Interface optimization mechanism and quantitative analysis of hybrid graphite anode for fast-charging lithium-ion batteries.

Due to the inherent characteristics of traditional graphite anode material, its lithium diffusion kinetic is significantly constrained, easily leading to a noticeable capacity degradation during rapid charge/discharge cycling. Although modifying the graphite by mixing the hard carbon can effectively enhance its fast-charging performance, yet the underlying mechanism of improvement effect and structure design of interface are still needed to further investigate. To address this research gap, hard carbon-coated graphite (HCCG) material has been designed and synthesized through simple interface engineering, which is aimed to explore and elucidate the optimization mechanisms on fast-charging performance from the graphite interface perspective. According to the electrochemical calculations, the HCCG anode exhibits significant enhancements. Specially, its reversible lithium content is increased by approximately 8 % at various states of charge, its exchange current density is tripled, and its Tafel slope is reduced to one-quarter of the original graphite. Therefore, the HCCG maintains an impressive 86.89 % capacity retention and a high capacity of 202.3 mAh g-1 after 1450 cycles at ultrahigh rate of 5C. These improvements indicate a substantial reduction in electrode polarization during fast charging, which is ascribed to the abundant lithium intercalation pathways and accommodation space provided by the intimate hard carbon coating layer. Moreover, as a "buffer layer," hard carbon coating can accommodate considerable amount of lithium deposited on the graphite surface, effectively mitigating the capacity loss caused by lithium deposition and maintaining effective electrochemical contact without delamination. This comprehensive analysis of hard carbon coating illustrates the improvement mechanism of fast-charging performance, which can offer valuable insights into the dynamic and structural optimization of graphite anode interfaces.

Alleviating the volume expansion of silicon anodes by constructing a high-strength ordered multidimensional encapsulation structure.

The application of silicon-based nanomaterials in fast-charging scenarios is hindered by volume expansion during lithiation and side reactions induced by surface effects. Constructing a robust encapsulation structure with high mechanical strength and conductivity is pivotal for optimizing the electrochemical performance of nanostructured silicon anodes. Herein, we propose a multifaceted hierarchical encapsulation structure featuring excellent mechanical strength and high conductivity by sequentially incorporating SiO x , hard carbon, and closed-pore carbon layers around silicon quantum dots, thereby enabling stable cycling at high current densities. In this structure, the ultra-thin SiO x layer strengthens the Si-C interface, while the outermost carbon matrix with closed pores functions both as a conductive network and a barrier against electrolyte intrusion. Notably, the synthesized material exhibits a specific capacity of 1506 mA h g-1 with 90.17% retention after 300 cycles at 1.0 A g-1. After 500 cycles at 5.0 A g-1, it retains 640.4 mA h g-1, over 70% of its initial capacity.

Interfacial Robustness and Improved Kinetics of Single-Crystal Ni-Rich Co-Free Cathodes Enabled by Surface Crystal-Facet Modulation.

The elimination of Co from Ni-rich layered cathodes is critical to reduce the production cost and increase the energy density for sustainable development. Herein, a delicate strategy of crystal-facet modulation is designed and explored, which is achieved by simultaneous Al/W-doping into the precursors, while the surface role of the crystal-facet is intensively revealed. Unlike traditional studies on crystal structure growth along a certain direction, this work modulates the crystal-facet at the nanoscale based on the effect of W-doping dynamic migration with surface energy, successfully constructing the core-shell (003)/(104) facet surface. Compared to the (003) plane, the induced (104) facet at the surface can provide more space for Li+-activity, enabling lower interfacial polarization and higher Li+-transport rate. Additionally, bulk Al-doping is beneficial for enhancing the Li+-diffusion from the exterior surface to the interior lattice. With improved interfacial stability and restrained surface erosion, the product exhibits superior capacity retention and boosted rate performance under the elevated temperature.

Push-Pull Electrolyte Design Strategy Enables High-Voltage Low-Temperature Lithium Metal Batteries.

Lithium (Li) metal batteries hold significant promise in elevating energy density, yet their performance at ultralow temperatures remains constrained by sluggish charge transport kinetics and the formation of unstable interphases. In conventional electrolyte systems, lithium ions are tightly locked in the solvation structure, thereby engendering difficulty in the desolvation process and further exacerbating solvent decomposition. Herein, we propose a new push-pull electrolyte design strategy, utilizing molecular electrostatic potential (ESP) screening to identify 2,2-difluoroethyl trifluoromethanesulfonate (DTF) as an optimal cosolvent. Importantly, DTF exhibits a moderate ESP minimum (-21.0 kcal mol-1) to strike a balance between overly strong and overly weak Li ion affinity, which allows the sulfonyl group to effectively pull Li ions without disrupting the anion-rich solvation structure. Simultaneously, the difluoromethyl group, with a high ESP maximum (37.3 kcal mol-1), pushes solvent molecules via competitive hydrogen bonding. This design reconstructs existing solvation structures and expedites Li ion desolvation. Furthermore, fluorinated DTF demonstrates excellent stability at elevated voltage and facilitates the formation of robust inorganic-rich interphases. Impressively, rapid charge transfer kinetics can be achieved employing designed electrolyte, and the LiNi0.8Mn0.1Co0.1O2 (NMC811)||Li cells demonstrate excellent charge-discharge cycling stability with a high capacity exceeding 153 mAh g-1 even at -40 °C, retaining over 93% of initial capacity after 100 cycles under a 4.8 V charging cutoff. This work provides insights into the design of low-temperature electrolytes with a wide electrochemical window, advancing the development of batteries for extreme conditions.

Low-temperature de-alloying and unique self-filling interface optimization mechanism of layered silicon for enhanced lithium storage.

Layered silicon (L-Si) anodes are celebrated for their high theoretical capacity but face significant challenges regarding safety and material purity during preparation. This study addresses these challenges by employing NH4Cl-CaSi2 as the raw material in a gas-solid de-alloying process, which enhances both safety and purity compared to traditional methods. The L-Si anodes produced demonstrate outstanding electrochemical performance, delivering a high reversible lithium storage capacity of 1497.7 mA h g-1 at a current density of 0.5 A g-1, and exhibiting stable performance over 1200 charge-discharge cycles. In situ and ex situ characterizations reveal that electrolyte decomposition products effectively fill the voids within the electrode, while the gradual disintegration of the L-Si structure contributes to the formation of a dense, conductive network. This process enhances lithium ion transport and exploits the capacitive storage benefits of layered silicon.

Gel Polymer Electrolyte Enables Low-Temperature and High-Rate Lithium-Ion Batteries via Bionic Interface Design.

Traditional ethylene carbonate (EC)-based electrolytes constrain the applications of silicon carbon (Si-C) anodes under fast-charging and low-temperature conditions due to sluggish Li+ migration kinetics and unstable solid electrolyte interphase (SEI). Herein, inspired by the efficient water purification and soil stabilization of aquatic plants, a stable SEI with a 3D desolvation interface is designed with gel polymer electrolyte (GPE), accelerating Li+ desolvation and migration at the interface and within stable SEI. As demonstrated by theoretical simulations and experiment results, the resulting poly(1,3-dioxolane) (PDOL), prepared by in situ ring-opening polymerization of 1,3-dioxolane (DOL), creates a 3D desolvation area, improving the Li+ desolvation at the interface and yielding an amorphous GPE with a high Li+ ionic conductivity (5.73 mS cm-1). Furthermore, more anions participate in the solvated structure, forming an anion-derived stable SEI and improving Li+ transport through SEI. Consequently, the Si-C anode achieves excellent rate performance with GPE at room temperature (RT) and low temperature (-40 °C). The pouch full cell coupled with LiFePO4 cathode obtains 97.42 mAh g-1 after 500 cycles at 5 C/5 C. This innovatively designed 3D desolvation interface and SEI represent significant breakthroughs for developing fast-charging and low-temperature batteries.

Strengthening the interfacial stability of single-crystal LiNi0.88Co0.09Mn0.03O2 cathode with multiple-function surface modification.

The instability in the structural integrity caused by interfacial issues is commonly regarded as the primary drawback of Ni-rich layered cathode materials (LiNixCoyMn1-x-yO2, where x  ≥ 0.8), which must be addressed before their commercial application. Herein, a novel multiple-function surface modification strategy is proposed based on the single crystal structure to in-situ achieve the construction of a coating layer and surface doping with Ce element to enhance the structural stability of the LiNi0.88Co0.09Mn0.03O2 (NCM). Notably, the introduction of Ce-O bonding adjusts the local oxygen coordination to achieve a more stabilized structure of the oxygen framework, which inhibits the evolution of lattice oxygen and enhances conductivity. Additionally, by benefiting from the in-situ synthesized coating layer of LixCeO2, the occurrence of side reactions on the surface is effectively alleviated, resulting in a reduction in electrode polarization. Combined with comprehensive electrochemical tests, it is confirmed that the improved electrochemical performance originates from the reduction of the detrimental H2-H3 phase transition and enhanced conductivity. As expected, the modified material with 1 wt% content of Ce (NCM@Ce) exhibits a high initial discharge capacity of 196.3 mAh g-1 with a capacity retention of 79.7 % after 200 cycles, and its energy density reaches 574.3 Wh kg-1 after 200 cycles.

Molecular anchoring of free solvents for high-voltage and high-safety lithium metal batteries.

Constraining the electrochemical reactivity of free solvent molecules is pivotal for developing high-voltage lithium metal batteries, especially for ether solvents with high Li metal compatibility but low oxidation stability ( <4.0 V vs Li+/Li). The typical high concentration electrolyte approach relies on nearly saturated Li+ coordination to ether molecules, which is confronted with severe side reactions under high voltages ( >4.4 V) and extensive exothermic reactions between Li metal and reactive anions. Herein, we propose a molecular anchoring approach to restrict the interfacial reactivity of free ether solvents in diluted electrolytes. The hydrogen-bonding interactions from the anchoring solvent effectively suppress excessive ether side reactions and enhances the stability of nickel rich cathodes at 4.7 V, despite the extremely low Li+/ether molar ratio (1:9) and the absence of typical anion-derived interphase. Furthermore, the exothermic processes under thermal abuse conditions are mitigated due to the reduced reactivity of anions, which effectively postpones the battery thermal runaway.

Optimized In Situ Doping Strategy Stabling Single-Crystal Ultrahigh-Nickel Layered Cathode Materials.

Single-crystal Ni-rich cathodes offer promising prospects in mitigating intergranular microcracks and side reaction issues commonly encountered in conventional polycrystalline cathodes. However, the utilization of micrometer-sized single-crystal particles has raised concerns about sluggish Li+ diffusion kinetics and unfavorable structural degradation, particularly in high Ni content cathodes. Herein, we present an innovative in situ doping strategy to regulate the dominant growth of characteristic planes in the single-crystal precursor, leading to enhanced mechanical properties and effectively tackling the challenges posed by ultrahigh-nickel layered cathodes. Compared with the traditional dry-doping method, our in situ doping approach possesses a more homogeneous and consistent modifying effect from the inside out, ensuring the uniform distribution of doping ions with large radius (Nb, Zr, W, etc). This mitigates the generally unsatisfactory substitution effect, thereby minimizing undesirable coating layers induced by different solubilities during the calcination process. Additionally, the uniformly dispersed ions from this in situ doping are beneficial for alleviating the two-phase coexistence of H2/H3 and optimizing the Li+ concentration gradient during cycling, thus inhibiting the formation of intragranular cracks and interfacial deterioration. Consequently, the in situ doped cathodes demonstrate exceptional cycle retention and rate performance under various harsh testing conditions. Our optimized in situ doping strategy not only expands the application prospects of elemental doping but also offers a promising research direction for developing high-energy-density single-crystal cathodes with extended lifetime.

Anionic Sublattices in Halide Solid Electrolytes: A Case Study with the High-Pressure Phase of Li3ScCl6.

The Li3MX6 compounds (M=Sc, Y, In; X=Cl, Br) are known as promising ionic conductors due to their compatibility with typical metal oxide cathode materials. In this study, we have successfully synthesized γ-Li3ScCl6 using high pressure for the first time in this family. Structural analysis revealed that the high-pressure polymorph crystallizes in the polar and chiral space group P63mc with hexagonal close-packing (hcp) of anions, unlike the ambient-pressure α-Li3ScCl6 and its spinel analog with cubic closed packing (ccp) of anions. Investigation of the known Li3MX6 family further revealed that the cation/anion radius ratio, rM/rX, is the factor that determines which anion sublattice is formed and that in γ-Li3ScCl6, the difference in compressibility between Sc and Cl exceeds the ccp rM/rX threshold under pressure, enabling the ccp-to-hcp conversion. Electrochemical tests of γ-Li3ScCl6 demonstrate improved electrochemical reduction stability. These findings open up new avenues and design principles for lithium solid electrolytes, enabling routes for materials exploration and tuning electrochemical stability without compositional changes or the use of coatings.

Constructing an Anion-Braking Separator to Regulate Local Li+ Solvation Structure for Stabilizing Lithium Metal 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.

Strong Oxidizing Molten Salts for Strengthening Structural Restoration Enabling Direct Regeneration of Spent Layered Cathode.

As a mainstream technology for recycling spent lithium-ion batteries, direct regeneration is rapidly developed due to its high efficiency and green characteristics. However, efficient reuse of spent LiNixCoyMn1- x - yO2 cathode is still a significant challenge, as the rock salt/spinel phase on the surface hinders the Li replenishment and phase transformation to the layered structure. In this work, the fundamental understanding of the repair mechanism is confirmed that the oxidizing atmosphere is the crucial factor that can greatly improve the rate and degree of phase restoration. Particularly, a ternary-component molten salt system (LiOH-Li2CO3-LiNO3) is proposed for direct regeneration of LiNi0.5Co0.2Mn0.3O2 (NCM523), which can in situ generate the strong oxidizing intermediate of superoxide radicals. Additionally, it shows a liquid-like reaction environment at a lower temperature to acceclerate the transport rate of superoxide-ions. Therefore, the synergistic effect of LiOH-Li2CO3-LiNO3 system can strengthen the full restoration of rock salt/spinel phases and achieve the complete Li-supplement. As anticipated, the regenerated NCM523 delivers a high cycling stability with a retention of 91.7% after 100 cycles, which is even competitive with the commercial NCM523. This strategy provides a facile approach for the complete recovery of layer structure cathode, demonstrating a unique perspective for the direct regeneration of spent lithium-ion batteries.

Amorphous Aluminum Oxide-Coated NaFe0.33Ni0.33Mn0.33O2 Cathode Materials: Enhancing Interface Charge Transfer for High-Performance Sodium-Ion Batteries.

Layered cathode materials for sodium-ion batteries (SIBs) have gained considerable attention as promising candidates owing to their high capacity and potential for industrial scalability. Nonetheless, challenges arise from stress and structural degradation resulting from the deposition of larger ion radius species, leading to diminished cyclic stability and rate performance. In this study, we present a novel and straightforward strategy that combines the synergistic effects of an amorphous aluminum oxide coating and aluminum ion doping. This approach effectively addresses the issues of grain cracking and expands the interlayer spacing of alkali metal ions in SIB materials, thereby enhancing their overall performance. Consequently, it optimizes the diffusion of charge carriers and facilitates interfacial charge transfer, leading to remarkable improvements in the performance of the NaNi0.33Mn0.33Fe0.33O2 material with 0.4 wt % amorphous aluminum oxide coating (NNMF-0.4A), which exhibits reversible capacities of 135.7, 114.3, 106.8, 99.9, 89.5, and 77.1 mAh g-1 at 0.1, 0.5, 1, 2, 5, and 10 C, respectively. Furthermore, the NNMF-0.4A material maintains a capacity of 76.7 mA g-1 after 500 cycles at a current density of 800 mA g-1 (10 C), with a capacity retention rate of 98.2%. Our findings present a groundbreaking pathway for modifying high-power sodium-ion battery cathode materials, contributing to the advancement of sustainable energy storage technologies.

High-performance expanded graphite regenerated from spent lithium-ion batteries by integrated oxidation and purification method.

Currently, the recycling of spent lithium-ion batteries (LIBs) has mainly been focused on the extraction of precious metals, such as lithium, cobalt and nickel from cathodes, while the waste graphite anode has been overlooked due to its low-cost production and abundant resources reserve. However, there are enormous potential value and pollution risk in the view of graphite recycling. Thus, we propose an original method to prepare expanded graphite (EG) as new anode material generated from waste graphite in LIBs which integrates the oxidation and purification in one-step. By regulating the oxidizability of potassium hypermanganate in the sulfur-phosphorus mixed acid system, the expansion of graphite and removal of impurities are realized simultaneously and thoroughly. As anticipated, the shortening of preparation process and purification procedure can also reduce the generation of polluting substances and production cost. It displays excellent electrochemical performance (reversible capacity of 435.8 mAh·g-1 at 0.1C and long-term cycling property of 370 mAh·g-1 at 1C after 1000 cycles), which is even higher than that of pristine commercial graphite. This delicate strategy of high-performance expanded graphite recycling achieves the integration of purification and value-added processes, providing the instructive guide to regenerate industrial-grade anode materials for the increasing LIBs demand in the future.

Cobalt/aluminum co-substitution in a LiNi0.9Mn0.1O2 layered cathode for improving kinetics.

We report the improved kinetic mechanism of a nickel-rich LiNi0.84Mn0.10Co0.03Al0.03O2 cathode. The important role of Co/Al in inhibiting cation disorder to increase the lithium ion diffusion rate is revealed. Impressively, it retains an excellent capacity retention of 76.8% after 200 cycles under the high-rate condition (5C).

Effect of ice popsicle treatment on emergence agitation in children undergoing oral surgery with sevoflurane anaesthesia: A prospective randomized controlled study.

PURPOSE: Emergence agitation is a common postoperative complication during recovery in children. The purpose of this study is to explore whether the use of ice popsicle could prevent emergence agitation in children undergoing oral surgery with sevoflurane anaesthesia. DESIGN AND METHODS: In this prospective randomized controlled study, 100 children undergoing oral surgery were randomly assigned to Group 1 which received ice popsicle after emergence (intervention, n = 50) or Group 2 which received verbal encouragement from their parents (control, n = 50). The primary outcome was the 2-hour postoperative incidence of EA. RESULTS: Group 1 had a significant lower incidence of emergence agitation (22% vs 58%, P < 0.001) compared with Group 2. The mean agitation score was significantly lower in Group 1 vs Group 2 at 10  minutes (1.64 vs 2.12, P = 0.024) and 20 min (1.60 vs 2.14, P = 0.004) after emergence. The peak agitation and pain scores were significantly lower in Group 1 than in Group 2 (P < 0.001). CONCLUSIONS: Findings from this study suggest that ice popsicle is an effective, cheap, pleasurable, and easily administered method for alleviating emergence agitation in paediatric patients after oral surgery under general anaesthesia. These results are worthy of confirmation in other surgeries. PRACTICE IMPLICATIONS: This approach is highly accepted by both children and their parents, and our findings support the effectiveness of ice popsicle in relieving emergence agitation and pain after oral surgery in children. CLINICAL TRIALS REGISTRATION: Chinese Clinical Trial Registry, ChiCTR1800015634.

Effect of fermentation on structural properties and antioxidant activity of wheat gluten by Bacillus subtilis.

Bacillus subtilis has been extensively studied for its ability to inhibit the growth of harmful microorganisms and its high protease activity. In this study, Bacillus subtilis was used to ferment gluten and assess the effects of the fermentation process on the physicochemical, microstructure and antioxidant properties of gluten. The results of Fourier infrared spectroscopy (FT-IR) and circular chromatography (CD) showed a significant decrease in the content of α-helix structures and a significant increase in the content of ß-sheet structures in gluten after fermentation (p < 0.05). Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) showed that glutenin was degraded into small molecular peptides with a molecular weight of less than 26 kDa after 24 h of fermentation; meanwhile, the fermentation process significantly increased the free amino acid content of the samples (p < 0.05), reaching 1923.38 µg/mL at 120 h of fermentation, which was 39.46 times higher than that at 24 h of fermentation (p < 0.05). In addition, the fermented back gluten has higher free radical scavenging activity and iron reduction capacity. Therefore, fermented gluten may be used as a functional food to alleviate oxidative stress. This study provides a reference for the high-value application of gluten.

In-situ catalytic mechanism coupling quantum dot effect for achieving high-performance sulfide anode in potassium-ion batteries.

Though numerous framework structures have been constructed to strengthen the reaction kinetics and durability, the inevitable generation of polysulfide dissolution during conversion-process can cause irreparable destruction to ion-channel and crystal structure integrality, which has become a huge obstacle to the application of metal-sulfide in potassium-ion batteries. Herein, the quantum dot structure with catalytic conversion capability is synchronously introduced into the design of FeS2 anode materials to heighten its K+-storage performance. The constructed quantum dot structure anchored by the graphene with space-confinement effect can shorten the ion diffusion path and enlarge the active area, thus accelerating the K+-ions transmission kinetics and absorption action, respectively. The intermediate phase of formed Fe-nanoclusters possesses high-active catalysis ability, which can effectively suppress the polysulfide shuttle combined with the enhanced absorption effect, fully guaranteeing the structure stability and cycling reversibility. Predictably, the fabricated quantum dot FeS2 can express a prominent advantage in rapid potassiation/depotassiation processes (518.1 mAh g-1, 10 A g-1) and a superior cycling lifespan with gratifying reversible capacity at superhigh rate (177.7 mAh g-1, 9000 cycles, 5 A g-1). Therefore, engineering quantum dot structure with self-induced catalysis action for detrimental polysulfide is an achievable strategy to implement high-performance sulfide anode materials for K-ions accommodation.

Synergistic regulation of kinetic reaction pathway and surface structure degradation in single-crystal high-nickel cathodes.

As a promising high energy density cathode, single-crystal Ni-rich cathode face poor diffusion dynamics, which leads to poor structural evolution, poor cyclic stability and unfavorable rate performance, thus impeding its wider application. Herein, the strategy of synergistic surface modification by ionic conductor coating and trace element doping is delicately designed. The surface protective Li3BO3 layer is wrapped on the single-crystal LiNi0.83Co0.11Mn0.06O2 (NCM83), which can improve the compatibility of cathode/electrolyte with reduced interface resistance. While Zr is incorporated into bulk to stabilize the crystal structure and migration channel. This synergistic strategy achieves the improvement of ionic transport and structural stability of single-crystal NCM83 (Zr-NCM83@B) from the outer surface to the inner body. As expected, the modified cathode Zr-NCM83@B demonstrates a satisfying electrochemical performance. It delivers a high reversible capacity of 169 mAh g-1 in coin-type half-cell at 4C within 3.0-4.3 V. Remarkably, it displays excellent capacity retention of 83.5 % in Zr-NCM83@B || graphite pouch-type full-cell over 1400 cycles at 1C with high voltage range of 2.8-4.4 V. This synergistic surface modification provides a reference for commercial development of advanced single-crystal Ni-rich cathode under harsh testing conditions.

Designed graphite with an activated edge for fast-charging lithium-ion storage properties.

Graphite with an activated edge is carefully designed via a controllable solution treatment and sintering process. The simultaneous existence of extra active sites and expanded layers at the edge enable it to exhibit excellent fast-charging performance in a half-cell and full-cell set-up. This work highlights an overall understanding of polarization and the optimum structure for a fast-charging anode.