Search

Battery safety is an ever-increasing significance to guarantee consumer's safety. Reducing or preventing the risk of battery fire and explosion is a must for battery manufacturers. Major reason for the occurrence of fire in commercial lithium-ion batteries is the flammability of conventional organic liquid electrolyte, which is typically composed of 1 M LiPF6 salt and ethylene carbonate (EC)-based organic solvents. Herein, we report the designed 1 M LiPF6 and EC-based nonflammable electrolyte including methyl(2,2,2-trifluoroethyl)carbonate, which breaks the conventional perception that EC-based liquid electrolyte is always flammable. The designed electrolyte also provides high anodic stability beyond the conventional charge cut-off voltage of 4.2 V. A graphite∥LiNi0.6Co0.2Mn0.2O2 lithium-ion full cell with our designed EC-based nonflammable electrolyte with a small fraction of vinylene carbonate additive under an aggressive condition of 4.5 V charge cut-off voltage, 0.5C rate, and 45 °C exhibits increased capacity, reduced interfacial resistance, and improved performance and rate capability. A basic understanding of how a high-voltage cathode-electrolyte interface and anode-electrolyte interface are stabilized and how failure modes are mitigated by fire-preventing electrolyte is discussed.

The formation of a robust solid electrolyte interphase (SEI) layer at the surface of graphite anode via electrolyte control is a key technology for high performance of lithium-ion batteries. Despite propylene carbonate (PC) offers like lower melting point over ethylene carbonate, its combination with graphite anode without additive is the worst choice, due to co-intercalation of PC and Li + ion into graphite, exfoliation of graphene sheets and death of a battery. Herein, we report for the first time unprecedented high initial coulombic efficiency of 94% and closely theoretical capacity of graphite anode, and excellent capacity retention 99% after 100 cycles in PC-based electrolyte system even under unusually high rate of 0.2C, which is generally attainable only at a very low rate below 0.05C in commercial electrolyte. The SEI stabilization approach on graphite anode in PC-based electrolyte system provides a new avenue for high-energy and high-performance batteries in widened working temperatures. The strong correlation between anode-electrolyte interfacial stabilization and highly reversible cycling performance is clearly demonstrated.

Driven by a high demand for safe lithium-ion batteries (LIBs) with no risk of fire, we develop a nonflammable organic liquid electrolyte, which is composed of 1 M lithium hexafluorophosphate salt a...

The structural design and synthesis of sulfur-carbon composite materials with high performance is still a major challenge for rechargeable lithium-sulfur batteries. Interconnected three-dimensional frameworks comprising multi-walled carbon nanotubes, graphene, or carbon particles offer a combination of constituent advantages and can thus be used to achieve superior energy conversion and storage properties. Herein, we designed and prepared free-standing three-dimensional sulfur papers containing interconnected highly conductive carbon materials, which enable to be flexible binder-free cathodes for Li-S batteries. The resultant sulfur-carbon composite paper cathode exhibited high reversible specific capacity of 1386 mAhg−1, good rate capability up to 5C, and excellent cycling performance (a capacity retention 68% after 400 cycles), all of which are significantly improved from those of bare sulfur cathode or sulfur-GO composite only. Rational design of cathode composition, structure, and a simple fabrication process can give insight into the development of various advanced cathode materials for high-performance Li-S batteries.

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.

Magnesium silicide (Mg2Si) is a new anode material candidate for Mg‐ion batteries due to the Earth‐abundance of Mg and Si and its high theoretical specific capacity of 1398 mAh/g. However, to date, no one reported its reversible Mg‐storage ability. Herein, we demonstrate for the first time the experimental visualization of a reversible electrochemical demagnesiation and magnasiation of Mg2Si film model electrode in a half‐cell with the electrolyte of PhMgCl/THF at room temperature. The Mg2+‐diffusivity, 1.3 × 10–18 cm2/s, of Mg2Si film model electrode determined with cyclic voltammetry is four orders of magnitude lower than that of Li+‐diffusivity of Mg2Si film electrode in a lithium cell, indicating a sluggish diffusion kinetics. Surface chemistry studies of the 1st discharged (demagnesiated) and the 1st cycled (re‐magnesiated) electrodes utilizing X‐ray photoelectron spectroscopy reveal that the surface of pristine Mg2Si is highly covered by various silicon oxides, and Mg2Si undergoes segregation and phase separation partly to Mg and Si along with the surface coverage of electrolyte decomposition products. Those events lower the homogeneity and connectivity of electrode composition, which limits the reaction reversibility. The data give insight into a new material design for Mg‐ion batteries.

With increased energy density of rechargeable lithium-ion batteries for powering smart phones and electric vehicles and for their long range use, battery safety becomes more important than ever. This aspect motivated us to develop non-flammable liquid electrolyte that removes the risk of battery fire and explosion, which is urgently needed. Battery energy density and performance however should not be sacrificed to achieve just the safety. Here we report for the first time a rational design of non-flammable carbonate-based organic liquid electrolyte to satisfy safety, energy density and performance simultaneously. Our novel electrolyte, composed of 1 M lithium hexafluorophosphate salt and propylene carbonate and fluorinated linear carbonate co-solvents, at unmeasurable flash point does not fire representing non-flammable safe batteries but permits high-voltage stability to enable high-voltage charge of lithium-rich layered oxide cathode up to 5.0 V, high-energy density of 856 Wh per kg of cathode active mass and stable charge-discharge cycling performance of full-cell with graphite anode, in contrast to rapid performance fade of flammable conventional electrolyte system. The discovery of non-flammable carbonate-based organic liquid electrolyte opens up a new avenue to high-safety and high energy-density lithium-ion batteries for electric vehicles and advanced energy-storage applications.

Rechargeable lithium–sulfur (Li–S) batteries have drawn significant attention as next-generation energy storage systems. Sulfur-copolymers are promising alternative cathode materials to elemental sulfur in Li–S batteries as they provide high reversible capacity. However, the redox mechanisms of these materials are not well understood owing to the difficulty in characterizing amorphous structures and identifying individual ionic species. Here, we use solid-state NMR techniques together with electrochemistry experiments and quantum calculations to investigate the structural evolution of the prototype S-copolymer cathodes, sulfur–diisopropenylbenzene copolymers (poly(S-co-DIB)), during cycling. We demonstrate that polysulfides with different chain lengths can be distinguished by 13C and 7Li NMR spectroscopy, revealing that the structure of the copolymers can be tuned in terms of polysulfide chain lengths and resulting reaction pathways during electrochemical cycling. Our results show that the improved cyclab...

We report a promising approach to achieve the maximum capacity (>230 mA h g−1) and high capacity retention (95% during 100 cycles) of a nickel-rich cathode of LiNi0.8Co0.1Mn0.1O2 (NCM811) by charging to 4.5 V in a non-flammable electrolyte of propylene carbonate and fluorinated linear carbonates. Our electrolyte permits the stabilization of the cathode–electrolyte interface and cathode structure at high-voltage, enabling stable and safe operation of the Ni-rich cathode for high-energy density and high-safety lithium-ion and lithium metal batteries.

The demand for eco-friendly and renewable resources has dramatically increased in scientific and technological areas including energy storage systems and production of new functional materials. Sulfur copolymers with high sulfur contents of up to 90 wt% were prepared via inverse vulcanization from environment-friendly, sustainable raw materials: cost-effective waste-product elemental sulfur and eugenol allyl ether (EAE), which is obtained from clove oil. The thermal properties and electrochemical activities of the resulting poly(S-co-EAE) materials can be tuned by controlling the EAE : S feed ratio. Employed as a cathode material in Li–S batteries, the copolymer with 90 wt% sulfur content provides good cycling stability at a capacity of ∼650 mA h g−1 and high Coulombic efficiencies (>99%) over 100 cycles.

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.

The effects of lithium bis(fluorosulfonyl)imide, Li[N(SO2F)2] (LiFSI), as an additive on the low-temperature performance of graphite‖LiCoO2 pouch cells are investigated. The cell, which includes 0.2M LiFSI salt additive in the 1M lithium hexafluorophosphate (LiPF6)-based conventional electrolyte, outperforms the one without additive under -20 °C and high charge cutoff voltage of 4.3 V, delivering higher discharge capacity and promoted rate performance and cycling stability with the reduced change in interfacial resistance. Surface analysis results on the cycled LiCoO2 cathodes and cycled graphite anodes extracted from the cells provide evidence that a LiFSI-induced improvement of high-voltage cycling stability at low temperature originates from the formation of a less resistive solid electrolyte interphase layer, which contains plenty of LiFSI-derived organic compounds mixed with inorganics that passivate and protect the surface of the cathode and anode from further electrolyte decomposition and promotes Li+ ion-transport kinetics despite the low temperature, inhibiting Li metal-plating at the anode. The results demonstrate the beneficial effects of the LiFSI additive on the performance of a lithium-ion battery for use in battery-powered electric vehicles and energy storage systems in cold climates and regions.

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.

Recently, researchers are devoted to develop all-solid-state batteries based on solid electrolytes such as polymers, sulfides, oxide ceramics that can provide improved thermal stability and safety than conventional lithium-ion batteries based flammable organic liquid electrolyte. However, solid electrolytes faces to challenge lower ionic conductivity and interfacial contact problem between cathode and electrolyte, which causes large interfacial resistance. In this presentation, we report the fabrication of polymer-based all-solid-state batteries with high-nickel LiNi0.8Co0.1Mn0.1O2 cathode, attainment of high areal capacity ~1.5 mAhcm-2 and improvement of cycling performance using additive combination. Studies of the changes in the structure and morphology of cathode and surface composition and their correlation to the performance would be discussed in the meeting. Acknowledgements This research was supported by the Korean Ministry of Trade, Industry & Energy (10080025), and Creative Human Resource Development Consortium for Fusion Technology of Functional Chemical/Bio Materials of BK Plus program by Ministry of Education of Korea.

Designing and controlling the anode–electrolyte interfacial chemistry of a micron Sn-Ni/graphite composite battery anode led to the formation of a stable solid electrolyte interphase (SEI) layer. We utilized fluoroethylene carbonate (FEC)-based electrolyte that is more interfacially compatible than an EC-based electrolyte, trimethyl phosphite electrolyte additive that reduces the attack of LiPF6-derived acidic species in the electrolyte, and the addition of a low fraction of SnF2 to anode for capturing the F anions of HF present in the electrolyte. Mechanistic surface chemistry studies using ATR FTIR and X-ray photoelectron spectroscopy revealed that the SnF2 transforms to SnF4 by capturing F anions, while FEC and phosphite provide a surface protective and robust SEI. The interfacially controlled composite anode with a tuned content of graphite exhibits good cycling stability (90% retention at the 50th cycle) with high discharge capacity of ∼800 mAhg−1 of tin, in contrast to a rapid capacity fade in the conventional electrolyte. © 2014 The Electrochemical Society. [DOI: 10.1149/2.0661412jes] All rights reserved.

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.

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.

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.

Crystalline films of WO3 were directly fabricated on alumina and zirconia ceramic substrates via a facile hydrothermal fabrication process using an aqueous peroxy-tungstate solution. The process utilized kinetically controlled decomposition reaction of the peroxy-tungstate solution to tungsten oxide following supersaturation and heterogeneous nucleation at the surface of the substrates. The films possessed remarkably different microstructures depending on the reaction conditions, but all particles were oriented normal to the substrates. X-ray diffraction, transmission electron microscopic and Raman spectroscopic data indicated that the WO3 film had a hexagonal structure and film orientation. The WO3 films showed a rapid gas response to NO2 of ppm level. The data contribute to the development of film fabrication methods of a variety of oxide gas sensing elements.

Lithium ferrite, β-LiFe 5 O 8 , fine particles with a 100–120 nm size were successfully prepared by hydrothermal ball milling at the low temperature of 170 °C for 2 h without any post annealing. The lithium ferrite fine particle formation was confirmed by characterization using XRD, SEM, XPS and magnetization measurements. The experimental results strongly support the idea that ball milling can accelerate the reaction not only between the solid and solid phases but also between the solid and liquid phases. We believe hydrothermal ball milling can open a new era for the low temperature synthesis and fabrication of homogeneous fine particles both in composition and size.

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.

An increase in the energy density of lithium-ion batteries has long been a competitive advantage for advanced wireless devices and long-driving electric vehicles. Li-rich layered oxide, xLi2MnO3∙(1−x)LiMn1−y−zNiyCozO2, is a promising high-capacity cathode material for high-energy batteries, whose capacity increases by increasing charge voltage to above 4.6 V versus Li. Li-rich layered oxide cathode however suffers from a rapid capacity fade during the high-voltage cycling because of instable cathode–electrolyte interface, and the occurrence of metal dissolution, particle cracking, and structural degradation, particularly, at elevated temperatures. Herein, this study reports the development of fluorinated polyimide as a novel high-voltage binder, which mitigates the cathode degradation problems through superior binding ability to conventional polyvinylidenefluoride binder and the formation of robust surface structure at the cathode. A full-cell consisting of fluorinated polyimide binder-assisted Li-rich layered oxide cathode and conventional electrolyte without any electrolyte additive exhibits significantly improved capacity retention to 89% at the 100th cycle and discharge capacity to 223–198 mA h g−1 even under the harsh condition of 55 °C and high charge voltage of 4.7 V, in contrast to a rapid performance fade of the cathode coated with polyvinylidenefluoride binder.

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.

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 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.

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.

Siloxane-capped amorphous nano-SiOx/graphite was prepared by simple reduction and self-organization, and facile particle dispersion. 92% capacity retention of the composite anode is ascribed to effective accommodation of the volume change, and uniform distribution of SiOx on the graphite matrix.

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 LiFePO 4 have been prepared on stainless steel substrates with pulsed laser deposition utilizing an Ar atmosphere. Raman spectral analysis revealed the presence of carbon in the films, even though the targets contained less than a few percent residual carbon. The Raman spectra also suggest the presence of iron oxide species on the surface of the film. Though the film morphology became rough with cycling and thicker films were cleaved; the films showed good stability on cycling. The 75-nm-thick film prepared with a carbon-containing target showed a reversible cycling of more than 90 mAh/g for 60 cycles. The use of the low-carbon (

Summary form only given. Nanometer sized (/spl tilde =/ 50nm) hexagonal strontium and barium ferrite (AFe/sub 12/O/sub 19/, A=Sr, Ba) have been prepared from metal citrate complexes. X-ray absorption near edge structure and Rietveld refinement were performed in order to investigate the structural feature and the magnetic origin of magnetoplumbite type ferrite. The increase of covalency or the presence of higher oxidation state (Fe/sup 4+/) could not be observed in XANES. The peak shapes of Fe K-edge XANES spectra of hexagonal ferritte is similar to that in the spinel, Fe/sub 3/O/sub 4/. The pre-edge peak (/spl tilde =/ 7111.5 eV) with large intensity could be observed due to the coexistance of local symmetries such as octahedral, tetrahedral and trigonal bipyramidal. According to the Rietveld refinement, the Sr-ferrite has shorter bond distances and smaller cell volume than the Ba-ferrite because of the ionic size difference. The larger magnetic value (H/sub C/=6500 Oe) of Sr-ferrite might be due to the reduced Fe-O-Fe bond distance which leads to a stronger ferromagnetic coupling between the Fe/sup 3+/ ions in the lattice.

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.