Active Material For Lithium-ion Batteries Research Articles

Analytical computation of stress intensity factor for multi-physics problems

This work presents a methodology for the analytical calculation of the stress intensity factor when the stress distribution on the crack surfaces is non-homogeneous. At first, a polynomial function is used to express the non-homogenous stress distribution. Subsequently, the principle of superposition of effects is applied, and the stress intensity factor is computed by multiplying each polynomial term by its respective geometric factor. Finite element fracture model is used to compute the geometric factor of the single polynomial grade. To explain the method, a spherical body is considered, with central and superficial cracks. Each geometric factor depends on a normalized geometrical parameter (the ratio between the crack length and sphere radius). The proposed methodology is applied to determine the stress intensity factor in the case of a crack driving force caused by diffusive fields, such as the concentration gradient in particles of electrodes active material in lithium-ion batteries. The methodology allows to speed up the fracture computation, then it is used to give electrode design guidelines to limit the fracture likeliness and mechanical degradation in lithium-ion batteries, as well as it is the basis for the development of algorithms assessing the capacity loss and the remaining useful life of lithium-ion batteries in real-time.

Mesoscale mechanical models for active materials in lithium-ion batteries using the multi-particle finite element method

The stability and mechanical integrity of electrode active materials have a significant impact on the safety and performance of lithium-ion batteries (LIBs). The study of mechanical properties of active materials is crucial for the safety design of batteries. Researchers have conducted several models for describing the mechanical behavior of active materials. However, an accurate mechanical model that can reflect the packing structure of active particles and achieve the multiscale mechanical analysis of active materials is still lacking. To bridge this gap, a three-dimensional (3D) mesoscopic model based on the multi-particle finite element method (MPFEM) is proposed in the present study. The numerical simulation results show that the established model is in good agreement with the experimental results for the description of the compression behavior of the active material. Based on the model, the effects of various factors on the mechanical behavior of the active materials are analyzed. The results deepen the understanding of the multiscale mechanical behavior of anode active materials and provide fundamental insights for the future development of safety design for LIBs.

A method for estimating the state of health of lithium-ion batteries based on physics-informed neural network

Data-driven methods have been widely used to estimate the State of health (SOH) of Lithium-Ion batteries (LIBs). However, these methods lack interpretability. In response to this issue, this article proposes a method called Physics-informed neural network (PIFNN) to enhance the interpretability of predictions made by a feedforward neural network (FNN). First, the features are extracted from incremental capacity (IC) curves and differential temperature curves, which can characterize battery aging from different perspectives. Specifically, the peaks of the IC curves (P-IC) reflect the electrochemical reactions that occur during the charge-discharge processes of LIBs. The decline of the P-IC is related to the loss of active materials in LIBs, which is a major cause of the decrease of the SOH. This article converts the monotonous relationship between the P-IC and the SOH into physical constraints to guide the “learning process” of the model. In the prediction process, a physics-constrained secondary “training” is applied to the FNN predictions to further enhance interpretability and improve prediction accuracy. The feasibility of the proposed method is validated using the Oxford and NASA battery datasets. The results indicate that PIFNN effectively improves prediction accuracy and reduces errors to below 1.5 %.

Isostructural dual-ligand-based MOFs with different metal centers in response to diverse capacity lithium-ion battery anode

Metal-organic frameworks (MOFs) have become one of the most promising active materials in lithium-ion batteries (LIBs) due to their designable molecular architecture and tunable functionality. Herein, we report a series of isostructural three-dimensional MOFs of divalent Mn (1), Co (2), and Zn (3), [MII2(H2O)2(4,4′-bipy)(mal)2]n as anode materials for LIBs. The MOFs can be prepared within a few minutes using a facile microwave-heating technique. Investigations on electrochemical properties and performance as active materials for LIBs anodes showed that Co-MOF 2 has higher efficiency than the Mn and Zn congeners, with an excellent specific capacity of 732 mA h g−1 after 200 cycles, which is distinguished electrochemical performance in specific capacity and rate cycle performance over the previous MOF-based materials. First-principles computations revealed the importance of the metal center of MOFs on the Li-ion batteries performance since it is involved in the Li diffusion mechanism.

Degradation Diagnostics of Ni-Rich NMC in Lithium-Ion Batteries Aged in Different Degrading Conditions

Ni-rich Nickel Manganese Cobalt Oxides (NMC) such as LiNi0.6Mn0.2Co0.2O2 (NMC622) and LiNi0.8Mn0.1Co0.1O2 (NMC811) have been widely used as the cathode active materials in lithium-ion batteries (LIB) of electric vehicles due to their high capacity. Thus, we can foresee millions of tons of end-of-life LIB will be accumulated by the next decades. This means that the efficient recycling method of batteries material, especially NMC which has the highest value, should be developed to reduce the cost and increase the efficiency of recycling. Direct recycling which is a novel method to recover cathode active materials in lithium-ion batteries by directly regenerating the chemical and physical structure of cathode materials, skipping the usage of harsh chemical and high energy consumption such as those of other recycling methods i.e. pyrometallurgy and hydrometallurgy. Such an attempt to directly reprocess the spent NMC back into the as good as new cathode requires and understanding what has happened with the materials through the battery life. This implies that the understanding of degradation mechanisms of Ni-rich NMC in different usage conditions is required to up-scale the direct recycling of Ni-rich NMC from degraded lithium-ion batteries.In this work, we investigated failure mode in controlled aged samples of LIB cells to understand the degradation mechanism of NMC622 and NMC811 which are to be connected with the method for direct regeneration. Lithium-ion batteries composed of NMC622 or NMC811 cathode active materials were aged through 1C-rate charge/discharge cycling at 25°C, 45°C or 55°C until 20% or 40% capacity fading. The degraded cells were analyzed via incremental capacity analysis (ICA), volume change measurement, electrochemical impedance spectroscopy (EIS). Ex-situ X-ray powder diffraction (XRD), Scanning electron microscopy analysis (SEM), X-ray photoelectron spectroscopy (XPS) and Inductively Coupled Plasma Optical Emission spectroscopy (ICP-OES) were used to characterize the chemical and physical structure of degraded NMC from each different degrading conditions.Inspection of degraded cells shows that NMC811 cells exhibit larger cell expansion compared to NMC622 cells going through the same degrading condition. EIS results show that the solution resistance (R S) does not vary much between the different cells, while solid-electrolyte interphase resistances (R SEI) were found to increase with temperature at approximately similar level for both NMC622 and NMC811. Fig. 1a and Fig. 1b show the contour plot on the variation of charge transfer resistance (R CT) ratio after and before degradation of NMC622 and NMC811 cells. It can be seen that R CT in NMC811 cells were found to increase for the more highly cycled NMC811 coupled with high temperature. However, temperature does not seem to have much role in the increment of R CT in NMC622. Investigating the change in structure of the cycled NMCs at different temperatures and to level of different degradation, it was found that the results show that at the same level of capacity remaining, NMC622 has a much larger change in c/a ratio after vs. before compared to NMC811.The above impedance analysis coupled with the XRD results imply that the main cause of capacity fade of NMC811 cells is likely due to electrolyte decomposition which generates gas, resulting in high degree of cell expansion, causing loss of electrical contact. The electrolyte decomposition in NMC811 cell is further facilitated by the increment of temperature due to the lower onset potential limit for gas evolution in NMC811, causing more capacity fading in NMC811 cell at high temperature [1]. On the other hand, the capacity fading in NMC622 cells is mainly from the chemical/structural change in the cycled NMC622 cathode.These insight information on the degradation mechanism of LIB cells and structural variation of Ni-rich NMC after ageing in each degrading condition is then further inspected to elucidate the method to effectively directly regenerate both NMC622 and NMC811 cathode in the spent Li-ion batteries.

Exploration of the lithiation/de-lithiation mechanisms of MoSe2@rGO composite anode by operando X-ray absorption spectroscopy

Owing to their inherent advantages of large inter-planar spacing and high-rate capability transition metal di-chalcogenides have attracted much attention as active materials for lithium-ion batteries (LIBs). Herein, MoSe2 and hybrid MoSe2@rGO nanocomposites have been successfully synthesized via hydrothermal processes and have been employed as anodes in LIBs. LIBs with bare MoSe2 and MoSe2@rGO anodes yield initial discharge capacities of 825 mAhg−1 and 979 mAhg−1 respectively at the current density of 100 mAg−1 and 619 mAhg−1 and 850 mAhg−1 respectively at the high current density of 500 mAg−1 in a voltage range of 0.1–3 V respectively. Thus, LIBs with MoSe2@rGO anode showed enhanced electrochemical performance compared to that with bare MoSe2 anode. Further, LIB with MoSe2@rGO anode during the 1st discharge/charge cycle has been investigated by operando X-ray Absorption Spectroscopy (XAS) measurements using synchrotron radiation which provides a detail insight into the intercalation/conversion processes that take place during lithiation/de-lithiation. The operando measurements reveal formation of LixMoSe2 in the initial phase of Li intercalation (discharge process) followed by conversion of LixMoSe2 into Mo, Li2Se and Se. The Li de-intercalation (charging process) shows oxidation of Mo to MoSe2, though the process is found to be not fully reversible and residual unreacted Mo and Se may lead to capacity fading of the LIBs during long cycling. Thus in the present work, the distinctive lithium reaction pathway in LIBs with MoSe2@rGO anodes has been deciphered by synchrotron radiation based operando XAS study.

Modeling Silicon-Dominant Anodes: Parametrization, Discussion, and Validation of a Newman-Type Model

Silicon is a promising anode material and can already be found in commercially available lithium-ion cells. Reliable modeling and simulations of new active materials for lithium-ion batteries are becoming more and more important, especially regarding cost-efficient cell design. Because literature lacks an electrochemical model for silicon-dominant electrodes, this work aims to close the gap. To this end, a Newman p2D model for a lithium-ion cell with a silicon-dominant anode and a nickel-cobalt-aluminum-oxide cathode is parametrized. The micrometer silicon particles are partially lithiated to 1200 mAh gSi−1. The parametrization is based on values from the electrode manufacturing process, measured values using lab cells, and literature data. Charge and discharge tests at six different C-rates up to 2C serve as validation data, showing a root-mean-squared error of about 21 mV and a deviation in discharge capacity of about 1.3%, both during a 1 C constant current discharge. Overall, a validated parametrization for a silicon-dominant anode is presented, which, to the best of our knowledge, is not yet available in literature. For future work, more in-depth studies should investigate the material parameters for silicon to expand the data available in the literature and facilitate further simulation work.

Charge–discharge properties of LiMn 2 O 4 -group positive electrode active materials for lithium-ion batteries using high-throughput experimental screening and machine learning models

Charge–discharge properties of LiMn ₂ O ₄ -group positive electrode active materials for lithium-ion batteries using high-throughput experimental screening and machine learning models

Cross-linked Si@SiC nanowires prepared by vacuum DC arc method embedded in phenolic resin as high electrochemical performance anode active materials for lithium-ion batteries

Cross-linked Si@SiC nanowires prepared by vacuum DC arc method embedded in phenolic resin as high electrochemical performance anode active materials for lithium-ion batteries

Estimation of Crack Formation By Digital-Twin Structure of a Single Secondary Particle

Most of the recently commercialized active materials for lithium-ion batteries (LiB) adopt secondary particles, and most of them are designed by evaluating cell-level electrochemical properties. Therefore, the relationship between particle design and battery performance is not properly understood because it is not possible to grasp the intrinsic properties of the electrode active material. Therefore, a single particle measurement technique has been developed in which a gold or platinum filament having a diameter of several tens of microns is directly contacted with a single particle to evaluate the single particle electrochemical properties. However, since it is a non-sealed battery system, only less-volatile electrolytes can be applied. Also, the experiment is difficult because the contact between particle and filament can easily break down with small vibration. Additionally, there are a lot of particle design parameters such as particle shape, size, and size distribution. Moreover, with operating conditions, the particle design needs to be changed. So, it is challenging to cover all cases by experiment.In this study, digital-twin structure of a single secondary particle was formed using focused ion beam / scanning electron microscope. Using the digital-twin structure, digital-twin electrochemo-mechanical model was developed and more than 99% of accuracy was secured by comparing the voltage profiles with result of single particle measurement technique. Using the well-matched model. Operando analysis of electrochemical properties (State of Lithiation, overpotential, potential, and concentration) and mechanical properties (von Mises stress and strain energy density) were performed. The strain energy density can be the criteria to determine the crack formation by comparing with the fracture toughness which is the strain energy density when the fracture occurs.

Investigating the Particle Formation Mechanism during Precipitation of Ni-Rich Hydroxide Precursors for Cathode Active Materials for Lithium-Ion Batteries

The industrial production of lithium-nickel-cobalt-manganese-oxides (LiNi x Co y Mn z O2, with x+y+z = 1) as cathode active material (CAM) for lithium-ion batteries is conducted by precipitation of a mixed metal hydroxide (Ni x Co y Mn z (OH)2) precursor (referred to as pCAM) in a stirred tank reactor, followed by a calcination of the pCAM with a lithium compound at elevated temperatures in a roller hearth kiln.1 Thereby, the physical properties of the resulting CAM powders are significantly affected by those of the associated pCAM.2 Independent of the material composition, the fluidity and filterability of pCAM and CAM powders deteriorates drastically with decreasing particle size, with non-uniformity of the particle size distribution, and with a deviation from a spherical particle shape.3,4 However, a fluent form of the pCAM and CAM powders is imperative for their further processing in tonnage quantities during pCAM and CAM manufacturing to prevent clogging of the powders in the technical equipment. As frequent cleaning and/or pulverization of the materials between process steps is cost-intensive, an economical and efficient manufacturing of pCAM and CAM powders requires a precise control of particle size and sphericity, which in turn requires an in-depth knowledge of the pCAM particle formation mechanism during the precipitation reaction.To gain a fundamental mechanistic understanding about the pCAM particle formation mechanism, the development of the secondary particle size and morphology during the semi-batch precipitation of Ni0.8Co0.1Mn0.1(OH)2 at various stirring speeds (between 550 and 1350 rpm) was monitored by light scattering and SEM imaging. The evolution of the volume-based median particle size (d 50) over the course of the run time (t run) at the different stirring speeds is depicted in Figure 1a. The d 50 of initial particles generated after 5 minutes as well as the d 50 after 8.75 h depends inversely on the applied stirring speed. After an initial nucleation time, the analysis in Figure 1b shows that the size of the approximatively spherical particles at a given stirring speed (for constant feed flow rates) increases linearly with respect to the third square root of run time/run time to the power of one third (t run1/3 ). Thus, the course of particle growth in each experiment can be divided into two distinct regimes: i) for t run1/3 < 1.0 (stage I in Figure 1b), the particle size remains essentially constant; ii) after this initial phase, for t run1/3 ≥ 1.0 (stage II in Figure 1b), the d 50 increases perfectly linearly with. It is concluded that during stage I, the seeding phase, an increasing number of particles with a constant size are being generated, since the overall volume of formed solid is increasing. In contrast, in stage II, the growth phase, the continuing precipitation occurs via deposition on already existing particles without any further increase in particle number, reflected by the linear relationship between particle size and t run1/3 .In light of these results, it is further demonstrated by SEM imaging that, during the seeding phase (stage I), irregularly shaped secondary particle agglomerates are formed, which in the subsequent growth phase (stage II) increase in size by growth of individual plate-like shaped primary particles. Moreover, it is shown that, at constant process parameters, the degree of turbulence quantified by the average energy input and the Reynolds number, both depending on the stirring speed, governs the initial agglomerate size formed during seeding. This not only dictates the growth rate, thus the final particle size, but also the ability of particles to become spherical over t run. Finally, a particle formation mechanism is proposed and compared to mechanisms described in the literature. Figure 1

Microwave-etched V2C MXene-activated carbon hybrid as a high-performance anode material for lithium-ion batteries

Activated carbon (AC) has been widely utilized as an active material in lithium-ion batteries (LIB) due to its stability and abundance. Nevertheless, the performance of AC anode materials alone falls short of competing with hybrid anode materials, which can attain maximum discharge capacity. Recently, a new two-dimensional (2D) transition metal carbide, MXene, has shown promising performance as an anode in LIB applications. The combination between AC and MXene has proved to improve battery performance previously. Thus, in this study, the electrode was prepared using a hybrid of activated carbon with vanadium carbide MXene (V2C), which was synthesized by etching V2AlC with in situ of hydrochloric acid (HCl) and lithium fluoride (LiF) at 90 °C for 30 min via microwave-assisted hydrothermal technique. The characterization by XRD pattern shows the appearance of V2C MXene peak at 7.23°, indicating the successful etching from V2AlC MAX. The as-prepared AC/V2C_D at ratio 9:1 revealed excellent electrochemical properties as anode LIB, owned capacity up to 562 mAh g−1 (at 50 mA g−1) with cycling stability and columbic efficiency of 95.87 % and 98.2 %, respectively after 50 cycles. Moreover, AC/V2C_D exhibited the smallest Rct (18.50 Ω), and the discharge capacity of 370.25 mAh g−1 was restored after 60 cycles when the current density returned to 50 mAg−1, implying a good reversibility performance and high endurance for LIB. Furthermore, the fabricated full cell of AC/V2C_D//LiFePO4 exhibits initial discharge and charge capacity at 159.6 and 199.8 mAh g−1, respectively, with 79.9 % of CE and delivers a stable cycling performance with reversible discharge specific capacity of 82.72 mAh g−1 after 100 cycles. These promising results prove that the hybrid of AC/V2C_D MXene can be good potential as an anode material in future LIBs applications.

Ag2Cu(VO3)4/PEDOT:PSS core-shell nanowire for lithium-ion batteries

Recently, multi-component transition-metal vanadium oxides (MTVOs) have shown great potential as a new class of active materials for lithium-ion batteries (LIBs). Compared with simple vanadium oxides, the presence of multi-component transition-metal elements in MTVOs can greatly improve the capacity and cycling stability. Here, we synthesized Ag2Cu(VO3)4 (SCVO) via a simple hydrothermal method. To further improve the specific capacity and electrical conductivity, SCVO/PEDOT:PSS core-shell nanowires were constructed by a dip-coating approach. Electrochemical measurements revealed that SCVO/PEDOT:PSS nanowires exhibit higher initial Coulombic efficiency and better cycling stability as anode material for LIBs.

Comparative study of the (Co/Mn/Ni)xSny intermetallic compounds as anode active materials for lithium-ion batteries

Comparative study of the (Co/Mn/Ni)xSny intermetallic compounds as anode active materials for lithium-ion batteries

Molecular dynamics study on the interfacial properties of mixtures of monomers of polyvinylpyrrolidone (PVP)-based battery binders on graphene and graphite surfaces.

This study investigates the behavior of two different mixtures of monomers of polyvinylpyrrolidone (PVP)-based battery binders, polyvinylpyrrolidone:polyvinylidene difluoride (PVP:PVDF) and polyvinylpyrrolidone:polyacrylic acid (PVP:PAA), at graphene and graphite interfaces using classical molecular dynamics simulations. The aim is to identify the best performing monomer binder blend and carbon-based material for the design of battery-optimized energy devices. The PVP:PAA monomer binder blend and graphite are found to have the best interaction energies, densification upon adsorption, and more ordered structure. The adsorption of both monomer binder blends is strongly guided by the higher affinity of PVP and PAA monomeric molecules for the surfaces compared to PVDF. The structure of adsorbed layers of PVP:PVDF monomer binder blend on graphene and graphite develops more quickly than PVP:PAA, indicating faster kinetics. This study complements a previous density functional theory study recently reported by our group and contributes to a better understanding of the nanoscopic features of relevant interfacial regions involving mixtures of monomers of PVP-based battery binders and different carbon-based materials. The effect of a blend of commonly used monomer binders on carbon-based materials is essential for obtaining tightly bound anode and cathode active materials in lithium-ion batteries, which is crucial for designing battery-optimized energy devices.

Charge Storage Mechanism in Electrospun Spinel-Structured High-Entropy (Mn0.2 Fe0.2 Co0.2 Ni0.2 Zn0.2 )3 O4 Oxide Nanofibers as Anode Material for Li-Ion Batteries.

High-entropy oxides (HEOs) have emerged as promising anode materials for next-generation lithium-ion batteries (LIBs). Among them, spinel HEOs with vacant lattice sites allowing for lithium insertion and diffusion seem particularly attractive. In this work, electrospun oxygen-deficient (Mn,Fe,Co,Ni,Zn) HEO nanofibers are produced under environmentally friendly calcination conditions and evaluated as anode active material in LIBs. A thorough investigation of the material properties and Li+ storage mechanism is carried out by several analytical techniques, including ex situ synchrotron X-ray absorption spectroscopy. The lithiation process is elucidated in terms of lithium insertion, cation migration, and metal-forming conversion reaction. The process is not fully reversible and the reduction of cations to the metallic form is not complete. In particular, iron, cobalt, and nickel, initially present mainly as Fe3+ , Co3+ /Co2+ , and Ni2+ , undergo reduction to Fe0 , Co0 , and Ni0 to different extent (Fe < Co < Ni). Manganese undergoes partial reduction to Mn3+ /Mn2+ and, upon re-oxidation, does not revert to the pristine oxidation state (+4). Zn2+ cations do not electrochemically participate in the conversion reaction, but migrating from tetrahedral to octahedral positions, they facilitate Li-ion transport within lattice channels opened by their migration. Partially reversible crystal phase transitions are observed.

Scalable Synthesis of Porous Silicon by Acid Etching of Atomized Al-Si Alloy Powder for Lithium-Ion Batteries.

Si anodes have attracted considerable attention for their potential application in next-generation lithium-ion batteries because of their high specific capacity (Li15Si4, 3579 mAh g-1) and elemental abundance. However, Si anodes have not yet been practically applied in lithium-ion batteries because the volume change associated with lithiation and delithiation degrades their capacity during cycling. Instead of considering the active material, we focused on the structural design and developed a scalable process for producing Si anodes with excellent cycle characteristics while precisely controlling the morphology. Al-Si alloy powders were prepared by gas atomization, and porous Si with a skeletal structure was prepared by leaching Al using HCl. Porous Si (p-Si12, p-Si19) prepared from Al88Si12 and Al81Si19 comprised resinous eutectic Si, and porous Si (p-Si25) prepared from Al75Si25 comprised lumpy primary Si and resinous eutectic Si. The porosity of the Si anodes varied from 63% to 76%, depending on the Si composition. The p-Si19 anode displayed the finest pore distribution (20-200 nm), excellent rate characteristics, a reversible discharge capacity of 1607 mAh g-1 after 200 cycles at a rate of 0.1 C with a Coulombic efficiency of over 97%, and high stability. The performances of the p-Si25 and p-Si19 electrodes began to decrease after 250 and 850 cycles, respectively, with a constant-charge capacity of 1000 mAh g-1 and at a rate of 0.2 C. In contrast, the p-Si12 anode maintained its discharge capacity at 1000 mAh g-1 for up to 1000 cycles without degradation. Therefore, the developed manufacturing process is expected to produce porous Si as an active material in lithium-ion batteries for high capacity and long life at an industrial scale.

High-Entropy Composite Coating Based on AlCrFeCoNi as an Anode Material for Li-Ion Batteries

In this study, a high entropy composite coating was synthesized by oxidizing a high entropy alloy, AlCrFeCoNi, at elevated temperatures in a pure oxygen atmosphere. X-Ray diffraction (XRD) analysis revealed that the prepared material was a dual-phase composite material consisting of a spinel-structured high entropy oxide and a metallic phase with a face-centered cubic structure. The metallic phase can improve the electrical conductivity of the oxide phase, resulting in improved electrochemical performance. Scanning electron microscopy with energy dispersive spectroscopy (SEM/EDS) analysis unveiled the compositional homogeneity of the composite material. The prepared material was utilized as an anode active material in lithium-ion batteries. Cyclic voltammetry (CV) revealed the oxidation and reduction regions, while the electrochemical impedance spectroscopy (EIS) measurements showed a decrease in the charge transfer resistance during the cycling process. A long-term rate capability test was conducted at various current densities: 100, 200, 500, 1000, and 2000 mA g−1. During this test, a notable phenomenon was observed in the regeneration process, where the capacity approached the initial discharge capacity. Remarkably, a high regeneration efficiency of 98% was achieved compared with the initial discharge capacity. This phenomenon is typically observed in composite nanomaterials. At a medium current density of 500 mA g−1, an incredible discharge capacity of 543 mAh g−1 was obtained after 1000 cycles. Based on the results, the prepared material shows great potential for use as an anode active material in lithium-ion batteries.

Extended Lifespan of Low-Cost Metal Silicon Anodes via a One-Step Wet Ball-Milling Process for Ultra-Thin Polymer Protecting Layer and Optimal Particle Size

Silicon is a promising active material for lithium-ion batteries (LIBs) with a high theoretical capacity (∼4000 mA h g–1). However, there is a critical issue that the fabrication of the Si anode needs complicated and high-cost processes to alleviate the poor cyclic performance, such as nanostructuring. Furthermore, the Si anode requires a high component ratio of conductive agents and binder in the electrode. Herein, we report the fabrication of submicron Si particles coated by a polyacrylonitrile (PAN) layer with a highly polar nitrile group via a facile one-step wet ball-milling process. During the milling of Si particles in PAN solutions, PAN adheres to the Si surface and forms a nanometer coating layer. The nitrile groups of PAN enhance the electrolyte wettability and increase the lithium-ion pathways on the Si surface. These result in a stable solid electrolyte interphase (SEI) layer and reduce the internal resistance of the electrodes. Si anodes with an optimal particle size and PAN layer (SM-Si@PAN) exhibit a superior performance even at ultra-fast current density (50 A g–1). In addition, a full-cell with an NCM712 cathode shows an excellent performance.

Confining NiCo2O4 nanoparticles in nitrogen doped carbon nanotubes embedded in 3D porous graphene aerogels for superior lithium storage

The huge volume expansion and poor electrical conductivity have seriously hindered the further development of redox-based electrode materials such as NiCo2O4 (NCO). Herein, we designed a novel NiCo2O4@nitrogen-doped carbon nanotube@3D graphene (NCO@CT@3DG) aerogel through hydrothermal assembly and high-temperature carbonization. In this aerogel, graphene nanosheets constructed the framework of the aerogel and NCO nanoparticles were deposited on the surface of nitrogen-doped carbon nanotubes which served as active materials for Lithium-ion batteries. The NCO decorated carbon nanotubes connecting the graphene sheets served as the scaffold to support the 3D cross-linked graphene network. As anode material of lithium-ion batteries, the optimized NCO@CT@3DG exhibited excellent electrochemical properties with high capacity as well as superior cycle and rate performance, which could maintain the discharge specific capacity of 810.3 mAh/g at the current density of 1.0 A/g after 500 cycles. The excellent properties are ascribed to the synergistic effect of each individual component and the unique graphene aerogels hybrid structure. This study demonstrates the great application prospects of 3DG aerogel hybrid structure in improving electrochemical properties of active materials with high volume expansion and poor conductivity.