Electrochemical behavior of a lithium-pre-doped carbon-coated silicon monoxide anode cell

Owing to high energy density, silicon monoxide is an attractive anode material for lithium ion secondary batteries. However, its huge irreversible capacity during initial cycling makes it difficult to use in lithium secondary batteries. A new technique for lithiation in the silicon monoxide has been developed using Li powders. The electrochemical behavior of the lithium powder pre-doped carbon-coated silicon monoxide (OG) anode cell was studied. The cells showed reduced initial irreversibility and enhanced coulombic efficiency. The behavior of the cells was analyzed by X-ray diffraction and electrochemical testing methods.     

High performance silicon carbon composite anode materials for lithium ion batteries

Silicon and silicon containing compounds are attractive anode materials for lithium batteries because of their low electrochemical potential vs. lithium and high theoretical capacities. In this work the relationship between the electrochemical performance of silicon powders and their particle sizes was studied. It is found that the material with nano particle sizes gives the best performance. New silicon/carbon composite anode materials were synthesized and their structures and electrochemical performance were investigated. The results of these studies are reported in this paper.     

MnO/C core-shell nanorods as high capacity anode materials for lithium-ion batteries

MnO/C core-shell nanorods were synthesized by an in situ reduction method using MnO₂ nanowires as precursor and block copolymer F127 as carbon source. Field emission scanning electron microscopy and transmission electron microscopy analysis indicated that a thin carbon layer was coated on the surfaces of the individual MnO nanorods. The electrochemical properties were evaluated by cyclic voltammetry and galvanostatic charge-discharge techniques. The as-prepared MnO/C core-shell nanorods exhibit a higher specific capacity than MnO microparticles as anode material for lithium ion batteries.     

Structural changes in a commercial lithium-ion battery during electrochemical cycling: An in situ neutron diffraction study

The structural response to electrochemical cycling of the components within a commercial Li-ion battery (LiCoO₂ cathode, graphite anode) is shown through in situ neutron diffraction. Lithuim insertion and extraction is observed in both the cathode and anode. In particular, reversible Li incorporation into both layered and spinel-type LiCoO₂ phases that comprise the cathode is shown and each of these components features several phase transitions attributed to Li content and correlated with the state-of-charge of the battery. At the anode, a constant cell voltage correlates with a stable lithiated graphite phase. Transformation to de-lithiated graphite at the discharged state is characterised by a sharp decrease in both structural cell parameters and cell voltage. In the charged state, a two-phase region exists and is composed of the lithiated graphite phase and about 64% LiC₆. It is postulated that trapping Li in the solid|electrolyte interface layer results in minimal structural changes to the lithiated graphite anode across the constant cell voltage regions of the electrochemical cycle.     

Electrochemical behavior of a silicon monoxide and Li-powder double layer anode cell

A new technique for synthesizing double layer anodes with silicon monoxide and Li powder has been developed to reduce the initial capacity loss of silicon monoxide anodes. Double layer anode (DLA) cells are fabricated using Li emulsified powders on a Cu foil and silicon monoxide powders on a Cu mesh collector and their electrochemical behaviors are studied. The DLA cells show reduced initial irreversibility and enhanced coulombic efficiency. The coulombic efficiency of the first cycle of the DLA cell is over 100% and its capacity remains as 700 mAh g⁻¹ up to 20 cycles. SEM observation shows that the Li-powder layer in DLA compensated for the initial irreversible loss and vanished after several cycles.     

Electrochemical behavior of Al in a non-aqueous alkyl carbonate solution containing LiBOB salt

Aluminum was studied as a current collector for rechargeable lithium batteries to understand electrochemical and passivation behavior. Electrochemical polarization tests, in situ scratch polarization tests and time-of-flight secondary ion mass spectroscopy (ToF-SIMS) analysis in lithium bis-oxalato borate (LiBOB)-containing alkyl carbonate solution were conducted. The Al foil did not follow the alloy and de-alloy process with the LiBOB salt in electrolyte at 0 V vs. Li/Li⁺ in the cathodic sweep. During the anodic scan to the noble direction, the absence of an oxidation peak up to 3 V vs. Li/Li⁺ indicated that the air-formed oxide layer of Al was not reduced to metal. Oxide-free Al surfaces made by the in situ scratch test during the electrochemical polarization resulted in abrupt alloy formation with Li at 0 V vs. Li/Li⁺, but the newly formed surface formed passive films at higher potential with oxygen, namely, Al-O compound, as confirmed by ToF-SIMS.     

Facile fabrication of porous Ti2Nb10O29 microspheres for high-rate lithium storage applications

Ti₂Nb₁₀O₂₉ (TNO) microspheres are fabricated combining a solvothermal method with a subsequent heat-treatment. Structural and morphological properties of the as-prepared material have been characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and nitrogen adsorption/desorption. The electrochemical performance is evaluated by performing cyclic voltammograms and galvanostatic discharge/charge tests. The electrochemical characterization demonstrates that the as-prepared TNO microspheres exhibit a good electrochemical performance with a discharge capacity of 185 mAh g^?1 after 200 cycles and a capacity retention of 94% at 10 C. Furthermore, since TNO may react with Li at a voltage above 1.0 V vs. Li⁺/Li, TNO microspheres could be the promising high-power anode materials for 2 V vs. Li⁺/Li lithium-ion batteries applications.     

Nano-Sn/hard carbon composite anode material with high-initial coulombic efficiency

Nanoscaled tin (Sn) particles were embedded in the mesopores of hard carbon spherules (HCS) to form a composite anode material for lithium ion batteries. The structure of the obtained composite was characterized by X-ray diffraction (XRD) and the electrochemical performances were evaluated by galvanostatic cycling and cyclic voltammetry. It is found that embedding Sn nanoparticles into HCS not only results in a composite material with high-lithium storage capacity and capacity retention, but also increases the initial coulombic efficiency of the composite. Based on the infrared spectroscopic analysis, the enhanced initial coulombic efficiency is attributed to the nano-tin-induced decomposition of the ROCO₂Li species in the solid electrolyte interphase (SEI) layer.     

Characterization of all-solid-state Li/LiPONB/TiOS microbatteries produced at the pilot scale

All-solid-state Li/LiPONB/TiOS microbatteries were manufactured at the pilot scale on silicon substrate. In a first attempt, the characterization of the active materials constituting the microbattery was achieved in order to determine their accurate composition, structure and morphology. Finally, a thorough electrochemical characterization was carried out on all-solid-state cells. Excellent performances were noted in terms of cycle life (with more than 1000 cycles), efficiency and self-discharge (less than 5% per year). In addition, the positive electrode highlighted a high volumetric capacity close to 90 μAh cm⁻² μm⁻¹ when cycled at 100 μA cm⁻² between 1 V and 3 V vs. Li⁺/Li.     

Stabilizing lithium plating-stripping reaction between a lithium phosphorus oxynitride glass electrolyte and copper thin film by platinum insertion

Lithium (Li) plating-stripping reaction properties at the lithium phosphorus oxynitride glass electrolyte (LiPON)/copper thin film (Cu) interface is improved by the insertion of nano-thickness platinum (Pt) layer at the interface. The LiPON films are formed on mirror-polished lithium-ion conductive solid electrolyte sheets, and current collector thin films of Li, Cu-Pt multi layer, and Cu are formed on the LiPON films. The plating-stripping reactions at the LiPON/current collector films interface are carried out by galvanostatic and potential sweep measurements. Galvanostatic measurements reveal that Pt layer insertion reduces the overvoltage of the reaction and improves its coulomb efficiency. Also, cyclic voltammetry measurement suggests formation of Li-Pt alloys at higher voltages than 0 V (vs. Li/Li⁺) during the lithium plating process. Scanning electron microscopy observation clarifies that platinum insertion moderate non-uniform lithium plating reaction. Most probably, Li-Pt alloys increase the reaction sites, resulting in both the stabilization of current collector and the reduction of the overvoltage of the lithium plating-stripping reaction upon cycling. The results shown here will be useful in improving the anode reaction of the “Li-free” all-solid-state lithium batteries.     

Enhanced electrochemical properties of nanostructured bismuth-based composites for rechargeable lithium batteries

Nanostructured Bi/C and Bi/Al₂O₃/C composites, prepared by high-energy mechanical milling (HEMM), are investigated as anode materials for Li-ion rechargeable batteries. X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) reveal that the Bi/C nanocomposite is composed of nano-sized Bi and amorphous C, while the Bi/Al₂O₃/C nanocomposite (obtained by the mechanochemical reduction of Bi₂O₃ and Al) is composed of nano-sized Bi, amorphous Al₂O₃, and amorphous C. The electrochemical reaction mechanism of the Bi/C nanocomposite electrode is identified by ex situ XRD analyses combined with a differential capacity plot. Electrochemical tests show that the Bi/C and Bi/Al₂O₃/C nanocomposites exhibit enhanced electrochemical performances compared with that of the pure Bi electrode.     

Fabrication of all-solid-state lithium battery with lithium metal anode using Al2O3-added Li7La3Zr2O12 solid electrolyte

Li₇La₃Zr₂O₁₂ (LLZ) solid electrolyte is one of the promising electrolytes for all-solid-state battery due to its high Li ion conductivity and stability against Li metal anode. However, high calcination temperature for LLZ preparation promotes formation of La₂Zr₂O₇ impurity phase. In this paper, an effect of Al₂O₃ addition as sintering additive on LLZ solid electrolyte preparation and electrochemical properties of Al₂O₃-added LLZ were examined. By the Al₂O₃ addition, sintered LLZ pellet could be obtained after 1000 °C calcination, which is 230 °C lower than that without Al₂O₃ addition. Chemical and electrochemical properties of the Al₂O₃-added LLZ, such as stability against Li metal and ion conductivity, were comparable with the LLZ without Al₂O₃ addition, i.e. σ_bulk and σ_total were 2.4 × 10⁻⁴ and 1.4 × 10⁻⁴ S cm⁻¹ at 30 °C, respectively. All-solid-state battery with Li/Al₂O₃-added LLZ/LiCoO₂ configuration was fabricated and its electrochemical properties were tested. In cyclic voltammogram, clear redox peaks were observed, indicating that the all-solid-state battery with Li metal anode was successfully operated. The redox peaks were still observed even after one year storage of the all-solid-state battery in the Ar-filled globe-box. It can be inferred that the Al₂O₃-added LLZ electrolyte would be a promising candidate for all-solid-state battery because of facile preparation by the Al₂O₃ addition, relatively high Li ion conductivity, and good stability against Li metal and LiCoO₂ cathode.     

Electrochemical behaviors of wax-coated Li powder/Li4Ti5O12 cells

The wax-coated Li powder specimen was effectively synthesized using the drop emulsion technique (DET). The wax layer on the powder was verified by SEM, Focused Ion Beam (FIB), EDX and XPS. The porosity of a sintered wax-coated Li electrode was measured by linear sweep voltammetry (LSV) and compared with that of a bare, i.e., un-coated Li electrode. The electrochemical behavior of the wax-coated Li powder anode cell was examined by the impedance analysis and cyclic testing methods. The cyclic behavior of the wax-coated Li powder anode with the Li₄Ti₅O₁₂ (LTO) cathode cell was examined at a constant current density of 0.35 mA cm⁻² with the cut-off voltages of 1.2–2.0 V at 25 °C. Over 90% of the initial capacity of the cell remained even after the 300th cycle. The wax-coated Li powder was confirmed to be a stable anode material.     

Improvement of cycling stability of Si anode by mechanochemcial reduction and carbon coating

In this work, a novel composite consisting of nanosized silicon highly dispersed within the porous, elastic and conductive oxide/carbon matrix has been developed as an anode candidate for lithium ion batteries. The composite was prepared by a mechanochemical reaction between SiO and Li under ball milling followed by a carbon coating using the pyrolysis of poly(vinyl chloride)–co-vinyl acetate. The porous structure can effectively suppress the volume change of silicon during the electrochemically Li-alloying process. No obvious capacity fading was observed up to 100 cycles with a stable capacity of 620 mAh g⁻¹. The factors influencing the microstructure and the electrochemical behavior of the composite were discussed.     

Differential pulse effects of solid electrolyte interface formation for improving performance on high-power lithium ion battery

Solid electrolyte interface (SEI) formation is a key that utilizes to protect the structure of graphite anode and enhances the redox stability of lithium-ion batteries before entering the market. The effect of SEI formation applies a differential pulse (DP) and constant current (CC) charging on charge-discharge performance and cycling behavior into brand new commercial lithium ion batteries is investigated. The morphologies and electrochemical properties on the anode surface are also inspected by employing SEM and EDS. The electrochemical impedance spectra of the anode electrode in both charging protocols shows that the interfacial resistance on graphite anodes whose SEI layer formed by DP charging is smaller than that of CC charging. Moreover, the cycle life result shows that the DP charging SEI formation is more helpful in increasing the long-term stability and maintaining the capacity of batteries even under high power rate charge-discharge cycling. The DP charging method can provide a SEI layer with ameliorated properties to improve the performance of lithium ion batteries.     

全固态锂离子电池关键材料研究进展

全固态锂离子电池采用固态电解质替代传统有机液态电解液,有望从根本上解决电池安全性问题,是电动汽车和规模化储能理想的化学电源。为了实现大容量化和长寿命,从而推进全固态锂离子电池的实用化,电池关键材料的开发和性能的优化刻不容缓,主要包括制备高室温电导率和电化学稳定性的固态电解质以及适用于全固态锂离子电池的高能量电极材料、改善电极/固态电解质界面相容性。本文以全固态锂离子电池关键材料为出发点,综述了不同类型的固态电解质和正负极材料性能特征以及电极/电解质界面性能的调控和优化方法等,阐述了未来全固态锂离子电池关键材料的发展方向以及界面问题的解决思路,为探索全固态锂离子电池产业化前景奠定基础。     

MnO powder as anode active materials for lithium ion batteries

MnO powder materials are investigated as anode active materials for Li-ion batteries. Lithium is stored reversibly in MnO through conversion reaction and interfacial charging mechanism, according to the results of ex situ XRD, TEM and galvanostatic intermittent titration technique. A layer of the solid electrolyte interphase with a thickness of 20-60 nm is covered on MnO particles after full insertion. MnO powder materials show reversible capacity of 650 mAh g⁻¹ with average charging voltage of 1.2 V. It can deliver 400 mAh g⁻¹ at a rate of 400 mA g⁻¹. The cyclic performance of MnO is improved significantly after decreasing particle size and coating with a layer of carbon. Among observed transition metal oxides, MnO shows relatively lower voltage hysteresis (<0.7 V) between the discharging and the charging curves at 0.05 C. In addition to its environmental benign feature and high density (5.43 g cm⁻³), MnO seems a promising high capacity anode material for Li-ion batteries among transition metal oxides. However, the initial columbic efficiency is less than 65% and the voltage hysteresis is still too high. The origins of them are discussed.     

Porous NiO/poly(3,4-ethylenedioxythiophene) films as anode materials for lithium ion batteries

NiO/poly(3,4-ethylenedioxythiophene) (PEDOT) films are prepared by chemical bath deposition and electrodeposition techniques using nickel foam as the substrate. These composite films are porous, and constructed by many interconnected nanoflakes. As anode materials for lithium ion batteries, the NiO/PEDOT films exhibit weaker polarization and better cycling performance as compared to the bare NiO film. Among these composite films, the NiO/PEDOT film deposited after 2 CV cycles has the best cycling performance, and its specific capacity after 50 cycles at the current density of 2 C is 520 mAh g⁻¹. The improvements of these electrochemical properties are attributed to the PEDOT, a highly conductive polymer, which covers on the surfaces of the NiO nanoflakes, forming a conductive network and thus enhances the electrical conduction of the electrode.     

The electrochemical behaviour of the carbon-coated Ni0.5TiOPO4 electrode material

Ni_0.5TiOPO₄ oxyphosphate exhibits good electrochemical properties as an anode material in lithium ion batteries but suffers from its low conductivity. We present here the electrochemical performances of the synthesized Ni_0.5TiOPO₄/carbon composite by using sucrose as the carbon source. X-ray diffraction study confirms that this phosphate crystallizes in the monoclinic system (S.G. P2₁/c). The use of the Ni_0.5TiOPO₄/C composite in lithium batteries shows enhanced electrochemical performances compared with the uncoated material. Capacities up to 200 mAh g⁻¹ could be reached during cycling of this electrode. Furthermore, an acceptable rate capability was obtained with very low capacity fading even at 0.5C rate. Nevertheless, a considerable irreversible capacity was evidenced during the first discharge. In situ synchrotron X-ray radiation was utilized to study the structural change during the first discharge in order to evidence the origin of this irreversible capacity. Lithium insertion during the first discharge induces an amorphization of the crystal structure of the parent material accompanied by an irreversible formation of a new phase.     

Hydrogen storage properties of lithium silicon alloy synthesized by mechanical alloying

A lithium silicon alloy was synthesized by mechanical alloying method. Hydrogen storage properties of this Li-Si-H system were studied. During hydrogenation of the lithium silicon alloy, lithium atom was extracted from the alloy and lithium hydride was generated. Equilibrium hydrogen pressures for desorption and absorption reactions were measured in a temperature range from 400 to 500 °C to investigate the thermodynamic characteristics of the system, which can reversibly store 5.4 mass% hydrogen with smaller reaction enthalpy than simple metal Li. Li absorbing alloys, which have been widely studied as a negative electrode material for Li ion rechargeable batteries, can be used as hydrogen storage materials with high hydrogen capacity.