Electrode For Lithium Secondary Batteries Research Articles

Electrochemical Properties of Carbon-Coated FeS<sub>2</sub> as a Positive Electrode for Lithium Secondary Batteries

The electrochemical properties of carbon-coated FeS2 were investigated as a positive electrode material for lithium secondary batteries. The carbon-coated FeS2 powders were synthesized by ball-milling using polyaniline as the carbon source. The particles in the carbon-coated FeS2 samples were smaller than those in the pristine FeS2 samples. The electrochemical performance, including capacity, of these batteries was improved by carbon-coating by ball-milling. However, the initial coulombic efficiency decreased because of the reduction of the oxidized products on FeS2 surface. The reduction in particle size provides a larger contact area for the electrolyte. Larger quantities of oxidation products were formed by the reduction of FeS2 in the presence of air and water after carbon-coating. Therefore, the poor initial coulombic efficiencies of carbon-coated FeS2 electrodes were caused by the reduction of the oxidized products on the FeS2 surface.

Effects of Poly(Vinylidene Fluoride) Content on Electrochemical Properties of a Graphite Negative Electrode in Lithium Secondary Batteries

We investigated the effect of poly (vinylidene fluoride) (PVdF) binder content on graphite negative electrodes for lithium secondary batteries. The negative electrode was prepared by artificial graphite powder and poly (vinylidene fluoride) binder. Scanning electron microscopy, charge/discharge test, and electrochemical impedance microscopy were conducted. As a result of electrochemical analysis, we confirmed that the electrochemical behavior varied according to the PVdF content (5, 10, 15, 50, and 90 wt%). In addition, charge/discharge test and electrochemical impedance microscopy results showed the high irreversible capacities and resistances, observed for electrodes containing PVdF contents of 50 and 90 wt%. This demonstrated that decomposition of the binder was generated during electrochemical analysis.

Synthesis of New Type Core–Shell Li[Li0.21(Ni0.20Co0.16Mn0.58)0.8(Ni0.2Mn0.2)0.2]O2 Spherical Particles as a Positive Electrode for Lithium Secondary Batteries by Coprecipitation

Abstract Microscale core–shell-structured Li[Li0.21(Ni0.20Co0.16Mn0.58)0.8(Ni0.2Mn0.2)0.2]O2 powders were prepared by a coprecipitation method. To protect the Li[Li0.2(Ni0.14Co0.14Mn0.52)]O2 core material from structural instability at high voltage, a Li[Li0.2(Ni0.4Mn0.4)]O2 shell, which provides structural and thermal stability, was used to encapsulate the core. Spherical morphologies with monodispersed powders were observed in the cross-sectional images obtained by scanning electron microscopy (SEM). To the best of our knowledge, this is the first report of the synthesis of a Mn-rich core–shell.

パルス電解法で作製したリチウム二次電池用Ni-Sn合金めっき膜負極の組成が充放電特性に及ぼす影響

パルス電解法で作製したリチウム二次電池用Ni-Sn合金めっき膜負極の組成が充放電特性に及ぼす影響

Influence of the binder types on the electrochemical characteristics of tin nanoparticle negative electrode for lithium secondary batteries

The influence of the binder types on the electrochemical characteristics of the tin nanoparticle negative electrode for lithium secondary batteries has been investigated using cyclic voltammetry, charge–discharge test, electrochemical impedance spectroscopy, scanning electron microscope, and transmission electron microscope. The results show that the initial capacity and the cyclic retention of the tin electrode using carboxymethyl cellulose as a binder are better than those of using polyvinylidene fluoride as a binder. Moreover, the cycle performance is further enhanced by the addition of acetylene black into the electrodes using the carboxymethyl cellulose binder. The good capacity retention in the subsequent cycles may be attributed to the formed branch-like structure on the surface of the tin nanoparticles during cycling.

Fabrication of binder-free SnO2 nanoparticle electrode for lithium secondary batteries by electrophoretic deposition method

We tried fabricating a binder-free co-deposited film electrode consisting of SnO2 nanoparticles (nano-SnO2) and acetylene black (AB) particles by an electrophoretic deposition (EPD) method. By cathodically depositing on a copper foil when employing an acetone bath, the co-deposited film consisting of nano-SnO2 and AB could be fabricated. SEM/EDX indicated that the roughness of the co-deposited film was approximately 1μm and the nano-SnO2 particles and the AB particles were uniformly deposited. The weight percent of the nano-SnO2 in the co-deposited film could be controlled in the range from 87.80 to 93.64wt.%. The galvanostatic charge–discharge tests indicated that the discharge capacity and the charge–discharge efficiency of the co-deposited film (nano-SnO2:AB=93.64:6.36wt.%) at the 1st cycle were 887mAhg−1 and 48.8% at 0.1C, respectively; the discharge capacity after the 50th cycle was 504mAhg−1. It has been considered that the reverse reaction of the conversion reaction would occur during discharging because the discharge capacity at the 1st cycle was higher than the theoretical capacity of SnO2 (783mAhg−1). Thus it has been clarified that the binder-free co-deposited film could operate as a negative electrode for lithium secondary batteries.

결정화도에 따른 Li3V2(PO4)3음극의 전기화학적 특성

열처리 온도를 <TEX>$600^{\circ}C$</TEX>와 <TEX>$800^{\circ}C$</TEX>로 다르게 하여 비정질 및 결정질구조의 탄소를 포함하는 <TEX>$Li_3V_2(PO_4)_3/C$</TEX>분말을 각각 합성하였으며, 결정성에 따른 리튬 이차전지용 음극으로의 특성을 비교하였다. 결정질 <TEX>$Li_3V_2(PO_4)_3/C$</TEX>은 추가반응에 의하여 리튬이 저장되기 때문에 260 mAh <TEX>$g^{-1}$</TEX>의 제한된 용량만을 지니고 있음에 비하여, 비정질 <TEX>$Li_3V_2(PO_4)_3/C$</TEX>는 3가의 바나듐이 금속상태에 근접할 정도로 가역적으로 반응되어 460 mAh <TEX>$g^{-1}$</TEX>의 큰가역용량을 발현함을 확인하였다. 이는 비정질 구조에서 기인하는 특성으로 유연한 구조로 인한 새로운 리튬의 저장공간이 확보되는 것 때문이라 할 수 있다. 또한, 비정질 <TEX>$Li_3V_2(PO_4)_3/C$</TEX>는 비정질 구조에 기인하는 선형적인 충방전 곡선을 지니고 있어 정확한 충전심도의 예측이 용이할 뿐만 아니라, 결함구조에서 유발된 리튬이온의 향상된 확산성으로 인하여 우수한 속도 특성도 나타내고 있다. <TEX>$Li_3V_2(PO_4)_3$</TEX>/carbon composite materials are synthesized from a sucrose-containing precursor. Amorphous <TEX>$Li_3V_2(PO_4)_3/C$</TEX> (a-LVP/C) and crystalline <TEX>$Li_3V_2(PO_4)_3/C$</TEX> (c-LVP/C) are obtained by calcining at <TEX>$600^{\circ}C$</TEX> and <TEX>$800^{\circ}C$</TEX>, respectrively, and electrochemical performance as the negative electrode for lithium secondary batteries is compared for two samples. The a-LVP electrode shows much larger reversible capacity than c-LVP, which is ascribed to the spatial <TEX>$Li^+$</TEX> channels and flexible structure of amorphous material. In addition, this electrode shows an excellent rate capability, which can be accounted for by the facilitated <TEX>$Li^+$</TEX> diffusion through the defect sites. The sloping voltage profile is another advantageous feature for easy SOC (state of charge) estimation.

パルス電解法を用いるリチウムイオン二次電池用Ni-Sn合金めっき膜負極の作製

パルス電解法を用いるリチウムイオン二次電池用Ni-Sn合金めっき膜負極の作製

Synthesis and electrochemical characterization of 2D nanostructured Li4Ti5O12 with lithium electrode functionality

Two-dimensional (2D) Li4Ti5O12 nanosheets with cubic spinel structure are synthesized via a lithiation process of exfoliated titanate 2D nanosheets and the subsequent heat-treatment at elevated temperatures. According to powder X-ray diffraction and field emission-scanning electron microscopy analysis, the obtained lithium titanium oxides show well-developed Bragg reflections of cubic spinel-structured Li4Ti5O12 phase and highly anisotropic 2D plate-like morphology. Ti K-edge X-ray absorption near-edge structure analysis reveals the stabilization of tetravalent titanium ions in the cubic spinel lattice of Li4Ti5O12. The 2D nanostructured Li4Ti5O12 materials display the electrochemical functionality as negative electrode for lithium secondary batteries. The most promising electrode performance is achieved by the heat-treatment of the lithiated titanate at 600°C, highlighting the importance of heating temperature in optimizing the electrochemical property of the resulting materials.

Preparation of Co–Sn alloy film as negative electrode for lithium secondary batteries by pulse electrodeposition method

In order to easily and simply improve the cyclability of the Sn film negative electrode, we selected Co as a matrix metal and tried to prepare the Co–Sn alloy film negative electrode by a pulse electrodeposition method. The surface morphology of the deposit was almost the same as that of the Sn film, although aggregation partially occurred. The content rate of Co and Sn in the deposit was almost the same as the composition percentage in the electrodeposition bath. X-ray diffraction measurement showed that the deposited film could be assigned to a metastable Co–Sn alloy, while the co-deposition of crystalline Sn was not observed. The galvanostatic charge–discharge tests indicated that the discharge capacity and the charge–discharge efficiency of the Co 30.5Sn 69.5 alloy film electrode at the 1st cycle were 529.2 mAh g −1 and 87.9%, respectively. Furthermore, the film electrode showed a good cyclability and discharge capacity of 470.5–617.5 mAh g −1 during 50 cyclings. Alloying Sn with inactive Co could effectively improve the cyclability of the Sn film electrode prepared by the pulse electrodeposition method.

Electrochemical Characteristics of SnO2 Nanoparticle Prepared by Liquid Phase Deposition Method as Negative Electrode for Lithium Secondary Batteries

not Available.

Thermoelectrochemically Activated MoO2 Powder Electrode for Lithium Secondary Batteries

The high temperature lithiation behavior of the electrode is examined, which is lithiated by one-electron reduction (by addition reaction) at room temperature. At elevated temperatures, this electrode is lithiated with four-electron reduction by addition and continued conversion reaction. As a result of four-electron reduction, the initial crystalline phase is decomposed into a nanosized mixture of metallic Mo and , which is in turn converted to nanosized upon forthcoming delithiation. An interesting feature here is that as-generated nanosized is now fully lithiated up to four-electron reduction even at room temperature. This phenomenon is named “thermoelectrochemical activation” because the extension from one- to four-electron reduction is achieved by a simple charge–discharge cycling made at elevated temperatures. The thermoelectrochemically activated electrode delivers a reversible specific capacity that is close to the theoretical four-electron capacity with an excellent cycle performance at room temperature.

Electrochemical characteristics of Sn film prepared by pulse electrodeposition method as negative electrode for lithium secondary batteries

In order to improve the cyclability of Sn negative electrode, we tried preparing the Sn film negative electrode by a pulse electrodeposition. Based on the SEM observations, the crystal grains of the Sn film after the pulse electrodeposition were comparatively homogeneous and their grain size was ca. 1 μm. The discharge capacity and the charge–discharge efficiency at the 1st cycle were 679.3 mAh g −1 and 93.0%, respectively. The charge–discharge tests indicated that the initial electrochemical characteristic of Sn film electrode prepared by a pulse electrodeposition was much better than that of the Sn film electrode prepared by a constant current electrodeposition. The GD-OES profile suggested that Li + ions were easily extracted during the discharge reaction. In addition, it was found that no exfoliation of the film was observed after the 1st discharge though the cracking in the film was observed after the 1st discharge. Consequently, the Sn film electrode prepared by a pulse electrodeposition exhibited a better cyclability for the initial 10 cycles compared to the Sn film electrode prepared by a constant current electrodeposition. By reducing the particle size and repressing the morphological change, the initial electrochemical characteristics were considerably improved.

Electrochemical Characteristics of Co-Sn Alloy Film Prepared by Pulse Electrodeposition Method as Negative Electrode for Lithium Secondary Batteries

not Available.

Carbon nanotubes (CNTs) as a buffer layer in silicon/CNTs composite electrodes for lithium secondary batteries

A core/shell type silicon/carbon nanotubes (Si/CNTs) composite is prepared and its anodic performance in lithium secondary batteries is examined. For the growth of CNTs, a Ni catalyst is loaded on a Si surface by electroless deposition. The growth is performed by chemical vapour deposition at 600 °C using C 2H 2/H 2 but is successful only on smaller and thinner Ni deposits. This is probably due to an easier transformation to small droplets that initiate the growth reaction. The anodic performance of a Si/CNTs composite electrode is superior to that observed with bare Si and Si/CNTs mixed electrodes. This beneficial feature is ascribed to the conductive buffering role of the CNTs layer. It is likely that the void space and the flexible characteristics in the CNTs buffer layer on the Si surface allow volume expansion of the Si core without severe electrode swelling. Because of this, the electric conductive network made among Si particles, carbon network and current-collector is well maintained, which reduces the charge-transfer resistance.

Application to Negative Electrode for Lithium Secondary Batteries of Electroplated Aluminum Electrode

Application to Negative Electrode for Lithium Secondary Batteries of Electroplated Aluminum Electrode

Electrochemical Properties and Microstructure of Tin Base Thin Film Electrode for Lithium Secondary Batteries

AbstractCu/Sn alloy electrode, as an anode for Li ion secondary batteries, was fabricated by annealing of Sn thin film electroplated on copper thin foil. The structure of Cu/Sn alloy electrode was determined using XRD, SEM and TEM. The thin film was consisted of Cu6Sn5, Cu3Sn and so on, the major component was a few ten nanometer sized Cu6Sn5 grains and the minor (Cu3Sn and β-(Cu,Sn)) was dispersed among the Cu6Sn5 grains. The electrochemical properties of Cu6Sn5 thin film were evaluated in coin type half-cell, which was configured with Cu6Sn5, thin film electrode, Li metal electrode and typical 1 mol LiPF6 in EC:DMC (1:1) electrolyte. Annealed Cu/Sn electrode took and released Li ions well during Li insertion and de-insertion. Cycle performance of annealed Cu/Sn electrode was better than that of as-deposited Sn electrode, which was caused by topotactic reaction of Cu6Sn5and composite structure of Cu/Sn alloys.

Failure Modes of Silicon Powder Negative Electrode in Lithium Secondary Batteries

Si composite negative electrodes for lithium secondary batteries degrade in the dealloying period with an abrupt increase in internal resistance that is caused by a breakdown of conductive network made between Si and carbon particles. This results from a volume contraction of Si particles after expansion in the previous alloying process. Due to the large internal resistance, the dealloying reaction is not completed while Si remains as a lithiated state. The anodic performance is greatly improved either by applying a pressure on the cells or loading a larger amount of conductive carbon in the composite electrodes.

Advanced Structures in Electrodeposited Tin Base Negative Electrodes for Lithium Secondary Batteries

Tin anodes deposited electrochemically on a copper foil current collector are studied to develop a next-generation lithium-ion battery with higher energy density. Better cycle performance through ten initial cycles under full charge and discharge conditions was attained by annealing tin electrodeposited on a rough surface copper foil. The annealing process was found to change the main active material from Sn to with some minor compounds. Furthermore, a microcolumnar structure of the active material portion was found to be self-organized in accordance with the surface profile of the foil during the first charge-discharge cycle. Advantages of these structural features are discussed in terms of the initial charge and discharge performance, including specific capacity and coulombic efficiency measured by using a three-electrode cell. © 2003 The Electrochemical Society. All rights reserved.

The effects of oxygen flow rate and anion doping on the performance of the LiNio2 electrode for lithium secondary batteries

This work presents the effects of O2 flow rate and S-doping on structural and electrochemical properties of LiNiO2. Layered LiNiO2 were prepared using a sol-gel method. It was found that oxygen plays an important role in the crystallization of layered LiNiO2. The deficiency of oxygen in the crystallization process induced the inclusions of impurities and cubic rock-salt structure in LiNiO2 powders. For LiNiO2 prepared at high O2 flow rates, the electrode delivered high initial discharge capacity with a relatively good retention rate. S-doped LiNiO2 not only stabilized the structural integrity of the electrode material, but also increased the electrode performance.