Extensive applications of rechargeable lithium-ion batteries (LIBs) to various portable electronic devices and hybrid electric vehicles result in the increasing demand for the development of electrode materials with improved electrochemical performance including high energy, power density, and excellent cyclability, while maintaining low production cost. Here, we present a direct synthesis of ferrite/carbon hybrid nanosheets for high performance lithium-ion battery anodes. Uniform-sized ferrite nanocrystals and carbon materials were synthesized simultaneously through a single heating procedure using metal-oleate complex as the precursors for both ferrite and carbon. 2-D nanostructures were obtained by using sodium sulfate salt powder as a sacrificial template. The 2-D ferrite/carbon nanocomposites exhibited excellent cycling stability and rate performance derived from 2-D nanostructural characteristics. The synthetic procedure is simple, inexpensive, and scalable for mass production, and the highly ordered 2-D structure of these nanocomposites has great potential for many future applications.

A vanadium pentoxide electrode is prepared in the amorphous form (a-V2O5), and its electrode performances are compared to those for its crystalline counterpart (c-V2O5). The a-V2O5 electrode outperforms c-V2O5 in several ways. First, it is free from irreversible phase transitions and Li trapping, which evolve in c-V2O5, probably due to the lack of interactions between the inserted Li+ ions/electrons and V2O5 matrix. Second, the absence of Li trapping allows a reversible capacity amounting to >600 mA h g–1, which is larger than that given by c-V2O5. Third, it shows an excellent rate property. The notably high reversible capacity and rate capability seem to be due to Li storage at vacant sites that are ill-defined but numerous in a-V2O5, which Li+ ions can easily access. However, irreversible capacity of a-V2O5 is appreciable in the first cycle due to a parasitic Li reaction with surface hydroxyl groups. Treatment with n-butyllithium can suppress the irreversible capacity by removing the surface hydroxyl groups.

Re-deposition of manganese compounds on LiMn 2 O 4 electrode after Mn dissolution and its impact on the positive electrode performances are studied by a control experiment, in which the spinel electrode is stored in its charged state at elevated temperature (60 • C) to accelerate Mn dissolution. Upon storage with Li foil, the re-deposition of manganese species is marginal since the dissolved Mn 2+ ions move to the Li foil to be deposited. When stored without Li foil, however, under which the chance for re-deposition of Mn species on the spinel electrode is rather high, the dissolved Mn 2+ ions are deposited as oxide and fluoride. The depth-profiling X-ray photoelectron spectroscopy and transmission electron microscope studies illustrate that Mn-O species are deposited in the earlier period of storage, whereas the Mn-F compounds (MnF 2 ) in the later stage. Due to the deposition of highly resistive MnF 2 phase, the electrode stored for a longer period of time shows a severe cell polarization and capacity loss.Since the reversible lithium intercalation/de-intercalation was reported with the lithium manganese oxide (LiMn 2 O 4, LMO hereafter) in the mid-1980s, this spinel-structured material has been extensively studied as the positive electrode for lithium-ion batteries (LIBs). At present, the LIBs adopting this 4 V positive electrode are widely used as the power source for small electronic devices, and their consumer market seems to be expanded in the near future for electric vehicles (EVs) since this material satisfies the most-demanding requirements for EVs applications; cost, high power and safety characteristics. [1][2][3][4][5][6][7] The high power performance stems from its three-dimensional Li + diffusion channels, whereas the better safety characteristics from its superior thermal stability. That is, LMO is considered as a safer positive electrode as the onset temperature for oxygen release at its charged state is higher than that for the other positive electrode materials. 8 One critical shortcoming for this material is, however, the poor cycle stability that is mainly associated with Mn dissolution during extended cycling. 9 The Mn dissolution has been considered as the most crucial aging mechanism for LMO. Obviously, the Mn dissolution leads to a loss of active material itself from the electrode layer. Many complicated aging mechanisms are also induced by Mn dissolution; an increase in cell polarization, unwanted structural and phase changes, and formation of surface films on negative and positive electrodes. 10-18 Mn dissolution is known to degrade the negative electrode when the graphitic carbons are assembled with LMO positive electrode. Dissolved manganese ions move to the negative electrode to be deposited in the metallic state, which is accompanied by the self-discharge of lithiated graphite. The metallic Mn, which is incorporated into the solid electrolyte interphase (SEI) layer on the negative electrode, is known to induce additional electrolyte decomposition. [19][20][21] It is also known that ...

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The solid electrolyte interphase (SEI) acts as a protection layer on the surface the anodes of lithium ion batteries to prevent further electrolyte decomposition. Understanding the fundamental properties of the SEI is essential to the development of high capacity silicon anodes. However, the detailed mechanism of the generation of the evolution of the SEI on the silicon anodes is not fully understood. This manuscript reviews our recent investigations of the SEI on silicon anodes. We have studied the fundamental formation mechanism of the SEI on silicon anodes, along with the evolution which occurs to the SEI upon cycling.