Organic electrode materials have shown great potential for metal-ion batteries because of their high theoretical capacity, flexible structure designability, and environmental friendliness. However, their electrochemical performance still needs to be further enhanced, which mainly depends on the molecular structures, electrode fabrication, electrolyte, and separators. In this review, we present the working principles and fundamental properties of different types of organic electrode materials, including conductive polymers, organosulfur compounds, organic radicals, carbonyl compounds, and other emerging materials. We then focus on the strategies toward enhancing the electrochemical performance (output voltage, capacity, cycling stability, and rate performance) of organic electrode materials in various metal-ion batteries. The key challenges of organic electrode materials for metal-ion batteries mainly contain the high solubility in electrolyte, low intrinsic electronic conductivity, large volume change, and low tap density. This review provides insights into the development of organic electrode materials with high performance for next-generation rechargeable metal-ion batteries.

Rechargeable aqueous batteries are an up-and-coming system for potential large-scale energy storage due to their high safety and low cost. However, the freeze of aqueous electrolyte limits the low-temperature operation of such batteries. Here, we report the breakage of original hydrogen-bond network in ZnCl2 solution by modulating electrolyte structure, and thus suppressing the freeze of water and depressing the solid-liquid transition temperature of the aqueous electrolyte from 0 to –114 °C. This ZnCl2-based low-temperature electrolyte renders polyaniline||Zn batteries available to operate in an ultra-wide temperature range from –90 to +60 °C, which covers the earth surface temperature in record. Such polyaniline||Zn batteries are robust at –70 °C (84.9 mA h g−1) and stable during over 2000 cycles with ~100% capacity retention. This work significantly provides an effective strategy to propel low-temperature aqueous batteries via tuning the electrolyte structure and widens the application range of temperature adaptation of aqueous batteries.

Sodium batteries are considered as promising candidates for large-scale energystorage systems owing to the abundant and low-cost sodium resources. However, many reported sodium batteries are based on conventional organic liquid electrolyte, which would lead to potential safety issues. Developing solid-state electrolyte (SSE) for sodium batteries is an effective way to solve such problems. Nevertheless, how to develop high-performance SSE and compatible interface for constructing solid-state sodium batteries is still challenging. In this review, we mainly focus on the development and recent advances of SSE (including all-solid-state and quasisolid-state electrolyte) and interface engineering for sodium batteries. The structure-property correlations and design principles of different inorganic and organic SSE are discussed in depth. The comprehensive performance of SSE depends on the structural characteristics such as defects, crystallinity, and stability of bonds. The design principles mainly include increasing the density of mobile Na + ions, reducing the energy barrier, immobilizing anions, adjusting the stability of bonds, adding specific buffer layers, and increasing interfacial contact area. Moreover, we discuss the interface between SSE and electrode because a suitable interface is the key prerequisite for high-performance solid-state sodium batteries. This review provides fundamental insights and future perspectives to design advanced SSE and concomitant interface for next-generation rechargeable solid-state sodium batteries.

Operating at low temperatures is a great challenge that hinders the practical application of aqueous batteries at subzero temperatures. The frozen electrolyte and the limited capacity of the cathode at low temperatures are the main reasons. Herein, we report synthetic electrolyte/cathode design strategies for low-temperature aqueous Zn batteries. The fundamental correlations between anion chemistries and freezing point depression of water are revealed by multi-perspective characterization. Coupled with the chaotropic anion, CF3SO3 –, the 2 M zinc electrolyte features a low freezing point of −34.1 °C and high ionic conductivity of 4.47 mS cm–1 at −30 °C. With the benefits of the low-temperature electrolyte and fast-kinetics cathode, Zn||V2O5 batteries deliver a high specific capacity of 285.0 mAh g–1 at −30 °C with capacity retention of 81.7% after 1000 cycles. This work points out the fundamental understanding of anion chemistries and synthetic design strategies for developing low-temperature aqueous batteries.

We present a detailed analysis of the picosecond-to-nanosecond motions of green fluorescent protein (GFP) and its hydration water using neutron scattering spectroscopy and hydrogen/deuterium contrast. The analysis reveals that hydration water suppresses protein motions at lower temperatures (<~ 200 K), and facilitates protein dynamics at high temperatures. Experimental data demonstrate that the hydration water is harmonic at temperatures <~ 180-190 K and is not affected by the proteins' methyl group rotations. The dynamics of the hydration water exhibits changes at ~ 180-190 K that we ascribe to the glass transition in the hydrated protein. Our results confirm significant differences in the dynamics of protein and its hydration water at high temperatures: on the picosecond-to-nanosecond timescale, the hydration water exhibits diffusive dynamics, while the protein motions are localized to <~3 Å. The diffusion of the GFP hydration water is similar to the behavior of hydration water previously observed for other proteins. Comparison with other globular proteins (e.g., lysozyme) reveals that on the timescale of 1 ns and at equivalent hydration level, GFP dynamics (mean-square displacements and quasielastic intensity) are of much smaller amplitude. Moreover, the suppression of the protein dynamics by the hydration water at low temperatures appears to be stronger in GFP than in other globular proteins. We ascribe this observation to the barrellike structure of GFP.

The main protease (3CL Mpro) from SARS-CoV-2, the etiological agent of COVID-19, is an essential enzyme for viral replication. 3CL Mpro possesses an unusual catalytic dyad composed of Cys145 and His41 residues. A critical question in the field has been what the protonation states of the ionizable residues in the substrate-binding active site cavity are; resolving this point would help understand the catalytic details of the enzyme and inform rational drug development against this pernicious virus. Here, we present the room-temperature neutron structure of 3CL Mpro, which allowed direct determination of hydrogen atom positions and, hence, protonation states in the protease. We observe that the catalytic site natively adopts a zwitterionic reactive form where Cys145 is in the negatively charged thiolate state, and His41 is doubly protonated and positively charged, instead of the neutral unreactive state usually envisaged. The neutron structure also identified the protonation states, and thus electrical charges, of all other amino acid residues and revealed intricate hydrogen bonding networks in the active site cavity and at the dimer interface. The fine atomic details present in this structure were made possible by the unique scattering properties of the neutron, which is an ideal probe for locating hydrogen positions and experimentally determining protonation states at near-physiological temperature. Our observations provide critical information for structure-assisted and computational drug design, allowing precise tailoring of inhibitors to the enzyme’s electrostatic environment.

Coupling quinone cathode with ionic liquid electrolyte is demonstrated to build high-energy and long-life sodium-ion batteries. Computational and spectroscopic studies reveal that the inhibitory effect of ionic liquid on dissolution of quinone correlates with the strong polarity, weak electron donor ability, and low interaction energy. The calix[4]quinone and 5,7,12,14-pentacenetetrone cathodes exhibit significantly improved cycling performance in N-methyl-N-propylpyrrolidinium bis(trifluoromethanesulfonyl)amide than in ether electrolyte. These results would enlighten the design and application of ionic liquid and quinones for organic batteries. HIGHLIGHTSA facile strategy is proposed to suppress the dissolution of quinone electrodes Inhibitory effect of ILs correlates to polarity, donor number, and binding energy [PY13][TFSI] markedly inhibits quinone dissolution C4Q and PT cathodes exhibit better capacity retention in ILs than in ether Wang et al., Chem 5, 364-375 February 14, SUMMARYQuinone-based sodium-ion batteries (SIBs) are highly desirable electrochemical devices with high capacity and low cost but suffer from poor cycle life and low practical energy because of quinone dissolution in aprotic electrolyte. Herein, we report a facile strategy of using ionic liquid (IL) to tackle the dissolution of quinone electrodes. The inhibitory effect of ILs on quinone dissolution correlates with their polarity, donor number, and interaction energy, as revealed by combined density functional theory and spectroscopy studies. Particularly, in N-methyl-N-propylpyrrolidinium bis(trifluoromethanesulfonyl)amide ([PY13] [TFSI]) electrolyte with weak donor ability and large polarity, calix[4]quinone cathode exhibits high capacity (>400 mAh g À1 ) and superior capacity retention ($99.7% at 130 mA g À1 for 300 cycles), significantly outperforming that in etherbased electrolyte. Moreover, the remarkable cyclability and considerable rate capability of 5,7,12,14-pentacenetetrone in [PY13][TFSI] render it a promising sodium-storage material. This work would promote the development of highperformance SIBs with quinone electrodes and IL electrolyte.

Rechargeable aqueous Zn metal batteries have become promising candidates for large-scale electrochemical energy storage owing to their high safety and affordable low cost. However, Zn metal anode suffers from dendritic growth and hydrogen evolution reaction (HER), deteriorating the electrochemical performance. Here, we demonstrate that these challenges can be conquered by introducing a halogen ion into the Zn2+ solvation structure. By designing an electrolyte composed of zinc acetate and ammonium halide, the electron-donating anion I– can coordinate with Zn2+ and transform the traditional Zn­(H2O)6 2+ to ZnI­(H2O)5 +, in which I– could transfer electrons into H2O and thus suppress HER. The dynamic electrostatic shielding layer formed by concomitant NH4 + can restrict the dendritic growth. As a result, the halogenated electrolyte achieves a high initial coulombic efficiency (CE) of 99.3% in the Zn plating/stripping process and remains at an average of ∼99.8% with uniform Zn deposition. Moreover, Zn–I batteries are constructed by using dissociative I– as the cathode and carbon felt–polyaniline as the conductive and adsorptive layer, exhibiting an average CE of 98.6% without capacity decay after 300 cycles. This work provides insights into the halogenated Zn2+ solvation structure and offers a general electrolyte design strategy for achieving a highly reversible Zn metal anode and batteries.