Graphite Battery Research Articles

Image processing methods and light optical microscopy for in-situ quantification of chromatic change and anode dilation in Li-ion battery graphite anodes during (de-)lithiation

Abstract In Lithium-ion batteries, the graphite anode is known to undergo a noticeable chromatic change during lithiation and de-lithiation by forming graphite intercalation compounds. Additionally, the graphite anode primarily contributes to the volume change of the battery. Using a novel in-situ optical microscopy setup for imaging cross-sections of Li-ion full cells, both effects can be studied simultaneously during charging and discharging. In this work, we describe feature extraction methods to quantify these effects in the image data (3730 images in total) captured during the lithiation and de-lithiation process. Automated and manual evaluations are compared. The images show graphite anodes and NMC 622 cathodes. For colorfulness, we evaluate different methods based on classical image processing. The metrics calculated with these approaches are compared to the results of ColorNet, which is a trainable colorfulness estimator based on deep convolutional neural networks. We propose a supervised semantic segmentation approach using U-Net for the layer thickness measurement and the anode dilation derived from it.

Ionic Liquid Electrolytes with Mixed Organic Cations for Low-Temperature Rechargeable Aluminum–Graphite Batteries

Recently, aluminum–graphite batteries using chloroaluminate ionic liquid electrolytes have been shown to store charge with significant pseudocapacitive contributions, features attractive for energy storage systems that must function with high capacity retention and high specific power at low temperatures. Herein, we present results toward rechargeable aluminum–graphite batteries designed specifically for low-temperature applications, focusing on electrolyte design to reduce the melting point and enhance ion transport properties down to −40 °C. Chloroaluminate ionic liquid electrolytes with mixtures of organic cations, particularly imidazolium cations with different asymmetric functional groups, were used to impart disorder, disrupt ion clustering, and enhance low-temperature ion mobilities. Graphite cathodes with higher pseudocapacitive contributions showed improved specific capacity retention at lower temperatures, while aluminum anodes with higher surface roughness reduced the nucleation energy for aluminum electrodeposition. An aluminum–natural graphite battery with mixed imidazolium cations was shown to exhibit 87% specific capacity retention at −20 °C and 10 mA g–1. Overall, the results demonstrate multiple approaches to improve low-temperature aluminum battery performance and illustrate electrochemical methods that quantify electrolyte properties relevant to ion transport and clustering, which can be universally translated into other battery systems.

Upcycling of spent lithium-ion battery graphite anodes for a dual carbon lithium-ion capacitor

A dual carbon lithium-ion capacitor is designed combining sustainable electrode materials using mechanistically different carbon composites derived from spent lithium-ion battery anodes.

Challenges of prospective life cycle assessment of emerging recycling processes: case study of battery materials recovery

The aim of recycling is not only to preserve raw materials within a circular economy but also to enable a decreased environmental impact by secondary production of materials compared to primary production and other end-of-life options. In order to ensure the sound development of emerging recycling processes from an environmental perspective, the method of life cycle assessment (LCA) should be applied from the early stage on. While several frameworks for prospective LCA of emerging technologies have been proposed in recent years, existing approaches are not intended for application to recycling processes. Therefore, this paper analyses the specific challenges in the LCA of emerging recycling processes as for example varying material quality, definition of system boundaries or handling of by-products in combination with changing process chains and lack of available data. Initial methodological recommendations are given and selectively applied to the use case of Lithium-ion battery recycling. Two emerging recycling processes are evaluated assessing the environmental impacts of battery graphite recovery by flotation combined with leaching and of re-synthesis of cathode active materials using hydrometallurgical processes. The assessment results approve the importance of methodological choice within the LCA of emerging recycling processes and its influence on the further process development.

Breaking the Electronic Conductivity Bottleneck of Manganese Oxide Family for High-Power Fluorinated Graphite Composite Cathode by Ligand-Field High-Dimensional Constraining Strategy.

Primary lithium fluorinated graphite (Li/CFx ) batteries with superior energy density are an indispensable energy supply for multiple fields but suffer from sluggish reaction kinetics of the CFx cathode. Designing composite cathodes emerges as a solution to this problem. Despite the optimal composite component for CFx , the manganese oxide family represented by MnO2 is still faced with an intrinsic electronic conductivity bottleneck, which severely limits the power density of the composite cathode. Here, a cation-induced high-dimensional constraining strategy from the perspective of ligand-field stacking structure topological design, which breaks the molecular orbital hybridization of pristine semiconductive oxides to transform them into the high-conductivity metallic state while competitively maintaining structural stability, is proposed. Through first-principles phase diagram calculations, mixed-valent Mn5 O8 ( ) is explored as an ideal high-dimensional constraining material with satisfied conductivity and large-scale production feasibility. Experiments demonstrate that the as-proposed CFx @ Mn5 O8 composite cathode achieves 2.36times the power density (11399 Wkg-1 ) of pristine CFx and a higher CFx conversion ratio (86%). Such a high-dimensional field-constraining strategy is rooted in the established four-quadrant electronic structure tuning framework, which fundamentally changes the orbital symmetry under the ligand field to overcome the common conductivity challenge of wide transition metal oxide materials.

In‐situ Sacrificial Positive Additive Strategy for the Construction of a Stable Negative Interface in Dual Graphite Batteries

AbstractDue to their merits of affordability, safety, and environmental friendliness, dual graphite batteries (DGBs) have drawn widespread interest as novel energy storage devices. Nevertheless, the development of DGBs is plagued by inferior cyclic stability that arise from the irreversible loss of cations and the anion‐cation crosstalk during the formation of an negative interface. We proposed an in‐situ sacrificial positive additive strategy to enhance the electrochemical performances, based on the decomposability of potassium oxalate monohydrate (K2C2O4⋅H2O). The experimental and computational results show that the positive additive can add cations to support a stable negative interface and suppress the anion‐cation crosstalk. The as‐constructed DGBs with K2C2O4⋅H2O deliver high‐rate capability (31.8 mAh g−1 at 3.0 C) and excellent cyclic stability (∼84.1 % capacity retention after 180 cycles). This work provides a new opportunity of negative interface construction for propelling the commercial evolution of the advanced DGBs.

Emerging dual carbon fiber batteries

Dual graphite battery emerges as a promising renewable energy storage system with merits of a high working voltage, low cost and environment-friendliness. However, energy density is limited because of a low packing density of graphite. We propose for the first time dual carbon fiber batteries (DCFBs) in which carbon fiber functions as both cathode and anode. With a graphite mass loading of ∼30 mg cm−2 at pitch-based carbon fiber (PCF) cloth, the reversible discharge capacity of PCF-PCF type DCFBs (with PCF cloth cathodes/anodes) can reach 72 mAh g−1 at 0.1 C (1 C corresponding to 80 mAh g−1), resulting in an unprecedentedly high areal capacity of ∼2.2 mAh cm−2. Unlike the general applicability of commercialized carbon fiber as DCFBs anode, only PCF out of five kinds of commercialized carbon fibers can function as DCFBs cathode. Meanwhile, PCF-PCF type DCFB enables investigation into distinct electrochemical behaviors of Li+/PF6−intercalation/deintercalation in PCF. Morphological difference of PCF brought about by Li+/PF6− ions, as found out by ex-situ X-ray diffraction (XRD) and ex-situ scanning electronic microscopy/energy dispersive spectroscopy (SEM/EDS) characterizations, facilitates comprehensive understanding of electrochemical behavior of graphite. This work lays good foundations for future exploration into a new arena of dual ion batteries.

Enhanced capacity and thermal safety of lithium-ion battery graphite anodes with conductive binder

Thermal safety is critical for marketable batteries. Numerous safety incidents from graphite anode instability impede lithium-ion battery (LIB) use for large-scale energy storage. Herein, we compare thermal safety and electrochemical performance of graphite anodes with commercial conducting polymer poly (3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) and standard polyvinylidene fluoride (PVDF) binders. Thermal analyses with differential scanning calorimetry (DSC) elucidates thermal runaway mechanisms. Reduced wettability of the PEDOT:PSS binder and lower specific surface area of the graphite anode composite contributes to less heat generation from solid electrolyte interphase (SEI) decomposition as compared to PVDF between 100 and 150ۥ°C, particularly when carbon black (CB) additive is excluded, evolving 143, 37.5, and 102 J g−1 for PVDF/CB, PEDOT:PSS, and PEDOT:PSS/CB composite binders, respectively. Additionally, conducting binders provide enhanced stability against LiXC6, generating less than 16% of the 728 J g−1 from the PVDF/CB graphite anode. In full-cell thermal safety studies with LiCoO2 (LCO) cathode using multimode calorimetry (MMC), this reduces heat generation at temperatures (<140 °C) where thermal runaway may still be circumvented. Electrochemical performance is not sacrificed as PEDOT:PSS/CB provides improved capacity (400 vs. 360 mAh g−1 after 100 cycles at C/5) and kinetics (260 and 189 mAh g−1 at 1C) over PVDF/CB.

Development of an Alternative Binder System for Lithium-Ion Battery Graphite Anodes - Correlation of Fast-Charging Capability with Ionic Pore Resistance and Pore Size Distribution

Binders can have a significant impact on the performance of lithium-ion batteries (LIBs), even though they constitute only a small portion of the battery electrodes. Among others, binders influence mechanical properties of the electrode, like adhesion and cohesion, as well as its electrochemical properties, which include the ionic and electronic conductivity.1 The most commonly used binder system for water-based graphite anodes is a combination of CMC and SBR. CMC ensures good rheological properties and is used as a thickening agent, whereas SBR provides an increased flexibility of the electrode.2–4 However, there are also disadvantages associated with the use of this binder system. CMC is very brittle and provides only a limited Li-ion conductivity, which is especially problematic for thick electrodes and high current densities.5, 6 In addition, CMC/SBR systems show poor electrical conductivity.7 Since fast-charging of LIBs is a key factor to ensure the economic success of battery electric vehicles, in this work a tailored binder system for water-based graphite anodes is developed by combining specific rheological, mechanical and electrochemical properties to enable an improvement in fast-charging capability. The fast-charging capability of the water-based graphite anodes prepared in this work is characterized in pouch cells using a NCM622 cathode. Since the fast-charging capability of anodes is closely related to the ionic resistance within the electrode`s porous structure, as well as its porosity and pore size distribution, electrochemical impedance measurements of symmetrical coin cells are performed to determine the ionic pore resistance. Hg-intrusion porosity measurements also provide information about the pore size distribution of the graphite anodes containing the used binder systems.It is shown that compared to the CMC/SBR binder system, a selective combination of different alternative binders for graphite anodes, based on their rheological, mechanical, as well as electrochemical properties, can improve the fast-charging capability of full cells at 4C (~ 10 mAh cm-2) in the constant-current step by more than 20% with regard to the theoretical capacity. In addition, a direct correlation between the ionic pore resistance and the pore size distribution of the graphite anodes containing the different binder systems with their fast-charging capability could be revealed.

Ultrasonic nondestructive diagnosis of lithium-ion batteries with multiple frequencies

Accurately estimating the state of charge (SoC) in battery management systems (BMSs) requires the measurement of numerous parameters and advanced algorithms. This work studies multifrequency ultrasonic waves to estimate the SoC of Li-ion batteries by sensing the material changes during charge/discharge. A pouch-type LiNi0.6Mn0.2Co0.2O2 (NMC622)||graphite battery cell is designed and fabricated with a capacity of 2.4 Ah. Different ultrasonic testing setups are explored to determine the optimal testing parameters for the battery. An ultrasonic monitoring system is developed to monitor the battery during charge/discharge at 750 kHz, 1 MHz, and 1.5 MHz. Signal processing algorithms are proposed for extracting three ultrasonic features—amplitude, wave velocity, and attenuation. In a three-cycle test, the amplitude histories do not show clear correlations with the SoC. The wave velocities of all three frequencies have an approximately linear relationship with the SoC, which can be used for SoC estimation. Hysteresis behavior is observed for the wave velocity in terms of a larger slope in the discharge process and velocity drop after a close charge/discharge cycle. The wave attenuation is able to capture the material phase transitions during charge/discharge.

Ionic Liquids Based Cocktails as a Composite Redox Electrolyte for Natural Dye-Sensitized Solar Cells

Fatty-imidazolinium electrolytes, waste graphite dispersed composite electrolytes like cocktails (1,3-methyl octyl-1,2,3-benzotiazolium acetate–cis-oleyl-imidazolinium iodide), and graphite exfoliation using cis-oleyl-imidazolinium acetate have been studied to enhance the efficiency of a newly developing dye-sensitized solar cells (DSSCs). The DSSCs were fabricated in a sandwich structure and characterized using Solar Simulator. The graphite exfoliation was conducted by sonication and microwave energy, as well as the electrochemical method. Cis-oleyl-imidazolinium iodide efficiency (0.53%) was highest than stearyl-imidazolinium iodide and palmityl-imidazolinium iodide because cis-oleyl-imidazolinium iodide has a double bond and the longest alkyl chain which triggered a self-assembly structure formation and increased the rate of I-/I3- transport in cells. Then, the efficiency of DSSCs-based composite electrolytes was in the range of 0.020– 0.203%. Dispersion of 0.05% of the graphite results in efficiency enhancement of about 100%, but the greater fraction (0.10%) of the graphite causes a poor performance (lower efficiency), possibly due to interference of the internal electron transportation routes in the DSSC by insoluble graphite. After exfoliation, the conductivity of synthetic graphite (11.58 x 10-1 S/cm), new battery graphite (9.32 x 10-1 S/cm), and battery waste graphite (7.96 x 10-1 S/cm) were increased respectively 10 times, 2 times, and 4 times from the graphite before exfoliation due to changes in crystallinity, the distance between layers, crystal size, formation of multilayer graphene, and the occurrence of π to π* transition. This enhancement of solar conversion efficiency can give a new contribution to the development of DSSC.

Pre-constructed SEI on graphite-based interface enables long cycle stability for dual ion sodium batteries

Lithium batteries have been widely used in all over the world for its high energy density, long-term cycle stability. While the resources of lithium metal and transition metal are limited, which restrict their applications in the grid energy storage. Dual ion sodium batteries (DISBs) possess higher energy density, especially owning high power density for its higher operating voltage (> 4.5 V). Nevertheless, the poor oxidation tolerance of carbonate electrolyte and the co-intercalation of solvents accompanied with anions are main obstacles to make the DISBs commercialization. Herein, a physical barrier (artificial SEI film) is pre-constructed in the Na||graphite batteries to solve these thorny problems. With the CSMG (covered SEI on modified graphite), batteries deliver higher capacity 40 mAh/g even under the current density of 300 mA/g and the capacity retention maintains very well after 100 cycles at a high operating voltage. Moreover, the function mechanism was revealed by in-situ XRD, demonstrating that the pre-constructed SEI can effectively suppress the irreversible phase transition and exfoliation of graphite, resulting from the co-intercalation of anions. Additionally, the work voltage windows of carbonate electrolyte are significantly broadened by establishing electrode/electrolyte interphase. This method opens up an avenue for the practical application of DISBs on the grid energy storage and other fields.

Mesoscale Machine Learning Analytics for Electrode Property Estimation

The development of next-generation batteries with high areal and volumetric energy density requires the use of high active material mass loading electrodes. This typically reduces the power density, but the push for rapid charging has propelled innovation in microstructure design for improved transport and electrochemical conversion efficiency. This requires accurate effective electrode property estimation, such as tortuosity, electronic conductivity, and interfacial area. Obtaining this information solely from experiments and 3D mesoscale simulations is time-consuming while empirical relations are limited to simplified microstructure geometry. In this work, we propose an alternate route for rapid characterization of electrode microstructural effective properties using machine learning (ML). Using the Li-ion battery graphite anode electrode as an exemplar system, we generate a comprehensive data set of ∼17 000 electrode microstructures. These consist of various shapes, sizes, orientations, and chemical compositions, and characterize their effective properties using 3D mesoscale simulations. A low dimensional representation of each microstructure is achieved by calculating a set of comprehensive physical descriptors and eliminating redundant features. The mesoscale ML analytics based on porous electrode microstructural characteristics achieves prediction accuracy of more than 90% for effective property estimation.

Operando odd random phase electrochemical impedance spectroscopy as a promising tool for monitoring lithium-ion batteries during fast charging

Electrochemical impedance spectroscopy (EIS) is a powerful technique for characterization of lithium-ion batteries (LIBs). It has extensively been used in laboratory research, but seldom in industrial applications, e.g., electrical vehicles (EVs). This is because the latter needs EIS measurements during operation, but achieving valid EIS measurements in dynamic conditions has been a long-lasting challenge. In this work, LiNi0.6Mn0.2Co0.2O2 (NMC622)/graphite batteries are characterized by operando odd random phase EIS (ORP-EIS) under practical usage conditions. The validity of the EIS data is quantitatively assessed based on the robust theoretical framework of ORP-EIS. The measured impedance data reveals a continuous evolution of charge-transfer phenomena along changes of state-of-charge (SoC). The results are consistent with conventional stationary EIS data. Moreover, charge-transfer related parameters can be extracted through equivalent electric circuit models or graphical analysis methods from operando ORP-EIS. The parameters exhibit consistent behavior under various charging conditions including different temperatures, C-rates, and state-of-health (SoH). As a proof of concept, operando ORP-EIS provides unique physical insights on top of conventional current/voltage-based monitoring methods, and could be powerful technique to monitor the SoC of the batteries during fast charging.

Aging effect delays overcharge-induced thermal runaway of lithium-ion batteries

This research focuses on the effect of overcharging on aged batteries, and the experiments aim to show the thermal runaway (TR) behavior of batteries with different degrees of aging. In order to clarify the typical behavioral characteristics of overcharge-induced battery thermal runaway, commercial 18,650 type LiMn2O4 (LMO)/graphite batteries with different capacity retention rates (CRRs) were applied for overcharge testing operation. The changes of external characteristics, such as surface temperature, voltage and fire explosion phenomena of aged batteries during the whole process of thermal runaway under overcharge conditions were investigated. The results showed that the battery TR trigger time was negatively correlated with the CRR. The batteries having CRR of 86.7%, 80.8%, and 75.2% took 28.2%, 32.5%, and 52.0% longer than fresh battery to reach the TR triggering temperature. Besides, they took 54.1%, 91.8% and 115.1% longer than fresh battery to reach the lithium plating time point. The deposition of manganese oxide on the cathode surface and the phenomenon of lithium plating on the anode surface together lead to the reduction of reversible lithium. With the deepening of aging, the amount of reversible lithium inside the battery decreases, which is the main reason why the TR trigger time is delayed.

Novel Way to Turn Spent Li-Ion Battery Graphite into Valuable and Active Catalyst for Electrochemical Oxygen Reduction

Battery technology has been recognized as one of the main driving forces and key technologies required to create a carbon-neutral economy and, therefore, batteries are currently one of the most rapidly growing technology sectors due to the rapid rise in the number of electric vehicles (EV´s). Additionally, the employment of Li-ion batteries (LIBs) in portable electronics has become a necessity in the modern world. This produces spend Li-ion batteries (SLIBs) in substantial volumes, it was estimated that in 2019 188,000 tonnes of SLIBs were available for recycling and it is expected that this number will rise to 125 million in 2030.1,2 To obtain the full benefits of electrification the value chain associated with batteries needs to become more sustainable, which strongly depends on the ability of SLIBs recycling to maximize the components return back to materials circulation. However, current SLIBs recycling strategies has been focused on cathode materials alone while largely overlooking the anode of the battery. In turn, anode recycling has so far concentrated mostly on the metal in the electrode and only very recently has the focus shifted towards the recycling of graphite powders.In this work, a novel strategy for recycling SLIB graphite and reforming it as a valuable catalyst material for electrochemical oxygen reduction reaction (ORR) is proposed. A modified Hummers method was applied to fabricate graphene oxide (GO) from SLIB graphite powder. The GO reduction and doping with nitrogen was achieved by pyrolyzing sample at 800 °C in the presence of DCDA. The prepared nitrogen-doped graphene (NG-Bat) was characterised by various physicochemical (SEM, TEM, XRD, Raman and XPS) and electrochemical characterization methods (LSV, EIS, chronoamperometry). For electrochemical characterisation RDE setup with the glassy carbon working electrode, modified with studied catalyst, in 0.1 M KOH solution was used. The physical and electrochemical characteristics of NG-Bat were compared with commercially available nitrogen doped graphene (NG-Com) sample.Based on XRD and Raman data, SLIB-derived graphite maintains its high quality, even after intense exploitation in the batteries and is therefore a valuable material that is worth recycling.3 Homogeneous distribution of carbon, nitrogen, and oxygen in NG-Bat sample was achieved and the overall nitrogen content was found to be 18.4 at%, based on XPS analysis. The onset potential of the ORR for the NG-Bat catalyst material is 0.867 V, and for the NG-Com catalyst 0.797 V. The NG-Bat shows a larger oxygen reduction current and higher electrocatalytic activity than the catalyst based on NG-Com (Figure 1). Based on EIS fitting very different charge transfer resistance and double-layer capacitance values are found, probably caused by different conductivities of the catalyst materials. NG-Bat showed much high electrocatalytic activity towards the ORR than commercial NG-Com based-catalyst material, caused probably by a higher content of active nitrogen species and the presence of carbon vacancies on the surface of graphene, as confirmed by XRD, Raman and XPS experiments.The findings demonstrate that SLIB graphite is still a valuable material and a promising precursor for GO fabrication. One of the potential applications of the SLIB-derived graphene could be the production of catalyst material for the oxygen reduction reaction (ORR), thereby open new avenues to the fuel cell, metal-air battery, and sensor industries.

Impact of Laser Structuring and Calendering on Electrode Characteristics and Cell Performance of Li-Ion Battery Graphite Anodes

The strong compression of electrode coatings is a common approach to enhance the volumetric energy density of Li-ion batteries (LIBs). However, it results in a deterioration of the charge and discharge performance due to an increase in the ionic resistance of the electrodes. This conflict can be addressed by microscopic ion diffusion channels in the electrode coatings, which reduce the ionic resistance and thus enhance the performance of a LIB.In this study, the impact of laser micro structuring on different electrode properties was experimentally investigated for graphite anodes with varying initial porosities. All electrodes showed higher porosities after laser structuring, which can be attributed to an increase in the electrodes’ thicknesses and the removal of material. An equivalent circuit was fitted to the electrochemical impedance spectra of symmetric coin cells consisting of structured and pristine graphite anodes, respectively, to determine the ionic resistances, MacMullin numbers and tortuosities. The values were found to increase for decreasing initial porosities. Laser structuring significantly reduced the ionic resistances, MacMullin numbers and tortuosities of the electrodes in comparison to their pristine counterparts. Furthermore, the different graphite anode configurations were paired with NMC cathodes in coin cells and examined in a discharge rate test. At rates over 1 C, a significant increase in the discharge capacity through laser structuring was observed especially for cells with highly compressed anodes. Conclusively, this study empirically quantifies how laser structuring and calendaring influence different electrode characteristics of graphite anodes and the respective performance in LIBs.

Electrochemical–mechanical multi-scale model and validation with thickness change measurements in prismatic lithium-ion batteries

A multi-scale model able to evaluate volume changes from atomic level of active material up to battery level of prismatic lithium iron phosphate–graphite batteries is presented in this work. The model goes through the scales according to the following steps: changes of lattice parameters as a function of lithium intercalation and consequent lattice volume deformation; active material particles deformation; electrode volume changes and porosity reduction; evaluation of the effects of the hard case on the overall battery thickness change through finite element modelling. From the experimental side, the thickness change of prismatic LFP–graphite batteries is measured during operation at different current rates with high-precision optical sensors and the statistical analysis of the results is carried out. Scanning electron microscope analyses are carried out on electrode samples for measuring model parameters and to give a visual proof of the existence of different scales in lithium ion batteries. Finally, the results of the multi-scale model are validated with the experiments.

Sustainable conversion of biomass to rationally designed lithium-ion battery graphite

The carbon net negative conversion of bio-char, the low value byproduct of pyrolysis bio-oil production from biomass, to high value, very high purity, highly crystalline flake graphite agglomerates with rationally designed shape and size tailored for lithium-ion battery energy storage material is reported. The process is highly efficient, 0.41 g/Wh; the energy content of its co-product of the process, bio-oil, exceeds that needed to power the process. It is shown that the shape of the starting material is retained during the transformation, allowing the ultimate morphology of the graphite agglomerates to be engineered from relatively malleable biomass. In contrast to commercial graphite production, the process can be performed at small scale with low equipment costs, enabling individual research laboratories to produce Li-ion grade graphite with customizable shape, size and porosity for Si/graphite composite and other graphite involved anodes. The mechanism of the graphitization of bio-char, a “non-graphitizable” carbon, is explored, suggesting the molten metal catalyst is absorbed into the pore structure, transported through and transforming the largely immobile biochar. Finally, the transformation of biomass to rationally designed graphite morphologies with Li-ion anode performance that closely mimic commercial shaped graphite is demonstrated.

Solid-Solution-Based Metal Coating Enables Highly Reversible, Dendrite-Free Aluminum Anode

Aluminum-ion batteries have attracted great interest in the grid-scale energy storage field due to their good safety, low cost and the high abundance of Al. However, Al anodes suffer from severe dendrite growth, especially at high deposition rates. Here, we report a simple strategy for constructing a highly reversible, dendrite-free, Al-based anode through directly introducing a solid-solution-based metal coating to a Zn foil substrate. Compared with Cu foil substrates and bare Al, a Zn foil substrate shows a lower nucleation barrier of Al deposition due to the intrinsic, definite solubility between Al and Zn. During Al deposition, a thin, solid-solution alloy phase is first formed on the surface of the Zn foil substrate and then guides the parallel growth of flake-like Al on Zn substrate. The well-designed, Zn-coated Al (Zn@Al) anode can effectively inhibit dendrite growth and alleviate the corrosion of the Al anode. The fabricated Zn@Al–graphite battery exhibits a high specific capacity of 80 mAh·g−1 and an ultra-long lifespan over 10,000 cycles at a high current density of 20 A·g−1 in low-cost molten salt electrolyte. This work opens a new avenue for the development of stable Al anodes and can provide insights for other metal anode protection.