A Novel Hexaazatriphenylene Carboxylate with Compatible Binder as Anode for High-Performance Organic Potassium-Ion Batteries

Organic electrode materials have attracted tremendous attention for potassium-ion batteries (PIBs). Whereas, high-performance anodes are scarcely reported. Herein, a novel hexaazatriphenylene potassium carboxylate (HAT-COOK) is proposed as anode materials for PIBs. The rich CN/CO bonds guarantee the high theoretical capacity. It is also demonstrated HAT-COOK is more compatible with the water-soluble binders than the hydrophobic fluoride binders, forming homogenous electrode film, maintaining structural integrity, and achieving stable cycling and excellent rate performance. With the compatible binder, each HAT-COOK molecule can involve 6-electron transfer, yielding a high reversible discharge capacity of 288 mAh g⁻¹ at 50 mA g⁻¹, excellent rate performance (105 mAh g⁻¹ at 5000 mA g⁻¹), and good cycling stability (143 mAh g⁻¹ after 500 cycles at 500 mA g⁻¹). These results highlight the importance of the delicate molecular design of organic molecules as well as the optimization of binders to achieve high-performance PIBs.     

Van der Waals Forces between S and P Ions at the CoP-C@MoS2/C Heterointerface with Enhanced Lithium/Sodium Storage

Metal–organic framework-derived metal phosphides with high capacity, facile synthesis, and morphology-controlled are considered as potential anodes for lithium/sodium-ion batteries. However, the severe volume expansion during cycling can cause the electrode material to collapse and reduce the cycle life. Here, novel CoP-C@MoS₂/C nanocube composites are synthesized by vapor-phase phosphating and hydrothermal process. As the anode of LIBs, CoP-C@MoS₂/C exhibits outstanding long-cycle performance of 369 mAh g⁻¹ at 10 A g⁻¹ after 2000 cycles. In SIBs, the composite also displays excellent rate capability of 234 mAh g⁻¹ at 5 A g⁻¹ and an ultra-high the capacity retention rate of 90.16% at 1 A g⁻¹ after 1000 cycles. Through density functional theory, it is found that the S ions and P ions at the interface formed by CoP and MoS₂ can serve as Na⁺/Li⁺ diffusion channels with an action of van der Waals force, have attractive characteristics such as high ion adsorption energy, low expansion rate and fast diffusion kinetics compared with MoS₂. This study provides enlightenment for the reasonable design and development of lithium/sodium storage anode materials composited with MOF-derived metal phosphides and metal sulfides.     

Si/SiO2@Graphene Superstructures for High-Performance Lithium-Ion Batteries

The superstructure composed of various functional building units is promising nanostructure for lithium-ion batteries (LIBs) anodes with extreme volume change and structure instability, such as silicon-based materials. Here, a top-down route to fabricate Si/SiO₂@graphene superstructure is demonstrated through reducing silicalite-1 with magnesium reduction and depositing carbon layers. The successful formation of superstructure lies on the strong 3D network formed by the bridged-SiO₂ matrix coated around silicon nanoparticles. Furthermore, the mesoporous Si/SiO₂ with amorphous bridged SiO₂ facilitates the deposition of graphene layers, resulting in excellent structural stability and high ion/electron transport rate. The optimized Si/SiO₂@graphene superstructure anode delivers an outstanding cycling life for ≈1180 mAh g⁻¹ at 2 A g⁻¹ over 500 cycles, excellent rate capability for ≈908 mAh g⁻¹ at 12 A g⁻¹, great areal capacity for ≈7 mAh cm⁻² at 0.5 mA cm⁻², and extraordinary mechanical stability. A full cell test using LiFePO₄ as the cathode manifests a high capacity of 134 mAh g⁻¹ after 290 loops. More notably, a series of technologies disclose that the Si/SiO₂@graphene superstructure electrode can effectively maintain the film between electrode and electrolyte in LIBs. This design of Si/SiO₂@graphene superstructure elucidates a promising potential for commercial application in high-performance LIBs.     

A Semi-Liquid Electrode toward Stable Zn Powder Anode

Zn powder anode possesses great versatility compared to the Zn foil counterpart, but the rough surface with a high surface area aggravates the corrosion and dendrite growth. Herein, a dendrite-free and anti-corrosive semi-liquid Zn anode (SLA) is successfully fabricated based on Zn powder and a thickening agent. Benefiting from the rheological property, the unique anode effectively releases the stress induced by Zn plating, especially under high-current densities. Meanwhile, the dual-conductive medium, i.e., ionic and electronic, homogenizes the ion flux and allows the stripping/plating to occur within the entire anode. In a symmetric cell, the SLA anode exhibits stable electrochemical behavior with a prolonged lifespan at the current density of 5 mA cm⁻²/10 mA cm⁻² under the capacity of 5 mAh cm⁻²/10 mAh cm⁻². Improved durability of more than 5000 cycles is endowed when assembling an SLA anode with a vanadium-based cathode. This study provides an electrode rheology-based approach to overcome the stability challenge of powder anode for scale-up manufacturing.     

Engineering Se/N Co-Doped Hard CNTs with Localized Electron Configuration for Superior Potassium Storage

The earth-abundant hard carbons have drawn great concentration as potassium-ion batteries (KIBs) anode materials because of their richer K-storage sites and wider interlayer distance versus graphite, but suffer from a low electrochemical reversibility. Herein, the novel Se/N co-doped hard-carbon nanotubes (h-CNTs) with localized electron configuration are demonstrated by creating unique N Se C covalent bonds stemmed from the precise doping of Se atoms into carbon edges and the subsequent bonding with pyrrole-N. The strong electron-donating ability of Se atoms on d-orbital provides abundant free electrons to effectively relieve charge polarization of pyrrole-N-C bonds, which contributes to balance the K-ion adsorption/desorption, therefore greatly boosting reversible K-ion storage capacity. After filtering into self-standing anodes with weights of 1.5–12.4 mg cm⁻², all of them deliver a high reversible gravimetric capacity of 341 ± 4 mAh g⁻¹ at 0.2 A g⁻¹ and a linear increasing areal capacity to 4.06 mAh cm⁻². The self-standing anode can still maintain 209 mAh g⁻¹ at 8.0 A g⁻¹ (93.3% retention) for a long period of 2000 cycles with a constant Se/N content.     

Mg-Doped Na4Fe3(PO4)2(P2O7)/C Composite with Enhanced Intercalation Pseudocapacitance for Ultra-Stable and High-Rate Sodium-Ion Storage

Na₄Fe₃(PO₄)₂(P₂O₇) (NFPP) is considered as a promising cathode material for sodium-ion batteries (SIBs) due to its low cost, non-toxicity, and high structural stability, but its electrochemical performance is limited by the poor electronic conductivity. In this study, Mg-doped NFPP/C composites are presented as cathode materials for SIBs. Benefiting from the enhanced electrochemical kinetics and intercalation pseudocapacitance resulted from the Mg doping, the optimal Mg-doped NFPP/C composite (NFPP-Mg5%) delivers high rate performance (capacity of ≈40 mAh g⁻¹ at 20 A g⁻¹) and ultra-long cycling life (14 000 cycles at 5 A g⁻¹ with capacity retention of 80.8%). Moreover, the in situ X-ray diffraction and other characterizations reveal that the sodium storage process of NFPP-Mg5% is dominated by the intercalation pseudocapacitive mechanism. In addition, the full SIB based on NFPP-Mg5% cathode and hard carbon anode exhibits the discharge capacity of ≈50 mAh g⁻¹ after 200 cycles at 500 mA g⁻¹. This study demonstrates the feasibility of improving the electrochemical performance of NFPP by doping strategy and presents a low-cost, ultra-stable, and high-rate cathode material for SIBs.     

Controlled Nitrogen Doping in Crumpled Graphene for Improved Alkali Metal-Ion Storage under Low-Temperature Conditions

The significant performance decay in conventional graphite anodes under low-temperature conditions is attributed to the slow diffusion of alkali metal ions, requiring new strategies to enhance the charge storage kinetics at low temperatures. Here, nitrogen (N)-doped defective crumpled graphene (NCG) is employed as a promising anode to enable stable low-temperature operation of alkali metal-ion storage by exploiting the surface-controlled charge storage mechanisms. At a low temperature of −40 °C, the NCG anodes maintain high capacities of ≈172 mAh g⁻¹ for lithium (Li)-ion, ≈107 mAh g⁻¹ for sodium (Na)-ion, and ≈118 mAh g⁻¹ for potassium (K)-ion at 0.01 A g⁻¹ with outstanding rate-capability and cycling stability. A combination of density functional theory (DFT) and electrochemical analysis further reveals the role of the N-functional groups and defect sites in improving the utilization of the surface-controlled charge storage mechanisms. In addition, the full cell with the NCG anode and a LiFePO₄ cathode shows a high capacity of ≈73 mAh g⁻¹ at 0.5 °C even at −40 °C. The results highlight the importance of utilizing the surface-controlled charge storage mechanisms with controlled defect structures and functional groups on the carbon surface to improve the charge storage performance of alkali metal-ion under low-temperature conditions.     

N-Rich Solid Electrolyte Interface Constructed In Situ Via a Binder Strategy for Highly Stable Silicon Anode

Silicon (Si) is regarded as a promising anode material for high-energy-density lithium-ion batteries due to its high specific capacity (4200 mAh g⁻¹) and low potential (0.3 V vs Li⁺/Li). However, the large volume change (over 300%) of Si during the lithiation/delithiation process leads to severe pulverization, electrode structure destruction, and finally capacity fading, which slows down its step to practical application. Herein, a poly(vinylamine) (PVAm) binder containing amino ( NH₂) and amide ( NH CHO) is proposed to improve the stability of Si anodes from particle to electrode structure. The N-containing functional groups show strong interaction with the Si particles and form a uniform and thin layer on the surface, which would decompose and form an N-rich inorganic solid electrolyte interphase (SEI) layer during discharging. The high mechanical stability N-rich SEI helps relieve the pulverization of Si particles through stress dissipation, maintains electrode structural stability, and reduces the loss of active materials. Thus, the Si anode with PVAm binder exhibits high capacity of ≈2000 mAh g⁻¹ after 200 cycles, which is much higher than that of using Poly(vinylidene fluoride) (PVDF) binder (66 mAh g⁻¹) and Poly(vinyl alcohol) PVA binder (820 mAh g⁻¹). This facile and practical strategy provides a new perspective for the application of Si anodes in advanced batteries.     

Unravelling the Solvation Structure and Interfacial Mechanism of Fluorinated Localized High Concentration Electrolytes in K-ion Batteries

Electrolyte is critical for the electrochemical properties of potassium-ion batteries. The high-concentration electrolyte has achieved significant effects in inhibiting the growth of dendrites and improving the cycle life of potassium ion batteries. However, the application remains challenging owing to the issues of high viscosity, low conductivity and poor electrode wettability. Herein, a fluorinated localized high concentration electrolyte (LHCE) based on potassium bis(fluorosulfonyl) imide/dimethoxyethane is designed for use in K-ion batteries. The electrolyte structure, interfacial mechanism and diffusion kinetics are analyzed systematically through physical/electrochemical characterization and molecular dynamics simulations. The LHCE is proven to have excellent oxidation stability, low flammability, and excellent electrode wettability. Furthermore, the LHCE is investigated in a half-cell assembled by using polyimide-derived nitrogen doped carbon material as an anode, which exhibits a reversible capacity of 169 mAh g⁻¹ and high-capacity retention upon 200 cycles at a current rate of 100 mA g⁻¹. Fundamental mechanism on enhanced cycling stability of the carbon anodes using optimized LHCE is also investigated. This work demonstrates an example of developing new electrolytes for high performance potassium ion batteries, and also provides theoretical guidance and significant reference for electrode interphase design and engineering.     

A Self-Healing Volume Variation Three-Dimensional Continuous Bulk Porous Bismuth for Ultrafast Sodium Storage

Bismuth (Bi) has attracted considerable attention as promising anode material for sodium-ion batteries (NIBs) owing to its suitable reaction potential and high volumetric capacity density (3750 mA h cm⁻³). However, the large volumetric expansion during cycling causes severe structural degradation and fast capacity decay. Herein, by rational design, a self-healing nanostructure 3D continuous bulk porous bismuth (3DPBi) is prepared via facile liquid phase reduction reaction. The 3D interconnected Bi nanoligaments provide unblocked electronic circuits and short ion diffusion path. Meanwhile, the bicontinuous nanoporous network can realize self-healing the huge volume variation as confirmed by in situ and ex situ transmission electron microscopy observations. When used as the anode for NIBs, the 3DPBi delivers unprecedented rate capability (high capacity retention of 95.6% at an ultrahigh current density of 60 A g⁻¹ with respect to 1 A g⁻¹) and long-cycle life (high capacity of 378 mA h g⁻¹ remained after 3000 cycles at 10 A g⁻¹). In addition, the full cell of Na₃V₂(PO₄)₃|3DPBi delivers stable cycling performance and high gravimetric energy density (116 Wh kg⁻¹), demonstrating its potential in practical application.     

Designing and Understanding the Superior Potassium Storage Performance of Nitrogen/Phosphorus Co-Doped Hollow Porous Bowl-Like Carbon Anodes

Potassium-ion batteries (PIBs) are promising alternatives to lithium-ion batteries because of the advantage of abundant, low-cost potassium resources. However, PIBs are facing a pivotal challenge to develop suitable electrode materials for efficient insertion/extraction of large-radius potassium ions (K⁺). Here, a viable anode material composed of uniform, hollow porous bowl-like hard carbon dual doped with nitrogen (N) and phosphorus (P) (denoted as N/P-HPCB) is developed for high-performance PIBs. With prominent merits in structure, the as-fabricated N/P-HPCB electrode manifests extraordinary potassium storage performance in terms of high reversible capacity (458.3 mAh g⁻¹ after 100 cycles at 0.1 A g⁻¹), superior rate performance (213.6 mAh g⁻¹ at 4 A g⁻¹), and long-term cyclability (205.2 mAh g⁻¹ after 1000 cycles at 2 A g⁻¹). Density-functional theory calculations reveal the merits of N/P dual doping in favor of facilitating the adsorption/diffusion of K⁺ and enhancing the electronic conductivity, guaranteeing improved capacity, and rate capability. Moreover, in situ transmission electron microscopy in conjunction with ex situ microscopy and Raman spectroscopy confirms the exceptional cycling stability originating from the excellent phase reversibility and robust structure integrity of N/P-HPCB electrode during cycling. Overall, the findings shed light on the development of high-performance, durable carbon anodes for advanced PIBs.     

Low Volume-Expansion,Insertion-Type Layered Silicate Hierarchical Structure For Superior Storage Of Li,Na, K

A hierarchical structure is successfully synthesized by coating polypyrrole (PPy) on the surface of carbon/saponite superlattice (denoted as PPy@C/SAP), and applied as low volume-expansion insertion-type anode for Li, Na, K storage.The synergistic effect of metal Ni, Fe doping, carbon/silicate superlattice, abundant oxygen vacancies and PPy coating leads to a good electronic conductivity and large current discharging capability. As a Si-based material, PPy@C/SAP has excellent storage capability for Li (659 mAh g⁻¹ after 1000 cycles at 2 A g⁻¹ and 550 mAh g⁻¹ after 1000 cycles at 5 A g⁻¹), Na (maximum specific capacity of 533 and 327 mAh g⁻¹ after 50 cycles) as well as K (236 mAh g⁻¹ after 100 cycles). XPS, XANES, XRD, FTIR, HRTEM, SEM are used to detect the hybrid mechanism (bulk insertion and surface conversion) with a volume expansion as low as 9%. Insertion reaction driven by valence state change of Ni, Fe, Si (Ni⁰⇔Ni²⁺, Fe0⇔Fe³⁺, Si²⁺⇔Si⁴⁺) in laminates and conversion reactions between LiOH/Li₂CO₃ and LiH/Li₂C₂ catalyzed by Ni° contribute to the high performance. In the whole electrochemical process, layered structure is retained while the conversion reactions of LiOH (prodeced by laminates dehydroxylation) and Li₂CO₃ (electrolyte decomposition) cause the dynamic evolution of solid ectrolyte interphase. This study develops a promising Si-based anode material for lithium ion batteries, sodium ion batteries and potassium ion batteries, which is significant for designing long cycle life rechargeable batteries.     

An In Situ Electrochemical Amorphization Electrode Enables High-Power High-Cryogenic Capacity Aqueous Zinc-Ion Batteries

Quick-charge technology is of great significance for the development of aqueous zinc-ion batteries. In this study, an unreported in situ electrochemical amorphization mechanism is highlighted to unlock the ultrafast-kinetics electrode. Multiple characterizations, density functional theory calculation, and molecular dynamic simulation are applied to uncover the storage mechanism of electrodes, as well as the evolution of structure, and reaction kinetics after reconstruction. As revealed, the long-range ordered ZnV₂O₄ crystalline can be reconstructed to a short-range ordered Zn_0.44V₂O₄ electrode, which exhibits significantly improved active sites, shortened diffusion path, and enhanced zinc ions capture ability. Notably, by pairing with the modified Zn anode, it can display ultrahigh rate capability (212 mAh g⁻¹ at 50 A g⁻¹) with a maximum power density of 23.2 kW kg⁻¹, as well as good cycle performance (217.2 mAh g⁻¹ after 3000 cycles at 20 A g⁻¹). Unexpectedly, such reconstructed amorphous electrodes can also retain superior storage capability even at cryogenic conditions. A high specific capacity of 251 mAh g⁻¹ can be delivered at −25°C and 1 A g⁻¹, as well as an 84.3% capacity retention after 500 cycles. This brand-new in-situ electrochemical amorphization mechanism is expected to provide new insight into understanding the high-performance aqueous zinc-ion batteries.     

Fe2VO4 Nanoparticles Anchored on Ordered Mesoporous Carbon with Pseudocapacitive Behaviors for Efficient Sodium Storage

Iron vanadates are attractive anode materials for sodium-ion batteries (SIBs) because of their abundant resource reserves and high capacities. However, their practical application is restricted by the aggregation of materials, sluggish reaction kinetics, and inferior reversibility. Herein, Fe₂VO₄ nanoparticles are anchored on the ordered mesoporous carbon (CMK-3) nanorods to assemble 3D Fe₂VO₄@CMK-3 composites, by solvothermal treatment and subsequent calcination. The resulting composites provide abundant active sites, high electrical conductivity, and excellent structural integrity. The pseudocapacitive-controlled behavior is the dominating sodium storage mechanism, which facilitates a fast charge/discharge process. The Fe₂VO₄@CMK-3 composites exhibit stable sodium-ion storage (219 mAh g⁻¹ under 100 mA g⁻¹ after 300 cycles), good rate performance (144 mAh g⁻¹ at 3.2 A g⁻¹), and excellent cycling performance (132 mAh g⁻¹ at 1 A g⁻¹ with capacity retention of 96.4% after 800 cycles). When coupled with a NaNi_1/3Fe_1/3Mn_1/3O₂ cathode, the sodium-ion full cell displays excellent cycling stability (94 mAh g⁻¹ after 500 cycles at 500 mA g⁻¹). These findings point to the potential of Fe₂VO₄@CMK-3 for application as anodes in SIBs.     

Novel Designed MnS-MoS2 Heterostructure for Fast and Stable Li/Na Storage:Insights into the Advanced Mechanism Attributed to Phase Engineering

Combining 2D MoS₂ with other transition metal sulfide is a promising strategy to elevate its electrochemical performances. Herein, heterostructures constructed using MnS nanoparticles embedded in MoS₂ nanosheets (denoted as MnS-MoS₂) are designed and synthesized as anode materials for lithium/sodium-ion batteries via a facile one-step hydrothermal method. Phase transition and built-in electric field brought by the heterostructure enhance the Li/Na ion intercalation kinetics, elevate the charge transport, and accommodate the volume expansion. The sequential phase transitions from 2H to 3R of MoS₂ and α to γ of MnS are revealed for the first time. As a result, the MnS-MoS₂ electrode delivers outstanding specific capacity (1246.2 mAh g⁻¹ at 1 A g⁻¹), excellent rate, and stable long-term cycling stability (397.2 mAh g⁻¹ maintained after 3000 cycles at 20 A g⁻¹) in Li-ion half-cells. Superior cycling and rate performance are also presented in sodium half-cells and Li/Na full cells, demonstrating a promising practical application of the MnS-MoS₂ electrode. This work is anticipated to afford an in-depth comprehension of the heterostructure contribution in energy storage and illuminate a new perspective to construct binary transition metal sulfide anodes.     

A Self-Growth Strategy for Simultaneous Modulation of Interlayer Distance and Lyophilicity of Graphene Layers toward Ultrahigh Potassium Storage Performance

Herein, a simple but effective self-growth strategy to simultaneously modulate the interlayer distance and lyophilicity of graphene layers, which results in ultrahigh potassium-storage performances for carbon materials, is reported. This strategy involves the uniform adsorption of individual metal ions on the oxygen-containing groups on graphene oxide via electrostatic/coordination interactions and in situ self-conversion reaction between the metal ions and the oxygen-containing groups to form lyophilic ultrasmall metal oxide nanoparticles modified/intercalated graphene skeleton (OM-G) with precisely regulated interlayer distance. The synergistic effect of expanded interlayer distance and enhanced lyophilicity is revealed for the first time to significantly reduce the ion diffusion barrier and enhance ion transport kinetics by experimental and theoretical analysis. As a result, such unique OM-G monolith as free-standing anode for potassium-ion battery (PIB) delivered an ultrahigh reversible capability of 496.4 mAh g⁻¹ at 0.1 A g⁻¹, excellent rate capability (306.6 mAh g⁻¹ at 10 A g⁻¹), and remarkable long-term cycling stability (96.3% capacity retention over 2000 cycles at 1 A g⁻¹), which are not only much better than those of previous graphene/carbon materials but also among the best performances for all PIB anodes ever reported. This study provides new fundamental insights for boosting the electrochemical properties of electrode materials.     

On the Practical Applicability of Rambutan-like SiOC Anode with Enhanced Reaction Kinetics for Lithium-Ion Storage

Silicon oxycarbide (SiOC) possesses great potential in lithium-ion batteries owing to its tunable chemical component, high reversible capacity, and small volume expansion. However, its commercial application is restricted due to its poor electrical conductivity. Herein, rambutan-like vertical graphene coated hollow porous SiOC (Hp-SiOC@VG) spherical particles with an average diameter of 302 nm are fabricated via a hydrothermal treatment combined CH₄ pyrolysis strategy for the first time. As-prepared Hp-SiOC@VG exhibits a large reversible capacity of 729 mAh g⁻¹ at 0.1 A g⁻¹, remarkable cycling stability of 98% capacity retention rate after 600 cycles at 1.0 A g⁻¹ and high rate capability of 289 mAh g⁻¹ at 5.0 A g⁻¹ owing to the unique structure of the particles and the electrical conductivity of the vertical graphene. Density functional theory calculations reveal that the higher contents of SiO₃C and SiO₂C₂ structural units in the SiOC are beneficial to enhance the Li⁺ storage capacity. Additionally, the full-cell assembled with Hp-SiOC@VG and LiFePO₄ delivers up to 74% capacity retention rate after 100 cycles at 0.2 A g⁻¹. This work reports a new way for the facile preparation of template-free hollow porous materials and expands the application prospects of SiOC-based anode for lithium-ion batteries.     

Neuromorphic Carbon for Fast and Durable Potassium Storage

Graphitic carbon materials (GCs) are attractive as anodes for the industrialization of potassium ion batteries (PIBs). However, the poor cycle and rate performance of GC-based anodes hinder the development of PIBs. In this study, inspired by the nervous system, neuromorphic GCs (NGCs) are designed to use as potassium anodes with high cycling stability and excellent rate performance. The inherent neuromorphic nature of NGCs enables fast signal transmission via multiwalled carbon nanotubes (MWCNTs), which serve as efficient pathways for electronic transmission. Meanwhile, the low-stress properties of hollow carbon spheres effectively support the cycling stability of PIBs. As a result, NGC-based potassium anodes achieved an unprecedented cycle life over 18 months (2400 cycles) with a reversible capacity of up to 225 mAh g⁻¹ at a current density of 100 mA g⁻¹. Moreover, the novel anode exhibits exceptional rate performance (73.6 mAh g⁻¹ at 1 A g⁻¹). The research presented here offers a practical and straightforward method for potassium's long-term and high-rate storage and beyond.     

Effective Coupling of Amorphous Selenium Phosphide with High-Conductivity Graphene as Resilient High-Capacity Anode for Sodium-Ion Batteries

It is of great importance to develop high-capacity electrodes for sodium-ion batteries (SIBs) using low-cost and abundant materials, so as to deliver a sustainable technology as alternative to the established lithium-ion batteries (LIBs). Here, a facile ball milling process to fabricate high-capacity SIB anode is devised, with large amount of amorphous SeP being loaded in a well-connected framework of high-conductivity crystalline graphene (HCG). The HCG substrate enables fast transportation of Na ions and electrons, while accommodating huge volumetric changes of the active anode matter of SeP. The strong glass forming ability of NaxSeP helps prevent crystallization of all stable compounds but ultrafine nanocrystals of Na2Se and Na3P. Thus, the optimized anode delivers excellent rate performance with high specific capacities being achieved (855 mAh g⁻¹ at 0.2 A g⁻¹ and 345 mAh g⁻¹ at 5 A g⁻¹). More importantly, remarkable cycling stability is realized to maintain a steady capacity of 732 mAh g⁻¹ over 500 cycles, when the SeP in the SeP@HCG still remains 86% of its theoretical capacity. A high areal capacity of 2.77 mAh is achieved at a very high loading of 4.1 mg cm⁻² anode composite.     

In Situ Synthesis of Graphene-Coated Silicon Monoxide Anodes from Coal-Derived Humic Acid for High-Performance Lithium-Ion Batteries

Silicon monoxide (SiO) is attaining extensive interest amongst silicon-based materials due to its high capacity and long cycle life; however, its low intrinsic electrical conductivity and poor coulombic efficiency strictly limit its commercial applications. Here low-cost coal-derived humic acid is used as a feedstock to synthesize in situ graphene-coated disproportionated SiO (D-SiO@G) anode with a facile method. HR-TEM and XRD confirm the well-coated graphene layers on a SiO surface. Scanning transmission X-ray microscopy and X-ray absorption near-edge structure spectra analysis indicate that the graphene coating effectively hinders the side-reactions between the electrolyte and SiO particles. As a result, the D-SiO@G anode presents an initial discharge capacity of 1937.6 mAh g⁻¹ at 0.1 A g⁻¹ and an initial coulombic efficiency of 78.2%. High reversible capacity (1023 mAh g⁻¹ at 2.0 A g⁻¹), excellent cycling performance (72.4% capacity retention after 500 cycles at 2.0 A g⁻¹), and rate capability (774 mAh g⁻¹ at 5 A g⁻¹) results are substantial. Full coin cells assembled with LiFePO₄ electrodes and D-SiO@G electrodes display impressive rate performance. These results indicate promising potential for practical use in high-performance lithium-ion batteries.