LiMn2O4 Cathode Material Research Articles

Synthesis and electrochemical performance of a LiMn1.83Co0.17O4 shell/LiMn2O4 core cathode material

A shell/core Co-incorporated LiMn2O4 cathode material was synthesized by a facile modified sol–gel process, using highly dispersed Mn3O4 nanoparticles as the Mn source. Structural characterization revealed that the shell layer, which was 5–10nm thick, and composed of spinel LiMn1.83Co0.17O4, grew homogeneously on the spinel LiMn2O4 core with a size of ~50nm. Electrochemical results showed that electrochemical performance of the shell/core cathode material compared favorably with that of the Co-doped LiMn2O4 counterparts. Also its rate capability and cycling performance were apparently superior to those of pristine LiMn2O4 synthesized under the same conditions. The shell/core cathode material exhibited a discharge capacity of 127mAhg−1 at a current rate of 0.5C (where 1C=148mAg−1), and retained a capacity of 103mAhg−1 at 10C, showing 81% capacity retention. After 200 cycles at 1C and 25°C, it delivered a capacity of 123mAhg−1, retaining 98% of its initial capacity. After 100 cycles at 1C and 55°C, it showed a capacity of 118mAhg−1, preserving 94% of its initial capacity. Its excellent electrochemical performance along with the facile synthesis process allowed the shell/core cathode material to serve as a promising cathode for high-performance Li-ion batteries.

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.

Crystal chemical investigation of nano inclusion in LiMn2O4cathode material of lithium ion battery

We found that the (100) plane of LiMn2O4and the (110) plane of ZnMn2O4connect without grain boundary.

Enhanced High-Temperature Cycling Stability of LiMn<SUB>2</SUB>O<SUB>4</SUB> by LiCoO<SUB>2</SUB> Coating as Cathode Material for Lithium Ion Batteries

LiCoO2 surface layer is proposed and prepared through sol-gel method. The physical and electrochemical performances of pristine LiMn2O4 and LiCoO2-coated LiMn2O4 cathode materials were investigated by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, electrochemical measurements respectively. Comparing with the pristine LiMn2O4, the LiCoO2- coated LiMn2O4 phase significantly improved cycling stability, especially at 55°C. Additionally, the thermal safety of LiMn2O4 is greatly enhanced after being coated by LiCoO2. ICP-AES measurement, structural analysis, and impedance experiments indicate that the improved electrochemical property of LiCoO2-coated LiMn2O4 should be attributed to the alleviated dissolution loss of manganese, strengthened structural stability.

Modeling of Lithium Ion Batteries Employing Grand Canonical Monte Carlo and Multiscale Simulation

In the current investigation modeling of two half cells (LiMn2O4 cathode and carbon anode) followed by modeling of the complete cell of the battery employing Grand Canonical Monte Carlo simulations to evaluate open circuit potential and energetic of the process involved had been carried out. Current model takes into account the effect of electrolyte and temperature variations on various battery parameters like open circuit potential, cell current, cell voltage and free energy of Li+ intercalation/deintercalation. Estimation of open circuit potential (OCV) of Lithium ion batteries becomes vital as it is a crucial parameter in (i) estimating diffusion coefficient of lithium in the electrode material during charge/discharge process, (ii) obtaining entropy of the reaction and internal energy calculations and (iii) understanding thermal runaway problems. The strong dependence of OCV with the state of charge (SOC) of the battery and temperature makes the prediction more difficult. To avoid computational tediousness, Grand Canonical Monte Carlo technique coupled with multiscale simulation is employed to predict experimental OCV of LiMn2O4 cathode material in the presence of electrolyte solution.

Electrochemical behavior and surface structural change of LiMn2O4charged to 5.1 V

Charging a spinel LiMn2O4cathode material to high voltage (>4.3 V) is a convenient way to obtain more lithium ions for formation of an anodic solid-electrolyte-interface in a full cell.

Structural Changes in Li2MnO3 Cathode Material for Li‐Ion Batteries

Structural changes in Li2MnO3 cathode material for rechargeable Li‐ion batteries are investigated during the first and 33rd cycles. It is found that both the participation of oxygen anions in redox processes and Li+‐H+ exchange play an important role in the electrochemistry of Li2MnO3. During activation, oxygen removal from the material along with Li gives rise to the formation of a layered MnO2‐type structure, while the presence of protons in the interslab region, as a result of electrolyte oxidation and Li+‐H+ exchange, alters the stacking sequence of oxygen layers. Li re‐insertion by exchanging already present protons reverts the stacking sequence of oxygen layers. The re‐lithiated structure closely resembles the parent Li2MnO3, except that it contains less Li and O. Mn4+ ions remain electrochemically inactive at all times. Irreversible oxygen release occurs only during activation of the material in the first cycle. During subsequent cycles, electrochemical processes seem to involve unusual redox processes of oxygen anions of active material along with the repetitive, irreversible oxidation of electrolyte species. The deteriorating electrochemical performance of Li2MnO3 upon cycling is attributed to the structural degradation caused by repetitive shearing of oxygen layers.

Structural and electrochemical properties of aluminium doped LiMn2O4 cathode materials for Li battery: Experimental and ab initio calculations

Pristine and Al-doped lithium manganese oxide (LiAlxMn2−xO4) spinel cathode materials were successfully synthesized by combustion method using urea as reducer and fuel. The structural and electrochemical properties of the as-synthesized powders were characterized using scanning electron microscopy, X-ray diffraction, energy dispersive spectroscopy and charge/discharge testing. The effect of aluminium doping on the discharge capacity was studied for different aluminium concentration x=0, 0.05, 0.1 and 0.5. The as-synthesized Al doped samples LiAl0.05Mn1.95O4 and LiAl0.1Mn1.9O4 exhibited higher discharge capacity for the first two cycles compared to the first cycle discharge capacity of pristine LiMn2O4. The first-principles calculations predict an increase in lattice parameter for x=0.05 and 0.1 to be responsible for the increase in first cycle discharge capacity for x=0.05 and 0.1. In addition, we have found that LiAl0.5Mn1.5O4 sample exhibited the more stable capacity than the other samples.

The electrochemical performance of sodium-ion-modified spinel LiMn2O4 used for lithium-ion batteries

The spinel LiMn2O4 cathode material has been considered as one of the most potential cathode active materials for rechargeable lithium ion batteries. The sodium-doped LiMn2O4 is synthesized by solid-state reaction. The X-ray diffraction analysis reveals that the Li1−x Na x Mn2O4 (0 ≤ x ≤ 0.01) exhibits a single phase with cubic spinel structure. The particles of the doped samples exhibit better crystallinity and uniform distribution. The diffusion coefficient of the Li0.99Na0.01Mn2O4 sample is 2.45 × 10−10 cm−2 s−1 and 3.74 × 10−10 cm−2 s−1, which is much higher than that of the undoped spinel LiMn2O4 sample, indicating the Na+-ion doping is favorable to lithium ion migration in the spinel structure. The galvanostatic charge–discharge results show that the Na+-ion doping could improve cycling performance and rate capability, which is mainly due to the higher ion diffusion coefficient and more stable spinel structure.

Study on the performance of LiMn2O4 using spent Zn–Mn batteries as manganese source

Recycling spent Zn–Mn batteries by synthesizing the products with high added value is very active internationally. In this work, we have successfully synthesized the spinel LiMn2O4 cathode materials for rechargeable lithium-ion batteries by simple sol–gel method using the manganese source that is recovered from spent Zn–Mn batteries through hydrometallurgy recycling technology. The influence of sintering temperature on the structure, the morphological properties, and the electrochemical properties of the product is investigated. The results show that spinel LiMn2O4 prepared at 700 °C has the best comprehensive performance. Moreover, the electrochemical performance of spinel LiMn2O4 has been further optimized by Co-ion doping.

Synthesis of LiMn2O4 Cathode Material for Lithium Ion Batteries By Solid State Process

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Effect of “Nano Inclusion” On Cycle Performance of LiMn2O4 Cathode Material At 3V Range

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Crystal Study of "Nano Inclusion" in LiMn2O4 Cathode Material of Lithium Ion Battery

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Characterization of surface-modified LiMn2O4 cathode materials with indium tin oxide (ITO) coatings and their electrochemical performance

Abstract Indium tin oxide (ITO) is used to modify the surface of LiMn2O4 by a sol–gel method in an attempt to improve its electrochemical performance at elevated temperatures. The surface-modified LiMn2O4 is characterized via XRD, FE-SEM, TEM, Auger electron spectroscopy (AES) and inductively coupled plasma-atomic emission spectroscopy (ICP-AES). The surface layer modified by substitution with indium was observed at a scale of several nanometers near the surface on LiMn2O4. The concentration of ITO for electrochemical performance was varied from 0.3 wt% to 0.8 wt%. The 0.5 wt% ITO coated LiMn2O4 showed the best electrochemical performance. This enhancement in electrochemical performance is mainly attributed to the effect of the surface layer modified through ITO, which could suppress Mn dissolution and reduce the charge transfer resistance at the solid electrolyte interface.

Structure and Electrochemical Performances of Co-Substituted LiCo<SUB><I>x</I></SUB>Li<SUB><I>x−y</I></SUB>Mn<SUB>2−<I>x</I></SUB>O<SUB>4</SUB> Cathode Materials for the Rechargeable Lithium Ion Batteries

Spinel LiMn2O4 and Co, Li co-substituted LiCo(x)Li(x-y)Mn(2-x)O4 (x = 0.20; y = 0.05, 0.10 and 0.15) cathode materials were synthesized by sol-gel technique using lithium acetate, manganese acetate, cobalt acetate and tartaric acid as the starting materials. The effect of Co, Li substitution on the structure and surface morphology of LiCo(x)Li(x-y)Mn(2-x)O4 has been examined by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The materials for all the compositions have exhibited a phase pure cubic spinel structures from the XRD analysis. The crystallinity and average particle size of the synthesized materials were decreased by the substitution of Co, Li. The electrochemical properties of the assembled LiCo(x)Li(x-y)Mn(2-x)O4/Li/LiPF6 cells were evaluated for charge/discharge studies at different rates and electrochemical impedance measurements. This co-substituted LiMn2O4 has improved specific capacity and capacity retention over pure spinel LiMn2O4. The co-substitution of LiMn2O4 cathode material has increases cyclability; however, the discharge capacity reduces. Among all the compositions, LiCo(0.10)Li(0.10-)Mn(1.80)O4 cathode has improved the structural stability and excellent electrochemical performances of the rechargeable lithium-ion batteries.

Performance improvement of spinel LiMn2O4 cathode material by LaF3 surface modification

Abstract LiMn 2 O 4 cathode material synthesized by a sol–gel method was modified by LaF 3 via wet coating strategy. The phase structures, components and morphologies of pristine and LaF 3 -coated LiMn 2 O 4 are investigated by X-ray diffraction (XRD), Raman spectroscopy, field emission scanning electron microscopy (FESEM) and electron diffraction spectroscopy (EDS). The electrochemical performances are investigated and compared at room temperature (25 °C) and elevated temperature (55 °C) for pristine and LaF 3 -coated LiMn 2 O 4 . The investigation on their cycling performance demonstrates that 3 wt.% LaF 3 -coated LiMn 2 O 4 exhibits the best cycling performance, with the capacity losses of only 15.9% after 200 cycles at 25 °C and 19.7% after 100 cycles at 55 °C, much better than those of pristine materials, 60% and 59.8%. Rate performance was improved after LaF 3 surface modification. Chronoamperometry experiments indicate that phase transformation is the rate determining step in 4.0–3.5 V region. Cyclic voltammetry (CV) results confirm that LaF 3 surface coating improves structure stability of LiMn 2 O 4 during cycling. Electrochemical impedance spectroscopy (EIS) data further demonstrate that modification layer suppresses the undesirable growth of resistance of surface (R sf ) film. Differential scanning calorimetry (DSC) tests show that LaF 3 coating layer helps to improve the thermal stability of pristine electrode.

Effect of β-Cyclodextrin on Electrochemical Properties of LiMn<sub>2</sub>O<sub>4</sub> Synthesized by Solid-State Combustion Synthesis

Spinel LiMn2O4 cathode material was rapidly prepared by solid-state combustion synthesis which used lithium carbonate and manganese carbonate as raw materials and β-cyclodextrin as a fuel. The effects of amount of β-cyclodextrin and calcination temperature on their structure and electrochemical properties were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), galvanostatic charge-discharge test and cyclic voltammetry (CV). The optimal synthesis conditions were found to be 5 wt% β-cyclodextrin. Under these conditions, high-purity spinel LiMn2O4 was obtained, and its discharge specific capacity was 110.5 mAh/g in the first cycle and still retained at 99.9 mAh/g after 40 cycles.

Improvement of capacity and cycling performance of spinel LiMn2O4 cathode materials with TiO2-B nanobelts

The spinel LiMn2O4 was modified with TiO2-B nanobelts to improve its specific capacity and cycling performance. TiO2-B/LiMn2O4 composites were fabricated by a facile liquid phase mixing method. The morphology and structure of the samples were characterized by means of X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The results show that TiO2-B nanobelts are uniformly distributed in LiMn2O4 particle. Compared with bare LiMn2O4, TiO2-B/LiMn2O4 composite cathode material shows enhanced specific capacity of 129mAhg−1 and improved cycling stability. After 50 cycles, the 0, 0.5, 1.0, 2.0 and 3.0wt.% TiO2-B nanobelts modified LiMn2O4 exhibited the capacity retention of 86.1, 92.6, 93.7, 94.5 and 92.8%, respectively. The improvement of the electrochemical performance is attributed to suppression of Mn2+ dissolution, higher structural stability of the composite and rapid Li+ diffusion resulting from the open lattice channels and unique one-dimensional structure of TiO2-B nanobelts.

Structure and electrochemical performance of LiV x Mn2 − x O4 (0 ≤ x ≤ 0.20) cathode materials for rechargeable lithium ion batteries

LiMn2O4 and vanadium-substituted LiV x Mn2 − x O4 (x = 0.05, 0.10 0.15 and 0.20) cathode materials were synthesized by sol–gel method using aqueous solutions of metal nitrates and tartaric acid as chelating agent at 600 °C for 10 h. The structure and electrochemical properties of the synthesized materials were characterized by using X-ray diffraction, SEM, TEM and charge–discharge studies. X-ray powder diffraction analysis was changed in lattice parameters with increasing vanadium content suggesting the occupation of the substituent within LiMn2O4 interlayer spacing. TEM and SEM analyses show that LiV0.15Mn1.85O4 has a smaller particle size and more regular morphological structure with narrow size distribution than LiMn2O4. It is concluded that the structural stability and cycle life improvement were due to many factors like better crystallinity, smaller particle size and uniform distribution compared to the LiMn2O4 cathode material. The LiV0.15Mn1.85O4 cathode material has improved the structural stability and excellent electrochemical performances of the rechargeable lithium ion batteries.

Structure and electrochemical performance of surface modified LaPO4 coated LiMn2O4 cathode materials for rechargeable lithium batteries

LiMn2O4 spinel cathode materials were coated with 1.0, 2.0 and 3.0 wt% of LaPO4 by the polymeric process, followed by calcinations at 800 °C for 6 h in air. The structure and electrochemical properties of the surface modified LiMn2O4 materials were characterized by XRD, SEM, XPS, cyclic voltammetry and charge–discharge techniques. XRD patterns of LaPO4 coated LiMn2O4 revealed that the coating did not affect the crystal structure and space group Fd3m of the powder materials, compared to the uncoated LiMn2O4. XPS data illustrate that the LaPO4 was completely coated over the surface of the LiMn2O4 core materials. 2 wt% of LaPO4 coated LiMn2O4 cathode material exhibits specific capacity of 103 mAh/g (versus lithium metal) and excellent capacity retention (82% of its initial capacity) between 4.5 and 3 V after 100 cycles at elevated temperature (50 °C). LiMn2O4 coated with 0.0–3.0 wt% of LaPO4 has slightly decreased the initial capacity, but the cycling stability increased remarkably over 3–4.5 V. This result indicates that the surface treatment should be an effective way to improve the overall properties of the cathode materials for lithium ion batteries. Among them, 2 wt% of LaPO4 coated spinel LiMn2O4 cathode material has improved the structural stability, high reversible capacity at elevated temperature and excellent electrochemical performances of the rechargeable lithium batteries.