Capacity Anode Research Articles

An artificial aluminum-tin alloy layer on aluminum metal anodes for ultra-stable rechargeable aluminum-ion batteries.

Rechargeable aluminum ion batteries (RAIBs) exhibit great potential for next-generation energy storage systems owing to the abundant resources, high theoretical volumetric capacity and light weight of the Al metal anode. However, the development of RAIBs based on Al metal anodes faces challenges such as dendrite formation, self-corrosion, and volume expansion at the anode/electrolyte interface, which needs the rational design of an aluminum anode for high-performance RAIBs. This work proposes a novel and low-cost strategy by utilizing an alloy electrodeposition method in a low-temperature molten salt system to fabricate an aluminum-tin (AlSn) alloy coating layer on copper foil as the anode for RAIBs, which successfully addresses the issues of dendrite formation and corrosion at the anode/electrolyte interface. The artificial AlSn alloy layer could enhance the active sites for metal Al homogeneous deposition and effectively retard the dendrite formation, which was verified by an in situ optical microscopy study. The symmetric AlSn@Cu cell demonstrates a low average overpotential of ∼38 mV at a current density of 0.5 mA cm-2 and a long-term lifespan of over 1100 h. Moreover, the AlSn@Cu//Mo6S8 full cells deliver a high capacity of 114.9 mA h g-1 at a current density of 100 mA g-1 and maintain ultra-stable cycling stability even over 1400 cycles with a ∼100% coulombic efficiency (CE) during the long-term charge/discharge processes. This facile alloy electrodeposition approach for designing high-performance Al-based anodes provides insights into the understanding of artificial interface chemistry on Al-based anodes and potentially accelerates the design of high-performance RAIBs.

Cathode materials for non-aqueous calcium rechargeable batteries.

Calcium rechargeable batteries based on divalent charge carriers have the potential to meet the future demands for large-scale energy storage applications, due to the crustal abundance of Ca element and the high capacity and high safety of Ca metal anodes. The discernible progress in electrolyte and anode materials has put calcium battery technology a step closer to practice. However, the pursuit of high-voltage, high-capacity and stable cathode materials had been formidable because of the sluggish ion migration kinetics and the instability of host lattices during Ca2+ insertion and extraction. Unlocking the potential of Ca rechargeable batteries particularly hinges on the strategic identification of high-performance cathode materials. Herein, this review summarizes the representative strategies to develop novel cathode materials that allow reversible accommodation of Ca2+ ions for high energy output. The cathode materials can be classified into intercalation-type (layered structure, polyanionic compounds, and Prussian blue analogues) and conversion-type (organic materials, sulfur, and oxygen). The scrutinization of their performances and drawbacks sheds light on the current stage of cathode material advancement and provides informative suggestions for future studies to develop advanced calcium rechargeable batteries with competitive performance.

Solvation and Interfacial Chemistry in Ionic Liquid Based Electrolytes toward Rechargeable Lithium-metal Batteries

Rechargeable lithium metal batteries (LMBs) are highly promising technologies for high-energy-density storage systems due to the low electrochemical potential and high theoretical capacity of lithium metal anode. The electrolyte plays...

Enhancing the electrochemical performance of Sn-Zn alloy anode foil for lithium-ion batteries through microstructure design via accumulative roll bonding technique

In this study, we introduce a novel method for designing microstructures of Sn-45Zn alloy foils utilizing the accumulative roll bonding (ARB) technique, which is one of severe plastic deformation techniques that have been used for refining the microstructures of bulk metals. The electrochemical properties of Sn-Zn foil anodes with various microstructures achieved through the ARB method followed by annealing are investigated in lithium-ion batteries. The degree and characteristics of microstructural damage during electrochemical cyclic tests are also examined in detail to provide insights into the microstructural parameters that critically influence the capacity and cyclic behavior of the Sn-Zn alloy foil anode. Our findings suggest that the ARB-processed Sn-Zn alloy foil, characterized by nearly ultrafine grains composed of Sn and Zn phases with the Zn phase forming a continuous network, exhibits superior battery capacity and cycle life compared to the sample processed using the conventional rolling method. This superiority can be attributed to its unique microstructure obtained through ARB, which reduces pore density, suppresses pore interlinkage, decreases charge transport resistance and nucleation overpotential, and enhances Li-ion diffusivity in the electrode.

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.

Tracking Mn and Zn in Rechargeable Aqueous Zn-MnO2 Batteries By Operando X-Ray Absorption

Zn-MnO2 batteries with mildly acidic electrolytes are a promising chemistry for large scale storage thanks to their remarkable energy density, low cost, and high safety. This is mainly obtained thanks to the high capacity of the Zn metal anode, and the nonflammable character of the aqueous electrolyte. MnO2 is one of the most common cathode of choice, not only for being Earth-abundant, but also because it can undergo a two-electron mechanism, which is however complex and still not fully understood. There is currently agreement in considering for discharge a MnO2 dissolution, leading to soluble Mn2+ and simultaneous precipitation of Zinc Hydroxide Sulfate (ZHS, ZnSO4[Zn(OH2)]3·xH2O). When charging the process is not simply reverted. In fact, a distinct electrochemical profile is observed, with at least two distinct plateaus and a third, apparently pseudocapacitive stage (Figure 1a). A similar multistage profile is observed during the second discharge. Although such profile is characteristic and observed with different MnO2 phases and architectures, the underlying mechanism remains elusive, as it seems to involve mainly poorly crystallized phases.We studied the mechanism by operando X-ray absorption (XAS) at the Mn and Zn K-edges to follow speciation simultaneously and quantitatively in the cathode and in the electrolyte via principal component analysis. Beam intensity needed appropriate regulation to avoid interference with the experiment.Simultaneous X-ray diffraction allowed precise correlation with the MnO2 dissolution and ZHS formation. We found evidence of Mn(III) intermediate occurring during local bond reorganization, which is inferred by the significant evolution of the absorption fine structure region (EXAFS) of the Mn K-edge (Figure 1b). In contrast, minor Zn spectral changes reflect primarily processes of precipitation and dissolution, suggesting that no Zn-Mn mixed phases form during cycling. Figure 1

Carbon: A Ubiquitous Electrode Material for Lithium-Based Rechargeable Batteries

In recent times, research has been directed to develop high-capacity anodes along with high-energy-density (high capacity and high voltage) and safe Lithium-ion battery (LIB) cathodes to power electric vehicles (EV’s). State-of-the-art lithium-ion cells use layered transition metal oxides (LiCoO2, LiNi1/3Mn1/3Co1/3 or LiNi0.8Co0.15Al0.15O2), or Phosphates (LiFePO4), Mn-based spinels (LiMn2O4) as cathodes and graphitic carbon as anode [1-2]. The nominal capacities of most of these cathodes range between 140-180 mAh g-1 when cycled up to 4.2 V. This is only half the specific capacity of graphite anode (372 mAh g-1). Thus, there has been intense research activity in the last decade to develop high-capacity anodes or high energy (high capacity and high voltage) and safe cathodes for lithium-ion batteries (LIBs) [1-2].Eliminating binders and carbon diluents and replacing carbon fiber-based 3D electrode architectures can improve the capacity utilization and C-rate performance, thereby improving energy density, cycle life, and safety of LIBs. The presentation will be focused on the development of organic binder and conducting diluent-free carbon fiber-based 3D electrodes architectures for LIBs, where the conventional copper (Cu) and aluminum foil (Al) foil current collectors are replaced with highly conductive carbon fibers (CFs). In this approach, the petroleum pitch (P-pitch) is used as a binder that adequately coats between the CFs and active nanoparticles (NPs) at high temperatures to form a uniform continuous layer of carbon coating along the exterior surfaces of NPs and 3D CFs. As a result, the electrodes assembly delivers superior electrochemical performances than conventional electrode fabrications. 3D electrode architecture of LiFePO4, FeF3, Li2MnSiO4 cathodes, and Si-C anodes will be presented [3-5].Dual carbon batteries (DCBs) based on LIB electrolytes have been evolving in recent times [5]. In DCBs, both electrodes consist of carbonaceous materials, and the ions from the electrolyte intercalate and deintercalate into the electrode matrix. During the charge, the cations and anions get inserted into the anode and cathode, respectively, and during discharge, the process is reversed. A DCB based on the 3D electrode architecture of carbon (zero transition metal ion) will be discussed. A DCB based on fully graphitic carbon fiber can have a nominal voltage of 4.65 V and can deliver energy densities of 92.7, and 110.9 Wh kg−1 at a power density of 114 W kg−1 for the cells cycled at 3.0–5.0 and 3.0–5.2 V, respectively. It is believed that the study presented here may contribute to the future development of carbon fiber-based dual-carbon and lithium-ion batteries.

Theoretical Study of Nucleation and Growth in Lithium Metal Batteries

The Lithium (Li) Metal Battery (LMB) has shown promise in overcoming the energy storage limitations of the Lithium Ion Battery (LIB) due to the high theoretical capacity of the Li Metal anode. However, it is hindered by an unstable interface and uncontrolled dendrite growth leading to a decrease in coulombic efficiency and safety concerns. While it is difficult to study the electrode-electrolyte interface operando, computational methods can be used to resolve the interface and track the complex physical and chemical phenomena at this location. Specifically, we can use computational modeling to better understand the morphological evolution of deposited Li starting from the nucleation of Li through the growth of the dendrite. In this work we propose a computational method that combines nucleation physics, deposition, and ion transport to study how surface energy and defects impact Li deposition. It is observed that when defects increase the surface energy the nucleation rate decreases resulting in less dendritic growth and more homogenous plating.

(Invited) Safety Behavior of Lyten’s High-Energy Li-S Cells with 3D Graphene™

Safety Behavior of Lyten’s High-Energy Li-S Cells with 3D Graphene™ Ratnakumar Bugga, Celina Mikolajczak, Zach Favors, Karel Vanheusden, Arjun Mendiratta, Jefferey Bell, Penchala Kankanala and Dan CookLyten Inc., 145 Baytech Dr., San Jose, CA 95134Lithium-sulfur (Li-S) batteries are the leading candidates in the next generation high energy systems to supplement or supplant the conventional Li-ion batteries (LIB) in commercial and DoD applications. Unlike other high energy systems with NMC cathodes, Li-S chemistry has the distinct advantage of being unaffected by the criticality and scarcity of raw materials (e.g., Co and Ni), which can pose significant challenges for robust supply chain and stable pricing. Li- S cells can potentially offer 2-3-fold higher specific energy compared to LIBs at significantly lower cost and have better compliance with environmental regulations,1 as well as, a significantly reduced carbon footprint. Despite their numerous advantages, the implementation of Li-S batteries in practice has been impeded by their classic problem of ‘polysulfide (PS) shuttle’, which is a result of PS dissolution in liquid electrolyte, and is a primary cause of poor cycle life.2 Lyten, an advanced materials company founded in 2015, has developed Lyten 3D Graphene™ (3DG) from methane cracking that has a mechanically flexible and electrically conductive framework to counter the volume expansion and low conductivity of sulfur, and a tunable hierarchical porous structure to confine sulfur and PSs and restrict them from shuttling to the Li anode. Lyten has been developing high energy and long-life Li-S cells based on these high-performance, nano-porous carbons. By further optimizing these 3DG materials microstructurally and chemically,3 Lyten has developed sulfur cathodes far superior to those containing commercial nano-porous carbons traditionally used in Li-S cells. In parallel, Lyten has been developing robust Li anodes with protective coatings, advanced electrolytes with reduced PS solubility, separator coatings for low polysulfide crossover, cathodes with low binder, high sulfur loadings and high areal capacities, and high-energy cell designs with minimal excess anode capacity (low N:P ratio) and low quantities of electrolyte (low E/S ratio). These advances have culminated in Lyten Li-S cells with high specific energy (275 Wh/kg), on par with current Li-ion cells, and a cycle life of ~300 cycles @C/3 in coin cells and ~150 full DOD cycles and >1200 during partial cycling in multi-layer pouch (MLP) and cylindrical cells.Another notable advantage of Lyten Li-S cells is their superior abuse tolerance, compared to LIBs, during electrical, mechanical, and thermal abuse. Though Li-S cells, like other Li metal batteries, are suspected to be less safe due to metallic Li, the safety of Lyten Li-S (1.5 Ah) multi-layer pouch and 18650 cylindrical cells has been demonstrated in our preliminary abuse tests (Fig. 1), i.e., nail penetration simulating internal short, external short, overcharge, over-discharge and mechanical crush test. There is no flame, smoke, charring, rupture, or thermal runaway in any of these abuse tests, underlining the innate safety of Lyten Li-S cells. This behavior is consistent with the previous reports, e.g., nail penetration by Offer et al on Oxis’s MLP Li-S cells 4 and overcharge by Huang et al.5 More recently, thermal runaway tests performed on similar Oxis cells show the absence of runaway behavior during thermal ramp tests even up to 300oC, especially in cells with lean electrolyte. We are planning to perform a full suite of safety testing including ARC (Accelerated Rate Calorimetry) on larger prototype cells (4-5 Ah) to be fabricated on our pilot cell manufacturing line , which has recently been commissioned. In this paper, we will describe our recent results on Lyten Li-S cells both in performance and abuse testing. References Chen et al, "Toward Practical High-Energy-Density Lithium-Sulfur Pouch Cells: A Review", Adv. Mater. 2022, 2201555.V. Mikhaylik and J. R. Akridge, “Polysulfide Shuttle Study in the Li-S Battery System”, J. Electrochem. Soc., 151, A1969-A1976 (2004).Lyten patent on "Carbonaceous material for Li-S cells" US patent 11309 545 B2, April 19, 2022.Hunt et al., J. Energy Storage, 2, 25 (2015).Huang, et al., J. Energy Storage Materials, 30, 87 (2020). Figure 1

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

Enhanced Sodium Ion Batteries' Performance: Optimal Strategies on Electrolytes for Different Carbon-based Anodes.

Carbon-based materials have emerged as promising anodes for sodium-ion batteries (SIBs) due to the merits of cost-effectiveness and renewability. However, the unsatisfactory performance has hindered the commercialization of SIBs. During the past decades, tremendous attention has been put into enhancing the electrochemical performance of carbon-based anodes from the perspective of improving the compatibility of electrolytes and electrodes. Hence, a systematic summary of strategies for optimizing electrolytes between hard carbon, graphite, and other structural carbon anodes of SIBs is provided. The formulations and properties of electrolytes with solvents, salts, and additives added are comprehensively presented, which are closely related to the formation of solid electrolyte interface (SEI) and crucial to the sodium ion storage performance. Cost analysis of commonly used electrolytes has been provided as well. This review is anticipated to provide guidance in future rational tailoring of electrolytes with carbon-based anodes for sodium-ion batteries.

Reversible growth of solid electrolyte interface enhances charge capacity in cobalt sulfide-carbon nanotube anodes

The development of high-performance anode materials for lithium-ion batteries is a critical aspect of advancing energy storage technology. This study presents a novel approach to improve the charge capacity of anodes by harnessing the reversible growth of the solid electrolyte interface (SEI). This work focuses on cobalt sulfide (Co9S8) nanoparticles incorporated into a porous carbon nanotube (CNT) structure. Through a two-step pyrolysis process, Co9S8CNT composites, characterized by their conductive and mechanically robust CNT matrix are successfully synthesized. These Co9S8CNT anodes exhibit excellent initial charge capacity (560.5 mAh g−1 at 100 mA g−1) and remarkable stability, with a charge capacity of 633 mAh g−1 after 1000 cycles at 1000 mA g−1, accompanied by a Coulombic efficiency exceeding 99 %. Notably, this investigation reveals that the growth of the SEI plays a pivotal role in enhancing the charge capacity. Through in-situ Raman spectroscopy and other analytical techniques, it is suggested that the reversible reduction of organic solvent molecules within the large polymeric SEI is responsible for the increased charge capacity. This unique phenomenon is characterized by changes in the SEI's composition, driven by the charge and discharge processes. This study is a novel attempt to report a SEI's reversible growth that results in improved charge capacity, contrasting with prior research where SEI growth typically leads to capacity loss. Understanding this stable system provides valuable insights into increasing the cycle life and charge capacity of anodes, not only for transition metal sulfides but also for broader applications in energy storage.

Constructing Ag@SiO2-TiO2 Nanofiber Interlayers with a Three-Dimensional Lithiophilic Gradient Framework for an Ultrastable Lithium Metal Anode.

Lithium metal batteries have become one of the most promising rechargeable batteries due to the ultrahigh theoretical specific capacity of the Li metal anode. However, the Li dendrite growth and volume change of the Li metal anode during repeated Li plating-stripping cycles restrict the practical viability. Herein, a unique lithiophilic gradient structure of uniformly incorporating Ag nanoparticles into a three-dimensional (3D) nanofiber framework with amorphous SiO2 and TiO2 hybrids was prepared by an electrospinning process and used as a multifunctional interlayer between the pristine separator and Li metal foil. The 3D framework not only possesses excellent flexibility but also alleviates volume changes, which can withstand massive Li loading and promote uniform Li+ distribution. In addition, the 3D lithiophilic gradient structure allows for regulable Li+ flux and suppresses Li dendrite growth. Impressively, the Li||Li symmetric batteries with Ag@SiO2-TiO2 interlayers exhibit a prolonged lifespan of 1500 h at 0.5 mA cm-2 for 0.5 mAh cm-2. The full cells coupled with the Ag@SiO2-TiO2 interlayer show a capacity retention rate of 94.6% after 1000 cycles and a high rate capability. This work provides promising guidance for the design of a gradient-distributed lithiophilic structure toward an ultrastable Li metal anode.

Acid-base encapsulation prepared N/P co-doped carbon-coated natural graphite for high-performance lithium-ion batteries

The incorporation of natural graphite as an anode material effectively enhances the lithium storage capacity of lithium-ion batteries. However, the lower specific capacity of graphite anodes and the slow dynamics limit the application of fast charging in daily life. In this work, we proposed an acid-base neutralization strategy to prepare N/P co-doped carbon coated natural graphite for high-performance lithium-ion batteries. Electrochemical testing shows that the prepared NG-PN@C electrode has a first discharge specific capacity of 429.61mAh/g and a high initial Coulombic efficiency (ICE) of 87.39 %, exhibiting a capacity three times higher than that of the commercial natural graphite at a rate of 3C. The enhanced performance can be attributed to the synergistic interplay between N/P co-doping and carbon coating. This interplay heightens the chemical reactivity of the graphite surface, an appropriate introduction of heteroatom into graphite (carbon) hosts is beneficial for Li heterogeneous nucleation and thus renders a uniform Li deposition. In addition, the stable carbon layer of about 3 nm can mitigate the volume expansion throughout cycling and improve rate capability and long-term cycling performance. This simple and low-cost acid-base neutralization strategy not only provides an eco-friendly method for the modification of graphite anodes, achieving doping of N/ P and coating a carbon layer on graphite but also offers inspiration for the advancement of alternative nanocomposites dedicated to improving their electrochemical properties.

Improving Natural Microcrystalline Graphite Performances by a Dual Modification Strategy toward Practical Application of Lithium Ion Batteries.

Microcrystalline graphite (MG), as a kind of natural graphite (NG), holds great potential for use as an anode material for lithium-ion batteries (LIBs) due to low raw material cost, good electrolyte compatibility, and relatively long cycle life. Nevertheless, the relatively low reversible capacity and poor initial Coulombic efficiency (ICE) of the MG anode largely limit its practical application in LIBs. In order to improve the lithium storage capacity of MG, three kinds of oxidant intercalators are applied to treat the original MG, and the as-obtained MG is further modified by a thin carbon layer. The results indicate that using H2SO4-C2H2O4 as oxidant intercalators and subsequent carbon coating layer modification are the optimum techniques, and they can increase the interlayer distance, introduce defects to decrease the volume expansion, and generate channels for fast Li+ diffusion. Meanwhile, the carbon coating layer can reduce the specific surface area of graphite and greatly improve the ICE and cycling performance. Especially, the OEMGC-2 anodes prepared by the dual modification strategies represent a high reversible capacity of 349.4 mA h g-1 at 0.2C with a satisfactory ICE of 90.2%, indicating that the MG can also be considered as a high performance and low-cost anode material of LIBs.

GeO2 crystals embedded germanium phosphate glass with high electrochemical properties as an anode for lithium‐ion battery

AbstractThe continuous development of portable devices and new energy vehicles has led to an increasing demand for high‐performance lithium‐ion batteries (LIBs), and anode materials, as a key part of LIBs, are being explored. Germanium‐based anode materials are considered to have good potential for application because of their high theoretical capacity. In this work, a germanium phosphate glass precipitating GeO2 microcrystal was designed and used in LIBs as anode materials for the study. The presence of GeO2 crystals increases the specific surface area and also provides more reaction sites for lithiation reaction, resulting in the capacity of the glass anode. The discharge specific capacity of the germanium‐phosphorus glass anode was as high as 740.9 mAh g−1 after 600 cycles at a current density of 500 mA g−1. Interestingly, the synergistic effect between the glass matrix and the crystals not only increases the cycling capacity but also enhances the cycling stability of the structure.

Chemical contributions to silicon anode calendar aging are dominant over mechanical contributions

Silicon (Si) anodes are a promising candidate for increasing the energy density of lithium (Li)-ion batteries for electric vehicles. However, they have recently been identified as having poor calendar life that is insufficient for commercial needs, in addition to the well-known issue of their poor cycle life resulting from large volume expansion. Here, a specially designed protocol with variable rest periods between intermittent cycling is used to evaluate the impact of the mechanical disruption of Si and solid electrolyte interphase (SEI) from cycling on calendar aging measurements. Si was found to undergo more mechanical degradation during calendar aging with intermittent cycling than graphite. However, Si anode capacity fade was still dominated by time, especially for rest periods greater than or equal to 1 month between cycling. Postmortem dQ/dV half-cell analysis indicated this was mainly due to Li inventory loss and an increase in electrode resistance. Isothermal microcalorimetry further demonstrated that Si passivation is more disrupted than graphite passivation with intermittent cycling and suggested that there may be a chemical buildup of a detrimental species in the electrolyte, leading to a large spike in heat after the Si and SEI are disrupted by cycling.

Unlock the full potential of carbon cloth-based scaffolds towards magnesium metal storage via regulation on magnesiophilicity and surface geometric structure

The development of rechargeable magnesium (Mg) batteries is of practical significance to upgrade the electric energy storage devices due to exceptional capacity and abundant resources of Mg-metal anode. However, the reversible Mg electrochemistry suffers from unsatisfied rate capability and lifespan, mainly caused by non-uniform distribution of electrodeposits. In this work, a fresh design concept of three-dimensional carbon cloths scaffolds is proposed to overcome the uncontrollable Mg growth via homogenizing electric field and improving magnesiophilicity. A microscopic smooth and nitrogen-containing defective carbonaceous layer is constructed through a facile pyrolysis of ZIF8 on carbon cloths. As revealed by finite element simulation and DFT calculation results, the smooth surface endows with uniform electric field distribution and simultaneously the nitrogen-doping species enable good magnesiophilicity of scaffolds. The fine and uniform Mg nucleus as well as the inner electrodeposit behavior are also disclosed. As a result, an exceptional cycle life of 500 cycles at 4.0 mA cm−2 and 4.0 mA h cm−2 is firstly realized to our best knowledge. Besides, the functional scaffolds can be cycled for over 2200 h at 2.0 mA cm−2 under a normalized capacity of 5.0 mA h cm−2, far exceeding previous results. This work offers an effective approach to enable the full potential of carbon cloths-based scaffolds towards metal storage for next generation battery applications.

Lithium zinc/lithium iodide composite modified layer toward highly stable lithium metal anodes

Lithium metal batteries (LMBs) are considered by most researchers as among the most prospective next-generation high energy density storage devices because of high theoretical capacity (3860 mAh g − 1) and low reduction potential (–3.040 V compared to standard hydrogen electrode) of Li metal anode. Nevertheless, the uncontrollable dendrite growth of the Li metal anode during cycling hinders the commercial application of LMBs. Herein, we put forward a hybrid protective layer containing LiZn alloy and LiI at the surface of the Li metal anode. Thanks to the "lithiophilic" feature of LiZn alloy and LiI having a low surface Li+ diffusion energy barrier, the constructed homogeneous hybrid protective layer can reduce the nucleation barrier and facilitate Li+ rapid diffusion. As a consequence, Li metal anode exhibits a smooth plating/stripping morphology and can suppress the dendrite formation. Notably, the constructed ZI@Li || ZI@Li symmetrical cell realizes stable cycling for 470 h at 2 mA cm−2 and 2 mAh cm−2, and LMBs matched with commercial LiFePO4 cathode deliver greatly enhanced electrochemical properties. This hybrid protective layer provides a feasible strategy to realize even plating/stripping of Li metal, which would promote the high energy density LMBs for practical applications.

Experimental Considerations of the Chemical Prelithiation Process via Lithium Arene Complex Solutions on the Example of Si‐Based Anodes for Lithium‐Ion Batteries

Losses of Li inventory in lithium‐ion batteries lead to losses in capacity and can be compensated by electrode prelithiation before cell assembly or before cell formation. The approach of chemical prelithiation, for example, via Li arene complex (LAC)‐based solutions is technically an apparently simple and promising approach. Nevertheless, as shown herein on the example of Si‐based anodes and LAC solutions based on 4,4′‐dimethylbiphenyl (4,4′‐DMBP), several practical challenges need to be considered. Given their reactivity, the LAC solution can not only decompose itself within a range of a few hours, as seen by discoloration and confirmed via mass spectrometry, but can also decompose its solvent and binder of added composite electrodes. Effective prelithiation requires an excess in capacity of the LAC solution (relative to anode capacity) and optimized system characteristic conditions (time, temperature, etc.) as exemplarily shown by comparing Si‐based nanoparticles with nanowires. It is worth noting that the prelithiation degree alone does not determine the boost in cycle life, but relevantly depends on previously applied prelithiation conditions (e.g., temperature), as well.