2D Exfoliation Chemistry Towards Covalent Pseudo-Layered Phosphate Framework Derived by Radical/Strain-Synergistical Process.

2D compounds exfoliated from weakly bonded bulk materials with van der Waals (vdW) interaction are easily accessible. However, the strong internal ionic/covalent bonding of most inorganic crystal frameworks greatly hinders 2D material exfoliation. Herein, we first proposed a radical/strain-synergistic strategy to exfoliate non-vdW interacting pseudo-layered phosphate framework. Specifically, hydroxyl radicals (•OH) distort the covalent bond irreversibly, meanwhile, H2O molecules as solvents, further accelerating interlayered ionic bond breakage but mechanical expansion. The innovative 2D laminar NASICON-type Na3V2(PO4)2O2F crystal, exfoliated by •OH/H2O synergistic strategy, exhibits enhanced sodium-ion storage capacity, high-rate performance (85.7 mA h g-1 at 20 C), cyclic life (2300 cycles), and ion migration rates, compared with the bulk framework. Importantly, this chemical/physical dual driving technique realized the effective exfoliation for strongly coupled pseudo-layered frameworks, which accelerates 2D functional material development.

Direct and rapid thermal shock for recycling spent graphite in lithium-ion batteries.

Due to the rapid increase in the number of spent lithium-ion batteries, there has been a growing interest in the recovery of degraded graphite. In this work, a rapid thermal shock (RTS) strategy is proposed to regenerate spent graphite for use in lithium-ion batteries. The results of structural and morphological characterization demonstrate that the graphite is well regenerated by the RTS process. Additionally, an amorphous carbon layer forms and coats onto the surface of the graphite, contributing to excellent rate performance. The regenerated graphite (RG-1000) displays excellent rate performance, with capacities of 413 mAh g-1 at 50 mA g-1 and 102.1 mAh g-1 at 1000 mA g-1, respectively. Furthermore, it demonstrates long-term cycle stability, maintaining a capacity of 80 mAh g-1 at 1000 mA g-1 with a capacity retention of 78.4 % after 600 cycles. This RTS method enables rapid and efficient regeneration of spent graphite anodes for lithium-ion batteries, providing a facile and environmentally friendly strategy for their direct regeneration.

Rare earth elements induced electronic engineering in Rh cluster toward efficient alkaline hydrogen evolution reaction.

The unique electronic and crystal structures of rare earth metals (RE) offer promising opportunities for enhancing the hydrogen evolution reaction (HER) properties of materials. In this work, a series of RE (Sm, Nd, Pr and Ho)-doped Rh@NSPC (NSPC stands for N, S co-doped porous carbon nanosheets) with sizes less than 2 nm are prepared, utilizing a simple, rapid and solvent-free joule-heat pyrolysis method for the first time. The optimized Sm-Rh@NSPC achieves HER performance. The high-catalytic performance and stability of Sm-Rh@NSPC are attributed to the synergistic electronic interactions between Sm and Rh clusters, leading to an increase in the electron cloud density of Rh, which promotes the adsorption of H+, the dissociation of Rh-H bonds and the release of H2. Notably, the overpotential of the Sm-Rh@NSPC catalyst is a mere 18.1 mV at current density of 10 mAcm-2, with a Tafel slope of only 15.2 mV dec-1. Furthermore, it exhibits stable operation in a 1.0 M KOH electrolyte at 10 mA cm-2 for more than 100 h. This study provides new insights into the synthesis of composite RE hybrid cluster nanocatalysts and their RE-enhanced electrocatalytic performance. It also introduces fresh perspectives for the development of efficient electrocatalysts.

Defect engineering unveiled: Enhancing potassium storage in expanded graphite anode.

Expanded graphite (EG) stands out as a promising material for the negative electrode in potassium-ion batteries. However, its full potential is hindered by the limited diffusion pathway and storage sites for potassium ions, restricting the improvement of its electrochemical performance. To overcome this challenge, defect engineering emerges as a highly effective strategy to enhance the adsorption and reaction kinetics of potassium ions on electrode materials. This study delves into the specific effectiveness of defects in facilitating potassium storage, exploring the impact of defect-rich structures on dynamic processes. Employing ball milling, we introduce surface defects in EG, uncovering unique effects on its electrochemical behavior. These defects exhibit a remarkable ability to adsorb a significant quantity of potassium ions, facilitating the subsequent intercalation of potassium ions into the graphite structure. Consequently, this process leads to a higher potassium voltage. Furthermore, the generation of a diluted stage compound is more pronounced under high voltage conditions, promoting the progression of multiple stage reactions. Consequently, the EG sample post-ball milling demonstrates a notable capacity of 286.2 mAh g-1 at a current density of 25 mA g-1, showcasing an outstanding rate capability that surpasses that of pristine EG. This research not only highlights the efficacy of defect engineering in carbon materials but also provides unique insights into the specific manifestations of defects on dynamic processes, contributing to the advancement of potassium-ion battery technology.

Homeostatic Solid Solution Reaction in Phosphate Cathode: Breaking High-Voltage Barrier to Achieve High Energy Density and Long Life of Sodium-Ion Batteries.

The stable phase transformation during electrochemical progress drives extensive research on vanadium-based polyanions in sodium-ion batteries (SIBs), especially Na3 V2 (PO4 )3 (NVP). And the electron transfer between V3+/4+ redox couple in NVP could be generally achieved, owing to the confined crystal variation during battery service. However, the more favorable V4+/5+ redox couple is still in hard-to-access situation due to the high barrier and further brings about the corresponding inefficiency in energy densities. In this work, the multilevel redox in NVP frame (MLNP) alters reaction pathway to undergo homeostatic solid solution process and breaks the high barrier of V4+/5+ at high voltage, taking by progressive transition metal (V, Fe, Ti, and Cr) redox couple. The diversified reaction paths across diffusion barriers could be realized by distinctive release/uptake of inactive Na1 site, confirmed by the calculations of density functional theory. Thereby its volume change is merely 1.73% during the multielectron-transfer process (≈2.77 electrons). MLNP cathode could achieve an impressive energy density of 440 Wh kg-1 , driving the leading development of MLNP among other NASICON structure SIBs. The integration of multiple redox couples with low strain modulates the reaction pathway effectively and will open a new avenue for fabricating high-performance cathodes in SIBs.

Hybrid Binder Chemistry with Hydrogen-Bond Helix for High-Voltage Cathode of Sodium-Ion Batteries.

Since sodium-ion batteries (SIBs) have become increasingly commercialized in recent years, Na3V2(PO4)2O2F (NVPOF) offers promising economic potential as a cathode for SIBs because of its high operating voltage and energy density. According to reports, NVPOF performs poorly in normal commercial poly(vinylidene fluoride) (PVDF) binder systems and performs best in combination with aqueous binder. Although in line with the concept of green and sustainable development for future electrode preparation, aqueous binders are challenging to achieve high active material loadings at the electrode level, and their relatively high surface tension tends to cause the active material on the electrode sheet to crack or even peel off from the collector. Herein, a cross-linkable and easily commercial hybrid binder constructed by intermolecular hydrogen bonding (named HPP) has been developed and utilized in an NVPOF system, which enables the generation of a stable cathode electrolyte interphase on the surface of active materials. According to theoretical simulations, the HPP binder enhances electronic/ionic conductivity, which greatly lowers the energy barrier for Na+ migration. Additionally, the strong hydrogen-bond interactions between the HPP binder and NVPOF effectively prevent electrolyte corrosion and transition-metal dissolution, lessen the lattice volume effect, and ensure structural stability during cycling. The HPP-based NVPOF offers considerably improved rate capability and cycling performance, benefiting from these benefits. This comprehensive binder can be extended to the development of next-generation energy storage technologies with superior performance.

"Pore-Hopping" Ion Transport in Cellulose-Based Separator Towards High-Performance Sodium-Ion Batteries.

Sodium-ion batteries (SIBs) have great potential for large-scale energy storage. Cellulose is an attractive material for sustainable separators, but some key issues still exist affecting its application. Herein, a cellulose-based composite separator (CP@PPC) was prepared by immersion curing of cellulose-based separators (CP) with poly(propylene carbonate) (PPC). With the assistance of PPC, the CP@PPC separator is able to operate the cell stably at high voltages (up to 4.95 V). The "pore-hopping" ion transport mechanism in CP@PPC opens up extra Na+ migration paths, resulting in a high Na+ transference number (0.613). The separator can also tolerate folding, bending and extreme temperature under certain circumstances. Full cells with CP@PPC reveal one-up capacity retention (96.97 %) at 2C after 500 cycles compared to cells with CP. The mechanism highlights the merits of electrolyte analogs in separator modification, making a rational design for durable devices in advanced energy storage systems.