Performance Of LiMn2O4 Research Articles

Lithiation Mechanism Change Driven by Thermally Induced Grain Fining and Its Impact on the Performance of LiMn2 O4 in Lithium-Ion Batteries.

The nature of precursors employed in the synthesis of lithium-ion battery cathode materials is a crucial performance-dictating factor. Therefore, it is of great importance to establish a way to manipulate the precursor and seek a comprehensive understanding of its influence on the electrochemical behavior of a targeted electrode material. A thermal route is herein demonstrated for the synthesis of lithium-excess LiMn2 O4 (LMO) by exploiting an intriguing thermal phenomenon, thermally induced grain fining, and sheds light on how it affects the mechanism and kinetics of lithiation, and, furthermore, the electrochemical behavior of LMO. Detailed insights into the lithiation mechanism and kinetics reveal that the use of a finely grained, porous Mn3 O4 , which possesses an open crystal structure, is a key to the success of incorporating excess Li. In addition, this in-depth electrochemical investigation verifies a very recent theoretical prediction of faster Li diffusion kinetics enabled by excess Li.

Enhancing the durable performance of LiMn2O4 at high-rate and elevated temperature by nickel-magnesium dual doping

Various nickel and magnesium dual-doped LiNixMg0.08Mn1.92−xO4 (x ≤ 0.15) were synthesized via a modified solid-state combustion method. All as-prepared samples show typical spinel phase with a well-defined polyhedron morphology. The Ni-Mg dual-doping obviously decreases the lattice parameter that gives rise to the lattice contraction. Owing to the synergistic merits of metal ions co-doping, the optimized LiNi0.03Mg0.08Mn1.89O4 delivers high initial capacity of 115.9 and 92.9 mAh·g−1, whilst retains 77.1 and 69.7 mAh·g−1 after 1000 cycles at 1 C and high current rate of 20 C, respectively. Even at 10 C and 55 °C, the LiNi0.03Mg0.08Mn1.89O4 also has a discharge capacity of 92.2 mAh·g−1 and endures 500 cycles long-term life. Such excellent results are contributed to the fast Li+ diffusion and robust structure stability. The anatomical analysis of the 1000 long-cycled LiNi0.03Mg0.08Mn1.89O4 electrode further demonstrates the stable spinel structure via the mitigation of Jahn-Teller effect. Hence, the Ni-Mg co-doping can be a potential strategy to improve the high-rate capability and long cycle properties of cathode materials.

Surfactant-assisted synthesis of LiMn2O4 particles as high-rate and long-life cathode materials for lithium-ion batteries

Herein, we reported the synthesis of uniform LiMn2O4 submicroparticles by surfactant-assisted preparation of spherical MnCO3 precursor followed by solid-state reaction. Polyethylene glycol (Mw = 1000) was used as surfactant to control the morphology and size of the MnCO3 precursor as well as the MnO2 intermediate and LiMn2O4 product. The influence of particle size, homogeneity, and crystallinity on the electrochemical performance of LiMn2O4 was intensively investigated. The test results indicate that the LiMn2O4 sample using polyethylene glycol with weight as 10% of reactants shows the best rate capability and long-term cyclability. Due to the homogeneous particles with the average size of ca. 250 nm and high crystallinity, the discharge capacities are as high as 125, 118, 114, and 100 mAh g−1 at 1, 10, 20, and 50 C rates, respectively, along with high capacity retention of 74% after 1000 cycles at 20 C.

Multiphase combustion synthesis and enhanced performance of LiMn2O4 nanoparticles using CNTs as a fuel

LiMn2O4 nanoparticles were successfully prepared using suitable dosage carbon nanotubles (CNTs) as a fuel through multiphase combustion synthesis. The effects of CNTs on the structure and electrochemical performance of LiMn2O4 were investigated. Rate performance test demonstrates that CNTs dosage greatly affect the electrochemical behaviour of LiMn2O4 and LiMn2O4 prepared by choosing suitable CNTs dosage (7%) as a fuel (C7%-LMO) shows high rate charge–discharge capability. X-ray diffraction results indicate that C7%-LMO has the smallest distortion degree in the crystal, compared to LiMn2O4 prepared without CNTs (C0%-LMO) and LiMn2O4 prepared with 10% CNTs (C10%-LMO). SEM results reveal that the average particle size of C7%-LMO is about 100 nm, which is the smallest among the three samples (C0%-LMO, C7%-LMO and C10%-LMO). This unique microscopic features guarantee C7%-LMO possesses the highest discharge capacity, the best cycling performance and the lowest charge transfer resistance among the three samples.

Improvement of the overall performances of LiMn2O4 via surface-modification by polypyrrole

Polypyrrole (PPy) is an excellent conductive polymer and the study on its utilization in the surface modification of the LiMn2O4 (LMO) is few. In this work, the structure, morphology and electrochemical performance of surface-modified LiMn2O4 composites with PPy and polyimides (PI) were discussed. The crystal structure, chemical bonds and morphology were characterized through X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM), respectively. Moreover, the specific power and cycling performance were tested at room and high (55°C) temperature. The PPy@LMO (surface-modified LMO composites with PPy) shows better performances than the pristine LMO. The addition of PPy not only weakens the corrosion caused by electrolyte, but also improves the discharge capacity at higher rates. The charge transfer resistance of the PPy@LMO is much lower than that of the pristine LMO after cycling.

Capacity Fade Study of LiCo0.4Al0.1Mn1.5O4 Cathode Material for Li-Ion Batteries Cycled at Low Discharge Rates

In order to improve the cycling performance of LiMn2O4 based cathode materials, we have synthesized a new composition LiCo0.4Al0.1Mn1.5O4 by sol-gel method. In the path of the material synthesis, citric acid was added to serve as a binding agent and a gelling agent respectively, followed by calcinations at 850°C for 12 h. The synthesized material was well characterized by TG/DTA, XRD, FTIR, EPR, SEM, electrical and electrochemical tests. It was found that LiCo0.4Al0.1Mn1.5O4 powder has an ordered cubic spinel phase (space group Fd3m) and exhibits good rate capability. The electrical and electrochemical characterization was carried out in CR-2032 coin type cell configuration. The material delivers an initial discharge capacity of 48 mAhg-1 between 3.5 and 4.9 V at a C/10 rate and subjected for more than 30 cycles. The electrochemical behavior is well supported with impedance data.

Enhanced High-Temperature Cycling Stability of LiMn<sub>2</sub>O<sub>4</sub> by Coating LiNi<sub>0.5</sub>Mn<sub>1.5</sub>O<sub>4</sub>

To enhance the electrochemical performances of LiMn2O4 at elevated temperature (55°C), we proposed a sol-gel method to synthesize LiNi0.5Mn1.5O4 modified LiMn2O4. The physical and electrochemical performances of pristine and LiNi0.5Mn1.5O4-coated LiMn2O4 cathode materials were investigated by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy and electrochemical measurements, respectively. The results indicated that about 4-5 nm thick layer of LiNi0.5Mn1.5O4 was formed on the surface of the LiMn2O4 powders. The modified LiMn2O4 exhibited excellent storage performance at 55&degC compared to the pristine one, which was attributed to the suppression of electrolyte decomposition and the reduction of Mn dissolution.

Study on the performance of LiMn2O4 using spent Zn–Mn batteries as manganese source

Recycling spent Zn–Mn batteries by synthesizing the products with high added value is very active internationally. In this work, we have successfully synthesized the spinel LiMn2O4 cathode materials for rechargeable lithium-ion batteries by simple sol–gel method using the manganese source that is recovered from spent Zn–Mn batteries through hydrometallurgy recycling technology. The influence of sintering temperature on the structure, the morphological properties, and the electrochemical properties of the product is investigated. The results show that spinel LiMn2O4 prepared at 700 °C has the best comprehensive performance. Moreover, the electrochemical performance of spinel LiMn2O4 has been further optimized by Co-ion doping.

Preparation and electrochemical properties of x Li2MnO3·(1-x)LiMn2O4 composites

Li2MnO3-doped spinel LiMn2O4 composites were synthesized by sol-gel method to improve the electrochemical performance of LiMn2O4. The microstructures, morphologies and electrochemical performance of the obtained xLi2MnO3·(1-x)LiMn2O4 composites were characterized by X-ray diffraction(XRD), scan electron microscopy(SEM) and a galvanostatic charge-discharge process. It was found that both Li2MnO3 and LiMn2O4 components exist in xLi2MnO3·(1-x)LiMn2O4(0<x<1) composites. The 0.3Li2MnO3·0.7LiMn2O4 composite shows the optimized electrochemical performance, including discharge capacity and cycle stability. It was demonstrated that Li2MnO3-doped spinel LiMn2O4 cathode material can work at wide potential window with quite good capacity retention and considerably larger reversible capacity compared to single-phase LiMn2O4 component.

Effect of electrolytic MnO2 pretreatment on performance of as-prepared LiMn2O4

To investigate the effect of electrolytic MnO2 (EMD) on the performance of LiMn2O4, several pretreatment methods, such as acid treating, presintering and impregnating with chromic salt, were used. The pretreated EMD and prepared LiMn2O4 were characterized by X-ray diffraction and inductively coupled plasma emission spectrometry. Charge and discharge tests of Li/LiMn2O4 batteries were also employed to evaluate electrochemical performance. The experimental results show that inorganic impurity contents in EMD decrease remarkably after acid treating; presintering EMD can remove adsorbent water and organic impurity, enlarge pore space and increase active reaction sites; pre-doping chromium in EMD can form more homogenous compound substance LiCr0.05Mn1.95O4, which shows better structural stability and capacity retention.

Study on the Storage Performance of Manganese Spinel Battery

The power battery was manufactured with the commercial LiMn2O4 and graphite, and its storage performances with different charged state were studied. Structure, morphology and surface state change of the LiMn2O4 before and after storage were observed by XRD, XPS and AC technique, respectively. The result shows that the capacity recovery of LiMn2O4 stored at discharge state is best (99.2%). While that of full-charged state is worst (93.6%). The cyclic performance of LiMn2O4 stored at full-charged state is best (capacity retention ratio of 89.8% after 200 cycles), while that of before storage is 83.0%. The crystal of the spinel was destroyed after storage, and the intensity of breakage is increased with charged state increasing. The amount of soluble Mn and Li-ion migration resistance (Rf) are increased with chare state increasing, and the oxygen loss is detected.

Synthesis and electrochemical performance of YF3-coated LiMn2O4 cathode materials for Li-ion batteries

Spinel LiMn2O4 cathodes were coated with 1 mol% YF3. X-ray diffraction (XRD) analyses showed that Y and/or F did not enter the lattice of the LiMn2O4 crystal. Transmission electron microscopy (TEM) showed that a compact YF3 layer of 5-20 nm in thickness was coated onto the surface of LiMn2O4 particles. Scanning electron microscopy (SEM) observation showed that the YF3 coating caused the agglomeration of LiMn2O4 particles. The cycling test demonstrated that the YF3 coating can improve the electrochemical performance of LiMn2O4 at both 20 and 55℃. Moreover, YF3-coated LiMn2O4 exhibited an improved rate capability compared with the uncoated one at high rates over 5C. The immersion test in electrolytes showed that YF3-coated LiMn2O4 is more erosion resistant than the uncoated one.

Synthesis and Lithium Battery Properties of LiM(M=Fe,Al,Mg)&lt;sub&gt;x&lt;/sub&gt;Mn&lt;sub&gt;2-x&lt;/sub&gt;O&lt;sub&gt;4&lt;/sub&gt; Powders by Spray Pyrolysis

LiM(M=Fe,Al,Mg)XMn2-XO4 fine powders were synthesized by the ultrasonic spray pyrolysis using metal nitrate solution. LiMn2O4 powders obtained by this method have a spherical morphology with a submicron size. XRD revealed that as-prepared powders were crystallized to spinel structure with Fd3m space group. LiM(M=Fe,Al,Mg)XMn2-XO4 showed enhanced cycling performance at room temperature. Reduced Jahn-Teller distortion of LiMn2O4 by metal doping was responsible for enhanced cycle performance of LiMn2O4.

Preparation, characterization and electrochemical performance of γ-MnO2 and LiMn2O4 as cathodes for lithium batteries

The spinel LiMn2O4 is a very promising cathode material with economical and environmental advantages. LiMn2O4 materials have been synthesized by solid state method using γ-MnO2 as manganese source, and Li2CO3 or LiNO3 as Li sources. γ-MnO2 is a commercial battery grade electrolytic manganese dioxide (TOSOH-Hellas GH-S) and LiMn2O4 samples were synthesized at a calcinations temperature up to 800 °C. γ-MnO2 and LiMn2O4 samples were characterized by X-ray diffraction, thermal and electrochemical measurements. X-ray powder diffraction of as prepared LiMn2O4 showed a well-defined highly pure spinel single phase. The electrochemical performance of LiMn2O4 and its starting material γ-MnO2 was evaluated through cyclic voltammetry, galvanostatic (constant current charge-discharge cycling) The electrochemical properties in terms of cycle performance were also discussed.

Synthesis of Al-doped LiMn2O4spinels by mechanical alloying and rotary heating

LiMn2O4 has been widely studied as the cathode material for Li-ion batteries because of its low cost, environmental merit and relatively high voltage [1–3]. However, it shows significant capacity fading and poor cycleability. A very effective way for improving the cycling performance of LiMn2O4 is to synthesize manganese-substituted LiMx Mn2−x O4 spinel phase by doping with divalent or trivalent ions (M = Al, Mg, Co, Ni, Fe, Ti, Zn and Cr, etc.) [4–8]. The conventional synthesis method of LiMn2O4 is direct solid-solid reaction of oxides and carbonate of manganese and either LiOH, or Li2CO3 and LiNO3 at high temperatures to enhance the diffusion process and obtain a well-ordered structure. Due to this high temperature, there are some disadvantages such as broader particle size distribution, longer reaction time or other unwanted phases. However, solid-state reaction technology is easy and simple, and is one of the most suitable techniques for industrialization. The obstacles to the solid-state reaction are mainly the higher synthesis temperature and longer high temperature reaction time, together with the difficulties in the effective controls of chemical composition and microstructures. In recent years great progress has been mode in developing new synthesis methods of LiMn2O4 [9–13]. One of the main approaches is mechanical alloying. The works of Kosova et al. [11–13] on LiMn2O4 showed that mechanical alloying significantly decreased the synthesis temperature and the resulting products exhibited tolerable electrochemical performances. Mechanical alloying can produce particle and grain sizes down to the nanoscale, together with structure defects. Energetic lattice defects, combined with short diffusion distances, are the driving forces for faster solid-state alloying and chemical reactions at low temperatures. The high temperature furnaces for solid-state synthesis, at present, are mainly periodical kilns or furnaces. The powders in these equipments are static. Therefore the temperature field within the powders is often nonuniform during heating or cooling, especially for mass production, which will result in non-uniform chemical composition and non-uniform particle size distribution in a batch of synthesized powders. On the other hand, these mechanically alloyed initial powders easily grow during the following high temperature treatment,

Chromium-ion doped spinel lithium manganate nanoparticles derived from the sol-gel process

Lithium ion secondary batteries have been widely applied in high-tech electronic devices such as cellular phones and notebook computers owing to their high working voltage, low self-discharge rate, and elevated energy density [1, 2]. In lithium ion batteries, cathode materials play an important role in modulating the electrochemical performance. Lithiated transition oxides such as lithium cobalt oxide, lithium nickelate, and lithium manganate are usually adopted as the cathode materials. LiMn2O4 is a potential cathode material owing to its low cost, low toxicity, and acceptable safety [3–6]. However, LiMn2O4 suffers a severe capacity fading problem after long-term cycling, and such a problem limits its application. In order to improve the cycleability of LiMn2O4, doping other cations into the spinel compound has been intensively investigated [7–9]. The spinel compound can be stabilized via doping M (III) cations into the host structure by inhibiting the Jahn-Teller distortion. In the previous work, chromium ions have been found to be an effective dopant for improving the cycling performance of LiMn2O4 [10]. Traditionally, LiMn2−x Crx O4 powders are prepared through the solid-state reaction; however, the particle size of the obtained powders is large and their morphology is not well controlled. In order to obtain ultrafine and uniform cathode powders, some newly developed solution techniques have been been used to satisfy these demands [11–14]. A PVA sol-gel process has been investigated in this study. This process has been found to be a potential method to prepare nanosized ceramic powders with improved electrochemical performance. It is revealed that the obtained powders exhibit not only enhanced cycling performance, but also good discharge capacities at ambient temperature as well as elevated temperatures. An aqueous solution containing lithium nitrate (LiNO3), chromium nitrate (Cr(NO3)3), and manganese nitrate (Mn(NO3)2) was initially prepared with the overall cationic concentration maintained at 1 M. Reagent-grade PVA was completely dissolved in deionized water, and then added into the above solution. The resulting viscous solution comprising of the starting materials and the PVA solution was dried at 80 ◦C to obtain the precursor powders. These dried precursor powders were subsequently calcined at various temperatures ranging from 500 to 900 ◦C to synthesize the desired spinel compounds.