Electrochemical Performance Of LiMn2O4 Research Articles

Efficient enhancement on crystallization and electrochemical performance of LiMn2O4 by recalcination treatment

Spinel LiMn2O4 cathode material was obtained by a recalcination treatment, which exhibits excellent crystallization and electrochemical performance. A series of test and analysis results revealed that the performance enhancement of as-prepared sample is related to the crystal structure, morphology and electrochemical properties. Owing to the recalcination treatment, the spinel LiMn2O4 presents a truncated-octahedral morphology with selective growth of the (110) and (100) crystal planes, which would effectively inhibit manganese dissolution. Moreover, the optimized sample exhibits a better crystallinity and electrochemical reversibility than that of pristine sample, which can provide a faster Li ion de-intercalation/intercalation kinetics. Hence, the spinel LiMn2O4 cathode material delivers a high initial discharge capacity of 112.3 mAh·g−1 with a good capacity retention of 90.3% after 500 cycles and an excellent rate performance. This study constructed a facile and meaningful method to prepare spinel LiMn2O4 cathode material, which may facilitate the development of lithium-ion batteries.

Improving the electrical conductivity and electrochemical performance of LiMn2O4 by Sm gaseous penetration technology

Aiming at the poor electrical conductivity and rate performance of LiMn2O4, the rare earth gaseous penetration technology was used to modify commercial LiMn2O4. XRD, SEM, TEM, FTIR, XPS and other characterization methods were used to investigate the resistivity, morphology, phase structure and electrochemical performance. ICP measurement and the mapping diagrams of TEM displayed that there was a small amount of Sm with evenly distribution after penetration. Sm-modified LiMn2O4 still maintained the standard spinel structure, Mn3+ was partially replaced by Sm3+ during the penetration process, the bond energy of Sm-O bond was stronger than that of Mn-O bond, which stabilized the spinel structure of LiMn2O4. The particle size of LiMn2O4 decreased after penetration, which can shorten the migration path of Li+ from the inside of the particle to the surface during the charge and discharge processes, and increase the charge transfer rate. The resistivity of LiMn2O4 reduced to 1.15 × 105 Ω·cm and the initial discharge specific capacity of Sm-modified LiMn2O4 was 110.9 mAh·g−1 at 0.1C. Moreover, Sm-modified LiMn2O4 exhibited excellent rate capabilities. This work is useful for providing a concrete method to improve the electrical conductivity and electrochemical performance of LiMn2O4 in industry.

Electrochemical performanceof LiMn2O4 with varying thickness of cathode sheet

Lithium-ion batteries are widely used as portable electrical energy storage devices because they have high energy densities and long life cycles. One of the cathode active materials used in the manufacture of Lithium-ion batteries is LiMn2O4 because of its easy and cheap manufacturing, has a long life cycle, high power applications, safe, and low toxicity of manganese basic materials. In this research, LiMn2O4 as cathode sheet has been made by doctor blade coating. This method was carried out by mixing LiMn2O4 with polyvinylidene fluoride (PVDF), Super P, and dimethylacetamide (DMAC) with weight ratio of 82.5: 10: 7.5, respectively, to obtain a well dispersed slurry. Slurry was superimposed on aluminum foil surface with various thickness of 200, 300 and 400 μm. Coin cell was assembled using electrodes, separator, lithium metal and electrolytes in the glove box. The cell battery was characterized by using cyclic voltammetry, charge discharge and electrochemical impedance spectroscopy in order to know the effect of active material thickness to cell battery performances. The results showed that active material with 400 μm in thickness had the best electrochemical performance due to a narrow and sharp reduction-oxidation peak pair, small polarization value of 0.0335 V as well as having charge and discharge capacities of 1.1249 mAh and 1.0914 mAh, respectively. Moreover, EIS result showed that 400 μm thickness of active material had highest conductivity value of 5.3922 × 10−5 Scm−1.

Porous LiMn2O4 Microspheres With Different Pore Size: Preparation and Application as Cathode Materials for Lithium Ion Batteries

Three types of LiMn2O4 (LMO) microspheres with different pore size are prepared by a facile method, using porous MnCO3–MnO2 and Mn2O3 microspheres as the self-supporting template, for lithium ion batteries (LIBs) cathode material. Briefly, Mn2O3 and MnO2 microspheres are heated in air at 600 °C for 10 h to synthesize porous Mn2O3 spheres. Then the mixture of as-prepared spherical Mn2O3 and LiNO3 is calcined to obtain the LMOs. The morphology and structure of LMOs are characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and nitrogen adsorption/desorption analyses. The result shows that the maximum pore diameters of LMOs are 17 nm, 19 nm, and 11 nm, respectively. All LMOs microspheres are composed of similar sized nanoparticles; however, the surface of these microspheres is strewed with dense tinier pores or sparse larger pores. Generally, the nanoparticles will reduce the path of Li+ ion diffusion and increases the reaction sites for lithium insertion/extraction. Moreover, the pores can provide buffer spaces for the volume changes during charge–discharge process. The electrochemical performances of LMOs are investigated and LMO2 exhibits extremely good electrochemical behavior, especially the rate capability. The as-prepared LMO2 delivers a discharge capacity of 124.3 mAh g−1 at 0.5 C, retaining 79.6 mAh g−1 even at 5 C. The LMO2 sample also shows good capacity retention of 96.9% after 100 cycles at 0.5 C.

Surfactant-assisted synthesis of LiMn2O4 particles as high-rate and long-life cathode materials for lithium-ion batteries

Herein, we reported the synthesis of uniform LiMn2O4 submicroparticles by surfactant-assisted preparation of spherical MnCO3 precursor followed by solid-state reaction. Polyethylene glycol (Mw = 1000) was used as surfactant to control the morphology and size of the MnCO3 precursor as well as the MnO2 intermediate and LiMn2O4 product. The influence of particle size, homogeneity, and crystallinity on the electrochemical performance of LiMn2O4 was intensively investigated. The test results indicate that the LiMn2O4 sample using polyethylene glycol with weight as 10% of reactants shows the best rate capability and long-term cyclability. Due to the homogeneous particles with the average size of ca. 250 nm and high crystallinity, the discharge capacities are as high as 125, 118, 114, and 100 mAh g−1 at 1, 10, 20, and 50 C rates, respectively, along with high capacity retention of 74% after 1000 cycles at 20 C.

Hybrid LiMn2O4–radical polymer cathodes for pulse power delivery applications

Electrochemical performances of LiMn2O4 (LMO) – poly (2,2,6,6-tetramethyl-1-piperinidyloxy-4-yl methacrylate) (PTMA) hybrid electrodes are investigated. Different constituent ratios are tested and the impact on the power and the cycling performances is discussed. Variable rate galvanostatic charge/discharge tests show improved energy-power performances and capacity retention of the hybrid LMO/PTMA electrodes when compared to pure LMO electrodes. This enhancement is correlated to a sequential power delivery mechanism by the fast kinetic component (PTMA) subsequently recharged by the high-energy constituent (LMO). Hybrid electrodes are shown to deliver higher energy and longer cycle life when subjected to power pulse tests. The combination of the PTMA power buffer component with the LMO high-energy sink proves the potential of the hybrid energy-power electrodes in pulsed discharge applications.

Multiphase combustion synthesis and enhanced performance of LiMn2O4 nanoparticles using CNTs as a fuel

LiMn2O4 nanoparticles were successfully prepared using suitable dosage carbon nanotubles (CNTs) as a fuel through multiphase combustion synthesis. The effects of CNTs on the structure and electrochemical performance of LiMn2O4 were investigated. Rate performance test demonstrates that CNTs dosage greatly affect the electrochemical behaviour of LiMn2O4 and LiMn2O4 prepared by choosing suitable CNTs dosage (7%) as a fuel (C7%-LMO) shows high rate charge–discharge capability. X-ray diffraction results indicate that C7%-LMO has the smallest distortion degree in the crystal, compared to LiMn2O4 prepared without CNTs (C0%-LMO) and LiMn2O4 prepared with 10% CNTs (C10%-LMO). SEM results reveal that the average particle size of C7%-LMO is about 100 nm, which is the smallest among the three samples (C0%-LMO, C7%-LMO and C10%-LMO). This unique microscopic features guarantee C7%-LMO possesses the highest discharge capacity, the best cycling performance and the lowest charge transfer resistance among the three samples.

Carbon coated to improve the electrochemical properties of LiMn2O4 cathode material synthesized by the novel acetone hydrothermal method

Spinel LiMn2O4 particle is successfully synthesized by the acetone hydrothermal method without further sintered at high temperature. The electrochemical performances of LiMn2O4 at room temperature are improved by carbon modification through a post-heat treatment. SEM exhibits that the particles are well distributed and the primary grains are 5 μm in size. TEM indicates that the LiMn2O4/C is uniformly coated with a carbon layer about 2.0 nm in size. The electrochemical performances show that the pristine sample has an initial discharge capacity of 127.9 mAh g−1, and the capacity decreases to 110.6 mAh g−1 with the losses of 14.2 % after 100 cycles. Apparently, the LiMn2O4/C exhibits an initial capacity with 134.9 mAh g−1, and capacity losses of only 4.3 % after 100 cycles. At a discharge rate of 1 C, it keeps more than 97.18 % of the reversible capacity compared with that at 0.1 C. At the same time, the sample LiMn2O4/C shows only 5.84 % discharge capacity loss at the elevated temperature. The results show that the LiMn2O4/C sample with excellent electrochemical performances should attribute to the carbon layer avoiding the core material direct contact with the acidic electrolyte and suppression of Mn+ dissolution into electrolyte.

Effects of binder content on manganese dissolution and electrochemical performances of spinel lithium manganese oxide cathodes for lithium ion batteries

In this study, the effects of the polyvinylidene fluoride (PVdF) binder on the Mn dissolution behavior and electrochemical performances of LiMn2O4 (LMO) electrodes are investigated. It is found that increasing the PVdF content (3, 5, 7, and 10 wt.%) leads to reduced Mn dissolution, and thus superior cycle performance at elevated temperature (60 °C). This can be ascribed to increased binder coverage on the LMO surface, as evidenced by X-ray photoelectron spectroscopy measurements, which acts a role as a passivation layer for Mn dissolution. The rate capability of the LMO electrode is hardly deteriorated as the PVdF content increases, despite the increasing surface coverage. Electrochemical impedance measurements reveal that the LMO electrode with higher binder loading exhibits lower electrode impedance, which is suggested to be due to enhanced electronic passage through the composite LMO electrode.

Improvement in the Electrochemical Performances of Spinel LiMn2O4 cathodes By MnO2 coating for Lithium Ion Battery Application

Lithium ion batteries (LIBs) are considered as attractive power sources for electric vehicles (EV) and aenergy storage systems (ESS) as well as portable electronic devices due to their high energy density and long cycle life. Importantly, EV and ESS applications require high power density and thermal stability as well as low cost. In this regard, spinel LiMn2O4 is a promising cathode material because of its low cost, good safety, high abundance and environmental harmlessness. However, LiMn2O4 generally exhibits poor capacity retention especially at elevated temperatures mostly owing to the Mn dissolution. Moreover, Jahn Teller effect also causes the structural instability, which can be seen on the surface of LiMn2O4 at high current application. Previous literatures verify that surface-modification by coating plays an important role in electrochemical performances of LiMn2O4. The surface treatment of LiMn2O4 is known to prohibit Mn dissolution from LiMn2O4 electrode. In this study, the MnO2 were prepared on the surface of LiMn2O4 powders. The synthesis procedure includes mixing KMnO4 solution with ethylene glycol through oxidation-reduction reaction under ambient conditions. Electrochemical evaluation as well as storage test at elevated temperatures reveal that the surface-modification with MnO2 enhance the rate capability and improve the storage characteristics at 60oC of spinel LiMn2O4 cathode materials. In-depth analyses such as X-ray Photoelectron Spectroscopy and Electrochemical Impedance Spectroscopy are also performed to elucidate the effect of surface-modification using MnO2.

Effect of Al-Doping on Electrochemical Performance of LiMn2O4

Effect of Al-Doping on Electrochemical Performance of LiMn2O4

Enhanced High-Temperature Cycling Stability of LiMn<sub>2</sub>O<sub>4</sub> by Coating LiNi<sub>0.5</sub>Mn<sub>1.5</sub>O<sub>4</sub>

To enhance the electrochemical performances of LiMn2O4 at elevated temperature (55°C), we proposed a sol-gel method to synthesize LiNi0.5Mn1.5O4 modified LiMn2O4. The physical and electrochemical performances of pristine and LiNi0.5Mn1.5O4-coated LiMn2O4 cathode materials were investigated by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy and electrochemical measurements, respectively. The results indicated that about 4-5 nm thick layer of LiNi0.5Mn1.5O4 was formed on the surface of the LiMn2O4 powders. The modified LiMn2O4 exhibited excellent storage performance at 55&degC compared to the pristine one, which was attributed to the suppression of electrolyte decomposition and the reduction of Mn dissolution.

Conventional- and microwave-hydrothermal synthesis of LiMn2O4: Effect of synthesis on electrochemical energy storage performances

The LiMn2O4 electrode materials were synthesized by the conventional-hydrothermal and microwave-hydrothermal methods. The electrochemical performances of LiMn2O4 were studied as supercapacitors in LiNO3 electrolyte and lithium-ion battery cathodes. The microwave-hydrothermal method can synthesize LiMn2O4 electrode materials with reversible electrochemical reaction in a short reaction time and low reaction temperature than conventional-hydrothermal route. The capacitance of LiMn2O4 electrode increased with increasing crystallization time in conventional-hydrothermal route. The results showed that LiMn2O4 supercapacitors had similar discharge capacity and potential window (1.2V) as that of ordinary lithium-ion battery cathodes. In LiNO3 aqueous electrolyte, the reaction kinetics of LiMn2O4 supercapacitors was very fast. Even, at current densities of 1A/g and 5A/g, aqueous electrolyte gave good capacity compared with that in organic electrolyte at a current density of 0.05A/g.

Effects of precursor treatment on the structure and electrochemical properties of spinel LiMn2O4 cathode

As a precursor of spinel LiMn2O4 cathode, manganese oxide is prepared by co-precipitation via a two-step drying method. The effects of precursor treatment on the structure, morphology, and electrochemical performance of the synthesized spinel LiMn2O4 are studied using contrasting experiments involving the addition of hydrazine, N2, and H2O2. The tests show that different treatments have a great effect on the crystal structure, morphology, tap density, and electrochemical performance of LiMn2O4. When the precursor is treated by adding hydrazine and pure N2, the synthesized LiMn2O4 shows an integral lattice, uniform particle size, a pure spinel phase with an ordered octahedral crystal structure, and high tap density (2.23gcm−3). The electrochemical results show that spinel LiMn2O4 exhibits higher specific capacity and better cyclic stability than other samples, especially at an elevated temperature and high discharge current. The initial discharge capacity of the electrode is 110.8mAhg−1 at a rate of 3°C, and exhibits a good capacity retention of 96.4% after 30 cycles; at a rate of 5°C, the initial discharge capacity is 107.5mAhg−1, with a capacity retention of 87.3% after 50 cycles.

Preparation and electrochemical properties of x Li2MnO3·(1-x)LiMn2O4 composites

Li2MnO3-doped spinel LiMn2O4 composites were synthesized by sol-gel method to improve the electrochemical performance of LiMn2O4. The microstructures, morphologies and electrochemical performance of the obtained xLi2MnO3·(1-x)LiMn2O4 composites were characterized by X-ray diffraction(XRD), scan electron microscopy(SEM) and a galvanostatic charge-discharge process. It was found that both Li2MnO3 and LiMn2O4 components exist in xLi2MnO3·(1-x)LiMn2O4(0<x<1) composites. The 0.3Li2MnO3·0.7LiMn2O4 composite shows the optimized electrochemical performance, including discharge capacity and cycle stability. It was demonstrated that Li2MnO3-doped spinel LiMn2O4 cathode material can work at wide potential window with quite good capacity retention and considerably larger reversible capacity compared to single-phase LiMn2O4 component.

Synthesis and electrochemical performance of YF3-coated LiMn2O4 cathode materials for Li-ion batteries

Spinel LiMn2O4 cathodes were coated with 1 mol% YF3. X-ray diffraction (XRD) analyses showed that Y and/or F did not enter the lattice of the LiMn2O4 crystal. Transmission electron microscopy (TEM) showed that a compact YF3 layer of 5-20 nm in thickness was coated onto the surface of LiMn2O4 particles. Scanning electron microscopy (SEM) observation showed that the YF3 coating caused the agglomeration of LiMn2O4 particles. The cycling test demonstrated that the YF3 coating can improve the electrochemical performance of LiMn2O4 at both 20 and 55℃. Moreover, YF3-coated LiMn2O4 exhibited an improved rate capability compared with the uncoated one at high rates over 5C. The immersion test in electrolytes showed that YF3-coated LiMn2O4 is more erosion resistant than the uncoated one.

Preparation, characterization and electrochemical performance of γ-MnO2 and LiMn2O4 as cathodes for lithium batteries

The spinel LiMn2O4 is a very promising cathode material with economical and environmental advantages. LiMn2O4 materials have been synthesized by solid state method using γ-MnO2 as manganese source, and Li2CO3 or LiNO3 as Li sources. γ-MnO2 is a commercial battery grade electrolytic manganese dioxide (TOSOH-Hellas GH-S) and LiMn2O4 samples were synthesized at a calcinations temperature up to 800 °C. γ-MnO2 and LiMn2O4 samples were characterized by X-ray diffraction, thermal and electrochemical measurements. X-ray powder diffraction of as prepared LiMn2O4 showed a well-defined highly pure spinel single phase. The electrochemical performance of LiMn2O4 and its starting material γ-MnO2 was evaluated through cyclic voltammetry, galvanostatic (constant current charge-discharge cycling) The electrochemical properties in terms of cycle performance were also discussed.