Understanding the Chemomechanical Function of the Silver-Carbon Interlayer in Sheet-type All-Solid-State Lithium-Metal Batteries.

All-solid-state batteries with lithium metal anodes hold great potential for high-energy battery applications. However, forming and maintaining stable solid-solid contact between the lithium anode and solid electrolyte remains a major challenge. One promising solution is the use of a silver-carbon (Ag-C) interlayer, but its chemomechanical properties and impact on interface stabilities need to be comprehensively explored. Here, we examine the function of Ag-C interlayers in addressing interfacial challenges using various cell configurations. Experiments show that the interlayer improves interfacial mechanical contact, leading to a uniform current distribution and suppressing lithium dendrite growth. Furthermore, the interlayer regulates lithium deposition in the presence of Ag particles via improved Li diffusivity. The sheet-type cells with the interlayer achieve a high energy density of 514.3 Wh L-1 and an average Coulombic efficiency of 99.97% over 500 cycles. This work provides insights into the benefits of using Ag-C interlayers for enhancing the performance of all-solid-state batteries.

Cyclotetrabenzil Derivatives for Electrochemical Lithium-Ion Storage.

Organic electrode materials could revolutionize batteries because of their high energy densities, the use of Earth-abundant elements, and structural diversity which allows fine-tuning of electrochemical properties. However, small organic molecules and intermediates formed during their redox cycling in lithium-ion batteries (LIBs) have high solubility in organic electrolytes, leading to rapid decay of cycling performance. We report the use of three cyclotetrabenzil octaketone macrocycles as cathode materials for LIBs. The rigid and insoluble naphthalene-based cyclotetrabenzil reversibly accepts eight electrons in a two-step process with a specific capacity of 279 mAh g-1 and a stable cycling performance with ≈65 % capacity retention after 135 cycles. DFT calculations indicate that its reduction increases both ring strain and ring rigidity, as demonstrated by computed high distortion energies, repulsive regions in NCI plots, and close [C⋅⋅⋅C] contacts between the naphthalenes. This work highlights the importance of shape-persistency and ring strain in the design of redox-active macrocycles that maintain very low solubility in various redox states.

Opportunities and Challenges for Organic Electrodes in Electrochemical Energy Storage.

As the world moves toward electromobility and a concomitant decarbonization of its electrical supply, modern society is also entering a so-called fourth industrial revolution marked by a boom of electronic devices and digital technologies. Consequently, battery demand has exploded along with the need for ores and metals to fabricate them. Starting from such a critical analysis and integrating robust structural data, this review aims at pointing out there is room to promote organic-based electrochemical energy storage. Combined with recycling solutions, redox-active organic species could decrease the pressure on inorganic compounds and offer valid options in terms of environmental footprint and possible disruptive chemistries to meet the energy storage needs of both today and tomorrow. We review state-of-the-art developments in organic batteries, current challenges, and prospects, and we discuss the fundamental principles that govern the reversible chemistry of organic structures. We provide a comprehensive overview of all reported cell configurations that involve electroactive organic compounds working either in the solid state or in solution for aqueous or nonaqueous electrolytes. These configurations include alkali (Li/Na/K) and multivalent (Mg, Zn)-based electrolytes for conventional "sealed" batteries and redox-flow systems. We also highlight the most promising systems based on such various chemistries relying on appropriate metrics such as operation voltage, specific capacity, specific energy, or cycle life to assess the performances of electrodes.

Separator Effect on Zinc Electrodeposition Behavior and Its Implication for Zinc Battery Lifetime.

Uncontrolled zinc electrodeposition is an obstacle to long-cycling zinc batteries. Much has been researched on regulating zinc electrodeposition, but rarely are the studies performed in the presence of a separator, as in practical cells. Here, we show that the microstructure of separators determines the electrodeposition behavior of zinc. Porous separators direct zinc to deposit into their pores and leave "dead zinc" upon stripping. In contrast, a nonporous separator prevents zinc penetration. Such a difference between the two types of separators is distinguished only if caution is taken to preserve the attachment of the separator to the zinc-deposited substrate during the entire electrodeposition-morphological observation process. Failure to adopt such a practice could lead to misinformed conclusions. Our work reveals the mere use of porous separators as a universal yet overlooked challenge for metal anode-based rechargeable batteries. Countermeasures to prevent direct exposure of the metal growth front to a porous structure are suggested.

Universal quinone electrodes for long cycle life aqueous rechargeable batteries.

Aqueous rechargeable batteries provide the safety, robustness, affordability, and environmental friendliness necessary for grid storage and electric vehicle operations, but their adoption is plagued by poor cycle life due to the structural and chemical instability of the anode materials. Here we report quinones as stable anode materials by exploiting their structurally stable ion-coordination charge storage mechanism and chemical inertness towards aqueous electrolytes. Upon rational selection/design of quinone structures, we demonstrate three systems that coupled with industrially established cathodes and electrolytes exhibit long cycle life (up to 3,000 cycles/3,500 h), fast kinetics (≥20C), high anode specific capacity (up to 200-395 mAh g-1), and several examples of state-of-the-art specific energy/energy density (up to 76-92 Wh kg-1/ 161-208 Wh l-1) for several operational pH values (-1 to 15), charge carrier species (H+, Li+, Na+, K+, Mg2+), temperature (-35 to 25 °C), and atmosphere (with/without O2), making them a universal anode approach for any aqueous battery technology.

Tailored Organic Electrode Material Compatible with Sulfide Electrolyte for Stable All-Solid-State Sodium Batteries.

All-solid-state sodium batteries (ASSSBs) with nonflammable electrolytes and ubiquitous sodium resource are a promising solution to the safety and cost concerns for lithium-ion batteries. However, the intrinsic mismatch between low anodic decomposition potential of superionic sulfide electrolytes and high operating potentials of sodium-ion cathodes leads to a volatile cathode-electrolyte interface and undesirable cell performance. Here we report a high-capacity organic cathode, Na4 C6 O6 , that is chemically and electrochemically compatible with sulfide electrolytes. A bulk-type ASSSB shows high specific capacity (184 mAh g-1 ) and one of the highest specific energies (395 Wh kg-1 ) among intercalation compound-based ASSSBs. The capacity retentions of 76 % after 100 cycles at 0.1 C and 70 % after 400 cycles at 0.2 C represent the record stability for ASSSBs. Additionally, Na4 C6 O6 functions as a capable anode material, enabling a symmetric all-organic ASSSB with Na4 C6 O6 as both cathode and anode materials.

Interlayer-expanded molybdenum disulfide nanocomposites for electrochemical magnesium storage.

Mg rechargeable batteries (MgRBs) represent a safe and high-energy battery technology but suffer from the lack of suitable cathode materials due to the slow solid-state diffusion of the highly polarizing divalent Mg ion. Previous methods improve performance at the cost of incompatibility with anode/electrolyte and drastic decrease in volumetric energy density. Herein we report interlayer expansion as a general and effective atomic-level lattice engineering approach to transform inactive intercalation hosts into efficient Mg storage materials without introducing adverse side effects. As a proof-of-concept we have combined theory, synthesis, electrochemical measurement, and kinetic analysis to improve Mg diffusion behavior in MoS2, which is a poor Mg transporting material in its pristine form. First-principles simulations suggest that expanded interlayer spacing allows for fast Mg diffusion because of weakened Mg-host interactions. Experimentally, the expansion was realized by inserting a controlled amount of poly(ethylene oxide) into the lattice of MoS2 to increase the interlayer distance from 0.62 nm to up to 1.45 nm. The expansion boosts Mg diffusivity by 2 orders of magnitude, effectively enabling the otherwise barely active MoS2 to approach its theoretical storage capacity as well as to achieve one of the highest rate capabilities among Mg-intercalation materials. The interlayer expansion approach can be leveraged to a wide range of host materials for the storage of various ions, leading to novel intercalation chemistry and opening up new opportunities for the development of advanced materials for next-generation energy storage.

Heavily n-Dopable π-Conjugated Redox Polymers with Ultrafast Energy Storage Capability.

We report here the first successful demonstration of a "π-conjugated redox polymer" simultaneously featuring a π-conjugated backbone and integrated redox sites, which can be stably and reversibly n-doped to a high doping level of 2.0 with significantly enhanced electronic conductivity. The properties of such a heavily n-dopable polymer, poly{[N,N'-bis(2-octyldodecyl)-1,4,5,8-naphthalenedicarboximide-2,6-diyl]-alt-5,5'-(2,2'-bithiophene)} (P(NDI2OD-T2)), were compared vis-à-vis to those of the corresponding backbone-insulated poly{[N,N'-bis(2-octyldodecyl)-1,4,5,8-naphthalenedicarboximide-2,6-diyl]-alt-5,5'-[2,2'-(1,2-ethanediyl)bithiophene]} (P(NDI2OD-TET)). When evaluated as a charge storage material for rechargeable Li batteries, P(NDI2OD-T2) delivers 95% of its theoretical capacity at a high rate of 100C (72 s per charge-discharge cycle) under practical measurement conditions as well as 96% capacity retention after 3000 cycles of deep discharge-charge. Electrochemical, impedance, and charge-transport measurements unambiguously demonstrate that the ultrafast electrode kinetics of P(NDI2OD-T2) are attributed to the high electronic conductivity of the polymer in the heavily n-doped state.

Imaging solid-electrolyte interphase dynamics using operando reflection interference microscopy.

The quality of the solid-electrolyte interphase is crucial for the performance of most battery chemistries, but its formation dynamics during operation are not well understood due to a lack of reliable operando characterization techniques. Herein, we report a dynamic, non-invasive, operando reflection interference microscope to enable the real-time imaging of the solid-electrolyte interphase during its formation and evolution processes with high sensitivity. The stratified structure of the solid-electrolyte interphase formed during four distinct steps includes the emergence of a permanent inner inorganic layer enriched in LiF, a transient assembly of an interfacial electrified double layer and a consequent emergence of a temporary outer organic-rich layer whose presence is reversible with electrochemical cycling. Reflection interference microscope imaging reveals an inverse correlation between the thicknesses of two interphasial subcomponents, implying that the permanent inorganic-rich inner layer dictates the organic-rich outer layer formation and lithium nucleation. The real-time visualization of solid-electrolyte interphase dynamics provides a powerful tool for the rational design of battery interphases.

A cellulose-derived supramolecule for fast ion transport.

Supramolecular frameworks have been widely synthesized for ion transport applications. However, conventional approaches of constructing ion transport pathways in supramolecular frameworks typically require complex processes and display poor scalability, high cost, and limited sustainability. Here, we report the scalable and cost-effective synthesis of an ion-conducting (e.g., Na+) cellulose-derived supramolecule (Na-CS) that features a three-dimensional, hierarchical, and crystalline structure composed of massively aligned, one-dimensional, and ångström-scale open channels. Using wood-based Na-CS as a model material, we achieve high ionic conductivities (e.g., 0.23 S/cm in 20 wt% NaOH at 25 °C) even with a highly dense microstructure, in stark contrast to conventional membranes that typically rely on large pores (e.g., submicrometers to a few micrometers) to obtain comparable ionic conductivities. This synthesis approach can be universally applied to a variety of cellulose materials beyond wood, including cotton textiles, fibers, paper, and ink, which suggests excellent potential for a number of applications such as ion-conductive membranes, ionic cables, and ionotronic devices.

A Quinone Anode for Lithium-Ion Batteries in Mild Aqueous Electrolytes.

Aqueous batteries could be potentially used for grid-scale energy storage owing to the use of nonflammable electrolytes and long cycle life. Recently, quinones have shown examples as redox-active materials in aqueous batteries under either strong acidic or basic conditions. However, a quinone-based battery with a less corrosive electrolyte is still rare. Given that quinone-based batteries are heavily influenced by the pH of electrolytes, we studied the influence of acid dissociation constants (pKa) of hydroquinones on their performance as solid electrode materials. We measured the pKa of anthracene-9,10-diol (AQH2 ) and benzo[1,2-b:4,5-b']dithiophene-4,8-diol (BDTDH2 ) from the Pourbaix diagrams of two para-quinone monomers [i.e., anthracene-9,10-dione (AQ) and benzo[1,2-b:4,5-b']dithiophene-4,8-dione (BDTD)]. Subsequently, their polymeric forms [i.e., poly(anthraquinonyl sulfide) (PAQS) and poly(benzo[1,2-b:4,5-b']dithiophene-4,8-dione-2,6-diyl sulfide) (PBDTDS)] were investigated as electrodes in aqueous lithium-ion cells. At pH 13, PAQS demonstrates a low capacity and poor cycle life, whereas PBDTDS shows a capacity of 196 mAh g-1 and fade rates of 0.0038 % per cycle over 4200 cycles, 0.77 % per day over 21 days. The differences in capacity and cycle stability can be explained by the difference of corresponding pKa values. A full cell with the configuration of (-)PBDTDS|2.5 m Li2 SO4 (pH 13)|LiCoO2 (+) shows a voltage of 1.08 V, a capacity of 72 mAh g-1 and ≈99.9 % of Coulombic efficiency for 500 stable cycles.

Flower-Like Molybdenum Disulfide for Polarity-Triggered Accumulation/Release of Small Molecules.

Flower-like molybdenum disulfide (MoS2) with rich edge sites has been prepared by the hydrothermal method. The edge sites possess polarity due to the noncentrosymmetric Mo-S on exposed (100) facets and thus show a strong electrostatic attraction toward polar species. The flower-like MoS2 can be used as small-molecule carriers for the model drug, Rhodamine B (RhB). The results prove that flower-like MoS2 have fast adsorption kinetics and perform a switchable accumulation/release with response to the solvent polarity. An outstanding reusability can be found in flower-like MoS2 due to little cargo retention, and the recycle of adsorption can be repeated 100 times with above 88.5% of the adsorption capacity retained. The flower-like MoS2 with solvent polarity-triggered loading/release can be extended to controlled release and color switch of display.

An Aqueous Ca-Ion Battery.

Multivalent-ion batteries are emerging as low-cost, high energy density, and safe alternatives to Li-ion batteries but are challenged by slow cation diffusion in electrode materials due to the high polarization strength of Mg- and Al-ions. In contrast, Ca-ion has a low polarization strength similar to that of Li-ion, therefore a Ca-ion battery will share the advantages while avoiding the kinetics issues related to multivalent batteries. However, there is no battery known that utilizes the Ca-ion chemistry due to the limited success in Ca-ion storage materials. Here, a safe and low-cost aqueous Ca-ion battery based on a highly reversible polyimide anode and a high-potential open framework copper hexacyanoferrate cathode is demonstrated. The prototype cell shows a stable capacity and high efficiency at both high and low current rates, with an 88% capacity retention and an average 99% coloumbic efficiency after cycling at 10C for 1000 cycles. The Ca-ion storage mechanism for both electrodes as well as the origin of the fast kinetics have been investigated. Additional comparison with a Mg-ion cell with identical electrodes reveals clear kinetics advantages for the Ca-ion system, which is explained by the smaller ionic radii and more facile desolvation of hydrated Ca-ions.

Fast kinetics of magnesium monochloride cations in interlayer-expanded titanium disulfide for magnesium rechargeable batteries.

Magnesium rechargeable batteries potentially offer high-energy density, safety, and low cost due to the ability to employ divalent, dendrite-free, and earth-abundant magnesium metal anode. Despite recent progress, further development remains stagnated mainly due to the sluggish scission of magnesium-chloride bond and slow diffusion of divalent magnesium cations in cathodes. Here we report a battery chemistry that utilizes magnesium monochloride cations in expanded titanium disulfide. Combined theoretical modeling, spectroscopic analysis, and electrochemical study reveal fast diffusion kinetics of magnesium monochloride cations without scission of magnesium-chloride bond. The battery demonstrates the reversible intercalation of 1 and 1.7 magnesium monochloride cations per titanium at 25 and 60 °C, respectively, corresponding to up to 400 mAh g-1 capacity based on the mass of titanium disulfide. The large capacity accompanies with excellent rate and cycling performances even at room temperature, opening up possibilities for a variety of effective intercalation hosts for multivalent-ion batteries.Magnesium rechargeable batteries potentially offer high-energy density, safety, and low cost. Here the authors show a battery that reversibly intercalates magnesium monochloride cations with excellent rate and cycle performances in addition to the large capacity.

A magnesium-sodium hybrid battery with high operating voltage.

We report a high performance magnesium-sodium hybrid battery utilizing a magnesium-sodium dual-salt electrolyte, a magnesium anode, and a Berlin green cathode. The cell delivers an average discharge voltage of 2.2 V and a reversible capacity of 143 mA h g(-1). We also demonstrate the cell with an energy density of 135 W h kg(-1) and a high power density of up to 1.67 kW kg(-1).

High areal capacity hybrid magnesium-lithium-ion battery with 99.9% Coulombic efficiency for large-scale energy storage.

Hybrid magnesium-lithium-ion batteries (MLIBs) featuring dendrite-free deposition of Mg anode and Li-intercalation cathode are safe alternatives to Li-ion batteries for large-scale energy storage. Here we report for the first time the excellent stability of a high areal capacity MLIB cell and dendrite-free deposition behavior of Mg under high current density (2 mA cm(-2)). The hybrid cell showed no capacity loss for 100 cycles with Coulombic efficiency as high as 99.9%, whereas the control cell with a Li-metal anode only retained 30% of its original capacity with Coulombic efficiency well below 90%. The use of TiS2 as a cathode enabled the highest specific capacity and one of the best rate performances among reported MLIBs. Postmortem analysis of the cycled cells revealed dendrite-free Mg deposition on a Mg anode surface, while mossy Li dendrites were observed covering the Li surface and penetrated into separators in the Li cell. The energy density of a MLIB could be further improved by developing electrolytes with higher salt concentration and wider electrochemical window, leading to new opportunities for its application in large-scale energy storage.

Li3VO4 anchored graphene nanosheets for long-life and high-rate lithium-ion batteries.

Li3VO4 nanoparticles embedded in graphene nanosheets (Li3VO4@GNS) were obtained using a sol-gel method. The composite presents excellent high-rate performance with a stable capacity of 133 mA h g(-1) at 50 C and long-life performance with a capacity retention rate of 63.1% after 5000 cycles at 5 C.

Promoted hydrogen release from ammonia borane with mannitol via a solid-state reaction route.

Promoted hydrogen release from ammonia borane (NH(3)BH(3), AB) with mannitol (C(6)H(8)(OH)(6), MA) additive is reported. It is found that for the MA/2AB sample, the dehydrogenation temperature is lowered by ~25 °C compared to that of neat AB, the liberation of undesired byproduct borazine is suppressed, and the released ammonia can be removed by using anhydrous MgCl(2) as absorber. The analyses of Raman, Fourier transform infrared spectroscopy and (11)B nuclear magnetic resonance spectroscopy demonstrate the breaking of B-N, B-H and O-H bonds and the formation of B-O bonds for the dehydrogenation process of MA/2AB. These results suggest a solid-state dehydrogenation reaction between AB and MA: the B-H(δ-) bonds in AB and the O-H(δ+) bonds in MA combine with each other to release H(2). Furthermore, the use of the perfect -OH carrier MA as additive leads to a straightforward understanding of the improved dehydrogenation of AB under the effect of hydroxyl groups in the solid state.

Rechargeable Mg batteries with graphene-like MoS2 cathode and ultrasmall Mg nanoparticle anode.

The combination of a highly exfoliated, graphene-like MoS2 cathode and ultrasmall Mg nanoparticle anode is proposed, for the first time, for rechargeable Mg batteries. Such a configuration exhibits an operating voltage of 1.8 V and a well reversible discharge capacity of ca. 170 mA h g−1, emphasizing the necessity of rational morphological control of electrode materials and opening up new opportunities for rechargeable Mg batteries.

Triphenylamine-based dyes bearing functionalized 3,4-propylenedioxythiophene linkers with enhanced performance for dye-sensitized solar cells.

Introduction of modified 3,4-propylenedioxythiophene units into triphenylamine-based dyes is found to enhance light capturing, suppress dye aggregation, and remarkably retard charge recombination in dye-sensitized solar cells. Open circuit voltages of the as-synthesized dyes (approximately 800 mV) are much higher than that with a thiophene congener (720 mV) under similar conditions as a result of self-passivation benefiting from their three-dimensional branched structures.