Saeed Mardi

Nickel‐rich layered cathodes, LiNi _x Mn _y Co _{1 −x −y} O ₂ (NMC), are promising materials for next‐generation Li‐ion batteries due to their high energy/power densities; however, capacity fading remains a major limitation. While fluorinated electrolytes have enabled optimal performance, their environmental and safety issues prompt the investigation of fluorine‐free alternatives. Here, we evaluate a fluorine‐free electrolyte based on lithium bis(oxalato)borate in NMC811||Si–graphite full cells operated at low and high cutoff voltages, comparing its performance with that of a LiPF ₆ ‐based electrolyte. The reactions at the cathode–electrolyte interface (CEI) are the primary cause of capacity fade, leading to electrolyte decomposition, layer disorder, and irreversible phase transitions. Increasing the cutoff voltage and the use of a fluorine‐free electrolyte exacerbate these reactions, resulting in more rapid capacity loss. Differential scanning calorimetry characterization of harvested electrodes from cycled cells with both electrolytes indicates that the anode exhibits lower thermal stability than the cathode and that the thermal stability of the anode is enhanced when using the fluorine‐free electrolyte. Overall, the results indicate that the fluorine‐free electrolyte performance is limited at high cutoff voltage by the cathode and highlights the need for improved CEI‐based additives or cathode coatings to allow competitive performance of more environmentally friendly electrolytes with fluorine‐free components.

Fluorinated compounds, including polyvinylidene fluoride (PVdF) binder and lithium hexafluorophosphate salt, are considered essential components in lithium-ion batteries due to their ability to provide good performance and cycle life. However, these compounds raise potential environmental concerns, as they can lead to the formation of toxic, corrosive and persistent compounds, such as hydrofluoric acid, phosphorus pentafluoride (PF₅) and per- and polyfluoroalkyl substances. In this study, the effects of fluorine-free electrolyte consisting of lithium bis(oxalato)borate (LiBOB) salt and vinylene carbonate (VC) addtive and an aqueous-based binder based on carboxymethyl cellulose (CMC) and latex are investigated for full cells combining a silicon–graphite composite anode with LiNi_0.6Mn_0.2Co_0.2O₂ cathodes. Higher capacity retention is obtained at C/2 after 500 cycles with the fluorine-free binder in the cathode (61 and 65% for the fluorine-free and fluorinated electrolytes, respectively) compared to the PVdF-based binder (58 and 56% respectively). X-ray photoelectron spectroscopy analysis of the passivating layers on the cathode and anode across the four systems revealed a F-rich interfacial composition in the presence of the fluorinated electrolyte, while the fluorine-free electrolyte led to the formation of oxygen-rich layers at the interphases. Despite the chemical differences, both layers protect the cathode and anode during cycling, resulting in similar electrochemical performance. Moreover, the solid electrolyte interphase composition on the anode is dependent on the cathode’s formulation. The aqueous-processed cathode resulted in higher coverage of the active material, which mitigated salt decomposition and facilitated the formation of a more stable passivating layer. This contributed to higher capacity retention despite a lower initial discharge capacity compared to the PVdF-based cathode. This study demonstrates the potential of fluorine-free components (electrolyte and binder with aqueous-processed cathode) to achieve high-energy-density full cells with comparable performance to conventional highly fluorinated lithium-ion batteries.

Nickel-rich layered cathodes, LiNixMnyCo₁₋ₓ₋ᵧO₂ (NMC) are promising materials for next-generation Li-ion batteries due to their high energy/power densities and long cycle life, however, capacity fading remains a major limitation. While fluorinated electrolytes have enabled optimal performance, their environmental and safety issues prompt the investigation of fluorine-free alternatives. Here, we evaluate a fluorine-free electrolyte based on lithium bis(oxalato)borate in NMC811||Si–Graphite full cells operated at low and high cutoff voltages, comparing its performance with that of a LiPF₆-based electrolyte. The cathode–electrolyte reactions are the primary cause of capacity fade, leading to electrolyte decomposition, layer disorder, and irreversible phase transitions. Increasing the cutoff voltage and the use of a fluorine-free electrolyte exacerbate these reactions, resulting in more rapid capacity loss. Differential scanning calorimetry characterization of harvested electrodes from cycled cells with both electrolytes indicated that the anode limits the thermal stability at lower temperatures than the cathode, and it is higher for the fluorine-free electrolyte. Overall, the results indicate that the fluorine-free electrolyte performance is limited at high cutoff voltage by the cathode and highlights the need for improved CEI-based additives or cathode coatings to allow competitive performance of more environmentally friendly electrolytes with fluorine-free components.

Fluorinated compounds, including polyvinylidene fluoride (PVdF) binder and lithium hexafluorophosphate salt, are considered essential components in lithium-ion batteries due to their ability to provide good performance and cycle life. However, these compounds raise potential environmental concerns, as they can lead to the formation of toxic, corrosive and persistent compounds, such as hydrofluoric acid, phosphorus pentafluoride (PF5) and per- and polyfluoroalkyl substances. In this study, the effects of fluorine-free electrolyte and binder are investigated for full cells combining a silicon–graphite composite anode with LiNi0.6Mn0.2Co0.2O2 cathodes. Higher capacity retention is obtained at C/2 after 500 cycles with the fluorine-free binder in the cathode (61 and 65% for the fluorine-free and fluorinated electrolytes, respectively) compared to the PVdF-based binder (58 and 56% respectively). X-ray photoelectron spectroscopy analysis of the passivating layers on the cathode and anode across the four systems revealed a F-rich interfacial composition in the presence of the fluorinated electrolyte, while the fluorine-free electrolyte led to the formation of oxygen-rich layers at the interphases. Despite the chemical differences, both layers protect the cathode and anode during cycling, resulting in similar electrochemical performance. Moreover, the solid electrolyte interphase composition on the anode is dependent on the cathode’s formulation. The aqueous-processed cathode showed a better coverage of the active material preventing salt decomposition and allowing the additives to form a more stable passivating layer that improved the overall cycling performance compared to the cell with PVdF-based cathode. This study demonstrates the potential of fluorine-free components (electrolyte and binder with aqueous-processed cathode) to achieve high-energy-density full cells with comparable performance to conventional highly fluorinated lithium-ion batteries.

High-capacity stretchable batteries are crucial for next-generation wearables to enable long-term operation and mechanical conformability with the human user. In existing stretchable battery designs, increasing the active material to yield higher capacity often leads to thicker and stiffer solid electrodes with poor mechanical properties. Here, we present a concept that transfers the physical property of a battery electrode from a conventional solid into a fluid state. The mechanical and electrochemical properties of the electrode rely on the viscosity of fluids rather than Young’s modulus of solids. Fluids conform easily into any shape with minimal force, making them intrinsically deformable. This decouples the electrochemical and mechanical property of the redox-active electrofluid, leading to higher capacities with more active material loading without stiffening the cell. The cell showed excellent capacity retention over 500 charge-discharge cycles and mechanical robustness up to 100% strain. Our work provides a technological solution for stretchable batteries that balances capacity and mechanical performance.

Herein, the effect of electrode anodization on the enhancement of the reversibility and the electrochemical activity of the redox‐active molecule alizarin in both positive and negative electrodes is reported. Alizarin is a bifunctional plant‐based anthraquinone redox species that exhibits irreversibility at positive potential (versus Ag/AgCl). The results show that the anodization of carbon paper increases surface area and introduces functional groups, which in turn promotes reversibility at the positive potential. To demonstrate the applicability of our technique, the modified electrodes are used in a symmetric aqueous organic redox flow battery, showing a significant improvement in capacity retention and Coulombic efficiency compared to pristine carbon electrodes.

A stretchable battery design that uses sustainable plant-based materials and enables high electrochemical and mechanical performance and is biodegradable at the end-of-life.

The increasing energy demand and the ever more pressing need for clean technologies of energy conversion pose one of the most urgent and complicated issues of our age. Thermoelectricity, namely the direct conversion of waste heat into electricity, is a promising technique based on a long-standing physical phenomenon, which still has not fully developed its potential, mainly due to the low efficiency of the process. In order to improve the thermoelectric performance, a huge effort is being made by physicists, materials scientists and engineers, with the primary aims of better understanding the fundamental issues ruling the improvement of the thermoelectric figure of merit, and finally building the most efficient thermoelectric devices. In this Roadmap an overview is given about the most recent experimental and computational results obtained within the Italian research community on the optimization of composition and morphology of some thermoelectric materials, as well as on the design of thermoelectric and hybrid thermoelectric/photovoltaic devices.

Ionic thermoelectric supercapacitors (ITESCs) have recently been developed for converting low‐grade waste heat into electricity. Until now, most reports of ITESCs have been focused on the development of electrolytes, which then have been combined with a specific electrode material. Here, it is demonstrated that the electrode is not only critical for electrical energy storage but also greatly affects the effective thermopower (S_eff) of an ITESC. It is shown that the same ion gel can generate a positive thermopower in an ITESC when using gold nanowire (AuNW) electrodes, while generating a negative thermopower when using poly(3,4‐ethylendioxythiophene):polystyrene sulfonate (PEDOT:PSS) electrodes. The achieved negative sign of the S_eff could be attributed to the Donnan exclusive effect from the polyanions in the PEDOT:PSS electrodes. After examining the thermovoltage, capacitance and charge retention performance of the two ITESCs, it is concluded that PEDOT:PSS is superior to AuNWs as electrodes. Moreover, a new strategy of constructing an ionic thermopile of multiple p‐ and n‐type legs is achieved by series‐connecting these legs with same electrolyte but different electrodes. Using interfacial effect at ionic gels/PEDOT:PSS electrode interface, an enhanced thermoelectric effect in ITESCs is obtained, which constitutes one more step towards efficient, low‐cost, flexible, and printable ionic thermoelectric modules for energy harvesting.

Organic materials have attracted considerable attention for thermoelectric (TE) applications. Given their potential as wearable power generators, there is an urgent need to develop organic TE materials that possess superior electronic properties as well as excellent mechanical and environmental stability. Here, we develop paper-based TE materials using the poly(3,4-ethylenedioxythiophene): polystyrenesulfonate (PEDOT:PSS), graphene nanoplatelets (GNPs), and a starch-based biopolymer as a binder for GNPs. The device fabrication consists of spraying the biopolymer/GNP ink onto the cellulose paper followed by spraying the PEDOT:PSS solution. Further enhancement of TE properties was obtained by adding an ionic liquid (IL), bis(trifluoromethane)sulfonimide lithium salt to the PEDOT:PSS solution. Upon addition of the IL, the electrical conductivity of as-fabricated PEDOT:PSS films increased nearly two orders of magnitude. The electrical conductivity increases with GNPs' content due to formation of an effective electrical percolation network. Interestingly, incorporating GNPs simultaneously improves the Seebeck coefficient. Raman measurements suggest that the concurrent enhancement of the Seebeck coefficient and electrical conductivity might be related to the chemical bonding between the conducting polymer chains and the filler. In addition, these composites display remarkable flexibility at various bending angles and environmental stability without losing their original conductivity after three months of exposure to ambient conditions.