Theoretical Gravimetric Capacity Research Articles

Enhance hydrogen storage in lightweight solid-state systems based on Poly(vinylnaphthalene)

This article highlights the potential of poly(2-vinylnaphthalene) (PVN) as a novel light-weight solid-state hydrogen storage system for various applications. With an impressive theoretical gravimetric hydrogen capacity of 5.2 wt.-%, PVN stands out for its attractiveness as a hydrogen carrier. The material possesses advantageous characteristics, including moldability, low toxicity, and ease of storage, making it a promising candidate for both stationary and mobile hydrogen storage applications. Experimental findings demonstrate that PVN can be hydrogenated by up to 76 % utilizing an Ru/Al2O3 catalyst at 250 °C for 24 h. Confirmation of the hydrogenation reaction, which results in poly(2-vinyldecalin), was achieved through characterization techniques such as FTIR, 1H NMR, and spectroscopic ellipsometry. The study of the effects of hydrogen pressure and reaction time identified moderate conditions as favorable, though a further exploration of different catalysts is suggested for optimal conversion. A palladium-based catalyst was employed to release hydrogen from the hydrogenated polymer, demonstrating almost complete reversibility of the hydrogenation of poly(2-vinylnaphthalene) with a dehydrogenation yield of 90 %.

A novel modeling approach for sulfurized polyacrylonitrile (SPAN) electrodes in Li metal batteries

Li-sulfur batteries represent a promising class of next-generation batteries with high theoretical gravimetric capacity. Moreover, the absence of scarce elements such as nickel or cobalt makes them a sustainable alternative to Li-ion batteries. However, it is well known that the main problem of Li-sulfur batteries is the so-called polysulfide shuttle, which leads to self-discharge, capacity fading and low coulombic efficiency. In recent years, several mitigation strategies have been developed for Li-sulfur batteries to reduce the polysulfide shuttle effect. One promising approach is to covalently bond the sulfur to a polymer backbone. A well-known class of materials is sulfurized poly(acrylonitrile) (SPAN), for which long cycle life and high specific capacities have been reported. In this work, we present a novel continuum model for SPAN electrodes and demonstrate its application in Li-SPAN batteries. Within our simulation framework we include both red/ox reactions of covalently sulfur on PAN as well as transport and reactions of polysulfides in the solution. By combining simulations and experimental data we analyze the discharge mechanism and provide guidelines for electrode design.

Silicon Solid State Battery: The Solid‐State Compatibility, Particle Size, and Carbon Compositing for High Energy Density

AbstractSolid‐state battery research has gained significant attention due to their inherent safety and high energy density. Silicon anodes have been promoted for their advantageous characteristics, including high volumetric capacity, low lithiation potential, high theoretical and specific gravimetric capacity, and the absence of lethal dendritic growth. Addressing concerns such as low conductivity, pulverization, fracture, dense solid electrolyte interface layer, and low coulombic efficiency has substantially improved the use of silicon electrodes in solid‐state batteries. Researchers have explored carbon additions, solid electrolyte suitability for Si anodes, pressure optimization, and particle size effects (nano/micro) to enhance energy density. Recent studies have investigated the conductivity mechanism, stack pressure, and anode‐solid electrolyte compatibility to improve energy density. Micro‐ and nano‐sized silicon have attracted attention in carbon‐based composites due to their exceptional conductivity, uniform distribution, efficient electron migration, and diffusion channels. The development of solid‐state batteries with high energy density, safety, and extended lifespan has been a major focus. This review sheds light on significant insights and strategic approaches for researchers working on solid‐state silicon‐based systems to overcome existing challenges.

Electrode-Resolved Impedance and Potential Measurements to Investigate the Rate Capability of High Loading Micron-Silicon Anodes in All-Solid-State Batteries

In order to enable the market introduction of all-solid-state batteries (ASSBs), several anode concepts are under investigation to increase the energy density compared to graphite anodes, while maintaining long cycle-life. At the same time, the production costs must be the same or even reduced in comparison with classical lithium-ion batteries. Besides lithium metal as anode material, which still poses significant technical challenges, more and more interest is being directed toward materials that form lithium alloys. One of the most attractive candidates is silicon, which has a low delithiation potential of around 0.45 V vs. Li+/Li and an attractive theoretical gravimetric capacity of 3579 mAh/gSi, which in the fully lithiated state corresponds to a volumetric capacity of ≈2190 mAh/cm3, even higher than the one reachable by lithium metal.Silicon-containing anodes are already being introduced in classical lithium-ion batteries. For that system, the lithium-ion conduction across the anode electrode is mainly provided by the liquid electrolyte that fills the pores of the electrode, while the electrical conduction is enhanced by the addition of graphite and/or conductive carbon additives, because crystalline silicon is only a semiconductor. As is well known, the major issue with silicon anodes is the volume expansion of 300% upon lithiation of silicon, inducing severe cracking of µm-sized silicon particles as well as continuous solid electrolyte interphase (SEI) growth, both of which lead to a fast capacity fading.The intrinsic solid nature of all-solid-state batteries opens the possibility of a new electrode concept that has the potential to mitigate the above-mentioned drawbacks of silicon. Indeed, the silicon particles themselves could be used for the lithium-ion conduction across the electrode, so that anode electrodes can be prepared that are free of electrolyte, thereby largely restricting SEI formation to the anode/separator interface .In this work, anodes with >90% weight of silicon are prepared by coating a water-based slurry that contains microscale silicon particles (ca. 2-4 µm diameter) as active material, the rest being made up of LiPAA and NaCMC as binders as well as C65 carbon as conductive additive. The combination of the water-based process and the microscale dimension of the silicon particles make this electrode concept easily scalable and cost-effective.To reach a competitive areal silicon anode capacity of 3 mAh/cm2, with the full utilization of the silicon, only a thin layer is needed (pristine thickness of 8 µm when the anode porosity is 50%). The thickness variation and the anode morphology are being investigated by examining cross-sectional scanning electron microscopy (SEM) images at different states-of-charge (SOC). After the first complete lithiation, the anode consists of a fully dense and compact Li3.75Si alloy block of 15 µm thickness. Upon its complete delithiation, a peculiar porous columnar morphology is formed that on account of the void space between the columns and within the columns retains a thickness of 11 µm. This peculiar morphology was recently reported in the literature (Tan et al., Science 373 (2021), 1494–1499); and seems to be reversible during subsequent lithiation and delithiation processes. For example, our half-cells utilizing an InLi counter electrode and operating at 70 MPa have more than 80% capacity retention after 350 cycles at a rate of C/5, with an average coulombic efficiency higher than 99.9%. The reason for this promising stability could be attributed to the minimal loss of lithium into the SEI, which is limited to the geometrical contact area between the silicon and the solid electrolyte separator.To better understand the electrochemical and mechanical characteristics of these silicon anodes, they are investigated in full-cells, utilizing an NCM composite cathode, while the anode potential is monitored by using a gold wire micro reference electrode (µ-RE) which was recently developed in our group (Sedlmeier et al., J. Electrochem. Soc. 170 (2023) 030536). This specific µ-RE, which has a defined and stable potential, allows to precisely deconvolute the potential curves of cathode and anode, and also to measure and separate the impedance contributions of the two electrodes. Therefore, the impedance of the silicon anode is measured at different SOC to understand how the contact resistances, the charge-transfer resistance, and the solid-state diffusion affect its overall impedance. In particular, the low impedance at high SOC enables to reach a good fast charging rate capability up to 1C without lithium metal plating and dendrite formation, as reported in Figure 1. However, in order to explore whether the fast charging goal of 4C (80% of the capacity in 15 minutes) can be reached, the influence of the carbon additive, operating temperature and applied pressure are being investigated. Figure 1

Atomistic Insight into the Role of Porous Structure in Accommodating the Volume Expansion of Silicon Anodes for Lithium-Ion Batteries

Despite possessing high theoretical gravimetric capacity, the practical utilization of silicon anodes for lithium-ion batteries is still challenging because of poor capacity retention caused by massive volume expansion upon lithium insertion. The use of porosity to tackle this issue has widely been scrutinized, and porous silicon materials have been experimentally shown to have improved cycling stability. To provide a fundamental understanding of the structural and chemical evolution, here, we investigate the atomistic behaviors of porous silicon nanowires during lithiation and delithiation by means of a reactive molecular dynamics method. The simulations show that although the porous nanomaterials undergo a large intrinsic volume expansion similar to the non-porous ones, the hollow space available inside the materials can be exploited for lowering the external expansion via the local structure relaxation in the vicinity of the pore. Due to such relaxation, a small pore undergoes structural collapse during the first charge, suggesting that a relatively large pore diameter and a thin wall thickness are required to maintain the porous structural integrity. The simulations also unveil the evolution of the local stresses generated during lithium migration into and out of the materials, which emphasizes the role of porosity in alleviating the induced stresses.

Highly effective Cu doped SrTiO3 as a cathode driven by oxygen vacancies and redox of Ti4+/Ti3+ and Cu2+/Cu+ for rechargeable alkaline zinc batteries

There is great demand for environmental concerns and explosion hazard batteries. Rechargeable alkaline zinc batteries (RAZBs) have gained significant attention due to their exceptional characteristics such as affordability, safety features, and high theoretical gravimetric capacity. However, practically RAZBs still exhibit poor capacities and limited rechargeability. In this study, copper-doped SrTiO3 (Cu-STO) was successfully synthesized via facile hydrothermal method to be used as a cathode in RAZBs. The capacity of RZABs has enhanced up to 208 mAh g−1 (0.2 A g−1) or 1.5 folds as compared to that of pristine SrTiO3. This is attributed to the presence of oxygen vacancies (Vö) which facilitate the activation of redox-active sites involving Ti4+/Ti3+ and Cu2+/Cu+ ions. Moreover, the fast ions diffusion and good conductivity enable high capacity and rechargeability. Thus, RAZBs showed good rechargeability even after 1000 cycles under 1 A g−1. This provides the underlying potential of Cu-STO as cathode in RAZBs.

A Dithiin-Linked Covalent Organic Polymer for Ultrahigh Capacity Half-Cell and Symmetric Full-Cell Sodium-Ion Batteries.

Sodium ion-batteries (SIBs) are considered as a class of promising alternatives to lithium-ion batteries (LIBs) to overcome their drawbacks of limited sources and safety problems. However, the lack of high-performance electrode materials hinders the wide-range commercialization of SIBs. Comparing to inorganic counterparts, organic electrode materials, which are benefitted from flexibly designable structures, low cost, environmental friendliness, and high theoretical gravimetric capacities, should be a prior choice. Here, a covalent organic polymer (COP) based material (denoted as CityU-9) is designed and synthesized by integrating multiple redox motifs (benzoquinone and thioether), improved conductivity (sulfur induction), and intrinsic insolubility (rigid skeleton). The half-cell SIBs exhibit ultrahigh specific capacity of 1009mAhg-1 and nearly no capacity drop after 650 cycles. The first all-COP symmetric full-cell shows high specific capacity of 90mAhg-1 and excellent rate capability. This work can extend the selection of redox-active moieties and provide a rational design strategy of high-performance novel organic electrode materials.

Cathode host engineering for non-lithium (Na, K and Mg) sulfur/selenium batteries: A state-of-the-art review

Sulfur and selenium have been paid more and more attention in energy storage systems because of their high theoretical specific gravimetric and volumetric capacities. With the increasing scarcity of lithium resources, secondary batteries made of sulfur and selenium coupled with other alkali metal/alkaline earth metals (e.g. Na, K, Mg) are expected to play a vital role in future production and human life. Due to the volume expansion, poor conductivity and shuttle effect, the structure design of cathode, as one of the important roles in metal-S/Se batteries, has always been a hot and difficult point. In the review, various host materials of S and Se are clarified and discussed. Typically, carbonaceous materials are the most widely used hosts, while polar materials are becoming more and more popular in metal-S/Se batteries. Through a comprehensive overview, it is hoped that previous research experiences can provide further reference and guidance for the sustainable development of metal-S/Se batteries.

Screening of Metal-Ion Intercalated Yttrium Carbide and Nitride MXenes for Energy Storage Applications via Density Functional Theory

Rechargeable batteries and energy storage devices play a major role in many facets of human endeavour due to their efficiency and portability. In this work, we investigated the suitability of single-layer intercalated Yttrium-based MXenes Y2CT2 (T= Li, Mg, Al) and Y2NLi2 as potential energy storage materials using the first principle calculation within the framework of the density functional theory approach. Upon intercalation, the lattice constants of the MXenes expand due to the size of the intercalating species and the electrostatic repulsion. We obtained the theoretical gravimetric capacities, open circuit voltages and adsorption energies. The obtained open circuit voltages for Y2CT2 (T= Li, Mg) and Y2NLi2 falls within the voltage window of 0 − 1.0V which has been found to eliminate dendrites formation caused by alkaline metals during the discharge-charge cycle. The adsorption energies indicate the stability of the intercalating ion on the MXenes surfaces except for Al cation. The results are consistent with other studies on similar MXene families in the existing literature. The work may aid the understanding of the electrochemical properties of 2D materials and we recommend Y2CLi2, Y2NLi2 , and Y2CMg2 for future investigation as potential materials for rechargeable batteries.

Mesoporous Cobalt Oxide (CoOx) Nanowires with Different Aspect Ratios for High Performance Hybrid Supercapacitors.

Cobalt oxide (CoOx) nanowires have been broadly explored as advanced pseudocapacitive materials owing to their impressive theoretical gravimetric capacity. However, the traditional method of compositing with conductive nanoparticles to improve their poor conductivity will unpredictably lead to a decrease in actual capacity. The amelioration of the aspect ratio of the CoOx nanowires may affect the pathway of electron conduction and ion diffusion, thereby improving the electrochemical performances. Here, CoOx nanowires with various aspect ratios were synthesized by controlling hydrothermal temperature, and the CoOx electrodes achieve a high gravimetric specific capacity (1424.8 C g-1) and rate performance (38% retention at 100 A g-1 compared to 1 A g-1). Hybrid supercapacitors (HSCs) based on activated carbon anode reach an exceptional specific energy of 61.8 Wh kg-1 and excellent cyclic performance (92.72% retention, 5000 cycles at 5 A g-1). The CoOx nanowires exhibit great promise as a favorable cathode material in the field of high-performance supercapacitors (SCs).

Bi nanoparticles confined in N,S co-doped carbon nanoribbons with excellent rate performance for sodium-ion batteries.

Bismuth (Bi) has emerged as a promising candidate for sodium-ion battery anodes because of its unique layered crystal structure, superior volumetric capacity, and high theoretical gravimetric capacity. However, the large volume expansion and severe aggregation of Bi during the alloying/dealloying reactions are extremely detrimental to cycling stability, which seriously hinders its practical application. To overcome these issues, we propose an effective synthesis of composite materials, encapsulating Bi nanoparticles in N,S co-doped carbon nanoribbons and composites with carbon nanotubes (N,S-C@Bi/CNT), using Bi2S3 nanobelts as templates. The uniform distribution of Bi nanoparticles and the structure of carbon nanoribbons can reduce the diffusion path of ions/electrons, efficiently buffer the large volume change and prevent Bi from aggregating during cycles. As expected, the N,S-C@Bi/CNT electrode shows superior sodium storage performance in half cells, including a high specific capacity (345.3 mA h g-1 at 1.0 A g-1), long cycling stability (1000 cycles), and superior rate capability (336.0 mA h g-1 at 10.0 A g-1).

Unexpected Direct Synthesis of Tunable Redox-Active Benzil-Linked Polymers via the Benzoin Reaction.

Strategies for the sustainable synthesis of redox-active organic polymers could lead to next-generation organic electrode materials for electrochemical energy storage, electrocatalysis, and electro-swing chemical separations. Among redox-active moieties, benzils or aromatic 1,2-diones are particularly attractive due to their high theoretical gravimetric capacities and fast charge/discharge rates. Herein, we demonstrate that the cyanide-catalyzed polymerization of simple dialdehyde monomers unexpectedly leads to insoluble redox-active benzil-linked polymers instead of the expected benzoin polymers, as supported by solid-state nuclear magnetic resonance spectroscopy and electrochemical characterization. Mechanistic studies suggest that cyanide-mediated benzoin oxidation occurs by hydride transfer to the solvent, and that the insolubility of the benzil-linked polymers protects them from subsequent cyanolysis. The thiophene-based polymer poly(BTDA) is an intriguing organic electrode material that demonstrates two reversible one-electron reductions with monovalent cations such as Li+ and Na+ but one two-electron reduction with divalent Mg2+. As such, the tandem benzoin-oxidation polymerization reported herein represents a sustainable method for the synthesis of highly tunable and redox-active organic materials.

(Digital Presentation) Electrochemistry and Structural Study of Manganese Hexacyanoferrate Cathode Material in Aqueous Zn-Ion Battery

Aqueous rechargeable Zinc-ion batteries (ARZIBs) have attracted extensive attention as one of the most promising post-lithium ion battery candidates for large-scale electrochemical applications, because of their low cost, intrinsic safety, and environmental friendliness. The metallic zinc, as an ideal anode material shows high theoretical gravimetric and volumetric capacity of 820 mAh g-1 and 5855 mAh cm-3, low electrochemical potential (-0.76 V vs. SHE) and high abundance.[1,2]Manganese hexacyanoferrate (MnHCF), one of the Prussian blue analogues (PBAs), has attracted widely attention as promising cathode material for Li-ion and post-Li ion batteries. MnHCF is composed of only highly abundant metals and displays large capacity and high discharge potential owning to the two-redox active sites [3-4]. Here, the electrochemical performance of MnHCF was studied in 3 M ZnSO4 aqueous electrolyte with Zn sheet as anode. The battery exhibits high specific capacity (176 mAhg-1) at C/20, and around 61% capacity retention after 50 cycles at C/5. In order to explain the capacity fading problems during cycling, the local geometric, electronic structures, as well as the framework structure change of MnHCF electrode were studied by means of ex-situ X-ray absorption spectroscopy (XAS) and synchrotron X-ray diffraction (XRD). Based on XAS data, no obvious change was observed at the Fe K-edge during cycling, and this indicates that there is no apparent change of the local Fe structural environment. However, the XAS spectra of Mn K-edge exhibit an apparent change after 10 cycles. The Zn K-edge shows a typical -Zn-NC-Fe- structural framework in the cycled samples that resembles the one of zinc hexacyanoferrate (ZnHCF), providing evidence for Zn-Mn partially replacement upon cycling, resulting in dissolution the Mn ion [5]. From the ex-situ XRD data, we found that this phase changes mainly concerns early cycles, because the XRD patterns of the 2nd and 10th cycle are almost identical. ZnHCF phase formed even during the first charge process. The more detailed phase transformation process is still under studying. By combing the ex-situ XAS and XRD data, the charge/discharge mechanism of MnHCF in aqueous Zn-ion battery can be more clearly illustrated. Trócoli, F. La Mantia, ChemSusChem. 8, 2015, 481–485.Tang, L. Shan, S. Liang, J. Zhou, Energy Environ. Sci. 12, 2019, 3288–3304.Mullaliu, J. Asenbauer, G. Aquilanti, S. Passerini, M. Giorgetti. Small Methods, 2019, 1900529.Mullaliu, M. Gaboardi, J. R. Plaisier, S. Passerini, and M. Giorgetti, ACS Applied Energy Materials 3, 2020, 5728.Li, R. Sciacca, M. Maisuradze, G. Aquilanti, J. Plaisier, M. Berrettoni, M. Giorgetti, Electrochim. Acta. 400 ,2021.

The Adoption of Lithiophilic Nano Sn on Cu Current Collector By Electroplating Techniques to Improve the Stability of Lithium Metal Anode

The growing demand for higher energy density batteries is increasing due to needs of electric vehicle (EV) [1]. Until now, it cannot exceed the one-time charging distance of an internal combustion engine vehicle, due to energy limit of batteries. Li metal anode (LMA) is one of the attractive anode candidates because of the lowest electrochemical redox electrode potential (-3.04 V vs. SHE) and the extremely high theoretical gravimetric capacity (3,860 mAh g-1) compared to graphite anode (372 mAh g-1) [2]. However, uneven Li deposition causes dendritic growth leading to low Coulombic efficiency (CE) and safety hazards which is impeding the practical use of LMAs [3]. Recently, to suppress such dendritic growth, various solutions such as introduction of solid-state electrolyte (SSE) [4], artificial solid electrolyte interphase (ASEI) [5], 3D current collector (CC) [6], and lithiophilic materials [7] have been proposed.Among the several approaches, introducing lithiophilic material on a CC is one of the facile and effective strategies to increase the lithiophilicity, and hence to induce the planar growth of Li. Also, assuming that electroplating is largely divided into two steps: nucleation and growth, lithiophilic material can change the intrinsic nucleation behavior by preferentially forming a different phases such as Li alloys [8]. Since the Li nucleation process significantly influences the final growth of Li, different cycling behaviors of LMAs would be expected depending on lithiophilic material [9]. As for the methods to adopt the lithiophilic materials, the electrodeposition is very attractive, since it can easily control the surface morphology, which might affect the Li deposition morphology and the related behavior. In this regard, we chose the tin (Sn) as a lithiophilic material, which can be deposited on Cu CC by electroplating, and moreover have a fast Li ion diffusion coefficient [10].Specifically, in this work, we study the effect of surface morphology of lithiophilic Sn deposited on copper CC by testing Li deposition/stripping behavior for a LMAs. For different morphology, a direct current electrodeposition (DC) and pulsed electrodeposition (PED) were used. Fig.1 is FE-SEM images of Cu@Sn with DC growth and PED growth. Fig.1 (a) shows Sn particles are growing without filling the pores. However, Fig.1 (c) shows Sn particles are growing with filling the pores. At Fig.1 (b) and (d), the morphology difference is conspicuous between DC and PED growth. Fig.1 (b) presents island growth in which nuclei grow on existing nuclei because there is only Ton without relaxation time. While, Fig.1 (d) shows that after rearrangement of deposited atom at Toff, new nucleation sites are created by continuously applying pulses, thereby obtaining the coalescence growth. At Fig.2, Cu@Sn (PED) shows the longer cycle life than bare Cu and Cu@Sn (DC) because Cu@Sn (PED) has an uniformly distributed nano Sn morphology, which provides more sites for Li nucleation to prevent dendritic growth.

High Performance and Long-cycle Life Rechargeable Aluminum Ion Battery: Recent Progress, Perspectives and Challenges.

The rising energy crisis and environmental concerns caused by fossil fuels have accelerated the deployment of renewable and sustainable energy sources and storage systems. As a result of immense progress in the field, cost-effective, high-performance, and long-life rechargeable batteries are imperative to meet the current and future demands for sustainable energy sources. Currently, lithium-ion batteries are widely used, but limited lithium (Li) resources have caused price spikes, threatening progress toward cleaner energy sources. Therefore, post-Li, batteries that utilize highly abundant materials leading to cost-effective energy storage solutions while offering desirable performance characteristics are urgently needed. Aluminum-ion battery (AIB) is an attractive concept that uses highly abundant aluminum while offering a high theoretical gravimetric and volumetric capacity of 2980 mAh g-1 and 8046 mAh cm-3 , respectively. As a result, intensified efforts have been made in recent years to utilize numerous electrolytes, anodes, and cathode materials to improve the electrochemical performance of AIBs, and potentially create high-performance, low-cost, and safe energy storage devices. Herein, recent progress in the electrolyte, anode, and cathode active materials and their utilization in AIBs and their related characteristics are summarized. Finally, the main challenges facing AIBs along with future directions are highlighted.

Decoupling the Dynamics of Zinc Hydroxide Sulfate Precipitation/Dissolution in Aqueous Zn–MnO2 Batteries by Operando Optical Microscopy: A Missing Piece of the Mechanistic Puzzle (Adv. Energy Mater. 30/2022)

Zn–MnO2 Batteries With a high theoretical gravimetric capacity, intrinsic safety, and low cost, aqueous Zn–MnO2 batteries are promising candidates for grid-scale energy storage. However, the charge storage at the MnO2 electrode remains a mystery, delaying real-life applications. In article number 2200722, Frédéric Kanoufi and co-workers shine light on its mechanism using optical microscopy.

Protective Coating Layers via Phosphazene Compounds for Stabilizing Silicon Anode Materials

In recent years, lithium-ion batteries (LIBs) are widely used in electric vehicles (EVs) and mobile energy storage devices (ESDs), which has led to higher requirements for energy density. To fulfill these requirements, tremendous attention has been paid to design advanced LIBs with various silicon active materials as alternative negative electrodes to replace graphite (372 mAh g-1) due to their high theoretical gravimetric capacity (4200 mA h g-1).[1,2] However, silicon as potential anode material suffers from huge volume changes during charging and discharging and has a poor electronic conductivity which negatively impacts the long-term performance and prevents high silicon contents from practical application.[3] Additionally, an unstable crystalline silicon structure tends to pulverization during the (de)lithiation process.[4] To compensate the volume changes, alleviate pulverization and maintain high electronic conductivity, silicon-doped graphite composites with protecting coating layers are a promising approach. In this context, phosphazene compounds are investigated concerning their silicon protecting properties in silicon-doped graphite composites. In detail electrochemical performance measurements in pouch full-cells (NCM523||SiOx/C), supressing gas formation properties and post-mortem analyzes were carried out to characterize phosphazene compounds as additive materials. The introduction of the dual-additive approach in state-of-the-art electrolytes leads to synergistic effects between FEC and phosphazene compounds which accelerate the durability of silicon particles and results in enhanced electrochemical performance. Reference: [1]Zuo X, Zhu J, Muller‐Buschbaum P, Cheng Y, Silicon based lithium‐ion battery anodes: a chronicle perspective review, Nano Energy, 2017, 31, 113‐143.[2]Jimenez A. R., Klöpsch R., Wagner R., Rodehorst U. C., Kolek M., Nölle R., Winter M., Placke T., A step toward high-energy silicon-based thin film lithium ion batteries, ACS Nano, 2017, 11, 5, 4731-4744.[3] Berla A. L., Lee S. W., Ryu I., Cui Y., Nix W. D., Robustness of amorphous silicon during the initial lithiation/delithiation cycle, Journal of power sources, 2014, 258, 253-259.[4] Casimir A., Zhang H., Ogoke O., Amine J. C., Lu J., Wu G., Silicon-based anodes for lithium-ion batteries: Effectiveness of materials synthesis and electrode preparation, Nano Energy, 2016, 27, 359-376.

Three-Dimensional Monolithically Self-Grown Metal Oxide Highly Dense Nanonetworks as Free-Standing High-Capacity Anodes for Lithium-Ion Batteries.

Transition metal oxides (TMOs) have been widely studied as potential next-generation anode materials, owing to their high theoretical gravimetric capacity. However, to date, these anodes syntheses are plagued with time-consuming preparation processes, two-dimensional electrode fabrication, binder requirements, and short operational cycling lives. Here, we present a scalable single-step reagentless process for the synthesis of highly dense Mn3O4-based nanonetwork anodes based on a simple thermal treatment transformation of low-grade steel substrates. The monolithic solid-state chemical self-transformation of the steel substrate results in a highly dense forest of Mn3O4 nanowires, which transforms the electrochemically inactive steel substrate into an electrochemically highly active anode. The proposed method, beyond greatly improving the current TMO performance, surpasses state-of-the-art commercial silicon anodes in terms of capacity and stability. The three-dimensional self-standing anode exhibits remarkably high capacities (>1500 mA h/g), a stable cycle life (>650 cycles), high Coulombic efficiencies (>99.5%), fast rate performance (>1.5 C), and high areal capacities (>2.5 mA h/cm2). This novel experimental paradigm acts as a milestone for next-generation anode materials in lithium-ion batteries, and pioneers a universal method to transform different kinds of widely available, low-cost, steel substrates into electrochemically active, free-standing anodes and allows for the massive reduction of anode production complexity and costs.

Bi@C Nanospheres with the Unique Petaloid Core-Shell Structure Anchored on Porous Graphene Nanosheets as an Anode for Stable Sodium- and Potassium-Ion Batteries.

Bismuth (Bi) has emerged as a prospective candidate as Na-ion and potassium-ion battery anodes because of its unique advantages of low cost, high theoretical gravimetric capacity (386 mAh g-1), and superior volumetric capacity (3800 mAh cm-3). However, the low electronic conductivity and the huge volume expansion of Bi during the alloying/dealloying reactions are extremely detrimental to cycling stability, which seriously hinder its practical application. To overcome these issues, we propose a rational design: Bi@C nanospheres with the unique petaloid core-shell structure are synthesized in one step for the first time and then combined with different contents of graphene (GR) nanosheets to form the composites Bi@C@GR. The Bi@C nanospheres with a core-shell structure are beneficial to shortening the transmission path of electrons/ions and reducing the risk from structural rupture of the particles during cycling. In addition, the combination of Bi@C nanospheres and porous GR could greatly improve the conductivity and prevent the aggregation of particles, which is conducive to better cycling stability and rate performance. Consequently, Bi@C@GR-2 presents a superior reversible capacity for sodium storage (300 mAh g-1 over 80 cycles) and potassium storage (200 mAh g-1 over 70 cycles) at 0.1 A g-1. Furthermore, in situ electrochemical impedance spectroscopy and ex situ transmission electron microscopy are carried out to analyze and reflect the kinetic reaction mechanism and the phase change of the Bi@C@GR-2 electrode during the charge/discharge processes.

In Situ Room-Temperature Cross-Linked Highly Branched Biopolymeric Binder Based on the Diels-Alder Reaction for High-Performance Silicon Anodes in Lithium-Ion Batteries.

Silicon (Si) is an auspicious anode material in next-generation lithium-ion batteries due to its exceptional theoretical gravimetric capacity, environmental friendliness, and high natural abundance. However, the practical application of Si anodes remains a "must-solve" challenge because of its drastic capacity fading that results from the inherent property of drastic volume expansion of Si during repeated lithiation and delithiation. Developing binders employed in robust electrodes has been considered an economical and practical method to affect the electrochemical performance of Si-based electrodes. Some natural polymers have demonstrated good adhesive properties with Si-active materials. However, they have limited capacity to keep the structural integrity of electrodes because the network structures solely based on weak hydrogen bonds are susceptible to deformation during cycling. Herein, we develop an in situ covalently cross-linked three-dimensional (3D) supramolecular network and apply it to the Si electrode to improve cycling performance. This network architecture is constructed using furan-modified branched arabinoxylan of corn fiber gum (CFG) and an ionically conductive cross-linker of maleimido-poly(ethylene glycol) (PEG) through the Diels-Alder reaction. The maleimide groups in PEG can react spontaneously with the furan groups in CFG at room temperature without any other stimulation, thus forming strong covalent bonds in the network. The cross-linked CFG-PEG binder has demonstrated robust adhesive properties with Si-active materials and the current collector. The branching of CFG and functional groups of PEG are conducive to improving the lithium-ion conductivity in the silicon anode, resulting in excellent rate performances. The Si anode with a cross-linked CFG-PEG binder exhibits superior cycling stability. As a result, an in situ cross-linking 3D network as a novel binder has a great potential for fabricating an advanced Si anode in next-generation Li-ion batteries.