Spinel Lithium Manganese Oxide Research Articles

Effect of Manganese Vanadate Formed on the Surface of Spinel Lithium Manganese Oxide Cathode on High Temperature Cycle Life Performance

Rate capability and cyclability of <TEX>$LiMn_2O_4$</TEX> should be improved in order to use it as a cathode material of lithium-ion batteries for hybrid-electric-vehicles (HEV). To enhance the rate capability and cyclability of <TEX>$LiMn_2O_4$</TEX>, it was coated with <TEX>$MnV_2O_6$</TEX> by a sol-gel method. A <TEX>$V_2O_5$</TEX> sol was prepared by a melt-quenching method and the <TEX>$LiMn_2O_4$</TEX> coated with the sol was heat-treated to obtain the <TEX>$MnV_2O_6$</TEX> coating layer. Crystal structure and morphology of the samples were examined by X-ray diffraction, SEM and TEM. The electrochemical performances, including cyclability at <TEX>$60^{\circ}C$</TEX>, and rate capability of the bare and the coated <TEX>$LiMn_2O_4$</TEX> were measured and compared. Overall, <TEX>$MnV_2O_6$</TEX> coating on <TEX>$LiMn_2O_4$</TEX> improves the cyclability at high temperature and rate capability at room temperature at the cost of discharge capacity. The improvement in cyclability at high temperature and the enhanced rate capability is believed to come from the reduced contact between the electrode, and electrolyte and higher electric conductivity of the coating layer. However, a dramatic decrease in discharge capacity would make it impractical to increase the coating amount above 3 wt %.

Synthesis of high-purity LiMn2O4 with enhanced electrical properties from electrolytic manganese dioxide treated by sulfuric acid-assisted hydrothermal method

Using sulfuric acid-assisted hydrothermal treatment, β-MnO2 particles were obtained from the electrolytic manganese dioxide (EMD). Via high-temperature solid-phase reactions, spinel lithium manganese oxides (LiMn2O4) were produced using the obtained β-MnO2 particles as precursor mixed with LiOH·H2O for the lithium-ion battery cathodes. Atomic absorption (AAS) shows that after the hydrothermal treatment, the contents of impurity ions, such as Na+, K+, Ca2+, and Mg2+, caused by the limitation of preparation technology of EMD are greatly reduced. X-ray diffraction and scanning electron microscopy show that β-MnO2 is highly alloyed consisting of nano sticks. Spinel lithium manganese (LiMn2O4) synthesized by the β-MnO2 precursor has high crystallinity with a well 111 face grow and presents a regular and micron-sized octagonal crystal. When used as cathode materials for lithium-ion batteries, LiMn2O4 synthesized by the β-MnO2 precursor has greater discharge capacity, better cycle performance, and better high-rate capability when compared with LiMn2O4 synthesized by the EMD precursor. Cyclic voltammetry and electrochemical impedance spectroscopy indicate that LiMn2O4 synthesized by the β-MnO2 precursor has better electrochemical reaction reversibility, greater peak current, higher lithium-ion diffusion coefficient, and lower electrochemical impedance.

Synthesis, Structure, and Electrochemistry of Sm-Modified LiMn2O4 Cathode Materials for Lithium-Ion Batteries

Spinel lithium manganese oxide and a series of Sm/LiMn2O4 spinels with different Sm additive contents (x = 0.02%, 0.05%) were prepared for the first time via a coprecipitation method for rechargeable lithium-ion batteries. X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive analysis of x-rays (EDAX), infrared (IR), and electron spin resonance spectral studies as well as various electrochemical measurements were used to examine the structural and electrochemical characteristics of LiMn2−xSmxO4 (x = 0.00%, 0.02%, 0.05%). XRD and SEM studies confirmed the nano materials size for all prepared spinels. From cyclic voltammetry studies, in terms of peak splitting, electrochemical active surface area, and intensity of the peaks, the LiMn1.98Sm0.02O4 sample possesses better electrochemical performance compared with the LiMn1.95Sm0.05O4 sample. Hence, limited addition of a rare-earth dopant is preferable to obtain better efficiency. Direct-current (DC) electrical conductivity measurements indicated that these samples are semiconducting and their activation energies decrease with increasing rare-earth Sm3+ content.

Synthesis and properties of LiMn2O4 from hydrazine hydrate reduced electrolytic manganese dioxide

Using N2H4·H2O as reductant γ-Mn3O4 particles were obtained from the electrolytic manganese dioxide (EMD). Via high temperature solid-phase reactions, spinel lithium manganese oxide (LiMn2O4) was produced using the obtained γ-Mn3O4 as precursor mixed with LiOH⋅H2O for the lithium ion battery cathodes. Atomic absorption (AAS) shows that after the liquid-phase reduction reaction the impurity ions, such as Na+, K+, Ca2+, and Mg2+, are greatly reduced. X-ray diffraction (XRD) and scanning electron microscopy (SEM) show that γ-Mn3O4 has high crystallinity and uniform size-distribution. Spinel lithium manganese (LiMn2O4) synthesized by the γ-Mn3O4 precursor has a high crystallinity and the (111) face grows perfectly with a regular and micron-sized octagonal crystal. The electrochemical tests show that LiMn2O4 synthesized by the γ-Mn3O4 precursor has greater discharge capacity, better cycle performance, and better high-rate capability compared with LiMn2O4 synthesized by the EMD precursor. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) indicate that LiMn2O4 synthesized by the γ-Mn3O4 precursor has a better electrochemical reaction reversibility, greater peak current, higher lithium-ion diffusion coefficient, and lower electrochemical impedance. Furthermore, this synthesis process is simple, of low-cost, and easy for a large-scale production.

Synthesis and Characterization of Nanosized of Spinel LiMn2O4via Sol-gel and Freeze Drying Methods

Nanocrystalline spinel lithium manganese oxide (<TEX>$LiMn_2O_4$</TEX>) powders with narrow-size-distribution, pure-phase particles, and high crystallinity with an average crystallite size of about 70 nm were synthesized at <TEX>$600^{\circ}C$</TEX> for 6 h in air by freeze drying method. Spinel <TEX>$LiMn_2O_4$</TEX> is also prepared by sol-gel using citric acid as a chelating agent. The influence of different parameters such as pH conditions, solvent, molar ratio of citric acid to total metal ions, calcination temperature, starting material on the structure, morphology and purity of this oxide was investigated. The results of sol-gel method show that pure <TEX>$LiMn_2O_4$</TEX> with average crystallite size of about 130 nm can be produced from nitrate salts as starting materials at <TEX>$800^{\circ}C$</TEX> for 6 h in air. The optimum pH and molar ratio of chelating agent to total metal ions are <TEX>$4{\leq}pH{\leq}6$</TEX> and 1.0, respectively. A possible mechanism on the formation of the nanocrystallines synthesized by sol-gel was also discussed. At the end a comparison of the differences between two methods was made on the basis of x-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA) tests.

Contribution of oxygen partial density of state on lithium intercalation/de-intercalation process in LixNi0.5Mn1.5O4 spinel oxides

The electronic structural changes during lithium-ion intercalation/de-intercalation process of nickel substituted lithium manganese spinel oxides have been investigated by using X-ray absorption near-edge structure (XANES) spectra of O K-edges as well as Ni L3-edges and Mn L3-edges. The results of the XANES spectra indicate that the electronic structure of both manganese and oxygen atoms contribute on the redox reaction at 0.06 ≤ x < 1, and only that of nickel atom affect the redox reaction at 1 < x ≤ 1.78 in LixNi0.5Mn1.5O4. Thus, the electronic structural change of oxygen atom is also crucial for considering redox reaction at intercalation/de-intercalation process, and the contribution of the oxygen atom on redox reaction differs in various redox cation species.

Pressure dependence of magnetic transition temperature in Li[LixMn2−x]O4 (0 ≤ x ≤ 1/3) studied by muon-spin rotation and relaxation

In order to study a change in electrochemical, structural, and magnetic properties for lithium manganese oxide spinels Li[LixMn2−x]O4 (LMO) with 0 ≤ x ≤ 1/3, muon-spin rotation and relaxation (μSR) spectra were recorded under pressure (P) up to 2.1 GPa. At ambient P, P = 0.1 MPa, the antiferromagnetic or spin-glass-like transition temperature (Tm) at P = 0.1 MPa monotonically decreases with increasing x. On the contrary, the slope of the Tm vs. P (dTm/dP) rapidly increases from 0.9(1) K/GPa at x = 0 to 1.4 K/GPa at x = 0.1, then drops to 0.7(1) K/GPa at x = 0.15, and finally keeps constant (∼0.4 K/GPa) with further increasing x. Considering the structural change of LMO with x, the decrease in the distance between Mn ions (dMn-Mn) is likely to play an essential role for determining Tm under P. According to cyclic voltammetry on LMO, the peak current at both anodic and cathodic directions shows the maximum at x = 0.1, indicating the highest diffusivity of Li+ ions (DLi) at x = 0.1.

Preparation and Characterization of a Cylinder-Type Adsorbent for the Recovery of Lithium from Seawater

In this work, a spinel lithium manganese oxide (LMO) used as a lithium adsorbent was prepared with a conventional solid state reaction using lithium carbonate and manganese carbonate as the reactants. A cylinder-type LMO was prepared using water glass (sodium silicate solution) as a binder together with the reactants and examined for its lithium adsorption capacity. The effect of the preparation condition on the adsorption capacity of the LMO powder was investigated. The optimum heating condition for the LMO powder, determined to be 500°C for 4 h, was applied to prepare the cylinder-type LMO. The cylinder-type LMO showed a maximum adsorption capacity of 15.06mg/g when immersed in lithium-enriched seawater, whereas LMO powder showed a maximum adsorption capacity of 27.62mg/g under identical conditions. The cylinder-type LMO generally maintained its structure after the acid treatment and the Li adsorption process. Thus, the cylinder-type LMO developed in this study can overcome the limits associated with powder-type adsorbents and may be appropriate for multiple adsorption runs in seawater. [doi:10.2320/matertrans.M2013028]

Chemical mixing in molten-salt for preparation of high-performance spinel lithium manganese oxides: Duplication of morphology from nanostructured MnO2 precursors to targeting materials

The chemical mixing strategy involving molten-salt lithiation at 450°C and post-annealing at 800°C on formation of morphological replica of spinel lithium manganese oxides from nanostructured potassium-contained manganese oxides has been discussed in terms of influences of Li/Mn stoichiometry during molten-salt mixing, crystal phases and microstructure of precursory nanostructured MnO2. It is exhibited that α-MnO2 with suitable-sized one-dimensional tunnels in lattices facilitates the formation of chemical-level mixture of Li, Mn and O, and ensuring morphological retention after molten-salt lithiation. Compared to α-MnO2, the interlayer gap in δ-MnO2 crystal lattices is too large to ensure chemical-level mixture or morphology retention. It is suggested that the precursory Li/Mn ratio during molten-salt treatment should be prudently controlled, aiming to restraining excessive surface-absorption of Li and facilitating an effective Li/K exchange process. Also, one-dimensional nanoarchitectured precursory manganese oxide is advantageous over its nanoparticle counterparts on morphological retention after post-annealing process, due to its the enhanced stability against large local strains. Electrochemical measurements show that the prepared phase-pure and highly crystalline spinel-typed lithium manganese oxide nanorods in morphological replica of precursory α-MnO2 nanorods deliver a reversible specific capacity 94mAhg−1 upon 200 times of charge–discharge cycling at a rate of 10C.

Thermal expansion in lithium manganese oxide spinels Li[LixMn2−x]O4 with 0 ≤ x ≤ 1/3

In order to know the coefficients of thermal expansion in lithium manganese oxide spinels Li[LixMn2−x]O4 with 0 ≤ x ≤ 1/3, X-ray diffraction measurements are performed in the temperature (T) range from 400 to 100 K. The crystal structure for x = 0 changes from the high-T cubic phase (Fd3¯m) into the low-T orthorhombic phase (Fddd) below 285 K due to a cooperative the Jahn–Teller transition. Hence, the average coefficients of linear thermal expansion (αL) in x = 0 are very different between the three orthorhombic axes; αL = 1.3(1) × 10−6 K−1 along the ao-axis, αL = 13.1(1) × 10−6 K−1 along the bo-axis, and αL = 5.7(1) × 10−6 K−1 along the co-axis, where ao, bo, and co are the lattice parameters of orthorhombic phase. On the other hand, the crystal structure for the samples with x ≥ 0.05 keeps the cubic phase (Fd3¯m) down to 100 K. The αL value is almost independent on x at x ≥ 0.05, i.e. αL ∼ 7.0 × 10−6 K−1. This suggests that the bond strength between Mn(Li) and O2− ions does not increase by the partial substitution of Li ions for Mn ions.

Millimeter-sized spherical ion-sieve foams with hierarchical pore structure for recovery of lithium from seawater

Millimeter-sized spherical ion-sieve foams (SIFs) were prepared from spinel lithium manganese oxide (LMO) via a combined process of foaming, drop-in-oil, and agar gelation to recover the lithium from natural seawater. The spinel structure of the fabricated SIFs was induced by H+–Li+ ion exchange after acid treatment, and the SIFs were found to exhibit hierarchical trimodal pore structure. Small and large bimodal mesopores were formed from the acid treatment-induced agar removal, and macropores from the bubble-template. Increasing agar content during the fabrication process led to an increase in the specific surface area and mesopore volume of the SIFs, but a decrease in the macropore volume. The amount of lithium adsorption in the LiOH solution was significantly decreased with increasing agar content during the fabrication process, probably because the SIFs fabricated with lower agar content possessed more open pores, which in turn increased the contact probability with the hierarchical structure developed in the inner parts of the SIFs. The SIFs with the lowest agar content exhibited greatest lithium adsorption capacity in natural seawater of 3.4mgg−1, and the adsorption and desorption efficiency were almost unaffected even after five adsorption–desorption cycles.

Degradation of spinel lithium manganese oxides by low oxidation durability of LiPF6-based electrolyte at 60 °C

The manganese dissolution behavior of lithium hexafluorophosphate (LiPF6) dissolved in carbonate-based organic solvents is investigated by ex situ field emission scanning electron microscope (FE-SEM), Fourier transform infrared (FT-IR), X-ray diffraction (XRD), and inductively coupled plasma (ICP). It is found that the LiPF6 salt anions in the electrolytes are prone to oxidize upon contacting delithiated lithium manganese oxide with high oxidizing power and the electrons that evolved from the oxidation of anions are consumed in the reduction of tetravalent manganese ions to trivalent manganese ions at 60°C. The generated trivalent manganese ions readily undergo a disproportion reaction and thereby release divalent manganese ions into the electrolytes, which leads to a capacity loss in the lithium manganese oxide cathode.

구형 스피넬계 LiMxMn2-xO4(M = Al, Mg, B) 양극소재의 입자치밀도와 전지성능간의 상관관계에 대한 연구

본 연구에서는 습식분쇄, 구형화 분무건조 및 열처리 공정을 통해 구형의 <TEX>$LiMn_{2-x}M_xO_4$</TEX>(M = Al, Mg, B) 스피넬계 양극소재를 합성하고, 이의 전기화학적 성능을 평가하였다. <TEX>$MnO_2$</TEX> (Tosoh, 91.94%), <TEX>$Li_2CO_3$</TEX> (SQM, 97%), <TEX>$MgCO_3$</TEX> (Aldrich, 99%), <TEX>$Al(OH)_3$</TEX> (Aldrich, 99%) 및 <TEX>$B_2O_3$</TEX> (Aldrich, 99%)를 원료로 사용하였으며, 분무건조공정에서 전구체의 구형화도 증가를 위해 PAAH 바인더를 첨가하였다. 200~500 nm 크기로 분쇄된 혼합 슬러리 용액으로부터 분무건조법을 통해 구형의 전구체를 제조하고, 이를 다양한 조건에서 열처리하여 최종 스피넬계 <TEX>$LiMn_{2-x}M_xO_4$</TEX> (M = Al, Mg, B) 양극소재를 제조하였다. 제조된 구형의 <TEX>$LiMn_{2-x}M_xO_4$</TEX> (M = Al, Mg, B) 양극재료는 이종원소 치환량, 특히 Boron 치환량에 따라 입자 표면 및 내부의 치밀도가 변화하는 것을 확인할 수 있었으며, 치밀도가 증가함에 따라 소재의 출력특성이 향상되었으며, 최적 조성의 양극소재는 상온 5 C 용량이 0.2 C 용량 대비 90% 이상이 됨을 확인하였다. 또한 표면의 치밀도도 증가함에 따라 <TEX>$60^{\circ}C$</TEX> 고온 충방전 조건에서 수명특성이 향상되어 500회 사이클 이후에도 초기용량의 80% 이상을 유지하였다. Spherical lithium manganese oxide spinel, <TEX>$LiMn_{2-x}M_xO_4$</TEX> (M = Al, Mg, B) prepared by wet-milling, spray-drying, and sintering process has been investigated as a cathode material for lithium ion batteries. As-prepared powders exhibit various surface morphologies and internal density in terms of boron (B) doping level. It is found that the dopant B drives the growth of the primary particle and minimizes the surface area of the powder. As a result, the dopant enhances the internal density of the particles. Electrochemical tests demonstrated that the capacity of the synthesized material at 5 C could be maintained up to 90% of that at 0.2 C. The cycle performance of the material showed that the initial capacity was retained up to 80% even after 500 cycles under the high temperature of <TEX>$60^{\circ}C$</TEX>.

Diode laser heat treatment of lithium manganese oxide films

The crystallization of lithium manganese oxide thin films prepared by radio frequency magnetron sputtering on stainless steel substrates under 10Pa argon pressure is demonstrated by a laser annealing technique. Laser annealing processes were developed as a function of annealing time and temperature with the objective to form an electrochemically active lithium manganese oxide cathode. It is demonstrated, that laser annealing with 940nm diode laser radiation and an annealing time of 2000s at 600°C delivers appropriate parameters for formation of a crystalline spinel-like phase. Characteristic features of this phase could be detected via Raman spectroscopy, showing the characteristic main Raman band at 627cm−1. Within cyclic voltammetric measurements, the two characteristic redox pairs for spinel lithium manganese oxide in the 4V region could be detected, indicating that the film was well-crystallized and de-/intercalation processes were reversible. Raman post-analysis of a cycled cathode showed that the spinel-like structure was preserved within the cycling process but mechanical degradation effects such as film cracking were observed via scanning electron microscopy. Typical features for the formation of an additional surface reaction layer could be detected using X-ray photoelectron spectroscopy.

Spinel Lithium Manganese Oxide Synthesized under a Pressurized Oxygen Atmosphere

not Available.

Laser microstructuring and annealing processes for lithium manganese oxide cathodes

It is expected that cathodes for lithium-ion batteries (LIB) composed out of nano-composite materials lead to an increase in power density of the LIB due to large electrochemically active surface areas but cathodes made of lithium manganese oxides (Li–Mn–O) suffer from structural instabilities due to their sensitivity to the average manganese oxidation state. Therefore, thin films in the Li–Mn–O system were synthesized by non-reactive radiofrequency magnetron sputtering of a spinel lithium manganese oxide target. For the enhancement of the power density and cycle stability, large area direct laser patterning using UV-laser radiation with a wavelength of 248nm was performed. Subsequent laser annealing processes were investigated in a second step in order to set up a spinel-like phase using 940nm laser radiation at a temperature of 680°C. The interaction processes between UV-laser radiation and the material was investigated using laser ablation inductively coupled plasma mass spectroscopy. The changes in phase, structure and grain shape of the thin films due to the annealing process were recorded using Raman spectroscopy, X-ray diffraction and scanning electron microscopy. The structured cathodes were cycled using standard electrolyte and a metallic lithium anode. Different surface structures were investigated and a significant increase in cycling stability was found. Surface chemistry of an as-deposited as well as an electrochemically cycled thin film was investigated via X-ray photoelectron spectroscopy.

Simulation of the surface structure of lithium manganese oxide spinel

Simulations of the surface structure of low-index surfaces of LiMn${}_{2}$O${}_{4}$ (LMO), a candidate Li-ion battery electrode material, have been performed within the $\text{GGA}+U$ approximation, using the VASP code. Surfaces of (001), (110), and (111) orientation were considered, with at least two terminations treated in each case. A slab geometry was employed, with termination-layer vacancies introduced to remove the bulk dipole moment while maintaining ideal stoichiometry. To complement static-structure relaxation calculations, molecular-dynamics simulations were performed to explore the phase space of possible surface reconstructions. A reconstruction is predicted for the Mn-terminated (111) surface, in which the top layers mix in stoichiometric proportions to form an LMO termination layer with square-planar-coordinated Mn. Average surface Mn oxidation states are reduced, relative to the bulk, for all surfaces considered, as a consequence of the lower-energy cost of Jahn-Teller distortion at the surface. Threefold-coordinated surface Mn, found for two terminations, is divalent, which may enhance its vulnerability to dissolution. The Li-terminated (001) surface is lowest in energy, consistent with previous classical-potential simulations for MgAl${}_{2}$O${}_{4}$ that showed the Mg-terminated (001) surface to be lowest in energy.

Investigation of positive electrode materials based on MnO2 for lithium batteries

Various composite materials of MnO 2/C have been synthesized by electrochemical deposition and then used for the synthesis of lithium manganese oxide (LiMn 2 O 4) spinel as a cathode material for lithium ion batteries. The structure and electrochemical properties of electrode materials based on MnO 2/C, spinel LiMn 2 O 4 and doped spinel LiNi 0.5 Mn 1.5 O 4 have been studied. The influence of synthesis conditions on the structural and electrochemical properties of synthesized materials was investigated by x-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electronic microscopy (TEM) and charge–discharge experiments. Some of the studied materials exhibit good performance of cycling and discharge capacity.

Charge–discharge rate of spinel lithium manganese oxide and olivine lithium iron phosphate in ionic liquid-based electrolytes

Rate capability of Li/spinel LiMn2O4 or olivine LiFePO4 positive electrode cells containing mixed imidazolium ionic liquids electrolytes has been investigated under comparison with conventional organic solvent electrolyte and piperidinium ionic liquid. The LiMn2O4 electrode provides variation of rate capabilities among the ionic liquid electrolytes, while ionic liquid electrolytes provide similar extent of capacity degradation under high rate compared with organic solvent electrolyte for LiFePO4 electrode. Such differences in electrolyte dependences of the rate capabilities can be explained in relation to parameters in the high frequency resistances on AC impedance, assumed as interfacial resistances. The rate capability of LiMn2O4 is somewhat related to the activation energy of the high frequency resistance, while for LiFePO4 the resistance value appears to contribute to the rate capability.

A Study on the Cause of Deterioration in Float-Charged Lithium-Ion Batteries Using LiMn2O4 as a Cathode Active Material

The deterioration mechanism of float-charged lithium-ion batteries with lithium manganese oxide spinel as the cathode active material was investigated in order to improve battery lifetime, which is especially important for Li-ion batteries used in backup applications. After lengthy charging at a constant voltage, the cathodes and anodes of deteriorated batteries were tested electrochemically and analyzed. The capacity deterioration of the anode was 18.4%, and that of the cathode was 5.7%, although the reduction in the cell capacity was 41.9%. Electron probe microanalysis revealed the manganese deposition on the anode, suggesting that the reduction in battery capacity was caused by a decrease in the number of mobile lithium ions because the manganese deposition may occur instead of lithium insertion into the anode during charging. However, a precise comparison of the decrease in the number of mobile lithium ions caused by the manganese deposition and the battery capacity reduction showed that the capacity reduction cannot be explained by the manganese deposition alone. Side reactions related to the deposited manganese that accompanies the loss of electric charge may be occurring at the anode as well.