Lithium Bis Trifluoromethanesulphonyl Imide Research Articles

Interface engineering enabling non-corrosive sulfonimide salt for 4.4 V class lithium batteries

Lithium bis(trifluoromethanesulphonyl)imide (LiTFSI) with outstanding electrochemical and thermal stability has promising applications in electrolytes for lithium batteries. However, a low concentration of the sulfonimide salt electrolyte can corrode a commonly used aluminum (Al) current collector, posing a perennial conundrum that hinders its wide application. In this work, we find that pure H2O as an additive in the 1 M LiTFSI electrolyte effectively protects the Al current collector from corrosion by TFSI−. The interface engineering by specific adsorption of H2O plays a pivotal role in regulating the structure of the electrical double layer on the Al foil surface, blocking the interaction of TFSI− with Al. Meanwhile, hydrogen bonds are verified between H2O and TFSI−, weakening the attack of TFSI− on the Al collector and improving the Li+ conductivity. The mechanism has been confirmed by theoretical calculations and a variety of characterizations. Benefiting from the addition of H2O, the lithium batteries exhibit excellent cycling performance at a high cut-off voltage of 4.4 V even at −20 °C and a 3 Ah pouch full cell shows long cycling performance. The results demonstrate the high compatibility of the H2O-added electrolyte with high voltage cathode, lithium metal and graphite anodes. This work introduces a strategy for the utilization of sulfonimide salt at high voltage and wide temperature even at a low concentration.

Dual-salt strategy tuning the solvation structure to achieve high cycling stability for FeS2 cathodes

Pyrite FeS2, as a promising conversion-type cathode material, faces rapid capacity degradation due to challenges such as polysulfide shuttle and massive volume changes. Herein, a localized high-concentration electrolyte (LHCE) based on dual-salt lithium bis(fluorosulfonyl)imide (LiFSI) and lithium bis(trifluoromethanesulphonyl)imide (LiTFSI) is designed to address the challenges. By the dual-salt strategy, we tailor a more desirable solvation structure than that in the single-salt system. Specifically, the solvation structure involving FSI− and TFSI− enables milder electrolyte decomposition, which reduces initial capacity loss. Meanwhile, it facilitates the formation of a stable and flexible cathode/electrolyte interphase (CEI), effectively mitigating side effects and accommodating volume changes. Consequently, the micro-sized FeS2 realizes a capacity of 641 mAh g−1 after 600 cycles with a retention rate of 90%, significantly improving the cycling stability of the FeS2 cathode. This work underscores the pivotal role of solvation structure in modulating electrochemical performances and provides a simple and effective electrolyte design concept for conversion-type cathodes.

Exploring the Efficiency of Lithium Stripping/Plating in Solid Polymer Anode-Free Lithium Cells

Traditional Li-ion batteries (LIBs) are widely used in various electronic devices due to their advantages in energy storage applications. However, finding ways to push the energy densities even higher would be highly desirable for the further rapid development of electric vehicles and electromobility. Li metal batteries and anode-free batteries (AFBs) – where the Li metal is plated in situ from Li+ ions taken from the cathode – have received extensive attention and research due to their very high specific capacity.[1] However, Li ions are unevenly deposited on the surface of anodes to form Li dendrite during the charging and discharging process, which severely deteriorates their electrochemical performance and battery safety.[2] To solve this problem, many researchers choose solid polymer electrolytes (SPEs) instead of liquid electrolytes in the batteries, because of the stability of SPEs towards Li metal.Long-term cycling of AFBs requires high-efficiency Li metal stripping and plating, which in a solid polymer cell is highly dependent on the polymer electrolyte system used, so finding appropriate host materials and salts to for the SPEs is very necessary. Poly(ethylene oxide) (PEO)-based SPEs are one of the most popular host materials for SPEs, due to their excellent chemical stability. Poly(ε-caprolactone) (PCL)-based SPEs have higher ionic conductivity and can be cycled at room temperature.[3] Poly(trimethylene carbonate) (PTMC)-based SPEs have high lithium transference number and better mechanical properties.[4] Lithium bis(trifluoromethanesulphonyl)imide (LiTFSI) is one of the most popular salts used for SPEs. Recently, lithium difluoro(oxalate)borate (LiDFOB) and lithium bis(oxalato)borate (LiBOB) have been considered a promising alternative as electrolyte because they can passivate electrode surfaces and protect electrode materials.[5] Combinations of these materials are all potentially relvant for application in AFBs.In this work, three different polymer host materials, PEO, PTMC, and PCL, were explored as polymer electrolytes together with LiTFSI salt for their performance in anode-less cell setups, testing the plating/striping coulombic efficiency (CE) in Cu || Li cells. The results reveal clear issues for the CE of cycling in the PEO:LiTFSI system, while low-concentration PTMC:LiTFSI instead shows much more promising results. Changing the LiTFSI salt for LiBOB or LiDFOB also improves the CE of the cells.[1] Beyene, T. T., Jote, B. A., Wondimkun, Z. T., Olbassa, B. W., Huang, C. J., Thirumalraj, B., Wang C. H., Su W. N., Dai H., Hwang B. J., Effects of concentrated salt and resting protocol on solid electrolyte interface formation for improved cycle stability of anode-free lithium metal batteries, ACS applied materials & interfaces, 2019, 11(35), 31962.[2] Huang W. Z., Zhao C. Z., Wu P., Yuan H., Feng W. E., Liu Z. Y., Lu Y., Sun S., Fu Z. H., Hu J. K., Yang S. J., Anode‐Free Solid‐State Lithium Batteries: A Review, Advanced Energy Materials, 2022, 12(26), 2201044.[3] Chiu, C. Y., Chen, H. W., Kuo, S. W., Huang, C. F., Chang, F. C., Investigating the effect of miscibility on the ionic conductivity of LiClO4/PEO/PCL ternary blends. Macromolecules, 2004, 37(22), 8424.[4] Li Z., Mogensen R., Mindemark J., Bowden T., Brandell D., Tominaga Y., Ion‐conductive and thermal properties of a synergistic poly (ethylene carbonate)/poly (trimethylene carbonate) blend electrolyte. Macromolecular rapid communications, 2018, 39(14):1800146.[5] Shkrob, I. A., Zhu, Y., Marin, T. W., Abraham, D. P., Mechanistic Insight into the Protective Action of Bis (oxalato) borate and Difluoro (oxalate) borate Anions in Li-Ion Batteries, The Journal of Physical Chemistry C, 2013, 117(45), 23750.

Efficient anion solvation modulation in carbonate electrolytes enables high-voltage lithium metal batteries

Developing electrolytes qualified for high-voltage (>4 V vs Li/Li+) conditions is of great significance for high-energy density Li-metal batteries (LMBs). Carbonate-based electrolytes possess high oxidation stability, whereas the uneven Li deposition, low Coulombic efficiency (CE) and poor anodic stability of such electrolytes severely impede the practical application in high-voltage LMBs. Herein, a 1.8 M lithium bis(trifluoromethanesulphonyl)imide (LiTFSI)-carbonate electrolyte with high compatibility with both Li anode and high-voltage cathode is designed. LiNO3 is introduced into the electrolyte as an additive with the assistance of CuF2 cosolvent, which efficiently enables robust and conductive interfaces at both anode and cathode sides. As a consequence, an average CE of 98.0% is achieved for Li||Cu half-cell at 1 mA cm−2. Li||LiNi0.8Co0.1Mn0.1O2 full cell fabricated with cathode areal capacity of 2.4 mAh cm−2 and 5× excess Li achieves a high capacity retention of 80.7% after 200 cycles with cut-off voltage of 4.3 V. This work provides a facile and effective approach to improve the application of carbonate-based electrolytes in high-voltage LMBs.

Desilicated zeolite ZSM-5 based composite polymer electrolytes for solid-state lithium metal batteries

The desilicated zeolite ZSM-5 (des-ZSM-5) based composite polymer electrolytes (CPEs) PZEw was fabricated via phase inversion processes and in-situ polymerization with polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) and liquid electrolyte 1 M lithium bis(trifluoromethanesulphonyl)imide (LiTFSI) in vinylene carbonate (VC) (VC@LiTFSI). Assisted by des-ZSM-5, PZEw possess excellent thermal stability, mechanical properties, high ionic conductivity (2.75 × 10−4 S cm−1, 25 °C), and enlarged electrochemical windows (4.94 v, vs. Li+/Li). Meanwhile lithium metal batteries (LMBs) LiFePO4 (LFP)/PZEw/Li showed superior rate performance and long-time cycling stability.

Poly(vinylidene fluoride)-based dual-salt composite polymer electrolytes for superior room-temperature solid-state lithium batteries

Polymer electrolytes are one of the most promising candidates for advancing the development of solid-state lithium metal batteries (SLMBs) due to their easy preparation process, high flexibility, and lightweight. However, the low ionic conductivity at room temperature limits their practical applications. In this study, we propose a strategy of dual-salt modification of polyvinylidene fluoride (PVDF)-based polymer electrolytes to enhance lithium ion transport channels, specifically through the introduction of Lithium bis(trifluoromethanesulphonyl)imide (LiTFSI), lithium bis(oxalate)borate (LiBOB), and Li6.4La3Zr1.4Ta0.6O12 (LLZTO) into polyvinylidene fluoride-polyvinyl acetate (PVDF-PVAC) polymer chain to form a dual-salt composite polymer electrolyte (DS-CPE), which effectively control the dehydrofluorination of the PVDF skeleton and eliminate the PVDF gel discoloration phenomenon. The newly developed DS-CPE shows high ionic conductivity at room temperature (4.96 × 10−4 S cm−1), sufficient Li+ transference number (tLi+ = 0.57), excellent oxidation resistance (5.4 V vs. Li/Li+), and favorable interfacial compatibility. Moreover, Li|DS-CPE|Li symmetric cell stably cycles 1300 h at 0.1 mA cm−1, and the Li|DS-CPE|LFP cell delivers excellent rate performance, maintaining a capacity retention of 91.4 % over 450 cycles.

One dimensional CeO2 nanorods/poly(ethylene oxide) solid composite electrolyte for all-solid-state lithium-ion batteries

The research of poly(ethylene oxide) (PEO)-based solid composite electrolyte with high ionic conductivity and excellent interfacial stability is the key to the development of all-solid-state lithium-ion batteries (ASSLIBs). Herein, uniform nanorod structured CeO2 fillers were controllably synthesized by electrospinning, which were subsequently filled into PEO polymer to prepare CeO2/PEO solid composite electrolyte. The addition of CeO2 nanorods can reduce both the glass transition temperature and the melting point of PEO polymer, and also interact with PEO and lithium bis(trifluoromethanesulphonyl)imide (LITFSI) by Lewis acid–base reaction. Therefore, the solid composite electrolyte exhibits a high ionic conductivity of 4.52 × 10−4 S/cm, a wide electrochemical stability window of about 4.8 V, and a good interfacial stability with Li at 55 °C. Moreover, the LiFePO4/Li ASSLIB divulges the discharging specific capacity of 165, 162, 156 and 146 mA⋅h/g at 0.2, 0.5, 1 and 2 C, respectively, and achieves the capacity retention of 90.3% after 150 cycles at 0.5 C. Consequently, one dimensional CeO2 nanorods can be considered as an alternative filler for polymeric solid electrolyte.

Mussel‐Inspired, Underwater Self‐Healing Ionoelastomers Based on α‐Lipoic Acid for Iontronics

Weak adhesion and lack of underwater self-healability hinder advancing soft iontronics particularly in wet environments like sweaty skin and biological fluids. Mussel-inspired, liquid-free ionoelastomers are reported based on seminal thermal ring-opening polymerization of a biomass molecule of α-lipoic acid (LA), followed by sequentially incorporating dopamine methacrylamide as a chain extender, N,N'-bis(acryloyl) cystamine, and lithium bis(trifluoromethanesulphonyl) imide (LiTFSI). The ionoelastomers exhibit universal adhesion to 12 substrates in both dry and wet states, superfast self-healing underwater, sensing capability for monitoring human motion, and flame retardancy. The underwater self-repairabilitiy prolongs over three months without deterioration, and sustains even when mechanical properties greatly increase. The unprecedented underwater self-mendability benefits synergistically from the maximized availability of dynamic disulfide bonds and diverse reversible noncovalent interactions endowed by carboxylic groups, catechols, and LiTFSI, along with the prevented depolymerization by LiTFSI and tunability in mechanical strength. The ionic conductivity reaches 1.4 × 10-6 -2.7 × 10-5 S m-1 because of partial dissociation of LiTFSI. The design rationale offers a new route for creating a wide range of LA- and sulfur-derived supramolecular (bio)polymers with superior adhesion, healability, and other functionalities, and thus has technological implications for coatings, adhesives, binders and sealants, biomedical engineering and drug delivery, wearable and flexible electronics, and human-machine interfaces.

Highly conductive Poly(ε-caprolactone) and chitosan based polymer electrolyte for lithium metal battery

Poly (ε-caprolactone) (PCL) is an attractive polymer electrolyte material due to its ultralow glass transition temperature, high dielectric constant as well as excellent electrochemical stability, but its practical application has been greatly hindered due to the low ionic conductivity induced by the semi-crystalline structure. Herein, we elaborately modify PCL with chitosan (CS) to obtain an amorphous PCL-CS composite membrane, and develop a fast Li+ conducting quasi-solid polymer electrolyte (QPE) with lithium bis(trifluoro methane sulphonyl)imide (LiTFSI) and merely 10 wt% plasticizer. The optimized QPE with 50 wt% LiTFSI exhibits an ionic conductivity of 7.7 × 10−4 S cm−1, which is the highest among PCL-based polymer electrolyte. Fourier Transform Infrared spectroscopy and Raman spectra reveal that Li+ conducting via the solvation of partial plasticizer as well as contacted ionic clusters. In addition, its excellent stability and compatibility are validated by the integrated symmetric Li//Li cell that exhibits an ultra-long cycling for over 1850 h with no Li dendrite formation.

Bi-nanofillers integrated into PEO-based electrolyte for high-performance solid-state Li metal batteries

Solid-state lithium metal batteries (SSLMBs) with high safety and high energy densities draw widespread attention in recent years. Nevertheless, the intrinsic defects of the solid-state electrolyte (SSE) such as the poor compatibility with electrodes and low ionic conductivity hamper the application of SSMLBs. Herein, we introduce rigid two-dimensional hexagonal boron nitride (BN) nanosheets and flexible One-dimensional aramid nanofibers (ANFs) as bi-nanofillers into the polyethylene oxide (PEO)-based SSEs to fabricate a composite solid-state electrolyte (CSE) ANF-PEO-BN with network structure boosting the comprehensive performance of SSMLBs. ANF and BN with special properties and structures are prone to be dispersed homogeneously in the PEO matrix to build the ANF-PEO-BN electrolyte, whose rigid and flexible network structure ensures the formation of Li dendrites inhibited. Furthermore, the dissociation of lithium bis(trifluoromethanesulphonyl)imide (LiTFSI) is promoted and more ion transport channels are provided due to the strong affinity between Lewis acid centers of ANF/BN and Li+/TFSI−. As a result, the LiFePO4/Li batteries deliver high-capacity retention of 86% after 500 cycles and Li/Li cells stably cycle beyond 3300 h with small overpotential of 10 mV at 0.1 mA cm−2/0.2 mAh cm−2.

High-performance garnet solid-state battery enabled by improved interfaces

Garnet solid electrolyte is expected to become the electrolyte of choice for next-generation solid-state batteries due to its high ionic conductivity and wide electrochemical window. However, the poor interfacial contact between electrolyte and electrodes limits the battery performance. In this work, the interface between the garnet and cathode is improved by utilizing a deep eutectic electrolyte (DEE) composed of 2,2′-dipyridyl disulfide and lithium bis(trifluoromethanesulphonyl)imide (LiTFSI) with high ionic conductivity and viscosity. It can favorably bind carbon and LiFePO4 particles, forming an intimate contact between the garnet and active material. In addition, by utilizing a succinonitrile gel electrolyte between the lithium metal anode and garnet, the assembled solid-state cell shows improved interfacial stability and promising cycling performance, i.e., a high initial discharge capacity of 134.2 mAh g−1 and capacity retention of 97.8% after 100 cycles at 0.2 C.

MXene//MnO2 Asymmetric Supercapacitors with High Voltages and High Energy Densities

AbstractAqueous asymmetric supercapacitors (AASCs) can have high voltages and high energy densities. However, the rational design of AASCs with proper negative and positive electrodes remains a challenge. Herein, we report on an AASC using Mo1.33CTz MXene films as the negative electrode, and tetramethylammonium cation intercalated birnessite (TMA+‐MnO2) films as the positive electrode in a 21 mol kg−1 lithium bis(trifluoromethanesulphonyl)imide (LiTFSI) electrolyte. Benefiting from a high, stable voltage of 2.5 V, an energy density of 86.5 Wh L−1 at 2 mV s−1 and a power density of 10.3 kW L−1 at 1 V s−1 were achieved. The cells also exhibit excellent cycling stability (>98 % after 1,0000 cycles at 100 mV s−1) and a 51.1 % voltage retention after 10 h. This good performance is attributed to the high stable potential window and high volumetric capacitances of both Mo1.33CTz and TMA+‐MnO2 electrodes in highly concentrated electrolytes. This work provides a roadmap for developing high performance AASCs with high voltages and high energy/power densities, with relatively slow self‐discharge rates.

Synthesis and characterization of electrolyte substrate materials based on hyperbranched polyurethane elastomers for anodic bonding

AbstractA series of hyperbranched polyurethane elastomers (PEO‐HBPUEs) as polymer electrolyte substrate materials was developed for anodic bonding with aluminum (Al) foil in micro‐electro‐mechanical system (MEMS) devices. The PEO‐HBPUEs were prepared by pre‐polymerization method with toluene‐2,4‐diisocyanate(TDI), polypropylene glycol (PPG), 1,4‐butanediol(BDO), trimethylolpropane(TMP), lithium bis(trifluoromethanesulphonyl)imide (LiTFSI), and polyethylene oxide (PEO)‐based electrolyte in varying proportions via solution casting technique at room temperature. All prepared PEO‐HBPUEs exhibited low glass transition temperatures, good thermal stabilities, and suitable mechanical properties. The XRD results showed that PEO‐HBPUEs are amorphous, and LiTFSI was well dissolved in the polymer matrix. The component of PEO‐based electrolyte in PEO‐HBPUEs contributed to increase the ionic conductivity, of which the highest value reached 1.23 × 10−3 S/cm at 75°C for PEO‐HBPUE4. The anodic bonding of PEO‐HBPUE substrate with Al foil was conducted by the coupling action of electric field, temperature field, and pressure field. A clear intermediate bonding layer between the substrate and Al foil was observed and the elements diffusion around bonding layer can be detected by SEM, indicating PEO‐HBPUEs and Al foil have been jointed together successfully. The highest tensile strength of the bonding interface of PEO‐HBPUE4/Al reached 1.88 MPa. All results demonstrated that the prepared PEO‐HBPUEs materials would be promising substrates for flexible MEMS device that can be applied to flexible packaging by anodic bonding technology.

An evaluation of solid-state electrolyte based on pectin and lithium bis (trifluoromethanesulphonyl)imide for lithium-ion batteries

In this era, surviving Li-ion batteries is power-driven by various solid electrolytes, focusing majorly on lithium polymer electrolytes. A huge challenge in finding an electrolyte with the highest and stable ionic conductivity is on the process. In this connection, the present study aims in preparing a solid electrolyte using lithium bis(trifluoromethanesulphonyl)imide (LiTFSI) doped in host Pectin (biopolymer) by solution casting technique. The prepared solid polymer electrolyte was characterized using XRD, FT-IR Spectrophotometer, TG/DTA, and 3D Optical Laser Profilometry techniques. The ionic conductivity was determined using an AC Impedance spectroscopy. The results obtained revealed the interaction between the polymer and the LiTFSI. The electrolyte was found to be amorphous and the optical profilometry showed the average roughness which was stable at elevated temperatures. The conductivity of the electrolyte was found to be at a higher order. Thus, the prepared solid polymer electrolyte system may be suitable for greater energy outputs with improved safety.

Preparation and characterization of Guar gum-based solid biopolymer electrolyte doped with lithium bis(trifluoromethanesulphonyl)imide (LiTFSI) plasticized with glycerol

The Guar gum (GG)–lithium bis(trifluoromethanesulphonyl)imide (LiTFSI)-glycerol-based solid biopolymer electrolyte has been investigated. The polymer electrolytes has been prepared via solution casting technique and characterized by Fourier transform infrared (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), 3D-laser profilometry and AC impedance studies. The amorphous nature and complexation has been revealed by XRD and FTIR. TGA reveals that the polymer electrolyte is stable up to 260°C. The average roughness was measured using 3D-laser profilometry. The ionic conductivity of the electrolyte was studied using impedance analysis. The best optimum ionic conductivity of 2.041 × 10−3 S cm−1 has been achieved for the film containing 60 wt% GG–40 wt% LiTFSI.

A stable protective layer toward high-performance lithium metal battery

Metal lithium anodes are quite promising for next-generation batteries due to their high energy density and low voltage, which has attracted numerous attention of the researchers. However, the main challenge for lithium anodes still lies on their serious dendrite problems, leading to the poor cycling stabilities. Here, we introduced poly(vinylidene-co-hexafluoropropylene) (PVDF-HFP) composite film combined with nano alumina (nano-Al2O3), lithium fluoride (LiF) and lithiumbis(trifluoromethanesulphonyl)imide (LiTFSI), as a stable protective layer (SPL), to coat on the surface of cooper current collector, which was beneficial to improve the cycling stabilities of the fabricated lithium–copper (Li–Cu) half-cell. The copper foil electrode modified with the protective layer exhibited a much enhanced cycling performance compared with the one without modification, which did not show obvious capacity decay after 250 cycles at the current density of 0.5 mA/cm2 for 2 h. From SEM and XPS characterizations, it had to be found that the preset protective composite layer kept a stable structure during the charge and discharge process, which guaranteed the achieved stable cycling performance. In addition, a full battery system based on modified copper foil anode and LiFePO4 cathode also constructed and presented a good cycling performance.

Graphene-Armored Aluminum Foil with Enhanced Anticorrosion Performance as Current Collectors for Lithium-Ion Battery.

Aluminum (Al) foil, as the most accepted cathode current collector for lithium-ion batteries (LIBs), is susceptible to local anodic corrosions during long-term operations. Such corrosions could lead to the deterioration or even premature failure of the batteries and are generally believed to be a bottleneck for next-generation 5 V LIBs. Here, it is demonstrated that Al foil armored by conformal graphene coating exhibits significantly reinforced anodic corrosion resistance in both LiPF6 and lithium bis(trifluoromethanesulphonyl) imide (LiTFSI) based electrolytes. Moreover, LiMn2 O4 cells using graphene-armored Al foil as current collectors (LMO/GA) demonstrate enhanced electrochemical performance in comparison with those using pristine Al foil (LMO/PA). The long-term discharge capacity retention of LMO/GA cell after ≈950 h straight operations at low rate (0.5 C) reaches up to 91%, remarkably superior to LMO/PA cell (75%). The self-discharge propensity of LMO/GA is clearly relieved and the rate/power performance is also improved with graphene mediations. This work not only contributes to the long-term stable operations of LIBs but also might catalyze the deployment of 5 V LIBs in the future.

Safety-Reinforced and High-Voltage Poly(propylene carbonate)-Based All-Solid-State Polymer Electrolyte for Ambient-Temperature Solid Polymer Lithium Batteries

1. Introduction There were huge potential safety hazards when commercialized lithium ion battery employing organic carbonate solvent and polyolefin-based separators. These potential risks (combustion and explosion) would retard the commercialization of electric vehicles or hybrid electric vehicles. Thus, the safety issue of lithium ion battery merits further study. Solid polymer electrolyte is attracting strong interest and regarded as a perfect way to handle the potential safety risk of lithium batteries. 2. Experimental poly(propylene carbonate) (PPC) based solid polymer electrolytes were fabricated by a facile solution casting method. PPC (10 g) and lithium bis (trifluoromethanesulphonyl) imide (LiTFSI) (3 g) were added into anhydrous acetonitrile (100 mL) in sequence under intense stirring to form a homogeneous solution. Subsequently, flame retardant cellulose nonwoven membrane was prepared according to the method of our previous literature. Followingly, homogeneous solution poured into cellulose nonwovens followed by the evaporation of the solvent in a vacuum oven at 100 oC for 24 hrs. The thickness of the resultant cellulose-supported PPC solid polymer electrolyte (CPPC-SPE) was 75±5 μm. Pristine PPC solid polymer electrolyte (PPC-SPE) and pristine polyethylene oxide (PEO) solid polymer electrolyte (PEO-SPE) were fabricated via similar method without cellulose nonwoven supporting matrix. 3. Results and Discussion In order to demonstrate the feasibility of the novel CPPC-SPE, all-solid-state polymer LiFePO4/Li battery was assembled and typical charge-discharge curves at various rates and long-term cycling stability were also examined (Fig. 1). It is obvious that rate capability and cycle performance of CPPC-SPE was much better than those of PEO-SPE at room temperature. This better rate performance is an indicator of a low resistance, which can be contributed to better ionic transport capability, demonstrating that CPPC-SPE has great potential in ambient temperature all-solid-state lithium batteries. It was noted that the cell with CPPC-SPE displayed superior cycle durability after 1000 cycles at 20 oC, 95 % of the initial capacity. This outstanding cycle performance would be attributed to better electrochemically interfacial stability. It can be seen from Figure 4c that the value of charge-transfer resistance after first cycle was 73 Ω. After the 1000 cycles, the value became 83 Ω, indicative of a minor augment of charge-transfer resistance. More importantly, solid state soft-package lithium batteries using CPPC-SPE can present excellent safety characteristic even in extremely harsh condition. A corollary of this is that, this class of CPPC-SPE is very promising to develop next-generation all-solid-state lithium batteries that require high energy density, superior safety and excellent reliability. Most significantly, the main innovative of our work will highlight a reference for subsequent scientific research of room temperature solid polymer electrolyte and also boost the development of high performance all solid state polymer lithium batteries. References 1) G. L. Cui, et. al Advanced Energy Materials DOI: 10.1002/aenm.201501082. 2) G. L. Cui, et. al Sci entific Rep orts 2014, 4, 6272. Figure 1

Highly conductive solvent-free polymer electrolyte membrane for lithium-ion batteries: Effect of prepolymer molecular weight

The present article demonstrates the effects of molecular weight of network precursor on properties of solid-state polymer electrolyte membrane (PEM) comprised of poly (ethylene glycol) diacrylate (PEGDA) prepolymer, succinonitrile (SCN) plasticizer, and lithium bis(trifluoromethane sulphonyl) imide (LiTFSI) salt using two different PEGDA molecular weights. To provide guidance for crosslinking reaction, ternary phase diagrams of the PEM precursor mixtures were established. Upon photopolymerization within the wide isotropic region, completely amorphous membranes were obtained in several compositions. The PEM having a higher PEGDA molecular weight (i.e., 6000g/mol) revealed both improved impact strength with an elongation at break of ~80 % and higher ambient temperature ionic conductivity (~1.4×10−3Scm−1) relative to the low molecular weight counterpart (i.e., 700g/mol). Both PEMs exhibited excellent electrochemical (4.8V/Li/Li+) and thermal (140°C) stabilities. Specific discharge capacities of the PEM containing half-cells using LiFePO4 or Li4Ti5O12 electrodes against lithium electrode reached the level of ~140mAhg−1 at 0.2°C, indicating potential applications in all solid-state lithium-ion batteries.

Surfactant for Enhanced Rheological, Electrical and Electrochemical Performance of Suspensions for Semi-Solid Redox Flow Batteries and Supercapacitors

Redox-flow batteries (RFBs) store electrochemical energy in two fluids contained in external tanks, so called anolyte and catholyte which are pumped and flow through an electrochemical reactor in which electro-active species are oxidized and reduced. This feature provides to RFBs a unique ability in decoupling the energy and the power, therefore providing a significant design freedom for stationary applications. An interesting concept to deal with the energy density of RFBs, proposed by Chiang et al. [1], consists to use solid electro-active particles suspended in a Li+ containing electrolyte. The interest of such Semi-Solid Flow Cell (SSFC) system has recently been demonstrated with energy density ten times higher compared to classical RFBs [2,3]. Subsequently, Gogotsi et al. proposed an analogous to supercapacitors, the so called electrochemical flow capacitor (EFC) in which the energy is stored in the electric double layer of charged carbon particles [4]. A flowable carbon-electrolyte mixture is employed as the active material for capacitive energy storage, and is handled in a similar fashion to flow as for semi-solid batteries.Performance of SSFC (and EFC) system strongly depends on the flow ability of the anolyte and catholyte suspensions combined with their electronic conductivity which is governed by the extent of the carbon black percolation. In this regards, we have recently investigated the rheological and electrical behaviours of two carbon blacks [5], namely, Ketjen black EC-300 (KB) and C-NERGY Super C45, which differ by their primary particle size, and blends of Li4Ti5O12 (LTO) and KB, suspended in an organic electrolyte, a solution of 1M of Lithium bis(trifluoromethanesulphonyl)imide (LiTFSI) in propylene carbonate (PC). The electrochemical performance of the LTO/KB/PC-LiTFSI suspension was investigated vs. lithium metal electrode as function of the cycling rate in static mode (i.e. no flow) and using a home-made cell that allows studying the influence of the thickness of the suspension [6].Recently, we demonstrated the very beneficial influence of the addition of a nonionic surfactant in the composition of the LTO/KB/PC-LiTFSI anolyte suspension. All practical properties are improved with respect to semi-solid redox flow application. As a matter of fact, the viscosity is decreased, the electronic conductivity is increased and is less affected by the shear flow, and the electrochemical performance is increased. Moreover, a much better stability with time of the suspension is obtained, which means the preservation of its performance with time.