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Uniform distribution of siloxane-grafted SiO 0.26 hydrophobic nanoparticles in porous micron hard-carbon matrix was in situ made by a simple mixing in the organic medium of N-methylpyrrolidinone during the slurry preparation of composite anode for a fast-charge of lithium-ion batteries, whose characteristics are advantageous for a good electronic conductivity and the accommodation of volume change of silicon during charge-discharge cycling. The composite anode enables fast charge in 6 min at the rate of 10 C and high cycling stability, delivering the discharge capacities of 648–538 mAh g −1 , coulombic efficiencies of 99%, and high capacity retention of 98% at the 100th cycle. Surface and structural analysis results reveal that the formation of relatively thinner solid electrolyte interphase (SEI) layer at 10 C and higher structural maintenance than at low rate (0.2 C) are correlated to lowered interfacial resistances at 10 C and a good high-rate cycling stability. The data give an insight into material design principles and the SEI property of anode for high-rate lithium-ion batteries.

Driven by the limited global resources of lithium, magnesium metal batteries are considered as potential energy storage systems. The battery chemistry of magnesium metal anode, however, limits the selection of electrolytes, cathode materials and working temperature, making the realization of magnesium metal batteries complicated. Herein, we report the development of a new magnesium-insertion anode, magnesium stannide (Mg2Sn), and demonstrate reversible electrochemical Mg2+-extraction and insertion of Mg2Sn anode at 0.2 V versus Mg, delivering discharge capacity of 270 mAhg−1 in a half-cell with the electrolyte of PhMgCl/THF and enabling of room temperature magnesium-ion batteries with Mg2Sn anode combined with Mg-free oxide cathode and conventional-type electrolyte of Mg(TFSI)2/diglyme. The combination of Mg2Sn anode with various cathodes and electrolytes holds great promise for enabling room temperature magnesium-ion batteries.

All-solid-state lithium batteries offer notable advantages over conventional Li–ion batteries with liquid electrolytes in terms of energy density, stability, and safety. To realize this technology, it is critical to develop highly reliable solid-state inorganic electrolytes with high ionic conductivities and adequate processability. Li1+xAlxTi2−x(PO4)3 (LATP) with a NASICON (Na superionic conductor)-like structure is regarded as a potential solid electrolyte, owing to its high “bulk” conductivity (ca. 10−3 S cm−1) and excellent stability against air and moisture. However, the solid LATP electrolyte still suffers from a low “total” conductivity, mainly owing to the blocking effect of grain boundaries to Li+ conduction. In this study, an LATP–Bi2O3 composite solid electrolyte shows very high total conductivity (9.4×10−4 S cm−1) at room temperature. Bi2O3 acts as a microstructural modifier to effectively reduce the fabrication temperature of the electrolyte and to enhance its ionic conductivity. Bi2O3 promotes the densification of the LATP electrolyte, thereby improving its structural integrity, and at the same time, it facilitates Li+ conduction, leading to reduced grain-boundary resistance. The feasibility of the LATP–Bi2O3 composite electrolyte in all-solid-state Li batteries is also examined in this study.

Electrochemical cycling performance of microsize bulk and thin film Sn electrodes up to 50 cycles in Mg half-cell configuration, as well as Mg diffusivity and interfacial reaction behavior in a phenylmagnesium chloride (PhMgCl)/THF electrolyte are studied. The bulk Sn electrode delivers capacities of 321–289 mAh g−1 with capacity retention of 90 % and coulombic efficiencies higher than 99 % over 30 cycles, and thus demonstrates the potential of Sn anodes. The Sn film electrode shows good cycling ability. Surface analysis by XPS reveals that the surface of cycled electrodes is composed of a mixture of various inorganic salts of Sn and Mg formed by interfacial reactions between Sn and PhMgCl, and organic functionality produced by decomposition of THF, indicating surface film formation. The Mg2+ diffusivity of Sn is on the order of 10−11 cm2 s−1, which is four orders of magnitude lower than the Li+ diffusivity of Sn in Li-ion batteries. Advanced material design for enhanced electronic conductivity and control of the interfacial chemistry for formation of a surface protective film are believed to be the keys to overcome such sluggish kinetics, increase the capacity, and improve the cycling performance.

Research progress of high-energy performance and interfacial phenomena of Li 1.13 Mn 0.463 Ni 0.203 Co 0.203 O 2 cathode and graphite anode in a 55 °C full-cell under an aggressive charge cut-off voltage to 4.7 V (4.75 V vs. Li/Li + ) is reported. Although anodic instability of conventional electrolyte is the critical issue on high-voltage and high-temperature cell operation, interfacial phenomena and the solution to performance improvement have not been reported. Surface spectroscopic evidence revealed that structural degradation of both cathode and anode materials, instability of surface film at cathode, and metal-dissolution from cathode and -deposition at anode, and a rise of interfacial resistance with high-voltage cycling in 55 °C conventional electrolyte are resolved by the formation of a stable surface film with organic/inorganic mixtures at cathode and solid electrolyte interphase (SEI) at anode using blended additives of fluorinated linear carbonate and vinylene carbonate. As a result, significantly improved cycling stability of 77% capacity retention delivering 227−174 mAhg −1 after 50 cycles is obtained, corresponding to 819−609 Wh per kg of cathode active material. Interfacial stabilization approach would pave the way of controlling the performance and safety, and widening the practical application of Li-rich layered oxide cathode materials and high-voltage electrolyte materials in various high-energy density Li-ion batteries.

Capacity of layered lithium nickel-cobalt-manganese oxide () cathode material can increase by raising the charge cut-off voltage above 4.3 V vs. , but it is limited due to anodic instability of conventional electrolyte. We have been screening and evaluating various sulfone-based compounds of dimethyl sulfone (DMS), diethyl sulfone (DES), ethyl methyl sulfone (EMS) as electrolyte additives for high-voltage applications. Here we report improved cycling performance of cathode by the use of dimethyl sulfone (DMS) additive under an aggressive charge condition of 4.6 V, compared to that in conventional electrolyte, and cathode-electrolyte interfacial reaction behavior. The cathode with DMS delivered discharge capacities of over 50 cycles and capacity retention of 84%. Surface analysis results indicate that DMS induces to form a surface protective film at the cathode and inhibit metal-dissolution, which is correlated to improved high-voltage cycling performance.

As the lithium-ion battery (LIB) market for electric vehicles and grid-based energy storage systems is rapidly growing, the upcoming urgent challenge is to charge faster the LIB than ever. Thus, battery chemistry and reaction kinetics are being evolved toward the development of quickly charged LIBs in minutes scale, not in hours scale. In the LIB electrolyte perspective, commercial carbonate-based liquid electrolyte has multiple limitations in attaining high rate performance, due to the limited ionic conductivity and viscosity, sluggish de-solvation kinetics on graphite anode, low thermal stability, etc. To overcome those limitations, extensive research on new electrolyte systems (e.g., highly concentrated salt, aqueous system, etc.) have been reported. Herein, we present the improved rate capability and cycling performance of nickel-rich layered oxide-based lithium cell with our newly designed electrolytes. We are going to discuss electrode-electrolyte interface chemistry and its correlation to performance in this meeting. Acknowledgements This research was supported by the National Research Foundation grant funded by the Ministry of Science and ICT (No. 2019R1A2C1084024) and Creative Human Resource Development Consortium for Fusion Technology of Functional Chemical/Bio Materials of BK Plus program by Ministry of Education of Korea.

Understanding the chemical processes that occur at the electrode/electrolyte interface in a battery is crucial, as the interactions between anode/cathode and electrolyte and between cathode and anode of a full-cell determine the final battery performance. We have investigated the correlation among cycling performance, interfacial reaction behavior and the solid electrolyte interphase (SEI) stability of a LiNi 0.5 Co 0.2 Mn 0.3 O 2 //Si-graphite full-cell under an aggressive test condition between 3.0 and 4.55 V using fluoroethylene carbonate (FEC)-based electrolyte, and blended additives of methyl (2,2,2-trifluoroethyl)carbonate (FEMC) and vinylene carbonate (VC). Through the formation of a stable SEI at both high-voltage cathode and anode, metal dissolution from the cathode is inhibited and full-cell achieves enhanced cycling performance. Interfacially stabilized full-cell delivers a high energy of 622 Wh per kg of active material and improved capacity retention, whereas the cell in conventional electrolyte shows a rapid performance fade.

Lithium diffusivity of fluorine-free and -doped tin-nickel (Sn-Ni) film model electrodes with improved interfacial (solidelectrolyte interphase (SEI)) stability has been determined, utilizing variable rate cyclic voltammetry (CV). The methodfor interfacial stabilization comprises fluorine-doping on the electrode together with the use of electrolyte including flu-orinated ethylene carbonate (FEC) solvent and trimethyl phosphite additive. It is found that lithium diffusivity of Sn islargely dependent on the fluorine-doping on the Sn-Ni electrode and interfacial stability. Lithium diffusivity of fluorine-doped electrode is one order higher than that of fluorine-free electrode, which is ascribed to the enhanced electrical con-ductivity and interfacial stabilization effect.Keywords: Lithium-ion batteries, Lithium diffusivity T, in-nickel anode, Film model electrode, Fluorine-doping In, terfacials tability Received July 13, 2015 : Accepted November 2, 2015 1. Introduction Tin (Sn)-based materials have been recognized asone of the attractive anode materials, which can replacethe commercialized graphite, primarily because of thelarger theoretical capacity (~994 mAhg

The ammonia-free green coprecipitation process has successfully produced a micro-sized spherical Ni0.5Co0.2Mn0.3(OH)2 precursor with a homogeneous elemental distribution. The replacement of ammonia with citric acid as a chelating agent was the key for this eco-friendly and cost-effective process. The pH of coprecipitation was determined from solubility and complex formation diagrams calculated using solubility products and formation constants. By varying the relative ratio of citric acid to metals, the optimized particle morphology, size and robustness of the precursor were obtained. The cathode material LiNi0.5Co0.2Mn0.3O2, prepared using the hydroxide coprecipitate precursor, showed a good charge–discharge cycling performance in lithium cells, delivering high capacity and cycling stability (≥94% retention) at 3.0–4.3 V as well as upon high-voltage operation at 4.6 V.

High-capacity Li-rich layered composite oxide, xLi2MnO3(1-x)LiMO2 (M = Mn, Ni, Co), is a promising candidate cathode material for high-energy electrochemical energy storage. Enabling the high-performance of high-voltage cathode relies on an electrolyte breakthrough and the solid electrolyte interface (SEI) stabilization. In this study, the 0.6Li2MnO30.4LiNi0.45Co0.25Mn0.3O2 (Li1.2Mn0.525Ni0.175Co0.1O2, LMNC) cathode is operated at 2.5–4.8 V with 5 wt% fluorinated linear carbonate, di-(2,2,2 trifluoroethyl)carbonate (DFDEC), as a high-voltage electrolyte additive, for the first time and applied to a high-energy lithium-ion battery. The cathode with DFDEC outperforms that in electrolyte only, delivering a high capacity of 250 mAhg−1 with an excellent charge-discharge cycling stability at the rate of 0.2C. Upon the use of DFDEC, the cathode surface is effectively passivated by a stable SEI composed of DFDEC decomposition products, which inhibit a detrimental metal dissolution and structural cathode degradation. A full-cell based on the SEI-stabilized LMNC cathode and graphite anode successfully demonstrates doubled energy density (~278 Whkg−1) compared to ~136 Whkg−1 of a commercialized cell of graphite//LiCoO2 and an excellent cycling stability.

Control of electrode–electrolyte interfacial reactivity and the formation of the solid electrolyte interphase (SEI) layer is a key technology for high performance rechargeable lithium batteries. Here we present the first report on a promising interfacial approach for Sn–Ni electrode that the use of acid-resisting and -scavenging fluorine-dopant on Sn combined with acid-scavenging trimethyl phosphite electrolyte additive to LiPF6-contiaing carbonate-based organic electrolyte improves the interfacial stability of Sn to acidic electrolyte species. As a result, a stable SEI layer consisting of a plenty of carbonate decomposition products forms and cycling ability significantly improves, in contrast to less efficient SEI formation and rapid performance fade for the electrodes without fluorine-dopant or trimethyl phosphite additive.

Lithium diffusivity of the silicon (Si)-based materials of Si-Cu and SiO x (x = 0.4, 0.85) withimproved interfacial stability to electrolyte have been determined, using variable rate cyclic vol-tammetry with film model electrodes. Lithium diffusivity is found to depend on the intrinsic prop-erties of anode material and electrolyte; the fraction of oxygen for SiO x (x = 0.4, 0.85), which isdirectly related to electrical conductivity, and the electrolyte type with different ionic conductivityand viscosity, carbonate-based liquid electrolyte or ionic liquid-based electrolyte, affect the lithiumdiffusivity. Keywords : Rechargeable lithium batteries, Si-based anode, Lithium diffusivity, Film model electrode ( Received September 23, 2013 : Accepted October 7, 2013) 1. Introduction There is an increasing need of high-energyrechargeable lithium batteries for their applications toelectric vehicles and stationary energy storage gridsystems. This represents the development need ofhigher capacity anode materials, and higher capacityand higher voltage cathode materials with a stablecycling ability and safer characteristics than the con-ventional ones.

/EC:EMC. SEM imaging reveals that the facetting on higher surface energy plane of (101) is additionallydeveloped at the edges of an octahedron that is predominantly grown with the most thermodynamically stable(111) plane, which enhances interfacial reactivity. Fluorine-doping also increases the amount of interfaciallyreactive Mn

Film model electrodes of silicon oxide (SiOx) with various oxygen content (x = 0.4, 0.85, 1.0 and 1.3) have been studied for the effects of oxygen content and interfacial reaction behavior on cycling ability. IR and XPS analyses on the origin of initial charge plateau in 1M LiPF6/EC:DEC indicate that the contribution of electrolyte reduction to the plateau is far larger than the formation of lithium silicates, lithium oxide and silicon. Higher oxygen content of SiOx induces to decrease initial electrolyte reduction, whereas larger fraction of oxides is subjected to dissolution by acid (e.g., HF)-etching. Cycling ability at higher oxygen content however is remarkably improved when constructing a surface protective siloxane network at the electrodes using silane electrolyte additive. The SiO1.0 electrode exhibits superior capacity retention of 84% at the 200th cycle delivering discharge capacity of 1206–1017 mAh/g. The SEI layer formed over surface siloxane network consists of a plenty of organic compounds and lithium carbonate, in contrast to mainly inorganic salts and organic phosphorus fluoride compounds upon cycling without silane adidtive. A better protection and passivation of electrode surface should be of the effects of siloxane network, and in that fashion cycling ability is greatly stabilized.

The cycling behavior of Li 4 Ti 5 O 12 /LiCoO 2 cells in the ionic liquid electrolytes based on 1-butyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl) imide (BMP-TFSI) with different additives, such as vinylene carbonate (VC), 1,3-propane sultone (PS) and their mixture is investigated. The cell assembled with BMP-TFSI containing 10 wt% VC/PS (1:1 by weight) exhibits reversible cycling behavior with good capacity retention. FTIR studies reveal that the electrochemically stable solid electrolyte interphase forms on Li 4 Ti 5 O 12 electrode in the presence of a mixture of VC and PS during cycling. The additives hardly affect the composition, thickness and stability of the surface film formed on the LiCoO 2 cathode.

Structural volume change occurring on the Si-based anode battery materials during alloying/dealloying with lithium is noticed to be a major drawback responsible for a limited cycle life. Silicon monoxide has been reported to show relatively improved cycling performance compared to Si-containing materials for rechargeable lithium batteries, due to the structural buff- ering role of in-situ formed Li2O and lithium silicate during the reaction of silicon monoxide and lithium. Here we report improved cycling ability of interfacially stabilized Si-SiO2-graphite composite anode using silane-based electrolyte additive for rechargeable lithium batteries, which includes low cost silicon dioxide for structural stabilization and graphite for enhanced conduc- tivity.

A FeSi 2.7 thin film is deposited on a copper substrate by RF magnetron sputtering of a Fe–Si alloy target. The electrochemical behavior of the FeSi 2.7 electrode in ionic liquid electrolyte based on 1-butyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl) imide is investigated and compared with that of a FeSi 2.7 electrode in conventional liquid electrolyte. The FeSi 2.7 electrode in the ionic liquid electrolyte delivers an initial discharge capacity of 756 mAh g −1 at room temperature, and its discharge capacity is maintained to be 92% of the initial discharge capacity after the 100th cycle. AC impedance and FTIR analysis reveal that the formation of a stable solid electrolyte interphase (SEI) layer on the FeSi 2.7 electrode in the ionic liquid electrolyte leads to a good capacity retention. This study demonstrates that the FeSi 2.7 electrode exhibits stable cycling behavior and good interfacial characteristics in the ionic liquid electrolyte without any solvents and additives.

Mesoporous TiO2 anatase microspheres consisting of self-assembled nanocrystals have been synthesized by a one-step hydrothermal method at 120 oC using titanium-peroxo complex, without a post-calcination process. Transmission and scanning electron microscopic imaging reveal that diamond-shaped nanocrystals as primary particles, which are 20 nm in average width and 50 nm in length and oriented with (101) plane of anatase phase, are aggregated to form a secondary microsphere particle with 0.5–1 μm in diameter. BET analysis data show that the TiO2 anatase particles possess significantly large surface area of 254 m2 g–1 with the pore size of ∼14 nm. Mesoporous TiO2 anatase anode shows an enhanced lithium storage performance in pyrrolidinium-based ionic liquid electrolyte diluted with ethyl methyl carbonate, delivering 195 - 150 mAhg-1 at the C/2 rate with 77 % capacity retention and 98–99 % Coulombic efficiencies over 50 cycles despite the absence of surface carbon-coating. AC impedance analysis results reveal...

cathodes upon oxidation of electrolyte during electrochemicalcycling was investigated. Information on the important factors for film formation on the cathode can facilitatethe design of additives that improve the properties of the cathode. Pyrazole is added to the electrolyte becauseit is readily oxidized to form a surface film on the cathode. The results of differential scanning calorimetry andFourier transform infrared spectroscopy (FTIR) showed that the active material played a dominant role in theinterfacial film formation with the electrolyte. Carbon black played a negligible role in the surface filmformation. Key Words : Li-ion battery, Li(Ni

Interfacial compatibility between the Si-Cu electrode and diluted ionic liquid electrolyte containing 50 vol.% of 1M lithium bis(trifluoromethanesulfonyl)imide (LiTFSI)/1-methyl-1-propylpyrrolidinium bis(trifluoromethylsulfonyl)imide (MPP-TFSI) and 50 vol.% dimethyl carbonate (DMC) in a lithium cell and dilution effect on surface chemistry are examined. ex-situ ATR FTIR analysis results reveal that the surface of the Si-Cu electrode cycled in the diluted ionic liquid electrolyte is effectively passivated with the SEI layer mainly composed of carboxylate salts-containing polymeric compounds produced by the decomposition of DMC. Surface species by the decomposition of TFSI anion and MPP cation are found to be relatively in a very low concentration level. Passivation of electrode surface with the SEI species contributes to protect from further interfacial reactions and to preserve the electrode structure over 200 cycles, delivering discharge capacity of > 1670 and capacity retention of 88% of maximum discharge capacity.

Gel polymer electrolytes containing a mixture of organic solvent and ionic liquid were prepared and their electrochemical properties were investigated. The gel polymer electrolytes exhibited good electrochemical stability and stable interfacial properties toward lithium metal. Using these gel polymer electrolytes, lithium metal polymer cells composed of a lithium anode and a LiFePO4 cathode were assembled, and their cycling performances were evaluated. The cells showed good cycling performance comparable to that of a cell assembled with gel polymer electrolyte containing only organic liquid electrolyte. The Li/LiFePO4 cells assembled with a gel polymer electrolyte containing ionic liquid are expected to be one of the promising candidates for high energy density lithium batteries with improved safety.

Silane-based self-assembly was employed for the surface modification of carbon-coated Si electrodes and their surface chemistry and electrochemical performance in battery electrolyte depending on the molecular structure of silanes was studied. IR spectroscopic analyses revealed that siloxane formed from silane-based self-assembly possessed Si-O-Si network on the electrode surface and high surface coverage siloxane induced the formation of a stable solid-electrolyte interphase (SEI) layer that was mainly composed of organic compounds with alkyl and carboxylate metal salt functionalities, and PF-containing inorganic species. Scanning electron microscopy imaging showed that particle cracking were effectively reduced on the carbon-coated Si when having high coverage siloxane and thickened SEI layer, delivering > 1480 mAh/g over 200 cycles with enhanced capacity retention 74% of the maximum discharge capacity, in contrast to a rapid capacity fade with low coverage siloxane.

Interfacial structures of electrode–current collector and electrode–electrolyte have been designed to be stabilized for improved cycling performance of amorphous silicon (Si) that is considered as an alternative anode material to graphite for lithium-ion batteries. Interfacial structural stabilization involves the interdigitation of Si electrode–Cu current collector substrate by anodic Cu etching with thiol-induced self-assembly, and the formation of self-assembled siloxane on the surface of Si electrode using silane. The novel interfacial architecture possesses promoted interfacial contact area between Si and Cu, and a surface protective layer of siloxane that suppresses interfacial reactions with the electrolyte of 1 M LiPF6/ethylene carbonate (EC):diethylene carbondate (DEC). FTIR spectroscopic analyses revealed that a stable solid electrolyte interphase (SEI) layer composed of lithium carbonate, organic compounds with carboxylate metal salt and ester functionalities, and PF-containing species formed when having siloxane on Si electrode. Interfacially stabilized Si electrode exhibited a high capacity retention 80% of the maximum discharge capacity after 200 cycles between 0.1 and 1.5 V vs. Li/Li+. The data contribute to a basic understanding of interfacial structural causes responsible for the cycling performance of Si-based alloy anodes in lithium-ion batteries.

Interfacial reactions of Sn during initial cycling in 1 M LiPF6/EC:DMC (1:1) were studied by characterizing the surface species formed on thin film electrodes of Sn, prepared with a pulsed laser deposition, using ex-situ ATR FTIR spectroscopy and microscopy. FTIR analyses indicated that at high voltage region above 1.0 V vs. Li/Li+ the surface of Sn electrode was covered by PF-containing inorganic species probably by the interfacial reactions between Sn and PF6− anions. With charging to 0.63 V low amounted organic species with carboxylate metal salt and alkyl functionalities appeared, due to the reductive decomposition of organic solvents. The organic surface species however were destroyed upon a deep charge to 0.1 V and reproduced on the subsequent discharge process, whereas P–F containing inorganic species remained preserved. No sustainment of organic surface species but the stable passivation of Sn surface by PF-containing species during initial cycling are believed to cause unstable interfacial structure and the possibility of reduced utilization of active Sn, respectively, resulting in the large initial irreversible capacity loss.

Surface layer formed on Sn thin film electrode in 1 M LiPF 6 /EC:DMC electrolyte was characterized using ex situ FTIR spectroscopy with the attenuated total reflection technique. IR spectral analyses showed that the immersion of Sn film in the electrolyte resulted in a chemical interfacial reaction leading to the passivation of Sn surface with primarily PF-containing inorganic surface species and small amount of organics. When constant current cycling was conducted with lithium cells with Sn film electrode at 0.1–1.0 V vs . Li/Li + , the interfacial reaction between Sn and electrolyte appeared significantly intensified that the features of PF-containing species became enhanced and new IR features of organic species (e.g. alkyl carbonate/carboxylate metal salts and ester functionalities) were observed. The surface layer continued to form with cycling, partly due to non-effective surface passivation as well as particle pulverization accompanied by enlargement of active surface area. Comparative IR spectral analyses indicated that the interfacial reaction between Sn and PF 6 − anion played a leading role in forming the surface layer, which is different from lithiated graphite that had mainly organic surface species. The data contribute to a better understanding of the interfacial processes occurring on Sn-based anode materials in lithium-ion batteries.

Palladium-coated magnesium–manganese–nickel films behave as gasochromic switchable mirrors, becoming transparent on exposure to dilute hydrogen, and reverting to a mirror state on exposure to air. The cycling stability of the optical switching depends upon preservation of the integrity of the Pd catalyst overlayer. Alloying between Mg and Pd causes interdiffusion of the two elements, and leads to degradation in switching speed and eventual deactivation. Incorporation of a thin niobium oxide barrier layer between the active magnesium alloy film and the Pd layer substantially improves the cycling stability of the mirror.

We have developed a new method to directly fabricate lithium cobalt oxide (LiCoO 2 ) films onto porous films by an electrodeposition method in solutions at low temperature. A set of porous substrate films consisting of a PTFE membrane-filter and paper was placed between a LiOH solution and a CoSO 4 solution. Cobalt compounds were deposited on the substrates under electrical currents of ∼1 mA/cm 2 using carbon electrodes. As a result, we found that LiCoO 2 films on the porous filter were successfully fabricated at 120 °C. Furthermore, the LiCoO 2 films did not cover the entire substrate, but formed only in the shape of the anode.

Increasing the capacity of Li-rich layered oxide (LMNC) cathode material for high-energy density lithium-ion batteries relies on the increase of charge cut-off voltage toward 5 V, under the utilization of anodically stable electrolyte component. The utilization of di-(2,2,2 trifluoroethyl)carbonate (DFDEC)-containing electrolyte permits significant improvement of anodic stability, cathode–electrolyte interface, and cycling stability of LMNC cathode, with respect to conventional electrolyte. In the present study, the limit of anodic stability of DFDEC under charging to 5.5 V versus Li is explored, and the interfacial processes of DFDEC-derived surface protection mechanism are investigated, utilizing charge cut-off voltage-dependent surface and structural analyses. The oxidative decomposition of DFDEC is found to begin at 4.7 V, producing metal fluorides and CF-containing organic compounds as the earliest surface species, passivating the cathode surface and reducing metal dissolution, structural transformation, and cathode degradation. The tolerable limit of charge cut-off voltage of a model electrolyte of 0.1 m LiPF6/DFDEC is determined to be 5.0 V, to which the cathode outperforms conventional electrolyte, delivering discharge capacities of 261–225 mAhg−1 with the capacity retention of 86% at the 50th cycle. The data give an insight into the principles of electrolyte design and high-voltage cathode–electrolyte interfacial stabilization toward advanced 5 V lithium-ion batteries.

In this paper, a newly developed idea for direct fabrication of double oxide films on various substrates, the “dual anode system,” is described. Films of LiCoO2 were directly fabricated on Pt, Ni, and graphite substrates by a hydrothermal–electrochemical method at 125–175°C for 2 hours in a flow cell using a cobalt metal anode as a cobalt ion source and a 4M LiOH aqueous solution as a lithium source, without any subsequent firing or annealing. The target substrate (Pt, Ni, or graphite) was also connected to the anode in the dual anode system. The addition of an oxidant, H2O2, in the flowing LiOH solution has produced LiCoO2 films in a short reaction time of 2 h using the flow cell. The H2O2 seems to accelerate the oxidation of Co2+ into Co3+ in cobalt species during the reactions, dissolution–oxidation–precipitation. The thickness and the microstructure of the films could be controlled. In optimum conditions, the film consisting of plate-like LiCoO2 crystals at most a few micrometers thick could be obtained. Micro-Raman and X-ray diffraction studies demonstrated that increasing the fabrication temperature produces a phase change in LiCoO2 from spinel to hexagonal. Spinel phase LiCoO2 is obtained around 125°C and hexagonal phase appears above 125°C. Above 150°C, the redissolution rate of formed crystals seems to dominate the formation of crystals; thus the grain size decreases with increasing temperature.

Formation of the SEI layer on Si–Cu film electrode in the ionic liquid electrolyte of 1 M lithium bis(trifluoromethylsulfonyl)imide/1-methyl-1-propylpyrrolidinium bis(trifluoromethylsulfonyl)imide (LiTFSI/MPP-TFSI) was investigated using ex-situ ATR FTIR and X-ray photoelectron spectroscopy. The SEI layer is found to be composed of organic and inorganic compounds that are the decomposition products of MPP cation and TFSI anion, and effectively passivate the electrode surface during initial cycling. Formation of a stable SEI layer leads to an excellent capacity retention 98% of the maximum discharge capacity, delivering discharge capacities of >1620 mAhg−1 over 200 cycles. The data contribute to a basic understanding of SEI formation and composition responsible for the cycling performance of Si-based alloy anodes in ionic liquid electrolyte-based rechargeable lithium batteries. Keywords: Rechargeable lithium batteries, Si-based anode, Ionic liquid electrolyte, SEI layer

Li1−xNi1+xO2 and LiCoO2 films as cathodes for lithium rechargeable microbatteries were fabricated in a concentrated LiOH solution at 20–200°C using different Soft Solution-Processing methods. While LiCoO2 films can be obtained by a purely hydrothermal reaction, a supplementary electrochemical charge with the same hydrothermal conditions is necessary to produce Li1−xNi1+xO2 films. A film formation mechanism study elucidated the necessity of such different activation methods for the preparation of Li1−xNi1+xO2 and LiCoO2 films.

LiCoO2 film and powder applicable to rechargeable lithium microbatteries have been directly prepared at the same time by hydrothermal treatment of a cobalt metal plate in a concentrated LiOH solution. The effect of LiOH concentration (0.1–6 M) on the structural change in film and powder has been examined using the XRD, micro-Raman and SEM analyses. It is found that all the powders with a layered hexagonal structure are precipitated by homogeneous nucleation regardless of LiOH concentration, whereas the dependence of film structure on the concentration is revealed by a selection of phase such as cobalt hydroxide species, hexagonal or cubic spinel phases formed by heterogeneous nucleation.

Well-crystallized and electrochemically active Li1-xNi1+xO2 and LiCoO2 thin-film electrodes for lithium rechargeable microbatteries can be fabricated in a single synthetic step using an economical,...

Layered nickel and zinc hydroxy double acetates have been prepared by both hydrothermal and coprecipitation methods. According to the X-ray absorption spectroscopic analyses at the Ni and Zn K-edge for the hydrothermally prepared precipitates, it was found that the brucite-type nickel hydroxide is formed with partial nickel vacancies, and the zinc ions are stabilized in tetrahedral sites just below and above the nickel vacant sites in hydroxide planes, with three hydroxide and one acetate ligands. The X-ray diffraction patterns indicate that the hydrothermally prepared precipitates exhibit an evolution of the interlayer distance with respect to air-drying time at 25°C, while such a change could not be observed for precipitates obtained by coprecipitation. Such a different behavior arises from the difference in their positive layer charges and the contents of inserted acetate anion. From the FT-IR spectroscopic study, it is concluded that the reversible structural phase transformation is resulting from the change of orientation of intercalated acetates depending on the type of ligation, chelating or unidentate ones.

The Li x Ni 1 − y Ti O 2 (0.1 ≤ y ≤ 0.5) solid solution has been prepared by solid state reaction. From the X-ray diffraction analysis, these materials were found to have rhombohedral layered structure and an isostructure of LiNiO 2 . The partial disordering between transition metal (Ni and Ti) layer and lithium was detected by the Rietveld refinement. According to the X-ray photoelectron spectroscopic studies, the titanium and nickel in the lattice was found to be trivalent and bivalent, respectively. From the Ni K-edge X-ray absorption spectroscopic analysis, the presence of the mixed valence state of Ni(II) and Ni(III) was observed, and the increase of the coordination number of long Ni-O bond from 2 (for LiNiO 2 ) to 3 was determined, indicating the reduction of ca. 30% Ni(III) to Ni(II). By considering the ionic radius and the NiO bond length, the Ni(II) ions are concluded to be partially stabilized in the lithium site. Li LiAsF 6 in EC, DEC Li x Ni 1 − rmy Ti y O 2 ( y = 0.1, 0.3) cell showed far larger charging rates ( Δx = 0.25 ~ 0.4) than discharging one in a high charge cut-off voltage of 4.5 V.

The optimum pH for preparing single-phase Pb(Mg1/3Nb2/3)O3(PMN) powder can be estimated from the solubility vs. pH diagrams for the corresponding metal ions in hydroxide, carbonate and citrate media. The homogeneous and stoichiometric citrate PMN precursor could be prepared from the system Pb–Mg–Nb–citric acid–H2O by adjusting the pH of the solution to 6. Ultrafine (0.05–0.3 µm) and stoichiometric PMN powder could be obtained through the thermal decomposition of the citrate precursor at the relatively low temperature of 900 °C.

The title compound is synthesized by solid state reaction of SrCO3, MgO, and (NH4)2HPO4 (air, 1303 K, 4 h and 1323 K, 4 h, 90% yield) and its structure is determined by powder XRD.

Control of electrode–electrolyte interfacial stability and the composition of the solid electrolyte interphase (SEI) layer is a promising approach for improved cycling performance of silicon-based anode material for rechargeable lithium batteries. Here we demonstrate that a room temperature ionic liquid electrolyte effectively passivates the surface of the SiO1.3 electrode and significantly enhances cycling ability in contrast to the commercial liquid electrolyte. The SiO1.3 electrode, prepared by pulsed laser deposition, showed 88% capacity retention in the ionic liquid electrolyte of 1 M LiTFSI/Py13TFSI delivering 1058–930 mA h g−1 over 200 cycles. Results from infrared and X-ray photoelectron spectroscopic analyses suggest that the presence of organic SEI compounds consisting of the pyrrolidinium cation and TFSI anion and their decomposition products on the oxygen-abundant SiO1.3 surface confers interfacial stability and cycling stability.

Thin films of Cu{sub 2}Sb, prepared on stainless steel and copper substrates with a pulsed laser deposition technique at room temperature, have been evaluated as electrodes in lithium cells. The electrodes operate by a lithium insertion/copper extrusion reaction mechanism, the reversibility of which is superior when copper substrates are used, particularly when electrochemical cycling is restricted to the voltage range 0.65-1.4 V vs. Li/Li{sup +}. The superior performance of Cu{sub 2}Sb films on copper is attributed to the more active participation of the extruded copper in the functioning of the electrode. The continual and extensive extrusion of copper on cycling the cells leads to the isolation of Li{sub 3}Sb particles and a consequent formation of Sb. Improved cycling stability of both types of electrodes was obtained when cells were cycled between 0.65 and 1.4 V. A low-capacity lithium-ion cell with Cu{sub 2}Sb and LiNi{sub 0.8}Co{sub 0.15}Al{sub 0.05}O{sub 2} electrodes, laminated from powders, shows excellent cycling stability over the voltage range 3.15-2.2 V, the potential difference corresponding to approximately 0.65-1.4 V for the Cu2Sb electrode vs. Li/Li{sup +}. Chemical self-discharge of lithiated Cu{sub 2}Sb electrodes by reaction with the electrolyte was severe when cells were allowed to relax on open circuitmore » after reaching a lower voltage limit of 0.1 V. The solid electrolyte interphase (SEI) layer formed on Cu2Sb electrodes after cells had been cycled between 1.4 and 0.65 V vs. Li/Li{sup +} was characterized by Fourier transform infrared spectroscopy; the SEI layer contributes to the large irreversible capacity loss on the initial cycle of these cells. The data contribute to a better understanding of the electrochemical behavior of intermetallic electrodes in rechargeable lithium batteries.« less

Electrochemically active thin films of Mg 2 Si in various film thicknesses of 30-380 nm have been prepared with the pulsed laser deposition technique. The thinnest film of 30 nm showed a highly stable cycling behavior at 0.1-1.0 V vs. Li, delivering capacity greater than 2000 mAh/g for more than 100 cycles. Though the film morphology became remarkably rougher with cycling, the films showed good stability. However, the first cycle irreversible capacity loss increased with film thickness. Therefore, lithium adsorption/desorption reaction forming Li-Si alloy at the Si-rich film surface is suggested as one of the sources of the large capacity of the 30 nm film. The superior capacity retention, when compared to porous electrodes of this alloy, may be attributed to a limited structural volume change in the two-dimensional film, shorter lithium diffusion path and enhanced conductivity from stainless steel substrate. The goals of this study are to promote the emerging need of thin film anodes for all solid-state microbatteries and clarify the capacity failure of powder intermetallic anodes for rechargeable lithium batteries.

An economical, energy-efficient, and environmentally friendly solution process was used to prepare lithiated thin-film electrodes as a cathode for lithium rechargeable microbatteries. Well-crystallized and electrochemically active lithium cobalt oxide thin-film electrodes were spontaneously fabricated in a single synthetic step in a 4M lithium hydroxide solution at room temperature without any post-synthesis annealing. The estimated film properties show that the obtained spinel lithium cobalt oxide films (space group Fd3m) has possible use as a desired cathode film.