New Insights into Anionic Redox in P2-Type Oxide Cathodes for Sodium-Ion Batteries.

Manganese/nickel-based layered transition metal oxides have caught the attention of studies as promising cathodes for sodium-ion batteries (SIBs). It is reported that utilizing both cationic and anionic redox reactions is a promising method for higher energy density cathodes. However, the anionic redox reaction comes at the expense of irreversible oxygen release. Hence, a Li-Mg cosubstituted P2-Na0.67Li0.07Mg0.07Ni0.28Mn0.58O2 material with a honeycomb-ordered superstructure was designed. The Ni3+/Ni4+ redox couple and the anionic redox reaction are proven to have a competitive relationship. Density functional theory calculations reveal the effect of O 2p nonbonding states from Li and prove that Mg-O bonds can stabilize the Ni-O eg states. In situ electrochemical impedance spectroscopy measurements and galvanostatic charging/discharging derived dV/dQ, representing resistance changes with time, are obtained to reveal the mechanism of the anionic redox reaction. This study presents the effect and mechanism of the O 2p nonbonding state and Mg-O bonds of manganese/nickel-based layered oxides.

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.

Lithium Orbital Hybridization Chemistry to Stimulate Oxygen Redox with Reversible Phase Evolution in Sodium-Layered Oxide Cathodes.

Searching for high energy-density electrode materials for sodium ion batteries has revealed Na-deficient intercalation compounds with lattice oxygen redox as promising high-capacity cathodes. However, anionic redox reactions commonly encountered poor electrochemical reversibility and unfavorable structural transformations during dynamic (de)sodiation processes. To address this issue, we employed lithium orbital hybridization chemistry to create Na-O-Li configuration in a prototype P2-layered Na43/60Li1/20Mg7/60Cu1/6Mn2/3O2 (P2-NaLMCM') cathode material. That Li+ ions, having low electronegativity, reside in the transition metal slabs serves to stimulate unhybridized O 2p orbitals to facilitate the stable capacity contribution of oxygen redox at high state of charge. The prismatic-type structure evolving to an intergrowth structure of the Z phase at high charging state could be simultaneously alleviated by reducing the electrostatic repulsion of O-O layers. As a consequence, P2-NaLMCM' delivers a high specific capacity of 183.8 mAh g-1 at 0.05 C and good cycling stability with a capacity retention of 80.2% over 200 cycles within the voltage range of 2.0-4.5 V. Our findings provide new insights into both tailoring oxygen redox chemistry and stabilizing dynamic structural evolution for high-energy battery cathode materials.

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 mAh 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.

Nanodesigns for Na3V2(PO4)3-based cathode in sodium-ion batteries: a topical review.

With the rapid development of sodium-ion batteries (SIBs), it is urgent to exploit the cathode materials with good rate capability, attractive high energy density and considerable long cycle performance. Na3V2(PO4)3(NVP), as a NASICON-type electrode material, is one of the cathode materials with great potential for application because of its good thermal stability and stable. However, NVP has the inherent problem of low electronic conductivity, and various strategies are proposed to improve it, moreover, nanotechnology or nanostructure are involved in these strategies, the construction of nanostructured active particles and nanocomposites with conductive carbon networks have been shown to be effective in improving the electrical conductivity of NVP. Herein, we review the research progress of NVP performance improvement strategies from the perspective of nanostructures and classifies the prepared nanomaterials according to their different nano-dimension. In addition, NVP nanocomposites are reviewed in terms of both preparation methods and promotion effects, and examples of NVP nanocomposites at different nano-dimension are given. Finally, some personal views are presented to provide reasonable guidance for the research and design of high-performance polyanionic cathode materials of SIBs.

Advanced Lithium Primary Batteries: Key Materials, Research Progresses and Challenges.

In recent years, with the vigorous development and gradual deployment of new energy vehicles, more attention has been paid to the research on lithium-ion batteries (LIBs). Compared with the booming LIBs, lithium primary batteries (LPBs) own superiority in specific energy and self-discharge rate and are usually applied in special fields such as medical implantation, aerospace, and military. Widespread application in special fields also means more stringent requirements for LPBs in terms of energy density, working temperature range and shelf life. Therefore, how to obtain LPBs with high energy density, wide operational temperature range and long storage life is of great importance in future development. In view of the above, this paper reviews the latest research on LPBs in cathode, anode and electrolyte over the years, and puts forward relevant insights for LPBs, along with the intention to explore avenues for the design of LPBs components in the coming decades and promote further development in this field.

Aliovalent-Ion-Induced Lattice Regulation Based on Charge Balance Theory: Advanced Fluorophosphate Cathode for Sodium-Ion Full Batteries.

There are still many problems that hinder the development of sodium-ion batteries (SIBs), including poor rate performance, short-term cycle lifespan, and inferior low-temperature property. Herein, excellent Na-storage performance in fluorophosphate (Na3 V2 (PO4 )2 F3 ) cathode is achieved by lattice regulation based on charge balance theory. Lattice regulation of aliovalent Mn2+ for V3+ increases both electronic conductivity and Na+ -migration kinetics. Because of the maintaining of electrical neutrality in the material, aliovalent Mn2+ -introduced leads to the coexistence of V3+ and V4+ from charge balance theory. It decreases the particle size and improves the structural stability, suppressing the large lattice distortion during cathode reaction processes. These multiple effects enhance the specific capacity (123.8 mAh g-1 ), outstanding high-rate (68% capacity retention at 20 C), ultralong cycle (only 0.018% capacity attenuation per cycle over 1000 cycles at 1 C) and low-temperature (96.5% capacity retention after 400 cycles at -25 °C) performances of Mn2+ -induced Na3 V1.98 Mn0.02 (PO4 )2 F3 when used as cathode in SIBs. Importantly, a feasible sodium-ion full battery is assembled, achieving outstanding rate capability and cycle stability. The strategy of aliovalent ion-induced lattice regulation constructs cathode materials with superior performances, which is available to improve other electrode materials for energy storage systems.

Ether-Based Electrolyte Chemistry Towards High-Voltage and Long-Life Na-Ion Full Batteries.

Although ether-based electrolytes have been extensively applied in anode evaluation of batteries, anodic instability arising from solvent oxidability is always a tremendous obstacle to matching with high-voltage cathodes. Herein, by rational design for solvation configuration, the fully coordinated ether-based electrolyte with strong resistance against oxidation is reported, which remains anodically stable with high-voltage Na3 V2 (PO4 )2 O2 F (NVPF) cathode under 4.5 V (versus Na+ /Na) protected by an effective interphase. The assembled graphite//NVPF full cells display superior rate performance and unprecedented cycling stability. Beyond that, the constructed full cells coupling the high-voltage NVPF cathode with hard carbon anode exhibit outstanding electrochemical performances in terms of high average output voltage up to 3.72 V, long-term cycle life (such as 95 % capacity retention after 700 cycles) and high energy density (247 Wh kg-1 ). In short, the optimized ether-based electrolyte enriches systematic options, the ability to maintain oxidative stability and compatibility with various anodes, exhibiting attractive prospects for application.

Isostructural and Multivalent Anion Substitution toward Improved Phosphate Cathode Materials for Sodium-Ion Batteries.

Polyanion-type phosphate materials are highly promising cathode candidates for next-generation batteries due to their excellent structural stability during cycling; however, their poor conductivity has impeded their development. Isostructural and multivalent anion substitution combined with carbon coating is proposed to greatly improve the electrochemical properties of phosphate cathode in sodium-ion batteries (SIBs). Specifically, multivalent tetrahedral SiO4 4- substitute for PO4 3- in Na3 V2 (PO4 )3 (NVP) lattice, preparing the optimal Na3.1 V2 (PO4 )2.9 (SiO4 )0.1 with high-rate capability (delivering a high capacity of 82.5 mAh g-1 even at 20 C) and outstanding cyclic stability (≈98% capacity retention after 500 cycles at 1 C). Theoretical calculation and experimental analyses reveal that the anion-substituted Na3.1 V2 (PO4 )2.9 (SiO4 )0.1 reduces the bandgap of NVP lattice and enhanced its structural stability, Na+ -diffusion kinetics and electronic conductivity. This strategy of multivalent and isostructural anion substitution chemistry provides a new insight to develop advanced phosphate cathodes.

Temperature-Dependent Electrochemical Properties and Electrode Kinetics of Na3 V2 (PO4 )2 O2 F Cathode for Sodium-Ion Batteries with High Energy Density.

Phosphate cathode materials are practical for use in sodium-ion batteries (SIBs) owing to their high stability and long-term cycle life. In this work, the temperature-dependent properties of the phosphate cathode Na3 V2 (PO4 )2 O2 F (NVPOF) are studied in a wide temperature range from -25 to 55 °C. Upon cycling at general temperature (above 0 °C), the NVPOF cathode retains an excellent charge/discharge performance, and the rate capability is noteworthy, indicating that NVPOF is a competitive candidate as a temperature-adaptive cathode for SIBs. Upon decreasing the temperature below 0 °C, the cell performance deteriorates, which may be caused by the electrolyte and Na electrode, based on the study of ionic conductivity and electrode kinetics. This work proposes a new breakthrough point for the development of SIBs with high performance over a wide temperature range for advanced power systems.

Alkali-Metal-Ion-Functionalized Graphene Oxide as a Superior Anode Material for Sodium-Ion Batteries.

Although graphene oxide (GO) has large interlayer spacing, it is still inappropriate to use it as an anode for sodium-ion batteries (SIBs) because of the existence of H-bonding between the layers and ultralow electrical conductivity which impedes the Na(+) and e(-) transformation. To solve these issues, chemical, thermal, and electrochemical procedures are traditionally employed to reduce GO nanosheets. However, these strategies are still unscalable, consume high amounts of energy, and are expensive for practical application. Here, for the first time, we describe the superior Na storage of unreduced GO by a simple and scalable alkali-metal-ion (Li(+) , Na(+) , K(+) )-functionalized process. The various alkali metals ions, connecting with the oxygen on GO, have played different effects on morphology, porosity, degree of disorder, and electrical conductivity, which are crucial for Na-storage capabilities. Electrochemical tests demonstrated that sodium-ion-functionalized GO (GNa) has shown outstanding Na-storage performance in terms of excellent rate capability and long-term cycle life (110 mAh g(-1) after 600 cycles at 1 A g(-1) ) owing to its high BET area, appropriate mesopore, high degree of disorder, and improved electrical conductivity. Theoretical calculations were performed using the generalized gradient approximation (GGA) to further study the Na-storage capabilities of functionalized GO. These calculations have indicated that the Na-O bond has the lowest binding energy, which is beneficial to insertion/extraction of the sodium ion, hence the GNa has shown the best Na-storage properties among all comparatives functionalized by other alkali metal ions.

A Superior Na3 V2 (PO4 )3 -Based Nanocomposite Enhanced by Both N-Doped Coating Carbon and Graphene as the Cathode for Sodium-Ion Batteries.

A superior Na3 V2 (PO4 )3 -based nanocomposite (NVP/C/rGO) has been successfully developed by a facile carbothermal reduction method using one most-common chelator, disodium ethylenediamintetraacetate [Na2 (C10 H16 N2 O8 )], as both sodium and nitrogen-doped carbon sources for the first time. 2D-reduced graphene oxide (rGO) nanosheets are also employed as highly conductive additives to facilitate the electrical conductivity and limit the growth of NVP nanoparticles. When used as the cathode material for sodium-ion batteries, the NVP/C/rGO nanocomposite exhibits the highest discharge capacity, the best high-rate capabilities and prolonged cycling life compared to the pristine NVP and single-carbon-modified NVP/C. Specifically, the 0.1 C discharge capacity delivered by the NVP/C/rGO is 116.8 mAh g(-1) , which is obviously higher than 106 and 112.3 mAh g(-1) for the NVP/C and pristine NVP respectively; it can still deliver a specific capacity of about 80 mAh g(-1) even at a high rate up to 30 C; and its capacity decay is as low as 0.0355 % per cycle when cycled at 0.2 C. Furthermore, the electrochemical impedance spectroscopy was also implemented to compare the electrode kinetics of all three NVP-based cathodes including the apparent Na diffusion coefficients and charge-transfer resistances.

[Chemical constituents from Dichotella gemmacea].

OBJECTIVE: To study the chemical constituents from Dichotella gemmacea. METHODS: Chemical constituents were isolated by silica gel and Sephadex LH-20 column chromatography. The structures of the isolated compounds were elucidated through spectroscopic analysis. RESULTS: Eight compounds were identified as fragilide J(I), junceelldide D(II), junceellin A (IlI), juncin P(IV), dichotellides A (V), cerevisterol (VI), 1,2-diphenyldiselane (VII) and 5H-pyrido[4,3-b] indole (VIII). CONCLUSION: Compounds VI, VII and VIII are isolated from Dichotella gemmacea for the first time.

Multi-metal ions co-regulated vanadium oxide cathode toward long-life aqueous zinc-ion batteries.

Interlayer intercalation engineering shows great feasibility to improve the structure stability of the layered oxides. Although high Zn-storage capability has been attained based on the pillar effect of multifarious intercalants, an in-depth understanding the synergistic effect of intercalated multiple metal ions is still in deficiency. Herein, alkali metal ion K+, alkaline earth metal ion Mg2+ and trivalent metal ion Al3+ are introduced into the VO interlayer of V2O5. Due to the different electronegativity and hydrated ion radius of K+, Mg2+ and Al3+, adjusting the relative proportions of these metal ions can achieve an appropriate interlayer spacing, stable layer structure and regular morphology, which facilitates the transport kinetics of Zn2+. Under the synergistic effect of pre-intercalated multi-metal ion, the optimal tri-metal ion intercalated hydrated V2O5 cathode exhibits a high specific capacity of 382.4 mAh g-1 at 0.5 A g-1, and long-term cycling stability with capacity retention of 86 % after 2000 cycles at the high current density of 10 A g-1. Ex-situ and kinetic characterizations reveal the fast charge transfer and reversible Zn2+ intercalation mechanism. The multi-ion engineering strategy provides an effective way to design desirable layered cathode materials for aqueous zinc-ion batteries.

Solvent-Free Ultrafast Construction of Se-Deficient Heterojunctions of Bimetallic Selenides toward Flexible Sodium-Ion Full Batteries.

Flexible quasi-solid-state sodium ion batteries featuring their low-cost, high safety and excellent mechanical strength have attracted widespread interest in the field of wearable electronic devices. However, the development of such batteries faces great challenges including the construction of interfacial compatible flexible electrode materials and addressing the high safety demands of electrolyte. Here selenium-vacancies regulated bimetallic selenide heterojunctions anchored on waste cotton cloth-derived flexible carbon cloth (FCC) with robust interfacial C-Se-Co/Fe chemical bonds as a flexible anode material (CCFSF) is proposed by ultrafast microwave pyrolysis method. Rich selenium vacancies and CoSe2 /FeSe2-x heterostructures are synchronously formed that can significantly improve ionic and electronic diffusion kinetics. Additionally, a uniform carbon layer coating on the surface of Se-deficient heterostructures endows it with outstanding structural stability. The flexible cathode (PB@FCC) is also fabricated by directly growing Prussian blue nanoparticles on the FCC. Furthermore, an advanced flexible quasi-solid-state Na-ion pouch cell is assembled by coupling CCFSF anode, PB@FCC cathode with P(VDF-HFP)-based gel polymer electrolyte. The full cell not only demonstrates excellent energy storage performance but also robust mechanical flexibility and safety. The present work offers an effective avenue to achieve high safety flexible energy storage device, promoting the development of flexible wearable electronic devices.

Dynamic Li+ Capture through Ligand-Chain Interaction for the Regeneration of Depleted LiFePO4 Cathode.

After application in electric vehicles, spent LiFePO4 (LFP) batteries are typically decommissioned. Traditional recycling methods face economic and environmental constraints. Therefore, direct regeneration has emerged as a promising alternative. However, irreversible phase changes can significantly hinder the efficiency of the regeneration process owing to structural degradation. Moreover, improper storage and treatment practices can lead to metamorphism, further complicating the regeneration process. In this study, a sustainable recovery method is proposed for the electrochemical repair of LFP batteries. A ligand-chain Zn-complex (ZnDEA) is utilized as a structural regulator, with its ─NH─ group alternatingly facilitating the binding of preferential transition metal ions (Fe3+ during charging and Zn2+ during discharging). This dynamic coordination ability helps to modulate volume changes within the recovered LFP framework. Consequently, the recovered LFP framework can store more Li-ions, enhance phase transition reversibility between LFP and FePO4 (FP), modify the initial Coulombic efficiency, and reduce polarization voltage differences. The recovered LFP cells exhibit excellent capacity retention of 96.30% after 1500 cycles at 2 C. The ligand chain repair mechanism promotes structural evolution to facilitate ion migration, providing valuable insights into the targeted ion compensation for environmentally friendly recycling in practical applications.

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 Na3V2(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.

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.

Pearl-Structure-Enhanced NASICON Cathode toward Ultrastable Sodium-Ion Batteries.

Based on the favorable ionic conductivity and structural stability, sodium superionic conductor (NASICON) materials especially utilizing multivalent redox reaction of vanadium are one of the most promising cathodes in sodium-ion batteries (SIBs). To further boost their application in large-scale energy storage production, a rational strategy is to tailor vanadium with earth-abundant and cheap elements (such as Fe, Mn), reducing the cost and toxicity of vanadium-based NASICON materials. Here, the Na3.05 V1.03 Fe0.97 (PO4 )3 (NVFP) is synthesized with highly conductive Ketjen Black (KB) by ball-milling assisted sol-gel method. The pearl-like KB branch chains encircle the NVFP (p-NVFP), the segregated particles possess promoted overall conductivity, balanced charge, and modulated crystal structure during electrochemical progress. The p-NVFP obtains significantly enhanced ion diffusion ability and low volume change (2.99%). Meanwhile, it delivers a durable cycling performance (87.7% capacity retention over 5000 cycles at 5 C) in half cells. Surprisingly, the full cells of p-NVFP reveal a remarkable capability of 84.9 mAh g-1 at 20 C with good cycling performance (capacity decay rate is 0.016% per cycle at 2 C). The structure modulation of the p-NVFP provides a rational design on the superiority of others to be put into practice.