Search

In the race to increase lithium-ion cell manufacturing, labor and energy costs quickly ascend to become chief concerns for building new facilities, as conventional electrode designs need significant resources during fabrication. Complicating this issue is an empirical trade-off between environmental friendliness and ethical sourcing. To circumvent this paradox, modified cell designs that employ foils and textiles can significantly change manufacturing considerations if their simple construction can be matched with competitive performance. In this work, we demonstrate one possible cell design for a lithium-ion device that utilizes a fabric and a foil for the cathode and the anode, respectively. For the anode, a prelithiated aluminum foil is chosen, as the room-temperature solubility range of the LiAl phase is well-suited to uptake and release lithium, all while reducing energy or cost-intensive production steps. The cathode is composed of activated carbon fiber textiles, which offer a scalable path to realize sustainability. With such benefits, this device design can potentially change the calculus for the mass production of energy storage devices.

Aluminum metal has long been known to function as an anode in lithium-ion batteries owing to its capacity, low potential, and effective suppression of dendrite growth. However, seemingly intrinsic degradation during cycling has made it less attractive throughout the years compared to graphitic carbon, silicon-blends, and more recently lithium metal itself. Nevertheless, with the recent unprecedented growth of the lithium-ion battery industry, this review aims to revisit aluminum as an anode material, particularly in light of important advancements in understanding the electrochemical lithium-aluminum system, as well as the growth of activity in solid-state batteries where cell designs may conveniently mitigate problems found in traditional liquid cells. Furthermore, this review culminates by highlighting several non-trivial points including: 1) Prelithiatied aluminum anodes, with β-LiAl serving as an intercalation host, can be effectively immortal, depending on formation and cycling conditions; 2) the common knowledge of aluminum having a capacity of 993 mAh g-1 is inaccurate and attributed to kinetic limitations, thus silicon and lithium should not stand alone as the only ‘high-capacity’ candidates in the roadmap for future lithium-ion cells; 3) replacement of Cu current collectors with Al-based foil anodes may simplify lithium-ion battery manufacturing and has important safety implications due to the galvanic stability of Al at high potentials vs. Li/Li+. Irrespective of the type of Li-ion device of interest, this review may be useful for those in the broader community to enhance their understanding of general alloy anode behavior, as the methodologies reported here can be extended to non-Al anodes and consequently, even to Na-ion and K-ion devices.

A two-step modification for the electrochemical performance of Si-based anodes for LIBs is achieved in this study. Firstly, the Cr element is chosen as the doped media into Si bulk via a HEBM method and the fabricated Si-Cr precursors consist of nanocrystalline Si, CrSi2, and amorphous Si. The electrochemical analysis reveals that all ball-milled samples have a similar lithiation/delithiation mechanism with raw Si but the generation of cr-Li3.75Si can be effectively suppressed in the initial stage. The introduction of Cr can enhance cycle stability, volumetric capacity, coulombic efficiency, and electrical conductivity for Si-Cr alloys. The abnormal performance degradation phenomenon in previous Si-CuO system cannot be found here and the suggested Cr ratio is at least 15%. Furthermore, the selected Si85Cr15 precursor is conducted a carbon-coating treatment at 800 ℃, where it shows a 100- and 250-cycle capacity retention of ~93% at 0.2C and ~80% at 0.5C, respectively. The excellent cycle performance is considered related to the limited microstructure change of Si85Cr15@c-PDA due to a certain high-temperature tolerance of CrSi2 at 800 ℃. Meanwhile, it is also attributed to the synergistic effect of CrSi2 and c-PDA, with which Si85Cr15@c-PDA electrode possesses a stable structure and impedance change during the cycles.

Lithium-ion batteries with aluminum anodes had appeared to resolve critical dendrite issues of lithium metal cells in the 1970s. However, the poor cycling performance attributed to aluminum anodes would lead to their obsolescence. In this work, we demonstrate how strategic thermal control in cycling aluminum anodes circumvents the problematic α/β phase transformations that yield poor cycling life. Instead, electrochemical formation of the Li3Al2 and Li2–xAl phases necessitates temperatures slightly above ambient, as the Li3Al2 and Li2–xAl phases are key enablers for high capacity and stable cycling. While delivering a competitive capacity level (ca. 1 Ah kg–1-Al), cycling among those higher-order phases is found to be significantly improved, from several cycles to 100 cycles with ca. 67% capacity retention. Importantly, because modern battery charging is likely to occur above room temperature due to ohmic heating, the thermal conditions explored here are expected to be realized in a variety of applications. Furthermore, we show that elevated temperature is not necessary for aluminum anode delithiation, thus creating additional synergies with many practical scenarios.

Lithium-ion batteries with aluminum anodes had appeared to resolve critical dendrite issues of lithium metal cells in the 1970s. However, the poor cycling attributed to aluminum anodes would lead to their obsolescence. In this work, we demonstrate how strategic thermal control circumvents the problematic α/β phase transformations. The electrochemical formation of Li3Al2 and Li2-xAl, which necessitates temperatures slightly above ambient, are the key enablers for high capacity and stable cycling. While delivering a competitive capacity level (ca. 1 Ah kg-1-Al), those higher-order phases exhibit significantly improved cycling behaviors, from a few cycles to one hundred cycles with ca. 67% capacity retention. Since modern battery charging is likely to occur above ambient due to ohmic heating, the thermal conditions explored here are likely to be realized in a variety of applications. Importantly, this elevated temperature is not necessary for aluminum anode delithiation, thus creating additional synergies with many practical scenarios.

The huge volume change of Si anode with fast capacity degradation limits its commercialization in LIBs. The co-introduction of metal and O elements into the Si bulk fabricating Si-metal silicide-Si oxides composites has been proven an effective way to overcome this issue. Among them, Si-CuO composites, due to financial feasibility and environmentally compatibility, have attracted much attention recent years but still with the unsatisfactory cycle performance. In order to optimize the cycle stability of Si-CuO composites, NiO is firstly introduced into the Si-CuO system with different proportion from 10 % to 20 % by a facile and low-cost HEBM method. The study reveals that Si72CuO8NiO20, with the least volume change percentage of ~ 133 %, has a highest capacity retention of ~ 86. 9% after 100 cycles at 0.2 C and average coulombic efficiency of ~ 99.4 % as well as a competitive volumetric capacity of ~ 1700 Ah·L-1 based on the 2nd lithiation. These results confirm the effectiveness of the NiO introduction to improve the cycle performance of the Si-CuO composites. Moreover, in order to make sure the ball-milled Si-CuO-NiO precursors can be well compatible with the high-temperature post-treatment of coating a carbon layer, the thermal stability of Si72CuO8NiO20 is also conducted with the best cycle stability at 600 °C.

Silicon (Si) is a promising anode material for Li-ion batteries but its application is limited due to its severe volume change during the lithiation/delithiation process, leading to a fast degradation of cycle performance. Applying transition metals to dope into the bulk Si forming active/inactive silicide phase is proved as an effective and practical method to solve the issue. However, the classic high-energy ball milling method is faced with the challenges of strict requirements to the machine, long-time working and difficulty to control the morphology of the product. Aiming to this point, the present study proposes a facile and “softer” method via coating the polydopamine (PDA) with the assistance of CuCl2·2H2O followed by a high-temperature annealing process to successfully fabricate the Si-based anode material with a unique structure of Si-Cu3Si@c-PDA. We firstly achieved the doping of Cu3Si and the coating of carbon layer simultaneously on the surface of Si. Owing to the synergistic effect of carbonized PDA layer and doped Cu3Si phase, both structural stability and electronic conductivity of electrode have been significantly enhanced. The Si-Cu3Si@c-PDA composite anode not only exhibited a high initial reversible capacity of 2356.7 mAh·g-1 with an initial coulombic efficiency of 83.6%, but also demonstrated a good capacity retention of 89.7% after 100 cycles at the current density of 400 mA·g-1. We believe this work would pave a novel way to improve the Si-based anode material.

Combining photodynamic therapy (PDT), chemodynamic therapy (CDT), and ferroptosis is a valuable means for an enhanced anticancer effect. However, traditional combination of PDT/CDT/ferroptosis faces several hurdles, including excess glutathione (GSH) neutralization and preparation complexity. In this work, a versatile multifunctional nanoparticle (HCNP) self-assembled from two porphyrin molecules, chlorin e6 and hemin, is developed. The as-constructed HCNPs exhibit a peroxidase-mimic catalytic activity, which can lead to the in situ generation of endogenous O

In the race to improve lithium-ion cell manufacturing, societal impact is a chief concern as significant resources are required to meet increasing demands. Modified cell designs which employ foils and textiles with simplified constructions offer a scalable path to realize sustainability. Here we demonstrate the novel design for a lithium-ion energy storage device which utilizes a pre-lithiated aluminum foil anode and an activated carbon fiber cathode avoiding energy or cost-intensive production steps.

Silicon (Si) is a promising anode material for Li-ion batteries but its application is limited due to its low electronic conductivity and severe volume change during the lithiation/delithiation process. Recently, coating a carbon layer on the Si surface and doping the alloy phase into the bulk Si have been considered as effective approaches to resolve the aforementioned issues. The present study proposes a facile method via coating the polydopamine (PDA) with the assistance of CuCl2·2H2O followed by a high-temperature annealing process to successfully fabricate the Si-based anode material with a unique structure of Si-Cu3Si@C. Owing to the synergistic effect of carbonized PDA layer and doped Cu3Si phase, both structural stability and electronic conductivity of electrode have been significantly enhanced. The Si-Cu3Si@C composite anode not only exhibited a high initial reversible capacity of 1.44 mAh·cm-2 (2483 mAh·g-1) with an initial coulombic efficiency of 83.2%, but also demonstrated a good capacity retention of 91.3% after 100 cycles at the current density of 0.28 mA·cm-2 (480 mA·g-1). In particular, an excellent reversible capacity of 0.75 mAh·cm-2 (1339 mAh·g-1) after a long-term test of 400 cycles was displayed at the high current density of 1.4 mA·cm-2 (2500 mA·g-1).

Lithium storage in aluminum stems from a phase transformation from lithium-poor α phase (Al, face-centered cubic) to lithium-rich β phase (LiAl, cubic) at room temperature. We investigate the electrochemical lithiation of polycrystalline Al using operando light microscopy coupled with electron backscatter diffraction. The operando videos reveal that the β phase patches expand radially from discrete nuclei with inhibition observed for specific Al grains at the α/β interface. Statistical analyses indicate that these grains have a preferred out-of-plane orientation. This study suggests that lithiation of Al is a whole-grain process that is influenced by grain textures rather than grain boundaries.

Aluminum is well-known to possess attractive properties for possible use as an anode material in Li-ion batteries (LIBs), but effort is still needed to understand how and why it degrades. Herein, investigations of the delithiation and the re-lithiation processes in Al thin films using an established operando light microscopic platform are pursued. Operando videos highlight that the extraction of Li from the β phase (LiAl) is accompanied by fracture and crack formation leading to the detachment of the α phase (Al) from the rest of the electrode. The evolution of mechanical stress in Al thin film electrodes is tracked and shows severe stress asymmetry as phase transformations progress. Combining with the observations from light and electron microscopy, the mechanical stress during dealloying can be explained by Li solubility with the β phase, formation of cracks and of a highly porous Al nanostructure. Although the results pave a difficult path for utilization of the Al/LiAl/Al (α/β/α) phase transformations in future LIBs, they also suggest excellent opportunities when structural changes can be prevented, which otherwise impact the stability of Al-based electrodes.

Despite the tremendous theoretical capacities of new materials for lithium-ion battery (LIB) anodes (e.g. Si, Sn, etc.), the conventional design of these electrodes with binders, current collectors, and conductivity enhancers inhibit the translation of performance gains during commercialization. Therefore, consideration should be given to monolithic materials systems which can increase performance while simultaneously reducing design complexity. In the present study, aluminum–silicon thin-films were synthesized with compositions ranging from 0 to 45 at% Si, and the structure, morphology, and electrochemical behavior of the material as an electrode for LIBs were investigated. This analysis confirms that the Li9AlSi3 phase is formed during initial lithiation, prior to the formation of the β phase, and is recognized as the dominant phase in the Al–Si–Li alloy system. These findings also show that by preventing the formation of the β phase during lithiation of the electrode results in an excellent cycling life performance of 70 at% Al–30 at% Si electrode over 100 cycles at the rate of C/20 and a specific capacity of 650 mA h g−1. In situ stress measurements and ex situ SEM analysis performed during cycling confirm the reversibility such that no degradation or delamination is observed in the films despite the high capacity and long-term cycling.

International audience; The convergence of fiber optic sensing with lithium-ion batteries holds great promise for observing key cell parameters in real time, which is essential to every level of decision making, from design and engineering to finance and management. Optical sensors based on fiber Bragg gratings have recently been demonstrated as an ideal tool for measuring these metrics with sufficient temporal and spatial resolution. In this work, we extend the use of fiber Bragg gratings to polymeric optical fibers which have notably greater thermal and strain coefficients than their common silica counterparts. We demonstrate that a polymer optical fiber sensor paired with a silica-based sensor, both affixed to the external package of a lithium battery, can concurrently generate high fidelity temperature and volumetric expansion data through this non-invasive approach. The quality of this data allows for further assessments as mechanical characteristics associated with dimensional changes of cells may indicate more than simple charging or discharging during cycling. While internal monitoring remains essential for future diagnostics, external monitoring using polymer fiber sensors offers a straightforward, superficial, and cost-effective sensing solution that opens a new avenue for real-time cell assessment, prognostics, and packaging considerations

Lithium-ion battery electrodes contain a substantial amount of electrochemically inactive materials, including binders, conductive agents, and current collectors. These extra components significantly dilute the specific capacity of whole electrodes and thus have led to efforts to utilize foils, for example, Al, as the sole anode material. Interestingly, the literature has many reports of fast degradation of Al electrodes, where less than a dozen cycles can be achieved. However, in some studies, Al anodes demonstrate stable cycling life with several hundred cycles. In this work, we present a successful pathway for enabling long-term cycling of simple Al foil anodes: the β-LiAl phase grown from Al foil (α-Al) exhibits a cycling life of 500 cycles with a ∼96% capacity retention when paired with a commercial cathode. The excellent performance stems from strategic utilization of the Li solubility range of β-LiAl that can be (de-)lithiated without altering its crystal structure. This solubility range at room temperature is determined to be ∼6 at %. Consequently, this design circumvents the critical issues associated with the α/β/α phase transformations, such as volume change, mechanical strain, and formation of nanopores. Application-wise, the maturity of the aluminum industry, combined with excellent sustainability prospects, makes this anode an important option for future devices.

Among elemental semiconductors, tellurium (Te) exhibits unique mechanical and electromechanical properties due to its highly anisotropic crystal structure and mixed interatomic bonding modes. A lac...

Atherosclerosis (AS) is a major cause of cardiovascular diseases, but its effective theranostic measure remains challenging thus far. Macrophages contribute to AS progress in diverse ways such as producing cytokines and reactive oxygen species (ROS), foaming macrophages, and differentiating into pro-inflammatory macrophages. With the aim of constructing a facile and efficacious theranostic system for diagnosis and treatment of AS, a templated self-assembly approach was developed. This strategy involves using indole molecule (indocyanine green (ICG) or IR783) as a template to assemble with probucol (PB) to gain multifunctional nanoparticles (IPNPs or IRPNPs). IPNPs and IRPNPs both showed excellent physicochemical properties, which testified the generality of the indole molecular self-assembly strategy for PB delivery. Besides, the nanoparticles have superior pharmaceutical characteristics including preventing macrophages from differentiating, more efficiently internalizing in inflammatory macrophages, eliminating overproduced ROS, lowering the level of inflammation cytokines, and inhibiting foaming. More importantly, IPNPs displayed effective therapeutic effects in AS model mice when administered via intravenous (i.v.) route. In addition, IPNPs and IRPNPs accumulated more effectively than ICG and IR783 via i.v. injection in the lesion area, and the blood circulation time was extended beyond 24 h. More interestingly, we discovered that the fluorescence imaging ability of IR783 and IRPNPs was more excellent than ICG and IPNPs, respectively. Moreover, a long-term treatment with IPNPs or IRPNPs revealed an excellent safety profile in mice. Accordingly, this self-assembly strategy developed herein is a universal and promising way for the delivery of lipophilic drugs. This study also provides new insights into developing effective theranostic agents for AS.

In this paper, we proposed a fast-automated scheduling method for the final assembly workshop based on the Genetic Algorithm. This method belongs to the technical field of production planning management involving the application of the genetic algorithm and computer simulation in advanced planning and scheduling. Comprehensively, we take into account realistic factors including order priority, lines workload balance and time-consuming to design our three-level scheme evaluation systems. Moreover, the order priority is decided by the Decision Tree model we train. Considering the efficiency, we redesign the coding scheme, variation operator and fitness function to make the Genetic Algorithm serve as an exclusive accelerator for the approximation of optimal schemes. As a result, this fast-automated scheduling method is practical and conducive to production efficiency improvement as well as enterprise benefits maximization.

Stability studies are essential to understanding the limitations of capacitive deionization (CDI) technology and to future commercialization efforts. In this work, the effect of trapped salt ions on stability degradation is explored. The extraction results indicate that Na+ and Cl− exist in aged electrodes and are metastably trapped. Accordingly, a schematic illustration based on the classical Gouy–Chapman–Stern (GCS) model is made to present the dynamic movement of ions near degraded electrodes with regard to the inversion effect. Moreover, a two-electrode voltage sweep test (voltage of null conductivity change (Vncc) test) is developed to simultaneously monitor the active voltage window for CDI. This voltage sweep test is conducted along with long-term operation of CDI cells. The results indicate that the active voltage window between the electrodes decreases gradually, with prolonged cycling, or increases immediately, by inverting the applied voltage of the cell. The shift of Vncc and the desalination ability are found to be strongly correlated, regardless of the cycling history of the electrodes. Therefore, the Vncc test can be a practical tool for sensing both the active voltage window and the desalination ability of carbon-based electrodes during prolonged or continuous CDI operations.

Methane-producing bioelectrochemical systems (BESs) are a promising technology to convert renewable surplus electricity into the form of storable methane. One of the key challenges for this technology is the search for suitable cathode materials with improved biocompatibility and low cost. Here, we study heat-treated stainless steel felt (HSSF) for its performance as biocathode. The HSSF had superior electrocatalytic properties for hydrogen evolution compared to untreated stainless steel felt (SSF) and graphite felt (GF), leading to a faster start-up of the biocathodes. At cathode potentials of −1.3 and −1.1 V, the methane production rates for HSSF biocathodes were higher than the SSF, while its performance was similar to GF biocathodes at −1.1 V and lower than GF at −1.3 V. The HSSF biocathodes had a current-to-methane efficiency of 60.8% and energy efficiency of 21.9% at −1.3 V. HSSF is an alternative cathode material with similar performance compared to graphite felt, suited for application in methane-producing BESs., Our study increases methane-producing BESs’ applicability with a novel cathode, heat-treated stainless steel felt, showing great promise in renewable energy storage.

Wetlands in the Prairie Pothole Region of North America are integrated with farmland and contain mixtures of herbicide contaminants. Passive nonfacilitated diffusion is how most herbicides can move across plant membranes, making this perhaps an important process by which herbicide contaminants are absorbed by wetland vegetation. Prairie wetlands are dominated by native cattail (Typha latifolia) and hybrid cattail (Typha x glauca). The objective of this batch equilibrium study was to compare glyphosate absorption by the shoots and rhizomes of native versus hybrid cattails. Although it has been previously reported for some pesticides that passive diffusion is greater for rhizome than shoot components, this is the first study to demonstrate that the absorption capacity of rhizomes is species dependent, with the glyphosate absorption being significantly greater for rhizomes than shoots in case of native cattails, but with no significant differences in glyphosate absorption between rhizomes and shoots in case of hybrid cattails. Most importantly, glyphosate absorption by native rhizomes far exceeded that of the absorption occurring for hybrid rhizomes, native shoots and hybrid shoots. Glyphosate has long been used to manage invasive hybrid cattails in wetlands in North America, but hybrid cattail expansions continue to occur. Since our results showed limited glyphosate absorption by hybrid shoots and rhizomes, this lack of sorption may partially explain the poorer ability of glyphosate to control hybrid cattails in wetlands.

Limitations of capacitive deionization (CDI) and future commercialization efforts are intrinsically bound to electrode stability. In this work, thermal treatments are explored to understand their ability to regenerate aged CDI electrodes. We demonstrate that a relatively low thermal treatment temperature of ∼500 °C can sufficiently recover the lost salt adsorption capacity of degraded electrodes. Furthermore, a systematic study of electrode replacement clarifies that the desalination ability loss and regeneration for a CDI cell are isolated to the aged anode, as expected. Characterizations of surface functionalities support that the acidic oxygen-containing functional groups formed in situ during cycling undergo thermal decomposition during treatment. The modified Donnan model quantitatively confirms that the surface charges originate from the formation/decomposition of functional groups. Accordingly, the lost pore volume and the increased resistance are recovered during thermal treatments, while the surface morphologies and pore structure of the electrodes are well-preserved. Therefore, thermal treatment can be applied practically to extend the lifetime of aged electrodes. This study also offers insights into strategies for minimizing electrode degradation or in situ regeneration such that the technology gains momentum for future commercialization.

Aluminum is an attractive anode material for lithium-ion batteries (LIBs) owing to its low cost, light weight, and high specific capacity. However, utilization of Al-based anodes is significantly limited by drastic capacity fading during cycling. Herein, a systematic study is performed to investigate the kinetics of electrochemical lithiation of Al thin films to understand the mechanisms governing the phase transformation, by using an operando light microscopy platform. Operando videos reveal that nuclei appear at random positions and expand to form quasi-circular patches that grow and merge until the phase transformation is complete. Based on this direct evidence, models of the lithiation processes in Al anodes are discussed and reaction-controlled kinetics are suggested. The growth rate of LiAl depends on the potential and increases considerably as higher overpotentials are approached. Lastly, improved cycling performance of Al-based anodes can be realized by two approaches: 1) by controlling the lithiation extent, the cycling life of Al thin film is extended from 5 cycles to 25 cycles; 2) the performance can be optimized by adjusting the kinetics. Together, this work offers a renewed promise for the commercialization of Al-based anodes in LIBs where the performance requirements are compatible with the proposed cycle life-extending strategies.

Alloy anodes have been extensively studied over past decades to replace the graphite of lithium-ion batteries (LIBs). Most efforts are made towards those anode materials with high specific capacities such as silicon and germanium. To minimize the negative impacts of the volume expansions during Li incorporation, protective coatings or specific micro- and nanostructures have been suggested, but a commercialization on a larger scale was impeded by such preparation costly procedures. Therefore, the optimal alloy anode candidate should balance the cost, capacity and manufacturing complexity rather than solely maximize the specific capacity. Aluminum, an underappreciated anode material, possesses intrinsic properties that fulfill the criteria mentioned above. The origin of the main capacity of aluminum anode is upon the formation of the β phase (LiAl; ca. 1Ah/g). However, the (de-)alloying processes of Al remain poorly understood, especially at room temperature under which LIBs usually operate. In this study, we investigate the (de-)lithiation that occurs within the solubility range of the β phase Although this Li solubility is highlighted by multiple versions of the Li-Al phase diagrams, the solubility range at low temperatures was not specified yet due to the experimental conditions of previous phase diagram studies (> 400 °C). Various electrochemical analytic tools and methods are used to shed light on the Li solubility within the β phase. The Li solubility range of the β phase is determined to be roughly 5 at% by a potentiostatic charge counting experiment at room temperature. Moreover, the cyclic voltammetry of partially lithiated Al foils shows that the β phase can be (de-)saturated without propagating the phase front towards the α phase. If galvanostatic charge and discharge is smartly controlled by taking into consideration of the solubility range, the cycling life of β-LiAl anode can be significantly improved. Not only does this piece of work provide fundamental data for the β-LiAl phase at room temperature that complements the existing phase diagrams, but also implies that aluminum foil holds great potential as an anode material for the next generation of lithium-based batteries.

Based on current trends in lithium-ion battery (LIB) production and forecasts for immense demand of these energy storage devices, it is evident that all cell components will need dramatic improvement in the future. Although anode materials may be considered by some to be a lower priority, compared to cathode materials, the cost of the anode (and Cu foil current collector) comprise nearly 25% of the materials cost of a LIB cell, and consume ~30% of the volume. Among the possible alternative anode materials for LIBs to replace slurry-based graphite electrodes, alloying materials such as Si, Sn, Al and Ge are promising candidates. Despite the attractive advantages of aluminum-based electrodes (such as low cost, good geographic dispersity and high abundancy), capacity fade due to a large volume change associated with the α/β (Al/LiAl) phase transformation during cycling is the key problem. Al alloy or composite electrodes are a promising strategy for improving the reliability of Al-based electrodes. Among the Al-based monolithic anode materials for LIBs, to the best of our knowledge, Al-rich Al-Si alloys or composites have rarely been investigated. The present work highlights a new achievement towards realizing monolithic, free-standing alloy anodes which can significantly reduce both the cost and processing complexity of LIB electrodes. Herein, we propose a novel strategy to enable the use of aluminum-silicon alloys as monolithic anodes for LIBs. Accordingly, the microstructural, morphological, and electrochemical evolution of Al-Si thin-films of various compositions were investigated, with a focus on understanding the process of Al-Si-Li ternary phase formation during lithiation (in the particular case of excess Al). Ex situ microscopy observations, along with comprehensive electrochemical analysis, suggests that remarkable performance can be achieved by controlling the electrochemical condition for the formation of Al-Si-Li ternary phase, such that no LiAl (β phase) forms during lithiation. In other words, Al-Si-Li ternary phase is cycled within a soft aluminum matrix, thereby avoiding the degradation associated with the de-/lithiation of the β phase [1]. [1] M. H. Tahmasebi, D. Kramer, R. Mönig, and S. T. Boles, “Insights into Phase Transformations and Degradation Mechanisms in Aluminum Anodes for Lithium-Ion Batteries,” J. Electrochem. Soc., vol. 166, no. 3, pp. A5001–A5007, 2019.

Despite the tremendous progress made towards understanding the alloying and dealloying mechanisms in new lithium-ion battery anode materials like silicon and tin, the large volumetric changes that are intrinsic to these materials seem difficult to overcome in the absence of additional coating or nano-structuring methods that inherently increase cost and decrease capacity. Thus, the most likely candidate to replace graphite in the future may not be that which has the absolute highest capacity, but one that has an optimal balance between cost, capacity and processing complexity. Aluminum has significant advantages over other alloy anodes because of its low cost, high abundance, and wide variety of film and foil processing options. If the high theoretical capacity of aluminum (ca. 1 Ah/g or 2.7 Ah/cm3) can be even partially realized, it would be a significant improvement over conventional carbon-based anode materials. Despite the great promise of aluminum as an anode material in lithium-ion batteries, it typically suffers from fast capacity fading upon cycling. Unfortunately, the depth of knowledge concerning the degradation mechanisms of aluminum-based anode electrodes is still scarce. In this work, aluminum and aluminum-based alloys are used to investigate the lithiation, delithiation, and degradation mechanisms in this industrially-friendly materials system. Various in situ and ex situ microscopy methods are employed, along with conventional electrochemical cycling and characterization techniques, to investigate the phase transformations associated with the Al-Li system, in particular from the α-phase (Al) to the β-phase (AlLi), during charging and discharging. Furthermore, substrate curvature methods are used which allow for quantitative insights into the mechanical properties of the film as a function of lithium content. Scanning electron microscopy investigations of the surface morphological evolution of the aluminum-based thin-film electrodes indicate that irreversible damage depends more on the depth of discharge than on the volume contraction during delithiation [1]. These results suggest that aluminum-based anodes may be highly suitable for future lithium-ion battery anodes and implications for commercially available aluminum foils as anode materials will be discussed. [1] M. H. Tahmasebi, D. Kramer, R. Mönig, and S. T. Boles, “Insights into Phase Transformations and Degradation Mechanisms in Aluminum Anodes for Lithium-Ion Batteries,” J. Electrochem. Soc., vol. 166, no. 3, pp. A5001–A5007, 2019.