energy storage applications.

Key to intimately coupling metal chalcogenides with a carbon nanonetwork for potassium-ion storage

An interfacial engineering strategy is proposed to intimately couple metal chalcogenides with multidimensional carbon nanonetworks, which significantly improves their potassium-ion storage performances and electrochemical kinetic properties.

Electrochemical extraction kinetics of Nd on reactive electrodes

• Pyroprocessing technology is a promising technology for the reprocessing of spent fuel. • It is critical to pursue electrode materials with high An / Ln separation efficiency. • The electrochemical reduction of Nd 3+ on the W electrode is a two-step reduction process. • The kinetic properties of Nd 3+ on W, reactive electrodes were measured. • Cd was evaluated as a favorable electrode material for electrochemical extract ion of Nd. Pyroprocessing technology with molten salt electrolysis as the core is a promising technology for the reprocessing of spent fuel. In this work, the electrochemical reduction mechanism and kinetic properties of Nd 3+ on various electrodes (inert W and reactive Al, Ga, Bi, Cd, Zn, Pb, and Sn electrodes) were systematically investigated and compared in LiCl-KCl eutectic melts using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and Tafel techniques. The electrochemical reduction of Nd 3+ was a two-step process on the W electrode including Nd 3+ →Nd 2+ and Nd 2+ →Nd, while it became a one-step process involving three electrons on the reactive electrodes with obvious depolarization effects. Furthermore, the connections between the reduction potentials of Nd 3+ on these reactive cathodes and the formation energies of the electrode-rich alloy phases (Al 11 Nd 3 , Cd 11 Nd, Pb 3 Nd, Zn 17 Nd 2 , Ga 6 Nd, Sn 3 Nd, BiNd 2 ) were established. After evaluating the physicochemical, depolarization and kinetic properties of these reactive electrodes, liquid Cd was considered as the most favorable material for the electrochemical extraction of Nd. In addition, Al, Cd, and Bi are also promising candidates for An / Ln separation.

Preparation of porous polyaniline/RGO composite and its application in improving the electrochemical properties of Co9S8 hydrogen storage alloy

The sea urchin-like porous polyaniline (PPANI) is prepared by a facile saturated solution synthetic route. The porous polyaniline/reduced graphene oxide composite (PPANI/RGO) is synthesized via a solution-assisted self-assembly method. Mechanical alloying is used to obtain the Co9S8 alloy. Composites of Co9S8 mixed with PPANI and PPANI/RGO are fabricated through ball-milling to improve the electrochemical performance of Co9S8 alloy. The structures and morphologies of the composite alloys are studied by XRD, SEM and BET. The electrochemical properties of alloys are tested as negative electrodes of Ni-MH batteries by the LAND CT2001A tester and three-electrode system. For comparison, Co9S8 alloys doped with conventional polyaniline (CPANI) and RGO are also prepared. Ultimately, the Co9S8 + PPANI composite shows preferable discharge capacity compared with CPANI modified Co9S8 and matrix alloy. In addition, the PPANI/RGO composite modified Co9S8 electrode exhibits superior discharge capacity than separate PPANI and RGO coated alloys. A maximum discharge capacity (701.4 mAh/g) is achieved for Co9S8 + PPANI/RGO electrode. Furthermore, the Co9S8 + PPANI/RGO composite materials exhibit preferable high-rate dischargeability, improved corrosion and oxidation resistance and excellent kinetics properties. The PPANI material with special porous structure and unique morphology displays better performance than CPANI. Moreover, a synergistic effect between PPANI and RGO species in the PPANI/RGO material may provide a rapid passageway for charge transfer and accelerate the hydrogen transmission. Accordingly, the electrochemical activity and kinetic properties are improved for Co9S8 + PPANI/RGO composite electrode.

Fabrication of Mesoporous Carbon CMK-3 Modified Co0.9Cu0.1Si Alloy for Electrochemical Hydrogen Storage

Mechanical alloying is used to prepare the Co[Formula: see text]Cu[Formula: see text]Si alloy. Mesoporous silicon SBA-15 is employed as the template to synthesize mesoporous carbon CMK-3. For the purpose of improving the electrochemical properties of Co[Formula: see text]Cu[Formula: see text]Si alloy, Co[Formula: see text]Cu[Formula: see text] CMK-3 ([Formula: see text], 6%, 9% and 12% mass fraction) alloys are fabricated via ball-milling. As the negative electrodes of Ni–MH batteries, the discharge capacities of alloys are tested by the LAND CT2001A tester and three-electrode system. Finally, the composite alloys show different properties for hydrogen storage. A maximum discharge capacity (558.7[Formula: see text]mAh/g) is achieved for Co[Formula: see text]Cu[Formula: see text] CMK-3 electrode. Superfluous CMK-3 is not beneficial to enhance the discharge capacity of Co[Formula: see text]Cu[Formula: see text]Si alloy. Moreover, Co[Formula: see text]Cu[Formula: see text] CMK-3 electrodes exhibit better corrosion and oxidation resistance, which leads to higher capacity retention for CMK-3/Co[Formula: see text]Cu[Formula: see text]Si composites. The comparative studies on HRD and kinetic properties of Co[Formula: see text]Cu[Formula: see text]Si and Co[Formula: see text]Cu[Formula: see text] CMK-3 are also conducted. The [Formula: see text] of Co[Formula: see text]Cu[Formula: see text]Si alloy reduces and [Formula: see text] increases after doping of CMK-3. The special structural characteristics and higher conductivity of CMK-3 can offer more electrochemical active sites and accelerate hydrogen diffusion. Accordingly, the electrochemical activity and kinetic properties are enhanced for CMK-3/Co[Formula: see text]Cu[Formula: see text]Si composites.

Space and interface confinement effect of necklace-box structural FeS2/WS2 carbon nanofibers to enhance Na+ storage performance and electrochemical kinetics

Necklace-box structural FeS2/WS2 carbon nano-composite fibers (NB FeS2/WS2-CNFs) are fabricated by electrospinning-sulfuration-hydrothermal process. NB FeS2/WS2-CNFs exhibit the spatial confined structure, which is able to restrain volume expansion effectively in the process of Na+ intercalation/deintercalation and improve the cycling stability and rate performance. NB FeS2/WS2-CNFs exhibit remarkable initial coulombic efficiency (ICE = 87.0%) and stable long cycle (~422.6 mA h g−1 at 0.5 A g−1 after 500 cycles) for sodium storage capability. The heterojunction interface between FeS2 and WS2 can alleviate the damage of the micro-crystal plane and enhance electrochemical kinetic process. The structure evolution and mechanism of sodium storage are explored by ex-situ methods, which further confirm the spatial and interface confinement effect distinctly. In addition, the electrochemical kinetic properties of lithium-ion batteries (LIBs), sodium-ion batteries (SIBs) and potassium-ion batteries (PIBs) are compared, thereby revealing the energy storage mechanism and different ion migration modes of the three batteries. This work provides a guide for the synthesis of bimetallic compounds based on the spatial confinement and heterojunction interface confined strategy that efficiently improves energy storage performance of electrode material.

Fabrication of porous polyaniline/MWCNTs coated Co9S8 composite for electrochemical hydrogen storage application

Mechanical alloying is used to obtain the Co9S8 hydrogen storage material. The porous polyaniline (PPANI) with sea urchin-like morphology is synthesized via a facile saturated solution synthetic route. The porous polyaniline/multi-walled carbon nanotubes (PPANI/MWCNTs) composite is prepared by a solution-assisted self-assembly route. In order to improve the electrochemical performance of Co9S8, composites of Co9S8 doped with PPANI, MWCNTs and PPANI/MWCNTs are fabricated by ball-milling. As the negative electrodes of Ni-MH batteries, the electrochemical properties of samples are measured utilizing a three-electrode system with the LAND CT2001A tester. Eventually, the composites exhibit superior discharge capacities than original Co9S8 material. Moreover, PPANI/MWCNTs coated Co9S8 electrode shows preferable discharge capacity compared with single MWCNTs or PPANI modified Co9S8. The Co9S8 + PPANI/MWCNTs electrode obtains a maximum discharge capacity of 689.2 mAh/g. In addition, the better high-rate dischargeability, enhanced corrosion resistance and preferable kinetic performance are also obtained for Co9S8 + PPANI/MWCNTs. The improved electrochemical activity and kinetic properties of Co9S8 are attributed to the synergistic effect between PPANI and MWCNTS species, which may further accelerate the hydrogen transmission and promote the charge transfer during the charge/discharge process.

Synthesis of yolk‐shell‐structured iron monosulfide‐carbon microspheres and understanding of their conversion reaction for potassium‐ion storage

Nanostructured transition metal chalcogenides (TMCs) have attracted attention as potential anode materials owing to the anticipation of next-generation battery systems, particularly potassium-ion batteries (PIBs). In this study, the electrochemical reaction mechanism of iron monosulfide (FeS) with potassium ions was systemically investigated for the first time. To enhance the electrochemical properties by improving the structural stability and electrical conductivity during cycling, rational strategies of introducing a yolk-shell architecture via an aerosol process and pitch solution infiltration were applied, resulting in the formation of yolk-shell-structured FeS/pitch-derived carbon composite microspheres (Y-FeS@C). From in situ and ex situ investigations of electrodes in fully discharged and charged states, the following reaction mechanism was determined from the second cycle onward: 4Fe + 4K2S ↔ KxFe2S3 + FeS + Fe + (8 − x)K+ + (8 − x)e−. The inhibition of substantial FeS crystal growth thanks to the pitch-derived carbon encapsulation as well as the formation of metallic Fe after the initial conversion reaction contributed to the excellent electrochemical kinetic properties of Y-FeS@C. Y-FeS@C showed stable cycle performance (256.5 mA h g−1 for the 100th cycle at 0.5 A g−1) and high rate capability (113.8 mA h g−1 at 5.0 A g−1) as an anode material for PIBs.

Effect of the Mn/V ratio to optimize the kinetic properties of Na3+xMnxV1-xCr(PO4)3 positive electrode for sodium-ion batteries

Several samples of the Na3+xMnxV1-xCr(PO4)3 series, in which the Mn/V ratio was allowed to vary from 0 to 1, are structural, chemical, and morphologically characterized using helpful solid-state techniques such as XRD diffraction, electron microscopy, and Raman and XPS spectroscopies. These cathode materials are tested by both galvanostatic and voltammetric methods to unveil their electrochemical response. The intermediate compositions showed a biphasic transition and a combination of the profiles belonging to the end member of the series: V4+/V3+ Mn3+/Mn2+ and Mn 4+/ Mn 3+ redox couples. The correlation of apparent diffusion coefficients and the cell internal resistance allowed us to conclude the beneficial effect of intermediate Mn-V composition (x = 0.4) to optimize the electrochemical performance and kinetic properties in sodium-ion cells.

Structure and electrochemical characteristics of Mg–Ti–Ni-based electrode alloys synthesized by mechanical milling

The vacuum induction melting was adopted to fabricating Mg50−xTixNi45Al3Co2 (x = 0, 1, 2, 3, 4 at.%) composites protected by the high-purity helium atmosphere. Subsequently, the surface modification treatment of the as-cast alloys was carried out by mechanically coating nickel. The amorphous and nanocrystalline Mg50−xTixNi45Al3Co2 (x = 0–4) + 50 wt.% Ni hydrogen storing alloys as the negative materials in batteries were prepared through ball milling, and the influences of milling time and Ti dosage on the structure and electrochemical hydrogen storing behaviors of the corresponding samples were studied in detail. The electrochemical testing reveals that the as-milled alloys have excellent performances and can finish the electrochemical hydrogenation and dehydrogenation at indoor temperature. In the first cycle without activation, the ball milling alloy obtains the maximum value of discharge capacity. Discharge capacity and cyclic steadiness of the composites conspicuously grow as Ti content and milling duration increase. Concretely, the capacity retaining rate at 100th cycle and the discharge capacity of 30 h milling samples augment from 53% to 78% and from 435.2 to 567.2 mAh/g with changing Ti content from 0 to 4. The same performances of the alloy (x = 4) are enhanced from 61% to 78% and from 379.9 to 567.2 mAh/g, respectively, with extending milling duration. Moreover, high rate discharge ability, potential-step measurements, potentiodynamic polarization curves and electrochemical impedance spectrum manifest that the electrochemical kinetics properties can achieve significant amelioration as Ti content varies and milling duration is extended.

Ionic liquid assisted hydrothermal synthesis of 0.5Li2MnO3·0.5LiNi0.5Mn0.5O2 for lithium ion batteries

The uniform lithium-rich manganese-based 0.5Li2MnO3·0.5LiNi0.5Mn0.5O2 cathode materials are synthesized by a hydrothermal strategy with assistant of 1-butyl-3-methylimidazolium chloride ([BMIm]Cl) ionic liquid. The microstructures and electrochemical performances of the prepared cathode materials are characterized by XRD, SEM, TEM and electrochemical measurements. Compared with the original sample, the unique micro-morphology and better layered structure and less cation mixing of the obtained compounds with [BMIm]Cl ionic liquid give the material a sufficient contact between the solid/liquid interface (electrode and electrolyte) and facilitated the process of Li+ intercalation/deintercalation, which availing to improved electrochemical kinetics properties with excellent rate capability and remarkable cycling stability. The analysis of the kinetics of electrode reaction (EIS) proved that the charge transfer resistance value can be decreased by adding appropriate amount of [BMIm]Cl ionic liquid, and thus reduce the diffusion pathways of Li+ ions and electrons, which is well consistent with the rate capability test results. Specifically, when the amount of the [BMIm]Cl ionic liquid reaches 0.5 g, the 0.5Li2MnO3·0.5LiNi0.5Mn0.5O2 exhibited a higher initial capacity of 269.7 mAh g−1, and the capacity retention after 65 cycles was 93.0%.