Discharge Capacity Of Cell Research Articles

A two-step identification approach for an extended nonlinear double-capacitor model

Equivalent circuits are one of the most used models for Li-ion cells in the automotive area. However, it is a challenge to these models to be able to capture the cell discharge capacity under different loads, while still being accurate on both continuous charge and dynamic tests, fast to compute, and easy to parametrize from non-specialized data. To tackle this challenge, this paper proposes an extension of the nonlinear double capacitor model by increasing its order, parameter dependency with C-rate, and an identification procedure that exploits the pseudo-linear nature of the problem to find the parameter maps. An analogy between the parts of the circuit and the single particle model is also presented to reduce the search space of the identification algorithm and to enhance model interpretability. The performance of the proposed model extension is analyzed and compared to a state-of-the-art model on a challenging LiFePO4 dataset with different characteristics and validated on a realistic drive cycle, obtaining a mean absolute average error of around 20 mV for both training and validation tests.

A novel instrumentation approach for achieving in-situ temperature sensing of a Li-ion cylindrical cell under immersion cooling

Battery thermal management systems are critical for high-performance electric vehicles, where the ability to remove heat and homogenize temperature distributions in single cells and packs are key considerations. Immersion cooling, which immerses the battery in a dielectric fluid, can improve cooling efficiency compared to air cooling. However, stringent instrumentation standards make in-situ monitoring under immersion cooling a difficult challenge. This study proposes a novel cell instrumentation method based on the integrated combination of three O-rings, which for the first time achieves in-situ temperature sensing of batteries under oil-immersed cooling conditions. Reliability of the sealing system and instrumentation methodology is ensured by leakage tests and oil corrosion assessment. Data such as cell impedance and discharge capacity also support the success and reliability of the instrumentation process without affecting the battery performance. Compared with natural air cooling, immersion cooling can reduce the temperature rise during battery operation by >10 °C under high C-rate discharge conditions. However, this is accompanied by an increase in radial temperature gradient. The temperature gradient of the cell with oil immersed reaches a maximum of >7 °C, while the temperature gradient under natural cooling under the same test conditions is only 3 to 4 °C. This leads to intensified temperature inhomogeneity of the cell, which may accelerate the local ageing and degradation. Our instrumentation approach contributes to a deeper understanding of the thermal behaviour of batteries under direct immersion cooling, aiding the development of more advanced cooling strategies and associated battery thermal management models.

Magnetic Force Dilatometry of Silicon-NMC622 Lithium-Ion Coin Cells: The Effects of Binder, Capacity Ratio, and Electrolyte Selection

Operando cell expansion measurements on Si-NMC622 coin cells using a magnetic dilatometer were performed to understand the effects of electrode binder content, electrode formulation, negative-to-positive electrode capacity ratio (N/P ratio), and electrolyte selection on reversible and irreversible cell expansions. Our experiments reveal a complex relationship between cell properties, imparted by the selected cell parameters, and cell expansion. Reversible cell expansions scaled with cell discharge capacity and electrode mechanical properties, while irreversible cell expansions were sensitive to capacity fade, silicon utilization, and electrolyte decomposition mechanisms. Additionally, volumetric cell energy densities were calculated using the measured capacities and irreversible expansions over the life of the cells. We show that judicious selection of cell parameters can improve volumetric energy density after 200 charge/discharge cycles by approximately two-fold. Our work provides valuable insight, at an early stage of cell development, towards minimizing the effects of cell expansion on battery cell, pack, and module designs.

Locally Concentrated Deep Eutectic Liquids Electrolytes for Low-Polarization Aluminum Metal Batteries.

Low-cost and nontoxic deep eutectic liquid electrolytes (DELEs), such as [AlCl3]1.3[Urea] (AU), are promising for rechargeable non-aqueous aluminum metal batteries (AMBs). However, their high viscosity and sluggish ion transport at room temperature lead to high cell polarization and low specific capacity, limiting their practical application. Herein, non-solvating 1,2-difluorobenzene (dFBn) is proposed as a co-solvent of DELEs using AU as model to construct a locally concentrated deep eutectic liquid electrolyte (LC-DELE). dFBn effectively improves the fluidity and ion transport without affecting the ionic dynamics in the electrolyte. Moreover, dFBn also modifies the solid electrolyte interphase growing on the aluminum metal anodes and reduces the interfacial resistance. As a result, the lifespan of Al/Al cells is improved from 210 to 2000h, and the cell polarization is reduced from 0.36 to 0.14V at 1.0mAcm-2. The rate performance of Al-graphite cells is greatly improved with a polarization reduction of 0.15 and 0.74V at 0.1 and 1Ag-1, respectively. The initial discharge capacity of Al-sulfur cells is improved from 94 to 1640mAhg-1. This work provides a feasible solution to the high polarization of AMBs employing DELEs and a new path to high-performance low-cost AMBs.

Influence of Particle Size and Mass Loading of Hard Carbon on Sodium Ion Battery Rate Performance in Industrially Relevant Full Cells

Sodium-ion batteries (SIBs) represent a great opportunity for stationary storage, back-up power supply and light electric vehicle applications. Energy and power requirements for these applications needs to be satisfied. Beside material improvement, electrode microstructure plays a critical role. Herein, the influence of hard carbon (HC) particle size and mass loading on the rate performance have been comprehensively investigated. This work analyses the relative contribution of ionic resistance within the porous electrode (Rion) in SIB full cells employing relevant mass loadings. Rion was obtained by applying electrochemical impedance spectroscopy (EIS) to symmetrical cells and by fitting a transmission line model (TLM) under “blocking” conditions. The relative contribution of Rion arising from HC electrodes was further compared to the charge transfer resistance (RCT) in full cell configuration utilising a three-electrode cell under “non-blocking” conditions. Results illustrate mass loading to be as far more influential on cell rate performance compared to the two particle sizes analyzed. The three-electrode study reveals the contribution of Rion to be greater than that of RCT at high mass loadings and high states of charge for the HC electrode and elucidates that the gravimetric and volumetric discharge capacity of cells is limited by the layered oxide cathode and HC electrode respectively.

Synchronized dual-modified graphite felt electrodes for all-vanadium redox flow batteries with high power density and ultra-long lifespan

All-vanadium redox flow battery (VRFB) with high safety and long lifespan is recognized as promising large-scale energy storage system for intermittent renewable energy sources. However, the large-scale development of VRFBs is still hindered by untreated graphite felt electrodes with poor electrocatalytic performance. In this work, we report a modified GF electrode with synchronous etching of the electrode surface and loading of nitrogen-rich biomass carbon, which allows the formation of pores on the GF electrode surface while introducing enriched nitrogen as active sites. The obtained electrode N-EGF exhibits superior wettability, and the structural modification also contributes to the catalytic activity and reversibility of the vanadium redox reaction. The voltage efficiency (VE), energy efficiency (EE) and discharge capacity of the VRFB single cell with N-EGF are improved at current densities from 80 to 280 mA cm−2. Significantly, the power density of the VRFB achieves a peak value of 804.6 mW cm−2. In addition, the N-EGF exhibits excellent stability and ultra-low EE decay rate (0.0018 %) after long-term cycling operation (1285 cycles) at a current density of 200 mA cm−2.

A nitrile solvent structure induced stable solid electrolyte interphase for wide-temperature lithium-ion batteries.

Lithium-ion batteries (LIBs) are extensively employed in various fields. Nonetheless, LIBs utilizing ethylene carbonate (EC)-based electrolytes incur capacity degradation in a wide-temperature range, which is attributable to the slow Li+ transfer kinetics at low temperatures and solvent decomposition during high-rate cycling at high temperatures. Here, we designed a novel electrolyte by substituting nitrile solvents for EC, characterized by low de-solvation energy and high ionic conductivity. The correlation between the carbon chain length of nitrile solvents with reduction stability and the Li+-solvated coordination was investigated. The results revealed that the valeronitrile (VN) solvent displayed an enhanced lowest unoccupied molecular orbital energy level and low de-solvation energy, which helped construct robust SEI interfacial layers and improved kinetics of interfacial ion transfer in wide-temperature LIBs. The VN-based electrolyte employed in graphite‖NCM523 pouch cells achieved a discharge capacity of 89.84% at a 20C rate at room temperature. Meanwhile, the cell exhibited 3C rate cycling stability even at a high temperature of 55 °C. Notably, the VN-based electrolyte exhibited a high ionic conductivity of 1.585 mS cm-1 at -50 °C. The discharge capacity of pouch cells retained 75.52% and 65.12% of their room temperature capacity at -40 °C and -50 °C, respectively. Wide-temperature-range batteries with VN-based electrolytes have the potential to be applied in various extreme environments.

Predicting the discharge capacity of a lithium-ion battery after nail puncture using a Gaussian process regression with incremental capacity analysis

This work uses a Gaussian process regression to predict the discharge capacity of small Lithium-ion pouch cells after a nail puncture. Previous studies have shown that cells can operate at a reduced capacity after experiencing abuse similar to what can be seen during extreme field operation, where the ability to predict cell functionality can be critical to safety. Other studies have shown that different features of cell incremental capacity curves can be used to determine the extent of cell degradation during normal operation, which can be used to predict future operation. For this work, 15 cells are punctured with a nail and allowed to continue operating for 100 total cycles to collect data. The incremental capacity curves are calculated, then the magnitude and corresponding voltage of the highest peak are determined. A Gaussian process regression is used to predict the discharge capacity during operation after the nail punctures. The results show a mean coefficient of determination of 0.923 with a median value of 0.95, a mean root mean square error of 0.013 and median value of 0.09, and a mean absolute error of 0.011 with a median value of 0.08, indicating the regression can be useful in predicting discharge capacity.

Impact of Multiple Module Collectors on the Cell Current Distribution within the Battery Pack

Lithium-ion batteries are usually connected in series and parallel to form a pack for meeting the voltage and capacity requirements of energy storage systems. However, different pack configurations and battery module collector positions result in different equivalent connected resistances, leading to pack current inhomogeneity, which seriously reduces the lifetime and safety of the pack. Therefore, in order to quantitatively analyze the influence of the connected resistance on the current distribution, this study researched the initial cell current distribution of the parallel module by developing mathematical models of different configurations. Then, this study explored the influence of multiple module collector positions on the current inhomogeneity of the pack under the dynamic current condition. The results show that the inhomogeneity of cell current and discharge capacity in the pack with parallel modules connected in series can be improved by keeping each cell in a parallel module with the same distance to its module collector. Furthermore, the current homogeneity of the edge parallel modules in the pack is seriously affected by the position of the single module collector. Therefore, this study innovatively proposes the symmetrical multiple module collectors of the pack, which can greatly improve the current homogeneity of the edge parallel modules, thereby improving the lifetime and safety of the pack.

Effect of Ambient Temperature and Discharge Current on Thermo-Electrochemical Behaviour of Lithium-Ion Cells Using Surrogate Modelling and Analysis

The thermal behaviour of lithium-ion cells plays a critical role in their overall performance and safety. The cell temperature fluctuates during operation due to varying operating conditions, particularly discharge current and ambient temperature. Thus, a precise thermo-electrochemical characterization is imperative for comprehending the behaviour of these cells under a wide range of operating conditions. Through experimental measurements, this study endeavours to determine the dependence of the thermo-electrochemical response of commercial lithium-ion cells as a function of discharge rates and ambient temperatures. High-fidelity reduced-order models are established using surrogate-based techniques to formulate response surfaces for the relevant output parameters, which enables the estimation of these parameters in cases where experiments were not performed. The study reaffirms that an increase in the discharge current rate results in an increase in the temperature difference between the core and surface of the cell. Also, a low ambient temperature has a relatively higher adverse impact on the battery performance, given the same discharge current. Furthermore, sensitivity analysis reveals that cell temperature, discharge capacity, and average discharge energy are more sensitive to ambient temperature than discharge current. On the other hand, the average discharge power is insensitive to ambient temperature and primarily dependent on the discharge current.

Composite Membrane Containing Titania Nanofibers for Battery Separators Used in Lithium-Ion Batteries

In order to improve the electrochemical performance of lithium-ion batteries, a new kind of composite membrane made using inorganic nanofibers has been developed via electrospinning and the solvent-nonsolvent exchange process. The resultant membranes present free-standing and flexible properties and have a continuous network structure of inorganic nanofibers within polymer coatings. Results show that polymer-coated inorganic nanofiber membranes have better wettability and thermal stability than those of a commercial membrane separator. The presence of inorganic nanofibers in the polymer matrix enhances the electrochemical properties of battery separators. This results in lower interfacial resistance and higher ionic conductivity, leading to the good discharge capacity and cycling performance of battery cells assembled using polymer-coated inorganic nanofiber membranes. This provides a promising solution via which to improve conventional battery separators for the high performance of lithium-ion batteries.

Development of al‐doped MgMn2O4‐based cathode materials for magnesium ion cells

AbstractMagnesium ion battery is an alternative for secondary battery instead of lithium ion battery due to its advantages of low cost, safety and environment friendly. Magnesium (Mg) is safer compared to lithium (Li) where it has high stability in contact of air and prevent the formation of dendrites during electrochemical cycling. The cathode materials of un‐doped MgMn2O4 and Al‐doped MgMn2‐xAlxO4, x = .01, .02, .03 were prepared using self‐propagating combustion method with triethanolamine fuel as a reducing agent. All samples (powder form) were annealed at 700˚C in 6 h based on the thermogravimetric analysis results. The samples were been characterized using X ray diffraction, field emission electron microscopy, energy‐dispersive X‐ray spectroscopy and high‐resolution transmission electron microscopy to study structural and morphological properties of the samples. Electrochemical properties of linear sweep voltammetry, cyclic voltammetry, and charge‐discharge capacity were performed in 1 M Magnesium Trifluoromethanesulfonate (MgTf2) with ratio 1:1 of ethylene carbonate: dimethyl ether electrolyte. The discharge capacity of magnesium ion cells using Al‐doped cathode material showed the improvement of 68% compared to the un‐doped sample.

Temperature-Dependent Discharge of Li-O2 and Na-O2 Batteries

Li-O2 and Na-O2 batteries offer the promise of increased energy densities compared to Li-ion batteries but suffer from poor power and cycle life. Despite considerable research on the oxygen reduction reaction (ORR) in these cells at room temperature, limited work has been performed to understand the influence of temperature on the discharge characteristics. In this Letter, we show that the discharge capacity of Li-O2 cells increases with increasing temperature while the discharge capacity of Na-O2 cells decreases over the same temperature range. We show that the discharge behavior of Na-O2 cells is dominated by increasing superoxide solubility with decreasing temperature. On the other hand, increasing Li+-O2– coupling strength with decreasing temperature promotes the formation of insoluble Li2O2 through either disproportionation or a 2e– reduction mechanism, leading to reduced discharge capacity in Li-O2 cells. Such findings highlight the complex and important effect that temperature has on ORR in Li-O2 and Na-O2 batteries.

In Situ Gas-Phase Polymerization of Polypyrrole-Coated Lithium-Rich Nanotubes for High-Performance Lithium-Ion Batteries

Conductive polymer polypyrrole (PPy)-coated lithium-rich manganese-based Li1.2Mn0.54Ni0.13Co0.13O2 (LMNCO) nanotube cathode materials were synthesized by electrospinning and subsequently subjected to low-temperature vapor-phase polymerization. X-ray diffraction (XRD), scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM) results confirm that the successful coating of the PPy layer (~2 nm) on the surface of LMNCO nanotubes did not destroy their morphologies or structures. Electrochemical tests indicate that the electrochemical performance of PPy-coated LMNCO nanotubes has been significantly enhanced. At a rate of 1 C, the discharge capacity of the PPy-coated LMNCO cell is 200.1 mAh g−1, and the capacity retention is 99% after 120 cycles. This excellent stability is attributed to the inhibition of side reactions and the protective function of the tubular structure due to the PPy coating layer. Additionally, the rate capability is also improved at a high current density due to the higher electronic and ionic conductivity.

Partially fluorinated electrolyte for high-voltage cathode with sulfurized carbon anode from polyacrylonitrile for lithium-ion battery

A new lithium-ion battery is configured by coupling sulfurized carbon anode and high voltage LiNi0.5Mn1.5O4 (LNMO) cathode. The anode is derived from sulfurized polyacrylonitrile (S-C(PAN)). Severe capacity fading usually becomes unavoidable due to the oxidative decomposition of solvents, primarily when a conventional carbonate electrolyte with 1 M lithium hexafluorophosphate (LiPF6) is employed. Fluoroethylene carbonate (FEC), ethyl methyl carbonate (EMC), and 1, 1, 2, 2-Tetrafluoroethyl-2, 2, 3, 3-tetrafluoropropyl ether (TTE) are formulated as the best electrolyte (3:2:5 in vol. ratio) for this new high-voltage lithium-ion battery to mitigate this capacity fading and improve the adaptability of the S-C(PAN) and LNMO. The discharge capacity of full cell made with 1 M lithium hexafluorophosphate (LiPF6) in FEC/EMC/TTE (3:2:5) electrolyte reaches 688 mAh g−1 at a rate of 2 C, while 19 mAh g−1 for the control electrolyte. X-ray photoelectron spectroscopy (XPS) results confirm that the fluorinated electrolyte stabilizes both surfaces of S-C(PAN) and LNMO in the full cell effectively. Compared to the control electrolyte, the developed electrolyte enhances the cyclic stability and rate capability of both half cells (Li//S-C(PAN and Li//LiNi0.5Mn1.5O4) and S-C(PAN)//LiNi0.5Mn1.5O4 full cells.

PVDF-based electrolyte decorated by Li29Zr9Nb3O40 Li-ion conductor and electrochemical performance of related solid-state batteries

Solid-state Li-ion batteries (LIBs) have recently attracted much attention for their high safety and energy density. Polyvinylidene fluoride (PVDF) is as a potential electrolyte for solid-state LIBs due to its high permittivity, wide voltage window and excellent thermal stability. Here, Y3+-doped Li29Zr9Nb3O40 (LZNO) Li-ionic conductor with room temperature conductivity (σ25) of 1.26 × 10−4 S cm−1 is prepared. LZNO decorated PVDF-based composite solid electrolytes (CSEs) are fabricated. The PVDF-based CSE with 10% (mass ratio) of LZNO shows σ25 of 2.34 × 10−4 S cm−1, and has thermal stability with melting temperature up to 332 °C and voltage window of 4.8 V. The assembled Li(Ni0.8Co0.1Mn0.1)O2|CSE|Li cells show initial specific discharge capacity of 216.7 mAh g−1 at 0.1 C, and exhibit high capacity and cycle performance. LiFePO4|CSE|Li cells display initial specific discharge capacity of 137.4 mAh g−1 at 0.5 C and high cycle performance. Addition of LZNO powder in CSEs can inhibit the dehydrofluorination of PVDF during the charge-discharge of cells, alleviate the deterioration of interface resistance, and greatly improve the specific discharge capacity of cells at high rates.

Molecular engineering of dihydroxyanthraquinone-based electrolytes for high-capacity aqueous organic redox flow batteries

Aqueous organic redox flow batteries (AORFBs) are a promising technology for large-scale electricity energy storage to realize efficient utilization of intermittent renewable energy. In particular, organic molecules are a class of metal-free compounds that consist of earth-abundant elements with good synthetic tunability, electrochemical reversibility and reaction rates. However, the short cycle lifetime and low capacity of AORFBs act as stumbling blocks for their practical deployment. To circumvent these issues, here, we report molecular engineered dihydroxyanthraquinone (DHAQ)-based alkaline electrolytes. Via computational studies and operando measurements, we initially demonstrate the presence of a hydrogen bond-mediated degradation mechanism of DHAQ molecules during electrochemical reactions. Afterwards, we apply a molecular engineering strategy based on redox-active polymers to develop capacity-boosting composite electrolytes. Indeed, by coupling a 1,5-DHAQ/poly(anthraquinonyl sulfide)/carbon black anolyte and a [Fe(CN)6]3−/4− alkaline catholyte, we report an AORFB capable of delivering a stable cell discharge capacity of about 573 mAh at 20 mA/cm2 after 1100 h of cycling and an average cell discharge voltage of about 0.89 V at the same current density.

Aqueous Processed Thick-Film Li(Ni0.6Mn0.2Co0.2)O2 Electrodes with 3D Architectures

The development of high areal energy density electrodes with layered metal oxide cathode materials is currently worldwide a main topic in research and industry. Water-based binders were applied in the presented work for the manufacturing of NMC 622 (Li(Ni0.6Mn0.2Co0.2)O2) cathodes in order to achieve environmental friendly and cost-reduced production, replacing the conventional organic PVDF binder and the toxic and volatile NMP solvent. However, the pH value of aqueous processed cathode slurries increases to over 12 due to the reaction between NMC 622 particles and water, which decreases the specific discharge capacity of the cells and on the other side results in the chemical corrosion of the current collector during casting. In order to avoid the damage of the current collector and protect the cathode material, different acids could be applied during mixing process to adjust the slurry pH value. In addition, the energy density at battery level can be increased with increasing electrode film thickness which corresponds to an enhanced areal capacity. However, capacity fading of thick-film electrodes at C-rates above C/2 is mainly due to a limited lithium-ion diffusion kinetics and crack formation in cathode particles. 3D electrode architectures produced by ultrafast laser ablation are proven to improve the capacity retention at high discharge rates and the electrolyte wettability of electrodes as reported in our previous works.In this work, NMC 622 electrodes with a film thickness of 150 µm (5.8 mAh/cm2) were manufactured with aqueous binders TRD 202A and CMC, and were subsequently laser structured. With increasing film thickness from 70 µm to 150 µm, the mass loading of cathodes increased from 17 mg/cm2 to 36 mg/cm2. The slurry pH values were adjusted between 9 - 10 with citric acid (CA), phosphoric acid (PA), and acetic acid (AC). The dried electrodes were characterized using XPS and SEM. The unstructured and structured electrodes with different thicknesses were afterwards assembled versus lithium in coin cells. Rate capability test and cyclic voltammetry (CV) were performed in order to investigate the electrochemical performance of the electrodes. Cells containing 70 µm cathodes with PA and CA+PA showed about 10 mAh/g higher capacity at C/20 to C/5 compared to cells with PA, while at 1C to 3C cells with CA showed the lowest capacities With increasing electrode film thickness, cells with PA and PA+CA retained 5-10 mAh/g more capacity than cells with CA at C/20 to C/5. The cells with PA maintained about 120 mAh/g discharge capacity at C/2, while cells with PA+CA and CA showed about 80 mAh/g and 45 mAh/g, respectively. In comparison to cells with unstructured electrodes, laser structuring increased the discharge capacity of cells with 70 µm electrodes from 1C to 3C, regardless of the type of added acid. As for cells with thick-film electrodes, the discharge capacity of cells containing structured electrodes with CA+PA increased to 120 mAh/g, which is about 40 mAh/g higher compared to cells with unstructured electrodes. Finally, CV proved that the addition of acids had no effect on the redox reaction of NMC 622.

Structure–Performance Relationships of Li-Ion Battery Fiber-Based Separators

Lithium-ion battery separators are receiving increased consideration from the scientific community. Many research efforts trend toward creating high-performance fiber-based battery separators with a small and uniform pore size to maximize ionic conductivity and cell discharge capacity. Here, we show that not only the pore size but also the pore size distribution has an important effect on these electrochemical properties. In this work, we studied nonwoven membranes fabricated from a single polymer, poly(vinylidene fluoride) (PVDF), with different pore sizes and pore size distributions using three different techniques (meltblowing, electrospinning, and shear spinning). We evaluate their performance as separators in Li-ion cells. Although meltblowing is commonly employed to produce commercial microfibers/nanofibers, electrospinning has been studied mostly in the academic literature. Shear spinning is an emerging method to fabricate nanofibrous material where, for this study, the morphology of the resulting PVDF membranes may be controlled from fibrous-like to nano-sheet-like with subsequent effects on the electrochemical properties. We show that the smaller the pore size and the wider the pore size distribution, the higher are the electrolyte uptake and ionic conductivity of the mats, resulting in improved in-use discharge capacity and rate capability of Li/LiCoO2 cells.

Ultrathin two-dimensional bimetal NiCo-based MOF nanosheets as ultralight interlayer in lithium-sulfur batteries

Lithium-sulfur batteries as one of the most promising next-generation high-energy storage system, the shuttle effect, the expansion of cathode and the slow electrode redox kinetics limit its further development. Herein, we report a two-dimensional, ultrathin and ultra-light bimetal-NiCo-organic framework as the interlayer for Li-S batteries. This kind of interlayer can effectively block polysulfides and accelerate the conversion with a thickness of only 1 µm and a load of 0.1 mg/cm2. Because the MOF nanosheets with a thickness of a few nanometers have a large specific surface and a large number of exposed accessible active sites. At the same time, the intrinsic activity of each site is enhanced and the catalytic performance is improved due to the synergistic effect of mixed metals and the unique coordination environment around the active sites. So, 2D NiCo MOF/CNT totally meets the requirements for the lightweight and effective interlayer. The initial discharge capacity of cell with 2D NiCo MOF/CNT interlayer can reach 1132.7 mAh/g at 0.5 C. It remained 709.1 mAh/g after 300 cycles, showing good cycling stability and rate performance.