Search

Pseudocapacitors are an emerging class of energy storage materials that offer an attractive compromise between the energy density of batteries and power density of electric double‐layer capacitors. Decreasing particle size and increasing surface area of battery materials is a common approach for introducing pseudocapacitive behavior and increasing power density. However, in many cases, as the crystal size is reduced, lattice disorder of unknown extent is also introduced, making it difficult to characterize the relative contribution of size and disorder to fast‐charging performance. In this work, a series of nanostructured MoS2 materials are synthesized with different crystallite sizes and degrees of crystallinity to decouple the effects of size and disorder on charge/discharge kinetics. The extent and type of disorder in each material is quantified by total X‐ray scattering experiments and pair distribution function analyses. Electrochemical characterization, including galvanostatic rate capability, cyclic voltammetry, and various kinetic analyses, are used to demonstrate that both decreasing particle size and introducing lattice disorder are effective strategies for increasing charge storage kinetics, and that the effects are additive. Finally, operando X‐ray diffraction measurements show that both size and disorder can be used suppress first‐order Li+ intercalation‐induced phase transitions, a key feature for enabling pseudocapacitive charge storage. [ABSTRACT FROM AUTHOR]

Pseudocapacitors are an emerging class of energy storage materials that offer an attractive compromise between the energy density of batteries and power density of electric double‐layer capacitors. Decreasing particle size and increasing surface area of battery materials is a common approach for introducing pseudocapacitive behavior and increasing power density. However, in many cases, as the crystal size is reduced, lattice disorder of unknown extent is also introduced, making it difficult to characterize the relative contribution of size and disorder to fast‐charging performance. In this work, a series of nanostructured MoS2 materials are synthesized with different crystallite sizes and degrees of crystallinity to decouple the effects of size and disorder on charge/discharge kinetics. The extent and type of disorder in each material is quantified by total X‐ray scattering experiments and pair distribution function analyses. Electrochemical characterization, including galvanostatic rate capability, cyclic voltammetry, and various kinetic analyses, are used to demonstrate that both decreasing particle size and introducing lattice disorder are effective strategies for increasing charge storage kinetics, and that the effects are additive. Finally, operando X‐ray diffraction measurements show that both size and disorder can be used suppress first‐order Li+ intercalation‐induced phase transitions, a key feature for enabling pseudocapacitive charge storage. [ABSTRACT FROM AUTHOR]

H+ co‐intercalation chemistry of the cathode is perceived to have damaging consequences on the low‐rate and long‐term cycling of aqueous zinc batteries, which is a critical hindrance to their promise for stationary storage applications. Herein, the thermodynamically competitive H+ storage chemistry of an attractive high‐voltage cathode LiMn2O4 is revealed by employing operando and ex‐situ analytical techniques together with density functional theory‐based calculations. The H+ electrochemistry leads to the previously unforeseen voltage decay with cycling, impacting the available energy density, particularly at lower currents. Based on an in‐depth investigation of the effect of the Li+ to Zn2+ ratio in the electrolyte on the charge storage mechanism, a purely aqueous and low‐salt concentration electrolyte with a tuned Li+/Zn2+ ratio is introduced to subdue the H+‐mediated charge storage kinetically, resulting in a stable voltage output and improved cycling stability at both low and high cathode loadings. Synchrotron X‐ray diffraction analysis reveals that repeated H+ intercalation triggers an irreversible phase transformation leading to voltage decay, which is averted by shutting down H+ storage. These findings unveiling the origin and impact of the deleterious H+‐storage, coupled with the practical strategy for its inhibition, will inspire further work toward this under‐explored realm of aqueous battery chemistry. [ABSTRACT FROM AUTHOR]

The paradigm shift toward the closed‐loop recycling of spent lithium‐ion batteries necessitates the direct, efficient cathode recovery that goes beyond the traditional pyrometallurgy and hydrometallurgy techniques, meanwhile avoiding substantial energy consumption, tedious procedures, or chemical contamination. In this study, a straightforward, dual‐functional upcycling approach is presented for the spent nickel‐rich cathodes to boost their high‐rate performance. Specifically, the protocol rationally employs the Li vacancy within the degraded oxide to minimize the La diffusion barrier, expanding the lattice spacing of the layered structure; the Li+ conductive, conformal LiLaO2 encapsulation further suppresses the interfacial acid corrosion and structural deterioration into the rock‐salt phase. Transmission‐mode X‐ray diffraction tracks the reversible lattice breathing of the regenerated cathode in operando, suggesting the continuous, kinetically boosted solid‐solution process with all the microcracks repaired. The as‐assembled regenerated LiNi0.8Co0.1Mn0.1O2/Graphite pouch cell (1.4Ah) thus achieves 91.0% capacity retention for 500 cycles, the energy density of 277 Wh kg−1 as well as extreme power output of 1030 W kg−1 at the cell level. This upcycling strategy paves the way for value‐added utilization of the retired Ni‐rich cathodes in practical high‐rate battery prototypes. [ABSTRACT FROM AUTHOR]

Lattice oxygen redox reactions dedicate the extra retrievable capacities from the lithium‐rich layered oxides (LLOs) cathodes, however, the widespread adoption of which in the energy‐dense batteries faces a series of obstacles, such as oxygen loss during the initial activation, cycling‐induced structural degradation as well as the retard Li+ diffusivity impeded by the interfacial impurities. Here, a Lewis acid gas treatment of LLOs is proposed, namely the PF5 etching to enhance the cycling endurance and high‐temperature tolerance of the electrode. The multiscale modifications involve the F− doping in the bulk lattice, the phosphate coating to kinetically suppress the O2 release as well as the removal of surface impurities in a single step. The gas‐phase treatment constructs a continuous pathway across the densely‐packed LLO electrode, enhancing Li+ diffusivity by fivefold compared to the untreated electrode. Notably, the transmission‐mode operando X‐ray diffraction of the modified LLOs cathode confirms a 71.4% reduction of self‐discharge rate during the idle charged state at 55 °C, as well as the 16% mitigation of lattice contraction (Δc/a) during the dynamic galvanostatic cycling. By pairing the lithium foil (50 µm) with the modified LLO cathode (12.75 mg cm−2) in a pouch‐format cell model, the 0.2 Ah prototype achieves the gravimetric energy/power densities as well as cycling endurance across a wide temperature range. This scalable, Lewis‐acid gas modification strategy presents a practical approach for deploying LLOs in energy‐dense cell prototyping. [ABSTRACT FROM AUTHOR]

Alkaline iron (Fe) batteries are attractive due to the high abundance, low cost, and multiple valent states of Fe but show limited columbic efficiency and storage capacity when forming electrochemically inert Fe3O4 on discharging and parasitic H2 on charging. Herein, sodium silicate is found to promote Fe(OH)2/FeOOH against Fe(OH)2/Fe3O4 conversions. Electrochemical experiments, operando X‐ray characterization, and atomistic simulations reveal that improved Fe(OH)2/FeOOH conversion originates from (i) strong interaction between sodium silicate and iron oxide and (ii) silicate‐induced strengthening of hydrogen‐bond networks in electrolytes that inhibits water transport. Furthermore, the silicate additive suppresses hydrogen evolution by impairing energetics of water dissociation and hydroxyl de‐sorption on iron surfaces. This new silicate‐assisted redox chemistry mitigates H2 and Fe3O4 formation, improving storage capacity (199 mAh g−1 in half‐cells) and coulombic efficiency (94 % after 400 full‐cell cycles), paving a path to realizing green battery systems built from earth‐abundant materials. [ABSTRACT FROM AUTHOR]

[Display omitted] Lithium cobalt phosphate (LiCoPO 4) has great potential to be developed as a cathode material for lithium-ion batteries (LIBs) due to its structural stability and higher voltage platform with a high theoretical energy density. However, the relatively low diffusion of lithium ions still needs to be improved. In this work, Fe and Zn co-doped LiCoPO 4 : LiCo 0.9-x Fe 0.1 Zn x PO 4 /C is utilized to enhance the battery performance of LiCoPO 4. The electrochemical properties of LiCo 0.85 Fe 0.1 Zn 0.05 PO 4 /C demonstrated an initial capacity of 118 mAh/g, with 93.4 % capacity retention at 1C after 100 cycles, and a good capacity of 87 mAh/g remained under a high current density of 10C. In addition, the diffusion rate of Li ions was investigated, proving the improvement of the materials with doping. The impedance results also showed a smaller resistance of the doped materials. Furthermore, operando X-ray diffraction displayed a good reversibility of the structural transformation, corresponding to cycling stability. This work provided studies of both the electrochemical properties and structural transformation of Fe and Zn co-doped LiCoPO 4 , which showed that 10 % Fe and 5 % Zn co-doping enhanced the electrochemical performance of LiCoPO 4 as a cathode material in LIBs. [ABSTRACT FROM AUTHOR]

Eliminating cobalt from high‐nickel layered oxide cathodes lowers the cost of lithium‐ion batteries for electric vehicles. However, cobalt‐free cathodes with high Mn4+ and Ni2+ contents are prone to Li/Ni mixing after synthesis, potentially compromising battery energy density, rate capability, and cycling stability. Without cobalt facilitating cation ordering in the layered structure, the degree of Li/Ni mixing in cobalt‐free cathodes depends heavily on the calcination conditions. In this study, a systematic exploration of calcination temperatures and LiOH ratio for LiNi0.9Mn0.1O2 (NM‐90) provides detailed insights into the optimal synthesis conditions for high‐capacity cobalt‐free cathodes with extended cycle life. Surprisingly, high Li/Ni mixing does not necessarily lead to poor cycling stability whereas low Li/Ni mixing does not guarantee a long cycle life. More importantly, although excessive calcination temperature can further decrease Li/Ni mixing, it does not necessarily enhance capacity. Instead, the pernicious effects from the H2 → H3 phase transition are amplified due to a pronounced two‐phase reaction. An extensive suite of chemical and structural characterization methods uncovers a correlation between elevated calcination temperature, phase transformation, cation ordering, and capacity fading behavior: "overcooking" high‐nickel, cobalt‐free cathodes induce structural arrangement toward that of LiNiO2, with exacerbated lattice distortion and surface instability accelerating capacity fade. [ABSTRACT FROM AUTHOR]

Sodium‐ion batteries (SIBs) represent a viable substitute to lithium‐ion batteries due to their affordability and resource abundance. For SIBs, antimony (Sb) shows potential as anode material but is impeded by the high volumetric variations. Here the challenges of Sb sodium storage by introducing the nanostructured Cu substrate for enhanced Sb adhesion and morphology optimization is addressed, which is realized by fused deposition modeling (FDM) printing of Cu substrate, subsequent high‐temperature sintering, and electrodeposition of Sb. In SIBs, the Sb deposited on three dimensional (3D) printed Cu substrate performs improved cycling stability compared with that of Sb@Cu with commercial Cu foil substrate, which can be attributed to the nanostructure of the 3D‐Cu substrate. Such architecture of 3D‐Cu induces the generation of pine‐leaf‐like Sb clusters to promote stability and kinetics, and it aids the adhesion between the Sb cluster and 3D‐Cu substrate for preventing the Sb detachment and restructuring the Sb cluster to the robust porous ligament‐channel Sb framework. The morphology evolution, (de)sodiation mechanism, and gas evolution are explored by ex situ scanning electron microscope, operando X‐ray diffraction, and operando differential electrochemical mass spectrometry separately. The developed Sb@3D‐Cu anode offers a flexible pathway for constructing 3D‐printed self‐supported electrodes for SIBs. [ABSTRACT FROM AUTHOR]

One often proposed route to improved energy density for lithium‐ion batteries is to use alloy anodes, such as silicon, able to store large amounts of lithium. Mechanical instability caused by the large expansion and contraction associated with (de)lithiation, and hence bad cyclability, has, however, so far hindered progress. As proof‐of‐concept of a remedy, we here present BiSbSe1.5Te1.5, a medium high‐entropy alloy with improved cycling stability for conversion‐alloying (de)lithiation reactions. We attain five to twenty times more stable cycles than previously reported for comparable metal‐Se and ‐Te‐based anodes, with a very good reversible capacity (464 mAh g−1) for up to 110 cycles‐ and this without using any carbonaceous materials to create a composite. Altogether, this highlights how alloy engineering and increased entropy materials can stabilize conversion‐alloying electrodes. [ABSTRACT FROM AUTHOR]

The fast charging/discharging performance of lithium‐ion batteries is closely related to the properties of electrode materials, especially the phase evolution and Li+ diffusion kinetics. The phase evolution and intrinsic properties of an electrode material under different C‐rates can be investigated by applying operando X‐ray diffraction (XRD). In this study, a transmission X‐ray diffractometer is used in operando monitoring the behaviors of NCM811/Graphite pouch cells during charging/discharging at low rate (0.1C) and high rate (2.5C), especially the structure changes, phase evolution, and relaxation of graphite anode. The variations in XRD patterns, as well as and the inconsistency between the state of charge (SOC) of full cells and the SOC of electrodes, are explained based on genetic algorithm and shrinking annuli model. Furthermore, from the perspectives of monitoring and identification of electrode state, structural design of materials and electrodes, and optimization of charging/discharging protocols, practical suggestions for understanding the state and improving the performance of electrodes are proposed. [ABSTRACT FROM AUTHOR]

Self‐discharge, which is associated with energy efficiency loss, is a critical issue that hinders practical applications of rechargeable aluminum batteries (RABs). The self‐discharge properties of two commonly‐used RAB positive electrode materials, namely natural graphite (NG) and expanded graphite (EG), are investigated in this work. EG, which has a wider spacing between graphitic layers and a larger surface area, has a higher self‐discharge rate than that of NG. After 12 h of rest, NG and EG electrodes retain 74% and 63% of their initial capacities, respectively, after charging up to 2.4 V at 0.3 A g−1. Operando X‐ray diffraction, X‐ray photoelectron spectroscopy, and energy‐dispersive X‐ray spectroscopy are employed to study the self‐discharge mechanism. The self‐discharge loss is related to the spontaneous deintercalation of AlCl4− anions from the graphite lattice charge‐compensated by Cl2 gas evolution at the same electrode and can be restored (i.e., no permanent damage is caused to the electrodes) in the next charge‐discharge cycle. It is found that the charging rate and depth of charge also affect the self‐discharge properties. In addition, the self‐discharge rates of NG in 1‐ethyl‐3‐methylimidazolium chloride–AlCl3 and urea–AlCl3 electrolytes are compared. [ABSTRACT FROM AUTHOR]

The utilisation of helium as process gas in laser powder bed fusion limits the generation of Ti-6Al-4V hot and incandescent spatters and enhances their cooling rate. In the present study, operando X-ray diffraction using synchrotron X-rays permits to verify that the cooling rates experienced by the deposited material are not significantly affected by the process gas unlike spatters. Topography measurements of the top printed surface reveal lower roughness of He-produced samples, attributed to the previously observed reduction of spatters with He and thus a reduction of redepositions on the powder bed and printed surfaces. Operando radiography provides with insights on the spatter formation mechanisms namely particle entrainment, agglomeration, melting and spheroidization.Highlights The top surface average roughness of samples produced with He is lower than that of Ar equivalent Deposited Ti-6Al-4V cooling rates during LPBF are not significantly affected by the use of He Grain size and orientation of Ti-6Al-4V is similar when processing under Ar, He, and a mixture of both Operando radiography permits to identify the mechanisms of Ti-6Al-4V spatter formation

The lithiation/delithiation properties of α‐Si3N4 and β‐Si3N4 are compared and the carbon coating effects are examined. Then, β‐Si3N4 at various fractions is used as the secondary phase in a Si anode to modify the electrode properties. The incorporated β‐Si3N4 decreases the crystal size of Si and introduces a new NSiO species at the β‐Si3N4/Si interface. The nitrogen from the milled β‐Si3N4 diffuses into the surface carbon coating during the carbonization heat treatment, forming pyrrolic nitrogen and CNO species. The synergistic effects of combining β‐Si3N4 and Si phases on the specific capacity are confirmed. The operando X‐ray diffraction and X‐ray photoelectron spectroscopy data indicate that β‐Si3N4 is partially consumed during lithiation to form a favorable Li3N species at the electrode. However, the crystalline structure of the hexagonal β‐Si3N4 is preserved after prolonged cycling, which prevents electrode agglomeration and performance deterioration. The carbon‐coated β‐Si3N4/Si composite anode shows specific capacities of 1068 and 480 mAh g−1 at 0.2 and 5 A g−1, respectively. A full cell consisting of the carbon‐coated β‐Si3N4/Si anode and a LiNi0.8Co0.1Mn0.1O2 cathode is constructed and its properties are evaluated. The potential of the proposed composite anodes for Li‐ion battery applications is demonstrated. [ABSTRACT FROM AUTHOR]

In laser powder bed fusion (LPBF), complex components are manufactured layer-by-layer via scanning the cross-sections of a 3D CAD model using a high intensity laser. Throughout this process, the material is exposed to temperature profiles that significantly differ from conventional manufacturing methods, and result in development of a unique and inhomogeneous microstructure and high levels of residual stresses in additively fabricated parts. The large temperature gradients and rapid cooling rates around the moving laser spot, and the overall heterogeneity of the temperature field need to be better understood in order to optimize the process parameters for increased production quality. In this study, operando X-ray diffraction (XRD) was employed to measure and compare temperature histories on the laser path under various processing conditions for Hastelloy X. Finite element thermal simulations were validated based on the acquired XRD data and then used as a supplementary tool to discuss the cooling behaviour and thermal heterogeneities across the geometry. The increase in the deposited energy density was qualitatively linked with higher temperature levels and slower cooling rates during LPBF. The melt-pool lengths showed strong sensitivity to the laser power and little variation with the scanning speed. Furthermore, even for a single set of parameters, large variations in the temperature field within the build were observed such that the cross-section edges located at higher build layers were exposed to markedly higher temperature levels.

Due to the high theoretical specific capacity and low cost of Sn, developing Sn‐based anode materials with long life is the key to their practical applications in lithium‐ion batteries. Herein, novel hierarchically porous NiSn alloys with interconnected ligament‐channel networks are synthesized via a two‐step dealloying strategy, involving corrosion of an Al97.5Ni2Sn0.5 precursor in NaOH, followed by partially etching Ni in HNO3. The architecture of the obtained NiSn‐3 h alloy contains the ligaments with the scale of about 115.2 nm and nanowalls with a thickness of several nanometers on the ligament surface, which can enhance the electron/ion transport kinetics and improve the tolerance to volume variation. The NiSn‐3h electrode exhibits superior Li storage performance in terms of satisfactory rate performance and excellent cycling stability with a reversible capacity of 213.9 mAh g−1 at 1 A g−1 after 1000 cycles. More importantly, the Li storage mechanism of NiSn‐3h is unveiled by operando X‐Ray diffraction, revealing the formation of lithiation products with low crystallinity at the end of discharge. In addition, on‐line differential electrochemical mass spectroscopy is used to detect the gas evolution of the NiSn‐3h electrode during the discharge–charge processes. [ABSTRACT FROM AUTHOR]

The co‐intercalation of solvent molecules along with Na+ into the crystal lattice of electrode materials is an undesired process in sodium batteries. An exception is the intercalation of ether solvated alkali ions into graphite, a fast and highly reversible process. Here, reversible co‐intercalation is shown to also be possible for other layered materials, namely titanium disulfide. Operando X‐ray diffraction and dilatometry are used to demonstrate different storage mechanisms for different electrolyte solvents. Diglyme is found to co‐intercalate into the TiS2 leading to a change in the voltage profile and an increase in the interlayer spacing (≈150%). This behavior is different compared to other solvents, which expand much less during Na storage (24% for tetrahydrofuran [THF] and for a carbonate mixture). For all solvents, specific capacities (2nd cycle) exceed 250 mAh g−1 whereas THF exhibited the best stability after 100 cycles. The solvent co‐intercalation is rationalized by density functional theory and linked to the stability of the solvation shells, which is largest for diglyme. Finally, the TiS2 electrode with diglyme electrolyte is paired with a graphite electrode to realize the first proof‐of‐concept solvent co‐intercalation battery, that is, a battery with two electrodes that both rely on reversible co‐intercalation of solvent molecules. [ABSTRACT FROM AUTHOR]

Magnesium-ion batteries (MIBs) are promising alternatives to lithium-ion batteries due to their safety and high theoretical specific capacity, and the abundance of magnesium reserves. However, their anodes and electrolytes severely restrict the development of MIBs, so alloy-type anodes provide an effective strategy to circumvent the surface passivation issue encountered with Mg metal in conventional electrolytes. Theoretically, a germanium anode can deliver a high specific capacity of 1476 mAh g−1, but hitherto, no experimental reports have described Ge in MIBs. Herein, we experimentally verified that Ge could reversibly react with Mg2+ ions through the design of dual-phase Ge–Bi film electrodes fabricated by magnetron co-sputtering. Notably, a Ge57Bi43 electrode delivered a high specific capacity of 847.5 mAh g−1, owing to the joint alloying reactions of Ge and Bi with Mg, which was much higher than the specific capacity of Bi (around 385 mAh g−1). Moreover, the Ge–Bi anode showed excellent rate performance, good cycling stability, and superior compatibility with conventional electrolytes such as Mg(TFSI)2. More importantly, the Mg storage mechanism of the Ge–Bi anode was unveiled by operando X-ray diffraction, and density functional theory calculations rationalized that the introduction of Bi to form Ge–Bi evidently decreased the defect formation energy and effectively boosted the electrochemical reactivity of Ge with Mg.

Bi-Sb alloys are appealing anode materials for potassium ion batteries (PIBs) but challenged by their enormous volumetric variation during operation. Herein, a facile one-step dealloying protocol was devised and utilized to prepare the Bi-Sb alloys that manifest an exotic bicontinuous hierarchical nanoporous (np) microstructure ideal for volume-change mitigation and K+ transport percolation. The growth mechanism fostering the peculiar morphology of the np-(Bi,Sb) alloys was investigated and clarified via operando X-ray (XRD) and ex-situ scanning electron microscopy (SEM). In particular, the np-Bi6Sb2 electrode, optimized for comprehensive electrochemical performance, achieves decent reversible capacities and a superior lifespan, as benchmarked with the monometallic references and other Bi-Sb alloy electrodes. The (de)potassiation mechanism of the np-(Bi,Sb) alloys was studied by operando XRD and further rationalized by density functional theory (DFT) calculations, whereby a homogeneous (segregation-free) and robust two-step electrochemically-driven phase transformations’ catenation of (Bi,Sb) ↔ K(Bi,Sb)2 ↔ K3(Bi,Sb) was reliably established to substantiate the outstanding reversibility of the np-(Bi,Sb) anodes in PIBs.

The alloy-type anodes in lithium ion batteries (LIBs) often suffer from the pulverization/failure of active materials caused by the drastic volume variations during cycling. Liquid Ga-based materials with low melting points and intrinsic self-healing feature are one of the best candidates for enhancing the Li storage property. Herein, a liquid eutectic GaSn (EGaSn) electrode was fabricated based upon a simple painting method and directly used as the anode for LIBs at room temperature. Furthermore, the wettability of liquid EGaSn alloy on the current collector in the Ar atmosphere was greatly improved through the construction of Ag 3 Ga modified layer on the stainless steel mesh (ssm) surface. And the Ag 3 Ga-EGaSn anode displays the much better Li storage performance (specific capacity, rate performance and cycling stability) than the untreated EGaSn anode. More importantly, operando XRD measurement clearly clarified the electrochemical reaction mechanism of Ag 3 Ga-EGaSn in LIBs. This work indicates a potential strategy to directly use liquid Ga-based electrode with regulated wettability for LIBs. [Display omitted] • Room-temperature liquid EGaSn anodes were simply prepared for LIBs. • The wettability of liquid EGaSn on current collectors was significantly improved. • The Ag 3 Ga-EGaSn shows greatly enhanced cycling stability and rate performance. • Reaction mechanism of liquid Ag 3 Ga-EGaSn anodes in LIBs were unveiled. [ABSTRACT FROM AUTHOR]

Alloy-type anodes have attracted extensive attention in magnesium-ion batteries (MIBs) due to their low reaction potentials and high theoretical specific capacities. However, the kinetically sluggish Mg insertion/extraction and diffusion in electrode materials, as well as the huge volume changes resulting in the capacity decay limit their further development. Herein, a series of porous-Bi (P-Bi x) anodes are fabricated through a facile dealloying strategy based on the Sn 100-x Bi x (x = 1, 5, 10, 43, at.%) precursor alloys. Among them, the P–Bi 10 anode delivers a high discharge specific capacity (376.0 mAh g−1 at 500 mA g−1), greatly improved rate capability (363.3 mAh g−1 at 1000 mA g−1) and good cycling stability even at 2000 mA g−1 (104.0 mAh g−1 after 1000 cycles). Furthermore, operando X-ray diffraction (XRD) is performed to unveil the magnesiation/demagnesiation mechanisms of the P–Bi 5 and P–Bi 10 anodes, indicating a simple two-phase reaction process. Additionally, the P–Bi 10 anode displays good compatibility with conventional Mg salt electrolytes such as Mg(TFSI) 2. Our findings could provide useful information on design of high-performance alloy-type anode materials for MIBs. [Display omitted] • P-Bi x anodes were facilely fabricated through dealloying of Sn 100-x Bi x precursors. • The P–Bi 10 shows superior Mg storage performance and compatibility with Mg(TFSI) 2. • Operando XRD unveiled a simple two-phase reaction between Bi and Mg 3 Bi 2. [ABSTRACT FROM AUTHOR]

While lithium‐sulfur batteries theoretically have both high gravimetric specific energy and volumetric energy density, only its specific energy has been experimentally demonstrated to surpass that of the state‐of‐the‐art lithium‐ion systems at cell level. One major reason for the unrealized energy density is the low capacity density of the highly porous sulfur/carbon composite as the positive electrode. In this work, mechanical compression at elevated temperature is demonstrated to be an effective method to increase the capacity density of the electrode by at least 90 % and moreover extends its cycle life. Distinct impacts of compression on the resistance profiles of electrodes with different thickness are investigated by tortuosity factors derived from both electrochemical impedance spectroscopy, X‐ray computed tomography and kinetic analysis based on operando X‐ray diffraction. The results highlights the importance of a homogeneous electrode structure highlight lithium‐sulfur system. [ABSTRACT FROM AUTHOR]

• Mg-Sn and Mg-Pb intermetallics are prepared by high-energy ball-milling. • Tuning the milling time allows to obtain cubic Mg 2 Sn and Mg 2 Pb or non-cubic Mg ∼2 Sn and Mg ∼2 Pb polymorphs. • Intermetallics are investigated as active material in Mg-batteries by operando X-ray diffraction. • The alloying process favors the formation of the cubic alloy for both tin and lead. Different polymorphs of Mg-Sn and Mg-Pb intermetallic compounds were prepared by high-energy mechanical alloying and then investigated as active material in magnesium batteries. Beside thermodynamically stable Mg 2 Sn and Mg 2 Pb crystallizing in the anti-fluorite structure, other polymorphs Mg ∼2 Sn and Mg ∼2 Pb were prepared by increasing the ball-milling time. The first dealloying process is almost complete only for the cubic polymorphs, then similar capacities are observed during the subsequent alloying and dealloying sequences. Thanks to operando X-ray diffraction, the electrochemical mechanism is revealed and shows that the cubic polymorphs Mg 2 Sn and Mg 2 Pb tend to preferentially form during the alloying whatever the pristine intermetallic. Weak traces of Mg ∼2 Sn and Mg ∼2 Pb are observed during the alloying, suggesting that these polymorphs act as a by-product and/or an intermediate phases of the electrochemical process. Finally, the compatibility of cubic Mg 2 Sn and Mg 2 Pb with Mg(TFSI) 2 -based electrolyte is confirmed in full cell vs. a positive electrode based on the Chevrel phase Mo 6 S 8 , although limited performance is achieved. This fundamental work provides new insights in the behavior of alloy-type negative electrodes for magnesium-ion batteries. [ABSTRACT FROM AUTHOR]

The substantial manufacturing of lithium-ion batteries (LIBs) requires sustainable, circular, and decarbonized recycling strategies. While efforts are concentrated on extracting valuable metals from cathodes using intricate chemical process, the direct, efficient cathode regeneration remains a technological challenge. More urgently, the battery supply chain also requires the value-added exploitation of retired anodes. Here, a "closed-loop" approach is proposed to upcycle spent graphite into the prelithiation catalyst, namely the fewer-layer graphene flakes (FGF), upon the exquisite tuning of interlayer spacing and defect concentration. Since the catalytic FGF mitigates the delithiation energy barrier from calcinated Li 5 FeO 4 nanocrystalline, the composite layer of which cast on the polyolefin substrate thus enables a customized prelithiation capability (98% Li + utilization) for the retired LiFePO 4 recovery. Furthermore, the hydrophobic polymeric modification guarantees the moisture tolerance of Li 5 FeO 4 agents, aligning with commercial battery manufacturing standards. The separator strategy well regulates the interfacial chemistry in the anode-free pouch cell (LiFePO 4 ||Cu), the prototype of which balances the robust cyclability, energy density up to 386.6 Wh kg -1 as well as the extreme power output of 1159.8 W kg -1 . This study not only fulfills the sustainable supply chain with graphite upcycling, but also establishes a generic, viable protocol for the anode-free cell prototyping., (© 2024 Wiley‐VCH GmbH.)

Na 3 V 2 (PO 4 ) 3 (NVP) has gained a lot of attention due to its remarkable properties, such as its robust crystal structure, cycle life, rate capabilities, and so on. Nevertheless, NVP undergoes a substantial decrease in its rate capability at low temperatures, which limits its practical applications. In this study, the performance of NVP at low, room, and high temperatures during cycling is thoroughly investigated using synchrotron operando X-ray diffraction. The (de)insertion of two sodium ions from Na 3 V 2 (PO 4 ) 3 to Na 1 V 2 (PO 4 ) 3 appeared to occur via two intermediate phases (Na 2 V 2 (PO 4 ) 3 and Na 1.64 V 2 (PO 4 ) 3 ). The Na 1.64 V 2 (PO 4 ) 3 phase which is observed for the first-time during operando XRD measurements of NVP, exhibited limited stability at high temperatures. The increase in the quantity of these intermediate phases from high to low temperatures, especially at high C-rates, could be anticipated to be one of the contributing factors of poor rate capabilities of NVP at low temperatures. This study encourages the exploration of suitable strategies to enhance the performance of NVP at low temperatures and high C-rates.

Alloy-type anodes used in magnesium ion batteries (MIBs) have garnered significant attention in light of their substantial theoretical specific capacities and possible matchability with conventional electrolytes. However, the major challenges for alloy-type anodes are the sluggish transport kinetics as well as severe volume variations during the discharge/charge processes. Herein, we present a strategy for phase-structure modulation to fabricate a self-supporting In-Bi film through straightforward magnetron sputtering. In comparison to the single-phase In and Bi electrodes, the biphase InBi/Bi electrode displays markedly enhanced rate and cycling performance, with the discharge capacities of 303.1/292.6 mAh g -1 after 550/500 cycles at 200/2000 mA g -1 , respectively. The exceptional Mg storage capability of the sputtered InBi/Bi electrode could be ascribed to the favorable two-phase configuration and increased phase boundaries, effectively accommodating volume expansion and accelerating Mg 2+ ion transport. More importantly, the (de)magnesiation mechanism of InBi/Bi for MIBs was elucidated through operando X-ray diffraction.

Adding silicon (Si) to graphite (Gr) anodes is an effective approach for boosting the energy density of lithium-ion batteries, but it also triggers mechanical instability due to Si volume changes upon (de)lithiation reactions. In this work, component-specific (de)lithiation dynamics on Si-rich (30 and 70 wt.% Si) SiGr anodes at various charge/discharge C-rates are unveiled and compared to a graphite-only electrode (100Gr) via operando synchrotron X-ray diffraction coupled with differential capacity plots analysis. Results show preferential lithiation of amorphous Si above ≈200 mV and competing lithiation of Gr, amorphous Si, and crystalline Si below ≈200 mV. Discharge proceeds via sequential delithiation of Gr and amorphous lithium silicide. Si shifts the interconversion potentials of graphite intercalation compounds, lowering the Gr state of charge compared to 100Gr. In the 30% Si electrode, crystalline Si amorphization at potentials <110 mV is found to be kinetically hindered at C-rates higher than C/5, which can be key for enhancing the cycling stability of SiGr anodes. The 70% Si electrode exhibits restricted lithium diffusion in Gr, full Si amorphization, and Li 15 Si 4 formation. These findings related to the potential- and current-dependent dynamic changes on SiGr blends are crucial for designing stable high energy density SiGr anodes., (© 2024 The Author(s). Small published by Wiley‐VCH GmbH.)

Substantial improvements in cycle life, rate performance, accessible voltage, and reversible capacity are required to realize the promise of Li-ion batteries in full measure. Here, we have examined insertion electrodes of the same composition (V2O5) prepared according to the same electrode specifications and comprising particles with similar dimensions and geometries that differ only in terms of their atomic connectivity and crystal structure, specifically two-dimensional (2D) layered α-V2O5 that crystallizes in an orthorhombic space group and one-dimensional (1D) tunnel-structured ζ-V2O5 crystallized in a monoclinic space group. By using particles of similar dimensions, we have disentangled the role of specific structural motifs and atomistic diffusion pathways in affecting electrochemical performance by mapping the dynamical evolution of lithiation-induced structural modifications using ex situ scanning transmission X-ray microscopy, operando synchrotron X-ray diffraction measurements, and phase-field modeling. We find the operation of sharply divergent mechanisms to accommodate increasing concentrations of Li-ions: a series of distortive phase transformations that result in puckering and expansion of interlayer spacing in layered α-V2O5, as compared with cation reordering along interstitial sites in tunnel-structured ζ-V2O5. By alleviating distortive phase transformations, the ζ-V2O5 cathode shows reduced voltage hysteresis, increased Li-ion diffusivity, alleviation of stress gradients, and improved capacity retention. The findings demonstrate that alternative lithiation mechanisms can be accessed in metastable compounds by dint of their reconfigured atomic connectivity and can unlock substantially improved electrochemical performance not accessible in the thermodynamically stable phase. [ABSTRACT FROM AUTHOR]

Substantial improvements in cycle life, rate performance, accessible voltage, and reversible capacity are required to realize the promise of Li-ion batteries in full measure. Here, we have examined insertion electrodes of the same composition (V2O5) prepared according to the same electrode specifications and comprising particles with similar dimensions and geometries that differ only in terms of their atomic connectivity and crystal structure, specifically two-dimensional (2D) layered α-V2O5 that crystallizes in an orthorhombic space group and one-dimensional (1D) tunnel-structured ζ-V2O5 crystallized in a monoclinic space group. By using particles of similar dimensions, we have disentangled the role of specific structural motifs and atomistic diffusion pathways in affecting electrochemical performance by mapping the dynamical evolution of lithiation-induced structural modifications using ex situ scanning transmission X-ray microscopy, operando synchrotron X-ray diffraction measurements, and phase-field modeling. We find the operation of sharply divergent mechanisms to accommodate increasing concentrations of Li-ions: a series of distortive phase transformations that result in puckering and expansion of interlayer spacing in layered α-V2O5, as compared with cation reordering along interstitial sites in tunnel-structured ζ-V2O5. By alleviating distortive phase transformations, the ζ-V2O5 cathode shows reduced voltage hysteresis, increased Li-ion diffusivity, alleviation of stress gradients, and improved capacity retention. The findings demonstrate that alternative lithiation mechanisms can be accessed in metastable compounds by dint of their reconfigured atomic connectivity and can unlock substantially improved electrochemical performance not accessible in the thermodynamically stable phase. [ABSTRACT FROM AUTHOR]

Designing high‐performance electrocatalysts for boosting aprotic electrochemistry is of vital importance to drive longevous Li–S batteries. Nevertheless, investigations on probing the electrocatalytic endurance and protecting the catalyst activity yet remain elusive. Here, a ternary graphene‐TiO2/TiN (G‐TiO2/TiN) heterostructure affording conformal graphene chainmail is presented as an efficient and robust electrocatalyst for expediting sulfur redox kinetics. The G‐TiO2/TiN heterostructure synergizes adsorptive TiO2, catalytic TiN, and conductive graphene armor, thus enabling abundant anchoring points for polysulfides and sustained active sites to allow smooth bi‐directional electrocatalysis. Encouragingly, in situ crafted graphene chainmail ensures favorable protection of inner TiO2/TiN to retain their catalytic robustness towards durable sulfur chemistry. As expected, sulfur cathodes mediated by ternary G‐TiO2/TiN harvest an impressive rate capability (698.8 mAh g−1 at 5.0 C), favorable cycling stability (a low decay of 0.054% per cycle within 1000 cycles), and satisfactory areal capacity under elevated loading (delivering 8.63 mAh cm−2 at a sulfur loading of 10.4 mg cm−2). The ternary heterostructure design offers an in‐depth insight into the electrocatalyst manipulation and protection toward long lifespan Li–S batteries. [ABSTRACT FROM AUTHOR]

The layered V2O5 cathode exhibits appealing features of multiple electron redox processes and versatile cation‐storage capacities. However, the huge volume respiration induces structural collapse and limits its commercial‐scale deployment. Herein, a scalable water‐bath strategy is developed to tailor the (001) spacing of the bulk V2O5 from the original 4.37 Å to its triple value (14.2 Å). The intercalated polyaniline (PANI) molecules act as pillars in the V2O5 interlayer, thus affording the abundant storage sites and enhanced cation diffusivities of Li+, Na+, or hydrated Zn2+. Upon various cations (de‐)intercalation, transmission‐mode operando X‐ray diffraction is employed to document the zero‐strain behavior of the PANI‐intercalated V2O5. This scalable intercalation‐polymerization strategy, coupled with the compatibility study of the ionic radius and the c‐lattice for the layered structure, enables the rational engineering of the intercalation‐type cathodes toward facile reaction kinetics. [ABSTRACT FROM AUTHOR]

• A set of highly complementary operando techniques (Advanced operando X-ray absorption spectroscopy (XAS), X-ray diffraction (XRD) and Raman spectroscopy) sensitive to potential-dependent alteration of highly porous oxidic precursor materials used for the electrochemical reduction of CO 2 into value-added products such as hydrocarbons and higher alcohols. • This complementary and holistic approach of 'bulk'- and surface-sensitive techniques demonstrates that the electro-reduction of porous Cu x O foams into metallic Cu is completed before CO 2 RR products formation sets in. • There are substantial differences in the particular potential dependence of the oxide reduction when comparing the 'bulk' with the respective 'surface' processes. • It is valuable in comparison with the bulk-sensitive XAS and XRD techniques which both indicate oxide-metal transitions that are 'delayed' on the potential scale with respect to what is observed in the surface-sensitive Raman spectroscopy. Copper oxides have recently emerged as promising precursor catalyst materials demonstrating enhanced reactivity and selectivity towards C2 and C3 products like ethylene, ethanol, and n-propanol generated from the direct electro-reduction reaction of CO 2 (denoted as CO 2 RR). Advanced operando X-ray absorption spectroscopy (XAS), X-ray diffraction (XRD) and Raman spectroscopy were employed to probe the potential-dependent changes of the chemical states of Cu species in the Cu oxide foams (referred to as Cu x O) before and during the CO 2 RR. This complementary and holistic approach of 'bulk'- and surface-sensitive techniques demonstrates that the electro-reduction of Cu x O foams into metallic Cu is completed before hydrocarbon (e.g., ethylene, ethane) and alcohol (e.g., ethanol, n-propanol) formation sets in. There are, however, substantial differences in the potential dependence of the oxide reduction when comparing the 'bulk' with the respective 'surface' processes. Only in the very initial stage of the CO 2 RR, the reduction of the Cu oxide precursor species is temporarily superimposed on the production of CO and H 2. Complementary identical location (IL) SEM analysis of the Cu x O foams prior to and after the CO 2 RR reveals a significant alteration in the surface morphology caused by the appearance of smaller Cu nanoparticles formed by the reduction process of Cu x O species. [ABSTRACT FROM AUTHOR]

Ball‐milled Li3VO4 (LVO) offers higher practical specific charge values and better cycle stability than the pristine, μm‐scale material due to improved electronic conductivity within the electrode. Although the theoretical specific charge of LVO is estimated to be 592 mAh g−1, its practical reversible specific charge retains 220 mAh g−1 (1.12 Li+) on long‐term cycling. At a very low rate of C/200 (=3 mA g−1), ball‐milled Li3VO4‐based anodes accomplish an almost full lithiation state of x=2.97 Li+ in Li3+xVO4. At the end of the first delithiation, the recovered LVO phase is able to only reversibly (de)lithiate about 1.8 Li+ in the following cycles. A careful investigation of the charge storage mechanism of LVO by operando X‐ray diffraction revealed that the irreversible specific charge "loss" in the first cycle is mainly associated with an irreversible structural transformation via an intermediate phase on the first lithiation of LVO that leads to clear mechanistic differences in the reaction pathways between the first lithiation and delithiation. [ABSTRACT FROM AUTHOR]

Abstract Potassium‐ion batteries (KIBs) are one of the most appealing alternatives to lithium‐ion batteries, particularly attractive in large‐scale energy storage devices considering the more sufficient and lower cost supply of potassium resources in comparison with lithium. To achieve more competitive KIBs, it is necessary to search for anode materials with a high performance. Herein, the bimetallic oxide Sb2MoO6, with the presence of reduced graphene oxide, is reported as a high‐performance anode material for KIBs in this study, achieving discharge capacities as high as 402 mAh g−1 at 100 mA g−1 and 381 mAh g−1 at 200 mA g−1, and reserving a capacity of 247 mAh g−1 after 100 cycles at a current density of 500 mA g−1. Meanwhile, the potassiation/depotassiation mechanism of this material is probed in‐depth through the electrochemical characterization, operando X‐ray diffraction, transmission electron microscope, and density functional theory calculation, successfully unraveling the nature of the high‐performance anode and the functions of Sb and Mo in Sb2MoO6. More importantly, the phase development and bond breaking sequence of Sb2MoO6 are successfully identified, which is meaningful for the fundamental study of metal‐oxide based electrode materials for KIBs.

The cycling performance of LiCoPO4 (LCP) as a high voltage positive electrode material in lithium‐ion batteries is enhanced by partial magnesium substitution for cobalt. Structural investigation of magnesium‐doped LCP using combined powder neutron and X‐ray diffraction reveals a decrease in anti‐site defects. In addition, the reduced unit cell volume variation during the charging process is observed by operando X‐ray diffraction measurements. Characterisation of the surface shows the presence of a Mg‐rich layer on the surface that might prevent detrimental reactions with the electrolyte. The combined beneficial effects of magnesium doping in LCP result in improved capacity retention. [ABSTRACT FROM AUTHOR]

Structural variation of LiMn1.5Ni0.5O4 spinel cathode during the Li+ extraction/insertion reaction was studied using operando X-ray diffraction. It was found that the reaction in the voltage range from 3.5 to 4.9 V consisted of two consecutive two-phase reactions, where three spinel phases of LiMn1.5Ni0.5O4, Li0.5Mn1.5Ni0.5O4 and Mn1.5Ni0.5O4 were identified and the lattice volume change in the whole reaction was evaluated as 6%. The reactions were symmetric and reversible under low-current conditions, but some asymmetries were detected during high current operation. Furthermore, a two-phase reaction between cubic and tetragonal phases was observed in the low-voltage reaction at 2.1–3.5 V, where the lattice volume change was approximately 4.9%. The rate-determining step was discussed based on these operando results. [ABSTRACT FROM AUTHOR]

Although lithium intercalation into vanadium (V) oxide was studied over decades, exact compositional stability limits for γ‐LixV2O5 phase, which can be reversibly lithiated and delithiated, are still not clear. Using operando and ex‐situ synchrotron X‐ray diffraction, we traced phase composition of the V2O5 electrodes containing reduced graphene oxide during its lithiation and delithiation. We found that coating of micron‐sized V2O5 particles by reduced graphene oxide yields the material providing electrochemical capacity of more than 300 mA h g−1 manifesting insertion of more than 2 lithium ions per mole of V2O5 as confirmed by ICP MS analysis of the electrodes. The obtained electrode material can be sustainably cycled with capacity retaining at ca. 220 mA h g−1 at 500 mA g−1 current over 200 cycles. [ABSTRACT FROM AUTHOR]

The sputtered PbSn film electrode exhibits significant Mg storage activity and a two-step alloy process towards Mg storage. [Display omitted] • Flexible, self-supporting PbSn film was fabricated by magnetron co-sputtering. • Biphase PbSn anode exhibits more stable Mg storage properties. • The Mg storage mechanism of PbSn was clarified by combining ex situ and operando XRD. Alloy-type anodes in magnesium ion batteries (MIBs) have sparked considerable interest due to their notable characteristics, including high theoretical specific capacities, low reaction potentials and compatibility with conventional electrolytes, but their development still needs to be further expanded and explored. Herein, we fabricated the self-supporting biphase PbSn alloy films using a one-step magnetron co-sputtering technique. As anodes for MIBs, the PbSn alloy electrode delivers more stable capacity values and better capacity recoverability than those of pure Pb electrode, which could be associated with the improvement of structural/performance stability derived from the biphase constitution. Most importantly, the Mg storage mechanism of PbSn anodes was distinctly revealed by integrating both ex situ and operando X-ray diffraction methods, elucidating a two-step alloying reaction. [ABSTRACT FROM AUTHOR]

Fast-charging Li-ion batteries are technologically important for the electrification of transportation and the implementation of grid-scale storage, and additional fundamental understanding of high-rate insertion reactions is necessary to overcome current rate limitations. In particular, phase transformations during ion insertion have been hypothesized to slow charging. Nanoscale materials with modified transformation behavior often show much faster kinetics, but the mechanism for these changes and their specific contribution to fast-charging remain poorly understood. In this work, we combine operando synchrotron X-ray diffraction with electrochemical kinetics analyses to illustrate how nanoscale crystal size leads to suppression of first-order insertion-induced phase transitions and their negative kinetic effects in MoO 2 , a tunnel structure host material. In electrodes made with micrometer-scale particles, large first-order phase transitions during cycling lower capacity, slow charge storage, and decrease cycle life. In medium-sized nanoporous MoO 2 , the phase transitions remain first-order, but show a considerably smaller miscibility gap and shorter two-phase coexistence region. Finally, in small MoO 2 nanocrystals, the structural evolution during lithiation becomes entirely single-phase/solid-solution. For all nanostructured materials, the changes to the phase transition dynamics lead to dramatic improvements in capacity, rate capability, and cycle life. This work highlights the continuous evolution from a kinetically hindered battery material in bulk form to a fast-charging, pseudocapacitive material through nanoscale size effects. As such, it provides key insight into how phase transitions can be effectively controlled using nanoscale size and emphasizes the importance of these structural dynamics to the fast rate capability observed in nanostructured electrode materials.

Abstract Developing advanced electrode materials and understanding their reaction mechanisms are two crucial issues for development of high-performance sodium ion batteries (SIBs). Herein, we synthesized a bimetallic single-phase nanoporous (NP) SnSb alloy with a bicontinuous ligament-channel structure through elaborate design of ternary Mg-Sn-Sb precursor and chemical dealloying. As an anode for SIBs, the NP-SnSb alloy delivers high specific capacity, excellent cycling stability (506.6 mAh g−1 after 100 cycles at 0.2 A g−1; 457.9 mAh g−1 after 150 cycles at 1.0 A g−1) and superior rate capability (458.2 mAh g−1 at 10 A g−1). Moreover, the Na 3 V 2 (PO 4) 3 (cathode)/NP-SnSb (anode) full cell also exhibits outstanding electrochemical performance (cycling stability and rate capability). The unique nanoporous structure (with ligaments of 38.9 ± 7.3 nm), the alloying effect and the synergetic reaction of Sn/Sb account for the eminent electrochemical properties of NP-SnSb. Most importantly, the Na storage mechanism of SnSb alloy was revealed using operando X-ray diffraction and density functional theory calculations. Rather than separate reactions of Sn and Sb, the reaction of SnSb alloy proceeds through a synergetic sodiation/desodiation process via the mechanism: SnSb (crystalline) ↔ Na(Sn,Sb) (amorphous) ↔ Na 9 (Sn,Sb) 4 (amorphous/low-crystalline) ↔ Na 15 (Sn,Sb) 4 (crystalline). Graphical abstract fx1 Highlights • Nanoporous SnSb (NP-SnSb) alloy was fabricated by a facile dealloying strategy. • NP-SnSb anode exhibits good cycling stability and superior rate capability. • A unique Na storage mechanism of SnSb anode was revealed by operando XRD and DFT. • Ex-situ XRD verified the metastable feature of sodiated products of SnSb. [ABSTRACT FROM AUTHOR]

A methodology that allows the quantification of structural changes in functional thin films during the application of external electrical field is reported. The originality of this method is the development of a set-up using a laboratory X-ray source since most of previous Operando studies have used synchrotron radiations. Several technical challenges have been addressed: the (i) optimization of the electrical contact and the sample geometry within the lab-source goniometers, (ii) evaluation of any X-ray dose effect on the Metal/Insulator/Metal structure to prevent eventual charge accumulation at the electrode interfaces and (iii) the quantification of the effect of the time-delay, needed for X-ray measurement, on domain switching. The validity of our method has been demonstrated on a prototypic sol-gel lead zirconate titanate (PZT) thin film where the polarization and structural changes have been simultaneously measured. The evolution of ferroelastic domains as a function of external electric field has been quantified and two different effects have been successfully separated: (a) the cell extension and (b) domain wall motion described as the switching between a and c tetragonal domains. [ABSTRACT FROM AUTHOR]

We investigated rechargeable aluminum (Al) batteries composed of an Al negative electrode, a graphite positive electrode, and an ionic liquid (IL) electrolyte at temperatures down to −40 °C. The reversible battery discharge capacity at low temperatures could be superior to that at room temperature. In situ/operando electrochemical and synchrotron X-ray diffraction experiments combined with theoretical modeling revealed stable AlCl4−/graphite intercalation up to stage 3 at low temperatures, whereas intercalation was reversible up to stage 4 at room temperature (RT). The higher-degree anion/graphite intercalation at low temperatures affords rechargeable Al battery with higher discharge voltage (up to 2.5 V, a record for Al battery) and energy density. A remarkable cycle life of >20,000 cycles at a rate of 6C (10 minutes charge time) was achievable for Al battery operating at low temperatures, corresponding to a >50-year battery life if charged/discharged once daily. [ABSTRACT FROM AUTHOR]