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— This work reports the synthesis and electrochemical performance of the nickel-doped lithium manganese oxide along with the surface modification of the mentioned oxide coated with the aluminum oxide via a solid state route. The structural and functional groups were confirmed by the X-ray powder diffraction and Raman spectroscopy studies, respectively. A pyramid-like structure of the pure lithium manganese oxide and a plate-like structure of lithium manganese nickel oxide coated by Al 2 O 3 were confirmed by the field emission scanning electron microscopy. The exchange current density and the charge transfer resistance were calculated via electrochemical impedance spectroscopy in an aqueous electrolyte system. In that system, the electrochemical behaviour of the lithium manganese oxide, of the lithium manganese nickel oxide, and of the Al 2 O 3 coated lithium manganese nickel oxide was studied by the charge/discharge analysis. The Al 2 O 3 coated lithium manganese nickel oxide exhibits 91% capacity retention up to 100 charge/discharge cycles as well as a lower charge transfer resistance which are far better than previously reported values.

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.

Lithium manganese spinel (LiMn2O4) is considered a promising cathode material for lithium-ion batteries (LIBs). Its structure, morphology, and electrochemical performances are strongly connected to the precursors, synthesis route, and heat treatment; hence, by optimizing the synthesis procedure, improved materials can be obtained. Recently investigated routes focus on the synthesis of enhanced LiMn2O4 spinel, with uniform morphology, high crystallinity, which can deliver large discharge capacity at high rates for a longer period of time. Also, the synthesis procedure must be easily applicable on industrial scale, not just for pilot and laboratory investigations. In the current study, main synthesis procedures (solid-state reactions, sol-gel, hydrothermal reactions, combustion method plus several newly employed methods) used for obtaining lithium manganese oxide, along with its electrochemical effectiveness, are described. Among the considered synthesis methods, some of the best electrochemical performances are recorded for lithium manganese oxide obtained by sol-gel process and hydrothermal method. Even though solid-state reaction method is a simple and has few stages, particle crystallinity and size are more difficult to control, while sol-gel and hydrothermal method provides more evenly sized particles. Also, the latter two syntheses do not need very high calcination temperatures like in the samples obtained by solid-state reactions method. Lithium manganese spinel with uniform spherical and octahedral particles delivered the highest initial discharge capacities and has the ability to retain most of the capacity during the charge–discharge cycles.

In this work, a facile, wet chemical synthesis was utilized to achieve a series of lithium manganese oxide (LiMn2O4, (LMO) with 1–5%wt. graphene oxide (GO) composites. The average crystallite sizes estimated by the Rietveld method of LMO/GO nanocomposites were in the range of 18–27 nm. The electrochemical performance was studied using CR2013 coin-type cell batteries prepared from pristine LMO material and LMO modified with 5%wt. GO. Synthesized materials were tested as positive electrodes for Li-ion batteries in the voltage range between 3.0 and 4.3 V at room temperature. The specific discharge capacity after 100 cycles for LMO and LMO/5%wt. GO were 84 and 83 mAh g−1, respectively. The LMO material modified with 5%wt. of graphene oxide flakes retained more than 91% of its initial specific capacity, as compared with the 86% of pristine LMO material.

LiMn2O4 (LMO) spinel cathode materials suffer from severe degradation at elevated temperatures because of Mn dissolution. In this research, monobasic sodium phosphate (NaH2PO4, P2) is examined as an electrolyte additive to mitigate Mn dissolution; thus, the thermal stability of the LMO cathode material is improved. The P2 additive considerably improves the cyclability and storage performances of LMO/graphite and LMO/LMO symmetric cells at 60 °C. We explain that P2 suppresses the hydrofluoric acid content in the electrolyte and forms a protective cathode electrolyte interphase layer, which mitigates the Mn dissolution behavior of the LMO cathode material. Considering its beneficial role, the P2 additive is a useful additive for spinel LMO cathodes that suffer from severe Mn dissolution.

The advantages of Cr substitution in lithium manganese oxide (LiMn 2 O 4 ) for cathode of rechargeable battery were investigated. LiCr x Mn 2- x O 4 ( x  ≤ 0.3) thin films were deposited on Pt/Ti/SiO 2 /Si substrates via a sol–gel process. The LiCr x Mn 2- x O 4 specimens were found to have the spinel structure of pristine LiMn 2 O 4 with no detectable secondary phase. The Cr ions were found to be trivalent and to occupy the octahedral sites of the spinel lattice. The Cr-substituted specimens exhibited a new phonon mode near 570 cm −1 in the Raman spectrum. It is ascribed to octahedral Cr 3+ −O bonding (T 2g ) that is located close to the mode due to octahedral Mn 3+ −O bonding (580 cm −1 ). According to charge-discharge (C-D) cycling data on the LiCr x Mn 2- x O 4 cathodes, the specimens of x  = 0.02 and 0.05 kept larger capacities than that of the pristine LiMn 2 O 4 cathode up to 700 cycles. The x  = 0.05 cathode showed initial capacity close to that of x  = 0.02. Above 100 th cycle, the x  = 0.05 cathode showed better capacity retention than that of x  = 0.02. Possible reason for the improved capacity retention by the Cr substitution was discussed. Graphical Abstract Highlights LiCr x Mn 2− x O 4 ( x  ≤ 0.3) thin films were fabricated on Pt/Ti/SiO 2 /Si substrates by using a sol–gel technique and post-annealing in air for 6 h at 700 °C. The LiCr x Mn 2- x O 4 specimens were found to have the spinel structure of pristine LiMn 2 O 4 with no detectable secondary phase. The Cr ions were found to be trivalent and to occupy the octahedral sites of the spinel lattice. A new phonon mode (δ) near 570 cm −1 observed in the Raman spectra of the Cr-substituted specimens confirms the octahedral Cr 3+ occupation in the spinel lattice. The LiCr x Mn 2- x O 4 cathodes with small Cr 3+ compositions ( x   <  0.1) exhibited better capacity retention than the pristine LiMn 2 O 4 cathode.

Lithium manganese oxide is regarded as a capable cathode material for lithium-ion batteries, but it suffers from relative low conductivity, manganese dissolution in electrolyte and structural distortion from cubic to tetragonal during elevated temperature tests. This review covers a comprehensive study about the main directions taken into consideration to supress the drawbacks of lithium manganese oxide: structure doping and surface modification by coating. Regarding the doping of LiMn2O4, several perspectives are studied, which include doping with single or multiple cations, only anions and combined doping with cations and anions. Surface modification approach consists in coating with different materials like carbonaceous compounds, oxides, phosphates and solid electrolyte solutions. The modified lithium manganese oxide performs better than pristine samples, showing improved cyclability, better behaviour at high discharge c-rates and elevated temperate and improves lithium ions diffusion coefficient.

Current ab-initio approaches such as Quantum Mechanics (QM) calculations or Molecular Dynamics (MD) simulations to study the doped cathode structures are computationally expensive. In this work, we present the development and application of neural computing models to study the crystal structure of the cathode materials in Lithium-ion batteries, Lithium Manganese Oxide (LMO) in particular. We do this using LMO crystal configurations doped with Aluminum. We successfully demonstrate the application of 8 multi-layer perceptron models that are capable of predicting the potential energy of LMO crystal configurations, with coefficients of determination ( R 2 ) ranging from 0.95 to 0.98. To achieve this, models were developed by training and testing them on the potential energy (eV) values of over 460,000 crystal configurations. In lithium-ion battery research, the developed Neural Network models could be utilized alongside existing atomic or molecular simulation tools to efficiently identify optimal crystal configurations that could be subjected to more detailed investigation. With the integration of the multi-layer perceptron models of this work, the total time to evaluate all possible crystal configurations can be reduced by approximately 88% than when using just QM and MD simulations for such evaluations.

Lithium manganese oxide, LiMn2O4 (LMO) is a promising cathode material, but is hampered by significant capacity fade due to instability of the electrode-electrolyte interface, manganese dissolution into the electrolyte and subsequent mechanical degradation of the electrode. In this work, electrochemically-induced strains in composite LMO electrodes are measured using the digital image correlation (DIC) technique and compared with electrochemical impedance spectroscopy (EIS) measurements of surface resistance for different scan rates. Distinct, irreversible strain variations are observed during the first delithiation cycle. The changes in strain and surface resistance are highly sensitive to the electrochemical changes occurring during the first cycle and correlate with prior reports of the removal of the native surface layer and the formation of cathode-electrolyte interface layer on the electrode surface. A large capacity fade is observed with increasing cycle number at high scan rates. Interestingly, the total capacity fade scales proportionately to the strain generated after each lithiation and delithiation cycle. The simultaneous reduction in capacity and strain is attributed to chemo-mechanical degradation of the electrode. The in situ strain measurements provide new insight into the electrochemical-induced volumetric changes in LMO electrodes with progressing cycling and may provide guidance for materials-based strategies to reduce strain and capacity fade.

In order to improve the universality of LiMn2O4 materials, LiMn2O4 coated with Al2O3 (LMO@Al) is prepared by a co-precipitated method to improve the electrochemical performance of the porous LiMn2O4 cathode. The morphologies and microstructures are characterized by X-ray diffraction, scanning electron microscope, transmission electron microscope, and energy-dispersive spectroscopy. The electrochemical performances are investigated by galvanostatic charge-discharge test system and inductively coupled plasma emission spectrograph. The results show that the Al2O3 coating uniformly as well as tightly coupled with LiMn2O4 particles. The LMO@Al cathode material also shows outstanding electrochemical behaviors. After 100 cycles, the capacitance can remain 98.6 and 91.2% at 25 and 55 °C, respectively. Moreover, the LMO@Al composite cycled reversibly at 25 °C for 10 C with stable discharge capacities of 94.4 mAh g−1. Superior electrochemical stability of the LMO@Al can be attributed to the uniform coating which inhibited the manganese dissolution and Jahn-Teller effect of LiMn2O4 materials as well as the decomposition of the electrode by HF corrosion. The LMO@Al obtained from this work can open a new possibility in high power lithium ion batteries application.