Anode-free aqueous zinc metal batteries (AZMBs) offer significant potential for energy storage due to their low cost and environmental benefits. Ti₃C₂T_x MXene provides several advantages over traditional metallic current collectors like Cu and Ti, including better Zn plating affinity, lightweight, and flexibility. However, self-freestanding MXene current collectors in AZMBs remain underexplored, likely due to challenges with Zn deposition reversibility. This study investigates the combination of a Ti₃C₂T_x self-freestanding film with advanced electrolyte engineering, specifically examining the effects of Li-salt and propylene carbonate (PC) as additives on Zn plating reversibility. While using Li⁺ ions as an additive alone facilitates uniform Zn deposition on bulk metals through the electrostatic shielding effect, the addition of Li-salt negatively impacts Zn plating uniformity on Ti₃C₂T_x. Meanwhile, using PC additive alone forms an organic SEI layer on Ti₃C₂T_x and causes Zn agglomeration. The use of both additives together results in a ZnF₂-containing hybrid SEI layer with improved interfacial kinetics, promoting more uniform Zn deposition. This approach achieves an average Coulombic efficiency (CE) of 96.8% over 150 cycles (a maximum CE of 97.8%). The study highlights the strategic difference in electrolyte design, emphasizing the need for tailored approaches to optimize Zn deposition on MXenes, contrasting with traditional metallic current collectors.

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Hybrid solid electrolytes (HSEs) leverage the benefits of their organic and inorganic components, yet optimizing ion transport and component compatibility requires a deeper understanding of their intricate ion transport mechanisms. Here, macroscopic charge transport is correlated with local lithium (Li)-ion diffusivity in HSEs, using poly(ethylene oxide) (PEO) as matrix and Li6PS5Cl as filler. Solvent- and dry-processing methods were evaluated for their morphological impact on Li-ion transport. Through multiscale solid-state nuclear magnetic resonance analysis, we reveal that the filler enhances local Li-ion diffusivity within the slow polymer segmental dynamics. Phase transitions indicate inhibited crystallization in HSEs, with reduced Li-ion diffusion barriers attributed to enhanced segmental motion and conductive polymer conformations. Relaxometry measurements identify a mobile component unique to the hybrid system at low temperatures, indicating Li-ion transport along polymer-filler interfaces. Comparative analysis shows solvent-processed HSEs exhibit better morphological uniformity and enhanced compatibility with Li-metal anodes via an inorganic-rich solid electrolyte interphase.@en

Rechargeable Li||I2 batteries based on liquid organic electrolytes suffer from pronounced polyiodides shuttling and safety concerns, which can be potentially tackled by the use of solid-state electrolytes. However, current all-solid-state Li||I2 batteries only demonstrate limited capacity based on a two-electron I−/I2 polyiodides chemistry at elevated temperatures, preventing them from rivaling state-of-the-art lithium-ion batteries. Herein, we report a fast, stable and high-capacity four-electron solid-conversion I−/I2/I+ chemistry in all-solid-state Li||I2 batteries at room temperature. Through the strategic use of a highly conductive, chlorine-rich solid electrolyte Li4.2InCl7.2 as the catholyte, we effectively activate the I2/I+ redox couple. This activation is achieved through a robust I-Cl interhalogen interaction between I2 and the catholyte, facilitated by an interface-mediated heterogeneous oxidation mechanism. Moreover, apart from serving as Li-ion conduction pathway, the Li4.2InCl7.2 catholyte is demonstrated to show a reversible redox behavior and contribute to the electrode capacity without compromising its conductivity. Based on the I−/I2/I+ four-electron chemistry, the as-designed all-solid-state Li||I2 batteries deliver a high specific capacity of 449 mAh g-1 at 44 mA g-1 based on I2 mass and an impressive cycling stability over 600 cycles with a capacity retention of 91% at 440 mA g-1 and at 25 °C.@en

Electrode–electrolyte interphases are critical determinants of the reversibility and longevity of lithium (Li)-metal batteries (LMBs). However, upon cycling, the inherently delicate interphases, formed from electrolyte decomposition, become vulnerable to chemomechanical degradation and corrosion, resulting in rapid capacity loss and thus short battery life. Here, we present a comprehensive analysis of the complex interplay between the thermodynamic and kinetic properties of interphases on Li-metal anodes, providing insights into interphase design to address these challenges. Direct measurements of ion-transport kinetics across various electrolyte chemistries reveal that interphases with high Li-ion mobility are essential for achieving dense Li deposits. Conversely, sluggish ion transport generates high-surface-area Li deposits that induce Li random stripping and the accumulation of isolated Li deposits. Surprisingly, interphases that support long cycle life do not necessarily require the formation of dense Li deposits but must avoid possible electrochemical/chemical reactions between the Li-metal deposits and electrolytes’ components. By that, in some specific electrolyte systems, isolated Li deposits can recover and electrically rejoin the active Li anodes’ mass. These findings challenge conventional understanding and establish new principles for designing durable LMBs, demonstrating that even with commercial carbonate-based electrolytes, LiNi0.8Co0.1Mn0.1O2||Cu cells can achieve high reversibility.@en

Lithium argyrodite thiophosphate superionic conductors are being explored as promising solid electrolytes for all-solid-state batteries, primarily due to their high ionic conductivity and ease of processing. Yet, these electrolytes present challenges such as chemical instability in humid conditions and incompatibility with cathode materials. Although some lithium argyrodites show improved air stability, their ionic conductivity deteriorates below the practically required value. Herein, based on hard soft acid base theory, a new family of lithium argyrodite, as solid solution Li6−xAsS5−xBr1+x (for 0.0 ≤ x ≤ 0.6), has been proposed to address these issues. Through a combination of neutron diffraction, NMR spectroscopy, and electrochemical impedance spectroscopy, it has been determined that the partial substitution of S2− by Br− weakens interactions within the Li+ “cage”, facilitating long lithium-ion movement throughout the structure. An additional T4 Li+ site is identified, offering a lower energy barrier for inter-cage jumps. Consequently, the Li5.5AsS4.5Br1.5 member of the composition series exhibits a higher Li-ion diffusivity resulting in a remarkable ionic conductivity of 15.4 mS cm−1. Compared with lithium thiophosphates, the Li5.5AsS4.5Br1.5 also shows excellent air stability. This research opens a new avenue for developing air-stable sulfide solid electrolytes with high ionic conductivity necessitated for practical application in solid-state batteries.@en

By varying the bromine content and cooling method, we are able to induce site disorder in the Li_6-xPS_5-xBr_1+x (x = 0, 0.3, 0.5) system via two routes, allowing us to disentangle the impact of site disorder and chemical composition on conductivity. Through solid-state nuclear magnetic resonance (NMR), we can explore the chemical environment as well as short-range lithium-ion dynamics and compare these to results obtained from neutron diffraction and electrochemical impedance spectroscopy (EIS). We find that the cooling method has a profound effect on the ⁷Li and ³¹P environment that cannot be explained through 4d site disorder alone. The configurational entropy (S_conf) is used as a more complete descriptor of structural disorder and linked to distortions in both the phosphorus and lithium environment. These distortions are correlated to increased intercage movement through ⁷Li T₁ spin-lattice relaxation (SLR) NMR. Further analysis of the prefactors obtained from SLR NMR and EIS allows us to obtain the migrational entropy (ΔS_m). For short-range SLR movement, the ΔS_m correlates well with S_conf, implying that increased intercage movement is related to distortion of the lithium cages as well as a decrease of the intercage distance. Comparison to EIS shows that an increase in short-range movement translates into increased long-range movement in a straightforward manner for slow-cooled samples. However, for quench-cooled samples, this correlation is lost. Lattice softness and phonon-ion interactions are suggested to play an important role in long-range conduction which only becomes apparent when chemical composition and disorder are disentangled. This work shows that by altering one synthesis step, the relationship between site-occupancy-based descriptors (site disorder or S_conf) and lithium dynamics is changed profoundly. Furthermore, it shows that chemical composition and descriptors of site disorder cannot be seen as one and the same, as both play a role that changes with the length scale probed. Finally, it challenges the implicit assumption that increased short-range diffusivity automatically results in increased long-range diffusivity.

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Achieving both high redox activity and rapid ion transport is a critical and pervasive challenge in electrochemical energy storage applications. This challenge is significantly magnified when using large-sized charge carriers, such as the sustainable ammonium ion (NH₄⁺). A self-assembled MXene/n-type conjugated polyelectrolyte (CPE) superlattice-like heterostructure that enables redox-active, fast, and reversible ammonium storage is reported. The superlattice-like structure persists as the CPE:MXene ratio increases, accompanied by a linear increase in the interlayer spacing of MXene flakes and a greater overlap of CPEs. Concurrently, the redox activity per unit of CPE unexpectedly intensifies, a phenomenon that can be explained by the enhanced de-solvation of ammonium due to the increased volume of 3 Å-sized pores, as indicated by molecular dynamic simulations. At the maximum CPE mass loading (MXene:CPE ratio = 2:1), the heterostructure demonstrates the strongest polymeric redox activity with a high ammonium storage capacity of 126.1 C g⁻¹ and a superior rate capability at 10 A g⁻¹. This work unveils an effective strategy for designing tunable superlattice-like heterostructures to enhance redox activity and achieve rapid charge transfer for ions beyond lithium.

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Lithium metal with its high theoretical capacity and low negative potential is considered one of the most important candidates to raise the energy density of all-solid-state batteries. However, lithium filament growth and its induced solid electrolyte decomposition pose severe challenges to realize a long cycle life. Here, dendrite growth in solid-state Li metal batteries is alleviated by introducing a high dielectric material, barium titanate, as a filler that removes the electric field gradients that catalyze dendrite formation. In symmetrical Li-metal cells, this results in a very small over-potential of only 48 mV at a relatively high current density of 1 mA cm⁻², when cycling a capacity of 2 mA h cm⁻² during 1700 h. The high dielectric filler improves the Coulombic efficiency and cycle life of full cells and suppresses electrolyte decomposition as indicated by solid-state nuclear magnetic resonance (NMR) and X-ray photoelectron spectroscopy (XPS) measurements. This indicates that the high dielectric filler can suppress dendrite formation, thereby reducing solid electrolyte decomposition reactions, resulting in the observed low overpotentials and improved cycling efficiency.

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Ceramic membranes made of garnet Li7Zr3La2O12 (LLZO) are promising separators for lithium metal batteries because they are chemically stable to lithium metal and can resist the growth of lithium dendrites. Free-standing garnet separators can be produced on a large scale using tape casting and sintering slurries containing LLZO powder, but the quality of the separators is severely compromized by the protonation of the moisture-sensitive LLZO during processing and the irreversible loss of lithium during sintering. In this work, an approach is presented to mitigate the degradation of the LLZO and produce high quality separators using Li2CO3 as a source of excess lithium. By systematically investigating the effects of Li2CO3 addition during the different steps of the tape casting process and the intricate relationship between the protonation and relithiation of LLZO phase, the formation of highly protonated LLZO during ball milling was identified as the most critical step. It was shown that the addition of minimal amounts of Li2CO3 during wet milling effectively suppresses LLZO protonation and ensure the effectiveness of relithiation during subsequent sintering. Using this modified method, flat LLZO separators with a relative density of 95.3 % were prepared in a simplified process with a significantly reduced excess lithium of only 5 mol % with respect to the stoichiometric LLZO, exhibiting an ionic conductivity of 0.18 mS cm−1 at room temperature and a critical current density of 1 mA cm−2 at 60 °C for lithium stripping/plating.@en

Solid-state batteries currently receive ample attention due to their potential to outperform lithium-ion batteries in terms of energy density when featuring next-generation anodes such as lithium metal or silicon. One key remaining challenge is identifying solid electrolytes that combine high ionic conductivity with stability in contact with the highly reducing potentials of next-generation anodes. Fully reduced electrolytes, based on irreducible anions, offer a promising solution by avoiding electrolyte decomposition altogether. In this study, we demonstrate the compositional flexibility of the disordered antifluorite framework accessible by mechanochemical synthesis and leverage it to discover irreducible electrolytes with high ionic conductivities. We show that the recently investigated Li ₉N ₂Cl ₃ and Li ₅NCl ₂ phases are part of the same solid solution of Li-deficient antifluorite phases existing on the LiCl-Li ₃N tie line with a general chemical formula of Li _1+2xCl _1−xN _x (0.33 < x < 0.5). Using density functional theory calculations, we identify the origin of the 5-order-of-magnitude conductivity increase of the Li _1+2xCl _1−xN _x phases compared to the structurally related rock-salt LiCl phase. Finally, we demonstrate that S _Cl- and Br _Cl-substituted analogues of the Li _1+2xCl _1−xN _x phases may be synthesized, enabling significant conductivity improvements by a factor of 10, reaching 0.2 mS cm ⁻¹ for Li _2.31S _0.41Br _0.14N _0.45. This investigation demonstrates for the first time that irreducible antifluorite-like phases are compositionally highly modifiable; this finding lays the ground for discovery of new compositions of irreducible antifluorite-like phases with even further increased conductivities, which could help eliminate solid-electrolyte decomposition and decomposition-induced Li losses on the anode side in high-performance next-generation batteries.

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Ordered layered structures serve as essential components in lithium (Li)-ion cathodes^1–3. However, on charging, the inherently delicate Li-deficient frameworks become vulnerable to lattice strain and structural and/or chemo-mechanical degradation, resulting in rapid capacity deterioration and thus short battery life^2,4. Here we report an approach that addresses these issues using the integration of chemical short-range disorder (CSRD) into oxide cathodes, which involves the localized distribution of elements in a crystalline lattice over spatial dimensions, spanning a few nearest-neighbour spacings. This is guided by fundamental principles of structural chemistry and achieved through an improved ceramic synthesis process. To demonstrate its viability, we showcase how the introduction of CSRD substantially affects the crystal structure of layered Li cobalt oxide cathodes. This is manifested in the transition metal environment and its interactions with oxygen, effectively preventing detrimental sliding of crystal slabs and structural deterioration during Li removal. Meanwhile, it affects the electronic structure, leading to improved electronic conductivity. These attributes are highly beneficial for Li-ion storage capabilities, markedly improving cycle life and rate capability. Moreover, we find that CSRD can be introduced in additional layered oxide materials through improved chemical co-doping, further illustrating its potential to enhance structural and electrochemical stability. These findings open up new avenues for the design of oxide cathodes, offering insights into the effects of CSRD on the crystal and electronic structure of advanced functional materials.

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Nickel-rich layered oxide cathodes promise ultrahigh energy density but is plagued by the mechanical failure of the secondary particle upon (de)lithiation. Existing approaches for alleviating the structural degradation could retard pulverization, yet fail to tune the stress distribution and root out the formation of cracks. Herein, we report a unique strategy to uniformize the stress distribution in secondary particle via Kirkendall effect to stabilize the core region during electrochemical cycling. Exotic metal/metalloid oxides (such as Al₂O₃ or SiO₂) is introduced as the heterogeneous nucleation seeds for the preferential growth of the precursor. The calcination treatment afterwards generates a dopant-rich interior structure with central Kirkendall void, due to the different diffusivity between the exotic element and nickel atom. The resulting cathode material exhibits superior structural and electrochemical reversibility, thus contributing to a high specific energy density (based on cathode) of 660 Wh kg⁻¹ after 500 cycles with a retention rate of 86%. This study suggests that uniformizing stress distribution represents a promising pathway to tackle the structural instability facing nickel-rich layered oxide cathodes.

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Transport electrification and grid storage hinge largely on fast-charging capabilities of Li- and Na-ion batteries, but anodes such as graphite with plating issues drive the scientific focus towards anodes with slopped storage potentials. Here we report fast charging of ampere-hour-level full Na-ion batteries within about 9 minutes for continuous 3,000 cycles based on hard carbon anodes. These anodes, in addition to displaying a sloped storage voltage, provide capacity at a nearly constant voltage just above the plating potential, without observing Na-metal plating under high areal capacity. Comparing the electrochemical behaviour of Li and Na in hard carbon through experimental and computational techniques, a unified storage mechanism relying on the dimensions of wedge nanopores and drawing parallels with underpotential deposition for metals is brought forward, providing a rational guide for achieving fast storage in hard carbon anodes.

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One of the primary challenges to improving lithium-ion batteries lies in comprehending and controlling the intricate interphases. However, the complexity of interface reactions and the buried nature make it difficult to establish the relationship between the interphase characteristics and electrolyte chemistry. Herein, we employ diverse characterization techniques to investigate the progression of electrode-electrolyte interphases, bringing forward opportunities to improve the interphase properties by what we refer to as high-entropy solvation disordered electrolytes. Through formulating an electrolyte with a regular 1.0 M concentration that includes multiple commercial lithium salts, the solvation interaction with lithium ions alters fundamentally. The participation of several salts can result in a weaker solvation interaction, giving rise to an anion-rich and disordered solvation sheath despite the low salt concentration. This induces a conformal, inorganic-rich interphase that effectively passivates electrodes, preventing solvent co-intercalation. Remarkably, this electrolyte significantly enhances the performance of graphite-containing anodes paired with high-capacity cathodes, offering a promising avenue for tailoring interphase chemistries.

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All-solid-state lithium batteries have attracted widespread attention for next-generation energy storage, potentially providing enhanced safety and cycling stability. The performance of such batteries relies on solid electrolyte materials; hence many structures/phases are being investigated with increasing compositional complexity. Among the various solid electrolytes, lithium halides show promising ionic conductivity and cathode compatibility, however, there are no effective guidelines when moving toward complex compositions that go beyond ab-initio modeling. Here, we show that ionic potential, the ratio of charge number and ion radius, can effectively capture the key interactions within halide materials, making it possible to guide the design of the representative crystal structures. This is demonstrated by the preparation of a family of complex layered halides that combine an enhanced conductivity with a favorable isometric morphology, induced by the high configurational entropy. This work provides insights into the characteristics of complex halide phases and presents a methodology for designing solid materials.

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Metal-ion batteries, particularly lithium-ion (Li-ion) and sodium-ion (Na-ion) batteries, are currently among the most compelling technologies for energy storage. However, the growing demands driven by wide implementation of batteries in multiple applications call for further improvements of energy and power densities. Despite the incredible developments in this field observed over the past decades, the innovation of new active materials for metal-ion batteries has seen only modest progress, with primary focus on the optimization of already existing materials. The recent discovery of cathode materials with antiperovskite structure signals a promising direction for the creation of relatively simple materials geared towards electrochemical energy storage. These materials can be synthesized through relatively simple chemical processes using abundant elements and could offer stable electrochemical performance. Even though the number of reported examples is still limited, the structural flexibility of these materials offers multiple possibilities for tuning the chemical stability, operating voltage and capacity. This perspective provides a summary of the latest advancements in the field of antiperovskite active materials, highlighting both the advantages and the challenges associated with their integration into metal-ion batteries, and suggests possible future research directions towards practical implementation of this promising yet underexplored class of materials.

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Sodium-ion batteries have not only garnered substantial attention for grid-scale energy storage owing to the higher abundance of sodium compared with lithium, but also present the possibility of fast charging because of the inherently higher sodium-ion mobility. However, it remains a phenomenal challenge to achieve a combination of these merits, given the complex structural chemistry of sodium-ion oxide materials. Here we show that O3-type sodium-ion layered cathodes (for example, Na_5/6Li_2/27Ni_8/27Mn_11/27Ti_6/27O₂) have the potential to attain high power density, high energy density (260 Wh kg⁻¹ at the electrode level) and long cycle life (capacity retention of 80% over 700 cycles in full cells). The design involves introduction of characteristic P3-structural motifs into an O3-type framework that serves to promote sodium-ion diffusivity and address detrimental transition metal migration and phase transition at a high state of charge. This study provides a principle for the rational design of sodium-ion layered oxide electrodes and advances the understanding of the composition–structure–property relationships of oxide cathode materials.

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Formation cycling is a critical process aimed at improving the performance of lithium ion (Li-ion) batteries during subsequent use. Achieving highly reversible Li-metal anodes, which would boost battery energy density, is a formidable challenge. Here, formation cycling and its impact on the subsequent cycling are largely unexplored. Through solid-state nuclear magnetic resonance (ssNMR) spectroscopy experiments, we reveal the critical role of the Li-ion diffusion dynamics between the electrodeposited Li-metal (ED-Li) and the as-formed solid electrolyte interphase (SEI). The most stable cycling performance is realized after formation cycling at a relatively high current density, causing an optimum in Li-ion diffusion over the Li-metal-SEI interface. We can relate this to a specific balance in the SEI chemistry, explaining the lasting impact of formation cycling. Thereby, this work highlights the importance and opportunities of regulating initial electrochemical conditions for improving the stability and life cycle of lithium metal batteries.

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Due to their high ionic conductivity, lithium-ion conducting argyrodites show promise as solid electrolytes for solid-state batteries. Aliovalent substitution is an effective technique to enhance the transport properties of Li₆PS₅Br, where aliovalent Si substitution triples ionic conductivity. However, the origin of this experimentally observed increase is not fully understood. Our density functional theory (DFT) study reveals that Si⁴⁺ substitution increases Li diffusion by activating Li occupancy in the T4 sites. Redistribution of Li-ions within the lattice results in a more uniform distribution of Li around the T4 and neighboring T5 sites, flattening the energy landscape for diffusion. Since the T4 site is positioned in the intercage jump pathway, an increase in the intercage jump rate is found, which is directly related to the macroscopic diffusion and bulk conductivity. Analysis of neutron diffraction experiments confirms partial T4 site occupancy, in agreement with the computational findings. Understanding the aliovalent substitution effect on interstitials is crucial for improving solid electrolyte ionic conductivity and advancing solid-state battery performance.

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The formation of stable interphases on the electrodes is crucial for rechargeable lithium (Li) batteries. However, next-generation high-energy batteries face challenges in controlling interphase formation due to the high reactivity and structural changes of electrodes, leading to reduced stability and slow ion transport, which accelerate battery degradation. Here, we report an approach to address these issues by introducing multicomponent grain-boundary-rich interphase that boosts the rapid transport of ions and enhances passivation toward prolonged lifespan. This is guided by fundamental principles of solid-state ionics and geological crystallization differentiation theory, achieved through improved solvation chemistry. Demonstrations showcase how the introduction of the interphase substantially impacts the Li-ion transport across the interphase and the electrode-electrolyte compatibility in cost-effective electrolyte solutions optimized with multiple Li salts. The resulting interphases feature microstructures rich in inorganic grain boundaries with a diverse array of nanosized grains, presenting enhanced Li-ion transport. Comprehensive analyses revealed that this realizes remarkable electrochemical stability over extended cycling periods by inhibiting electrode corrosion, thus holding promise for high-capacity thin-Li-metal, Si-based anodes, and even Li-free anodes when paired with high-capacity oxide cathodes. This work opens new avenues to customize protective interphases on high-capacity electrodes, promoting the development of batteries with the highest energy density using cost-effective electrolytes.

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