Spinel LiMn2O4 Research Articles

Analysing the Implications of Charging on Nanostructured Li2MnO3 Cathode Materials for Lithium-Ion Battery Performance.

Capacity degradation and voltage fade of Li2MnO3 during cycling are the limiting factors for its practical use as a high-capacity lithium-ion battery cathode. Here, the simulated amorphisation and recrystallisation (A + R) technique is used, for generating nanoporous Li2MnO3 models of different lattice sizes (73 Å and 75 Å), under molecular dynamics (MD) simulations. Charging was carried out by removing oxygen and lithium ions, with oxygen charge compensated for, to restrain the release of oxygen, resulting in Li2−xMnO3−x composites. Detailed analysis of these composites reveals that the models crystallised into multiple grains, with grain boundaries increasing with decreasing Li/O content, and the complex internal microstructures depicted a wealth of defects, leading to the evolution of distorted cubic spinel LiMn2O4, Li2MnO3, and LiMnO2 polymorphs. The X-ray diffraction (XRD) patterns for the simulated systems revealed peak broadening in comparison with calculated XRD, also, the emergence of peak 2Θ ~ 18–25° and peak 2Θ ~ 29° were associated with the spinel phase. Lithium ions diffuse better on the nanoporous 73 Å structures than on the nanoporous 75 Å structures. Particularly, the Li1.00MnO2.00 shows a high diffusion coefficient value, compared to all concentrations. This study shed insights on the structural behaviour of Li2MnO3 cathodes during the charging mechanism, involving the concurrent removal of lithium and oxygen.

Spinel LiMn2O4 with Remarkable Electrochemical Performances by Synergistic Enhancement of Double-Cation (Sm3+, Mo6+) Doping for Li-Ion Batteries

Spinel LiMn2O4 with Remarkable Electrochemical Performances by Synergistic Enhancement of Double-Cation (Sm3+, Mo6+) Doping for Li-Ion Batteries

Engineering d-p orbital hybridization for high-stable lithium manganate cathode

Spinel LiMn2O4 is a prevalent cathode material due to its environmental benignities and high operating voltage. Nevertheless, capacity attenuation and structural collapse are still inevitable, caused by the native Jahn–Teller distortion and spontaneous disproportionation of Mn3+. Hereby, LiMn2O4 cathode with stable crystallographic structure is rationally designed based on valence-bond theory with introduction of Ru dopant. The enhanced orbital hybridization between Mn 3d and O 2p is successfully achieved owing to the reinforcing band coherency of Mn–O aroused from the electrostatic interaction between Mn and Ru atoms. Notably, the robust crystal structure framework is effectively reconstructed, which is beneficial for ameliorating phase evolution and inhibiting structural degradation substantiated by the state-of-the-art synchrotron X-ray absorption spectroscopy and in-situ X-ray diffraction. Concomitantly, LiO4 tetrahedron is effectively weakened, further facilitating the rapid Li+ diffusion kinetics intensively confirmed by theoretical calculations and electrochemical tests. Remarkably, the as-designed Ru-doped LiMn2O4 manifests splendid long cycling stability, affording a respectable capacity retention of 88.2 % after 200 loops. Given this, the intriguing work might inaugurate an explicit direction for rationally tuning the orbital hybridization towards advanced electrodes in alkali metal batteries.

Structure and interface modification via Gd boosting excellent high-temperature electrochemical performance of LiMn2O4

Spinel LiMn2O4 has become one of the most attractive cathode materials for electric vehicles due to its low cost, non-toxicity, and good electrochemical performance of high C-rates. While the rapid decay of capacity at high temperature limits its further development. In this article, it is demonstrated that Gd modification can achieve the dual-modification of bulk structure and surface to effectively improve the electrochemical performance of LiMn2O4 at high temperature. It is found that Gd modification can decrease the lattice parameters and strengthens the stability of Mn–O bonds, which can efficiently improve the capacity stability by inhibiting the dissolution of Mn3+ from the electrode to the electrolyte. Besides, the Gd modification also enables the formation of the Gd2O3 coating layer on the material surface, which can significantly reduce the interfacial impedance and lower the diffusion activation energy of lithium-ion. Therefore, Gd-modified samples show a better rate capability and longer cycle life, especially at high temperature. Among them, the sample with Gd of 6000 ppm exhibited the most excellent capacity retention ratio of 82.6% after 300 cycles at 55 °C, 1C (1C = 148 mA·g-1) in the voltage range of 3.0–4.3 V, with an initial discharge capacity of 124.9 mAh·g−1.

A new strategy to quickly synthetize true nanoparticles of the spinel LiMn2O4 by using a microwave-assisted hydrothermal route

Based on a microwave-assisted hydrothermal reaction, a new route is proposed to prepare highly pure true nanoparticles (≤15 nm) of the single-phase spinel LiMn2O4 (LMO) at a low temperature (140 °C) and short reaction time (5 min), using exclusively water-soluble reagents. The obtention of this material was confirmed by using different techniques such as X-ray diffractometry, Rietveld crystal structure refinement, inductively coupled plasma-atomic emission spectroscopy and high-resolution transmission electron microscopy. Electrochemical evaluations were performed by using cyclic voltammetry and galvanostatic charge and discharge tests. Only electrodes prepared from spinel LMO nanoparticles with an average size of ~15 nm showed electrochemical activity. From charge and discharge tests at a constant rate of C/5, the electrodes prepared from this active material exhibited an initial specific capacity of 128 mA h g–1 with a capacity retention of 95% after the 27th cycle. The hallmark of the synthesis route here described is the saving of energy while preparing truly nanoparticulate LMO with excellent chemical, structural and promising electrochemical properties.

Improved long cycle performance of LiMn2O4 cathode material by Ni-B co-doping combined with truncated octahedron morphology

The rapid capacity fading of spinel LiMn2O4 cathode materials still suffers from Jahn-Teller effect and Mn dissolution. Herein, various spinel LiMn1.90-xNi0.10BxO4 cathode materials with truncated octahedron morphology are obtained by a solid-state combustion method. Owing to the substitution of Ni-B dual-doping for Mn, the MnO6 octahedron in the LiMn2O4 generates a contraction that leads to the increased average Mn oxidation state and the suppressed Jahn-Teller effect. Simultaneously, the expansive LiO4 tetrahedron is conducive to boosting the fast Li+ diffusion. Moreover, the growth of {110} crystal planes in the LiMn1.90-xNi0.10BxO4 (x = 0.02–0.15) is also restrained by the Ni-B co-doping, hence alleviating the Mn dissolution. So the Ni-B co-doping accompanied with truncated octahedron morphology presents the preferential growth of {111} and {100} planes. Among the various counterparts of Ni-B co-doping, the optimized LiMn1.84Ni0.10B0.06O4 exhibits the optimal rate performance and cycle life. At 5 C, a capacity retention of 73.5% with an initial discharge capacity of 101.8 mAh g−1 is achieved after ultra-long 2000 cycles. Even at 10 C, the capacity retention of 62.2% is also maintained after 2000 cycles. This combination of element doping and morphology regulation will provide a feasible strategy to synthesize high-performance spinel LiMn2O4 cathode materials for lithium-ion batteries.

Tuning Interphase Chemistry to Stabilize High-Voltage LiCoO2 Cathode Material via Spinel Coating.

Cathode electrolyte interphases (CEIs) are critical to the cycling stability of high-voltage cathodes for batteries, yet their formation mechanism and properties remain elusive. Here we report that the compositions of CEIs are largely controlled by abundant species in the inner Helmholtz layer (IHL) and can be tuned from material aspects. The IHL of LiCoO2 (LCO) was found to alter after charging, with a solvent-rich environment that results in fragile organic-rich CEIs. By passivated spinel Li4 Mn5 O12 coating, we achieve an anion-rich IHL after charging, thus enabling robust LiF-rich CEIs. In situ microscopy reveals that LiF-rich CEIs maintain mechanical integrity at 500 °C, in sharp contrast to organic-rich CEIs which undergo severe expansion and subsequent voids/cracks in the cathode. As a result, the spinel-coated LCO exhibits a high specific capacity of 194 mAh g-1 at 0.05 C and a capacity retention of 83 % after 300 cycles at 0.5 C. Our work sheds new light on modulating CEIs for advanced lithium-ion batteries.

Tuning Interphase Chemistry to Stabilize High‐Voltage LiCoO2Cathode Material via Spinel Coating

AbstractCathode electrolyte interphases (CEIs) are critical to the cycling stability of high‐voltage cathodes for batteries, yet their formation mechanism and properties remain elusive. Here we report that the compositions of CEIs are largely controlled by abundant species in the inner Helmholtz layer (IHL) and can be tuned from material aspects. The IHL of LiCoO2(LCO) was found to alter after charging, with a solvent‐rich environment that results in fragile organic‐rich CEIs. By passivated spinel Li4Mn5O12coating, we achieve an anion‐rich IHL after charging, thus enabling robust LiF‐rich CEIs. In situ microscopy reveals that LiF‐rich CEIs maintain mechanical integrity at 500 °C, in sharp contrast to organic‐rich CEIs which undergo severe expansion and subsequent voids/cracks in the cathode. As a result, the spinel‐coated LCO exhibits a high specific capacity of 194 mAh g−1at 0.05 C and a capacity retention of 83 % after 300 cycles at 0.5 C. Our work sheds new light on modulating CEIs for advanced lithium‐ion batteries.

Nanoscaled LiMn2O4 for Extended Cycling Stability in the 3 V Plateau.

Extending the potential window toward the 3 V plateau below the typically used range could boost the effective capacity of LiMn2O4 spinel cathodes. This usually leads to an “overdischarge” of the cathode, which can cause severe material damage due to manganese dissolution into the electrolyte and a critical volume expansion (induced by Jahn–Teller distortions). As those factors determine the stability and cycling lifetime for all-solid-state batteries, the operational window of LiMn2O4 is usually limited to 3.5–4.5 V versus Li/Li+ in common battery cells. However, it has been reported that nano-shaped particles and thin films can potentially mitigate these detrimental effects. We demonstrate here that porous LiMn2O4 thin-film cathodes with a certain level of off-stoichiometry show improved cycling stability for the extended cycling range of 2.0–4.5 V versus Li/Li+. We argue through operando spectroscopic ellipsometry that the origin of this stability lies in the surprisingly small volume change in the layer during lithiation.

(1-x) Li1-YNayM1-ZTizO2 x LiM2-ZTizO4 layered-Spinel Nanoparticles As Promising Dual Positive Electrode for Lithium-Ion Batteries and Sodium-Ion Batteries

The demand for high-capacity batteries is increasing rapidly with the upcoming energetic needs of an ever increasing population, especially in the transportation sector. Lithium-ion battery (LIB) has emerged as an attractive technology, however the main restriction is his low energy density1. To make a post-transition possible the sodium-ion battery (SIB) are among the most promising alternatives due sodium is abundant, there are enormous availability and It's low cost2. Besides, the electrochemical principles governing LIB and SIB batteries are quite similar3. Nevertheless, for both emerging alternatives it is necessary to find more suitable electrode materials. Therefore, nowadays, different electrode materials have been explored to increase the capacity of those batteries. Specially, the layered-spinel structure has been used to improve the initial specific capacity and stability electrode materials. The Na-layered structure cathode facilitates Li+-ion diffusion in the structure4. Besides the incorporation of Ti4+ in the LiMn2O4 spinel phase is performed with the purpose of improving its stability by averting the Jahn-Teller effect of the Mn3+ and decreasing Mn2+ dissolution towards the electrolyte during cycling since Ti-O provides a higher binding energy (662 kJ/mol) than for Mn-O (402 kJ/mol)1.The aim of this investigation is to estimate the optimal stoichiometry in the (1-x)Li1-yNayM1-zTizO2x LiM2-zTizO4 layered-spinel by varying the concentration of Na+ and to assess the effects of the cations addition in the cycling stability of the active material. A facile sol-gel method is presented to develop new composite materials for LIB and SIB. Cathode materials were characterized by XRD, Raman, SEM, VC, EIS and charge/discharge cycling tests.Analysis of XRD patterns confirmed the existence of a spinel-layered composite where the peaks can be indexed to the cubic spinel structure ( space group) and layered structure (C 12 - m1; R-3m and P 63-mmc space group)°5. For LIB cycling was performed typically between 4.8 and 2.0V vs. Li|Li+ at a constant current of 29.0 mAg-1, equivalent to 0.1 C-rate. The stoichiometry 0,5Li0.9Na0.1Mn0.4Ni0.5Ti0.1O2-0,5LiMn1.4Ni0.5Ti0.1O4 showed an initial specific capacity, ca. 141 mAhg-1 but later it presented increasing of the specific capacity, ca. 180 mAh g-1 at 15st cycling exhibiting 98% of its charge capacity after 30st cycles. Moreover, for SIB cycling was performed typically between 4.5 and 2.0V vs. Na|Na+ at a constant current of 10.0 mAg-1, equivalent to 0.1 C-rate. In this case, the stoichiometry 0,5Li0.5Na0.5Mn0.4Ni0.5Ti0.1O2-0,5LiMn1.4Ni0.5Ti0.1O4 showed an initial specific capacity, ca. 94 mAh g- 1.Thus, by possessing interesting properties electrochemical we believe that these materials could be a potential electrode for the development of high-power rechargeable Li-ion batteries and Na-ion batteries. References N. Mosquera, F. Bedoya-Lora, V. Vásquez, F. Vásquez, and J. Calderón, Journal of Applied Electrochemistry (2021) https://doi.org/10.1007/s10800-021-01582-w.R. Klee, P. Lavela, and J. L. Tirado, Electrochimica Acta, 375 (2021).S. Rubio et al., Journal of Solid State Electrochemistry, 24, 2565–2573 (2020).L. Zheng and M. N. Obrovac, Electrochimica Acta, 233, 284–291 (2017) https://www.sciencedirect.com/science/article/pii/S0013468617304978.S. U. Vu. N and H. V, Journal of Power Sources, 355, 134–139 (2017) http://dx.doi.org/10.1016/j.jpowsour.2017.04.055. Figure 1

Microwave irradiation suppresses the Jahn-Teller distortion in Spinel LiMn2O4 cathode material for lithium-ion batteries

Jahn-Teller (J-T) distortion remains the key challenge to realizing the full electrochemistry potential of the commercialized LiMn2O4 cathode material for lithium-ion batteries. In this work, the application of microwave irradiation to suppress the limiting J-T distortion in pristine LMO (LMO-p) materials and improve the electrochemistry of lithium-ion batteries has been reported. Unlike thermal heating, microwave irradiation inhibits J-T distortion. To establish the underlying science behind the impact of microwave irradiation, both the pristine (LMO-p) and the microwave-treated counterpart (LMO-m) are subjected to several characterization techniques, including synchrotron XRD, XPS, powder neutron diffraction (PND), MAS 7Li NMR, Raman and BET analysis. These techniques prove that LMO-m possesses the needed physico-chemical properties that explain: i) suppressed J-T distortion (such as an increased average Mn oxidation state (i.e., nMn ≥ 3.5+ or Mn4+/Mn3+ > 50%)), decreased lattice parameter, enhanced BET surface area, and enhanced structural crystallinity), and ii) improved electrochemical performance (such as increased specific discharge capacity, electronic and Li-ion transfer kinetics, and Coulombic efficiency). Microwave irradiation improves the specific capacity by about 21% and capacity retention (0.022% capacity loss per cycle for the LMO-m, ∼ 0.036% capacity loss per cycle for LMO-p for 100 cycles). The findings in this work are relevant for the realization of low-cost and environmentally benign scale-up modification processes for LMO spinel and related cathode materials for the development of high-performance lithium-ion batteries.

Hydrothermal synthesis of Mg-doped LiMn2O4 spinel cathode materials with high cycling performance for lithium-ion batteries

Hydrothermal synthesis of Mg-doped LiMn2O4 spinel cathode materials with high cycling performance for lithium-ion batteries

Mitigating the Jahn-Teller distortion driven by the spin-orbit coupling of lithium manganate cathode

Spinel LiMn2O4 is recognized as one of the most competitive cathode candidates for lithium-ion batteries ascribed to environmentally benign and rich sources. However, the wholesale application of LiMn2O4 is predominately plagued by its severe capacity degradation, mainly associated with the innate Jahn-Teller effect. Herein, single-crystalline LiMn2O4 with Eu3+ doping is rationally designed to mitigate the detrimental Jahn-Teller distortion by tuning the chemical environment of MnO6 octahedra and accommodating localized electron, based on the unique aspheric flexible 4f electron orbit of rare-earth metal ions. Notably, the stretching of MnO6 octahedron stemmed from the Jahn-Teller effect in Eu-doped LiMn2O4 is effectively suppressed, confirmed by theoretical calculation. Meanwhile, the structural stability of the material has been significantly enhanced due to the robust Mn–O band coherency and weakened phase transition, proved by synchrotron radiation absorption spectrum and operando X-ray diffraction. The corresponding active cathode manifests superior long-cycle stability after 300 loops at 2C and displays only a 0.011% capacity drop per cycle even at 5C. Given this, this modification tactic sheds new light on achieving superior long-cycle performances by suppressing distortion in various cathode materials.

Tailoring structure, nonlinear/linear optical, and dielectric properties of PVA/PVP film by spinel LiMn2O4 nanoparticles

LiMn2O4 (LMO) nanoparticles have received significant attention owing to their role in energy storage and power supply applications. Here, the facile low-temperature synthesis of new hybrid freestanding films incorporated with different LMO nanoparticle concentrations (0, 0.037, 0.37, and 3.7 wt.%) was preceded to tunable the optical and electrical properties of the PVA-PVP blend. The formation of the nanoparticles and polymeric nanocomposite (PNC) films was confirmed using various techniques, including HRTEM, SEM, FTIR, and XRD. The relationship between the optical and dielectric properties of the films with the bandgap was tuned using the doping ratio. Two models were used to estimate the precision of the optical transition bandgap. Our results revealed that the calculated extinction coefficient, Urbach energy, optical conductivity, and refractive index of PVA-PVP were enhanced. The nonlinear optical parameters, including the third-order susceptibility (χ(3)) and refractive index (n2), also improved with a reduction in the bandgap. In addition, a hybrid film with 3.7 wt.% LMO exhibited excellent optical shielding. However, the electrical properties of the PNC films are not only affected by the applied frequency but can also be tuned by the LMO ratio. The AC conductivity and dielectric constant of the hybrid/PNC films were enhanced by the addition of LMO, and the highest values were achieved for the semi-transparent PNC with 0.37 wt.% LMO. For the oblique film with 3.7 wt.% LMO, most nanoparticles cover the significant portions of the polymer surface, which decreases the electrical properties. The dominant mechanism in all PNC films is related to barrier hopping (CBH) and follows Jonscher's power (JP) performance. The investigated hybrid films are promising for environmental optoelectronics, photosensors, optical shielding, and Li+ ion-based battery devices.

Spinel LiMn2O4 integrated with coating and doping by Sn self-segregation

Spinel LiMn2O4 integrated with coating and doping by Sn self-segregation

Configurational entropy-induced phase transition in spinel LiMn2O4

The spinel-type LiMn2O4 is a promising candidate as cathode material for rechargeable Li-ion batteries due to its good thermal stability and safety. Experimentally, it is observed that in this compound there occur the structural phase transitions from cubic () to tetragonal (I41/amd) phase at slightly below room temperature. To understand the phase transition mechanism, we compare the Gibbs free energy between cubic phase and tetragonal phase by including the configurational entropy. Our results show that the configurational entropy contributes substantially to the stability of the cubic phase at room temperature due to the disordered Mn3+/Mn4+ distribution as well as the orientation of the Jahn–Teller elongation of the Mn3+O6 octahedron in the the spinel phase. Meanwhile, the phase transition temperature is predicted to be 267.8 K, which is comparable to the experimentally observed temperature. These results serve as a good complement to the experimental study, and are beneficial to the improving of the electrochemical performance of LiMn2O4 cathode.

Surface spinel and interface oxygen vacancies enhanced lithium-rich layered oxides with excellent electrochemical performances

Li-rich layered oxide (LLO) is one of the most promising cathode materials for high energy–density lithium ion battery (LIB) due to its capacity more than 250 mAh g−1. However, the low initial Coulombic efficiency, large voltage decay and poor cycling stability caused by irreversible lattice oxygen releasing hinder its further development. The present work demonstrates that a surface layer of spinel Li4Mn5O12 rich of interface oxygen vacancies in LLO (denote as SLLO) reduces the voltage decay and suppresses the irreversible release of oxygen. When SLLO was used as a cathode in LIBs, the initial Coulombic efficiency is improved from 83% to 97%, a high reversible capacity of 303 mAh g−1 at a rate of 0.1C, as well as a capacity retention of 88% at 0.3C at 200 cycles, and corresponding voltage decay is also mitigated. Characterization and calculation reveal that the enhanced performance is attributed to the rapid Li+ extraction/insertion in the surface spinel; the irreversible release of O2 is reduced through the interfacial oxygen vacancies; the adverse reaction is largely suppressed by spinel coating layer.

Beneficial impact of incorporating spinel lithium manganate and samarium oxide into high performance positive materials through ultrasonic cavitation strategy

Spinel LiMn2O4 (LMO) positive material has the advantage of a robust structure with a three-dimensional network of channels for fast Li+ conduction, which is one of the hot topics in the zero-cobalt electrodes field of new energy technology. Nonetheless, the spinel LiMn2O4 has serious transition metal dissolution as well as phase/surface stability problems, resulting in unsatisfactory cycle performance which hinders large scale applications in the field of lithium-ion batteries. In this study, Sm2O3 surface modified LiMn2O4 positive material is obtained by a facile ultrasonic cavitation combined with sol-gel strategy. The structural and surface morphological are analyses by X-ray diffraction, X-ray photoelectron spectroscopy and high resolution transmission electron microscopy illuminate the formation of the Sm2O3-coated LiMn2O4. Electrochemical analysis revealed that the LMO particles coated by the 1 wt% Sm2O3 is exhibited the best electrochemical performance among other coated and non-coated samples, with an initial capacity of 110.92 mAh g−1 and a capacity retention of 94.79% after 200 cycles. Furthermore, ICP analysis is showed that the manganese dissolution of the modified material in organic electrolyte is much lower than that of pristine sample. This work may provoke wide interests in surface modification areas and motivate the further improvement of the electrochemical performance for other commercialized spinel lithium ion batteries (LIBs).

Modification of LiMn2O4 surfaces by controlling the Acid–Base surface chemistry of atomic layer deposition

In this combined theoretical and experimental study, we report the effects of Al precursor selection on the growth chemistry, interfacial structure, and electrochemistry of Al2O3 coatings on spinel LiMn2O4 (LMO) surfaces by atomic layer deposition (ALD). Five Al precursors, exhibiting a range of Lewis acid–base properties, were used to establish trends in the ALD Al2O3 growth chemistry on LMO powders in comparison to redox-inactive planar silicon substrates. We show that the Lewis acid–base properties of the Al precursor ligands can be used to tune both the Mn oxidation states and the Al2O3 coverage on the LMO surface. Density functional theory calculations are used to examine the reaction mechanism of each precursor on LMO surfaces, elucidating a correlation between the Lewis acidity of the ligands and the decomposition thermochemistry. In-depth X-ray photoelectron spectroscopy and in situ Fourier transform infrared spectroscopy measurements support these theoretical predictions and further reveal how different Al precursors modify the atomic and electronic structure near the LMO surface during ALD. While the Mn oxidation state is strongly influenced by the Lewis acidity of the precursor ligand, the surface coverage and thickness of the Al2O3 coating are a more representative descriptor of the electrochemical performance measured in coin cell experiments. We show how the ligand acid–base properties of ALD precursors can be used to rationally tailor atomic layer growth mechanisms, which may enable atomic level control over the structure of functionalized interfaces for various applications related to catalysis, semiconductors, and energy storage.

Boosting the cycling performance of spinel LiMn2O4 by in situ MnBO3 coating

Spinel LiMn2O4 (LMO) is a promising cathode material for lithium-ion batteries (LIBs) due to its low cost, high safety, and high energy density. However, surface dissolution of manganese and irreversible phase transitions reduce its long-term cycling performance. Although surface coating is a promising strategy for improving the structural stability of LMO, the commonly used coating process is tedious and complicated. In this work, a one-step sintering process is developed to prepare LMO materials coated in situ with MnBO3. It is found that the MnBO3 layer formed in this way is uniformly coated on the surface of LMO, and effectively suppresses Mn dissolution and undesirable phase transition during repeated charge/discharge cycles. Furthermore, the MnBO3-coated LMO has improved electrode kinetics, demonstrating significantly improved rate performance compared to the pristine LMO. As a result, the optimized LMO sample exhibits 85.2% capacity retention after 1000 cycles at 1 C and still can deliver 96 mAh g−1, even at 5 C. This work proposes a facile and efficient coating strategy for improving the electrochemical performance of LMO as a cathode material for LIBs.