Electrolytes for Sodium Ion Batteries: The Current Transition from Liquid to Solid and Hybrid systems.

Sodium-ion batteries (NIBs) have recently garnered significant interest in being employed alongside conventional lithium-ion batteries, particularly in applications where cost and sustainability are particularly relevant. The rapid progress in NIBs will undoubtedly expedite the commercialization process. In this regard, tailoring and designing electrolyte formulation is a top priority, as they profoundly influence the overall electrochemical performance and thermal, mechanical, and dimensional stability. Moreover, electrolytes play a critical role in determining the system's safety level and overall lifespan. This review delves into recent electrolyte advancements from liquid (organic and ionic liquid) to solid and quasi-solid electrolyte (dry, hybrid, and single ion conducting electrolyte) for NIBs, encompassing comprehensive strategies for electrolyte design across various materials, systems and their functional applications. Our objective is to offer strategic direction for the systematic production of safe electrolytes and to investigate the potential applications of these designs in real-world scenarios while thoroughly assessing the current obstacles and forthcoming prospects within this rapidly evolving field. This article is protected by copyright. All rights reserved.

Evaluation of Electronic-Ionic Transport Properties of a Mg/Zr-Modified LiNi0.5Mn1.5O4 Cathode for Li-Ion Batteries.

There is an enormous drive for moving toward cathode material research in LIBs due to the proposal of zero-emission electric vehicles together with the restriction of cathode materials in design. LiNi0.5Mn1.5O4 (LNMO) attracts great research interests as high-voltage Co-free cathodes in LIBs. However, a more extensive study is required for LNMO due to its poor electrochemical performance, especially at high temperature, because of the instability of the LNMO interface. Herein, we design structural modifications using Mg and Zr to alleviate the above-mentioned drawbacks by limiting Mn dissolution and tailoring interstitial sites (which are shown by structural and electrochemical characterizations). This strategy enhances the cycle life up to 1000 cycles at both 25 and 50 °C. In addition, a thorough characterization by impedance spectroscopy is applied to give an insight into the electronic and ionic transport properties and the intricate phase transitions occurring upon oxidation and reduction.

Oxide Coating Role on the Bulk Structural Stability of Active LiMn2O4 Cathodes.

The protective coating of the electrode materials is a known source of improvement of the cycling performances in battery devices. In the case of the LiMn2O4 cathodes, the coating with a thin alumina layer has been proven to show performance efficiency. However, the precise mechanism of its effect on the performance improvement of the electrodes is still not clear. In this work we investigate alumina-coating-induced effects on the structural dynamics of the active materials in correlation to the modified solid electrolyte interface dynamics. The local structures of coated and uncoated samples at different galvanostatic points are studied by both soft X-ray absorption measurements at the Mn L-edges and O K-edge (in total electron yield mode) and hard X-ray absorption at the Mn K-edge (in transmission mode). The different probing depths of the employed techniques allowed us to study the structural dynamics both at the surface and within the bulk of the active material. We demonstrate that the coating successfully hinders the Mn3+ disproportionation and, hence, the degradation of the active material. Side products (layered Li2MnO3 and MnO) and changes in the local crystal symmetry with formation of Li2Mn2O4 are observed in uncoated electrodes. The role of alumina coating on the stability of the passivation layer and its consequent effect on the structural stability of the bulk active materials is discussed.

Chemical, Thermal and Mechanical Characterization of Licorice Root, Willow, Holm Oak, and Palm Leaf Waste Incorporated into Maleated Polypropylene (MAPP).

The effect of four lignocellulosic waste fillers on the thermal and mechanical properties of biocomposites was investigated. Powdered licorice root, palm leaf, holm oak and willow fillers were melt compounded with polypropylene at two different weight contents, i.e., 10 and 30, and then injection molded. A commercially available maleated coupling agent was used to improve the filler/matrix interfacial adhesion at 5 wt.%. Composites were subjected to chemical (FTIR-ATR), thermal (TGA, DSC, DMA) and mechanical (tensile, bending and Charpy impact) analyses coupled with a morphological investigation by scanning electron microscopy. Although similarities among the different formulations were noted, holm oak fillers provided the best combination of thermal and mechanical performance. In particular, at 30 wt.% content with coupling agent, this composite formulation displayed remarkable increases in tensile strength and modulus, flexural strength and modulus, of 28% and 110%, 58% and 111%, compared to neat PP, respectively. The results imply that all these lignocellulosic waste fillers can be used successfully as raw materials for biocomposites, with properties comparable to those featured by other natural fillers.

Structural and Interfacial Characterization of a Sustainable Si/Hard Carbon Composite Anode for Lithium-Ion Batteries.

The effects of a biomass-derived hard carbon matrix and a sustainable cross-linked binder are investigated as electrode components for a silicon-based anode in lithium-ion half-cells, in order to reduce the capacity fade due to volume expansion and shrinkage upon cycling. Ex situ Raman spectroscopy and impedance spectroscopy are used to deeply investigate the structural and interfacial properties of the material within a single cycle and upon cycling. An effective buffering of the volume changes of the composite electrode is evidenced, even at a high Si content up to 30% in the formulation, resulting in the retention of structural and interfacial integrity. As a result, a high capacity performance and a very good rate capability are displayed even at high current densities, with a stable cycling behavior and low polarization effects.

Role of the voltage window on the capacity retention of P2-Na2/3[Fe1/2Mn1/2]O2 cathode material for rechargeable sodium-ion batteries.

P2-Na2/3[Fe1/2Mn1/2]O2 layered oxide is a promising high energy density cathode material for sodium-ion batteries. However, one of its drawbacks is the poor long-term stability in the operating voltage window of 1.5-4.25 V vs Na+/Na that prevents its commercialization. In this work, additional light is shed on the origin of capacity fading, which has been analyzed using a combination of experimental techniques and theoretical methods. Electrochemical impedance spectroscopy has been performed on P2-Na2/3[Fe1/2Mn1/2]O2 half-cells operating in two different working voltage windows, one allowing and one preventing the high voltage phase transition occurring in P2-Na2/3[Fe1/2Mn1/2]O2 above 4.0 V vs Na+/Na; so as to unveil the transport properties at different states of charge and correlate them with the existing phases in P2-Na2/3[Fe1/2Mn1/2]O2. Supporting X-ray photoelectron spectroscopy experiments to elucidate the surface properties along with theoretical calculations have concluded that the formed electrode-electrolyte interphase is very thin and stable, mainly composed by inorganic species, and reveal that the structural phase transition at high voltage from P2- to "Z"/OP4-oxygen stacking is associated with a drastic increased in the bulk electronic resistance of P2-Na2/3[Fe1/2Mn1/2]O2 electrodes which is one of the causes of the observed capacity fading.

Fe3O4/Graphene Composite Anode Material for Fast-Charging Li-Ion Batteries.

Composite anode material based on Fe3O4 and reduced graphene oxide is prepared by base-catalysed co-precipitation and sonochemical dispersion. Structural and morphological characterizations demonstrate an effective and homogeneous embedding of Fe3O4 nanoparticles in the carbonaceous matrix. Electrochemical characterization highlights specific capacities higher than 1000 mAh g-1 at 1C, while a capacity of 980 mAhg-1 is retained at 4C, with outstanding cycling stability. These results demonstrate a synergistic effect by nanosize morphology of Fe3O4 and inter-particle conductivity of graphene nanosheets, which also contribute to enhancing the mechanical and cycling stability of the electrode. The outstanding capacity delivered at high rates suggests a possible application of the anode material for high-power systems.

Fast File Transfers from IoT Devices by Using Multiple Interfaces.

The Internet-of-Things (IoT) is a modern technological revolution that enables communication amongst a plethora of different devices. To date, about 30 billion devices have been connected to the internet and more than 75 billion devices are probably to be connected worldwide by 2025. These can range from small sensors and actuators to larger devices such as smartphones, drones or even buildings and interconnected cars. Devices are often mobile and battery powered thus their communication requires fast and energy efficient solutions. To this end, this paper studies the use of multi-interface communication for fast and energy efficient communication. In particular, we consider the basic operation of data transfer between smartphones in the form of files. This task can be performed for backup purposes, and hence it represents a useful and frequent operation that users perform. Our aim is to provide a new and easy means that optimises file transfers with respect to time and energy consumption. In particular, as smartphones are endowed with various connecting interfaces like Bluetooth, WiFi and 4G, we conduct experimental studies by varying different parameters in order to understand the best setting, including which interface is more appropriate to accomplish file transfer. To this respect, we also implemented an innovative and light app that allows the use of two or more interfaces concurrently. The experimental results show how the coupling of some interfaces might be effective in terms of time, while consuming a negligible amount of energy. Actually, such results become more and more interesting as the size of the file to be transferred grows. The best combination experienced is by making use of WiFi at 5 GHz concurrently with 4G, whereas WiFi at 2.4 GHz caused interference complications.

Tin-Decorated Reduced Graphene Oxide and NaLi0.2Ni0.25Mn0.75O as Electrode Materials for Sodium-Ion Batteries.

A tin-decorated reduced graphene oxide, originally developed for lithium-ion batteries, has been investigated as an anode in sodium-ion batteries. The composite has been synthetized through microwave reduction of poly acrylic acid functionalized graphene oxide and a tin oxide organic precursor. The final product morphology reveals a composite in which Sn and SnO2 nanoparticles are homogenously distributed into the reduced graphene oxide matrix. The XRD confirms the initial simultaneous presence of Sn and SnO2 particles. SnRGO electrodes, prepared using Super-P carbon as conducting additive and Pattex PL50 as aqueous binder, were investigated in a sodium metal cell. The Sn-RGO showed a high irreversible first cycle capacity: only 52% of the first cycle discharge capacity was recovered in the following charge cycle. After three cycles, a stable SEI layer was developed and the cell began to work reversibly: the practical reversible capability of the material was 170 mA·h·g-1. Subsequently, a material of formula NaLi0.2Ni0.25Mn0.75O was synthesized by solid-state chemistry. It was found that the cathode showed a high degree of crystallization with hexagonal P2-structure, space group P63/mmc. The material was electrochemically characterized in sodium cell: the discharge-specific capacity increased with cycling, reaching at the end of the fifth cycle a capacity of 82 mA·h·g-1. After testing as a secondary cathode in a sodium metal cell, NaLi0.2Ni0.25Mn0.75O was coupled with SnRGO anode to form a sodium-ion cell. The electrochemical characterization allowed confirmation that the battery was able to reversibly cycle sodium ions. The cell's power response was evaluated by discharging the SIB at different rates. At the lower discharge rate, the anode capacity approached the rated value (170 mA·h·g-1). By increasing the discharge current, the capacity decreased but the decline was not so pronounced: the anode discharged about 80% of the rated capacity at 1 C rate and more than 50% at 5 C rate.

Anatase TiO2 as a Cheap and Sustainable Buffering Filler for Silicon Nanoparticles in Lithium-Ion Battery Anodes.

The design of effective supporting matrices to efficiently cycle Si nanoparticles is often difficult to achieve and requires complex preparation strategies. In this work, we present a simple synthesis of low-cost and environmentally benign aAnatase TiO2 nanoparticles as buffering filler for Si nanoparticles (Si@TiO2 ). The average anatase TiO2 crystallite size was approximately 5 nm. A complete structural, morphological, and electrochemical characterization was performed. Electrochemical test results show very good specific capacity values of up to 1000 mAh g-1 and cycling at several specific currents, ranging from 500 to 2000 mA g-1 , demonstrating a very good tolerance to high cycling rates. Postmortem morphological analysis shows very good electrode integrity after 100 cycles at 500 mA g-1 specific current.

Is the Solid Electrolyte Interphase an Extra-Charge Reservoir in Li-Ion Batteries?

Advanced metal oxide electrodes in Li-ion batteries usually show reversible capacities exceeding the theoretically expected ones. Despite many studies and tentative interpretations, the origin of this extra-capacity is not assessed yet. Lithium storage can be increased through different chemical processes developing in the electrodes during charging cycles. The solid electrolyte interface (SEI), formed already during the first lithium uptake, is usually considered to be a passivation layer preventing the oxidation of the electrodes while not participating in the lithium storage process. In this work, we combine high resolution soft X-ray absorption spectroscopy with tunable probing depth and photoemission spectroscopy to obtain profiles of the surface evolution of a well-known prototype conversion-alloying type mixed metal oxide (carbon coated ZnFe2O4) electrode. We show that a partially reversible layer of alkyl lithium carbonates is formed (∼5-7 nm) at the SEI surface when reaching higher Li storage levels. This layer acts as a Li reservoir and seems to give a significant contribution to the extra-capacity of the electrodes. This result further extends the role of the SEI layer in the functionality of Li-ion batteries.

Correlation of AC-impedance and in situ X-ray spectra of LiCoO2.

In-situ X-ray and AC-impedance spectra have been obtained simultaneously during the deintercalation of lithium from LiCoO2 using a specially designed electrochemical cell. The AC-dispersions have been correlated with the cell parameters obtained from the X-ray spectra. The correlation confirms previous hypothesis on the interpretation of the AC-dispersions in terms of an equivalent circuit comprising an element that relates the change of the intrinsic electronic conductivity, occurring at the early stages of deintercalation, to the semiconductor to metal transition caused by the change of the cell parameters.