Lithium Manganese Oxide Research Articles

Stabilized Lithium, Manganese AB2O4 Spinel for Rechargeable Lithium Electrochemical Systems through A and B Site Doping

Lithium manganese spinel (LixMn2O4) has been extensively investigated as a safe and affordable lithium ion cathode material that can provide a great lattice for lithium intercalation. However, a major obstacle when utilizing LixMn2O4 cathodes is the loss of cycle capacity that occurs during cell charge and discharge. Lithium manganese oxide doped with potassium and cobalt produces a promising cathode material for rechargeable lithium-ion cells. Modifying the A site and B site of the spinel structure works to limit cathodic capacity fading by enhancing the robustness of the material. Successfully preventing degradation of the spinel matrix is key to maintaining the electrochemistry’s reversibility over prolonged cycling and abusive conditions. LixKyMn2-zCozO4 was prepared by modifying a stabilized lithium manganese-based AB2O4 spinel material with potassium A site and cobalt B site dopants. This was done using a two-step method where a manganese mixed metal oxide precursor was synthesized and subsequently used in a solid state reaction. LixKyMn2-zCozO4 was synthesized as the active ingredient for the cathode with x=1, y=0.1, and both z=0.1 and 0.2, and was tested against metallic lithium to evaluate performance. In order to assess the robustness of the LixKyMn2-zCozO4 cathode material at both z=0.1 and z=0.2, a number of cycling tests were run and analyzed in comparison to each cell’s baseline performance. A 2 mA cycling test between 3.0 or 2.5 V and 4.5 V was run initially on all cells to establish baseline performance, and was run between high rate discharge tests, pulse cycling tests, and deep discharge tests in order to compare to the cell’s baseline. Different groups of cells were discharged at 2, 4, 8, 12, 16, and 20 mA, pulse charged and discharged for 1 second with a 1 second rest, and deep discharged down to 2.5 V in order to assess the reversibility of the LixKyMn2-zCozO4 cathode chemistry when compared back to baseline performance. Through high-rate discharge, pulse cycling, and deep discharge tests, the electrochemistry of the cathode exhibited excellent reversibility and overall performance stability. For example, Figure 1 shows a Li \\ LiK0.1Mn1.8Co0.2O4 cell that retains its full capacity when tested at the 2 mA cycling baseline after high discharge rates of 4, 12, 16, and 20 mA for 10 cycles at a time. Figure2 illustrates the maintenance of the base thermodynamics of the same cell after these high-rate discharges, exhibiting the stability of the LiK0.1Mn1.8Co0.2O4 chemistry. An Li \\ LiK0.1Mn1.8Co0.2O4 cell was additionally shown to withstand a deep discharge test down to 2.5 V in Figure 3, and a pulse cycling test in Figure 4. Following each abusive test, the cell’s capacity returned to its previous value when cycled at baseline conditions, showing the stabilizing effect of the spinel’s modifications on capacity retention. Doping the LiMn2O4 spinel with potassium in the A site and cobalt in the B site proved to be a promising chemistry to prevent cathodic capacity fading in a lithium-ion cell, as well as a capable abuse tolerant option for use in rechargeable battery applications. Figure 1

Electrochemical Performance of LixMn2-YFeyO4-ZClz Synthesized through in Situ Glycine Nitrate Combustion

Background: Lithium manganese oxide spinel is a potential candidate for lithium-ion battery cathodes due to its 3D network of lithium pathways within the structure, low toxicity, reasonable capacity, and low cost. However, this spinel suffers from capacity fading due to fracturing of the structure either through the Jahn-Teller distortion, alternative phase formation via non-stoichiometry, or loss of crystallinity. Historically, cycle life enhancements have been achieved through stabilization of the spinel structure via transition metal doping on the B-site of the lattice. Iron as a dopant is of interest due partly to its low toxicity but primarily its low cost. By adding the redox couple of this transition metal, this spinel can satisfy higher voltage (5.0 V) applications should compatible electrolytes be produced. While B-site doping has proven effective, this effort proposes to observe if cycle life can be even further enhanced in LixMn2-yFeyO4 (LMFO) by also substituting anion dopants. Previously our group has incorporated chlorine and fluorine into the base LiMn2O4 material using solid state processing methods and demonstrated cyclability to 32 cycles as a result of weakening the Li-O bond for easier extraction from the lattice. Others have also added chlorine and more commonly fluorine and demonstrated performance enhancements. However rather than incorporating the halide into the lattice, most studies focus on surface modification of the spinel. The present study intends to look more into the cycle life benefits of the less-studied chlorine incorporation into the bulk of an iron-doped spinel via in situ combustion synthesis of the material. Experimental: A glycine nitrate combustion method was used to synthesize iron doped chlorinated lithium manganese oxide spinel (LMFO-Cl). Stoichiometric amounts of Li(NO­3­), Mn(NO­3)2∙4H2O, FeCl3, and NH2CH2COOH (glycine, Alfa Aesar) in a 1:1 metal to glycine ratio were dissolved into the aqueous solution. The solution was heated to evaporate the water and form a gel, which was heated further to 250 °C when auto ignition occurs. The resultant ash was fired at 600 °C for two to six hours to achieve the desired phase. Material characterization was performed using X-ray diffraction, X-ray fluorescence, BET surface area analysis, thermogravimetric analysis, and scanning electron microscopy. Cathode materials were mixed with carbon black and Teflon in a ratio of 85:10:5 of active to carbon to Teflon binder and calendared to 0.04 cm, punched into disks and pressed onto aluminum mesh opposite a Li metal anode. 2025 button cells were filled with 1 molar LiPF6 in a proportional mixture of diethyl carbonate, dimethyl carbonate, and ethylene carbonate. Electrochemical characterization was performed using electrochemical impedance spectroscopy (Solartron 1260) and cycling on an ARBIN MSTAT4 battery cycler system. Results and Conclusion: A nanoscale LixMn2-yFeyO4-zClz material was synthesized in three different compositions of y and z and desirable phase and morphological properties were achieved. The x-ray diffraction pattern indicated no presence of impurities while the x-ray fluorescence showed maintenance of the chlorine within the material after calcination. BET surface area analysis determined the surface area to be 8.48 m2/g with a highly desirable large pore size for ion transfer (14nm). The material was demonstrated to repeatedly achieve minimal capacity loss with short term cycling in all compositions and yielded 98% of the original discharge capacity at the 250th cycle for the case where y = 0.195 and z = 0.028. Figure 1 shows the cycling behavior out to 250 cycles demonstrating the capacity retention of this composition, LixMn1.805Fe0.195O3.972Cl0.028. Discharging below the 4.1 V plateau to 2.25 V did not immediately impact the cells as the reaction was reversible for all three compositions synthesized in this study. The primary limitations for these experimental cells were the inadequacy of the electrolyte preventing access to the higher voltage plateau at 5.0 V where more capacity could be achieved. Differential capacity curves across the 300 cycles (not shown here) demonstrate typical electrolyte degradation behavior. However the cathode chemistry appears to withstand advanced cycling and further work with electrolyte improvements could emphasize the extent of its performance capabilities. Figure 1

Chemical composition and formation mechanisms in the cathode-electrolyte interface layer of lithium manganese oxide batteries from reactive force field (ReaxFF) based molecular dynamics

Lithium manganese oxide (LiMn2O4) is a principal cathode material for high power and high energy density electrochemical storage on account of its low cost, non-toxicity, and ease of preparation relative to other cathode materials. However, there are well-documented problems with capacity fade of lithium ion batteries containing LiMn2O4. Experimental observations indicate that the manganese content of the electrolyte increases as an electrochemical cell containing LiMn2O4 ages, suggesting that active material loss by dissolution of divalent manganese from the LiMn2O4 surface is the primary reason for reduced cell life in LiMn2O4 batteries. To improve the retention of manganese in the active material, it is key to understand the reactions that occur at the cathode surface. Although a thin layer of electrolyte decomposition products is known to form at the cathode surface, the speciation and reaction mechanisms of Mn2+ in this interface layer are not yet well understood. To bridge this knowledge gap, reactive force field (ReaxFF) based molecular dynamics was applied to investigate the reactions occurring at the LiMn2O4 cathode surface and the mechanisms that lead to manganese dissolution. The ReaxFFMD simulations reveal that the cathode-electrolyte interface layer is composed of oxidation products of electrolyte solvent molecules including aldehydes, esters, alcohols, polycarbonates, and organic radicals. The oxidation reaction pathways for the electrolyte solvent molecules involve the formation of surface hydroxyl species that react with exposed manganese atoms on the cathode surface. The presence of hydrogen fluoride (HF) induces formation of inorganic metal fluorides and surface hydroxyl species. Reaction products predicted by ReaxFF-based MD are in agreement with experimentally identified cathode-electrolyte interface compounds. An overall cathode-electrolyte interface reaction scheme is proposed based on the molecular simulation results.

Synthesis, Characterization and Performance Evaluation of Lithium Manganese Oxide for Lithium Adsorption

Synthesis, Characterization and Performance Evaluation of Lithium Manganese Oxide for Lithium Adsorption

One-pot synthesis of aluminum oxide coating and aluminum doping on lithium manganese oxide nanoparticles for high performance energy storage system

In the present study, in order to demonstrate the one-pot synthesis of aluminum oxide (Al2O3) coating and aluminum doping, we synthesized aluminum oxide (Al2O3)-coated LiAlxMn2-xO4 (LAMO) NPs using a sequential process of the as-spun nanofiber templates, chemical precipitation, and calcination as a cathode material in lithium ion batteries (LIBs). To find the optimum condition of Al2O3 coating layer and Al doping, we performed the simple calcination methods at 300 °C using the Al(OH)2-coated LMO NPs. The resultant Al2O3-coated LAMO NPs exhibited the highest capacity of 111.1 mAh g−1 with the capacity retention of 94.4% after 90 cycles at 1 C, excellent rate performance, and the highest high-rate capacity of 81.4 mAh g−1 at 10 C as compared to bare LMO NPs without Al2O3 coating and Al(OH)2-coated LMO NPs without calcination. The improved electrochemical performance can be defined by the co-effect of Al2O3 coating and Al doping on bare LMO NPs. The former is related to cycle stability that increased due to the prevention of volume expansion and Mn dissolution as a physical buffer layer. The latter is related to high-rate performance improved due to the enhanced bonding energy of AlO bond. Therefore, it can be concluded that Al2O3-coated LAMO NPs are promising candidate cathode materials for high-performance LIBs.

Preparation of Chemical Manganese Dioxide by Dilute Sulphuric Acid Pickling of Mn3O4 and Its Application to the Synthesis of LiMn2O4

AbstractChemical manganese dioxide (CMD) was obtained by pickling Mn3O4 with dilute sulfuric acid. Atomic absorption spectroscopy (AAS) showed that S, Na, Ca and Mg impurities in CMD were less than in electrolytic manganese dioxide (EMD). Spinel lithium manganese oxide (LiMn2O4) samples were synthesized using CMD or EMD precursor mixed with Li2CO3 via high temperature solid‐phase reactions. The oxides were applied as the cathode material for lithium ion batteries. X‐ray diffraction (XRD) and scanning electron microscopy (SEM) showed that the crystallinity was high and the size‐distribution was uniform for CMD. The crystallinity of the spinel‐type LiMn2O4 synthesized by the CMD was high as well. Electrochemical tests showed that LiMn2O4 synthesized by the CMD precursor exhibited greater discharge capacity and better rate capability than the sample synthesized by the EMD precursor. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) indicated that LiMn2O4 synthesized by CMD or EMD precursor both showed good kinetics for Li+ ion transport, but LiMn2O4 synthesized by the CMD precursor showed a lower electrochemical impedance. Meanwhile, the synthesis process was simple, cheap, and easy for large‐scale production.

Modeling of a Permanent Magnet Synchronous Motor of an E-Scooter for Simulation with Battery Aging Model

For the growing market of electric two-wheelers (e-scooters) especially in China, the paper presents an implementation of a time efficient powertrain model. The model consists of an electric motor, power electronics and a Li-ion battery with aging prediction. Depending on the intended use of the models, two different accuracy levels requiring different computational power and computation time are introduced. As motor model a Permanent Magnet Synchronous Motor design is used. An empirical aging model for a Lithium Manganese Oxide cell is presented, which is based on aging measurements. Together, the models provide a possibility to evaluate the long-term cell aging behavior under realistic drive cycles taking motor effects into account.

Reduced-Order Electrochemical Model-Based SOC Observer With Output Model Uncertainty Estimation

As an integral part of energy storage systems, Li-ion batteries require extensive management to guarantee their safe and efficient operation. Estimation of the remaining energy capability of the battery, usually expressed in terms of state of charge (SOC), plays an important role in any battery-powered application. Electrochemical model-based estimation techniques have proven very attractive for this purpose due to the additional information they provide regarding the internal battery operating conditions. A modified reduced-order model based on the single particle approximation of the electrochemical model, suitable for the real-time implementation of SOC estimation, is employed in this paper. This model, while maintaining some of the physical insights about the battery operation, provides a basis for an output-injection observer design to estimate the SOC. Output model uncertainties, originating primarily from the electrolyte-phase potential difference approximation and encountered mainly at higher discharge rates, are handled by incorporating an adaptation algorithm in the observer. Therefore, the proposed method, while being suitable for online implementation, provides an electrochemical model-based solution for battery SOC estimation over a wide range of operations. System stability and the robustness of the estimates given measurement noise are proved analytically using Lyapunov stability. Finally, accurate performance of the proposed SOC estimation technique is illustrated using simulation data obtained from a full-order electrochemical model of a lithium manganese oxide battery.

Mechanochemical synthesis of silica-lithium manganese oxide composite for the efficient recovery of lithium ions from seawater

In this study, to prevent manganese dissolution from an acid treatment during the extraction of lithium ions (Li+), silica (SiO2) was mixed mechanically with lithium manganese oxide (Li1.33Mn1.67O4, LMO) by a high-energy milling technique followed by calcination. The milling process ensured high-level chemical homogeneity of metal oxides. The amorphous SiO2 imparted stability to the LMO spinel structure and reduced the level of Mn dissolution during the extraction of Li+ using an acid. X-ray diffraction and thermogravimetric analysis confirmed that the amorphous SiO2 was well mixed in the framework of LMO. The Li-Si-Mn-O composite was used as an efficient adsorbent for the recovery of Li+ from lithium spiked seawater with an adsorption capacity of 43.23mgg−1. The adsorption process fitted the Langmuir isotherm well with a correlation coefficient of 0.9831. The kinetic study showed that the adsorption behavior followed pseudo-second-order kinetics. The adsorbent exhibited excellent selectivity towards Li+, even in the presence of competitive cations with a higher concentration than Li+.

Interatomic Potential of Li–Mn–O and Molecular Dynamics Simulations on Li Diffusion in Spinel Li1–xMn2O4

An interatomic potential of the Li–Mn–O ternary system has been developed on the basis of the second-nearest-neighbor modified embedded-atom method (2NN MEAM) formalism combined with a charge equilibration (Qeq) concept. The potential reproduces fundamental physical properties (structural, elastic, thermodynamic and migration properties) of various compounds well, including lithium oxides, manganese oxides, and lithium manganese ternary oxides. Through molecular dynamics (MD) simulations using the developed potential, lithium diffusion properties (activation energy for lithium migration and diffusion coefficient) in spinel Li1–xMn2O4 are also reproduced in good agreement with experiments. We have found that the effect of the lithium vacancy concentration is marginal on the activation energy for lithium diffusion in the Li1–xMn2O4 cathode, but it is significant in the lithium diffusion coefficient. The potential can be further utilized for atomistic simulations of various materials phenomena (phase transit...

Surface-initiated fluoride-scavenging polymeric layer on cathode materials for lithium-ion batteries

Abstract Spinel-structured lithium manganese oxides (LMOs) suffer from manganese dissolution at elevated temperatures, which leads to severe capacity fading. In this work, a novel strategic approach was developed to alleviate this phenomenon by using poly(dimethylsiloxane) (PDMS) as a simple and scalable electrode additive. LMO electrodes containing finely dispersed PDMS were prepared using a conventional electrode coating process. Electrochemical studies showed that the PDMS-dispersed LMO electrodes had significantly improved cycling retentions. Ex-situ FT-IR and 19 F NMR spectra indicated PDMS chemically scavenged the F − species, which cause manganese dissolution in LMO-based cells. In addition, a plausible mechanism was proposed based on the spectroscopic evidences.

(Invited) Unified Band Diagram Framework for the Development of Cation Intercalation Materials for Next Generation Batteries

Next generation batteries may shift from lithium ion chemistries to those based on more earth-abundant cations such as sodium, potassium, or magnesium ions and employ ionic liquid or solid electrolytes with stability windows of over 6 volts. We have developed a new theoretical approaches to analyze lithium ion battery cathode materials to gain insight into the requisite properties for electrode materials in next-generation batteries, which we demonstrate using spinel lithium manganese oxide (LiMn2O4). Nanoscale spinel LiMn2O4 is a potential high-rate cathode material for advanced battery technologies and other electrochemical applications. Using a coupled electrochemical and band structure analysis of LiMn2O4 informed by screened hybrid density functional theory calculations we identify new features of the charge storage properties and stability of LiMn2O4. The accuracy and predictive power of this theoretical framework to determine the equilibrium potential(s) for charge-transfer in intercalated compounds is validated by comparison with experimental results. We first demonstrate the synthesis of ultrathin films of spinel LiMn2O4 between 20 and 200 nm in thickness by room-temperature electrochemical conversion of MnO grown by atomic layer deposition (ALD). Next, we investigate the charge storage properties of LiMn2O4 thin films in electrolytes containing Li+ with Na+, K+, and Mg2+. Our CV experiments demonstrate that for sweep rates between 1 and 400 mV/s, up to 30% of the capacity of LiMn2O4 arises from bulk electronic charge-switching which does not require compensating cation mass transport. The hybrid ALD-electrochemical synthesis, coupled electrochemical and electronic structure analysis, and unique charge storage mechanism we describe provide a fundamental framework to guide the development of future nanoscale electrode materials for ion-incorporation charge storage.

Novel mesoporous microspheres of Al and Ni doped LMO spinels and their performance as cathodes in secondary lithium ion batteries

ABSTRACTA facile, scalable, and solution-based technique is used to fabricate Al and Ni-doped (LiAl0.1Mn1.9O4 and LiAl0.1Ni0.1Mn1.8O4) microspheres of lithium manganese oxide (LMO) spinels for use as reversible cathode materials for lithium ion batteries (LIBs). The spheres of the two samples exhibit different porosities. Cells with these LMO-based cathodes are then cycled between 4.5 V and 2 V to study their stabilities while simultaneously being subjected to the undesirable Jahn-Teller distortion that occurs around the ~3 V regime. The LiAl0.1Mn1.9O4 (LAMO) and the LiAl0.1Ni0.1Mn1.8O4 (LANMO) cells exhibit comparable open circuit voltages (OCV) of 2.94 V and 2.97 V, respectively. During cell cycling, the LAMO cell exhibits a maximum specific capacity of 122.51 mAh g−1 with a capacity fade of 65.35% after 75 cycles. The LiAl0.1Ni0.1Mn1.8O4 (LAMO) sample fares better and exhibits a maximum of 140.49 mAh g−1 and a capacity drop of 52.59%. Detailed structural studies indicate that Ni doping and the greater degree of porosity of the LANMO sample to be a stabilizing factor. This is further confirmed by cyclic voltammetry (CV) and AC impedance spectra analysis.

Electrochemical properties of niobium and phosphate doped spherical Li-rich spinel LiMn2O4 synthesized by ion implantation method

Spherical Li-rich lithium manganese oxide (LMO) spinel material was synthesized by an ion implanted method assisted by polyalcohol doped with Niobium and Phosphate simultaneously. The material was characterized by scanning electron microscopy, X-ray diffraction and BET specific surface area analysis. The electrochemical performances were investigated with galvanostatic techniques and cyclic voltammetry. The synthesis process was investigated with TG/DSC. The results show that the lithium ion can be immersed into the pore of manganese dioxide at a low temperature with the ion implanted method. The prepared materials have a higher discharge capacity and better crystallization than those prepared by solid phase method. The doped Nb can improve the capacity of the Li-rich LMO spinel and reinforce the crystal growth along (111) and (400) planes. The crystal grains show circular and smooth morphology, which makes the specific surface area greatly decreased. Phosphate-doped LMO spinel exhibits good high-rate capacity and structure stability. The prepared Li1.09Mn1.87Nb0.031O3.99(PO4)0.021 delivers a discharge capacity of 119mAhg−1 at 0.2°C (1°C=148mAg−1) and 112.8mAhg−1 at 10°C, the discharge capacity retention reaches 98% at 1°C after 50 cycles at 25°C and 94% at 55°C.

Low content Ni and Cr co-doped LiMn2O4 with enhanced capacity retention

Nanoparticles of the pure and Ni–Cr co-doped lithium manganese oxides Li[NixCryMn2-x-y]O4 (x = y = 0.01–0.05) have been synthesized by sol–gel method using citric acid as a chelating agent. The effect of low-content doping was noted reflecting the faster ionic movement in the cathode material. The phase structure and morphology of the materials are characterized by XRD, FTIR, SEM and TEM. Electrochemical and impedance measurements established that low-content Ni–Cr substitution substantially improves the structural stability and high rate cycling performance of LiMn2O4. Among all the investigated compositions, LiNi0.01Cr0.01Mn1.98O4 demonstrated the best electrochemical performance. At a substantially high current rate of 5 C, 82% of the initial discharge capacity at 0.1 C is retained. Remarkably, after deep cycling at high rates, a discharge capacity of 104 mAhg−1 is resumed upon reducing the current rate to 0.1 C which is 91% of the specific capacity in the first cycle.

Study on Factors for Accurate Open Circuit Voltage Characterizations in Mn-Type Li-Ion Batteries

Open circuit voltage (OCV) of lithium batteries has been of interest since the battery management system (BMS) requires an accurate knowledge of the voltage characteristics of any Li-ion batteries. This article presents an OCV characteristic for lithium manganese oxide (LMO) batteries under several experimental operating conditions, and discusses factors for accurate OCV determination. A test system is developed for OCV characterization based on the OCV pulse test method. Various factors for the OCV behavior, such as resting period, step-size of the pulse test, testing current amplitude, hysteresis phenomena, and terminal voltage relationship, are investigated and evaluated. To this end, a general OCV model based on state of charge (SOC) tracking is developed and validated with satisfactory results.

Comprehensive Enhancement of Nanostructured Lithium-Ion Battery Cathode Materials via Conformal Graphene Dispersion.

Efficient energy storage systems based on lithium-ion batteries represent a critical technology across many sectors including consumer electronics, electrified transportation, and a smart grid accommodating intermittent renewable energy sources. Nanostructured electrode materials present compelling opportunities for high-performance lithium-ion batteries, but inherent problems related to the high surface area to volume ratios at the nanometer-scale have impeded their adoption for commercial applications. Here, we demonstrate a materials and processing platform that realizes high-performance nanostructured lithium manganese oxide (nano-LMO) spinel cathodes with conformal graphene coatings as a conductive additive. The resulting nanostructured composite cathodes concurrently resolve multiple problems that have plagued nanoparticle-based lithium-ion battery electrodes including low packing density, high additive content, and poor cycling stability. Moreover, this strategy enhances the intrinsic advantages of nano-LMO, resulting in extraordinary rate capability and low temperature performance. With 75% capacity retention at a 20C cycling rate at room temperature and nearly full capacity retention at -20 °C, this work advances lithium-ion battery technology into unprecedented regimes of operation.

A facile low-temperature synthesis of Li4Mn5O12 nanorods

The present work provides a facile novel method for the low-temperature synthesis of Li4Mn5O12 spinel, a lithium manganese oxide that can potentially be used for application as cathode material in rechargeable lithium ion batteries, in supercapacitors, in magnetic devices, etc. Pure Li4Mn5O12 has been prepared using pre-synthesized nanostructured MnOOH nanowires as manganese sources and lithium salt at fairly low temperature. XRD, FESEM, HRTEM, and ICP-MS results revealed the formation of perfect cubic phase Li4Mn5O12 nanorods. Based on the results obtained, a mechanism of formation of Li4Mn5O12 nanorod is proposed.

Electrochemical properties of LiMn2O4 prepared with tartaric acid chelating agent

Lithium manganese oxide (LiMn2O4) has been prepared using sol-gel technique under acidic (pH = 5.8) and alkaline (pH = 9) conditions with tartaric acid as chelating agent. X-ray studies show that under acidic condition, an Mn2O3 peak was observed indicating the presence of impurities. No impurity was observed for LiMn2O4 under alkaline conditions. The particle size is mostly in the range of 124 to 185 nm from HR-TEM. The lithium diffusion coefficient, D Li+ in LiMn2O4 is of the order 10−9 cm2 s−1. By using density functional theory (DFT) calculations, structural properties have been obtained. The specific discharge capacity of the cells with LiMn2O4 prepared under alkaline condition and with LiMn2O4 prepared under acidic condition discharged at 0.5 C is in the ranges of 132 to 142 and 128 to 139 mAh g−1, respectively.

Experimental assessment and model development of cycling behavior in Li-ion coin cells

The electrochemical performance of mesocarbon microbeads (MCMB)-lithium manganese oxide (LMO) spinel cells is examined by cyclic voltammetry, galvanostatic cycling and electrochemical impedance spectroscopy. The loss in capacity in full-cells is attributed to occurrence of parasitic reactions at the two electrodes. The contribution of each electrode in full-cell degradation is ascertained through testing of MCMB and LMO half-cells, with the former exhibiting a faster rate of degradation as compared to the latter. Lithium diffusion coefficient of MCMB and LMO electrodes are determined using the galvanostatic intermittent titration technique at various stages of cycling. The experimentally measured parameters are used to simulate the electrochemical behavior of MCMB and LMO half-cells. The computed capacity and cell potential variation show good agreement with experimentally obtained data for half-cells at 1C and 2C currents. The MCMB half-cell simulations reveal that loss in discharge capacity occurs due to thickening of SEI film, increase in gas formation and loss in cyclable lithium. Simulations of LMO half-cells show that capacity loss with cycling is a result of reduction in active material, increase in surface resistance with inactive material deposition and loss in cyclable lithium.