High-capacity Anode Materials Research Articles

Mechanistic Insight into Ion Transport in Layered Materials for Sodium-Ion Rechargeable Batteries

As a feasible alternative to Li-ion batteries (LIBs), Na-ion batteries (SIBs) are an emerging energy storage solution for electric vehicles, electronic devices, and large grid level energy storage systems. The TMD (transition metal dichalcogenides) component MoS2 and the NASICON structured-type NaxTi2(PO4)3 are two materials of interest as next-generation SIB materials. MoS2 is a 2D layered material with a graphene-like structure that can be used as a high-capacity anode or Na-ion host material as well as an electrocatalyst. Our experiments on the Al-doped 1T phase of MoS2 on reduced graphene oxide (rGO) nanosheets support demonstrated good electrochemical performance, such as 450, 400, etc. mAh/g at current densities of 0.05, 0.1 A/g. Experiments further revealed that Na-ion intercalation supports increased interlayer distance in 1T Al-MoS2@rGO, resulting in a stable phase structure. Density functional theory (DFT)-based simulations are utilized to study the intercalation properties of Na+ ions, in addition to GITT, EIS, and CV analysis. In this study, the Na-ion diffusion mechanism for 1T Al-MoS2@rGO interface and Al-MoS2-MoS2 interlayer host structure is explored. According to the experiments, the host structure is doped with 5% Al at a specific stable site, and Na-ions are introduced to the interface and interlayer (an interlayer distance of 9.3 Å is chosen, as estimated by the experiments). The Na-ion is hopped in both structures, and activation energies (Eact) are calculated to be 57.9 kJ/mol and 40.3 kJ/mol in the 1T Al-MoS2@rGO interface at migration distances of 0-2 Å and 2-4 Å, respectively. The related Na-ion diffusion coefficients are computed using an Arrhenius type fit to be in the order of 10-13 cm2/s and 10-10 cm2/s. Similarly, the Na-ion activation energy barriers in the 1T Al-MoS2-MoS2 interlayer are estimated to be between 49.8 and 59.6 kJ/mol, with related diffusivity ranging between 10-11 and 10-13 cm2/s. The outcomes of the DFT simulations are consistent with those of our experiments. The Na-ion transport properties in the NaTi2(PO4)3 bulk structure via the Na-ion vacancy assisted mechanism are investigated using MD simulations and DFT. The self-diffusion coefficients (DNa+) of bulk are examined, and then the lattice strain effect is proposed to alter its transport properties by introducing the lattice strain in uniaxial (x, y, z) and biaxial (xy, xz, yz) directions, and the changes are compared for strained and unstrained structure. In comparison to the unstrained structure at 323K, a significant improvement by 1-2 order change in DNa+ values (10-8 cm2/s - 10-10 cm2/s) is measured. DFT is also used to investigate the diffusion mechanisms along the various planes (line [001], [100], and [010]) of the bulk NaTi2(PO4)3 structure and Eact is determined along those directions, respectively. The values obtained are consistent with the experimental value ranges obtained for similar materials. In addition, a mixed ion-system is represented by inserting Li-ions at the surface of a NaTi2(PO4)3 structure, yielding the formula LixNay-xTi2(PO4)3. The sluggish kinetics of Li-ion in the NaTi2(PO4)3 structure were proposed by MD analysis. This corresponds well with experimental data that the NaTi2(PO4)3 framework exhibits preferred Na-ion insertion when cycling in mixed-ion electrolytes of varied concentrations, implying slow diffusion of Li-ions in the bulk Li+/Na+ mixed-ion crystal.

Rational Design of LixSiOy-Based Pre-SEI through Thermal-Evaporated Li-Metal Prelithiated SiOx Anode Enabling Extremely Stable and High-Rate Lithium Microbatteries

Recently, silicon oxides families (SiOx) have been commercialized as high capacity anode materials growing rapidly owing to their natural resource abundance and low-cost.(1) However, both the poor electron/ionic conductivity, and quite low initial coulombic efficiency (ICE) (normally < 60%) limits the further development into next generation SiOx anodes. (2) To address these two critical issues, various pre-lithiation strategies have emerged and systematically investigated with significant progress.(3, 4) Here, we provide a facile approach to prelithiate SiOx films by optimizing RF power and precisely controlling Li-metal deposition to overcome the current challenges of SiOx anodes. We found a strong correlation between the surface chemical state of SiOx and the pre-formation of LixSiOy SEI layers. The optimal prelithiation strategy achieves remarkable rate performance of 72.8% at 20C, and extremely excellent long-term cycling performance of 54.2% over 5000 cycles at 10C. This study significantly promotes SiOx-based anodes development, offering a promising strategy for extreme fast-charging and long-term stability not only overcoming the limitations in microbattery but scalable to practical electrodes.Reference: Q. Mai, Chem. Soc. Rev., 48, 285 (2019). M. L. Jiao, Y. F. Wang, C. L. Ye, C. Y. Wang, W. K. Zhang and C. Liang, J. Alloy. Compd., 842, 21 (2020). R. M. Zhan, X. C. Wang, Z. H. Chen, Z. W. Seh, L. Wang and Y. M. Sun, Adv. Energy Mater., 11, 20 (2021). X. Q. Min, G. J. Xu, B. Xie, P. Guan, M. L. Sun and G. L. Cui, Energy Storage Mater., 47, 297 (2022).

Zinc Dicyanamide: A Potential High-Capacity Negative Electrode for Li-Ion Batteries.

We demonstrate that the β-polymorph of zinc dicyanamide, Zn[N(CN)2]2, can be efficiently used as a negative electrode material for lithium-ion batteries. Zn[N(CN)2]2 exhibits an unconventional increased capacity upon cycling with a maximum capacity of about 650 mAh·g-1 after 250 cycles at 0.5C, an increase of almost 250%, and then maintaining a large reversible capacity of more than 600 mAh·g-1 for 150 cycles. Such an increased capacity is primarily attributed to the increased level of activity in the conversion reaction. A combination of conversion-type and alloy-type mechanisms is revealed in this anode material via advanced characterization studies and theoretical calculations. This mechanism, observed here for the first time in transition-metal dicyanamides, is probably responsible for the outstanding electrochemical performance. We believe that this study guides the development of new high-capacity anode materials.

Amorphous AlPO4 Layer Coating Vacuum Thermal Reduced SiOx with Fine Silicon Grains to Enhance the Anode Stability.

Micrometer-sized silicon monoxide (SiO) is regarded as a high-capacity anode material with great potential for lithium ion batteries (LIBs). However, the problems of low initial Coulombic efficiency (ICE), poor electrical conductivity, and large volume change of SiO inevitably impede further application. Herein, the vacuum thermal reduced SiOx with amorphous AlPO4 and carbon double-coating layers is used as the ideal anode material in LIBs. The vacuum thermal reduction at low temperature forms fine silicon grains in the internal particles and maintains the external integrity of SiOx particles, contributing to mitigation of the stress intensification and the subsequent design of multifunctional coating. Meanwhile, the innovative introduction of the multifunctional amorphous AlPO4 layer not only improves the ion/electron conduction properties to ensure the fast reversible reaction but also provides a robust protective layer with stable physicochemical characteristics and inhibits the volume expansion effect. The sample of SiOx anode shows an ICE up to 87.6% and a stable cycling of 200 cycles at 1 A g-1 with an initial specific capacity of 1775.8 mAh g-1. In addition, the assembled pouch battery of 1.8 Ah can also ensure a cycling life of over 150 cycles, demonstrating a promising prospect of this optimized micrometer-sized SiOx anode material for industrial applications.

A Novel Gelatin Binder with Helical Crosslinked Network for High-Performance Si Anodes in Lithium-Ion Batteries.

Silicon(Si) is a promising anode material for lithium-ion batteries, but its large volume expansion during cycling poses a challenge for the binder design. In this study, a novel gelatin binder is designed and prepared with a helical crosslinked network structure. This gelatin binder is prepared by enzymatic crosslinking and immersion in Hofmeister salt solution, which induces the formation of network and helical secondary structures. The helical crosslinked network structure can be analogous to a spring group system to effectively dissipate the stress and strain caused by the Si expansion. The gelatin binder is further partially carbonized by low-temperature pyrolysis, which improves its conductivity and stability. The Sianode with the optimized gelatin binder exhibits high initial coulombic efficiency, excellent rate performance, and long-term cycling stability. This study provides an innovative approach for the preparation of high-performance Si anodes, namely by controlling the molecular configuration of the binder to significantly improve the cycle stability, which can also be applied to other high-capacity anode materials that suffer from large volume changes during cycling.

Ultrahigh Potassium Storage Capacity of Ca2Si Monolayer with Orderly Multilayered Growth Mechanism.

As the rising renewable energy demands and lithium scarcity, developing high-capacity anode materials to improve the energy density of potassium-based batteries (PBBs) is increasingly crucial. In this work, a unique orderly multilayered growth (OMLG) mechanism on a 2D-Ca2Si monolayer is theoretically demonstrated for potassium storage by first-principles calculations. The global-energy-minimum Ca2Si monolayer is a semiconductor with isotropic mechanical properties and remarkable electrochemical properties, such as a low potassium ion migration energy barrier of 0.07eV and a low open circuit voltage ranging from 0.224 to 0.003V. Most notably, 2D-Ca2Si demonstrates an ultrahigh theoretical specific capacity of 5459mAhg-1 and a total specific capacity of 610mAhg-1, reaching up to 89% of the capacity of a potassium metal anode. Remarkably, the OMLG mechanism facilitates stable, dendrite-free deposition of hcp-K metal layers on the 2D-Ca2Si surface, where the ultrahigh and gradually converging lattice match as the layers increase is the key to achieving theoretically near-infinite growth. The study theoretically demonstrates the Ca2Si monolayer a highly promising anode material, and offers a novel potassium storage strategy for designing 2D anode materials with high specific capacity, rapid potassium-ion migration, and good safety.

In-situ synthesis of Fe3O4@Fe3C nanoparticles with heterostructures embedded in the N-doped porous carbon for high-performance lithium ion batteries

Metal oxides (Fe3O4) have attracted immense attention as high-capacity anode materials for high-performance electrochemical energy storage systems. However, the large structural change and sluggish reaction kinetics in the lithiation and delithiation reactions critically limit their practical development. Here, we design a novel composite consisting of Fe3O4@Fe3C nanoparticles embedded in N-doped porous carbon (Fe3O4@Fe3C-NPC) for lithium ion batteries. Benefiting from the synergistic effect of heterostructures, the Fe3O4@Fe3C-NPC delivers high reversible capacities (911.9 mAh g−1 at 0.2 A g−1, 319.6 mAh g−1 at 5.0 A g−1). The formed heterointerfaces can build an internal electric field, which help to improve reaction kinetics with fast ion diffusion kinetics and low charge transfer resistance. Furthermore, the Fe3O4@Fe3C-NPC//LiFePO4 full cell also displays great performance. The structural design concept and efficient synthesis method in the work can be extended to construct metal oxide/carbide heterostructures for anode materials.

Lithium-Ion battery silicon Anodes: Surface engineering with novel additives for enhanced ion and electron transport

Silicon (Si) stands as a promising candidate for high-capacity anode materials in the next-generation lithium-ion batteries (LIBs) due to extremely high specific capacity. However, silicon application is hindered by its inherently poor electron and ion conductivities, as well as structural instability during the repeated charging/discharging. To address these challenges, a novel functional surface modification agent, diethylenetriaminepenta(methylenephosphonic) acid (DTPMP), was decorated on the surface of silicon particles for the first time. The experimental results demonstrate that the DTPMP effectively enhances the cohesion between nano Si particles. This study combines experimental observations with theoretical calculations to analyze the nucleophilic and electrophilic sites of DTPMP and carboxymethyl cellulose (CMC), elucidating the existence state of DTPMP on the nano Si surface. Furthermore, by examining the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO), along with the electrostatic potential (ESP) of DTPMP and solvent molecules in conjunction with Li+, the impact of the phosphate group on the diffusion of Li+ and electrons at the nano Si surface was studied. The electron density difference (EDD) maps for DTPMP and CMC reveal that DTPMP exhibits a more pronounced response in the presence of an electric field, suggesting its enhanced role in facilitating Li+ diffusion. This research offers a novel perspective on enhancing the electrochemical performance of nano Si surfaces, paving the way for the development of advanced LIBs with improved energy storage capabilities.

Mechanistic insight into the impact of dry-state prelithiated SiOx thin-film anode toward extremely fast-charging and long-term stability

Silicon suboxides (SiOx) have achieved partial success in commercialization as high-capacity anode materials to replace graphite because of optimal electrochemical properties over silicon. Unfortunately, the further development has been sluggish, jeopardizing the urgent need of green energy. The daunting challenges to tackle include low initial coulombic efficiency (ICE) and low charging rate due to poor electron and ionic conductivity. In the context of thin film microbattery, we propose to precisely control the chemical states of SiOx films through varying sputtering power followed by dry-state pre-lithiation through Li-metal thermal evaporation, superior to the current pre-lithiation approaches for SiOx thin-film anodes. We addressed the leading roles of the surface chemical states of the as-deposited SiOx in the formation of the high ionic conductive Li4SiO4 phase as the pre-solid electrolyte interphase during the proposed dry-state prelithiation process. Ultimately, the prelithiated SiOx successfully mitigated the most confronted issues as low ICE and C-rate limitation, achieving an unprecedented rate performance of 72.8 % at 20 C, and ultra-long-cycle retention of 54.2 % over 5000 cycles at 10 C. These results strongly prove that appropriate pre-lithiation provides tremendous advantages to SiOx thin film anode not only in prolonging electrode stability but also promoting a significant fast-cycling.

The first-principles study of 2D monolayer T-Mo2C as promising anode material for Lithium-ion Batteries

The growing demand for renewable energy technologies emphasizes the necessity for advancements in anode materials to enhance the performance of lithium-ion batteries (LIBs). In this research, we employ first-principles calculations to investigate the properties of a T-Mo2C monolayer proposed as an anode material. Phonon dispersion calculations and ab initio molecular dynamics (AIMD) simulations are conducted to assess the dynamical stability and thermal characteristics of the T-Mo2C monolayer as an anode material. Remarkably low diffusion barriers of 0.029 eV (Li) and 0.01 eV (Na and K) have been identified, facilitating rapid ion mobility. Furthermore, a monolayer of metal ions (M = Li, Na, K) absorbed onto T-Mo2C is explored, revealing a high specific capacity of approximately 1314.37 mAh/g (Li), 262.87 mAh/g (Na), and 32.85 mAh/g (K). The average open circuit voltage is determined to be 0.08 V (Li), 0.68 V (Na), and 2.59 V (K). This research provides a comprehensive overview of T-Mo2C monolayer as a high-capacity anode material, emphasizing its significant contributions to advancing energy storage systems, particularly in the context of LIBs. The findings presented here pave the way for the development of efficient and sustainable energy storage solutions to meet the escalating demands of the renewable energy landscape.

A three-dimensional Ge@C anode with a hollow and micro/nano structure for high-capacity lithium-ion battery

Aiming at the key issues of low intrinsic conductivity and large volume expansion during the cycling existed in high-capacity Ge anode material system, a micro/nano structured Ge@C hybrid material was designed and prepared through a facile and controllable method. The as-prepared micron conductive cage with a dodecahedral structure is composed of interconnected ultra-thin walled Ge nanotubes encapsulated in the porous N-containing carbon network, which can not only reserve more buffer space for the volume expansion of Ge and assist in building a stable SEI film during the cycling, improves the conductivity and stability of the material, but also provide a rich and penetrating channel for the transmission of ions, realizing high dynamics. When applied to the anode of lithium-ion battery, the three-dimensional micro/nano structured germanium-based hybrid material (Ge-3D@C) delivers a high initial specific capacity of 1500 mAh g−1 at 0.2 A g−1, and after 350 cycles, it can still maintain a high reversible specific capacity of 1147 mAh g−1. Even at high current densities of 1 A g−1 and 2 A g−1, high reversible specific capacities of 752 and 631 mAh g−1 can still be obtained. Importantly, the rational design can be used to prepare Ge hybrids doped with other metals or metal oxides, as well as different structures, by adjusting the layer materials and the types of germanates, so as to adapt to different application environments.

Computational prediction of two dimensional Mo4BC as promising anode material for lithium-ion batteries

The rising demand for high-capacity energy storage systems drives the hunt for cutting-edge lithium-ion batteries. Herein, calculations based on density functional theory have been performed to investigate the properties of two-dimensional (2D) Mo4BC monolayer as an anode material with high stability and storage capacity. Phonon dispersion and ab initio molecular dynamics (AIMD) simulations were performed to determine the dynamic and thermal stability, respectively. A low diffusion barrier of 0.12 eV supports the ultrahigh ionic mobility of Li ions and cycling capability for this material, which is essential for the fast charging/discharging process. In addition, the Li-ion adsorption on Mo4BC shows a high capacity of about 800 mAhg−1 with an average open circuit voltage (Vocv) of 0.03 V. Comprehensive overview of Mo4BC as high-capacity anode material with negligible low diffusion barrier and metallic character provides a significant contribution towards the advancement of energy storage systems such as lithium-ion batteries (LIBs). Our findings suggest Mo4BC as a promising anode material for high-performance LIBs, thus offering valuable insights for exploring innovative anode materials.

Electrochemical performance of P4Se3 as high-capacity anode materials for monovalent and multivalent ion batteries

The increasing need for advanced anode materials with superior performance in rechargeable batteries has driven investigations into cutting-edge energy storage systems. This study delves into the potential of P4Se3 Molecular Cages (MCs) as innovative anode materials for both monovalent and multivalent ion batteries, including Na ion batteries (NIBs), Mg ion batteries (MIBs), Ca ion batteries (CIBs), Al ion batteries (AIBs), and Zn ion batteries (ZIBs) through a comprehensive Density Functional Theory (DFT) and molecular dynamics (MD) based investigations. The analyses encompass the electronic structure, structural stability, electrochemical performance, charge storage mechanisms, and redox properties to offer valuable insights into the potential of P4Se3 as an anode. The DFT calculations unveil critical aspects of adsorption, diffusion, and reaction kinetics in P4Se3 elucidating its potential as high-capacity and suitable anode material. The exothermic reactions between Na, Mg, Ca, Al, and Zn with host P4Se3 highlight its suitability for the intercalation process in monovalent and multivalent ion batteries. Furthermore, calculated storage capacities for NIB, MIB, CIB, AIB, and ZIB are found as 1484.84 mAhg−1, 519.69 mAhg−1, 1410.60 mAhg−1, 593.93 mAhg−1, and 74.24 mAhg−1 respectively. The voltage profiles indicate favorable open circuit voltages (OCV) of 0.31 V, 0.27 V, 0.55 V, and 3.3 V for NIB, MIB, CIB, and AIB respectively. The study employs climbing image nudged elastic band (Cl-NEB) simulations to compute diffusion barriers faced by monovalent and multivalent ions in the host structure. The calculated minimal diffusion barriers of 0.18 eV for NIB, 0.30 eV for MIB, 0.35 eV for CIB, 0.33 eV for AIB, and 0.71 eV for ZIB indicate fast charging capabilities due to efficient ion movement. Furthermore, the respective calculated values of diffusion coefficient are found as 5.27 × 10−10 m2/s, 5.27 × 10−9, 4.0 × 10−10 m2/s, 5.27 × 10−10 m2/s and 5.27 × 10−11 m2/s and respective values of ionic conductivity σ are found as 4.13 × 10−3 S/m, 14.57 × 10−2 S/m, 30.03 × 10−3 S/m, 16.65 × 10−3 S/m and 0.20 × 10−3 S/m for NIBs, MIBs, CIBs, AIBs and ZIBs. The findings of this study point out suitability of P4Se3 as anode material in monovalent and multivalent ion batteries.

In Situ Integration of a Flame Retardant Quasisolid Gel Polymer Electrolyte with a Si-Based Anode for High-Energy Li-Ion Batteries.

Silicon (Si) stands out as a promising high-capacity anode material for high-energy Li-ion batteries. However, a drastic volume change of Si during cycling leads to the electrode structure collapse and interfacial stability degradation. Herein, a multifunctional quasisolid gel polymer electrolyte (QSGPE) is designed, which is synthesized through the in situ polymerization of methylene bis(acrylamide) with silica-nanoresin composed of nanosilica and a trifunctional cross-linker in cells, leading to the creation of a "breathing" three-dimensional elastic Li-ion conducting framework that seamlessly integrates an electrode, a binder, and an electrolyte. The silicon particles within the anode are encapsulated by buffering the QSGPE after cross-linking polymerization, which synergistically interacts with the existing PAA binder to reinforce the electrode structure and stabilize the interface. In addition, the formation of the LiF- and Li3N-rich SEI layer further improves the interfacial property. The QSGPE demonstrates a wide electrochemical window until 5.5 V, good flame retardancy, high ionic conductivity (1.13 × 10-3 S cm-1), and a Li+ transference number of 0.649. The advanced QSGPE and cell design endow both nano- and submicrosized silicon (smSi) anodes with high initial Coulombic efficiencies over 88.0% and impressive cycling stability up to 600 cycles at 1 A g-1. Furthermore, the NCM811//Si cell achieves capacity retention of ca. 82% after 100 cycles at 0.5 A g-1. This work provides an effective strategy for extending the cycling life of the Si anode and constructing an integrated cell structure by in situ polymerization of the quasisolid gel polymer electrolyte.

Pb nanospheres encapsulated in metal–organic frameworks-derived porous carbon as anode for high-performance sodium-ion batteries

Alloying-type anode materials are considered promising candidates for sodium-ion batteries (SIBs) due to their high theoretical capacities. However, their application is limited by the severe capacity decay stemming from dramatic volume changes during Na+ insertion/extraction processes. Here, Pb nanospheres encapsulated in a carbon skeleton (Pb@C) were successfully synthesized via a facile metal–organic frameworks (MOFs)-derived method and used as anodes for SIBs. The nanosized Pb particles are uniformly incorporated into the porous carbon framework, effectively mitigating volume changes and enhancing Na+ ion transport during discharging/charging. Benefiting from this unique architecture, a reversible capacity of 334.2 mAh g−1 at 2 A g−1 is achieved after 6000 cycles corresponding to an impressive 88.2 % capacity retention and a minimal capacity loss of 0.00748 % per cycle. Furthermore, a high-performance full sodium-ion battery of Pb@C//NVPF was constructed, demonstrating a high energy density of 291 Wh kg−1 and power density of 175 W kg−1. This facile MOFs-derived method offers insights into the design of high-capacity alloy-type anode materials using Pb sources, opening up new possibilities for innovative approaches to Pb recycling and pollution prevention.

Unconventionally microspheric quasi-solid electrolyte interface approach for durable and highly reactive phosphorus for lithium-ion storage

Solid electrolyte interface (SEI) film is the most important separation layer between nonaqueous electrolytes and anodes to protect anode from corrosion and maintain continuous ionic diffusion tunnels. However, SEI film, especially for high-capacity anode materials, is still confined to continuous and stable ionic conductive layer despite the conventional SEI film is intrinsically poor to resist against the drastic volumetric changes of active centers. Herein, an unconventional spheric quasi-SEI film is thus strategically configured on cost-effective red phosphorus electrode materials by moderate phosphorylation combined with pore-forming process. Microstructure adjustment from solid microspheres structure to hollowed core–shell spheres is visibly taken place on this amazing spheric quasi-SEI film during the stabilization. Benefiting from the highly activated surface with weakened PP bond strength and the strengthened binding force between phosphorus and binders, the optimized phosphorus anode presents an outstanding long-term durability with a high discharge capacity of 1126.4 mAh/g over 400 cycles at 200 mA g−1 even at a high phosphorus load ratio of 70 wt%. This revolutionary configuration of quasi-SEI film provides high-capacity anode materials subject to large volumetric changes an unconventional approach from dependence on conductive framework/matrix.

Remarkably improved cycling stability of commercial micron-sized silicon enabled by a novel organic/inorganic hybrid binder

Silicon (Si) anode with ultra-high capacity and low cost are highly desirable for next-generation high-energy lithium-ion batteries, whereas suffers from severe volume change that causes rapid capacity decay upon lithiation/delithiation. The development of high-performance binders to alleviate volumetric expansion and maintain integrity of Si particles remains a significant challenge. Here, reported is a novel organic/inorganic hybrid binder composed of partial neutralized polyacrylic acid (PAAS) and sodium metaborate tetrahydrate (SMTH), which achieves in-situ crosslinking upon drying wafer electrodes. The robust crosslinked network structure with borate ester bonds is successfully attained, and can be modulated by changing the content of sodium metaborate. The strong covalent bond network endows the hybrid binder system with superior mechanical properties and powerful adhesion, which improve the contact and integrity of wafer silicon electrode by suppressing volume expansion and exfoliation, therefore facilitating Li-ion migration and enhancing electrochemical performance. The resulting commercial micro-silicon wafer electrode with PAAS/0.08SMTH binder remains a reversible specific capacity of 1670 mAh g−1 after 150 cycles at 300 mA g−1, largely superior to that prepared with the original PAAS binder because its reversible specific capacity was determined to be only 1046 mAh g−1 under identical conditions. The in-situ crosslinked 3D network structure provides a facile feasible way to improve the high-capacity anode materials for lithium-ion batteries.

Functionalized interfacial cover design toward pure silicon anode for high power density lithium–ion capacitor

A lithium–ion capacitor, comprising a capacitor–type cathode and battery–type anode, exhibits high power and energy density; however, the integration of different charge storage mechanisms in one cell naturally leads to a kinetic mismatch between the two electrodes, reducing the power density and cycle stability. To solve this problem, high–capacity anode materials with thinner electrodes are required. Silicon, with its high specific capacity, is considered a promising anode material with high energy and power density; however, pure Si anodes undergo rapid capacity fading and exhibit increased internal resistance owing to volume changes during cycling. In this study, both sides of the electrode are covered with functional layers consisting of functionalized herringbone–type carbon nanofibers to protect the Si electrode from degradation. The polar functional groups on the nanofibers weakly interact with the native oxide layer of the Si surface and the carboxyl groups of the binder, ensuring stable contact between electrode materials over repeated cycles. Moreover, the conductive functional cover promotes uniform lithium ion fluxes, aiding the formation of a stable solid electrolyte interphase layer. This study investigates the effects of this strategy on pure Si electrodes by surface morphology analysis, assessment of chemical interactions, and electrochemical testing. This approach has the potential to overcome the degradation of Si electrodes and significantly improve the power and energy density of lithium–ion capacitors.

Cobalt-catalyzed soft-hard carbon composite anodes for enhanced sodium-ion storage

Hard carbon is expected to be a high-capacity anode material for sodium-ion batteries (SIBs). However, its Na+ storage performance, especially the low discharge capacity, remains a great challenge. Herein, the soft-hard carbon composite anodes with high degree of graphitization were synthesized via low-temperature pyrolysis (at only 900 °C) of Cobalt-catalyzed perylene tetracarboxylic dianhydride (PTCDA-Co) and cotton, with subsequent removal of cobalt. The composite resulting from a 2:3 mass ratio of soft to hard carbon exhibits a good discharge capacity of 355.81 mAh g−1 at a current density of 50 mA g−1 and an enhanced initial Coulombic efficiency (ICE) of 81.41%. The enhanced electrochemical storage performance of cotton is attributed to the introduction of PTCDA-Co, which creates low-defect graphitic layer, hierarchical porous channels, and carbon shielding coating on hard carbon.

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.