Structure–Performance Correlation of Nanocellulose‐Based Polymer Electrolytes for Efficient Quasi‐solid DSSCs

Nanoscale microfibrillated cellulose (NMFC) was introduced into a light-cured polymeric matrix to result in a green, cheap, and highly efficient quasi-solid electrolyte for the next-generation of bio-based dye-sensitized solar cells. The effect of NMFC on the photovoltaic parameters and performance of the resulting photo-electrochemical cells was thoroughly investigated, and a noticeable increase in both the photocurrent (due to optical phenomena) and the photovoltage (through a shielding effect on the recombination reactions) was demonstrated. Upon thorough optimization of the amount of NMFC introduced into the polymeric network, sunlight conversion efficiencies as high as 7.03 and 8.25 % were achieved at simulated light intensities of 1.0 and 0.4 sun, respectively. Furthermore and outstandingly, the addition of NMFC positively affected the long-term stability of the device, which was able to retain >95 % of its initial efficiency after 500 h of extreme aging condition

Cobalt-Based Electrolytes for Dye-Sensitized Solar Cells: Recent Advances towards Stable Devices

Redox mediators based on cobalt complexes allowed dye-sensitized solar cells (DSCs) to achieve efficiencies exceeding 14%, thus challenging the emerging class of perovskite solar cells. Unfortunately, cobalt-based electrolytes demonstrate much lower long-term stability trends if compared to the traditional iodide/triiodide redox couple. In view of the large-scale commercialization of cobalt-based DSCs, the scientific community has recently proposed various approaches and materials to increase the stability of these devices, which comprise gelling agents, crosslinked polymeric matrices and mixtures of solvents (including water). This review summarizes the most significant advances recently focused towards this direction, also suggesting some intriguing way to fabricate third-generation cobalt-based photoelectrochemical devices stable over time

PEO/LAGP hybrid solid polymer electrolytes for ambient temperature lithium batteries by solvent-free, “one pot” preparation

Here, we report hybrid solid polymer electrolytes (HSPE) obtained by rapid, truly solvent-free, thus scalable preparation process. HSPE composition is very simple: a LiTFSI added poly(ethylene oxide) (PEO) polymer matrix encompassing NASICON-type Li1.5Al0.5Ge1.5(PO4)3 (LAGP) super Li+ ion conducting ceramic. Homogeneous, self-standing, mechanically robust solid electrolyte films are obtained by simply mixing in “one pot” and hot pressing the solid mixture of dry powders at moderate temperature. Noteworthy, unlike several other super ionic conductors used for composite electrolytes, LAGP is relatively stable in air atmosphere and can be processed in a dry-room, which is more favorable, cheap and scalable than Ar-filled dry glove box for industrial fabrication of safe lithium batteries. The proper, homogeneous mixing of LAGP powder, PEO and LiTFSI leads to HSPE with interesting electrochemical behavior in lab-scale lithium cells, especially under high current regimes, and even at ambient temperature. HSPE-based cells outperform the PEO-LiTFSI-based counterpart, in terms of specific capacity output (about 70% of the theoretical value retained at very high 2C rate), limited fading and excellent Coulombic efficiency (>99.5%) even at low rate. Interfacial stability issues remain to be solved, chiefly linked to the reactivity of LAGP in contact with lithium metal, but results here proposed represent a step further toward truly all-solid-state batteries conceived for high energy/power technologies, assuring safety and performance in a wide range of operating conditions

Protic Ionic Liquids Based Crosslinked Polymer Electrolytes: A New Class of Solid Electrolytes for Energy Storage Devices

Herein, the preparation of an innovative crosslinked polymer electrolyte (PEO_HPyr) encompassing protic ionic liquids (PILs) displaying high ionic conductivity, wide thermal, and electrochemical stability is reported, thus suitable for use in safe energy storage devices. The first example of an all‐solid‐state electrochemical double layer capacitor (EDLC) containing a PEO_HPyr‐based electrolyte is presented, which shows high performance at ambient temperature and exceptional stability. Furthermore, the first example of a PIL‐based lab‐scale lithium‐metal cell with lithium iron phosphate cathodes is also presented, which provides almost full capacity (i.e., 150 mAh g−1 at C/20) and highly reversible cycling at ambient conditions and different current rates. The excellent results obtained clearly demonstrate that PIL‐based crosslinked polymer electrolytes represent a new and very interesting class of solid electrolytes for energy storage devices

Unveiling Oxygen Redox Activity in P2-Type NaxNi0.25Mn0.68O2 High-Energy Cathode for Na-Ion Batteries

Na-ion batteries are emerging as convenient energy-storage devices for large-scale applications. Enhanced energy density and cycling stability are key in the optimization of functional cathode materials such as P2-type layered transition metal oxides. High operating voltage can be achieved by enabling anionic reactions, but irreversibility of O2–/O2n–/O2 evolution still limits this chance, leading to extra capacity at first cycle that is not fully recovered. Here, we dissect this intriguing oxygen redox activity in Mn-deficient NaxNi0.25Mn0.68O2 from first-principles, by analyzing the formation of oxygen vacancies and dioxygen complexes at different stages of sodiation. We identify low-energy intermediates that release molecular O2 at high voltage, and we show how to improve the overall cathode stability by partial substitution of Ni with Fe. These new atomistic insights on O2 formation mechanism set solid scientific foundations for inhibition and control of this process toward the rational design of new anionic redox-active cathode materials

Ambipolar suppression of superconductivity by ionic gating in optimally-doped BaFe2(As,P)2 ultrathin films

Superconductivity (SC) in the Ba-122 family of iron-based compounds can be controlled by aliovalent or isovalent substitutions, applied external pressure, and strain, the combined effects of which are sometimes studied within the same sample. Most often, the result is limited to a shift of the SC dome to different doping values. In a few cases, the maximum SC transition at optimal doping can also be enhanced. In this work, we study the combination of charge doping together with isovalent P substitution and strain by performing ionic gating experiments on BaFe$_2$(As$_{0.8}$P$_{0.2}$)$_2$ ultrathin films. We show that the polarization of the ionic gate induces modulations to the normal-state transport properties that can be mainly ascribed to surface charge doping. We demonstrate that ionic gating can only shift the system away from the optimal conditions, as the SC transition temperature is suppressed by both electron and hole doping. We also observe a broadening of the resistive transition, which suggests that the SC order parameter is modulated nonhomogeneously across the film thickness, in contrast with earlier reports on charge-doped standard BCS superconductors and cuprates.Comment: 10 pages, 5 figure

Siloxane Diacrylate-based All-Solid Polymer Electrolytes for Lithium Batteries

Fully solid polymer electrolyte (SPE) membranes were prepared by UV induced free radical polymerisation (UV-curing) of acrylated siloxane polyalkyleneoxide copolymers in the presence of different lithium salts. The main chain contains locally mobile segments of ethoxy groups as part of the copolymer, and these moieties can provide coordination sites for the mobility of Li+ ions. The materials are produced through a solvent free procedure, and used as ion-conducting media as well as a separator in high temperature lithium-based batteries. The preparation process is easy, simple and versatile. The final product obtained demonstrates good mechanical integrity due to the highly cross-linked nature of the polymer network, and wide thermal stability. The membranes are also soft, easy to manage and transparent. They also exhibit acceptable ionic conductivity and wide electrochemical stability window