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Utilization of high-voltage electrolyte additive(s) at a small fraction is a cost-effective strategy for a good solid electrolyte interphase (SEI) formation and performance improvement of a lithium-rich layered oxide-based high-energy lithium-ion cell by avoiding the occurrence of metal-dissolution that is one of the failure modes. To mitigate metal-dissolution, we explored fluorinated dual-additives of fluoroethylene carbonate (FEC) and di(2,2,2-trifluoroethyl)carbonate (DFDEC) for building-up of a good SEI in a 4.7 V full-cell that consists of high-capacity silicon-graphite composite (15 wt% Si/C/CF/C-graphite) anode and Li1.13Mn0.463Ni0.203Co0.203O2 (LMNC) cathode. The full-cell including optimum fractions of dual-additives shows increased capacity to 228 mAhg−1 at 0.2C and improved performance from the one in the base electrolyte. Surface analysis results find that the SEI stabilization of LMNC cathode induced by dual-additives leads to a suppression of soluble Mn2+-O formation at cathode surface, mitigating metal-dissolution event and crack formation as well as structural degradation. The SEI and structure of Si/C/CF/C-graphite anode is also stabilized by the effects of dual-additives, contributing to performance improvement. The data give insight into a basic understanding of cathode-electrolyte and anode-electrolyte interfacial processes and cathode-anode interaction that are critical factors affecting full-cell performance.

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.

Beyond current lithium-ion technologies, magnesium–sulfur (Mg–S) batteries represent one of the most attractive battery chemistries that utilize low cost, sustainable, and high capacity materials. In addition to high gravimetric and volumetric energy densities, Mg–S batteries also enable safer operation due to the lower propensity for magnesium dendrite growth compared to lithium. However, the development of practical Mg–S batteries remains challenging. Major problems such as self-discharge, rapid capacity loss, magnesium anode passivation, and low sulfur cathode utilization still plague these batteries, necessitating advanced material design strategies for the cathode, anode, and electrolyte. This review critically appraises the latest research and design principles to address specific issues in state-of-the-art Mg–S batteries. In the process, we point out current limitations and open-ended questions, and propose future research directions for practical realization of Mg–S batteries and beyond.

Battery safety has an ever-increasing significance and is required for consumer's safety. The high flammability of traditional organic liquid electrolyte, which consists of ethylene carbonate and highly flammable linear carbonate, is one of the major reasons for thermal runaway and battery fire events. Replacement of flammable liquid electrolyte with non-incendive one is urgently needed for safe lithium-ion batteries. A fluorinated linear sulfate paired with 1 m LiPF

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...

Demands of increased energy density and high-safety of lithium-ion and lithium metal batteries are growing for advanced electronics, electric vehicles and energy storage systems. Nickel-rich layered oxides such as LiNi0.8Co0.1Mn0.1O2 (NCM811) are appealing as promising high-capacity cathode materials. Their reversible capacity increases further by charging to higher voltages than conventional 4.2 V, which is however difficult to make because of unstable cathode-electrolyte interface and structural degradation. Herein, we report the combination of NCM811 cathode active material with non-aqueous functional polyimide binder to imparts enhanced thermal stability and highly stable interface originating from in situ building-up of surface protective polyimide layer at cathode through monodentate metal-carboxylate chemical bonds during slurry preparation, which permits to charge to 4.4 V despite in commercial electrolyte without any additive. This unique active material-binder combination not only suppresses metal-dissolution and cathode degradation and produces increased reversible capacity higher than 200 mAh g−1 but also provides unprecedented non-flammable characteristics contrary to the case of conventional binder, enabling a stable operation of higher energy and safer batteries.

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.

The needs of fast charging capability of high energy density Li-ion batteries are increasing to enable fast charge of battery-powered electric vehicles. However, not only lithium-plating event and sluggish diffusion kinetics of graphite anode but also limited diffusion kinetics of cathode hamper fast charging Li-ion batteries. Various approaches like surface coating of active materials, adopting new active materials, designing electrolytes and others are ongoing to improve high-rate performance of batteries. We have been developing a method to promote lithium diffusion kinetics of nickel-rich cathode active material through structural modification. In this presentation, we will report the effects of structural modification of NCM622 cathodes on the cycling performance under extremely fast charge conditions (4C~6C) and interfacial resistance change. Acknowledgements This research was supported by the National Research Foundation grant funded by the Ministry of Science, ICT and Future Planning (2019R1A2C1084024, 2020M3H4A3081874) of Korea.

Longer driving range electric vehicles require higher energy lithium-ion battery (LIB) than that of state-of-the-art LIBs. Therefore, the development of high capacity cathode and anode active materials beyond conventional ones is highly encouraged. Silicon (Si) as a high-capacity anode material has been studied for decades. However, still its fraction used in Si-graphite composite anode is limited to a few wt%, due to a large volume change, low electrical conductivity and unstable interface to electrolyte. Ever since the advent of the Si anode, numerous challenges such as size control, surface coating, active/inactive alloy, void space engineering, and composites have been conducted. In this presentation, we report comparative studies of electrochemical cycle behavior along with interfacial resistance changes of various silicon anode active materials and interfacial reaction behavior with electrolyte components. Acknowledgements This research was supported by the National Research Foundation grant funded by the Ministry of Science and ICT (No. 2021M3H4A3A02086211).

These days lithium-ion battery (LIB) market is rapidly expanding by electric mobilities and stationary energy storage system industries. One of the biggest challenges in the research and development of advanced LIB is to achieve simultaneously outstanding energy density, cycle life, charge rate, and safety. For fast charging, battery chemistry and reaction kinetics are being evolved from the current hours scale toward minutes scale charging. In the LIB electrolyte perspective, the conventional carbonate-based liquid electrolyte has several limitations in safety and high-rate and high-voltage performance, due to low thermal and anodic stabilities under extreme operation conditions like high temperature, high-current, and high-voltage. To mitigate those issues, we have been developing new and safe electrolyte without any trade-off with cycling performance and energy density of Li-ion batteries. Herein, we present high-rate and high-voltage cycling performance and high safety of nickel-rich cathode-based lithium-ion full-cell fabricated with nonflammable liquid electrolyte. The correlation between the stability of nonflammable liquid electrolyte and its derived solid electrolyte interphase (SEI) and performance will be discussed in this meeting. Acknowledgements This research was supported by the National Research Foundation grant funded by the Ministry of Science and ICT (No. 2019R1A2C1084024).

The effects of lithium bis(fluorosulfonyl)imide, Li[N(SO

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.

Fabrication and high-rate performance of a safe lithium ion-sulfur battery (LISB) with sulfur-copolymer [poly(S-co-divinylbenzene (DVB)] cathode having a sulfur content higher than 90 wt %, a carbon-fiber interlayer, and a prelithiated hard-carbon (Li-HC) anode are reported, which mitigates problems of lithium-sulfur cells such as performance fade and safety issues due to dissolution of polysulfides and lithium-dendrite growth. The poly(S-co-DVB) cathode offers scalability owing to the abundance and low cost of DVB. The Li-HC anode, the surface of which is passivated by a solid electrolyte interphase, inhibits the deposition of polysulfides. As a result, the LISB exhibits reversible and stable cycling performance at high rates up to 3 C, which enables quick charging within 20 min, and delivers a reversible capacity of approximately 400 mAh g-1 at 3 C for 500 cycles. The results give insight into the design principle of promising, quickly charged, and safe LISBs.

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...

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.

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.

Lithium-ion batteries (LIBs) are ubiquitous power sources and demand for higher energy and higher performance LIBs than state-of-the-art ones continues to increase for longer range use of electric mobility and energy-storage systems. Performance of conventional LIBs is often limited or failed in tough working environments, particularly, subzero-temperatures because of reduced ionic conductivity of electrolyte and diffusion kinetics of both anode and cathode, causing lithium metal plating and dendrite growth and finally safety issue and death of LIBs. Herein, for the first time we report a lithium metal plating-free and unprecedented high-performance graphite∥LiNi0.8Co0.1Mn0.1O2 (NCM811) full-cell under subzero-temperature of −10 °C and high-voltage of 4.45 V through the construction of robust solid electrolyte interphase (SEI) layers at both anode and cathode and their structural stabilization in 1 M LiPF6 and nonflammable electrolyte. Subzero-temperature operation of commercial electrolyte-based full-cell however results in a drastic performance failure in early cycles and shows distinguishing marks such as lithium metal plating at graphite anode and irreversible phase transformation of NCM811 to disordered H3 phase with a large volume contraction. The strong correlation between anode-electrolyte and cathode-electrolyte interfacial stabilization, bulk structural stabilization of both anode and cathode, and highly reversible cycling performance under subzero-temperature is clearly demonstrated.

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.

Rapidly growing interest and demand for wearable electronics require the development of flexible and lightweight all-solid-state batteries as power sources that guarantee high performance and safety with the absence of the risk of fire or explosion that can occur with traditional liquid electrolyte systems. Herein, we successfully fabricate new flexible all-solid-state microbatteries integrating a solid electrolyte film of lithium boron oxynitride (LiBON) on a flexible substrate using sophisticated thin-film fabrication technology. The new microbattery of Li/LiBON/LiCoO 2 exhibits excellent mechanical integrity even under severe bending and twisting test conditions, enabling the realization of flexible microbatteries. The microbatteries demonstrate superior electrochemical cycling stability relative to conventional batteries, delivering an outstanding capacity retention of 90% on the 1000 th cycle. Furthermore, operation at various temperatures from −10 °C to +60 °C and fast charging within 3–6 min are achieved. With various types of flexible substrates, the microbatteries can provide diverse opportunities for flexible and wearable electronics.

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.

High loading level of micron cathode active material is essential for high energy density Li-ion batteries. High loading level and thick cathode however limit not only rate capability but also cycle life, which is mainly caused by inhomogeneous current distribution from bottom (current collector side) to the top (interface side to electrolyte) of the cathode. Here we report a significant improvement of rate performance of micron LiNi0.6Co0.2Mn0.2O2 cathode material with high loading level of more than 10 mgcm−2, through simple and homogeneous dispersion and interweaving of bulk carbon fibers (CF) to active material. This microstructure permits the building-up of 3D electrical conduction network over the thick cathode. While the interwoven carbon fiber network guarantees fast electron transfer, porous characteristic of a thick cathode leads to a rapid access of Li+-ion through a good electrolyte wetting, and favorable rate capability and cycling stability. The resulting highly loaded CF-interwoven cathode achieves rate capability upto 5 C, high capacity of 163 mAhg−1 at 1 C and stable 1 C cycling performance even under an aggressive test condition between 3.0 and 4.6 V utilizing high-voltage electrolyte additive.

Elevating the charge cut-off voltage of lithium-ion battery above 4.2 V vs. Li/Li+ can increase the capacity of cathode and energy density of the battery but requires higher anodic stability of electrolyte and higher interface stability between charged cathode and electrolyte than those of the state-of-the-art commercial electrolyte. Utilization of a small fraction of high-voltage electrolyte additive is a promising and economic approach to mitigate the high-voltage stability issue. Fluorinated ethyl phosphate (FEP) is known as a flame-retardant but we examine it as a high-voltage additive of a commercial electrolyte with 1 M LiPF6 in EC:EMC (3:7 vol ratio). Herein, we report FEP-assisted performance improvement of a lithium-ion cell under high charge cut-off voltage of 4.6 V vs. Li/Li+, with reduced impedance rise. Our surface analysis results reveal that FEP additive in a graphite‖LiNi0.5Co0.2Mn0.3O2 full-cell is effective preferably on cathode over anode by forming a surface-passivating organics-rich and fluorine-rich solid electrolyte interphase (SEI) layer. We propose that the anodic reaction of FEP begins by a single electron transfer from the O atom of P − O − C to the cathode surface and forms FEP-derived SEI species. The SEI layer enables the inhibition of metal-dissolution phenomena from the cathode, evidenced by elemental analysis results on the metal species at graphite anode, leading to superior cycling performance to the full-cell with commercial electrolyte only. A basic understanding of interface stabilization pathway of the cathode via FEP additive in the lithium-ion full-cell is clearly demonstrated.

As mobile electronics and electric vehicles become essential in our lives, the specific energy density of a lithium-ion battery is one of the criteria that determines the quality of a battery and customers’ use range. Cathode is the one that primarily determines the capacity and energy density of the battery, and consists of active material, binder and carbon black. Nickel-rich layered oxides such as LiNi0.8Co0.1Mn0.1O2 (NCM811) are promising high-capacity cathode active materials, and its reversible capacity increases more by charging to higher cut-off voltages than the conventional 4.2 V. We observed that NCM811 cathode fabricated with commercial polyvinylidene fluoride binder has an unstable interface to electrolyte under high cut-off charge voltages and undergoes drastic structural changes during cycling in particular at elevated temperature, leading to capacity fade and reduced lifespan of the battery. In order to acquire a high reversible capacity and enhanced cycling performance with NCM811 cathode by mitigating the problems, we have designed an unique and functional high-voltage binder and make the combination with NCM811. In the meeting, we are going to report improved thermal stability and cycling performance of the designed binder-assisted cathode. Acknowledgement This research was supported by the Ministry of SMEs and Startups (S2788978) of Korea, National Research Foundation grant funded by the Korean 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.

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.

Lithium-rich layered oxide, xLi2MnO3·(1-x)LiMO2 (M = Mn/Ni/Co), is a promising high-capacity cathode active material for high-energy density rechargeable lithium batteries. While the capacity of lithium-rich layered oxide cathode can increase by increasing the charge cut-off voltage toward 5 V, it t relies on the anodic stability of electrolyte and the interface stability of charged cathode. We have been developing and suggesting fluorinated carbonates as effective high-voltage additives and solvents of new designed electrolytes, which provide a significant improvement in the stability of cathode-electrolyte interface, solid electrolyte interphase (SEI) layer and cycling performance, and longer life span of various high-capacity cathodes, with respect to commercial electrolyte system. Herein, we present our recent progress on the exploration of the limit of anodic stability of fluorinated carbonate-assisted electrolyte toward 5 V level and the capacity of a Li-rich cathode based full-cell, and the enhancement of battery safety. The mechanistic studies utilizing systematic spectroscopic analyses on the correlation among interfacial processes, the SEI formation and stabilization, and performance improvement would be discussed in the meeting. Acknowledgements This research was supported by the Ministry of Trade, Industry and Energy (A0022-00725) and the National Research Foundation grant (2019R1A2C1084024) funded by the Ministry of Science and ICT of Korea.

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 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

Advanced SiO2–carbon composite anode active material for lithium-ion battery has been synthesized through a simple chelation of silicon cation with citrate in a glyme-based solvent. The resultant composite material demonstrates a homogeneous distribution of constituents over the submicron particles and a unique hollow spherical microstructure, which provides an enhanced electrical conductivity and better accommodation of volume change of silicon during electrochemical charge–discharge cycling, respectively. As a result, the composite electrode exhibits a high cycling stability delivering the capacity retention of 91% at the 100th cycle and discharge capacities of 662–602 mAh/g and coulombic efficiencies of 99.8%. This material synthesis is scalable and cost-effective in preparing various submicron or micron composite electrode materials.

For lithium intercalation battery electrodes, understanding of the electronic structure of bulk and surface is essential for their operation and functionality. Soft X-rays are excellent probes for such electronic structure information, but soft X-rays are predominantly surface sensitive and thus cannot probe the bulk. Moreover, soft X-rays hardly permit meaningful in situ and operando studies in battery assemblies. We show here how we penetrate with hard X-rays (>10 keV) in situ a lithium cell, containing a manganite-based cathode. Through X-ray Raman spectroscopy we extract the Mn 2p multiplet from the entire cathode material, thus obtaining bulk-sensitive electronic structure information during battery charging and discharging.

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.

The interfacial origin of performance improvement and fade of high-voltage cathodes of LiNi0.5Co0.2Mn0.3O2 for high-energy lithium-ion batteries has been investigated. Performance improvement was achieved through interfacial stabilization using 5 wt % methyl (2,2,2-trifluoroethyl) carbonate (FEMC) of fluorinated linear carbonate as a new electrolyte additive. Cycling with the FEMC additive at 3.0–4.6 V versus Li/Li+ results in the formation of a stable solid electrolyte interface (SEI) layer and effective passivation of cathode surface, leading to improved cycling performance delivering enhanced discharge capacities to 205–182 mAhg–1 and capacity retention of 84% over 50 cycles. The SEI layer notably includes plenty of metal fluorides and −CF-containing species formed by additive decomposition. On the contrary, the origin of performance fade in electrolyte only was ineffective surface passivation and dissolution of metal elements, which leads to oxygen loss, surface structural degradation and crack format...

Increasing needs of electric vehicles and grid-based energy storage systems for the reduction of carbon dioxide gases require higher energy density lithium (Li)-ion batteries than commercial batteries. The energy density of Li-ion batteries can increase by increasing the specific capacity of cathode material, which can increase by raising the charge cut-off voltage. Among various cathode materials, nickel-rich layered oxides of Li(Ni1 –x –y Co x Mn y )O2 (NCM, 1–x–y ≥ 0.5) are promising high-capacity cathode materials for high-energy density Li-ion batteries because of higher capacity and lower cost than nickel-lean oxides. However, the limited anodic instability of the conventional carbonate-based organic electrolytes at the voltage higher than 4.2 V versus Li/Li+ and instability of cathode-electrolyte interface at highly charged state makes high-voltage charge of nickel-rich oxide cathode difficult. In order to mitigate the electrolyte and interface issues, we have been developing new functional electrolytes that provides high anodic stability above 4.3 V and highly stable cathode-electrolyte interface. High-voltage electrochemical and interfacial reaction studies and their correlation to cycling performance would be discussed in the meeting. Acknowledgements: This research was supported by Ministry of Trade, Industry & Energy (R0004645) and Creative Human Resource Development Consortium for Fusion Technology of Functional Chemical/Bio Materials of BK Plus program by Ministry of Education of Korea.

Solid-state battery based on solid polymer electrolyte has been long studied as one of the most potential solid-state systems because of its improved thermal stability and safety compared to conventional lithium-ion batteries based on carbonate-based liquid electrolyte. Challenges to improve ionic conductivity and interfacial contact between electrode and electrolyte for lowered interfacial resistance however remain. We have been developing various functional additives for lowering the interfacial resistance, in particular, between cathode and polymer electrolyte, and made some progress in enhancing the areal capacity and cycling performance at 45 oC. Herein, we report the fabrication of solid-state lithium metal batteries with PEO-based polymer electrolyte and nickel-rich LiNi1-x-yCo x Mn y O2 cathode, and the attainment of areal capacity higher than ~1.0 mAhcm-2 and enhancement of cycling performance using effective additives. Additive-dependent ex situ analysis results of crystal structure and surface composition of cathode active material would be presented. 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.

Rechargeable Mg battery is one of the most attractive candidates among the next-generation batteries because of the abundance, good safety and high volumetric capacity (3383 mAhcm-2) of magnesium. Despite its advantages, commercialization of Mg metal battery has been hindered by critical issues such as the formation of surface blocking layer on Mg metal anode and the limited selection of cathode material against Mg metal anode and electrolyte. Recently, we reported that Mg2Sn has a great potential as a Mg2+-insertion type anode for enabling an Mg-ion battery with high theoretical capacity (641 mAhg-1). The low working voltage (~0.2V versus Mg/Mg2+) of Mg2Sn anode gives a big advantage to obtain a high cell voltage in the full-cell with an Mg-free cathode. However, challenges to overcome low capacity in early cycles remain, even though Mg2Sn anode delivered a high reversible capacity in half-cell. Herein, we report the control of anode-electrolyte interfacial reaction during initial cycles of half-cell through the formation process and resultant improvement of cycling performance. Mechanistic studies of how the formation process influences structure, surface properties and particle morphology of Mg2Sn anode would be discussed. Preliminary cycling ability of full-cell with Mg2Sn anode combined with Mg-free cathode would be presented. Acknowledgments This work was supported by National Research Foundation of Korea (2015062107) and Creative Human Resource Development Consortium for Fusion Technology of Functional Chemical/Bio Materials of BK Plus program by Ministry of Education of Korea.

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.