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Lithium metal batteries (LMBs) represent the most promising next‐generation high‐energy density batteries. The solid electrolyte interphase (SEI) film on the lithium metal anode plays a crucial role in regulating lithium deposition and improving the cycling performance of LMBs. In this review, we comprehensively present the formation process of the SEI film, while elucidating the key properties such as electronic conductivity, ionic conductivity, and mechanical performance. Furthermore, various approaches for constructing the SEI film are discussed from both electrolyte regulation and artificial coating design perspectives. Lastly, future research directions along with development recommendations are also provided. This review aims to provide possible strategies for the further improvement of SEI film in LMBs and highlight their inspiration for future research directions. [ABSTRACT FROM AUTHOR]

This study investigates the use of lanthanide elements to modify a layered oxide cathode through solid-state calcination. Based on the findings, the modified cathodes demonstrated enhanced electrochemical performance, as lanthanide modification played dual roles in doping and coating. Some lanthanide ions entered the cathode lattice, expanding Li+ diffusion channels and stabilizing the crystal structure, while others formed a coating layer to prevent direct contact with the electrolyte and suppress undesirable side reactions. The Eu-modified cathode showed superior initial Coulombic efficiency, capacity retention, and rate ability, which can be attributed to the low dissociation energy that accelerated Eu ion entry into the cathode lattice, improving its structural stability. The Eu-modified LNCM increased Coulombic efficiency from 81.9 to 88.9%. More importantly, the data show that the modified electrode has better magnification performance and it is more stable after several cycles. This research provides new insights into the use of lanthanide modification to improve the performance of oxide cathodes, which could potentially be applied to other battery systems. [ABSTRACT FROM AUTHOR]

Phosphonium cation-based ionic liquids (phosphonium ILs) have several advantages for electrochemical device applications compared with ammonium cation-based ionic liquids because of their unique features, such as higher ionic conductivity and a larger electrochemical potential window. In this study, we prepared various phosphonium ILs with different substituents (alkyl, alkyl ether, or allyl) on the cation, and bis(fluorosulfonyl)amide (FSA) or bis(trifluoromethanesulfonyl)amide (TFSA) as the anion. This study describes these phosphonium ILs used as electrolytes for lithium-ion batteries and investigates their performance as typical Li/LiCoO 2 cells. We demonstrate that discharge capacity increases with increasing lithium-ion conductivity determined by electrochemical impedance and pulsed-field gradient nuclear magnetic resonance. A discharging rate test conducted in constant current (CC) mode also displays good high conductivity phosphonium IL electrolyte performance. Furthermore, the difference in cycle performance between FSA-based and TFSA-based phosphonium IL electrolytes is explained in terms of solid electrolyte interphase formation, similar to the performance of other cation-based ILs. [Display omitted] [ABSTRACT FROM AUTHOR]

The construction of stable cathode electrolyte interphase (CEI) is the key to improve the NCM811 particle structure and interfacial stability via electrolyte engineering. In He's work, lithium hexamethyldisilazide (LiHMDS) as the electrolyte additive is proposed to facilitate the generation of stable CEI on NCM811 cathode surface and eliminate H2O and HF in the electrolyte at the same time, which boosts the cycling performance of Li||NCM811 battery up to 1000 or 500 cycles with 4.5 V cut-off voltage at 25 or 60 °C. [ABSTRACT FROM AUTHOR]

The employment of electrolyte-film forming additive is a facile and effective strategy to improve the cycling performance of aggressive Nickel-rich layered oxide cathode LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811) cathode for high energy lithium-ion batteries (LIBs). Here we report a homogeneous and dense polymer cathode-electrolyte-interface (CEI) film generated via in-situ electrooxidation polymerization of 1, 3-Dioxolane (DOL) in a conventional carbonate-based electrolyte. It is found that the electrolyte modification with 15% DOL is the most effective in balancing the interfacial stability and Li-ion diffusion kinetics of NCM811 cathode, while also achieving its comparable rate capability and greatly improving cycling performance. Morphological and elemental characterizations demonstrate that the 15% DOL-derived CEI layer not only alleviates the impacts of harmful interfacial reactions and hinders the particle disintegration, but also suppresses the irreversible lattice transition of the NCM811 cathode surface to the inactive rock salt phase. Moreover, it is proved that the F-rich interfacial layer displays excellent Li-ion transport kinetics. As a result, the cell exhibits high capacity retention of 85.2% and 78.1% after 200 cycles at cut-off voltages of 4.3 V and 4.5 V at 1 C in the 15% DOL-modified electrolyte. Therefore, creating a stable and effective Li-ion conductive interfacial protective film on the cathode surface by optimizing an electrolyte functional additive is an economical and available approach to develop the highly stabilized Ni-rich cathode for high-energy LIBs applications. [Display omitted] • Surface modification of LiNi 0.8 Co 0.1 Mn 0.1 O 2 cathode was achieved by coating layer. • The cathode with polydioxolane showed enhanced electrochemical performance. • The coating layer serves as protective layer and good conductor of ion diffusion. [ABSTRACT FROM AUTHOR]

Abstract An electrolyte composed of lithium difluoro(oxalate)borate (LiDFOB) as lithium salt, N-propyl-N-methylpiperidinium bis(trifuoromethansulfonyl) imide (PP 13 TFSI) ionic liquid and dimethylcarbonate (DMC) as co-solvent and fluoroethylene carbonate (FEC) as additive is reported in this study. It is found that the resulted ionic liquid-based electrolyte demonstrates high ionic conductivity, low polarization and high safety performance. The Li/Li 1.1 Ni 0.25 Mn 0.65 O 2 and Li/Graphite half-cells with the electrolyte exhibit excellent electrochemical performance, retaining capacities of more than 186 mA h g−1 and 361.6 mA h g−1 after 100 cycles, respectively. Such outstanding energy storage performance is ascribed to the joint oxidative decomposition of LiDFOB and FEC, which can form stable and low impedance solid electrolyte interface (SEI) on the Li-rich cathode and graphite anode. Besides, the SEI layer can prevent transition metal dissolution, enabling excellent cycling stability for the high voltage graphite/Li 1.1 Ni 0.25 Mn 0.65 O 2 full cell. As a result, the full cell with the ionic liquid based electrolyte maintains a discharge capacity and capacity retention of 180 mAh g−1 and 87.54% after 100 cycles at 0.5 C and 40 °C, far superior to that obtained for commercial electrolyte. All these characteristics make the electrolyte a promising candidate for safe, high performance lithium-ion battery electrolyte. [ABSTRACT FROM AUTHOR]

Abstract The growth of zinc dendrites during cycling has constrained the development of the silver-zinc batteries. Herein, we focus on the practical application of polyethylene glycol with molecular weight of 200 as an electrolyte additive to the silver-zinc batteries. The cycleability of the batteries was significantly improved by introducing proper amount PEG-200 into the alkaline electrolyte. Further study shows that adding PEG-200 as electrolyte additive can effectively maintain the structure of the zinc electrode, and clearly inhibit the growth of zinc dendrites. At the same time, silver electrodes are not sensitive to the PEG-200 addition. [ABSTRACT FROM AUTHOR]

The capacities fade of manganese oxide originating from the well-known Mn dissolution in electrolyte. Suppressing the dissolution of Mn elements can result in a significant enhancement of the cycling performance of anode materials. Surface coating of active material is one of the most effective strategies, especially; aluminum oxide is most widely adopted coating material to improve anode materials performance. Here we report, Al 2 O 3 layer is coated on the surface and little Al-ions are diffused into MnO electrode prevents dissolution of manganese elements in electrolyte, decrease capacity fade and maintain structure stability of the active material. MnO@Al 2 O 3 composite electrode delivers an initial discharging/charging capacities of 1390/822 mA h g −1 at current rate of 100 mA g −1 and maintains high reversible charging capacity of 855 mA h g −1 after 100 cycles. Al 2 O 3 coating prevents decomposition of manganese oxide in electrolyte and enhances the cycling stability. [ABSTRACT FROM AUTHOR]

Lithium difluoroborate (LiDFOB), lithium bis(oxalato)borate (LiBOB), lithium difluoro(oxalato)borate (LiDFBOP) and lithium difluorophosphate (LiPF2O2) are investigated as electrolyte additives to alleviate the severe cycle capacity fading of spinel LiMn2O4 cathode of lithium-ion batteries, especially at elevated temperatures. Compared with that of the routine electrolyte, the capacity retention is significantly improved at both room temperature and 55 °C by adding LiBOB and LiDFOB as electrolyte additives. Moreover, surface layer formation processes on the LiMn2O4 electrode in the presence of the LiBOB, LiDFOB, LiDFBOP and LiPF2O2 are investigated by photoelectron spectroscopy (XPS) and X-ray diffraction. According to the analysis results, BOB− anions from LiBOB or LiDFOB bond with the dissolved Mn2+ to form an insoluble and stable surface layer on the LiMn2O4 surface, which is beneficial to the suppression of the LiMn2O4 dissolution and electrolyte decomposition, and eventually to the improvement of the cycling performance at elevated temperatures.Graphical abstract: [ABSTRACT FROM AUTHOR]

Nanostructure-LiNi 1/3 Co 1/3 Mn 1/3 O 2 (NCMa) has been successfully synthesized via a facile chemistry method using a cheap chelating agent of acetic acid. The NCMa has low cation mixing between Li + and Ni 2+ and exhibits a diameter of 100–300 nm. Specifically, the as-prepared particles NCMa with unique nano structure can increase the contact area with electrolyte, shorten Li + diffusion path and thus improve the Li + mobility. In addition, to reduce the adverse effect caused by NCMa, lithium bis(oxalate)borate (LiBOB) instead of LiPF 6 has been used as electrolyte salt to enhance the cycling of NCMa, due to the fact that LiBOB will generate relatively little acid in electrolyte. Furthermore, it is interest to note that LiBOB leads to forming a relative stable passivation film on the surface of NCMa cathode. Hence, compared with LiPF 6 , NCMa will generate remarkable electrochemical lithium storage properties in terms of high capacity, excellent rate capability and ultrastable long-term cycling performance. [ABSTRACT FROM AUTHOR]

[Display omitted] • PEO-based polymer-in-salt electrolytes are made by a facile coating process. • Rich hydrogen bonds are formed in polymer network for better structural stability. • High content of free Li+ and restricted anion movement obtain a high t Li + of 0.639. • Inhibition of Li dendrites renders Li/Li cells cycling over 3000 h at 0.2 mA cm−2. • The electrolytes boost the performances of LMBs using LFP or NCM88 significantly. Polyethylene oxide (PEO)-based solid polymer electrolyte (SPEs) is full of attraction due to its exceptional lithium ion dissolubility and strong resistance toward lithium metal reduction. Nevertheless, it still suffers from the unfulfilling room temperature ionic conductivity and poor mechanical properties. Herein, a flexible and robust polymer-in-salt electrolyte based on composite of polybenzimidazole (PBI) and PEO via a facile preparation approach has been developed for room-temperature lithium metal batteries (LMBs). The rigid framework structure of PBI and dense hydrogen bonds formed between PBI and PEO jointly reinforce the structural stability of SPEs at high lithium salt concentration, which makes the SPEs possess sufficient mechanical properties to resist the lithium dendrites growth. The thermal stability and fire resistance of SPEs have also been improved relying on the distinctive flame retardancy and incombustibility of PBI. Besides, PBI is prone to forming hydrogen bonds with lithium salt anions to limit their mobility, while the rich N atoms on PBI chains can promote the dissociation of lithium salt through electrostatic attraction interaction. Their synergistic effects make the PEO-based polymer-in-salt electrolytes achieve the high room temperature ionic conductivity of 5.7 × 10−4 S cm−1, wide electrochemical window of 4.45 V, and large lithium transference number of 0.639. When applied to LMBs with LiFePO 4 or LiNi 0.88 Co 0.06 Mn 0.06 O 2 cathode, both coin cells exhibit improved cycling performance and rate capability. Furthermore, the LiNi 0.88 Co 0.06 Mn 0.06 O 2 /SiO x -C pouch cells using the SPEs demonstrate remarkable flexibility and safety, clarifying that the PEO-based polymer-in-salt electrolytes possess a promising application prospect for safe and high-performance LMBs. [ABSTRACT FROM AUTHOR]

(Phenoxy)Pentafluorocyclotriphosphazene N 3 P 3 (OPh)F 5 (PFPN) is investigated as a bifunctional additive in electrolyte to improve the electrochemical performance and thermal stability of LiCoO 2 simultaneously when the electrodes cycled to high cutoff potentials. The results show that the electrochemical performance of the electrode material with the additive in the electrolyte is enhanced significantly, with a capacity retention of 91% after 300 cycles, which is a great improvement compared with that of only 67% in base electrolyte. More significantly, the thermal stability of Li x CoO 2 ( x < 0.5) in the presence of PFPN or covered with decomposed products of PFPN is also remarkably improved. Our results show that the additive can be oxidized prior to EC and DMC, and the decomposition products of PFPN contribute to the LiCoO 2 /electrolyte interphase film (CEI) with more uniform and denser structure. This polymerized CEI processes an excellent electrochemical stability to assist in inhibiting the further decomposition of the electrolyte and reducing the interfacial impedance growth apparently of the cells with a long cycling condition. [ABSTRACT FROM AUTHOR]

Lithium-ion cells based on Graphite/LiFePO (C/LFP), LiTiO/LiFePO (LTO/LFP) and LiTiO/LiNiMnCoO (LTO/NMC), using [CCIm][NTf]- and [CCCIm][NTf] ( n = 4 and 6)-based electrolytes with different lithium salts such as Li[N(SOCF)] (LiNTf), Li[N(SOF)] (LiFSI) and LiPF were tested at 333 K and compared to a commercial carbonate-based electrolyte [EC:DEC][LiPF]. The impact of different factors such as length of side-alkyl chain on imidazolium ring or its C substitution with CH group was studied, and the influence of the presence of organic additives as well as the value of the nominal voltage of the systems, was also reported. Finally, common trends for all these IL-based electrolyte systems were discussed. [ABSTRACT FROM AUTHOR]

A novel composite electrolyte membrane (CEM), consisting of a viscous PEGMEM-co-SMA copolymer, lithium salt and cellulose matrix, has been prepared as a new class of electrolyte for high performance lithium-ion batteries (LIBs). This CEM exhibits a wide electrochemical stability window (>5 V vs. Li/Li + ), reasonably high ionic conductivity and thermal stability up to 315 °C. At temperature above the melting temperature (31.98–35.71 °C), the viscous flow nature of the copolymer is beneficial to fully infiltrate the electrode materials like liquid electrolyte to maintain uniform contact with electrode surfaces during charge/discharge process. The interfacial resistance ( R intf ) of the fresh cell based on this CEM is extremely low (3.8 Ω cm −2 ) and the Li/LiFePO 4 cell deliveries a discharge capacity as high as 156.9 mA h g −1 with a current density of 1 C at 80 °C. It is anticipated that this work provides a new insight for designing advanced electrolyte materials for LIBs with enhanced interfacial contact and excellent cycling performance. [ABSTRACT FROM AUTHOR]

In this study, Ta single-doped Li 6.4 La 3 Zr 1.4 Ta 0.6 O 12 (Ta 0.6) and a series of Ta, Sr co-doped Li 6.4+x La 3-x Sr x Zr 1.4 Ta 0.6 O 12 (Ta 0.6 Sr x , x = 0.1, 0.2, 0.3, and 0.4) electrolytes are synthesized via a two-step process. The XRD result reveals that all samples have a pure cubic phase, which indicates that Ta5+ and Sr2+ can enter the lattice of LLZO and stabilize the cubic phase. The SEM images exhibit that all samples have a dense microstructure and tight grain boundary without obvious holes. The excellent properties are achieved when the doping amount of Sr reaches 0.2 mol. Among all designed samples, the Ta 0.6 Sr 0.2 has the highest Li+ conductivity and relative density of 8.54 × 10−4 S cm−1 and 98.79%, respectively, as well as the lowest activation energy roughly 0.302 eV. Additionally, the symmetrical cell's galvanostatic cycling data show that it has excellent cycling performance and extremely low overpotentials even after 350 cycles, indicating that it can be successfully applied to next-generation all-solid-state lithium-ion batteries (ASSLIBs). • A novel Ta, Sr co-doping strategy was adapted to synthesis ceramic electrolyte. • The sample Ta 0.6 Sr 0.2 exhibited a high ionic conductivity of 8.54 × 10−4 S cm−1. • The sample Ta 0.6 Sr 0.2 revealed a high relative density of 98.79%. • The symmetrical cell showed a brilliant cycling performance (total 350 cycles). • The electrochemical window of sample Ta 0.6 Sr 0.2 was up to 5 V. [ABSTRACT FROM AUTHOR]

Cathode materials LiNiMnO and LiNiLaMnO ( x = 0.04, 0.1, 0.14) were successfully prepared by the sol-gel self-combustion reaction (SCR) method. The X-ray diffraction (XRD) patterns indicated that, a few of doping La ions did not change the structure of LiNiMnO material. The scanning electronic microscopy (SEM) showed that the sample heated at 800°C for 12 h and then annealed at 600°C for 10 h exhibited excellent geometry appearance. A novel electrolyte system, 0.7 mol L lithium bis(oxalate)borate (LiBOB)-propylene carbonate (PC)/dimethyl carbonate (DMC) (1: 1, v/v), was used in the cycle performance test of the cell. The results showed that the cell with this novel electrolyte system performed better than the one with traditional electrolyte system, 1.0 mol L LiPF-ethylene carbonate (EC)/DMC (1: 1, v/v). And the electrochemical properties tests showed that LiNiLaMnO/Li cell performed better than LiNiMnO/Li cell at cycle performance, median voltage, and efficiency. [ABSTRACT FROM AUTHOR]

Highlights: [•] Fluorine doping leads to crystal growth and increases tap density. [•] Fluorine doping enhances the cycling performance of lithium-rich cathode material. [•] Surface fluorine modification similarly improves the cycling performance. [•] Stabilized electrode/electrolyte interface contributes to the improved cycling stability. [Copyright &y& Elsevier]

Abstract: This study demonstrates that tris(trimethylsilyl)borate (TMSB) additive in the electrolyte can dramatically improve the cycling performance of LiNi0.5Co0.2Mn0.3O2/graphite cell at higher voltage operation. And the effects of this additive are characterized by linear sweep voltammetry (LSV), electrochemical impedance spectroscopy (EIS), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). In the voltage range of 3.0–4.4 V, LiNi0.5Co0.2Mn0.3O2/graphite cell with TMSB in the electrolyte retains about 92.3% of its initial capacity compared to the cell without additive in the electrolyte that retains only 28.5% of its initial capacity after 150 cycles, showing the promising prospect of TMSB at higher voltage. The enhanced cycling performance is attributed to the thinner film originated from TMSB on the LiNi0.5Co0.2Mn0.3O2 and the combination of TMSB with PF6 − and F− in the electrolyte, which not only protects the undesirable decomposition of EC solvents but also results in lower interfacial impedance. [Copyright &y& Elsevier]

The effect of different membranes and aluminum current collectors on the initial coulombic efficiency of LiNiMnO/Li was investigated, and the cycling performance at different rates and temperatures and the storage performance at 60 °C for a week are discussed for LiNiMnO/Li. The results show that the lower initial coulombic efficiency is associated with the lower decomposition voltage of the commercial membrane and electrolyte, and the instability of aluminum current collector under the higher voltage. In addition, both versions of LiNiMnO can deliver about 115 mA h g of initial discharge capacity at 1 C at 25 °C and 60 °C; however, it retains only 61.57 % of its initial capacity after the 130th cycles at 60 °C, which is much lower than the 94.46 % rate observed for LiNiMnO at 25 °C, and the cycling performance of the material at 1 C is better than that at 0.5 C. Meanwhile, the initial discharge capacity at 0.1 C after storing at 60 °C is 119.3 mA h g, which is only a little lower than 121.5 mA h g recorded before storing; moreover, the spinel structure and surface state of LiNiMnO after storing at 60 °C has not been changed basically. These results indicate that the electrochemical stability of electrolyte is also related to the temperature. The serious capacity fading of LiNiMnO at 60 °C is attributed to the severe oxidation decomposition and the thermal decomposition in the range of cut-off voltage of the materials, and then the decomposition products interact with active materials to form a solid interface phase, leading to the larger electrode polarization and irreversible capacity loss. Meanwhile, the worse cycling performance at 0.5 C than that at 1 C is attributed to the longer interaction time between the electrolyte and the active materials. However, the storage performance of LiNiMnO corresponds to the thermal stability of electrolyte to a certain extent. [ABSTRACT FROM AUTHOR]

Abstract: The markedly enhanced cycling performance of a LiCoPO4/C cathode was observed in a 1M LiPF6 in fluoroethylene carbonate (FEC)/dimethyl carbonate (DMC) electrolyte solution compared to 1M LiPF6 in ethylene carbonate (EC)/DMC electrolyte solution. Further improvement was achieved by the addition of 0.5–1% of trimethylboroxine (TMB) additive to the electrolyte solution. The capacity retention of the LiCoPO4 electrode in this electrolyte is 90% with a faradaic efficiency of 98% after 100cycles. [Copyright &y& Elsevier]

Abstract: The charge/discharge, electrochemical impedance, cyclic voltammogram, and cycling behaviors of crystalline K x MnO2·nH2O as cathode material for supercapacitors in Li2SO4, Na2SO4, and K2SO4 electrolytes were compared. The different power and cycling performance of K x MnO2·nH2O during charge/discharge in the three electrolytes were elucidated by analyzing its composition and structure evolution. Compared with the Li2SO4 and Na2SO4 electrolytes, the highest ionic conductivity of K2SO4 electrolyte, the fastest charge-transfer process and slightest structural evolution of K x MnO2·nH2O during charge/discharge in the K2SO4 electrolyte lead to a superior power and cycling behavior for supercapacitor application. [Copyright &y& Elsevier]

Abstract: LiNi1/3Co1/3Mn1/3O2 (NCM) cathode has wide operation voltage window. Dissolution behavior of the NCM cathode at different charge states in 1M LiPF6/EC:DEC (1:1) electrolyte is determined with inductively coupled plasma (ICP) technique. Electrochemical cycling performance of the NCM-based cells in the electrolyte with different charge voltage limits is correlated with the dissolution of the active material. With increasing charge voltage limit, specific capacity and energy density of the electrode are significantly enhanced. However, cycle life of the cell based on NCM cathode and meso-carbon micro-bead (MCMB) anode is compromised at cutoff voltages >4.3V. Mechanisms of the capacity decay for the full cell cycled with high charge voltage limit are investigated. Impedance rise of the graphite anode, which is resulted from deposition of the dissolved metal ions from the NCM cathode, is specified to be the main factor responsible for the cell failure. SEM observation and EDX analysis confirm the presence of Mn, Co, and Ni elements on the MCMB anode surface when the cell is cycled with high charge voltage limits. [Copyright &y& Elsevier]

The activation characteristics and the effects of current densities on the formation of a separate LiCoO and graphite electrode were investigated and the behavior also was compared with that of the full LiCoO/graphite batteries using various electrochemical techniques. The results showed that the formation current densities obviously influenced the electrochemical impedance spectrum of Li/graphite, LiCoO/Li, and LiCoO/graphite cells. The electrolyte was reduced on the surface of graphite anode between 2.5 and 3.6 V to form a preliminary solid electrolyte interphase (SEI) film of anode during the formation of the LiCoO/graphite batteries. The electrolyte was oxidized from 3.95 V vs Li/Li on the surface of LiCoO to form a SEI film of cathode. A highly conducting SEI film could be formed gradually on the surface of graphite anode, whereas the SEI film of LiCoO cathode had high resistance. The LiCoO cathode could be activated completely at the first cycle, while the activation of the graphite anode needed several cycles. The columbic efficiency of the first cycle increased, but that of the second decreased with the increase in the formation current of LiCoO/graphite batteries. The formation current influenced the cycling performance of batteries, especially the high-temperature cycling performance. Therefore, the batteries should be activated with proper current densities to ensure an excellent formation of SEI film on the anode surface. [ABSTRACT FROM AUTHOR]

Abstract: Ceramic-coated separators are prepared by coating the sides of a porous polyethylene membrane with nano-sized Al2O3 powder and hydrophilic poly(lithium 4-styrenesulfonate) binder. These separators exhibit an improved thermal stability at high temperatures without significant thermal shrinkage. Due to the high hydrophilicity of the polymer binder and large surface area of the small ceramic particles, the separators show good wettability in non-aqueous liquid electrolytes. By using the ceramic-coated separators, lithium-ion cells composed of a carbon anode and a LiCoO2 cathode are assembled and their cycling performance is evaluated. The cells are proven to have better capacity retention than for cells prepared with polyethylene membrane. It is expected that the ceramic-coated separator in this study can be potential candidate as a separator for rechargeable lithium-ion batteries that require thermal safety and good capacity retention. [Copyright &y& Elsevier]

Abstract: Functionalized disiloxane compounds were synthesized by attaching oligo(ethylene glycol) chains, –(CH2CH2O)– n , n =2–7, via hydrosilation, dehydrocoupling, and nucleophilic substitution reactions and were examined as non-aqueous electrolyte solvents in lithium-ion cells. The compounds were fully characterized by 1H, 13C, and 29Si nuclear magnetic resonance (NMR) spectroscopy. Upon doping with lithium bis(oxalato)borate (LiBOB) or LiPF6, the disiloxane electrolytes showed conductivities up to 6.2×10−4 Scm−1 at room temperature. The thermal behavior of the electrolytes was studied by differential scanning calorimetry, which revealed very low glass transition temperatures before and after LiBOB doping and much higher thermal stability compared to organic carbonate electrolytes. Cyclic voltammetry measurements showed that disiloxane-based electrolytes with 0.8M LiBOB salt concentration are stable to 4.7V. The LiBOB/disiloxane combinations were found to be good electrolytes for lithium-ion cells; unlike LiPF6, LiBOB can provide a good passivation film on the graphite anode. The LiPF6/disiloxane electrolyte was enabled in lithium-ion cells by adding 1wt% vinyl ethylene carbonate (VEC). Full cell performance tests with LiNi0.80Co0.15Al0.05O2 as the cathode and mesocarbon microbead (MCMB) graphite as the anode show stable cyclability. The results demonstrate that disiloxane-based electrolytes have considerable potential as electrolytes for use in lithium-ion batteries. [Copyright &y& Elsevier]

Abstract: The formation of passivating surface films on the electrodes of a lithium-ion polymer battery was investigated at various cycling state using ac impedance spectroscopy and scanning electron microscopy (SEM). A sealed commercial cell (Sony Co.) with a nominal capacity of 840mAh was used for the experiment. An equivalent circuit used to model the impedance spectra show that, with continuous cycling there is a relatively large increase in the interfacial impedance and charge transfer resistances after a few hundred charge–discharge cycles. It was observed that the cell capacity decrease with increase cell impedance. SEM analysis on the electrodes shows that during continuous charge–discharge cycling, the deposition of sub-micro-size particles and dissolution of surface films on the graphite surface. This observation is consistent with increase in cell impedance as a function of charge/discharge cycling. [Copyright &y& Elsevier]

Abstract: A series of multi-functional zwitterionic compounds having both ester and sulfonate groups were synthesized and their electrochemical properties were investigated. The effect of added zwitterionic compounds on the cycling performance of the cell containing 1M LiPF6 in EC, DMC, and EMC (1/1/1 by vol.) was also examined. The cell capacity was not varied much at 1/5C up to 50 cycles with the addition of either 2.25wt% N-methylpyrrolidinium-N-(propyl sulfonate) (MePyS) or N-methylpiperidinium-N-(propyl sulfonate) (MePipS) as an additive, but dropped significantly at higher C rate of 1C. Such a sharp decrease of the performance at higher C rate was not observed when MePyS or MePipS was replaced by N-(2-acetoxyethyl) pyrrolidinium-N-(propyl sulfonate) (EsPyS) or N-(2-acetoxyethyl) piperidinium-N-(propyl sulfonate) (EsPipS), implying the positive role of the ester functional group. FT-IR study clearly demonstrates that ester-containing zwitterionic compounds are able to interact with Li+ ions through both sulfonate and ester functional groups. [Copyright &y& Elsevier]

The cycling performance of a silicon/carbon composite anode has been significantly enhanced by using acrylic adhesive and modified acrylic adhesive as binder to fabricate the electrodes for lithium ion batteries. The capacity retentions of Si/C composite electrodes bound by acrylic adhesive and modified acrylic adhesive are 79% and 90% after 50 cycles, respectively. These two binders are electrochemically stable in the organic electrolyte in the working window. They also show larger adhesion strength between the coating and the Cu current collector as well as smaller solvent absorption in the electrolyte solvent than polyvinylidene fluoride (PVDF). Furthermore, sodium carboxyl methyl cellulose (CMC) plays an important role on improving the properties of acrylic adhesive, which increases the adhesive strength of acrylic adhesive and improves the activation of the electrodes. [ABSTRACT FROM AUTHOR]

Abstract: A gel polymer electrolyte is prepared by soaking a polymer-coated separator in electrolyte solution that contains an inorganic additive. The porous polymer coated on the separator is gelled by soaking in an electrolyte solution to encapsulate a larger amount of electrolyte solution. By using the gel polymer electrolyte, lithium-metal–polymer cells composed of a lithium anode and V2O5 cathode are assembled and their cycling performances are evaluated. The effect of an inorganic additive (AlI3) on the cycling performance of Li/V2O5 polymer cells is investigated. The addition of AlI3 to the gel polymer electrolyte reduces the interfacial resistance and thus the cells exhibit a less capacity fading and better high rate performance. [Copyright &y& Elsevier]

The gel-forming polymer of different thicknesses was coated on both sides of polyethylene separator. The porous polymer coated on the separator was gelled by soaking in an electrolyte solution and encapsulated a larger amount of electrolyte solution. Adhesive gel formed on both sides of PE separator provided an efficient transport of lithium ion through the solid electrolyte interphase, and the electrolyte solution absorbed in the separator gave an acceptable ionic conductivity. By using the separators with adhesive gel layer, lithium metal polymer cells composed of a lithium anode and LiCoO2 cathode were assembled and their cycling performances were evaluated. The effect of thickness of gel polymer layer on cycling performances of the rechargeable lithium-metal polymer cells was investigated. [Copyright &y& Elsevier]

Abstract: A triethanolamine/sucrose (TEA/sucrose) assisted complexing method has been employed to synthesize LiNi0.5Co0.5O2 system which is considered to be a potential candidate as cathode material for lithium-ion batteries. The TEA/sucrose ratio has been varied and the changes in the structural and electrochemical properties of the systems have been studied and correlated. The prepared materials were characterized using XRD, SEM and electrochemical charge–discharge cycles. The particle sizes of the prepared materials were in the submicron range of ∼300–350 nm. LiNi0.5Co0.5O2 synthesized with a TEA/sucrose ratio 1:8 exhibited improved electrochemical performance which was well complemented by the structural studies. The 1st and the 10th discharge capacities were 152 and 144 mA h/g, respectively. [Copyright &y& Elsevier]

Gel polymer electrolytes (GPEs) are prepared with methyl methacrylate (MMA)–styrene (ST) copolymers and LiPF6 or LiBF4 in ethylene carbonate/dimethyl carbonate. Depending on the molar composition of the copolymer, these gel polymer electrolytes exhibit a different range of mechanical and electrical properties. On the aspect of ionic conductivity and mechanical property, the copolymer comprising about 33 mol% MMA is found to be most desirable. Lithium-ion polymer cells employing GPE containing different electrolyte solution are assembled and their cycling performances are evaluated. [Copyright &y& Elsevier]

With a higher theoretical specific capacity (1675 mAh g−1) and energy density (2600 Wh kg−1), the lithium-sulfur (Li-S) battery is considered as a promising candidate for a next-generation energy storage device. However, the shuttle effect of polysulfides as well as the large interfacial impedance between brittle solid electrolyte and electrodes lead to the capacity of the Li-S battery decaying rapidly, which limits the practical commercial applications of the Li-S battery. Herein, we reported a facile in situ ultraviolet (UV) curing method to prepare a flexible quasi-solid-state composite electrolyte (QSSCE) of poly(propylene glycol)-co-pentaerythritol triacrylate/Li1.5Al0.5Ge1.5(PO4)3 (PPG-co-PETA/LAGP). By combining the high Li-ion conductivity and mechanical strength of inorganic NASICON-structure LAGP and good flexibility of the crosslinked PPG-co-PETA with nanopore structure, the flexible QSSCE with 66.85 wt% LAGP exhibited high Li-ion conductivity of 5.95 × 10−3 S cm−1 at 25 °C, Li-ion transference number of 0.83 and wide electrochemical window of ~5.0 V (vs. Li/Li+). In addition, the application of QSSCE in the Li-S battery could suppress the shuttle effect of polysulfides effectively, thus the Li-S battery possessed the excellent electrochemical cyclic performance, showing the first-cycle discharge-specific capacity of 1508.1 mAh g−1, the capacity retention of 73.6% after 200 cycles with 0.25 C at 25 °C and good rate performance. [ABSTRACT FROM AUTHOR]

The thermal instability of conventional polyolefin separators and the high flammability of organic electrolytes are the primary safety-related concerns of high-energy-density lithium-ion batteries. To address these issues, reactive Al 2 O 3 nanostructured materials are coated onto a polyethylene (PE) separator to promote the formation of gel electrolyte and enhance the thermal stability of the separator. The Al 2 O 3 nanostructured materials are surface-treated by 3-methacryloxypropyl trimethoxysilane to induce radical polymerization with tetra(ethylene glycol) diacrylate (TEGDA) in liquid electrolyte. The three-dimensional network formed by cross-linking reactive alumina nanostructured materials and TEGDA reduces the electrolyte leakage from the cell and enhances the interfacial adhesion between separator and electrodes. Thermal shrinkage of the reactive alumina-coated separator is also significantly reduced at 140 °C, providing enhanced thermal stability. In addition to improved thermal safety, lithium-ion cells employing a reactive alumina-coated PE separator exhibit stable cycling at both ambient and high temperatures. • Reactive alumina-coated separator is prepared to promote gel electrolyte formation. • Thermal stability of alumina-coated separator is significantly enhanced at 140 oC. • The cell with reactive separator exhibits good cycling stability and enhanced safety. • The reactive Al 2 O 3 coated-separator is promising for enhancing the battery safety. [ABSTRACT FROM AUTHOR]