Ion Intercalation Research Articles

Synthesis by design and application to desalination of VO2/CTAB-Ti3C2 capacitive deionization electrode

As an emerging technology in capacitive deionization (CDI), flow-electrode capacitive deionization (FCDI) has attracted much attention due to its unlimited electrosorption capacity and continuous operation. Like CDI, carbon is generally chosen as the electrode material for FCDI at this stage, but conventional carbon materials have limited desalination capacity due to the double electric layer. The two-dimensional layered material MXene has been gradually applied to CDI due to its unique structure and physicochemical properties. However, the van der Waals forces exist between the MXene layers, and the layered structure of MXene is susceptible to stacking, while exhibiting an obvious swelling behavior in aqueous solution, thus affecting its desalination performance. Herein, we report a designed VO2/CTAB-Ti3C2 heterostructure synthesised by a simple hydrothermal method. The addition of VO2 can alleviate the lamellar structure buildup of Ti3C2 and improve the desalination performance of Ti3C2. On the other hand, Ti3C2 can be used as a conductive substrate for VO2, which improves the charge transfer rate of VO2, prevents VO2 agglomeration, and provides more contact surfaces for ion intercalation. Compared with the pure VO2 and Ti3C2 electrodes, the composite electrode has a good desalination performance, and its desalination reaches 1041.5 mg g−1 at 1.2 V. Therefore, this VO2/CTAB-Ti3C2 hybrid material is expected to be used as an electrode material for flow capacitive deionization.

Modern innovations in the provision and efficient application of 2D inorganic nanoscale materials

Abstract Two-dimensional nanoscale materials (2D NMs) have exceptional physical characteristics, distinctive structures, and customizable surface chemistry. They consist of infinite transverse dimensions of near-atomic thickness or atoms. They promise advancements in catalysis, renewable energy, and sensing. An extensive summary of the most recent research results on the creation and use of 2D NMs is provided in this work. It is possible to modify the characteristics of these multi-layered materials by means of chemical and physical manipulations. Due to their layer-dependent electrical properties, certain 2D layered inorganic nanomaterials such as MoS2, WS2, and SnS2 have recently been created and used in a variety of applications, including new sensors. In addition, the article delves into the difficulties confronted by sectors reliant on nanotechnology as well as the potential future uses of nanostructures coupled with electrochemical systems. The article begins by outlining the typical “top-down” and “bottom-up” approaches for synthesizing 2D NMs. These approaches include hydrothermal procedures, ion intercalation, mechanical exfoliation, liquid-phase exfoliation assisted by ultrasonic waves, and chemical vapor deposition. 2D NMs are the focus of this work because of their potential applications in gas sensing, photocatalysis, electrocatalysis, photo detection, and electromagnetic wave absorption. In addition, the study predicts patterns of future development and possible issues with 2D NMs based on existing studies. Increased demand for cost-effective, environmentally friendly, and highly connected products is propelling the ongoing research and development of these high-performance materials. This research is significant since it summarizes, in one place, the most recent advances in 2D NM preparation methods and applications.

Reversible Deposition/Dissolution of Double Hydroxides to Modulate Electrolyte pH Enabling High-Performance Aqueous Zinc-Ion Batteries.

Vanadium oxide has been extensively studied as a host of zinc ion intercalation but still suffers from low conductivity, dissolution, and byproduct accumulation during cycling. Here, we hydrothermally synthesize the VO2@MXene Ti3C2 (MV) composite and find that in the MV//3 M Zn(CF3SO3)2//Zn system, the double hydroxide Zn12(CF3SO3)9(OH)15·nH2O (ZCOH) uniformly covers VO2 during the charging process and dissolves reversibly during the discharge process. In situ X-ray diffraction of the MV combined with in situ pH measurements reveals that ZCOH acts as a pH buffer during cycling, which is beneficial to the cycling stability of batteries. And the theoretical calculation indicates that the decomposition energy required by ZCOH on the MV surface is lower than that on pure VO2, which is more conducive to ZCOH dissolution. The coin battery exhibits high-rate performance of 65.1% capacity retention at a current density of 15 A g-1 (compared to 0.6 A g-1) and a long cycling life of 20,000 cycles with a capacity retention of 80.7%. For a 22.4 mA h soft-packaged battery, its capacity remains at 72.1% after 2000 cycles. This work demonstrates the active role of ZCOH in the electrochemical process of VO2 and provides a new perspective for exploiting this mechanism to develop high-performance aqueous zinc-ion battery vanadium oxide cathode materials.

High-Performance Porous pSi/Ag@C Anode for Lithium-Ion Batteries

Silicon represents one of the most attractive anode materials in lithium-ion batteries (LIBs) due to its highest theoretical specific capacity. Thus, there is a most urgent need to prepare Si-based nano materials in a very efficient way and develop some reasonable approaches for their modification in order to resolve the short-falls of Si anodes, which include both low conductivity and huge volume changes during intercalation of lithium ions. In this work, the kerf loss silicon (KL Si) from the photovoltaic industry has been used as an inexpensive Si source for the preparation of a porous silicon/silver/carbon composite (pSi/Ag@C) as an anode material. Porous silicon was embedded with Ag particles via the Ag-catalyzed chemical etching process, providing additional space to accommodate the large volume expansion of silicon. After carbon coating from polymerization of tannic acid on the surface of pSi/Ag, a high-speed conductive network over the surface of silicon was built and contributed to enhancing the electrochemical performance of the anode. The pSi/Ag@C electrode discharge capacity maintained at a stable value of 665.3 mAh g−1 after 100 cycles under 0.5 A g−1 and exhibited good rate performance. Therefore, this study recommends that the method is very promising for producing a silicon anode material for LIBs from KL Si.

Intercalation in 2D materials and in situ studies.

Intercalation of atoms, ions and molecules is a powerful tool for altering or tuning the properties - interlayer interactions, in-plane bonding configurations, Fermi-level energies, electronic band structures and spin-orbit coupling - of 2D materials. Intercalation can induce property changes in materials related to photonics, electronics, optoelectronics, thermoelectricity, magnetism, catalysis and energy storage, unlocking or improving the potential of 2D materials in present and future applications. In situ imaging and spectroscopy technologies are used to visualize and trace intercalation processes. These techniques provide the opportunity for deciphering important and often elusive intercalation dynamics, chemomechanics and mechanisms, such as the intercalation pathways, reversibility, uniformity and speed. In this Review, we discuss intercalation in 2D materials, beginning with a brief introduction of the intercalation strategies, then we look into the atomic and intrinsic effects of intercalation, followed by an overview of their in situ studies, and finally provide our outlook.

Transparent Conducting TiO2 Thin Film Induced by Electric‐Field Controlled Hydrogen Ion Intercalation

AbstractRealizing transformation from transparent insulating to transparent conducting, is a pursuing goal in designing and fabricating novel optoelectronic materials and devices. Here, a pronounced insulating to metal transition in anatase TiO2 thin films is achieved through ionic liquid gating, and interestingly the material maintains an invariable high optical transparency. It is revealed that the emergent metallic state can be attributed to the electron doping associated with the hydrogen ion intercalation. Importantly, the hydrogenation leads to the almost rigid shift of the Fermi energy and therefore maintains nicely the transparency at the visible light region. This result is in strong contrast with the case of oxygen vacancy doping, in which the optical bandgap is suppressed due to improved orbitals hybridization and intraband transition. Moreover, through synergistic ion‐electron doping, the selective control of the gating area and pattern is realized in the micrometer or even nanometer scale with extremely distinct physical properties, which can be employed to fabricate novel optical and electronic devices. The result greatly deepens the understanding of the underlying physics and formation mechanism of transparent conducting oxide (TCO) materials. It is envisioned that this work would provide a new pathway to design other potential optoelectronic materials with novel functionalities.

Synergy of structural engineering and VO2 self-transformation enables ultra-high areal capacity cathodes for zinc-ion batteries

The development of cathodes with high areal capacities is a prerequisite for realizing the practical application of zinc-ion batteries (ZIBs). However, the slow ion (de)intercalation kinetics and the highly tortuous ion transport channels in the traditionally blade-coated electrodes limit the practical areal capacities of the ZIB cathodes below 3 mAh cm−2. In this work, multi-stage pore structures, including through-holes perpendicular to the electrode and submicron-scale channels along the radial direction of the printed filaments, are obtained through polyvinylidene difluoride (PVDF) phase separation assisted 3D printing procedure. In this novel electrode material, the porous network enables fast electron/ion transport and improves the accessibility of active materials for thick electrodes with high active material loadings. More importantly, a phase self-transformation of VO2 to a high oxidation state of V5O12∙6H2O is achieved by regulating the charging voltage, which significantly enhances the zinc storage capacity and provides smoother channels for fast ion (de)intercalation. With these unique features, the 3D printed VO2 cathode with a mass loading of 8.9 mg cm−2 demonstrates a high specific capacity of 478.1 mAh g−1 at 1 A g−1 and a stable life cycle for 1000 cycles at 4 A g−1. When the mass loading is increased to 29.6 mg cm−2, the electrode is still able to deliver an ultra-high areal capacity of 16.8 mAh cm−2. The strategies adopted in this work greatly boost up the performance of VO2 cathodes, especially the high areal capacity, by combining structural engineering and material activity regulation.

Investigation of fracture patterns and effect on capacity in all-solid-state batteries based on peridynamic electro-chemo-mechanical model

The evolution of complex fracture patterns of composite electrodes in all-solid-state batteries (ASSBs) during electrochemical cycles is one of the main phenomena driving capacity degradation. Such fracture patterns in active materials usually involve cracks with various orientations. While conventional wisdom usually treats fracture as ultimate failure of materials in many scenarios, the effect of crack in batteries is worth further investigation. Here, a concurrently coupled electro-chemo-mechanical model based on peridynamics has been developed to study fracture patterns and electrochemical performances of composite anodes during processes of charge and discharge. The framework consists of a classic bond-based peridynamic mechanical model, an electrochemical model, and a coupling technique to reflect the interaction between them in a bidirectional manner. The bond-based peridynamic mechanical model considers the active material’s elastic–plastic deformation and the solid electrolyte’s elastic deformation. The fracture energies of the active material, the solid electrolyte, and the interface are also incorporated into this model. The electrochemical model considers the volume expansion of the active material caused by the intercalation of lithium ions and the Butler–Volmer relation of charge transfer on the interface. Various parametric analyses are performed using this modeling framework to investigate the effects of external pressure, fracture energies of active material and solid electrolyte, and Young’s modulus on fracture patterns and electrochemical performances. It is found that different material parameters result in distinct fracture patterns in the active material with radial cracks or circumferential cracks, thus profoundly affecting the rates of charge and discharge. This work demonstrates the importance of considering the complex fracture patterns in electrode materials of batteries and provides insights for selecting more suitable electrode materials to mitigate capacity degradation.

Zn-Doped MnO2 microflake pseudocapacitive cathode on Ni(OH)2/Ni-Foam substrate as a promising charge storage material

Zn-doped MnO2 microflakes cathode material on Ni(OH)2/Ni foam has been synthesized and characterized as well as tested its electrochemical performances in 3 M KOH solution. The present work varies the amounts of Zn dopant in MnO2 system to improve its capability in energy storage. Material identification has been simply confirmed with XRD, SEM, TEM, and XPS analysis. It is expected the Zn dopant will induce surface defects such as ZnMn2- or ZnMn0 and oxygen vacancy, leading to enhanced charge storage efficiency. In addition, XPS analysis reveals the existence of positively charged oxygen vacancy and the surface charge of ZnMn2- or ZnMn0 induce different surface oxidation states of Mn2+ and Mn4+. The oxidation states of Mn could accommodate the redox reactions involving ion adsorption and intercalation during pseudocapacitive charge and discharge processes. Substituting Zn into Mn sites is optimized with MnZn-1.5 which reaches a specific capacitance of 1601F/g at a 0.4 VAg/AgCl in KOH solution. This work demonstrates a promising material system for supercapacitor applications using Zn doping with a simple preparation process to support a large-scale application.

Controllable Design of Metal-Organic Framework-Derived Vanadium Oxynitride for High-Capacity and Long-Cycle Aqueous Zn-Ion Batteries.

Introducing N atoms in vanadium oxides (VOx) of aqueous Zn-ion batteries (ZIBs) can reduce their bandgap energy and enhance their electronic conductivity, thereby promoting the diffusion of Zn2+. The close-packed vanadium oxynitride (VON) generated often necessitates the intercalation of water molecules for restructuring, rendering it more conducive for zinc ion intercalation. However, its dense structure often causes structural strain and the formation of by-products during this process, resulting in decreased electrochemical performance. Herein, carbon-coated porous V2O3/VN nanosheets (p-VON@C) are constructed by annealing vanadium metal-organic framework in an ammonia-contained environment. The designed p-VON@C nanosheets are efficiently converted to low-crystalline hydrated N-doped VOx during subsequent activation while maintaining structural stability. This is because the V2O3/VN heterojunction and abundant oxygen vacancies in p-VON@C alleviate the structural strain during water molecule intercalation, and accelerate the intercalation rate. Carbon coating is beneficial to prevent p-VON@C from sliding or falling off during the activation and cycling process. Profiting from these advantages, the activated p-VON@C cathode delivers a high specific capacity of 518 mAh g-1 at 0.2 A g-1 and maintains a capacity retention rate of 80.9% after 2000 cycles at 10 A g-1. This work provides a pathway to designing high-quality aqueous ZIB cathodes.

Deciphering Anion-Modulated Solvation Structure for Calcium Intercalation into Graphite for Ca-Ion Batteries.

Co-intercalation reactions make graphite a feasible anode in Ca ion batteries, yet the correlation between Ca ion intercalation behaviors and electrolyte structure remains unclear. This study, for the first time, elucidates the pivotal role of anions in modulating the Ca ion solvation structures and their subsequent intercalation into graphite. Specifically, the electrostatic interactions between Ca ion and anions govern the configurations of solvated-Ca-ion in dimethylacetamide-based electrolytes and graphite intercalation compounds. Among the anions considered (BH4 -, ClO4 -, TFSI- and [B(hfip)4]-), the coordination of four solvent molecules per Ca ion (CN=4) leads to the highest reversible capacities and the fastest reaction kinetics in graphite. Our study illuminates the origins of the distinct Ca ion intercalation behaviors across various anion-modulated electrolytes, employing a blend of experimental and theoretical approaches. Importantly, the practical viability of graphite anodes in Ca-ion full cells is confirmed, showing significant promise for advanced energy storage systems.

Deciphering Anion‐Modulated Solvation Structure for Calcium Intercalation into Graphite for Ca‐Ion Batteries

AbstractCo‐intercalation reactions make graphite a feasible anode in Ca ion batteries, yet the correlation between Ca ion intercalation behaviors and electrolyte structure remains unclear. This study, for the first time, elucidates the pivotal role of anions in modulating the Ca ion solvation structures and their subsequent intercalation into graphite. Specifically, the electrostatic interactions between Ca ion and anions govern the configurations of solvated‐Ca‐ion in dimethylacetamide‐based electrolytes and graphite intercalation compounds. Among the anions considered (BH4−, ClO4−, TFSI− and [B(hfip)4]−), the coordination of four solvent molecules per Ca ion (CN=4) leads to the highest reversible capacities and the fastest reaction kinetics in graphite. Our study illuminates the origins of the distinct Ca ion intercalation behaviors across various anion‐modulated electrolytes, employing a blend of experimental and theoretical approaches. Importantly, the practical viability of graphite anodes in Ca‐ion full cells is confirmed, showing significant promise for advanced energy storage systems.

Freeze-sonication delamination method of high crystalline-quality MXene with high yield

MXene has attracted broad attention for its unique physicochemical properties and has flourished in many research areas. Since MXene obtained by high crystalline-quality MAX phase has excellent stability and properties, the etching of high crystalline-quality MAX phase and delamination into monolayer will become an inevitable trend. However, the delamination of the high crystalline-quality MXene is significantly more challenging than conventional MXene because of the more vital van der Waals forces of the more regular interlayer structure. Here, we propose a freeze-sonication delamination (FSD) strategy that can solve the difficult problem of efficiently exfoliation of high crystalline-quality MXene. The principle is to utilize the synergistic effect of ultrasound and ionic intercalation to allow a large number of water molecules to penetrate into the interlayer, which results in volume expansion, and then ultrasound to obtain monolayer MXene in a frozen state. This method not only increases the yield of high crystalline-quality monolayer MXene but also prevents the size reduction and the nanosheet destruction. The yield of monolayer MXene reached 74.2 % with a concentration of 19.8 mg/mL after six FSD cycles (the time of ultrasound treatment is 5 min after per freeze). Meanwhile, under the protection of ice, the obtained monolayer MXene has a larger size with more complete nanosheets than ultrasound-delaminated MXene. Supercapacitors made of high crystalline-quality MXene exhibits excellent gravimetric capacitance of 261.1 F/g and satisfactory cycling stability.

Dual–ion symmetric hybrid supercapacitor built by vanadium oxide with expanded interlayers: The intercalation of cation–anion pair and reversible redox of anion excited by Al3+

The development of aluminum ion batteries (AIBs) is retarded by the low capacity of intercalation cathode and ineffective aluminum dissolution/deposition at Al anode. To solve the issues, benzoquinone(BQ)–preinserted hydrated vanadium oxide formulated as (BQ)0.04V2O5·0.87H2O (BQ-VO) with a large interlayer spacing of 13.3 Å was synthesized, which was used as both cathode and anode with Al(ClO4)3 acetonitrile (AN) electrolyte to fabricate a symmetric aluminum–ion supercapacitor. BQ-VO delivers a large capacity of ~152 mAh g−1 at 0.2 A g−1 in the range of 0–1.5 V, which is associated with the intercalation of ion (such as ClO4−, Al3+ or Al3+ − ClO4− pair) into BQ-VO and the reversible redox reaction of ClO4− ↔ Cl−, giving rise to a novel symmetric dual–ion hybrid supercapacitor. The reversible conversion of ClO4− ↔ Cl− is not observed in NaClO4 AN electrolyte, which is only excited by Al3+, leading to a continuous increasing capacity in the early stage of the cycling test. On the contrary, in the NaClO4 AN electrolyte, BQ-VO illustrates a surface-controlled capacitive performance with excellent cycling stability. Molecular dynamic (MD) simulations reveal that Al3+ and Na+ possess different solvation/anion sheaths, leading to different electrochemical performances of BQ-VO in the Al(ClO4)3 and NaClO4 electrolytes. The present work provides a routine to utilize the redox reaction of halide for energy storage.

Electron beam-assisted exfoliation of boron nitride and covalent functionalization

A facile, scalable exfoliation technique is still required for further modification to cater to any potential application for two-dimensional boron nitride. This paper discusses the radiation-assisted exfoliation of hexagonal boron nitride (h-BN) using electron beam irradiation and followed by functionalization with phosphoric acid 2-hydroxyethyl methacrylate ester (PA) to facilitate targeted applications. h-BN is dispersed in NaOH solution and subjected to mild sonication to facilitate ion intercalation between the layers. The sonicated h-BN solution was exposed to electron beam irradiation for BNNS exfoliation. The degree of exfoliation was measured in terms of d-spacing derived from XRD using Bragg's law. The effect of irradiation dose, energy, NaOH concentration, and mass of h-BN, on exfoliation degree was investigated. XRD analysis was used to compute the d-spacing, crystallinity, and crystal size of h-BN after irradiation. The d-spacing attained for pristine h- BN was 0.334 nm, however it increases to 0.337 nm upon irradiation at 100 kGy doses, 3 MeV of energy, and 0.1 g of h-BN in 80 mL of 30 % NaOH solution. The occurrence of radiation-assisted exfoliation and its mechanism were supported by FTIR, TGA, Raman, FESEM, XPS, AFM, and TEM analyses. The exfoliated BN was functionalized with PA. The degree of functionalization was measured by phosphoric density (mmol/g) via the acid-base titration method. The effect of PA concentration, reaction temperature and mass on phosphoric density was also investigated. The highest phosphoric density attained was approximately 13.32 mmol/g at 10 % PA, 0.1 g of exfoliated BN, 80 °C, and 5 h. The incorporation of PA onto exfoliated BN was further confirmed by XRD, FTIR, TGA, Raman, FESEM-EDX, and XPS analyses. Conclusively, this study reveals a facile dual-step exfoliation and functionalization technique of h-BN nanosheet through radiation assisted exfoliation technique.

Two-electron conversion nitroxide radicals-based electrode synergistically enhancing charge storage in water-in-salt electrolyte

Water-in-salt electrolytes (WISEs) are attractive in aqueous batteries due to their non-flammability, environmental friendliness, and wide electrochemical stability window. Stable nitroxide radicals with fast electron transfer rate and good cycling stability are promising electrode materials applied for WISEs, while their limited conductivity and high solubility in electrolytes are still challenges. Here, porous carbon with high specific area is used as conductive substrate for the deposition of 4-amino-TEMPO (TEMPO = 2,2,6,6-tetramethylpiperidine-1-oxyl), and MXene nanosheets are employed as their conductive binder to construct freestanding electrode with “hyacinth bean-like” structure. Nitroxide radicals undergo a two-step two-electron reversible redox reaction and MXene exhibits pseudocapacitive ion intercalation, leading to synergistically enhanced discharge capacity in WISE (19.8 m LiCl). The incorporated redox active nitroxide radicals in MXene/porous carbon-TEMPO electrode boost the surface pseudocapacity and the rationally designed three-dimensional structure further facilitates the ions diffusion and electrons transfer, endowing the composite electrode with fast charge storage kinetic. This work provides a promising potential for the design and fabrication of high-performance aqueous batteries.

Mn-doped V2O5@rGO towards high-performance electrode materials for aqueous zinc-ion supercapacitors

In order to address the diverse energy storage requirements, there is an urgent need to fabricate supercapacitors with high specific capacitance, long cycle life, high power density and high energy density. Among various transition metal oxide materials, vanadium pentoxide emerges as a promising candidate for cathode materials in supercapacitors. Herein, we report an ion intercalation strategy to synthesize Mn-doped V2O5 (MnVO) and recombine it with reduced graphene oxide (rGO) to form Mn-doped V2O5@rGO (MnVO@rGO) hybrids with special hierarchical structure. During the hydrothermal process, Mn2+ gradually inserts into the layer spacing of V2O5 to form nanobelts, which could be cross-linked with graphene nanosheets to form MnVO@rGO 3D skeleton network. This unique structure enables the MnVO@rGO electrode to exhibit excellent specific capacitance of 1120 F g−1 at 0.2 A g−1. Outstanding cycling performance is demonstrated by achieving a capacity retention rate of 91.5 % after 2000 cycle. The symmetrical supercapacitor device assembled with MnVO@rGO as both positive and negative electrodes exhibits an energy density of 150.75 and 77.5 W h Kg−1 at power density of 450 and 9000 W kg−1, respectively. Moreover, DFT calculations also have been employed to account for the improved electrochemical performances of MnVO@rGO. Besides, the excellent electrochemical performances of MnVO@rGO indicate that it has broad application prospects in future energy storage devices.

Lithium Ion Intercalation-Induced Metal-Insulator Transition in Inclined-Standing Grown 2D Non-Layered Cr2S3 Nanosheets.

Gate-controlled ionic intercalation in the van der Waals gap of 2D layered materials can induce novel phases and unlock new properties. However, this strategy is often unsuitable for densely packed 2D non-layered materials. The non-layered rhombohedral Cr2S3 is an intrinsic heterodimensional superlattice with alternating layers of 2D CrS2 and 0D Cr1/3. Here an innovative chemical vapor deposition method is reported, utilizing strategically modified metal precursors to initiate entirely new seed layers, yields ultrathin inclined-standing grown 2D Cr2S3 nanosheets with edge instead of face contact with substrate surfaces, enabling rapid all-dry transfer to other substrates while ensuring high crystal quality. The unconventional ordered vacancy channels within the 0D Cr1/3 layers, as revealed by cross-sectional scanning transmission electron microscope, permitting the insertion of Li+ ions. An unprecedented metal-insulator transition, with a resistance modulation of up to six orders of magnitude at 300 K, is observed in Cr2S3-based ionic field-effect transistors. Theoretical calculations corroborate the metallization induced by Li-ion intercalation. This work sheds light on the understanding of growth mechanism, structure-property correlation and highlights the diverse potential applications of 2D non-layered Cr2S3 superlattice.

Upgrading anode graphite from retired lithium ion batteries via solid-phase exfoliation by mechanochemical strategy

Vast quantities of anode graphite from waste lithium ion batteries (LIBs), as a type of underrated urban mine, has enormous potential to be exploited for resource recovery. Herein, we propose a benign process integrating low-temperature pyrolysis and mechanochemical techniques to upcycle spent graphite (SG) from end-of-life LIBs. Pyrolysis at 500 °C leads to about 82.2 % PVDF dissociation in thermal treated graphite (TG). Solid-phase exfoliation via ball milling assisted by urea successfully produces abundant graphite flakes and a small amount of monolayer graphene nanosheet at the edge of mechanochemically processed graphite (MG). Subsequent rinsing removes the residual LiF salts. High purity and unique edge structural features of the as-prepared MG offer more active sites and storage reservoir for intercalation and de-intercalation of lithium ions, resulting in enhanced lithium-ion diffusion kinetics, excellent reversible specific capacity and desirable rate capability. Inspiringly, MG exhibits a remarkably enhanced initial specific charge capacity of 521.3 mAh g−1 during the first charge–discharge, and only declines from 569.9 mAh g−1 to 538 mAh g−1 with slight attenuation after 50 consecutive cycles at 0.1 A/g, indicating satisfactory cycle stability. Additionally, the purification and reconstruction mechanism for MG have been illustrated in detail. This study offers a green strategy to reconstruct and upgrade anode graphite from LIBs, which can realize sustainable waste management.

Understanding the Coupling Mechanism of Intercalation and Conversion Hybrid Storage in Lithium-Graphite Anode.

Anodes with high capacity and long lifespan play an important role in the advanced batteries. However, none of the existing anodes can meet these two requirements simultaneously. Lithium (Li)-graphite composite anode presents great potential in balancing these two requirements. Herein, the working mechanism of Li-graphite composite anode is comprehensively investigated. The capacity decay features of the composite anode are different from those of Li ion intercalation in Li ion batteries and Li metal deposition in Li metal batteries. An intercalation and conversion hybrid storage mechanism are proposed by analyzing the capacity decay ratios in the composite anode with different initial specific capacities. The capacity decay models can be divided into four stages including Capacity Retention Stage, Relatively Independent Operation Stage, Intercalation & Conversion Coupling Stage, Pure Li Intercalation Stage. When the specific capacity is between 340 and 450mAh g-1, its capacity decay ratio is between that of pure intercalation and conversion model. These results intensify the comprehensive understandings on the working principles in Li-graphite composite anode and present novel insights in the design of high-capacity and long-lifespan anode materials for the next-generation batteries.