Lithium Manganite Research Articles

Lithium manganite anchored on mesoporous ceria photocatalyst for removal of Hg(II) ions from aqueous solution under visible illumination

The development of effective photocatalysts is critical for the photo/redox reaction of noxious Hg(II) ions and Hgo in environmental engineering and purification. In this contribution, Li2MnO3 nanoparticles (NPs) were anchored mesoporous CeO2 networks to design photocatalysts with high harvest of visible light, and the obtained Li2MnO3/CeO2 nanocomposites were utilized for photoreduction of Hg(II) ions under visible illumination. The TEM and XRD results showed the formation of Li2MnO3 and CeO2 with the monoclinic and cubic fluorite structures, and the particle size is about 10–20 nm. The enhancement of light absorption of Li2MnO3/CeO2 nanocomposites could create considerable photoinduced carriers during the photocatalytic reactions. The incorporation of Li2MnO3 and CeO2 NPs demonstrated outstanding photocatalytic performance compared with pristine CeO2 NPs, and the optimum 9%Li2MnO3/CeO2 nanocomposite achieved 98 % of the reduction Hg(II) ability within 60 min. The rate constant for 9 % Li2MnO3/CeO2 photocatalyst is ∼ 6.47 and 3.85 times greater than Li2MnO3 and CeO2 NPs. The superior photocatalytic performance of Li2MnO3/CeO2 nanocomposites was ascribed to the efficient separation of photocarriers due to the formation of S-scheme heterojunction, the large surface area, and mesoporous structures. The obtained Li2MnO3/CeO2 nanocomposite was highly stable and efficient for the Hg(II) photoreduction runs up to five successive experiments under similar conditions. Moreover, the possible mechanism over heterojunctions Li2MnO3/CeO2 nanocomposites toward the reduction of Hg(II) ions is examined as well. The formation of S-scheme heterojunction photocatalyst provides better photocatalytic applications in terms of air purification, hydrogen production, and water treatment.

Study on Modified High Voltage (5V) Spinel Lithium Manganate Used for Energy Storage Lithium Titanate Batteries

Solid electrolyte Li1.4Al0.4Ti1.6 (PO4)3 was used to coat high voltage (5V) spinel lithium manganate. The modified high voltage spinel lithium manganate was used as positive electrode and the lithium titanate as negative electrode. A type of 10Ah energy storage battery was assembled. Charge-discharge and cycle life tests of these batteries were carried out at different temperatures and rates. The results show that coating high voltage spinel lithium manganate improves the high temperature cycle performance of the lithium titanate batteries. The capacity retention ratio of the lithium titanate batteries with the coated high voltage lithium manganate as cathode material increases from 74.8% to 86.5% at 60°Cafter 2000 cycles compared to the lithium titanate batteries with the uncoated high voltage lithium manganite as cathode material. However, the cycle performance is not affected at-30 °C. The low temperature rate performance of lithium titanate batteries is improved by coating high voltage lithium manganate. When the discharge rate is 20 C at-30°C, 90.6% of the 1 C charge capacity at room temperature of the lithium titanate battery with the coated high voltage lithium manganate as cathode materialcan be delivered, while the lithium titanate battery with the un-coated high voltage lithium manganate as cathode material can only deliver 80.2% of the 1 C charge capacity at room temperature.

Defect Process, Dopant Behaviour and Li Ion Mobility in the Li2MnO3 Cathode Material

Lithium manganite, Li2MnO3, is an attractive cathode material for rechargeable lithium ion batteries due to its large capacity, low cost and low toxicity. We employed well-established atomistic simulation techniques to examine defect processes, favourable dopants on the Mn site and lithium ion diffusion pathways in Li2MnO3. The Li Frenkel, which is necessary for the formation of Li vacancies in vacancy-assisted Li ion diffusion, is calculated to be the most favourable intrinsic defect (1.21 eV/defect). The cation intermixing is calculated to be the second most favourable defect process. High lithium ionic conductivity with a low activation energy of 0.44 eV indicates that a Li ion can be extracted easily in this material. To increase the capacity, trivalent dopants (Al3+, Co3+, Ga3+, Sc3+, In3+, Y3+, Gd3+ and La3+) were considered to create extra Li in Li2MnO3. The present calculations show that Al3+ is an ideal dopant for this strategy and that this is in agreement with the experiential study of Al-doped Li2MnO3. The favourable isovalent dopants are found to be the Si4+ and the Ge4+ on the Mn site.

A layered-spinel lithium manganite hydrate for high-capacity and ultrafast lithium storage

Multi-phase integration and structural hydration are effective material design strategies for advanced electrode materials with high capacity and fast lithiation. Herein, a novel layered-spinel lithium manganite hydrate is successfully synthesized through a one-step hydrothermal lithiation process. Structure characterizations, electrochemical properties, reaction mechanisms and kinetic analysis are investigated in detail. The layered-spinel coexistence, stable intercalated water, abundant interfaces/defects and mesoporous architectures comprising 2D nanosheets help to shorten the Li-ion transport pathway, promote electronic/ion conductivity, increase Li storage sites and maintain structural stability. With combined diffusion-controlled and pseudocapacitive reaction mechanisms, the layered-spinel lithium manganite hydrate exhibits superior electrochemical behaviors, showing great potentials for high-capability and ultrafast lithium storage. The comprehensive utilization of multi-phase integration and structural hydration promotes the diversity of material and structure systems, and further paves new way for the design of other high-performance electrode materials.

High‐performance Li‐ion Battery based on Cr‐Substituted Lithium Manganite and Lithium Titanate Spinels: Influence of Mass Balance on its Electrochemistry

AbstractThe influence of mass balance in the LiCr0.2Ni0.4Mn1.4O4//Li4Ti5O12 (LCrNMO//LTO) full cell on its electrochemical performance at different rates is described. The effect of the variation of the molar fraction of LTO to LCrNMO (χ) at different rates is described in detail. The full cell showed a reversible working potential at about 3 V. For every rate tested, the discharge capacity, normalized to total mass of both electrode materials (Qdch), reached a maximum value approximately at the stoichiometric value of χ=1. When χ<1, Qdch is limited by an incomplete electrochemical reaction of the LCrNMO cathode and when χ>1 Qdch decreases due to the increase in the total weight of active electrode materials. When the discharge rates were increased to ≥1 C (1 C=147.5 mA g−1 or 0.260 mA cm−2), the maximum Qdch delivered by the full cell was shifted slightly beyond the stoichiometry (χ=1.1). Furthermore, the LCrNMO//LTO full cell exhibited an outstanding ultralong cycling behavior: with a capacity retention of 93 % after 1000 cycles. Its cyclability is as high as 99.994 %. The LiCrNMO//LTO full cell is a promising lithium‐ion battery for practical applications, especially for plug‐in hybrid electric vehicles, for which a long cycle life and reasonable power are required. However, it is demonstrated that the optimization of anode to cathode materials is one of the most important parameters to take into account to achieve high energy and power densities.

Structure and electrochemical performance of cobalt oxide layer coated on LiNi0.03Mn1.97O4 cathode materials

The composite cathode materials were fabricated by means of a thermal decomposition method combining a modified sol-gel method. The composite cathode-based cells exhibits improved electrochemical properties compared to the pristine lithium manganite cathode both at room temperature and boosted temperature. The cobalt oxide (Co3O4) characterized by the thermogravimetry play a protecting role from disproportionation manganese reaction and the considerable coating amount was 2% summarized from the electrochemical results. The cobalt oxide coating layer and the nickel doping ions showed a synergistic effect to ameliorate the electrochemical performance and the 2% coating combine with nickel doping cathode delivers the discharge capacity of 114.3 mAhg−1 at current density of 148 mA/g with retention of 92.7% after 100th cycle as well as the rate capability. As what the results revealed that the cobalt oxide coating combined with nickel doping could be a considerable approach to improve the lithium manganate electrochemical properties and worth of further studies.

The role of SnO2 surface coating in the electrochemical performance of Li1.2Mn0.54Co0.13Ni0.13O2 cathode materials

The manganese metal ions and other transition metal ions in lithium manganite cathode materials will be dissolved into the electrolyte during cycling and storage at charged state, leading to severe capacity fading. Herein, the SnO2-coated Li1.2Mn0.54Co0.13Ni0.13O2 cathode material is prepared successfully by a simple organic liquid-phase method. The data of inductive coupled plasma-atomic emission spectroscopy and ex-XRD suggest that the coating layer can effectively suppress the dissolution of metal ions, which maintains the stability of main structure. The value of the charge transfer impedance is 35.49 Ω cm2 for LLMO-Sn1 after 50 cycles, while the LLMO is 123.30 Ω cm2. The LLMO-Sn1 has the highest discharge capacity of 214.0 mAh·g−1 after 150 cycles in half cell and exhibits the capacity retention of 86.8% after 150 cycles in full-cell. The decomposition reaction peak of LLMO-Sn1 appears at 250.1 °C.

Storage Fading Mechanism of a Commercial 18650 Cell Comprised with Composite NMC/LMO Cathode and Graphite Anode

In this study, the capacities and electrochemical impedances at various states of charge (SOC) are measured after the screened commercial 18650 lithium ion cells assembled with composite cathode of layered mixed oxide (NMC) and spinel lithium manganite (LMO) and graphite anode were stored at various states of depth-of-discharge (DOD) at various temperatures for various durations. The results manifest that the capacity fading is strongly affected by the storage temperature and becomes prominent at temperatures higher than 45oC. Incremental capacity analyses (ICA) for the charge/discharge curves before and after storage were performed for the qualitative mechanism study. It demonstrates that the capacity fade of the cell stored at 60oC and 0% DOD can be attributed to the loss of active materials, and the loss of graphite anode is higher than that of composite cathode. The capacity fade of the cell stored at 60oC and 25% DOD can be caused by the lithium inventory loss, the loss of NMC, and the loss due to the morphology change of LMO. Cell stored at 50% DOD manifests similar fading behavior as that of the cell stored at 0% DOD, however, the ICA plots demonstrate that the capacity loss of the cell comes from losses of lithium inventory and NMC caused by the dissolution of transition metals with additional losses of LMO and graphite anode occur after 10 months of accumulated storage. For cell stored at 75% DOD, most the capacity loss can be due to the loss of NMC with minor contribution of lithium inventory loss, while cell stored at 100% DOD shows almost no change after storage for 12 accumulated months. These results revealed from the ICA study are consistent with those determined from the post mortem study of the electrodes obtained from cells before and after storage.

Lithium-ion Battery Electro-thermal Model and Its Application in the Numerical Simulation of Short Circuit Experiment

As a key issue in EVs (Electric Vehicles) development, Li-ion battery’s thermal safety is focused on in which the thermal abuse model is an important tool. This paper has established a 3-D electro-thermal model taking side reaction into account, in order to study on MGL100Ah lithium manganite battery’s safety issue. This paper firstly states the mechanism of heat generation, types of thermal model, and the mesh model, then analyzes the simulation on the model under the short circuit condition, one of thermal abuse condition. On one hand, the paper verifies the liability of the model, so as to apply the model on other thermal abuse condition in the future; on the other hand, the paper discusses in detail the internal temperature distribution, voltage and current changes under the short circuit condition. Analyzing this typical safety issue in details, this paper can help reduce cost, raise design efficiency and avoid thermal abuse in future development of battery.

Magnetism of LiMn2O4 manganite in structurally ordered and disordered states

The specific features of the crystal structure and the magnetic state of stoichiometric lithium manganite in the structurally ordered Li[Mn2]O4 and disordered Li1 − δMnδ[Mn2 − δLiδ]O4 (δ = 1/6) states have been investigated using neutron diffraction, X-ray diffraction, and magnetic methods. The structurally disordered state of the manganite was achieved under irradiation by fast neutrons (E eff ≥ 1 MeV) with a fluence of 2 × 1020 cm−2 at a temperature of 340 K. It has been demonstrated that, in the initial sample, the charge ordering of manganese ions of different valences arises at room temperature, which is accompanied by orthorhombic distortions of the cubic spinel structure, and the long-range antiferromagnetic order with the wave vector k = 2π/c(0, 0, 0.44) is observed at low temperatures. It has been established that the structural disordering leads to radical changes in the structural and magnetic states of the LiMn2O4 manganite. The charge ordering is destroyed, and the structure retains the cubic symmetry even at a temperature of 5 K. The antiferromagnetic type of ordering transforms into ferrimagnetic ordering with local spin deviations in the octahedral sublattice due to the appearance of intersublattice exchange interactions.

Effects of structural disorder in lithium manganite and titanate oxides

The structures and magnetic states of stoichiometric lithium manganite LiMn2O4 and manganites and titanates Li1.33Mn1.67O4 and Li1.33Ti1.67O4 with excess lithium in both the initial (as-synthesized) state and after irradiation by fast (Eeff ≥ 1 MeV) neutrons with a fluence of 2 × 1020 cm−2 have been studied using neutron diffraction, X-ray diffraction, and magnetic methods. It has been established that the irradiation brings about a noticeable redistribution of manganese, titanium, and lithium cations over nonequivalent tetrahedral (8a) and octahedral (16d) positions of a spinel lattice. This structural disorder causes a radical change in the physical properties of the materials under study. The charge order existing in the initial LiMn2O4 sample is destroyed. There arises a strong intersublattice indirect exchange interaction Mn(8a)-O-Mn(16d). The disorder is accompanied by the antiferromagnet-ferrimagnet (LiMn2O4) and paramagnet-ferrimagnet (Li1.33Mn1.67O4) magnetic transitions.

Low-dimensional exchange interactions, structural deformation, and antiferromagnetic ordering in lithium manganite LiMnO2

Structure deformation in lithium manganite LiMnO2 has been analyzed. It is shown that suppression of the Jahn-Teller effect with a decrease in temperature is related to striction effects, which are caused by intercluster exchange interactions. It is concluded that low-dimensional interactions play an important role in the formation of magnetic properties of lithium manganite.

Peculiarities of antiferromagnetic ordering in orthorhombic LiMnO2

Data on the antiferromagnetic ordering in orthorhombic lithium manganite LiMnO2 are obtained from magnetic-susceptibility, calorimetry, and nuclear magnetic resonance studies. The minimal hysteresis and the absence of jumps in the temperature dependences of the sublattice magnetization M(T) and the magnetic susceptibility near TN indicate that the ordering occurs through a continuous second-order phase transition. Within the critical temperature range, the M(T−TN) variation is satisfactorily described by a power-law dependence with a critical exponent β = 0.25(4), which is substantially smaller than that predicted for 3D magnetic systems with isotropic Heisenberg exchange. The band structure of orthorhombic LiMnO2 is calculated using the LMTO-ASA method. Taking into account the spin states of manganese ions, an adequate pattern is obtained for the density-of-states distribution with an energy gap near the Fermi level (∼0.7 eV), which is in agreement with the measured electrical parameters of lithium manganite. The calculations demonstrate that the exchange interactions between Mn3+ ions leading to antiferromagnetic ordering are significantly anisotropic. It is found that small paramagnetic regions persist in the manganite below the Neel temperature, and it is concluded that the reason for this is partial structural disordering of LiMnO2. As a result, a certain fraction of the manganese positions is occupied by lithium ions (LiMn) and vise versa (MnLi). These defects are not involved in the formation of the ordered magnetic structure and compose a paramagnetic fraction.

Magnetic transformations and structural disorder in lithium manganite LiMnO2

Investigation of the structural and magnetic characteristics of lithium manganite LiMnO2 with a variable Li/Mn ratio has been performed. A significant difference in the 7Li NMR spectra in the paramagnetic and antiferromagnetic manganite phases is revealed. It is shown that the common feature of the compositions studied is a high degree of structural disorder, which manifests itself in the presence of manganese ions in lithium positions (MnLi) and lithium ions in manganese positions (LiMn); this effect is also characteristic of the stoichiometric composition.