Search Results (12)

Composite solid electrolytes are gaining interest regarding their use in Li-metal solid-state batteries. Although high ceramic content improves the electrochemical stability of ceramic-rich composite separators (C-SCE), the polymeric matrix also plays a vital role. In the first generation of C-SCE separators with a PEO-based matrix, the addition of 90–95 wt% of Li_6.45Al_0.05La₃Zr_1.6Ta_0.4O₁₂ (LLZO) does not make C-SCE stable for cell cycling with high-voltage (HV) cathodes. For the next iteration, the objective was to find an HV-stable polymeric matrix for C-SCEs. Herein, we report results on optimizing C-SCE separators with different ceramics and polymers which can craft the system towards better stability with NMC622-based composite cathodes. Both LLZO and Li_1.3Al_0.3Ti_1.7(PO₄)₃ (LATP) were utilized as ceramic components in C-SCE separators. Poly(diallyldimethylammonium) bis(trifluoromethanesulfonyl)imide (PDDA-TFSI) and poly (vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) were used as polymers in the “polymer/LiTFSI/plasticizer”-based matrix. The initial phase of the selection criteria for the separator matrix involved assessing mechanical stability and ionic conductivity. Two optimized separator formulations were then tested for their electrochemical stability with both Li metal and HV composite cathodes. The results showed that Li/NMC622 cells with LP70_PVDF_HFP and LZ70_PDDA-TFSI separators exhibited more stable cycling performance compared to those with LZ90_PEO300k-based separators. Full article

The novel crosslinked composite polymer electrolyte (CPE) was developed and investigated using polytetrahydrofuran (PTHF) and polyethyleneglycol diacrylate (PEGDA), incorporating lithium aluminum titanium phosphate (LATP) particles and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) salt. Composite polymer electrolytes (CPEs) for solid-state lithium-ion batteries (LIBs) were synthesized by harnessing the synergistic effects of PTHF crosslinking and the addition of LATP ceramics, while systematically varying the film composition and LATP content. CPEs containing 15 wt% LATP (PPL15) demonstrated improved mechanical strength and electrochemical stability, achieving a high conductivity of 1.16 × 10⁻⁵ S·cm⁻¹ at 80 °C, outperforming conventional PEO-based polymer electrolytes. The CPE system effectively addresses safety concerns and mitigates the rapid degradation typically associated with polyether electrolytes. The incorporation of PEGDA not only enhances mechanical stability but also facilitates lithium salt dissociation and ion transport, leading to a uniform microstructure free from agglomerated particles. The temperature-dependent ionic conductivity measurements indicated optimal performance at lower LATP concentrations, highlighting the impact of ceramic particle agglomeration onion transport pathways. These findings contribute to advancing solid-state battery systems toward practical application. Full article

Composite solid electrolytes (CSEs), composed of sodium superionic conductor (NASICON)-type Li_1+xAl_xTi_2-x(PO₄)₃ (LATP), poly (vinylidene fluoride-hexafluoro propylene) (PVDF-HFP), and lithium bis (trifluoromethanesulfonyl)imide (LiTFSI) salt, are designed and fabricated for lithium-metal batteries. The effects of the key design parameters (i.e., LiTFSI/LATP ratio, CSE thickness, and carbon content) on the specific capacity, coulombic efficiency, and cyclic stability were systematically investigated. The optimal CSE configuration, superior specific capacity (~160 mAh g⁻¹), low electrode polarization (~0.12 V), and remarkable cyclic stability (a capacity retention of 86.8%) were achieved during extended cycling (>200 cycles). In addition, with the optimal CSE structure, a high ionic conductivity (~2.83 × 10⁻⁴ S cm⁻¹) was demonstrated at an ambient temperature. The CSE configuration demonstrated in this work can be employed for designing highly durable CSEs with enhanced ionic conductivity and significantly reduced interfacial electrolyte/electrode resistance. Full article

Lithium-ion batteries are popular energy storage devices due to their high energy density. Solid electrolytes appear to be a potential replacement for flammable liquid electrolytes in lithium batteries. This inorganic/hybrid solid electrolyte is a composite of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) salt, (poly(vinylidene fluoride-hexafluoro propylene) (PVDF-HFP) polymer and sodium superionic conductor (NASICON)-type Li_1+xAl_xTi_2−x(PO₄)₃ (LATP) ceramic powder. The structure, morphology, mechanical behavior, and electrochemical performance of this composite solid electrolyte, based on various amounts of LiTFSI, were investigated. The lithium-ion transfer and conductivity increased as the LiTFSI lithium salt concentration increased. However, the mechanical strength apparently decreased once the percentage of LITFSI was over 60%. The hybrid electrolyte with 60% LiTFSI content showed high ionic conductivity of 2.14 × 10⁻⁴ S cm⁻¹, a wide electrochemical stability window (3–6 V) and good electrochemical stability. The capacity of the Li|60% LiTFSI/PVDF-HFP/LATP| LiFePO₄ solid-state lithium-metal battery was 103.8 mA h g⁻¹ at 0.1 C, with a high-capacity retention of 98% after 50 cycles. Full article

We here demonstrate the preparation of composite polymer electrolytes (CPEs) for Li-ion batteries, applicable for 3D printing process via fused deposition modeling. The prepared composites consist of modified poly(ethylene glycol) (PEG), lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) and SiO₂-based nanofillers. PEG was successfully end group modified yielding telechelic PEG containing either ureidopyrimidone (UPy) or barbiturate moieties, capable to form supramolecular networks via hydrogen bonds, thus introducing self-healing to the electrolyte system. Silica nanoparticles (NPs) were used as a filler for further adjustment of mechanical properties of the electrolyte to enable 3D-printability. The surface functionalization of the NPs with either ionic liquid (IL) or hydrophobic alkyl chains is expected to lead to an improved dispersion of the NPs within the polymer matrix. Composites with different content of NPs (5%, 10%, 15%) and LiTFSI salt (EO/Li⁺ = 5, 10, 20) were analyzed via rheology for a better understanding of 3D printability, and via Broadband Dielectric Spectroscopy (BDS) for checking their ionic conductivity. The composite electrolyte PEG 1500 UPy₂/LiTFSI (EO:Li 5:1) mixed with 15% NP-IL was successfully 3D printed, revealing its suitability for application as printable composite electrolytes. Full article

The proliferation of the internet of things (IoT) and other low-power devices demands the development of energy harvesting solutions to alleviate IoT hardware dependence on single-use batteries, making their deployment more sustainable. The propagation of energy harvesting solutions is strongly associated with technical performance, cost and aesthetics, with the latter often being the driver of adoption. The general abundance of light in the vicinity of IoT devices under their main operation window enables the use of indoor and outdoor photovoltaics as energy harvesters. From those, highly transparent solar cells allow an increased possibility to place a sustainable power source close to the sensors without significant visual appearance. Herein, we report the effect of hole transport layer Li-TFSI dopant content on semi-transparent, direct plasmonic solar cells (DPSC) with a transparency of more than 80% in the 450–800 nm region. The findings revealed that the amount of oxidized spiro-OMeTAD (spiro⁺TFSI⁻) significantly modulates the transparency, effective conductance and conditions of device performance, with an optimal performance reached at around 33% relative concentration of Li-TFSI concerning spiro-OMeTAD. The Li-TFSI content did not affect the immediate charge extraction, as revealed by an analysis of electron–phonon lifetime. Hot electrons and holes were injected into the respective layers within 150 fs, suggesting simultaneous injection, as supported by the absence of hysteresis in the I–V curves. The spiro-OMeTAD layer reduces the Au nanoparticles’ reflection/backscattering, which improves the overall cell transparency. The results show that the system can be made highly transparent by precise tuning of the doping level of the spiro-OMeTAD layer with retained plasmonics, large optical cross-sections and the ultrathin nature of the devices. Full article

In this work, blends of Poly(ethylene oxide), PEO, and poly(1,6-hexanediol), PHD, were prepared in a wide composition range. They were examined by Differential Scanning Calorimetry (DSC), Polarized Light Optical Microscopy (PLOM) and Wide Angle X-ray Scattering (WAXS). Based on the results obtained, the blends were partially miscible in the melt and their crystallization was a function of miscibility and composition. Crystallization triggered phase separation. In blends with higher PEO contents both phases were able to crystallize due to the limited miscibility in this composition range. On the other hand, the blends with higher PHD contents display higher miscibility and therefore, only the PHD phase could crystallize in them. A nucleation effect of the PHD phase on the PEO phase was detected, probably caused by a transference of impurities mechanism. Since PEO is widely used as electrolyte in lithium batteries, the PEO/PHD blends were studied with lithium bis(trifluoromethanesulfonyl) imide (LiTFSI), and the effect of Li-salt concentration was studied. We found that the lithium salt preferentially dissolves in the PEO phase without significantly affecting the PHD component. While the Li-salt reduced the spherulite growth rate of the PEO phase within the blends, the overall crystallization rate was enhanced because of the strong nucleating effect of the PHD component. The ionic conductivity was also determined for the blends with Li-salt. At high temperatures (>70 °C), the conductivity is in the order of ~10⁻³ S cm⁻¹, and as the temperature decreases, the crystallization of PHD was detected. This improved the self-standing character of the blend films at high temperatures as compared to the one of neat PEO. Full article

Ionic liquids are attractive and safe electrolytes for diverse electrochemical applications such as advanced rechargeable batteries with high energy densities. Their properties that are beneficial for energy storage and conversion include negligible vapor-pressure, intrinsic conductivity as well as high stability. To explore the suitability of a series of ionic liquids with small ammonium cations for potential battery applications, we investigated their thermal and transport properties. We studied the influence of the symmetrical imide-type anions bis(trifluoromethanesulfonyl)imide ([TFSI]⁻) and bis(fluorosulfonyl)imide ([FSI]⁻), side chain length and functionalization, as well as lithium salt content on the properties of the electrolytes. Many of the samples are liquid at ambient temperature, but their solidification temperatures show disparate behavior. The transport properties showed clear trends: the dynamics are accelerated for samples with the [FSI]⁻ anion, shorter side chains, ether functionalization and lower amounts of lithium salts. Detailed insight was obtained from the diffusion coefficients of the different ions in the electrolytes, which revealed the formation of aggregates of lithium cations coordinated by anions. The ionic liquid electrolytes exhibit sufficient stability in NMC/Li half-cells at elevated temperatures with small current rates without the need of additional liquid electrolytes, although Li-plating was observed. Electrolytes containing [TFSI]⁻ anions showed superior stability compared to those with [FSI]⁻ anions in battery tests. Full article

We report a new process technique for electrode manufacturing for all solid-state batteries. Porous electrodes are manufactured by a tape casting process and subsequently infiltrated by a plastic crystal polymer electrolyte (PCPE). With a following isostatic lamination process, the PCPE was further integrated deeply into the porous electrode layer, forming a composite electrode. The PCPE comprises the plastic crystal succinonitrile (SN), lithium conductive salt LiTFSI and polyacrylonitrile (PAN) and exhibits suitable thermal, rheological (ƞ = 0.6 Pa s @ 80 °C 1 s⁻¹) and electrochemical properties (σ > 10⁻⁴ S/cm @ 45 °C). We detected a lowered porosity of infiltrated and laminated electrodes through Hg porosimetry, showing a reduction from 25.6% to 2.6% (NCM infiltrated to laminated) and 32.9% to 4.0% (LTO infiltrated to laminated). Infiltration of PCPE into the electrodes was further verified by FESEM images and EDS mapping of sulfur content of the conductive salt. Cycling tests of full cells with NCM and LTO electrodes with PCPE separator at 45 °C showed up to 165 mAh/g at 0.03C over 20 cycles, which is about 97% of the total usable LTO capacity with a coulomb efficiency of between 98 and 99%. Cycling tests at 0.1C showed a capacity of ~128 mAh/g after 40 cycles. The C-rate of 0.2C showed a mean capacity of 127 mAh/g. In summary, we could manufacture full cells using a plastic crystal polymer electrolyte suitable for NCM and LTO active material, which is easily to be integrated into porous electrodes and which is being able to be used in future cell concepts like bipolar stacked cells. Full article

Conventional carbonate-based liquid electrolytes have safety issues related to their high flammability and easy leakage. Therefore, it is essential to develop alternative electrolytes for lithium-ion batteries (LIBs). As a potential candidate, solid-polymer electrolytes (SPEs) offer enhanced safety characteristics, while to be widely applied their performance still has to be improved. Here, we have prepared a series of UV-photocrosslinked flexible SPEs comprising poly(ethylene glycol) diacrylate (PEGDA), trimethylolpropane ethoxylate triacrylate (ETPTA), and lithium bis(trifluoromethane sulfonyl)imide (LiTFSI) salt, with the addition of polydimethylsiloxane with acrylated terminal groups (acryl-PDMS) to diminish the crystallinity of the poly(ethylene glycol) chain. Polysiloxanes have gained interest for the fabrication of SPEs due to their unique features, such as decrement of glass transition temperature (T_g), and the ability to improve flexibility and facilitate lithium-ion transport. Freestanding, transparent SPEs with excellent flexibility and mechanical properties were achieved without any supporting backbone, despite the high content of lithium salt, which was enabled by their networked structure, the presence of polar functional groups, and their amorphous structure. The highest ionic conductivity for the developed cross-linked SPEs was 1.75 × 10⁻⁶ S cm⁻¹ at room temperature and 1.07 × 10⁻⁴ S cm⁻¹ at 80 °C. The SPEs demonstrated stable Li plating/stripping ability and excellent compatibility toward metallic lithium, and exhibited high electrochemical stability in a wide range of potentials, which enables application in high-voltage lithium-ion batteries. Full article

In this work, we report the synthesis of ion-conductive gels, or ionic gels, via thiol-ene click reactions. The novel gel systems consist of the multifunctional thiol monomers tris[(3-mercaptopropionyloxy)-ethyl]-isocyanurate (TEMPIC), pentaerythritol tetrakis(3-mercaptopropionate) (PEMP), and dipentaerythritol hexakis(3-mercaptopionate) (DPMP) as joint molecules and bifunctional allyl ionic liquid (IL) as a crosslinker. The thiol-ene reaction was carried out in lithium bis(trifluoromethanesulfonyl)imide (Li-TFSI) in a propylene carbonate (PC) (1 M) solvent system via a photopolymerization process. The chemical structure and mechanical, thermal, and conductive properties of the gels were investigated using Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), compression tests, and impedance spectroscopy, respectively. The mechanical and conductive properties of the ionic gels were found to be largely dependent on the monomer content and functionalities of the joint molecules. TGA revealed good thermal stability of the gels up to 100 °C. An ionic conductivity of 4.89 mS cm⁻¹ was realized at room temperature (298 K) for low-functional thiol monomers, and a further increase in ionic conductivity was observed with an increase in Li+ ion content and temperature. Full article

Promising electrochemical and dynamical properties, as well as high thermal stability, have been the driving forces behind application of ionic liquids (ILs) and polymerized ionic liquids (PILs) as electrolytes for high-temperature lithium-ion batteries (HT-LIBs). Here, several ternary lithium-salt/IL/PIL electrolytes (PIL_el) have been investigated for synergies of having both FSI and TFSI anions present, primarily in terms of physico-chemical properties, for unique application in HT-LIBs operating at 80 °C. All of the electrolytes tested have low T_g and are thermally stable ≥100 °C, and with TFSI as the exclusive anion the electrolytes (set A) have higher thermal stabilities ≥125 °C. Ionic conductivities are in the range of 1 mS/cm at 100 °C and slightly higher for set A PIL_el, which, however, have lower oxidation stabilities than set B PIL_el with both FSI and TFSI anions present: 3.4–3.7 V vs. 4.2 V. The evolution of the interfacial resistance increases for all PIL_el during the first 40 h, but are much lower for set B PIL_el and generally decrease with increasing Li-salt content. The higher interfacial resistances only influence the cycling performance at high C-rates (1 C), where set B PIL_el with high Li-salt content performs better, while the discharge capacities at the 0.1 C rate are comparable. Long-term cycling at 0.5 C, however, shows stable discharge capacities for 100 cycles, with the exception of the set B PIL_el with high Li-salt content. Altogether, the presence of both FSI and TFSI anions in the PIL_el results in lower ionic conductivities and decreased thermal stabilities, but also higher oxidation stabilities and reduced interfacial resistances and, in total, result in an improved rate capability, but compromised long-term capacity retention. Overall, these electrolytes open for novel designs of HT-LIBs. Full article