High Cycle Life Research Articles

Heteroatom-Doped Carbon-Shelled Iron Phosphide Microcuboids as Freestanding Negative Electrodes for Long Cycling Sodium-Ion Batteries

Energy storage devices (ESDs) have become indispensable for maximum renewable energy penetration and progress towards the elimination of fossil fuels in electricity generation. Also, high-performance ESDs are urgently needed for wearable and flexible devices, electric vehicles, and internet of things (IOT) applications. Lithium-ion batteries (LIBs) presently occupy the largest share of the EES market, however the cost-per watt stored is too high and the finite supply of Li means that they cannot offer a long-term solution to the world’s energy challenge. On the other hand, sodium-ion batteries (SIBs) are regarded as complementary ESDs and potential replacements for LIBs due to their relatively lower cost, abundance, and uniform global distribution of Na.[1] Furthermore, SIBs can operate in a wide temperature range and inert with Al, benefiting the construction of low cost and safe ESDs. Nonetheless, the performance of SIBs is limited by sluggish diffusion of Na+ in Na-insertion materials owing to large size of Na+ (1.02 Å).[2]The major challenge to developing SIBs is the lack of suitable electrode materials capable of efficiently accommodating Na+. SIBs are rocking-chair cells like LIBs, however, Na-ion storage in traditional graphite is extremely poor (< 35 mAh g-1) due to insufficient interlayer spacing.[3] Phosphorous presents the highest theoretical capacity (2596 mAh g-1) for a SIB anode, however, it suffers from poor cycling and large volume expansion (490 %) during sodiation/desodiation.[4,5] Low cost and environmentally benign iron phosphides present slightly better volume expansion and a theoretical capacity of 926 mAh g-1, but its charge storage mechanism is unclear.[6] The lack of suitable SIB anode with high capacity and long cycle life remains a major hurdle to the full-scale development of SIBs.In this work, we synthesized core-shell FeP microcuboids on freestanding carbon cloths substrate as a high capacity (< 800 mAh g-1), long-cycling anode for SIBs. The synthesized FeP microcuboids exhibit distinct physical and morphological features for efficient sodium-ion storage. It possesses a porous core within a 10 nm carbon shell, which enhances the surface area, enable fast Na+ diffusion and buffers the FeP anode against large volume variations during cycling. The integration of different heteroatoms including fluorine and nitrogen successfully improved the electronic conductivity and structural stability. Finally, using techniques such as in-situ X-ray diffraction analysis and ex-situ TEM and electroanalytical methods, we probed the conversion reaction storage mechanism and uncovered a pseudocapacitive dominated storage process. Finally, our work provides crucial insights on the rational design of high-performing metal-based phosphide anodes for alternative-ion batteries.

Atomic Layer Deposition of Lithium Borate and Borophosphate Thin Films for Lithium-Ion Battery Applications

Lithium-ion batteries (LiBs) are widely used in portable electronic devices and electric vehicles because of their high energy density and long cycle life. However, their performance is limited by unwanted side reactions that occur at the electrolyte-electrode interface during charge/discharge cycles.Previous studies have indicated that the application of a conformal and ultra-thin protective coating on the electrode surface through atomic layer deposition (ALD) is a promising strategy to prevent these undesired side reactions [1]. Due to their high stability, metal phosphates are deemed a promising class of materials for protective coatings, and several studies have focused on ALD of metal phosphates [2], with lithium phosphate as a particularly relevant material. However, the low ionic conductivity, as evidenced by the reported value of 1.4 x 10-10 S cm-1 with an activation energy of 0.92 eV for crystalline Li3PO4 films deposited by ALD [3] may hinder the flow of lithium ions through the coating. It has been shown, albeit using other deposition techniques, that the inclusion of borate species can enhance the ionic conductivity of phosphate materials, including lithium phosphate [4]. However, lithium borates exhibit a more narrow electrochemical stability window. Here, we investigate the combination of lithium phosphate and lithium borate into a new, intermixed ALD coating, i.e. lithium borophosphate, aiming to increase the ionic conductivity of the protective coating while preserving as much as possible its electrochemical stability.To date, only one ALD process for lithium borate has been reported by Kazyak et al. [5], which resulted in films with significant carbon incorporation. In this work, we have developed an ALD process for depositing lithium borate with minimal contaminants (< 5 at.% as determined by XPS) using LiHMDS, H2O and TMB as precursors. Through-plane impedance spectroscopy measurements were used to determine the ionic conductivity. For a lithium borate ALD film with a thickness of 81 nm deposited at 250°C, an ionic conductivity of 1.60 ± 0.03 x 10-7 S cm-1 was obtained at 30 °C, with an activation energy of 0.58 ± 0.01 eV.By combining this lithium borate ALD process with the well-known lithium phosphate ALD process [6], the composition of the film could be precisely controlled, resulting in tailored electrochemical properties. Cyclic voltammetry was employed to evaluate the electrochemical stability of the lithium borophosphate mixtures. The coatings were deposited on top of an ion-blocking material and cycled to high voltages. Initial results indicate that the stability of the coating material decreases as the amount of lithium borate to lithium phosphate cycles increases.These promising preliminary results demonstrate that ALD is a valuable tool in developing high-performance battery technologies, enabling the deposition of new protective coatings with controllable electrochemical properties. Finding the optimal lithium borophosphate coating will require a trade-off between ionic conductivity and electrochemical stability and will ultimately depend on the intended application. References Jung, Y. S., J. Electrochem. Soc. 157, A75 (2009).Henderick, L., Appl. Phys. Rev. 9, 011310 (2022).Put, B., J. Electrochem. Soc. 166, A1239 (2019).Magistris, A., J. Power Sources 14, 87 (1985).Kazyak, E., J. Mater. Chem. A 6, 19425 (2018).Hämäläinen, J., J. Electrochem. Soc. 159, A259 (2012). Figure 1

Constructing Stable Solid Electrolyte Interphase Using Gel Polymer Electrolytes for Anode-Free Lithium Metal Batteries with Enhanced Cycle Life

Anode-free lithium metal batteries (AFLMBs) have recently emerged as next-generation batteries due to high energy density, reduced cost, and simplified manufacturing process due to the absence of reactive metallic lithium. However, developing high-performance AFLMBs faces several challenges for practical applications, such as low coulombic efficiency and poor cyclability, due to the dendrite growth of lithium and side reactions of lithium with liquid electrolytes. To develop the AFLMBs with long cycle life, it is necessary to attain high coulombic efficiency since there is no excessive lithium to compensate for irreversible Li inventory losses in the AFLMB. Three-dimensional cross-linked gel polymer electrolyte (GPE) can be a good candidate for stabilizing the lithium metal by encapsulating organic solvents in the polymer matrix, leading to reduction of the parasitic reactions between lithium metal and liquid electrolyte, which results in high coulombic efficiency of AFLMBs. In this work, we prepared a cross-linked GPE using a multi-functional cross-linking agent to realize high coulombic efficiency and long cycle life of AFLMBs with LiNixCoyAl1-x-yO2(NCA) cathode (areal capacity of 4.76 mAh cm-2). Moreover, the GPE capable of coordinating with lithium ions could construct stable solid electrolyte interphase by regulating lithium ion solvation structures. Cycling performance was investigated in the voltage range of 3.6 – 4.3 V at 0.5 C rate. The Cu/GPE/NCA cell exhibited a capacity retention of 80% after 150 cycles, which was higher than that of AFLMB with liquid electrolyte. Electrochemical characterization and spectrometry were performed to investigate how the GPE could improve the cycling performance of AFLMBs.

Estimation of State-of-Charge and Energy Efficiency of Supercapacitors Using a 1-D Electrochemical Model

Supercapacitors (SCs) have found a broad application spectrum due to their unique characteristics, including high power density and long cycle life [1]. Supercapacitors have been extensively studied to be used with Li-ion batteries for electric vehicle applications due to their complementary characteristics [1]. The energy management system of these applications relies on accurate information about the state-of-charge (SOC) and energy efficiency of the storage device at the cell level for effective monitoring and control. In the case of SCs, coulomb counting is the most commonly used SOC identification method; however, it entails certain challenges, including initial SOC information, effects of leakage current, and measurement noise [1]. Alongside improving the capacitive health diagnosis, it is critical to identify utilizable capacitance. During rapid charge/discharge of an SC, the ions in the electrolyte are immediately adsorbed/desorbed within the macro-pores, which leads to achieving the desired terminal voltage level instantaneously. However, this hinders ions’ penetration in the micropores, causing an inhomogeneous distribution of the ions across the electrodes, increasing the electrolyte resistance, resulting in poor utilizable capacitance and a drop in its energy efficiency [2]. Derived from a one-dimensional model [2, 3], a simplified SOC and energy efficiency estimation scheme of the SCs is proposed in this study. In the solid phases, the charge density of the SC is approximated as a function of its electrodes’ specific surface area, double-layer differential capacitance, and the potential drop across the double-layer. The SOC of the SCs can be expressed as a function of the solid phase charge density in the positive electrode or negative electrode, as defined in Eqn. (1). The energy efficiency (Eeff ) of the SCs can be expressed as a function of the ratio of bulk double-layer potential difference of the electrodes to the output terminal voltage change, as defined in Eqn. (2). SOC(t)=(ρ(t)/ρmax)×100 ...............(1); Eeff=(ΔΦ/ΔΦd/ΔV)×CrΔV2/2 ..............(2) where ρ and ρmax are the electrode charge density at t time and a fully charged state, respectively; ΔΦd is the bulk double-layer potential difference; ΔV is the terminal voltage change; and Cr is the rated capacitance.The electrochemical model is used to analyze the effectiveness of the proposed SOC and energy efficiency model considering a galvanostatic charge and discharge. In this limited scope, a concise response of the model compared to their respective standard methods is shown in Fig. 1. A SAFT 3500 F SC cell parameters are considered to perform the simulations [2, 3]. The results show that the SOC estimation scheme identifies the remaining charge without considering the initial SOC information. Similarly, the energy efficiency model calculates the energy received/delivered by the SC effectively. Figure 1

Nanostructured 3D Mesoporous α-Fe2O3 Nano-Cubes As a High-Performance Electrode for Supercapacitors

Development of energy storage devices of high energy density and long cycle life is one of the pressing needs of electronic devices. Pseudo-capacitors with iron oxide electrodes show promising energy storage devices because they are economical and safe, but have poor conductivity and stability. To achieve an improved electrochemical performance such as shorter ion-diffusion path, faster ion accessibility, and higher conductivity, a rationally design of electrode material is highly desirable. Here, we shed the light on how three-dimensional (3D) Nano porous networked α-Fe2O3 nano-cubes serves as a supercapacitor electrode. Here we show the high specific capacitance and long-life supercapacitor anode by developing a hierarchical three-dimensional α-Fe2O3 nano-cubes. KOH is used as an aqueous electrolyte. The synthesized annealed nano-cubes (PNC) have high surface areas of 5.127m2/g. The annealed Hematite (α-Fe2O3) NC show good thermodynamic stability with high reversible redox activity. The half-cell anode based on this nanostructure give rise to a high specific capacitance value of ~520F/g at a current density of 1 A/g and ~90% of the capacitance can be retained at 2 A/g after 1000 redox cycles (indicates the good cyclic stability). The present work demonstrates that binder and conductive additive-free 3D Nano porous electrodes open up a new avenue to fabricate high surface area electrodes for improved charge storage performance. These performance features are superior among those reported for iron oxide-based supercapacitors. High specific capacitance value, stable cycling, and facile preparation make Hematite NC(α-Fe2O3) an excellent material for use as supercapacitor electrodes.

Innovative Investigation of Ordered Mesoporous Carbon Modified Separator for High Performance Lithium-Sulfur Batteries

These days, many portable electronic devices are used widely, and it makes secondary batteries important for future innovation. Li-ion battery which is most commonly used has the high specific energy and long cycle life. But it has problems with high price and possibility of explosion. Also it reaches the limitations of energy density for electric vehicles (EVs) and energy storage systems (ESS). Lithium-Sulfur battery is becoming a one of the promising alternatives. It has high theoretical capacity (1,675 mAh g-1) and specific energy density (~2600 Wh kg-1) and low cost. Also it is eco-friendly and safe. However, there is the primary problem to be commercialized. That one is called shuttle effect, which means dissolution of polysulfide into the electrolyte in the repetitive charging and discharging. It makes capacity decrease and internal resistance increase. And the active material and the discharge products, which are sulfur and Li2S2, Li2S, have low conductivity. The irreversible volume expansion during electrochemical reaction reaches to 80%. [1,2] To alleviate these problems, various sulfur host materials and modified separators have been investigated. [3,4] One of the representative approach is to apply carbon materials as sulfur hosts. Sulfur must be dispersed throughout the carbon conductor because of its low intrinsic electrical conductivity. The carbon matrix functions as a network for rapid electron transport. Various carbon materials, such as porous carbons, carbon nanotubes, or carbon materials with heteroatoms or chemical groups such as N, O, and S, have been employed to minimize polysulfide migration. One of the most effective sulfur hosts for limiting polysulfide diffusion is mesoporous carbon. By virtue of their inherent porosity and conductive carbon architecture, mesoporous carbon hosts have demonstrated better cycling performance. Another method for dealing with the shuttle effect is to form an interlayer between the cathode and the separator. Because the separator is an important role in battery safety and electrochemical performance, designing a high quality separator is critical for the development of high performance Li-S batteries. Separators made of polypropylene (PP) or polyethylene (PE) are commercially used and have some physical and electrochemical advantages. However, these separators have drawbacks such as low ionic conductivity and poor electrolyte compatibility. Various materials have been studied and used for modifying materials on the separator. For example, carbon materials, graphene oxides, and metal-organic frameworks are excellent at suppressing the shuttle effect of polysulfide. On the other hand, characterizing these structures and comprehending polysulfide behavior in these systems during electrochemical reaction, remain substantial challenges. Herein, we report on a dual-functional modified separator by applying ordered mesoporous carbon (OMC) on a commercial separator.The mesopores and the micropores of the OMC own a specific physical adsorption capability for polysulfide, thus it can adsorb a large amount of polysulfide. In addition, it is thermally and chemically stable. Also, the OMC can be detected by operando small-angle scattering (SAXS). In recent years, SAXS approach was applied to explain the ordered porous structure of sulfur host materials for Li-S batteries. These research provide information on how sulfur is adsorbed by porous carbon. This analysis identifies the changes of sulfur species as to whether polysulfide is adsorbed in mesopores or solid discharge products are formed on the surface, or infiltrated into micropores. The use of in-depth characterization techniques allows for more precise and independent assessment of the rapid electrochemical reactions in Li-S batteries. In brief, the highly ordered mesoporous carbon was synthesized, and it was used as an interlayer that served not only as a physical barrier to limit the polysulfide shuttle phenomena but also as an additional current collector to reuse active materials. By promoting the electrochemical reaction of active materials, it exhibited better electrochemical performance such as high capacity, stable cycle performance, and improved rate performance. The adsorbed polysufide and the behavior of sulfur species in the OMC during cycling were investigated using operando SAXS to acquire insight into the role of the OMC modified separator.[1] Li, Z.; He, Q.; Xu, X.; Zhao, Y.; Liu, X.; Zhou, C.; Ai, D.; Xia, L.; Mai, L. Adv. Mater. 2018, 30 (45), 1804089.[2] Zeng, L.-C.; Li, W.-H.; Jiang, Y.; Yu, Y. Rare Met. 2017, 36 (5), 339-364.[3] Liu, Z.; Liu, B.; Guo, P.; Shang, X.; Lv, M.; Liu, D.; He, D. Electrochim. Acta 2018, 269, 180-187.[4] Schuster, J.; He, G.; Mandlmeier, B.; Yim, T.; Lee, K. T.; Bein, T.; Nazar, L. F. Angew. Chem. 2012, 124 (15), 3651-3655. Figure 1

Sustainable SiO2 Nanostructures from Different Diatom Species As Anode Material for Future Generation Lithium-Ion Batteries

Energy harvesting and storage devices occupy a more prominent place in the 21st century than at any time in the past. Intensive efforts have been devoted to next-generation energy storage devices such as rechargeable lithium-ion batteries (LIBs) to develop high energy density and long cycle life electrode materials from sustainable sources. In the present anode, graphite is severely restricted by capacity and unavoidable solid electrolyte interface (SEI) formation. Besides, it has been listed as a critical material by the European Commission. Recently, silicon-based electrodes have been pinpointed as promising anode candidates due to their high theoretical capacity (~4200 mAhg-1 for Li4.4Si), low operating voltage (0.4V/Li/Li+), abundant resources, and environmental friendliness. Interestingly, nanostructures of Silica (SiO2) can be extracted from the frustules (exoskeletons) of a type of microalgae called diatoms. In this current work, SiO2 frustules were grown from two different diatom species, constituting a sustainable source for producing nanostructured Si-based materials. Scanning electron microscopy (SEM) images confirmed the highly nanoporous structure of diatom silica, which was retained even after ball-milling. The electrochemical performance of SiO2 was investigated as an anode material for LIBs. Herein, we have tested both species A & B milled and un-milled samples (denoted as SPAUM, SPAM, SPBUM, and SPBM). The diatom SiO2 un-milled species A (SPAUM) exhibited a high specific capacity of ~ 810 mAhg-1 with remarkable capacity retention and coulombic efficiency even after 100 cycles at 0.1 Ag-1 and delivered a high specific capacity of ~ 400 mAhg-1 even at high current density 3 Ag-1. For comparison and understanding, commercially available diatomaceous earth milled, and un-milled silica (denoted as EDAM & EDAUM) has been subjected to the same cycling protocol. Results clearly showed species A & B milled and un-milled displaying better electrochemical performance than diatomaceous earth milled and un-milled silica. Such improved electrochemical properties like cycle life, and rate capability of SPAUM are mainly ascribed to their highly porous nature which significantly facilitates fast Li ion diffusion, its unique morphology, which favors a faster kinetics and its complete lithiation/de-lithiation after the initial activation cycle. In view of the superior electrochemical properties, such sustainably sourced SiO2 materials can be considered a potential anode material for future LIBs. Figure 1

Multi-Parameter Optimization of Siloxene-PANI Composites for High-Performance and Flexible Energy Storage Application

The development of high-performance energy storage devices is crucial for various applications, such as electric vehicles, portable electronics, and renewable energy systems. Supercapacitors have emerged as a promising technology due to their high power density and long cycle life. However, their low energy density has limited their widespread application. To address this limitation, researchers have been exploring various strategies, including the use of new electrode materials and optimized electrode design. In this study, a high-energy-density energy storage device was developed using a composite material composed of siloxene and polyaniline (PANI) for flexible supercapacitor designs. Here, optimized material's surface area, pore distribution, and electronic transition, achieving a specific capacitance of 483 F/g at 1A/g in a three-electrode system using a 1 M H2SO4 electrolyte. The optimized material also exhibited a retention rate of 92.6% at 5A/g. The optimized siloxene-PANI composite material was then used to fabricate a flexible asymmetrical supercapacitor (SiP4//AC). The supercapacitor exhibited a high energy density of 19.7 Wh/kg at a power density of 248 W/kg, with a cyclic stability of 90.26% and a coulombic efficiency of 97%. The flexible design of the supercapacitor using the siloxene-PANI composite material allowed for its use in wearable electronics and other applications requiring high-performance, flexible energy storage devices. The study provides valuable insights into the development of energy storage devices with high energy density and high power density, which will pave the way for the practical application of supercapacitors in various fields.

Chemical and Electrochemical Interaction of Halide and Sulfide-Based Electrolytes in Solid-State Batteries

Introduction Conventional lithium-ion batteries (LIBs) have found widespread small and large applications. However, safety issues and capacity degradation of the cells, in general, can occur due to the use of toxic and flammable liquid electrolytes [1]. As one of the next-generation LIBs, solid-state lithium batteries (SSBs) have the potential to replace liquid electrolyte LIBs due to their safety and potentially high energy density [2]. The key component of SSBs is the solid-state electrolyte (SSE). Sulfide and halide-based solid electrolytes are among the hot topics in solid electrolyte research for SSBs. Despite the advantages of solid electrolytes, such as good compatibility with high-voltage cathode materials and soft fabrication. However, the poor chemical and electrochemical stability of sulfide and halide-based solid electrolytes towards Li metal has a critical problem that causes the degradation of the lithium/solid electrolyte interface due to the formation of side reaction components that leads to inhibiting lithium kinetics [3]. Results and Discussion Here, we have shown that a combination of halide and argyrodite (Li6PS5Cl) solid electrolytes can lead to the prevention of the formation of unfavorable interactions between solid electrolytes and lithium metal anode. The combination of halide and argyrodite (Li6PS5Cl) in the Li/Li symmetric cell can stabilize cycle life and increase the high critical current density (CCD) from C/20 to C/2 in comparison with the pure halide and argyrodite electrolytes. Furthermore, compared to the original halide and argyrodite electrolytes, a high initial coulombic efficiency and cycle life can be maintained when combined with a full Li/NCM cell. This approach to improving halide-based SSBs can provide a fairly simple and efficient strategy. Acknowledgements This project has received funding from the European Union's Horizon Europe programme for research and innovation under grant agreement No. 101069681 (HELENA project).

Inkjet Printed Ti3C2 Electrodes for Anode-Free Zinc-Ion Battery

Additive manufacturing techniques are coming to the fore in many technological fields as cheaper and more versatile manufacturing routes alternative to the physical deposition methods. In particular, when miniaturized, thin-film or patterned structures are needed, Inkjet printing (IJP) has been widely demonstrated as suitable techniques to fabricate coated electrodes and microdevices for many applications including energy storage 1. In this regard, Zinc-ion batteries (ZIBs) are a promising alternative to the traditional lithium-ion batteries due to the abundance and low cost of zinc. In ZIBs, a metallic Zn chips is usually employed as the anode and a variety of materials, such as metal oxides or polymers, as the cathode. Zinc-ion batteries have the potential for high energy density and long cycle life, however they suffer of the well-known issue of Zn dendritic growth and poor efficiency of the plating-dissolution process 2. Ti3C2 MXene have been recently demonstrated as a high-performance “zincophilic” substrate for smooth and efficient zinc with high reversibility 3,4.In this work, we investigate inkjet-printed Ti3C2 MXene thin coatings as an ideal substrate for anode-free ZIBs. Stable aqueous Ti3C2 MXene inks were formulated and successfully inkjet printed on different substrates. The zinc metal nucleation phenomena on MXene 2D sheets were investigated by electrochemical potentiodynamic polarization techniques as well as galvanostatic ones, comparing them to a zinc metallic foil. Ex-situ electron scanning microscopy (SEM) analyses were employed to observe the plated Zn morphology after cycling at both low and high current density. Taking advantage of the smooth inkjet-printed Ti3C2 MXene coatings, electrochemical atomic force microscopy (EC-AFM) was used for the first time to perform in-operando investigation of the Zn plating process, allowing to reveal the early stage Zn plating mechanism on the as-printed Bibliography C. Li, F. Bu, Q. Wang, and X. Liu, Advanced Materials Interfaces, 9, 2201051 (2022).K. Wang, ACS Omega, 5, 10225–10227 (2020).J. M. Park et al., Journal of Energy Chemistry, 76, 187–194 (2023).Z. Gong et al., Journal of Colloid and Interface Science, 625, 700–710 (2022).

Development of Iron Fluoride Based Nanocomposite Materials to Enable High Performance Aluminium-Ion Batteries

Developing grid-scale energy storage is important for the penetration of intermittent renewable energies such as wind and solar, but remains one of the biggest challenges in the field of electrochemical energy storage [1]. The application of mature lithium-ion batteries (LIBs) to grid energy storage is controversial due to the limited Li resources and geographical distribution, high cost of materials (e.g., Co, Li), limited lifetime, and safety concerns [2]. Rechargeable aluminium ion batteries (AIBs), which normally utilises aluminium (Al) metal as anode, are one of the most promising battery technologies for future large-scale energy storage, due to the high theoretical volumetric capacity (8046 mAh cm−3), high safety, and low cost and high abundance of aluminium (the third most abundant metal in the earth crust) [3].AIBs have achieved long cycle life (>7500 cycles) when using graphite and graphene as cathode materials [4-5]. Nevertheless, the reported graphite-based cathodes have intrinsically low storage capacities (60–200 mAh g-1) due to the intercalation mechanism of the solvated ions rather than the multivalent Al3+ transformation. Extensive efforts have been made to develop new cathode materials to promote the specific/volumetric capacity of AIBs, including transition metal oxides [6], sulfides [7], selenides [8] and others. These AIBs based on non-graphite cathodes usually demonstrate either low discharge voltage, or high initial capacity but significant capacity decay and poor cycle life. To further improve the performance of AIBs, new cathode materials with high storage capacity and long cycle life needs to be developed.In this paper, we report the development of a nanoscale FeF3@expaned graphite (EG) composite as a novel conversion-type cathode material for AIBs [9]. AIB coin cells were assembled using high-purity Al foil as the anode, the ionic liquid [EMIm]Cl/AlCl3 as the electrolyte, and the FeF3@EG composite as cathode. The conversion reaction between the Al3+ ions and FeF3 through transferring three electrons for per Al3+ ion reacted could boost the storage capacity of AIBs. A single-wall carbon nanotube-modified separator was introduced into the system, to significantly restrict the shuttle effect of the intermediate product of FeF3. The assembled AIBs exhibited a satisfactory reversible specific capacity of 266 mAh g-1 at a current density of 60 mA g-1 after 200 cycles, and a good Coulombic efficiency approaching 100% after 400 cycles at a current density of 100 mA g-1 [9]. Ex-situ X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) have been applied to explore the energy storage mechanism of FeF3 in AIBs for the first time [9].To further overcome the corrosion issue of ionic liquid, a gel polymer electrolyte (GPE) has been successfully synthesised via an innovative method where no solvent or initiator was utilised in the polymerisation process. The application of GPE significantly reduced the corrosivity and enhances the moisture sensitivity of EMIC ionic liquid, as well as improving the reversible ability of the AIBs. The FeF3@EG-based AIB with 0.8g-EMIC-gel electrolyte exhibits a reversible capacity of 204.5 mAh g-1after 1000 cycles at a current density of 100 mA g-1 and stable rate performance for 600 cycles with a Coulombic efficiency of approximately 95%.This work provides unprecedented insight into novel conversion type cathode materials for AIBs. The findings in this work can serve as guidance for the successful design of low cost and high discharge capacity AIBs for large-scale energy storage and are also meaningful for the fundamental understanding of the metal fluorides cathodes for AIBs.

Poor Cycling Performance of Rechargeable Lithium–Oxygen Batteries Under Lean-Electrolyte and High-Areal-Capacity Conditions: Role of Carbon Electrode Decomposition

There has been considerable interest in developing rechargeable lithium oxygen batteries (LOBs) that have the potential to significantly exceed the energy density limit of a Li ion battery (approximately 300 Wh/kg). Although 500 Wh/kg LOB has been demonstrated and exhibited stable discharge/charge cycle at room temperature condition1, their cyclability remains less than 10 cycle. For realizing the LOB with practically high energy density and long cycle life, the deep understanding of complicated reaction in LOBs has been highly demanded. Especially, the problems specifically associated with the limited electrolyte (“lean-electrolyte”) conditions need to be taken into account in LOBs.Although the importance of investigating negative lithium electrodes in lean-electrolyte systems has been recognised in recent years2,3, specific problems associated with the negative lithium electrode in a LOB has not been investigated so far. In particular, chemical crossover from the positive electrode to the negative electrode is a crucial factor that needs to be taken into consideration. Actually, recent studies have shown that LiOH is formed on the surface of a lithium-metal electrode through reaction with H2O in the electrolyte4,5. This H2O is generated by the decomposition of the tetraethylene glycol dimethyl ether (TEGDME) solvent at the positive oxygen electrode, which then migrates to the negative electrode side to react with the lithium-metal electrode. Consequently, problems related to chemical crossover are prominent in lean-electrolyte LOBs, where the effective water concentration in the electrolyte is much higher than that in an excess electrolyte system.Despite the importance of investigating the reaction of negative lithium electrodes in LOB with appropriate technological parameters, mechanistic details remains unclear due to the technical difficulty for applying non-destructive analytical methods. In the present study, we investigated the reaction of a negative lithium electrode in a lean-electrolyte LOB operating under high areal capacity conditions. The use of advanced non-destructive analytical methods, including three-electrode electrochemical techniques and an in-situ analytical setup revealed that the reaction efficiency of the lithium electrode mostly decreases through chemical crossover from the positive oxygen electrode6. In particular, the H2O generated as a side-product at the positive oxygen electrode crosses over to the negative electrode side and reacts with the lithium-metal electrode to form a porous LiOH/Li2CO3 layer on the electrode surface. LiOH and Li2CO3 accumulates, and the porous layer thickens through repeated discharge/charge cycling, which supresses efficient Li-ion transport through the layer.Furthermore, using a solid-state ceramic-based separator to protect the lithium-metal negative electrode, the side reaction with the negative electrode was considerably suppressed, which helped exclusively assess the degradation phenomena occurring in the oxygen positive electrode. By series of in-situ and ex-situ analysis revealed the following points: (i) Although the electrolyte degradation intensified with increasing repeated discharge/charge cycling, the scarcity of the electrolyte minimally influenced the cycle life of the LOBs. (ii) Most of the Li2CO3-like solid-state side products decomposed during charging at voltages higher than 3.8 V. (iii) Severe decomposition of the carbon electrode occurred during cycling, and an equivalent amount of CO2 was generated during charging at voltages higher than 3.8 V. Because the carbon electrode used in these experiments merely decomposed via simple electrochemical oxidation at voltages up to 4.5 V, the carbon electrode was considered to deteriorate through the decomposition of its solid-state side products. The findings of this study are anticipated to guide future investigations on the advancement of LOBs. In particular, detailed understanding of the reaction at the interface between the carbon electrode and solid-state products is crucial for realizing practical high-energy-density LOBs with long cycle life.

Lithium-Ion Capacitor Characterization Using Optical Fiber Sensors

With the high power density and long cycle life, lithium-ion capacitors (LICs) are anticipated to fill the performance gap with lithium-ion batteries. As LICs generally has one battery-type electrode with slow kinetics, and one capacitor-type electrode with fast kinetics, the bulk concentration of lithium ions is believed to change significantly. To capture the rapidly changing concentration and analyzing it with regards to the charge and discharge rates will reveal important information about the system.The lithium-ion concentration is measured with an in-house built fiber-optic sensor setup, see Fig. 1. The fiber is placed between the electrodes (Fig. 1a) and the concentration-dependent reflectivity is measured (Fig. 1b). Calibration of the sensor using known concentrations enables the calculation of the electrolyte concentration with rapid acquisition and high accuracy (Fig. 1c). Figure 1

Revealing the Cycling and Degradation Mechanism of Bi-Metallates As Anode Materials for Na-Ion Batteries

Na-ion batteries (NIBs) represent an emerging alternative to modern Li-ion batteries. To improve the overall performance of NIBs it is crucial to develop new types of anode materials with high capacity and long cycle life. Among the anode candidates, materials operating under combined conversion and alloying mechanisms (CAMs) are considered as promising. They are capable of delivering high capacity, however, despite theoretical predictions the cycling stability is still below expectations. Therefore, a comprehensive understanding of the cycling and degradation mechanisms of CAMs is crucial to improve their performance. However, these materials undergo multiple chemical transformations, which often involves formation of amorphous and nanocrystalline phases during cycling. Such chemical complexity substantially impedes their full characterization and understanding.Bismuth metallates, with a general formula of Bi-TM-O (TM = transition metal), is a group of ternary CAMs. Their general cycling mechanism consists of an irreversible conversion reaction, which leads to formation of Bi nanoparticles embedded in a Na-TM-O matrix during the first sodiation. This is followed by a reversible two-step alloying reaction leading to formation of Na3Bi with NaBi as an intermediate phase. In this work, we have used operando X-ray diffraction over the course of ∼30 cycles to study the cycling and degradation mechanisms of two CAMs - Bi2MoO6 and BiFeO3. With the help of ex situ X-ray absorption spectroscopy and pair distribution function (PDF) analysis, we have revealed new insights into these materials in addition to confirming the general cycling mechanism.Both materials form the cubic phase of Na3Bi (c-Na3Bi) in the sodiated state with some noticeable differences. While, the hexagonal Na3Bi (h-Na3Bi) phase starts to form after 10 cycles in Bi2MoO6, a combination of c-Na3Bi and h-Na3Bi can be observed after the first cycle in BiFeO3. The formation of c-Na3Bi is kinetically favorable in these systems, while h-Na3Bi is the more thermodynamically stable and, therefore, forms later in the cycling process. Both materials shows three distinct regions of capacity degradation, where the first is initiated by a growth in the crystallite sizes of Bi-particles. This is followed by a disappearance of the Bi-phase as the second step. The last degradation phase is related to the disappearance of the NaBi-phase and locking the system in the sodiated state. The present talk will discuss the mechanisms of these degradation steps in view of the future development of CAMs in greater details. Figure 1

Facile morphological construction of VO2 and its application in aqueous Zn-ion batteries

Three distinct morphologies of VO2, namely flake-shaped VO2 (VO2(PIAN)), disc-shaped VO2 (VO2(BING)) and rod-shaped VO2 (VO2(BANG)) were synthesized using a facile one-pot hydrothermal method. As a cathode for aqueous zinc-ion batteries (AZIBs), the VO2(PIAN) demonstrates relatively superior electrochemical performance for aqueous zinc storage, including the high discharge specific capacity and long cycle life. After 500 cycles at a current density of 1000 mA/g, it retains a discharge capacity of 208.83 mA h/g, with a Coulombic efficiency nearing 100%, which can be attributed to the larger specific surface area and shortened Zn[Formula: see text]diffusion distance, promoting faster electric transfer and Zn[Formula: see text]diffusion kinetics. This work broadens the understanding of the electrochemical behavior of VO2-based AZIBs.

Aqueous aluminum-zinc hybrid ion batteries with urea-based hydrated eutectic electrolytes

Aqueous polyvalent ion batteries are more suitable for large-scale industrial applications than non-aqueous polyvalent ion batteries due to their intrinsic cost-effectiveness and eco-friendliness. Developing new electrolyte and finding compatible anode and cathode materials are key to improve battery performance and reversibility. Herein, we present a novel aluminum-urea hydrated eutectic electrolyte (AUHEE) by coupling Al2(SO4)3·18 H2O and urea. Urea-assisted hydrated aluminum ions weaken the strong interaction between aluminum ions and water molecules, thus inhibiting hydrogen precipitation and anode passivation by suppressing water dehydrogenation. Unique solvation structure of electrolyte enables the V2O5/AUHEE/Zn cell to exhibit high discharge capacity (250 mAh g−1) and long cycle life (1500 cycles), providing new insights into the development of aqueous polyvalent ion batteries with high performance.

Excellent performance of pH sensitive artificial muscles under large loading

The pH-responsive artificial muscle is a chemical-driven actuator without external power input. However, the low work density and adequate stability limit their practical applications. Herein, we combine the porous pH-responsive polymer with carbon fiber bundles for obtaining the coiled hybrid fiber. The coiled carbon fiber (CNF) yarn enhances the strength of hybrid fiber, and the swelling pH sensitive polymer limited to CNF provide a large stroke for hybrid fiber untwisting, resulting in an excellent work capacity and a high cycle life. When the load weight is 600 times the weight of the fiber itself, its work density reaches 287 kJ/m3. In addition, the hybrid fiber can reach a maximum stretching and contraction of 47% at a load of 400 times its own weight. The breaking stress of the obtained artificial muscle can reach more than 100 MPa. At the same time, the constructed porous polymer hydrogels improve the response rate of the artificial muscle, the response time is shortened to 10 min and do not decay in hundreds of cycles, which is further shown that the limiting effect of carbon fiber on the polymer improve the stability of the artificial muscle. It is indicated that the pH-responsive composite fibers have a high potential for use in artificial muscles, pH sensors and mechanical system.

High-Performance Supercapacitors Using Hierarchical And Sulfur-Doped Trimetallic NiCo/NiMn Layered Double Hydroxides.

A supercapacitor features high power density and long cycling life. However, its energy density is low. To ensemble a supercapacitor with high power- and energy-densities, the applied capacitor electrodes play the key roles. Herein, a high-performance capacitive electrode is designed and grown on a flexible carbon cloth (CC) substrate via a hydrothermal reaction and a subsequent ion exchange sulfuration process. It has a 3D heterostructure, consisting of sulfur-doped NiMn-layered double hydroxide (LDH) nanosheets (NMLS) and sulfur-doped NiCo-LDH nanowires (NCLS). The electrode with sheet-shaped NMLS and wire-shaped NCLS on their top (NMLS@NCLS/CC) increases the available surface area, providing more pseudocapacitive sites. It exhibits a gravimetric capacity of 555.2 C g-1 at a current density of 1 A g-1 , the retention rate of 75.1% when the current density reaches up to 20 A g-1 , as well as superior cyclic stability. The assembled asymmetric supercapacitor that is composed of a NMLS@NCLS/CC positive electrode and a sulfurized activated carbon negative electrode presents a maximum energy density of 24.2Wh kg-1 and a maximum power density of 16000W kg-1 . In this study, a facile strategy for designing hierarchical LDH materials is demonstrated as well as their applications in advanced energy storage systems.

Phosphorous-Based Heterostructure for the Effective Catalysis of Polysulfide Reactions with Phase Changes in High-Sulfur-Loading Lithium-Sulfur Batteries.

High sulfur loading and long cycle life are the design targets of commercializable lithium-sulfur (Li-S) batteries. The sulfur electrochemical reactions from Li2 S4 to Li2 S, which account for 75% of the battery's theoretical capacity, involve liquid-to-solid and solid-to-solid phase changes in all Li-S battery electrolytes in use today. These are kinetically hindered processes that are exacerbated by a high sulfur loading. In this study, it is observed that an in situ grown bimetallic phosphide/black phosphorus (NiCoP/BP) heterostructure can effectively catalyze the Li2 S4 to Li2 S reactions to increase the sulfur utilization at high sulfur loadings. The NiCoP/BP heterostructure is a good polysulfide adsorber, and the electric field prevailing at the Mott-Schottky junction of the heterostructure can facilitate charge transfer in the Li2 S4 to Li2 S2 liquid-to-solid reaction and Li+ diffusion in the Li2 S2 to Li2 S solid-state reaction. Consequently, a sulfur cathode with the NiCoP/BP catalyst can deliver a specific capacity of 830 mAh g-1 at the sulfur loading of 6mg cm-2 for 500 cycles at the 0.5 C rate. High sulfur utilization is also possible at a higher sulfur loading of 8mg cm-2 for 440 cycles at the 1 C rate.

Application of Nondestructive Testing Technology in Device‐Scale for Lithium‐Ion Batteries

Lithium‐ion batteries (LIBs), due to their high energy density and long cycling life have been widely applied in a variety of industries, including electric vehicles, small‐ and medium‐sized electronic devices, and intelligent medical care. Nevertheless, the security and real‐time state of LIBs is difficult to obtain accurately, improving the battery's service life and ensuring battery safety have become the focus of research. Nondestructive testing (NDT) technology has developed quickly to reach this purpose, requiring a thorough investigation of how batteries’ internal structures have evolved. The principles, contributing factors, and applications of various widely used NDT techniques are summarized and discussed in this review. These inspection techniques can be used to evaluate the battery condition, observe the internal structure of the battery, analyze the failure phenomenon and electrochemical performance of the battery operation, etc. Finally, a summary and outlook are given regarding the characteristics and prospects of NDT methods. This overview will show new light on the application of NDT technology for LIBs and will promote the development of next‐generation LIBs with high security.