Li Secondary Batteries Research Articles

Dependence of Properties, Crystal Structure and Electrode Characteristics on Li Content for Lix(Ni,Co)O2 as a Cathode Active Material for Li Secondary Batteries

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A Study on the LiMn2O4 Cathodes with Mesh-Like Structures for Li Secondary Batteries

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Relationship Between Thermodynamic Stability, Crystal Structure, Properties and Cathode Performance Depend on Different Synthetic Process and Li Content of Lix(Mn1/3Co1/3Ni1/3)O2 as a Cathode Active Material for Li Secondary Battery

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A study on electrochemical characteristics of LiCoO 2/LiNi 1/3Mn 1/3Co 1/3O 2 mixed cathode for Li secondary battery

In this study, the LiCoO 2/LiNi 1/3Mn 1/3Co 1/3O 2 mixed cathode electrodes were prepared and their electrochemical performances were measured in a high cut-off voltage. As the contents of LiNi 1/3Mn 1/3Co 1/3O 2 in the mixed cathode increases, the reversible specific capacity and cycleability of the electrode enhanced, but the rate capability deteriorated. On the contrary, the rate capability of the cathode enhanced but the reversible specific capacity and cycleability deteriorated, according to increasing the contents of LiCoO 2 in the mixed cathode. The cell of LiCoO 2/LiNi 1/3Mn 1/3Co 1/3O 2 (50:50, wt.%) mixed cathode delivers a discharge capacity of ca. 168 mAh/g at a 0.2 C rate. The capacity of the cell decreased with the current rate and a useful capacity of ca. 152 mAh/g was obtained at a 2.0 C rate. However, the cell shows very stable cycleability: the discharge capacity of the cell after 20th charge/discharge cycling maintains ca. 163 mAh/g.

Electrochemical properties of LiNiO 2 cathode material synthesized by the emulsion method

LiNiO 2 powder, cathode material of Li secondary battery, was prepared by the emulsion method. Shape, crystal phase and electrochemical properties of the powders heated to various temperatures for various times were investigated by SEM, XRD and a charge–discharge tester. Single phase LiNiO 2 could be synthesized at 700 °C for 24 h, i.e. at a lower temperature compared with other processes. The optimum heating temperature and time for LiNiO 2 synthesis were 750 °C and 24 h in an oxygen stream. The powder calcined at 750 °C for 24 h has the highest I 0 0 3 / I 1 0 4 value and the first largest discharge capacity (161 mAh g −1 at the 1st cycle and 147 mAh g −1 at the 20th cycle).

Critical Pore Wall Thickness of Mesoporous Tin Phosphate for Li Secondary Battery

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Thixotropic Electrolytes Based on Hydrophilic Silica in the Presence of Polyethylene Oxide for Li-Secondary Batteries

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Characteristics of LLT Thin Film as Electrolyte of Li Secondary Battery Deposited by Sputtering Method

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Properties, Crystal Structure, and Performance of o- LiMnO2 as Cathode Material for Li Secondary Batteries

Orthorhombic (o-) was prepared as a cathode material for Li secondary batteries by the solid-state, sol-gel, and reflux heating methods. Reflux heating yielded a single phase whose composition we were able to control. The particle size distribution of this o- was uniform. Its discharge capacity at 25°C was the lowest and its cycle performance the most stable among the produced by the three methods. The discharge capacity increased with cycle number and stabilized at about 30–40 cycles at 25°C. We investigated the relationship between the diffusion coefficient and the crystal structure during the cycles. The for at the stable cycle region is larger than that at the initial cycle and was almost constant during the charge–discharge process at 25°C. The at 30, 40 cycles corresponded almost exactly to that of the spinel . Refinement of the sample was performed in 30 cycles by assuming two phases of space group . The electron-density images suggest that the covalent bond of Mn–O was stronger for the sample synthesized by reflux heating than those synthesized by the solid-state method. The high-crystallinity o- leads to better stability and slower conversion to spinel .

Electronic Structure of LiMn1-xMxO2(M=Mn, Co, Ni, Zn) as a Cathode Active Material for Li Secondary Battery by MEM/Rietveld Analysis and First Principles Calculations

We synthesized the LiMn1-xMxO2 (M=Mn, Co, Ni) and investigated the electron density map by X-ray diffraction using the Maximum Entropy Method(MEM)/Rietveld Analysis and first principles calculation. The electron density map shows that the covalent bonding of (Mn, M)-O of o-LiMn1-xMxO2 is stronger than that of o-LiMnO2. Next, we calculated the electron density of o-LiMn1-xMxO2 (M=Mn, Co, Ni, Zn) using the first principles calculation by FLAPW method. The covalent bonding of Mn-O and M-O of each o-LiMn1-xMxO2 is stronger than that of o-LiMnO2 by substitution of Mn with M.

Enhancement of the rate capability and cyclability of an Mg–C composite electrode for Li secondary batteries

An Mg–C composite, prepared by high energy mechanical milling, was investigated as an anode material for lithium-ion batteries. Electrochemical tests demonstrated that the first charge and discharge capacities were 1810 and 1433 mA h g −1, respectively, with a coulombic efficiency for the first cycle of 80%. Ex situ XRD analyses combined with a differential capacity plot of the Mg–C composite electrode showed the phase changes during the electrochemical Li–Mg alloying/dealloying reaction. Significantly enhanced rate capability and reversibility of the electrochemical reaction of Mg with lithium were observed and the improvement in the electrochemical properties of the composite electrode was attributed to the high energy mechanical milling of Mg with carbon on the surface of the Mg–C composite.

Low‐Temperature Synthesis of LixMn0.67Ni0.33O2 (0.2 < x < 0.33) Nanowires with a Hexagonal Layered Structure

Hexagonal layered lithium nickel manganate nanowires (see Figure) are prepared in large amounts through a simple soft-chemical redox reaction of a LiMn0.5Ni0.5O2 precursor. The structure and chemical composition of the nanowires can be tailored by tuning the reaction conditions. The resultant multicomponent nanowires show promise as a cathode material for Li secondary batteries.

Using PANI–PPDA/Au composite films as cathode of lithium secondary battery

Polyaniline (PANI)–1,4- para-phenylenediamine (PPDA) composite films were prepared on Au plate with the cyclic voltammetry (CV) method and used as the cathode of lithium secondary battery. The polymerization rate increased with increasing the concentration of PPDA in the solution. When the PANI–PPDA/Au was prepared with cycle number of 10 in the presence of 0.1 M aniline and 10 mM PPDA and used as the cathode of Li secondary battery, the maximum discharge capacity was obtained to be 103.2 mAh g −1 and the average fading rate was 0.147 mAh g −1 cycle −1 at charge/discharge rate of 0.4 mA.

Nanoparticles of tin confined in microporous carbon matrices as anode materials for Li batteries

A new approach has been developed for the preparation of anodes for rechargeable Li batteries based on nanoparticles of tin as an alloying medium embedded in microporous (pore diameter, <2 nm) carbon matrices. It is assumed that if tin particles are confined within the carbon micropores, they may exhibit better cyclability upon alloying–dealloying with lithium, since the detrimental effect of the volume expansion of Li x Sn upon alloying can be avoided. A volatile compound of tin, SnCl 4, was physisorbed to the carbon surface. This was followed by hydrolysis to SnO 2 and by high temperature degassing, which completed the hydrolysis and removed any volatile residue. Using SEM, EDAX and XRD analyses, we could show that we indeed obtained porous carbon, with particles of tin oxide within the microporous system. These matrices were tested as negative electrodes for secondary Li batteries. At this early stage of the study, a reversible capacity as high as 305 mAh g −1 was obtained (carbon and Sn), which means that the capacity of the Li–tin alloying was not to far from its theoretical value. The next steps in this study are: 1. Increasing the amount of tin that can be included in the carbon matrices. 2. The development of the preceding reduction process of SnO 2 to Sn, which will reduce pronouncedly the initial irreversible capacity.

A study on the charge–discharge mechanism of Co 3O 4 as an anode for the Li ion secondary battery

Co 3O 4 has shown acceptable electrochemical properties as the anode material of Li secondary batteries. In detail, its capacity reached about 700 mAh/g, twice as high as graphite, and 93.4% of initial capacity was retained after 100 cycles. EIS (electrochemical impedance spectroscopy) analyses revealed that after the 1st cycle, the insertion or extraction of Li ions in Co 3O 4 can occur homogeneously and reversibly (randless-like behavior, homogeneous mixture: Co + Li 2O (in the state of Li insertion), Co 3O 4 (in the state of Li extraction)). In fact, the coulombic efficiency of Co 3O 4 was almost 100% except for the 1st cycle. According to P. Poizot's research on several kinds of transition metal oxides, such as Co 3O 4, CoO, NiO, etc., a small Li 2O particle size and catalytic activity of the transition metal are expected to decrease the binding energy of Li 2O tremendously. As a result, Li 2O should be easy to decompose, and transition metal oxides should be able to charge or discharge reversibly by formation or decomposition of Li 2O. However, this assumption has never been confirmed by experimental results. In our results, the CV (cyclic voltammogram) of a Li 2O–Co mixture shows much larger oxidation and reduction peaks than that of Li 2O. Based on XRD analyses, oxidation and reduction in the CV of Li 2O correspond, respectively, to the decomposition and formation of Li 2O. So, it can be asserted that Co addition to Li 2O facilitates decomposition and formation processes in Li 2O and that the catalytic effect of the transition metal must be one of the main causes that make Li 2O form or decompose repeatedly.

OS7-08 Li二次電池を用いた電力貯蔵システムの開発(OS7 高温・高效率・発電・エネルギー貯蔵技術)

Mitsubishi Heavy Industries and Kyushu Electric have developed Li secondary battery power storage systems for applying to factories, stores and homes. The power storage system which we are evaluating now, consists of series-connected 270Wh-class cells by which each cell has 160Wh/kg of energy density, battery protection circuits and a bi-directional inverter, and has attained 86% or more of high energy efficiency. Our target of system life is 3,500 cycles (namely, ten years), and the system operating normally during more than one year and a half. We report main properties of cells and system and field test performance in this paper.

Multilayered Sn–Zn–Cu alloy thin-film as negative electrodes for advanced lithium-ion batteries

Sn-based alloy compounds have been considered as possible alternatives for carbon in lithium-ion batteries and attract great attentions because of their large electrochemical capacity compared with that of carbon. In this work, a multilayered Sn–Zn/Zn/Cu alloy thin-film electrode has been prepared by electroplating method. The structure and performance of the electrode before and after heat treatment have been investigated. It is found that Cu 6Sn 5 phase and multilayered structure in electrode are formed after heat treatment. This optimized structure of the heat-treated electrode results in enhanced cycle life. The capacity of the electrode is over 320 mA h g −1 after 100 cycles; though it is 83 mA h g −1 after 20 cycles for as-plated electrode. The Sn–Cu and Zn–Cu alloy formed a network in the electrode is considered to strengthen the electrode and reduce the effect of volume expansion and phase transition during cycling. Experimental results also reveal that lower cut-off potential (0.05 V) for charging and higher one (1.2 V) for discharging result in long cycle life and high discharge capacity, respectively. The reason of capacity decay of the heat-treatment electrode during cycling has also been investigated. All these results show that the electroplated Sn–Zn-based alloy film on Cu foil would be a promising negative material with high capacity and low cost for Li secondary batteries.

Cr 3+ modified LiMn 2O 4 spinel intercalation cathodes through oxalic acid assisted sol–gel method for lithium rechargeable batteries

To improve the cycle performance of eco-friendly and cost-effective spinel LiMn 2O 4 as the cathode of 4 V class Li secondary batteries, the spinel phase LiCr x Mn 2 − x O 4 ( x = 0.01–0.20) was synthesized by soft chemistry method using oxalic acid as chelating agent. The present technique results in better homogeneity, good surface morphology, shorter heat treatment time, sub-micron sized particles, good agglomeration and better crystallinity. Electrochemical studies were monitored in the potential range of 3–4.5 V. The present paper reveals that chromium substituted manganese spinel improves the structural stability of the parent material.

Thermodynamic Stability and Cathode Performance of LiMn&lt;sub&gt;2-x&lt;/sub&gt;Ni&lt;sub&gt;x&lt;/sub&gt;O&lt;sub&gt;4&lt;/sub&gt; as an Active Material for Li Secondary Battery

Thermodynamic Stability and Cathode Performance of LiMn&lt;sub&gt;2-x&lt;/sub&gt;Ni&lt;sub&gt;x&lt;/sub&gt;O&lt;sub&gt;4&lt;/sub&gt; as an Active Material for Li Secondary Battery

Fabrication of Three-dimensionally Ordered Macroporous Electrode Materials by Using PMMA Template

Three-dimensionally ordered macroporous (3DOM) structures of the <TEX>$LiCoO_2$</TEX> electrode materials for Li secondary batteries were fabricated by using the close-packed arrays of PMMA spheres served as templates. In order to successfully fabricate the cathode materials with highly ordered array form, the metal citrates were applied to new precursors. The precursor/template composites were prepared by the infiltration with metal citrate precursors into the voids of template. By removing the PMMA templates, then, the inverse opal structures with the uniform pores of narrow size distribution were resulted. It was confirmed that the 3DOM <TEX>$LiCoO_2$</TEX> material is to take a single phase of rocksalt (R3m) structure. In addition, 3DOM <TEX>$LiNiO_2$</TEX> and <TEX>$LiMn_{2}O_4$</TEX> cathode materials were fabricated using an identical preparation procedure. Also, the morphology of the 3DOM cathode materials calcined at <TEX>$500^{\circ}C\;to\;700^{\circ}C$</TEX> was observed by scanning electron microscope.