Spinel Lithium Manganate Research Articles

Long-acting electrochemical lithium-recovery from original brine using super-stable spinel lithium manganate oxide

with the unprecedented demand for raw lithium, the spinel LiMn2O4 has been widely studied for electrochemical Li-recovery from salt-lake brines, but its industrialization is hindered by the poor cyclability induced by manganese dissolution and Jahn-Teller distortion within octahedral structure. In this work, Cr-doped and carbon-coated LiMn2O4 (C-LMO-Cr) electrodes prepared via coprecipitation-calcination method are employed to improve cycling stability and lithium selectivity for electrochemical Li-recovery. The results confirm the C-LMO-Cr electrode exhibits super-high retention rate of 98.76 % and 95.70 % of the initial capacity (27 mg·g−1) after 300 and 500 cycles, respectively. The carbon buffering on the C-LMO-Cr surface effectively impedes the initial manganese dissolution with the enhanced charge transfer. Moreover, the structural evolution from Raman/XPS analysis and theoretical calculations confirms that the shrinking lattice of the carbon-buffering LMO-Cr enhances Li+ selectivity and Li+ migration. When assembled in a hybrid capacitive deionization (HCDI) device, the optimal C-LMO-Cr electrode displays high adsorption capacity of ∼21 mg·g−1, moderate energy consumption of 13 Wh·mol−1(Li+) with a remarkable increase in Mg/Li ratio from 1.67 to 158 in the original brine from Jiezechaka. Therefore, these results demonstrate a promising potential of C-LMO-Cr electrodes for long-acting electrochemical lithium-recovery from original brines.

Preparation and Properties of Spinel LiMn1.90 Ni0.05 Cu0.05 O4

Spinel LiMn2O4 and LiMn1.90Ni0.05 Cu0.05O4 cathode materials were synthesized by a simple solution combustion method. The structure, morphology and properties of the two samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), battery test system and electrochemical workstation. The results show that the two samples are spinel lithium manganate structure, which can be indexed as Fd3m space group. Ni Cu co doping effectively reduces the particle size and agglomeration, improves the crystallinity of the materials, and makes LiMn1.90Ni 0.05 Cu0.05O4 samples show good crystal structure stability and magnification properties. The capacity retention rates of 64.53%,79.52%and 69.47%were obtained after 1000 cycles at current densities of 1 C,5 C and 10 C,respectively, which were higher than 43.75%,55.74%and 44.38%of the corresponding undoped LiMn2O4 samples.

Boosting stability of spinel LiMn2O4 cathode materials by creating oxygen vacancies

Octahedral spinel lithium manganate dioxide (LiMn2O4, LMO) achieves remarkable electrochemical properties, but manganese dissolution during extended cycling process still cannot be well avoided. Herein, the oxygen vacancies within LiMn2O4 can be effectively modulated by extending the calcination duration. The density functional theory (DFT) calculation and experiments verified that appropriate oxygen vacancies not only promotes the structural stability, but also accelerates the charge transfer to improve the cycle performance under high C rate. Among them, the LMO sintered at 750 °C for 10 h (LMO-10) presented prominent electrochemical performance, delivering 114.58 mAh/g with the capacity retention rate of 95.90 % after 500 cycles at 5C, while the unmodified sample only exhibits 64.46 mAh/g with low retention of 63.75 %. This highly effective and facile approach to manipulate oxygen vacancies of spinel LiMn2O4 would facilitate to develop advanced cathode materials for lithium-ion batteries.

Ultrafast Non‐Equilibrium Phase Transition Induced Twin Boundaries of Spinel Lithium Manganate

AbstractDefect engineering is demonstrated to be an important factor in enhancing the electrochemical performance of lithium‐ion batteries by improving structural stability and ion diffusion. However, conventional synthetic methods have long and complicated processes, making it challenging to effectively and easily introduce defects into electrode materials. In this work, a high‐temperature shock technique (HTS) with an ultrafast heating and cooling process that can quickly introduce twin boundaries (TBs) into phase‐pure spinel LiMn2O4 in seconds is reported. Various ex situ techniques reveal the crystallization mechanism of LiMn2O4 during ultrafast synthesis. LiMn2O4 with TBs exhibits a higher rate performance than that obtained from the traditional method. Additionally, alien elements can be evenly incorporated into LiMn2O4 in seconds, resulting in excellent cycling performance. For instance, 2% Ni‐doped LiMn2O4 shows an initial capacity of 121 mAh g−1 and retention of 86.5% after 500 cycles at 1 C.

Surface Magnesium Substitution at Spinel Lithium Manganate 8a Tetrahedral Sites for Suppressed Manganese Dissolution and Enhanced Cycle Stability

Surface Magnesium Substitution at Spinel Lithium Manganate 8a Tetrahedral Sites for Suppressed Manganese Dissolution and Enhanced Cycle Stability

Lithium-Ion Conductivity Epitaxial Layer Contributing to the Structure and Cycling Stability of LiMn2O4 Cathodes

A critical challenge in the commercialization of spinel lithium manganate materials is the bulk structure damage and capacity degradation due to manganese dissolution during battery operation. Hence, Li3PO4 with good ionic conductivity was homogeneously deposited on the surface of spinel lithium manganate by the sol–gel method, aiming to improve the stability and cycling of the spinel structure by an epitaxial layer. The structural and electrochemical characterizations reveal that the presence of the Li3PO4 epitaxial coating prevents the direct contact of the cathode surface and electrolyte, thus enhancing the stability of the structure and reducing the extent of manganese dissolution. Further studies have shown that the contribution of the Li3PO4 layer promotes the diffusion coefficient of lithium ions, which increases from 7.89 × 10–12 to 4.43 × 10–11 cm2 s–1. Meanwhile, the Li3PO4 coating regulates the concentration of oxygen vacancies on the surface of the spinel, effectively reducing the transfer resistance and increasing the electronic conductivity to 3.50 × 10–5 cm–1. Specifically, the discharge specific capacity of the 1.0 wt % Li3PO4-modified electrode is still 115.4 mAh g–1 after 300 cycles, with the capacity retention increased to 90.8%. Even at a high rate of 10C, it still demonstrates excellent rate capability, with the discharge specific capacity more elevated than that of the unmodified material at about 40 mAh g–1. This strategy can simultaneously solve the interfacial instability and bulk structure degradation, thus improving the electrochemical performance of lithium manganate materials.

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).

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.

Building an artificial solid electrolyte interphase on spinel lithium manganate for high performance aqueous lithium-ion batteries.

Spinel lithium manganate (LiMn2O4) is a promising cathode for aqueous lithium-ion batteries (ALIBs). However, due to Mn dissolution and the Jahn-Teller effect it suffers from fast capacity fading, insufficient rate capability, and low overcharge resistance. Herein, a ∼2-3 nm artificial solid electrolyte interphase (SEI) layer (lithium polyacrylate, LiPAA) is constructed on the commercial LiMn2O4 (LiPAA@LiMn2O4). It is realized by an in situ polymerization hydrothermal reaction using an acrylic monomer. This artificial SEI layer can separate the electrode and aqueous electrolyte, thus suppressing Mn dissolution and the Jahn-Teller effect of LiMn2O4. Electrochemical analyses also suggest it may work as the Li+ conductor/reservoir to improve the Li+ diffusion coefficient of the electrode. Consequently, as the cathode of ALIBs, LiPAA@LiMn2O4 harvests a high capacity of 119 mA h g-1 at 0.6C, high rate capability (70 mA h g-1 at 12C), better durability (85.5%@100 cycles) and superior overcharge resistance.

Surface Stabilization of O3-type Layered Oxide Cathode to Protect the Anode of Sodium Ion Batteries for Superior Lifespan.

SummaryEven though the energy density of O3-type layer-structured metal oxide cathode can fully reach the requirement for large-scale energy storage systems, the cycling lifespan still cannot meet the demand for practical application once it is coupled with a non-sodium-metal anode in full-cell system. Transition metal dissolution into the electrolyte occurs along with continuous phase transformation and accelerates deterioration of the crystal structure, followed by migration and finally deposition on the anode to form a vicious circle. Surface engineering techniques are employed to modify the interface between active materials and the electrolyte by coating them with a thin layer of AlPO4 ion conductor. This stable thin layer can stabilize the surface crystal structure of the cathode material by avoiding element dissolution. Meanwhile, it can protect the anode from increased resistance by suppressing the dissolution-migration-deposition process. This technique is a promising method to improve the lifetime for the future commercialization.

Cr3+ and F− co-doped lithium manganese oxide cathode for medium-temperature reserve primary cell

Medium-temperature molten salt reserve primary cell utilizes low-melting nitrate electrolyte, that is considered suitable for geothermal borehole as well as oil and gas exploration. In this work, Cr3+ and F− ions were introduced into spinel lithium manganate oxides by high-temperature solid-state method and verified by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The effects of fluorine content on the morphology and discharge performance of the LiCr0.1Mn1.9O4−xFx (0 ≤ x ≤ 0.5) have been studied in LiCr0.1Mn1.9O4−xFx/LiNO3-KNO3-Ca(NO3)2/Li-Mg-B system. Fluoride-doped samples have a significant improvement in discharge performance at the condition of 10 mA·cm−2 and 250 °C because of the stabilization of the crystal structure. Factors of operating temperature and current density have a significant effect on battery discharge performance, and the surroundings of 10 mA·cm−2 and 200–250 °C contributes the battery to achieve high performance. That indicates the LiCr0.1Mn1.9O4−xFx/LiNO3-KNO3-Ca(NO3)2/Li-Mg-B battery shows great potential in geothermal borehole as well as oil and gas exploration environment.

Synthesis of single-crystal magnesium-doped spinel lithium manganate and its applications for lithium-ion batteries

Single-crystal magnesium-doped spinel lithium manganate cathode materials are prepared by the hydrothermal method followed by the heat treatment. XRD patterns reveal that Mg2+ions have already diffused into the Li1.088Mn1.912O4 crystal structure and not affect the Fd3m space group. SEM images demonstrate that the magnesium-doped spinel lithium manganates show uniform polyhedral single crystals with 2–4 μm. Electrochemical performance demonstrates that the optimized composition of Li1.088Mg0.070Mn1.842O4 electrode exhibits the best electrochemical properties. It delivers 92.0 mAh g−1 at 8C rates and corresponds to 90.8% capacity retention (vs. 1C), far higher than those of the pristine electrode (70.4 mAh g−1 and 69.2%). In addition, the Li1.088Mg0.070Mn1.842O4 electrode also shows 95.5% capacity retention after 100 cycles at 1C, while the pristine electrode only shows 91.0% capacity retention. The excellent electrochemical performances of Li1.088Mg0.070Mn1.842O4 electrode are ascribed to the suppressed polarization, more stable crystal structure, and better kinetic characteristics.

Engineering Surface Vacancy to Stabilize High-Voltage Battery Cathodes

In this issue of Chem, Cao and co-workers report a stabilization strategy for high-voltage lithium-ion battery cathodes down to the atomic scale. Using LiNi0.5Mn1.5O4 as a model, the authors demonstrated a protocol for precisely modulating the interstitial lattice sites on the material surface, showing the promising capability to improve electrochemical cyclability.

Role of Disproportionation in the Dissolution of Mn from Lithium Manganate Spinel

Dissolution of Mn from lithium manganate spinel has hindered its commercialization as a cathode material in Li-ion batteries. This dissolution has been widely attributed to disproportionation of near-surface Mn(III), in the presence of acid, with the resultant divalent Mn being vulnerable to dissolution. To what extent moisture in the cell (as opposed to the organic electrolyte) acts as the solvent for Mn ions has not been established. Simulations by Leung show that a small displacement of trivalent Mn from its equilibrium site at an LiMn2O4(001)/ethylene carbonate interface leads to its reduction to Mn(II). In the present work, thermodynamic integration is performed based on first-principles molecular dynamics simulations within the Blue-Moon ensemble to investigate the detachment of Mn ions at the LiMn2O4(001)/water interface. The results show that reduction of Mn(III) to Mn(II) occurs also in the case of an aqueous interface. The simulations were performed for both neutral and acidic water (in the pres...

On the Oxidation State of Manganese Ions in Li-Ion Battery Electrolyte Solutions.

We demonstrate herein that Mn3+ and not Mn2+, as commonly accepted, is the dominant dissolved manganese cation in LiPF6-based electrolyte solutions of Li-ion batteries with lithium manganate spinel positive and graphite negative electrodes chemistry. The Mn3+ fractions in solution, derived from a combined analysis of electron paramagnetic resonance and inductively coupled plasma spectroscopy data, are ∼80% for either fully discharged (3.0 V hold) or fully charged (4.2 V hold) cells, and ∼60% for galvanostatically cycled cells. These findings agree with the average oxidation state of dissolved Mn ions determined from X-ray absorption near-edge spectroscopy data, as verified through a speciation diagram analysis. We also show that the fractions of Mn3+ in the aprotic nonaqueous electrolyte solution are constant over the duration of our experiments and that disproportionation of Mn3+ occurs at a very slow rate.

Reducing the High Temperature Performance Degradation in Li-Ion Batteries By Using Ion-Trapping Separators

Manganese dissolution is the root-cause for a main degradation mode in Li-ion batteries with Mn-based active materials in their positive electrodes. Manganese cations dissolved from the positive electrode migrate through the electrolyte solution and deposit on the negative electrode, leading to reductions in both power performance and useful life. [1-4] Several methods were proposed over the years for mitigating the manganese dissolution or its consequences, such as elemental substitutions in positive electrode active material, surface coatings, inorganic barrier coatings by atomic layer deposition, passivating electrolyte solution additives, [5, 6] but none proved completely successfully so far. A different and complementary approach is that of using a separator containing manganese ion chelating agents, to trap the manganese ions in the inter-electrode space and prevent their migration to and deposition at the negative electrode. We showed in previous work that polymers functionalized by macrocycles (crown ethers) can both prevent manganese deposition on graphite negative electrodes and improve the capacity retention of lithium manganate spinel (LMO) - graphite cells during high-temperature (50 ºC) cycling. [7, 8] In the present work we show that the concept of Mn trapping separators has a wider applicability, beyond the class of macrocycles, i.e., that it can be extended to chelating agents with an open chemical structure, as exemplified by iminodiacetic acid disodium salt functional groups attached to styrene divinylbenzene polymeric particles (poly-IDANa2, for short). We demonstrate that separators functionalized with poly-IDANa2 perform as well as polymeric azacrowns with respect to the ability to chelate Mn ions and lead to similar improvements in the capacity retention of LMO-graphite cells during cycling at ambient and at elevated temperatures. The Mn cation trapping separators were fabricated in-house. A mixture of commercial poly-IDA resin and PVdF-HFP was either fabricated into poly-IADNa2 filled separator or coated onto a commercial separator by means of a phase-inversion method. We determined and compared the physical properties (surface and cross-section morphologies, electrolyte uptake, porosity, ionic conductivity, and electrochemical stability) of the Mn trapping separators with those of a plain commercial separator. Poly-IDANa2 filled separators had a McMullin Number (or conductivity derating divisor) of 2.7 at an overall porosity of 40%, compared with a McMullin Number of 8 - 12 for commercial polyolefin separators with the same porosity. Linear sweep voltammograms with cells containing poly-IDANa2 filled separators show onset of oxidative degradation near 5 V vs. Li/Li+; demonstrating that the electrochemical stability of these separators matches the stability limit of the 1M LiPF6/EC:DMC (1:1) electrolyte. Hence such filled separator should be suitable for use in present day commercial lithium-ion batteries and also enable improved low temperature power performance. Cycling tests showed that LMO-graphite cells containing poly-IDANa2 filled separators display improved capacity retention over LMO-graphite cells containing commercial polyolefin separators. After 100 constant current cycles at C/5 rate, cells with poly-IDANa2 filled separators displayed (a) smaller increases in interfacial film and charge transfer resistances (by factors of 1.5 to 2.3 at 30 ºC and of 1.9 to 4.4 at 55 ºC, compared, respectively, with factors of 2.2 - 4.4 and 2.8 - 11.8 for cells with commercial polyolefin separators); (b) significantly reduced Mn poisoning of graphite electrodes (Mn amounts on the graphite electrodes from pouch cells with poly-IDANa2 filled separators were 8.3x and 5.5x smaller than Mn amounts on graphite electrodes from cells with commercial polyolefin separators, at 30 ºC and 55 ºC, respectively); and (c) significantly increased cycle life for LMO-graphite cells (cells with poly-IDANa2 separators retained 20% and 55% more capacity than cells with commercial polyolefin separators at 30 and 55 °C, respectively).

Dissolution Based Analysis of Capacity Fade in Manganese Oxide Spinel Cathode

Due to higher gravimetric and volumetric energy density than other battery technologies, Lithium-ion batteries (LIBs) have assumed an important role as portable energy systems to power electronic devices such as mobiles and laptops. However, implementation of LIBs to power automotive vehicles are limited due to their high cost, low cycle life and capacity loss at high discharge rates. For successful commercialization of electric- (EVs) and hybrid-electric (HEVs) vehicles, battery technology in terms of novel electrode materials, electrolytes and fabrication techniques needs to be further developed so that it is able to deliver better discharge capacity with improved capacity retention and cycle life. LiMn2O4 (LMO) has been used as a promising cathode material in battery systems to power EVs and HEVs due to its abundance, low cost, environmentally benign nature, minimum safety and thermal runaway issues1-3. Along with these exceptional advantages, LMO suffers from poor rate capability and cycling stability due to the imperative manganese (Mn2+) dissolution through disproportionation reaction (2Mn3+=Mn2++Mn4+), structural changes and electrolyte decomposition which act as hindrance to high power applications4-5. Research has been directed towards elucidating novel avenues to improve the cycling performance of LMO cathode for better capacity retention through investigating its electrochemical performance experimentally as well numerically3-7. However, a comprehensive numerical analysis that imitates experimental measurements towards an improved understanding of LMO degradation is missing in the literature. Consequently, galvanostatic charge/discharge, cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), galvanostatic intermittent titration technique (GITT) and potentiostatic intermittent titration technique (PITT) has been employed in this work to quantify the performance of LMO half-cell (against Li foil anode). This experimental data has been used as an input to the numerical model to explain the phenomenon of degradation caused by manganese dissolution. Figure 1 (a) shows the experimentally and numerically obtained capacity derived from cycling two 2016 LMO coin cells at 1C rate for the first 100 cycles. The experimental and simulated results are in good agreement which indicates that capacity decreases gradually as cycle number increases. This loss in capacity, which we regard as having been caused by Mn2+ dissolution in electrolyte, induces a reduction in volume fraction of solid matrix of LMO cathode. Figure 1 (b) shows the variation of cell potential with discharge capacity for the 1st and 100th cycles, which also indicates 16.5% loss in discharge capacity due to reduction in volume fraction of solid matrix. Through this study, the rate of dissolution and loss in cyclic lithium with cycling can be quantified, and could be applied to develop novel methods of synthesis of LMO for better cycling performance and capacity retention. References M. Rashid and A. Gupta, “Mathematical model for combined effect of SEI formation and gas evolution in li-ion batteries”, ECS Electrochem. Lett., 3, A95 (2014).M. Rashid, A. Gupta, “Effect of relaxation periods over cycling performance of a li-ion battery”, J. Electrochem. Soc., 162, A3145 (2015).H. Wang, F. Lai, Y. Li, X. Zhang, and Y. Huang, “Excellent stability of spinel LiMn2O4 based cathode materials for lithium-ion batteries”, Electrochim. Acta, 177, 290 (2015).L. Cai, Y. Dai, M. Nicholson, R. E. White, K. Jagannathan, and G. Bhatia, “Life modeling of a lithium ion cell with a spinel-based cathode”, J. Power Sources, 221, 191 (2012).J. Park, J. H. Seo, G. Plett, W. Lu and A. M. Sastry, “Numerical simulation of the effect of the dissolution of LiMn2O4 particles on li-ion battery performance”, Electrochem. Solid State Lett., 14, A14 (2011).C.-H. Lu and S.-W. Lin, “Dissolution kinetics of spinel lithium manganate and its relation to capacity fading in lithium ion batteries”, J. Mat. Res., 17, 1476 (2002).Z. Zhang, T. Zeng, Y. Lai, M. Jia, and J. Li, “A comparative study of different binders and their effects on electrochemical properties of LiMn2O4 cathode in lithium ion batteries”, J. Power Sources, 247, 1 (2014). Figure 1

Improving Stability of Li-Ion Batteries by Means of Transition Metal Ions Trapping Separators

Transition metal ions dissolution from positive electrodes initiates a well-known degradation mechanism in Li-ion cells, which limits their operational life. Preventing its consequences should be considered as a breakthrough in the field. We show herein that trapping Mn ions by ion-chelating polymers placed in the inter-electrode space of cells with lithium manganate spinel and Li or graphite electrodes, and greatly improves their high temperature cycling performance. Mn cations trapping separators were fabricated in-house using a commercial resin consisting of iminodiacetic acid disodium salt functional groups on a styrene divinylbenzene polymeric matrix, either by their inclusion into a separator through a phase-inversion method or by coating onto a plain commercial separator. We determined and compared the surface and cross-section morphologies, electrolyte-uptake, porosity, ionic-conductivity, and electrochemical-stability of these separators with those of a baseline separator. LMO-Li cells containing phase-inversion separators had ∼15x less Mn on the Li-electrode than cells with the baseline separator, after 100 cycles at 55°C. LMO-graphite cells with phase-inversion separators had ∼6x less Mn on the graphite-electrode, after 100 cycles at 55°C than cells with the baseline-separator. Capacity losses after cycling at 55°C were 30% and 55%, respectively, for the cells with phase-inversion and baseline separators.

Synthesis of highly crystalline LiMn2O4/multiwalled carbon nanotube composite material with high performance as lithium-ion battery cathode via an improved two-step approach

Facile synthesis of highly crystalline spinel-type LiMn2O4/multiwalled carbon nanotube (MWCNT) composite by a novel two-step approach is achieved. This approach involves an acetone-assisted hydrothermal reaction in LiOH solution using previously prepared birnessite MnO2/MWCNT composite as a manganese containing precursor. The lithium manganate spinel Li0.81Mn2O4/MWCNT composite delivers a high specific capacity of 145.4mAhg−1 at 0.1C-rate, which is close to the theoretic capacity of LiMn2O4 (148mAhg−1). Besides, it exhibits excellent high-rate capability and cyclability. For example, a discharge capacity of 114.8mAhg−1 is retained even at a high charge/discharge current rate of 20C. When it is repeatedly cycled at 1C rate for 1000 cycles, the specific capacity is decreased from the initial value of 140.4mAhg−1 to an end value of 98.7mAhg−1, giving 70.3% capacity retention.

Molecular dynamics simulations of spinels: LiMn2O4 and Li4Mn5O12 at high temperatures

Energy storage technologies are critical in addressing the global challenge of clean sustainable energy. Spinel lithium manganates have attracted attention due to their electrochemical properties and also as promising cathode materials for lithium-ion batteries. The current study focused on the effects of high temperatures on the materials, in order to understand the sustainability in cases where the battery heats up to high temperature and analysis of lithium diffusion aids in terms of intercalation host compatibility. It is also essential to understand the high temperature behaviour and lithium ion host capability of these materials in order to perform the armorphization and recrystalization of spinel nano-architectures. Molecular dynamics simulations carried out to predict high temperature behaviour of the spinel systems. The NVE ensemble was employed, in the range 300 - 3000K. The melting temperature, lithium-ion diffusion and structural behaviour were monitored in both supercell systems. LiMn2O4 indicated a diffusion rate that increased rapidly above 1500K, just before melting (∼1700K) and reached its maximum diffusion at 2.756 × 10-7 cm2s-1 before it decreased. Li4Mn5O12 indicated an exponential increase above 700K reaching 8.303 × 10−7 cm2s−1 at 2000K and allowing lithium intercalation even above its melting point of around 1300K. This indicated better structural stability of Li4Mn5O12 and capability to host lithium ions at very high temperatures (up to 3000 K) compared to LiMn2O4.