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The methanol distribution and electroosmotic drag in hydrated poly(perfluorosulfonic) acid electrolyte membrane are studied using molecular dynamics simulations under various electric fields applied. The results indicate that the methanol molecules are preferentially distributed near the hydrophobic PFSA backbones with their methyl groups in contact with the fluorine atoms and their hydroxyl groups pointing to the hydrophilic subphase. As the hydroxyl groups of methanol forming hydrogen bonds, hydroxyl groups are more likely to accept hydrogen atoms than to donate hydrogen atoms. The calculated methanol diffusion coefficient is in good correspondence with experimental values, and the electroosmotic drag coefficient for methanol is much smaller than that of water molecules. [ABSTRACT FROM AUTHOR]

The carbon coating strategy has emerged as an indispensable approach to improve the conductivity of polyanionic cathodes. However, owing to the complex reaction process between precursors of carbon and cathode, establishing a unified screening principle for carbonaceous precursors remains a technical challenge. Herein, we reveal that carbonaceous precursor pyrolysis chemistry undeniably influences the formation process and performance of Na 3 V 2 (PO 4 ) 3 (NVP) cathodes from in situ insights. By investigating three types of carbonaceous precursors, it is found that O/H-containing functional groups can provide more bonding sites for cathode precursors and generate a reducing atmosphere by pyrolysis, which is beneficial to the formation of polyanionic materials and a uniform carbon coating layer. Conversely, excessive pyrolysis of functional groups leads to a significant amount of gas, which is detrimental to the compactness of the carbon layer. Furthermore, the substantial presence of residual heteroatoms diminishes graphitization. In this case, it is demonstrated that carbon dots (CDs) precursors with suitable functional groups can comprehensively enhance the Na + migration rate, reversibility, and interface stability of the cathode material. As a result, the NVP/CDs cathode displays outstanding capacity retention, maintaining 92% after 10,000 cycles at a high rate of 50 C. Altogether, these findings provide a valuable benchmark for carbon source selection for polyanionic cathodes.

Polycrystalline lithium manganese oxide (LMO) is known to suffer from severe surface structure degradation and electrochemical polarization due to its mixed crystal plane orientations. A hexagonal prism single-crystal LMO (LMOS-HP), engineered through the SrO-induced preferential growth effect, features the most stable {111} top surfaces and the fastest Li + diffusion {110} side surfaces, effectively addressing these challenges. Consequently, LMOS-HP exhibits superior electrochemical capability, with only 0.021% capacity fading per cycle after 500 cycles and achieves a discharge capacity of 81.9 mAh g -1 at 20C. This innovative design offers a promising approach for tuning surface crystal orientation to improve performance.

Al impurity is among the most likely components to enter the spent lithium-ion battery (LIB) cathode powder due to the strong adhesion between the cathode material and the Al current collector. However, high-value metal elements tend to be lost during the deep removal of Al impurities to obtain high-purity metal salt products in the conventional hydrometallurgical process. In this work, the harmful Al impurity is designed as a beneficial ingredient to upcycle high-voltage LiCoO 2 by incorporating robust Al-O covalent bonds into the bulk of the cathode assisted with Ti modification. Benefiting from the strong Al-O and Ti-O bonds in the bulk, the irreversible phase transitions of the upcycled R-LCO-AT have been significantly suppressed at high voltages, as revealed by in situ XRD. Moreover, a Li + -conductive Li 2 TiO 3 protective layer is constructed on the surface of R-LCO-AT by pinning slow-diffusion Ti on the grain boundaries, resulting in improved Li + diffusion kinetics and restrained interface side reactions. Consequently, the cycle stability and rate performance of R-LCO-AT were significantly enhanced at a high cutoff voltage of 4.6 V, with a discharge capacity of 189.5 mAhg -1 at 1 C and capacity retention of 92.9% over 100 cycles at 4.6 V. This study utilizes the detrimental impurity element to upcycle high-voltage LCO cathodes through an elaborate bulk/surface structural design, offering a strategy for the high-value utilization of spent LIBs.

On the basis of the sustainable concept, organic compounds and carbon materials both mainly composed of light C element have been regarded as powerful candidates for advanced electrochemical energy storage (EES) systems, due to theie merits of low cost, eco-friendliness, renewability, and structural versatility. It is investigated that the carbonyl functionality as the most common constituent part serves a crucial role, which manifests respective different mechanisms in the various aspects of EES systems. Notably, a systematical review about the concept and progress for carbonyl chemistry is beneficial for ensuring in-depth comprehending of carbonyl functionality. Hence, a comprehensive review about carbonyl chemistry has been summarized based on state-of-the-art developments. Moreover, the working principles and fundamental properties of the carbonyl unit have been discussed, which has been generalized in three aspects, including redox activity, the interaction effect, and compensation characteristic. Meanwhile, the pivotal characterization technologies have also been illustrated for purposefully studying the related structure, redox mechanism, and electrochemical performance to profitably understand the carbonyl chemistry. Finally, the current challenges and promising directions are concluded, aiming to afford significant guidance for the optimal utilization of carbonyl moiety and propel practicality in EES systems.

Layered sodium transition-metal (TM) oxides generally suffer from severe capacity decay and poor rate performance during cycling, especially at a high state of charge (SoC). Herein, an insight into failure mechanisms within high-voltage layered cathodes is unveiled, while a two-in-one tactic of charge localization and coherent structures is devised to improve structural integrity and Na + transport kinetics, elucidated by density functional theory calculations. Elevated Jahn-Teller [Mn 3+ O 6 ] concentration on the particle surface during sodiation, coupled with intense interlayer repulsion and adverse oxygen instability, leads to irreversible damage to the near-surface structure, as demonstrated by X-ray absorption spectroscopy and in situ characterization techniques. It is further validated that the structural skeleton is substantially strengthened through the electronic structure modulation surrounding oxygen. Furthermore, optimized Na + diffusion is effectively attainable via regulating intergrown structures, successfully achieved by the Zn 2+ inducer. Greatly, good redox reversibility with an initial Coulombic efficiency of 92.6%, impressive rate capability (86.5 mAh g -1 with 70.4% retention at 10C), and enhanced cycling stability (71.6% retention after 300 cycles at 5C) are exhibited in the P2/O3 biphasic cathode. It is believed that a profound comprehension of layered oxides will herald fresh perspectives to develop high-voltage cathode materials for sodium-ion batteries.

Lithium metal batteries (LMBs) offer significant advantages in energy density and output voltage, but they are severely limited by uncontrollable Li dendrite formation resulting from uneven Li + behaviors and high reactivity with potential co-solvent plating. Herein, to uniformly enhance the Li behaviors in desolvation and diffusion, the local Li + solvation shell structure is optimized by constructing an anion-braking separator, hence dynamically reducing the self-amplifying behavior of dendrites. As a prototypal, two-dimensional lithiated-montmorillonite (LiMMT) is blade-coated on the commercial separator, where abundant -OH groups as Lewis acidic sites and electron acceptors could selectively adsorb corresponding FSI - anions, regulating the solvation shell structure and restricting their migration. Meanwhile, the weakened anion mobility delays the time of breaking electrical neutrality, and the Li nucleation density is quantified through the respective experimental, theoretical and spectroscopical results, providing a comprehensive understanding of modifying anion and cation behaviors on dendritic growth suppression. As anticipated, a long Li plating/stripping lifespan up to 1800 h and a significantly increased average Coulombic efficiency of 98.8% are achieved under 3.0 mAh cm -2 . The fabricated high-loading Li-LFP or Li-NCM523 full-cells display the cycle durability with enhanced capacity retention of nearly 100%, providing the instructive guide towards realizing dendrite-free LMBs.

Fluorinated carbon dots (FCDs) have garnered interest owing to their distinct physicochemical properties. Nevertheless, intricate synthesis procedures and quite low fluorine doping levels limit its development and application. Herein, we propose a facile approach based on the Claisen-Schmidt reaction to realize gram-scale synthesis of highly fluorinated carbon dots (up to 20.79 at. %) at room temperature and atmospheric pressure, and a comprehensive exploration of the specific reaction mechanism is conducted. Furthermore, in consideration of the high fluorine content, good dispersibility, and compatibility with polymer electrolyte, the synthesized FCDs are utilized as an additive for PEO-based solid electrolytes of a Li battery to improve its ionic conductivity, interface stability, and mechanical properties. The introduction of FCDs can not only reduce the crystallinity of PEO and enhance the interaction of polymer chains, but also facilitate the establishment of uninterrupted pathways and in situ fluorination at the interface, which is substantiated by both theoretical calculations and experimental findings. As a result, the lithium symmetrical battery can operate stably for 1000 h at a current density of 0.4 mA cm -2 . Simultaneously, the LiFePO 4 /Li battery utilizing the composite electrolyte exhibits a capacity of 130.3 mAh g -1 over 300 cycles while maintaining a capacity retention rate of 95.10%. This study develops a strategy for synthesizing highly fluorinated carbon dots, which demonstrate a useful influence on PEO electrolytes, thus boosting the advancement of FCDs and solid-state batteries.

Further popularization of ultrahigh-Ni layered cathodes for high-energy lithium-ion batteries (LIBs) is hampered by their grievous structural and interfacial degeneration upon cycling. Herein, by leveraging the strong electronegativity and low solubility properties of Sb element, a multifunctional modification that couples atomic/microstructural reconstruction with interfacial shielding is well designed to improve the LiNi 0.94 Co 0.04 Al 0.02 O 2 (NCA) cathode by combining Sb 5+ doping and Li 7 SbO 6 coating. Notably, a robust O framework is established by regulating local O coordination owing to the incorporation of a strong Sb-O covalence bond, leading to the inhibited lattice O evolution at high voltage, as revealed by synchrotron X-ray absorption spectroscopy. Moreover, the radially aligned primary particles with (003) crystallographic texture and refined/elongated sizes are achieved by the pinning of Sb on grain boundaries and are confirmed by scanning transmission electron microscopy, resulting in the fast Li + diffusion and mitigated particle cracking. Additionally, in situ construction of the Li 7 SbO 6 ionic conductive layer on grain boundaries can effectively boost interfacial stability and Li + kinetics. As a result, the optimal Sb-modified NCA delivers a high capacity retention of 94.6% after 200 cycles at 1 C and a good rate capacity of 183.9 mAh g -1 at 10 C, which is expected to be applied to next-generation advanced LIBs.

Na 4 Fe 3 (PO 4 ) 2 (P 2 O 7 ) (NFPP) is an attractive candidate for Na + batteries (SIBs) and Li + batteries (LIBs). However, the real implementation of NFPP has been critically restrained by the inferior intrinsic electronic conductivity. Herein, in situ carbon-coated mesoporous NFPP, obtained via freeze drying and heat treatment, demonstrates highly reversible insertion/extraction of Na + /Li + . Mechanically, the electronic transmission and structural stabilities of NFPP are significantly enhanced by the graphitized carbon coating layer. Chemically, the porous nanosized structure shortens Na + /Li + diffusion paths and increases the contact area between the electrolyte and NFPP, ultimately rendering fast ion diffusion. Greatly, long-lasting cyclability (88.5% capacity retention for over 5000 cycles), decent thermal stability at 60 °C, and impressive electrochemical performances are demonstrated in LIBs. The insertion/extraction mechanisms of NFPP in both SIBs and LIBs are systematically investigated, confirming its small volume expansion and high reversibility. The superior electrochemical performances and the insertion/extraction mechanism investigation confirm the feasibility of utilizing NFPP as a cathode material for Na + /Li + batteries.