An Electrochemical Impedance Spectroscopic Study of the Electronic and Ionic Transport Properties of Spinet LiMn2O4

Electrochemical impedance spectra (EIS) for lithium ion insertion and deinsertion in spinel LiMn2O4 were obtained at different potentials and different temperatures during initial charge-discharge cycle. The results revealed that, at intermediate degrees of intercalation, three semicircles appeared in the Nyquist diagram. This new phenomenon has been investigated through EIS measurements as a function of temperature. It has found that the high frequency semicircle and the middle to high frequency semicircle begin to overlap each other above 20 degrees C, which indicates that the high frequency compressed semicircle commonly obtained at room temperature in the literature may consist of two semicircles. This signifies that the effects of the electronic and ionic transport properties of lithium intercalation materials clearly appear as separate features in the EIS spectra at low temperatures. A new equivalent circuit that includes elements related to the electronic and ionic transport, in addition to the charge transfer process, is proposed to simulate the experimental EIS data. The change of kinetic parameters for lithium ion insertion and deinsertion in spinel LiMn2O4 as a function of potential in the first charge-discharge cycle is discussed in detail, and a modified model is proposed to explain the impedance response of the insertion materials for lithium ion batteries.National Basic Research Program of China [2009CB220102

Impedance studies of spinel LiMn2O4 electrode/electrolyte interfaces

The formation process of solid electrolyte interphase(SEI) film on spinet LiMn2O4 electrode surface was studied by electrochemical impedance spectroscopy(EIS) during the initial storage in 1 mol/L LiPF6-EC:DMC:DEC electrolyte and in the subsequent first charge-discharge cycle. It has been demonstrated that the SEI film thickness increased with the increase of storage time and spontaneous reactions occurring between spinet LiMn2O4 electrode and electrolyte can be prevented by the SEI film. In the first charge-discharge cycle succeeding the storage, the electrolyte oxidation coupled with Li-ion insertion is evidenced as the main origin to increase the resistance of SEI film. The results also confirm that the variations of the charge transfer resistance(R-ct) with the electrode potential(E) can be well described using a classical equation

Influence of Temperature on the Performance of a Graphite Electrode

The first lithiation of a graphite electrode in 1 mol . L-1 LiPF6-EC (ethylene carbonate): DEC (diethyl carbonate): DMC(dimethyl carbonate) electrolyte at 25 and 60 degrees C, and in 1 mol . L-1 LiPF6-EC:DEC:DMC+5%VC (vinylene carbonate) electrolyte at 60 degrees C were investigated by electrochemical impedance spectroscopy (EIS) combined with cyclic voltammetry (CV). It was found that deterioration of the graphite electrode's electrochemical performance was mainly caused by the unstable solid electrolyte interphase (SEI) film on the electrode's surface in 1 mol . L-1 LiPF6-EC:DEC:DMC electrolyte at 60 degrees C. However, the use of VC as an additive to the above electrolyte significantly improved the electrochemical performance of the graphite electrode, which was attributed to an improvement in the stability of the SEI film that formed on the graphite electrode's surface

Influence of Resveratrol on Performance of Long-Term Storage’s Lithium-Ion Battery Electrolyte

锂离子电池电解液从制造完成到使用,一般都会经历灌装、运输和贮存的过程,了解长期贮存过程对锂离子电池电解液性能的影响,对锂离子电池的生产具有一定的理论指导意义。本文运用电化学阻抗谱(EIS)测试并结合循环伏安法(CV)测试、充放电测试、扫描电子显微镜(SEM)等研究了1 mol·L-1 LiPF6-EC:EMC基础电解液中添加不同浓度白藜芦醇(RES)时,在长期贮存过程中对石墨电极性能的影响及机制。研究结果表明,新鲜的基础电解液在经历6个月的贮存后,石墨电极在其中无论是可逆循环容量还是循环稳定性(容量保持率)均出现大幅度的下降。这主要是由于在经历6个月贮存后的基础电解液中,石墨电极表面形成的 SEI 膜较厚,进而导致锂离子嵌入过程的不稳定造成的。在基础电解液中添加不同浓度的白藜芦醇均能有效抑制电解液长期贮存造成的石墨电极在其中电化学性能的下降,当基础电解液中含有200 ppm白藜芦醇经历6个月贮存后,石墨电极无论是可逆容量还是循环性能稳定性甚至优异于在新鲜的电解液中。Electrolyte of lithium-ion battery usually goes through processes of filling, transportation and storage from the completion of manufacture to the use. Understanding the influence of long-term storage process on performance of lithium-ion battery electrolyte is of theoretical significance for production of lithium-ion battery. Scanning electron microscope (SEM) images showed that the solid electrolyte interface (SEI) film formed on the surface of the graphite electrode was thicker in the base electrolyte after 6 months of storage. The charge/discharge test results showed that the reversible cycle capacity and cycle stability (capacity retention rate) of graphite electrode decreased significantly after 6 months of storage. This might be due to the thicker SEI film formed on the surface of the graphite electrode, which in turn led to the instability of the lithium-ion intercalation process. When the base electrolyte containing 200 ppm resveratrol was stored for 6 months, the reversible capacity and cycle performance stability of the graphite electrode were even better than those in fresh base electrolyte. The results of electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) idicated that adding 200 ppm resveratrol to the base electrolyte could effectively suppress the decline in the electrochemical performance of the graphite electrode caused by long-term storage of the base electrolyte.国家自然科学基金项目(U1730136);中央高校基本科研业务费(2017XKQY062)通讯作者:庄全超E-mail:[email protected]:Quan-ChaoZhuangE-mail:[email protected]中国矿业大学材料与物理学院,江苏 徐州 221116Lithium ion battery lab, School of Materials & Physics, China University of Mining & Technology, Xuzhou 221116, Jiangsu, Chin

Three-dimensional porous Cu6Sn5 alloy anodes for lithium-ion batteries

Three-dimensional porous Cu6Sn5 alloy electrodes were prepared by electroplating using copper foam as current collector. The micro-holes and small islands on surface of the Cu6Sn5 alloy increased largely the surface area of the electrode, and improved significantly the ability of the electrode in buffering the volume change in process of charge/discharge when the Cu6Sn5 alloy was employed as anode in a lithium-ion battery. Galvonostatic charging/ discharging results demonstrated that the initial discharge (lithiation) and charge (delithiation) specific capacities of the Cu6Sn5 alloy electrode were 620 mAh center dot g(-1) and 560 mAh center dot g(-1), respectively. It demonstrated that the Cu6Sn5 alloy electrode exhibited a large initial coulomb efficiency (90.3%) and good capacity retention. SEM (scanning electron microscope) results illustrated that the Cu6Sn5 alloy deposited on copper foam substrate was more stable than that on a conventional copper substrate, and displayed no obvious exfoliation after 50 charge/discharge cycles

Bottom-up synthesis of nitrogen-doped graphene sheets for ultrafast lithium storage

National Natural Science Foundation of China for Innovative Research Group [51221462]; Jiangsu Ordinary University Graduate Innovative Research Programs [CXZZ12_0943, CXZZ13_0952]; Jiangsu Planned Projects for Postdoctoral Research Funds [1201030C]; Priority Academic Program Development of Jiangsu Higher Education InstitutionsA facile bottom-up strategy was developed to fabricate nitrogen-doped graphene sheets (NGSs) from glucose using a sacrificial template synthesis method. Three main types of nitrogen dopants (pyridinic, pyrrolic and graphitic nitrogens) were introduced into the graphene lattice, and an inimitable microporous structure of NGS with a high specific surface area of 504 m(2) g(-1) was obtained. Particularly, with hybrid features of lithium ion batteries and Faradic capacitors at a low rate and features of Faradic capacitors at a high rate, the NGS presents a superior lithium storage performance. During electrochemical cycling, the NGS electrode afforded an enhanced reversible capacity of 832.4 mA h g(-1) at 100 mA g(-1) and an excellent cycling stability of 750.7 mA h g(-1) after 108 discharge-charge cycles. Furthermore, an astonishing rate capability of 333 mA h g(-1) at 10 000 mA g(-1) and a high rate cycle performance of 280.6 mA h g(-1) even after 1200 cycles were also achieved, highlighting the significance of nitrogen doping on the maximum utilization of graphene-based materials for advanced lithium storage

Effects of temperature on the intercalation-deintercalation process of lithium ion in LiCOO2

The temperature dependent properties of the impedance spectral characters, the electronic resistance, the resistances of the SEI (solid electrolyte interphase) film as well as the charge transfer reaction of the LiCoO2 electrode in 1 mol/L LiPF6-EC (ethylene carbonate); DEC (diethyl carbonate):DMC (dimethyl carbonate) and I mol/L LiPF6-PC (propylene carbonate):DMC+5% VC (vinylene carbonate) electrolyte solutions were studied and reported. The temperature was varied from 0 to 30 degrees C. The studies of electrochemical impedance spectroscopy (EIS) revealed that, the common EIS features' of the LiCoO2 electrode in the I mol/L LiPF6-EC:DEC:DMC and I mol/L LiPF6-PC:DMC+5% VC electrolyte solutions were related to the temperature, and a straight line reflecting solid state Li ion diffusion in the bulk of active mass appeared at 10 and 20 V, respectively. In I mol/L LiPF6-EC:DEC:DMC and I mol/L LiPF6-PC:DMC+5% VC electrolyte solutions, the energy barriers for the ion jump relating to migration of lithium ions through the SEI film of the LiCoO2 electrode were determined to be 37.74 and 26.55 kJ/mol, the thermal active energy of the electronic conductivities to be 39.08 and 53.81 kJ/mol, and the intercalation-deintercalation reaction active energies to be 68.97 and 73.73 kJ/mol, respectively

Preparation and capacity fading mechanism of tin thin film as anode of lithium-ion battery

Tin thin film coated on Cu substrate as anode of lithium-ion battery was prepared by electroplating. Its structure and properties were characterized and studied by X-ray diffration, scanning electron microscopy, cyclic voltammetry, charging/discharging test and AC impedence method. XRD patterns indicate that the tin thin film exhibits a structure of tetragonal crystal. The first discharge and charge capacities of the tin thin film electrode were determined to be 709 and 561 mAh(.)g(-1), respectively. Cyclic voltammetric results illustrated that multi-phase changes occurred during the lithiation and delithiation. Electrochemical impedance spectroscopy (EIS) results indicated that SEI film was begun to form on the surface of tin thin film electrode at 1.2 V, and then break down below 0.4 V because of large volume expansion. SEM investigations revealed that the tin thin film electrode appeared serious cracks after 30 charging and discharging cycles