Nanoparticles constructed mesoporous coral-like Mn2O3 as high performance anode for lithium-ion batteries

As well established, the morphology and architecture of electrode materials greatly contribute to the electrochemical properties. Herein, a novel structure of mesoporous coral-like manganese (III) oxide (Mn₂O₃) is synthesized via a facile solvothermal method coupled with the carbonization under air. When fabricated as anode electrode for lithium-ion batteries (LIBs), the as-prepared Mn₂O₃ exhibits good electrochemical properties, showing a high discharge capacity of 1090.4 mAh g^?1 at 0.1 A g^?1, and excellent rate performance of 410.4 mAh g^?1 at 2 A g^?1. Furthermore, it maintains the reversible discharge capacity of 1045 mAh g^?1 at 0.1 A g^?1 after 380 cycles, and 755 mAh g^?1 at 1 A g^?1 after 450 cycles. The durable cycling stability and outstanding rate performance can be attributed to its unique 3D mesoporous structure, which is favorable for increasing active area and shortening Li⁺ diffusion distance.     

Phase structure and electrochemical properties of Ml1?xMgxNi2.78Co0.50Mn0.11Al0.11 hydrogen storage alloys

The effect of magnesium content on the phase structure and electrochemical properties of Ml_1−x Mg _x Ni_2.78Co_0.50Mn_0.11Al_0.11 (x = 0.05, 0.10, 0.20, 0.30) hydrogen storage alloys was investigated. The results of X-ray diffraction reveal that all the alloys consist of the major phase (La, Mg)Ni₃ and the secondary phase LaNi₅. With increase in x, the relative content of the (La, Mg)Ni₃ phase increases gradually, and the maximum capacity and low temperature dischargeability of the alloy electrodes first increase and then decrease. When x is 0.20, the discharge capacity of the alloy electrode reaches 363 mAh g⁻¹ at 293 K and 216 mAh g⁻¹ at 233 K, respectively. The high rate dischargeability of the alloy electrodes increases with increase in x. When the discharge current density is 1200 mA g⁻¹, the high rate dischargeability of the alloy electrodes increases from 22.0% to 50.4% with x increasing from 0.05 to 0.30. The cycling stability of the electrodes decreases gradually with increase in magnesium content.     

Niobium doping of Li1.2Mn0.54Ni0.13Co0.13O2 cathode materials with enhanced structural stability and electrochemical performance

Lithium-rich layered oxides with high energy density have been intensively investigated as advanced lithium-ion batteries cathode materials. However, capacity degradation and voltage decay caused by irreversible lattice oxygen loss and structural transformation during cycling restrict their application. Herein, we proposed a high valance cations Nb⁵⁺ doping strategy and synthesized a series of Li_1.2Mn_0.54-x/3Ni_0.13-x/3Co_0.13-x/3Nb_xO₂ (x = 0, 0.01, 0.02 and 0.03) cathode materials. The effects of Nb⁵⁺ doping on crystallographic structure and electrochemical property were systematically studied. In virtue of the large ionic radii and strengthened Nb–O bonds, the doped samples present commendable structural stability and expanded interlayer spacing for Li-ions migration, which ensures the upgraded cyclic stability and rate performance. In particular, the electrode with x = 0.02 delivers a discharge specific capacity of 265.8 mAh g^-1 at 0.2 C with decelerated voltage decay, while 86.9% capacity are remained after long-term cycles. Moreover, excellent discharge specific capacity of 153.4 mAh g⁻¹ is still attained at 5 C accompanied with enhanced Li-ion diffusion kinetics.     

Rice husk-derived SiOx@carbon nanocomposites as a high-performance bifunctional electrode for rechargeable batteries

This paper we use ZnCl₂ to activates and reduces rice husks to produce SiO_x@N-doped carbon core-shell nanocomposites with inner voids is a facile and effective strategy to improve the electrochemical performance. As an anode material for the lithium-ion batteries, the composites exhibit a high reversible capacity (1315 mAh g⁻¹ after 100 cycles at 100 mA g⁻¹) and long-term stability (584 mAh g⁻¹ after 500 cycles at 500 mA g⁻¹). Such outstanding cycling stability is attributed to the small size of the SiO_x particles with inner voids and the carbon layer coating can guarantee good structural integrity for long cycle stability. As a cathode material for Li–S batteries, the composite displays a high capacity and good stability (675 mAh g⁻¹ after 100 cycles at 0.1C). Its good performance and facile preparation will improve the utilization of rice husk waste.     

Direct-hydrothermal synthesis of LiFe<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>Mn<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>PO<Subscript>4</Subscript> cathode materials

Carbon free LiFe_1−x Mn _x PO₄ (x = 0, 0.05, 0.1, 0.2, 0.4) cathode materials were prepared by a direct-hydrothermal process at 170 °C for 10 h. The structural and electrochemical properties of the samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), charge–discharge experiments, cyclic voltammetry (CV) and alternating current (AC) impedance spectroscopy. The electrochemical performance of LiFePO₄ prepared in this manner showed to be positively affected by Mn²⁺-substitution. Among the Mn²⁺-substitution samples, the LiFe_0.9Mn_0.1PO₄ exhibited an initial discharge capacity of 141.4 mA h g⁻¹ at 0.1 C, and the capacity fading is only 2.7% after 50 cycles.     

Lithium storage performance of carbon nanotubes prepared from polyaniline for lithium-ion batteries

Carbon nanotubes with large surface area and surface nitrogen and oxygen functional groups are prepared by carbonizing and activating of polyaniline nanotubes, which is synthesized by polymerization of aniline with the self-assembly method in aqueous media. The physicochemical properties of the carbon nanotubes are characterized by scanning electron microscope, transmission electron microscopy, X-ray diffraction, Brunauer–Emmett–Teller, elemental analyses and X-ray photoelectron spectroscopy measurements. The surface area and pore diameter are 618.9 m² g⁻¹ and 3.10 nm. The electrochemical properties of the carbon nanotubes as anode materials in lithium ion batteries are evaluated. At a current density of 100 mA g⁻¹, the activated carbon nanotube shows an enormously first discharge capacity of about 1370 mAh g⁻¹ and a charge capacity of 907 mAh g⁻¹. After 20 cycling tests, the activated carbon nanotube retains a reversible capacity of 728 mAh g⁻¹. These indicate it may be a promising candidate for an anode material for lithium secondary batteries.     

Synthesis and characterization of 5?V LiCoxNiyMn2?x?yO4 (x?=?y?=?0.25) cathode materials for use in rechargeable lithium batteries

Double doped spinel LiCo _x Ni _y Mn_2−x−y O₄ (x = y = 0.25) have been synthesised via sol–gel method using different chelating agents viz., acetic acid, maleic acid and oxalic acid to obtain 5 V positive electrode material for use in lithium rechargeable batteries. The sol–gel route endows lower processing temperature, lesser synthesis time, high purity, better homogeneity, good control of particle size and surface morphology. Physical characterizations of the synthesized powder were carried out using thermo-gravimetric and differential thermal analysis (TG/DTA), X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The electrochemical behaviour of the calcined samples has been carried out by galvanostatic charge/discharge cycling studies in the voltage range 3–5 V. The XRD patterns reveal crystalline single-phase spinel product. SEM photographs indicate micron sized particles with good agglomeration. The charge–discharge studies show LiCo_0.25Ni_0.25Mn_1.5O₄ synthesized using oxalic acid to be as a promising cathode material as compared to other two chelating agents and delivers average discharge capacity of 110 mA h g⁻¹ with low capacity fade of 0.2 mA h g⁻¹ per cycle over the investigated 15 cycles.     

Synthesis of LiFe0.4Mn0.6?xNixPO4/C by co-precipitation method and its electrochemical performances

LiFe_0.4Mn_0.6−x Ni _x PO₄/C(x = 0, 0.05, 0.1, and 0.2) composite cathode materials for lithium ion batteries have been prepared by the co-precipitation method using oxalic acid as a precipitator. The structure and morphology of precursors and products have been investigated. Electrochemical tests demonstrate that LiFe_0.4Mn_0.55Ni_0.05PO₄ can deliver a specific capacity of 142 mAh g⁻¹ at 0.1 C, and retains 133 mAh g⁻¹ after 60 cycles. The rate performance of LiFe_0.4Mn_0.6PO₄ is obviously improved by doping Ni. The capacity of LiFe_0.4Mn_0.55Ni_0.05PO₄ at 2 C is 110 mAh g⁻¹.     

Investigation of lithium ion kinetics through LiMn2O4 electrode in aqueous Li2SO4 electrolyte

Spinel LiMn₂O₄ was prepared by sol–gel method and characterized by Fourier transform infrared spectroscopy, X-ray diffraction, and scanning electron microscope. Cyclic voltammogram, galvanostatic charge/discharge testing, and electrochemical impedance spectroscopy (EIS) techniques were employed to evaluate the electrochemical behaviors of LiMn₂O₄ in 1 M Li₂SO₄ aqueous solution. Two redox couples at E _SCE = 0.78/0.73 and 0.91/0.85 V were observed, corresponding to those found at E _Li/Li ⁺= 4.05/3.95 and 4.06/4.18 V in organic electrolyte. The discharge capacity of pristine LiMn₂O₄ in aqueous electrolyte was 57.57 mAh g⁻¹, and the capacity retention of the electrode is 53.7 % after 60 cycles. Only one semicircle emerged in EIS at different potentials in aqueous electrolyte, while three semicircles were observed in organic electrolytes. There was no solid electrolyte interface film on the surface of spinel LiMn₂O₄ electrode in aqueous electrolyte. The change of kinetic parameters of lithium ion insertion in spinel LiMn₂O₄ with potential in aqueous electrolyte for initial charge process was discussed in detail, and a suitable model was proposed to explain the impedance response of the insertion materials of lithium ion batteries in different electrolytes.     

Enhanced electrochemical performance of FeS<Subscript>2</Subscript> synthesized by hydrothermal method for lithium ion batteries

Iron disulfide (FeS₂) powders were successfully synthesized by hydrothermal method. Cetyltrimethylammonium bromide (CTAB) had a great influence on the morphology, particle size, and electrochemical performance of the FeS₂ powders. The as-synthesized FeS₂ particles with CTAB had diameters of 2–4 μm and showed a sphere-like structure with sawtooth, while the counterpart prepared without CTAB exhibited irregular morphology with diameters in the range of 0.1–0.4 μm. As anode materials for Li-ion batteries, their electrochemical performances were investigated by galvanostatic charge–discharge test and electrochemical impedance spectrum. The FeS₂ powder synthesized with CTAB can sustain 459 and 413 mAh g⁻¹ at 89 and 445 mA g⁻¹ after 35 cycles, respectively, much higher than those prepared without CTAB (411 and 316 mAh g⁻¹). The enhanced rate capability and cycling stability were attributed to the less-hindered surface layer and better electrical contact from the sawtooth-like surface and micro-sized sphere morphology, which led to enhanced process kinetics.     

Agar-assisted sol-gel synthesis and electrochemical characterization of TiNb2O7 anode materials for lithium-ion batteries

TiNb₂O₇ powders are synthesized via a newly developed agar-assisted sol-gel process for the first time. Phase-pure TiNb₂O₇ powders are obtained upon calcination at 800 °C. On contrast, TiNb₂O₇ powders synthesized via the conventional solid-state method require high calcination temperature at 1100 °C for the complete compound formation. The samples synthesized with agar improve the morphology with submicron-sized particles. The formed porous structure is favorable for enhancing the electrochemical kinetics due to the large contact area between the electrode and the electrolyte. Based on the electrochemical active surface area analysis, the electrical double-layer capacitance of TiNb₂O₇ powders synthesized via both the agar-assisted and the solid-state method is 145 mF cm^?2 and 22 mF cm^?2, respectively. The electrochemical active surface area of the sample prepared via the agar-assisted method is higher than that of the sample prepared via the solid-state method. The TiNb₂O₇ sample synthesized via the agar-assisted process yields 284 mAh g^?1 at 0.1 C, whereas the sample synthesized via the conventional solid-state method yields only 265 mAh g^?1 at 0.1 C. The discharge capacities of the agar-assisted synthesized sample are 205 mAh g^?1 and 174 mAh g^?1 at 5 C and 10 C, respectively. Moreover, the sample exhibits high capacity retention of 91% after 100 discharge-charge cycles at 5 C. Based on the obtained results, the agar-assisted sol-gel process is inferred as one of the facile methods for preparing high performance anode materials for lithium-ion batteries.     

New anode materials of Li1+xV1?xO2 (0?≤?x?≤?0.1) for secondary lithium batteries: correlation between structures and properties

Li_1+x V_1−x O₂ (0 ≤ x ≤ 0.1) compounds were studied as the anode materials for a lithium-ion battery. The crystal and electronic structures of the prepared materials were correlated with electrical conductivities and electrochemical properties. The electrochemical behaviors were significantly dependent on the composition of Li_1+x V_1−x O₂, and these were resulted from the perturbation of the local electronic structure arising from the increase in lithium contents in Li_1+x V_1−x O₂ rather than from the slight distortion in the crystal structure. The electrical conductivities of Li_1+x V_1−x O₂ increased with the increase in lithium contents in the compounds. Li_1.1V_0.9O₂ and Li_1.075V_0.925O₂ samples exhibit the first discharge capacities of 250 and 241 mAh g⁻¹ at 0.2 C-rate, respectively.     

Electrochemical performance of chemically synthesized oligo-indole as a positive electrode for lithium rechargeable batteries

Indole monomer was chemically polymerized to produce polyindole (PI) powder for use as a positive electrode material for lithium rechargeable batteries. Although the PI obtained was an oligomer with a low molecular weight corresponding to just 3 indole units, its electrochemical properties exhibited high d.c. electric conductivity comparable to that of the highly conducting polyaniline-LiPF₆ or LiAsF₆. A charge separation mechanism was also suggested to describe charge/discharge behavior of the oligo-indole (OI) protonated and/or lithiated in the Li||OI battery. Moreover, the lithium rechargeable battery adopting the OI as a positive electrode showed good cycleability with a discharge capacity of ∼55 mAh g⁻¹, which did not decay until after more than 100 cycles.     

Modified polysulfides conversion catalysis and confinement by employing La2O3 nanorods in high performance lithium-sulfur batteries

The development of lithium-sulfur batteries (LSB) was hindered due to the shuttling of Li-polysulfides in electrolytes and sluggish electrochemical kinetics of polysulfides. To address these stumbling blocks, we introduced La₂O₃ nanorods modification of ketjen black@sulfur (La₂O₃/KB@S) composite that adsorbs and provides sufficient sites with Li-polysufides interaction. The La₂O₃ nanorods play a key role in the adsorption and catalysis performance of the polysulfides, which further accelerate the redox kinetics. Consequently, the La₂O₃/KB@S cathode with sulfur loading of 3.1 mg cm⁻² attained a high initial discharge capacity of 833 mAh g⁻¹ at a 0.5C rate and displayed excellent cyclic stability with reversible capacity of 380 mAh g⁻¹ after 500 cycles with an average of 98% coulombic efficiency. Further, even with high sulfur loading of 5 mg cm⁻², the La₂O₃/KB@S cathode also presents a capacity of 4.9 mAh at 0.3C and still maintains a stable value of 3.87 mAh after 150 cycles. The results suggest the multifunction La₂O₃ nanorods anchoring effectively and catalyzing are beneficial to realize the goal of the large-scale application with high load active materials and high-performance LSB.     

Cs4PbBr6 QDs silicate glass-ceramic: A potential anode material for LIBs

Lithium-ion batteries (LIBs) have attracted special attention in the new energy field, while halide perovskites are potential materials in the field of energy. In this work, Cs₄PbBr₆ quantum dots silicate glass-ceramic is synthesized by melt-quenching methods and examined as LIBs anode materials. The half-battery provides a high initial discharge specific capacity of about 1986.9 mAh g^?1 and a remarkably high reversible capacity of 426.7 mAh g^?1. Also, the present glass material shows good rate performance. Between the perovskite quantum dots and the silicate glass exists an interesting synergistic effect, and the observed prominent electrochemical performance proves that the quantum dots glass-ceramic materials are viable for lithium-ion batteries application.     

Effects of Al doping on the electrochemical performances of LiNi0.83Co0.12Mn0.05O2 prepared by coprecipitation

The Ni-rich LiNi_0.83Co_0.12Mn_0.05O₂ (NCM83) cathode materials have drawn intensive attention due to the high energy density and low cost. However, Ni-rich LiNi_1-x-yCo_xMn_yO₂ still has the fatal weakness of poor cycle stability, limiting its further wide application. Bulk doping is an effective means to enhance the cycle stability, yet the electrochemical performances are very sensitive to the doping quantity. Here a facile method of co-precipitation is adopted to coat (Ni_0.4Co_0.2Mn_0.4)_1-xAl_x(OH)_2+x on precursor particles of NCM83. Al ions diffuse evenly in the NCM83 particles after sintering. The cells are operated at a high cut-off voltage of 4.5 V. The discharge capacity of NCM83 is 187.8 mAh g^?1, and decays fast with cycles. The doped sample even exhibits a higher discharge capacity of 195 mAh g^?1, and the capacity retention is improved to 83.8% after 200 cycles.     

Lithium storage behaviors of PbNb2O6 in rechargeable batteries

Herein, we propose a new anode material, PbNb₂O₆, for use in lithium-ion batteries. PbNb₂O₆ can be synthesized via a simple and traditional solid-state method. The as-prepared powder exhibits an average size distribution of about 0.5 μm. When tested in a lithium-ion cell, the PbNb₂O₆ electrode can exhibit a charge capacity of 245.2 mAh g⁻¹ at 200 mA g⁻¹, and after 80 cycles, the capacity can retain a charge capacity of 181.4 mAh g⁻¹, showing 0.32% capacity fading per cycle. Furthermore, the capacity of the PbNb₂O₆ electrode is 223.1 mAh g⁻¹, even when cycled at 1000 mA g⁻¹, and a capacity of 150.7 mAh g⁻¹ is maintained up to 500 cycles. In addition, the lithiation mechanism of PbNb₂O₆ is investigated via various techniques. Interestingly, PbNb₂O₆ exhibits high capacity without the contribution of two redox couples of niobium after the initial cycles. Finally, all Results suggest that PbNb₂O₆ has potential for use as an electrode in lithium-ion batteries.     

Influence of alloying and microstructure on the electrochemical hydriding of TiNi-based ternary alloys

Nanostructured ternary TiNi-type alloys, namely Ti_0.8M_0.2Ni (M = Zr, V), TiNi_0.8N_0.2 (N = Cu, Mn) and TiNi_1−x Mn _x (x = 0.2, 0.4, 0.6, 1.0), were synthesized by mechanical alloying. Depending on the intensity and time of milling alloys with different microstructure were obtained. The as-milled TiNi_1−x Mn _x alloys contain substantial amount of amorphous phase, which crystallizes during annealing. Annealing of the as-milled fine nanocrystalline materials at 500 °C results only in slight coarsening of the microstructure, which remains still nanocrystalline. Fully crystalline material (with crystal size larger than 50 nm), consisting of mainly cubic TiNi was obtained by annealing the ball-milled alloys at T ≥ 700 °C. Electrochemical hydrogen charge/discharge cycling of the as-milled as well as of annealed alloys were carried out at galvanostatic conditions. It was found that among the nanocrystalline Ti_0.8M_0.2Ni_0.8N_0.2 (M = Zr, V; N = Cu, Mn) alloys TiNi_0.8Mn_0.2 revealed the highest discharge capacity of 56 mAh g⁻¹ in the as-milled state and 75 mAh g⁻¹ after short-time annealing at 500 °C. Annealing at higher temperature does not increase the capacity further. The as-milled TiNi_1−x Mn _x alloys with x ≤ 0.4 reveal noticeably higher discharge capacity and better cycle life than the Mn-richer alloys. Based on potentiostatic experiments the diffusion coefficients of hydrogen into TiNi alloys in two different microstructural states (fine and coarser nanocrystalline) as well as in as-milled amorphous/nanocrystalline and nanocrystalline TiNi_0.8Mn_0.2 were determined. The hydrogen diffusion coefficients of the TiNi alloys are comparable (1.9–2.7 × 10⁻¹² cm² s⁻¹). The diffusion coefficient in the as-milled amorphous/nanocrystalline TiNi_0.8Mn_0.2 was found to be 3–4 times higher than that of the as-milled nanocrystalline alloy.     

Synthesis and electrochemical characterization of LiCoxMn1−xPO4/C nanocomposites

LiCo_xMn_1−xPO₄/C nanocomposites (0 ≤ x ≤ 1.0) were prepared by a combination of spray pyrolysis at 300 °C and wet ball-milling followed by heat treatment at 500 °C for 4 h in 3% H₂ + N₂ atmosphere. X-ray diffraction analysis indicated that all samples had the single phase olivine structures indexed by orthorhombic Pmna. The lattice parameters linearly decreased with increasing cobalt content, which confirmed the existence of solid solutions. It was clearly seen from the scanning electron microscopy observation that the LiCo_xMn_1−xPO₄/C samples were agglomerates with approximately 100 nm primary particles. The LiCo_xMn_1−xPO₄/C nanocomposites were used as cathode materials for lithium batteries, and electrochemical performance was comparatively investigated with cyclic voltammetry and galvanostatic charge–discharge test using the Li?1 M LiPF₆ in EC:DMC = 1:1?LiCo_xMn_1−xPO₄/C cells at room temperature. The cells at 0.05 C charge–discharge rate delivered first discharge capacities of 165 mAh g⁻¹ (96% of theoretical capacity) at x = 0, 136 mAh g⁻¹ at x = 0.2, 132 mAh g⁻¹ at x = 0.5, 125 mAh g⁻¹ at x = 0.8 and 132 mAh g⁻¹ (79% of theoretical capacity) at x = 1.0, respectively. While the first discharge capacity increased with the cobalt content at high charge–discharge rates more than 0.5 C due to higher electronic conductivity of LiCoPO₄ in comparison with LiMnPO₄, the cycleability of cell became worse with increasing the amount of cobalt. The existence of Mn²⁺ seemed to enhance the cycleability of LiCo_xMn_1−xPO₄/C nanocomposite cathode.     

Synthesis and electrochemical properties of mixed-phase αx/β1-x-LiVOPO4/C composites

Mixed-phase α_x/β_1-x-LiVOPO₄/C (x = 0.1, 0.3, 0.5, 0.7, 0.9) composites were synthesized by the solid-phase sintering method. X-ray diffraction (XRD) analyses revealed that a series of composites were comprised of pure triclinic α-LiVOPO₄ and orthorhombic β-LiVOPO₄ components. The mixed-phase materials exhibit better rate performance than whether pure triclinic α-LiVOPO₄/C or orthorhombic β-LiVOPO₄/C. The α_0.5/β_0.5-LiVOPO₄/C (α:β = 1:1) composite exhibit superior high-rate capability. When cycled at 2C and 5C, the initial discharge capacities of the α_0.5/β_0.5-LiVOPO₄/C composite are 81.1 mAh g^?1 and 69.8 mAh g^?1 respectively, which are significantly higher than those of the pure α-LiVOPO₄/C (30.6 mAh g^?1 and 18.6 mAh g^?1, respectively) and β-LiVOPO₄/C (56.8 mAh g^?1 and 36.9 mAh g^?1, respectively). The improved electrochemical performance could be attributed to the mixed phase possess an open framework and stable structure.