Charge-discharge Rate Research Articles

Service life estimation of electric vehicle lithium-ion battery pack using arrhenius mathematical model

Durability is a desired characteristic for all battery packs in Electric Vehicles. In this study, the service life of the EV battery pack under real-world operating conditions is projected using an Arrhenius mathematical simulation model. The model comprises a 39.2 kWh EV Lithium-Ion battery pack integrated with a three-phase inverter to convert the battery pack’s Direct Current output to Alternating Current. In addition, the Alternating Current output is coupled to a 100 kW permanent magnet synchronous motor, which is regarded as the load. A field-oriented controller provides pulse width-modulated output signals that are supplied back to the inverter to generate the correct driving current. Variable conditions of charge rate (C-rate: 1.25C − 4C), discharge rate (C-rate: 0.5C − 4C), temperature (25°C–60°C), and depth of discharge (30%–90%) are evaluated to determine the battery pack’s service life. Under a 4C charge rate/0.5C discharge rate and 50% depth of discharge, the modeling results indicate the battery pack has a service life of approximately 6,000 h at low temperatures (25°C) and roughly 3,000 h at high temperatures (60°C). The model has been validated by comparing the results with experimental data from the literature.

Elucidation of Mass Transport Phenomena in Highly Concentrated Electrolytes during Current Cycling Using In-Situ Interferometry and Finite Difference Method

Understanding electrolyte mass transfer during charge–discharge reactions is essential for developing next-generation storage batteries with high energy densities. In this study, we investigated Li+ transport in a highly concentrated electrolyte (HCE) consisting of an equimolar mixture of lithium bis(fluorosulfonyl)amide (LiFSA) and tetraglyme (G4) under current reversal and re-reversal. Concentration profiles of the electrolyte at a distance of 0–600 μm from the Li electrodes were obtained using in situ laser interferometry. The Li+ transference numbers and LiFSA diffusion coefficients were calculated from these profiles. Raman spectroscopy suggested that the coordination structure surrounding Li+ ions in the electrolytes mainly contributed to the transference number. A one-dimensional unsteady diffusion equation and the finite difference method were employed to simulate the concentration profiles. The maximum error percentage between the measured and simulated values was only 3%, confirming the accuracy and validity of the interferometric measurements. Our findings on Li-ion transfer in HCEs could promote the rational design of high-energy-density Li-ion batteries with higher cation transference numbers of electrolytes and charge–discharge rates.

Synergistic contribution of activated carbon and PEDOT:PSS in hybrid electrodes for high-performance planar micro-supercapacitors

The high-performance miniaturized micro-supercapacitors exhibit great potential due to their inherent properties of high-power density, fast charge–discharge rates, long cycle life, and wide working temperature range. However, there is a need to further enhance the energy density of micro-supercapacitors. In this study, we investigate a hybrid electrode material combination comprising activated carbon (AC) and polymer poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) to fabricate symmetric micro-supercapacitors (SMSCs) and employ the advanced Microplotter technique for the effective loading of active materials onto microelectrodes. The combination of AC and PEDOT:PSS is fine-tuned to attain optimal charge storage. This involves leveraging the synergistic impact of electrical double-layer capacitance from AC and pseudocapacitance from PEDOT:PSS, resulting in enhanced charge storage performance. Additionally, PEDOT:PSS acts as a mixed ion–electron conducting adhesive, effectively binding AC particles together and facilitating the rapid transport of both ions and electrons. As a result, the AC-PEDOT:PSS SMSCs demonstrate an impressive charge storage performance compared to AC SMSCs. At 1 mA/cm2, the measured areal capacitance (device areal capacitances) is 29.5 mF/cm2 (11.8 mF/cm2) for AC-PEDOT:PSS and 15.7 mF/cm2 (6.3 mF/cm2) for AC SMSCs. Furthermore, the areal energies and powers, considering active materials, are found to be 2.79 µWh/cm2 at 0.8 mW/cm2, and considering the device area of the SMSC, they are 1.12 µWh/cm2 at 0.32 mW/cm2. Notably, the AC-PEDOT:PSS SMSCs exhibit a stable long-term capacitance with 85% capacitance retention even after 5000 cycles. This work highlights the significant potential of hybrid materials in improving energy storage performance and showcases the innovative application of the Microplotter technique.

Biomass carbon-reinforced zinc-based composite oxide as an anode for superior sodium storage

The pursuit of high-abundance, cost-effective sodium-ion batteries represents a longstanding and valuable objective in the field. However, significant challenges remain in the quest for breakthroughs, particularly in the discovery of high-performance anode materials and a deeper understanding of the sodium storage mechanism. In this study, we present novel insights into the sodium storage properties of biomass carbon-reinforced Zn2P2O7 (Zn2P2O7/C-c) synthesized via a hydrothermal method followed by annealing, marking the first report of its kind. The unique loose porous structure of the Zn2P2O7/C-c composite offers multiple advantages. It facilitates efficient electrolyte infiltration, enhances the diffusion pathways for sodium ions, expedites electron transfer, and crucially, promotes the retention of Zn2P2O7 on the carbon substrate, even under conditions of mechanical stress or pulverization. Consequently, the Zn2P2O7/C-c composite demonstrates significantly improved rate capability, exhibiting specific capacities of 276.11, 234.41, 195.28, and 149.56 mA h g−1 at current densities of 0.2, 0.5, 1, and 2 A g−1, respectively. Furthermore, it exhibits exceptional cyclic stability with a capacity retention rate of 71% after 1000 charge-discharge cycles at 1 A g−1. In-depth in-situ/ex-situ characterization techniques confirm that the sodium storage mechanism involves a conversion reaction between Zn2P2O7 and Zn, as well as an alloying reaction between Zn and ZnNa13. Kinetic analysis underscores the predominant role of pseudocapacitance in facilitating sodium storage, particularly at high charge-discharge rates. These findings offer valuable insights and inspiration for the exploration of high-performance Zn2P2O7-based anode materials for sodium-ion batteries, representing a significant step toward the realization of cost-effective and efficient sodium-ion battery technology in the future.

On-Chip Micro-Supercapacitor with High Areal Energy Density Based on Dielectrophoretic Assembly of Nanoporous Metal Microwire Electrodes.

Advances in the Internet of Things (IoT) technology have driven the demand for miniaturized electronic devices, prompting research on small-scale energy-storage systems. Micro-supercapacitors (MSCs) stand out in this regard because of their compact size, high power density, high charge-discharge rate, and extended cycle life. However, their limited energy density impedes commercialization. To resolve this issue, a simple and innovative approach is reported herein for fabricating highly efficient on-chip MSCs integrated with nanoporous metal microwires formed by dielectrophoresis (DEP)-driven gold nanoparticle (AuNP) assembly. Placing a water-based AuNP suspension onto interdigitated electrodes and applying an alternating voltage induces in-plane porous microwire formation in the electrode gap. The DEP-induced AuNP assembly and the gold microwire (AuMW) growth rate can be adjusted by controlling the applied alternating voltage and frequency. The microwire-integrated MSC (AuMW-MSC) electrically outperforms its unmodified counterpart and exhibits a 30% larger electrode area, along with 72% and 78% higher specific and areal capacitances, respectively, than a microwire-free MSC. Additionally, AuMW-MSC achieves maximum energy and power densities of 3.33 µWh cm-2 and 2629 µW cm-2, respectively, with a gel electrolyte. These findings can help upgrade MSCs to function as potent energy-storage devices for small electronics.

Flexible Supercapacitor Integrated Systems

AbstractThere is a pressing need for flexible integrated systems owing to the swift progress of flexible electronics. Apart from flexibility, flexible supercapacitor (FSC) integrated systems exhibit certain characteristics like rapid charge–discharge rates, high power density, and excellent cycling stability, which makes them a promising candidate to serve as a vital component in flexible electronics. In this context, an in‐depth overview of recent progress in FSC‐integrated systems, including their design of structure, materials, fabrication techniques, and applications, is offered. On the basis of the current progress, the existing challenges and future prospects are also outlined and discussed.

Synthesis Processes of Carbonaceous Material/Conducting Polymer Nanocomposites in Relation to Grafting and Electrochemical Properties for Supercapacitor Application: A Review

Supercapacitors are the energy storage devices that have gained increased attention due to high charge storage capacity, fast charge-discharge rate, high specific power and excellent cycle stability. Recently, research on supercapacitors is focused on the development of new electrode materials prepared by surface engineering to obtain superior electrochemical performance. Carbonaceous materials (CM) such as graphene, graphene oxide (GO), reduced graphene oxide (rGO) and carbon nanotubes (CNTs) etc. and conducting polymer (CP) based composite materials have gained increased attention for their use in supercapacitors. The nanocomposites obtained by merely mixing these two components pose some serious drawbacks such as low conductivity or poor film forming ability. The conjugation of CPs to CMs through covalent bonds is able to address these drawbacks. This review mainly provide collective information about various synthetic strategies to obtain CP grafted CMs for supercapacitor application. Herein, we provide information on different CP-CM conjugation reactions for obtaining the composites and their effects on electrochemical performances. The analysis revealed the importance of CP-CM grafting is important for tuning the electrochemical properties of the materials.

Influence of Pressure, Temperature and Discharge Rate on the Electrical Performances of a Commercial Pouch Li-Ion Battery

In this study, the performances of a pouch Li-ion battery (LIB) with respect to temperature, pressure and discharge-rate variation are measured. A sensitivity study has been conducted with three temperatures (5 °C, 25 °C, 45 °C), four pressures (0.2 MPa, 0.5 MPa, 0.8 MPa, 1.2 MPa) and three electrical discharge rates (0.5 C, 1.5 C, 3.0 C). Electrochemical processes and overall efficiency are significantly affected by temperature and pressure, influencing capacity and charge–discharge rates. In previous studies, temperature and pressure were not controlled simultaneously due to technological limitations. A novel test bench was developed to investigate these influences by controlling the surface temperature and mechanical pressure on a pouch LIB during electrical charging and discharging. This test rig permits an accurate assessment of mechanical, thermal and electrical parameters, while decoupling thermal and mechanical influences during electrical operation. The results of the study confirm what has been found in the literature: an increase in pressure leads to a decrease in performance, while an increase in temperature leads to an increase in performance. However, the extent to which the pressure impacts performance is determined by the temperature and the applied electrical discharge rate. At 5 °C and 0.5 C, an increase in pressure from 0.2 MPa to 1.2 MPa results in a 5.84% decrease in discharged capacity. At 45 °C the discharge capacity decreases by 2.17%. Regarding the impact of the temperature, at discharge rate of 0.5 C, with an applied pressure of 0.2 MPa, an increase in temperature from 25 °C to 45 °C results in an increase of 4.27% in discharged capacity. The impact on performance varies significantly at different C-rates. Under the same pressure (0.2 MPa) and temperature variation (from 25 °C to 45 °C), increasing the electrical discharge rate to 1.5 C results in a 43.04% increase in discharged capacity. The interplay between temperature, pressure and C-rate has a significant, non-linear impact on performance. This suggests that the characterisation of an LIB would require the active control of both temperature and pressure during electrical operation.

Scalable fabrication of two-dimensional Bi2Se3 for high-performance supercapacitors

Although having an advantageous charge–discharge rate, supercapacitors, in terms of energy density, are still dwarfed by their battery counterparts, thereby hindering their industrial use. Two-dimensional (2D) Bi2Se3, which is characterized by high electrical conductivity, possesses a large theoretical specific capacity that has not been experimentally realized. In this study, we employed scalable electrochemical exfoliation to fabricate high-quality Bi2Se3 nanosheets with a yield of over 95 %. These nanosheets were then applied as anode materials with the hitherto highest specific capacitance of 662.5 F/g at 1A/g to assemble asymmetric supercapacitors (ASCs) of Bi2Se3//NiCo2S4. The supercapacitors demonstrated an extraordinary energy density of 48 Wh/kg at a power density of 800 W/kg and efficiently drove devices such as perovskite-LEDs. This study reveals the huge potential of 2D Bi2Se3 as an efficient supercapacitor electrode via a primary Faradaic pseudocapacitive storage mechanism. The scalable production of this material is expected to stimulate its widespread and practical use.

Carbon quantum dots modified and Y3+ doped Ni3 (NO3 )2 (OH)4 nanospheres with excellent battery-like supercapacitor performance.

Supercapacitor is an important energy storage device widely used in the automobile industry, military production, and communication equipment because of its fast charge-discharge rate, and high power density. Herein, carbon quantum dots modified and Y3+ doped Ni3 (NO3 )2 (OH)4 (NiY@CQDs) nanospheres are prepared by a solvothermal method and used as an electrode material. The electrochemical properties of NiY@CQDs were measured in a three-electrode system. An asymmetric supercapacitor (ASC) cell was assembled with activated carbon (AC) as the anode and NiY@CQDs as the cathode. The electrochemical properties of the ASC device were measured in a two-electrode system. Experimental results show the shape of NiY@CQDs is petal-shaped and the introducing carbon quantum dots and doping Y3+ significantly increases the specific surface area, conductivity, and specific capacitance of Ni3 (NO3 )2 (OH)4 . The mass-specific capacitance of NiY@CQDs reaches up to 2944 F g-1 at a current density of 1 A g-1 . The asymmetric supercapacitor of NiY@CQDs//AC has a high energy density of 138.65 Wh kg-1 at a power density of 1500 W kg-1 , displaying a wide range of application prospects in the energy storage area.

Exploring the Role of Carbon Nanotubes in Mitigating the Effects of Climate Change: A Comprehensive Review

‌This article provides the role of carbon nanotubes (CNTs) in mitigating the effects of climate change. CNTs possess unique properties that make them attractive for various applications aimed at addressing climate-related challenges. This review examines the potential contributions of CNTs in key areas, including energy storage, carbon capture and storage (CCS). In the field of energy storage, CNT-based materials demonstrate high-energy density and fast charge-discharge rates, enabling more efficient energy storage and facilitating the integration of renewable energy sources. This advancement offers promising opportunities for reducing reliance on fossil fuels and promoting a sustainable energy landscape. Regarding CCS, CNTs exhibit exceptional adsorption capabilities, making them effective adsorbents for capturing carbon dioxide (CO2) emissions from industrial sources. Additionally, CNTs can serve as catalyst supports for CO2 conversion, enabling the conversion of CO2 into valuable products and contributing to greenhouse gas reduction efforts. In conclusion, carbon nanotubes hold substantial promise in mitigating climate change. Future research and development efforts should focus on optimizing CNT synthesis techniques, functionalization methods, and characterization approaches to fully harness their potential. By advancing the applications of CNTs, we can contribute to a sustainable and low-carbon future.

Solvent-free NMC electrodes for Li-ion batteries: unravelling the microstructure and formation of the PTFE nano-fibril network

The microstructure and electrochemical performance of solvent-free processed and slurry cast Li(Ni0.6Co0.2Mn0.2)O2 (NMC622) based electrodes for Li-ion batteries has been investigated. In contrast to a moss-like PVDF-based carbon binder domain in slurry cast electrodes, the PTFE binder in solvent-free electrodes had a hierarchical morphology composed of primary fibrils of a few µm in diameter and 100’s µm in length that branched into secondary and then ever finer fibrils, down to diameters of 10s nm or below. A mechanism for the formation of the branch-like morphology observed in PTFE-based solvent-free electrodes is also presented. Even the finest fibrils were confirmed to survive typical cathode cycling conditions. The solvent-free electrodes showed progressive improvement in capacity with increasing charge-discharge rate (up to 150% at 2C) compared with slurry cast equivalents. The capacity of solvent-free electrodes faded 40% slower over 200 cycles at C/3. Impedance analysis showed the solvent-free microstructure enabled reduced charge transfer resistance and ionic resistance, arising from minimal obscuration of the active material surface and no pore blockage.

Microchannel cooling plates with non-uniform airfoil fin arrangement for large-capacity marine battery: An experimental study

In the process of charging and discharging, the heat generation of the battery is uneven, which is more obvious for large-capacity batteries. To maintain the performance of the battery, the thermal management system based on the cooling plate is of critical importance. In this paper, the non-uniform airfoil fins arrangement of microchannel cooling plates for marine large capacity battery thermal management are designed and tested. The cooling performances of the uniform airfoil fins arrangement (UAFA), non-uniform airfoil fins arrangement 1 (N-UAFA 1) and non-uniform airfoil fins arrangement 2 (N-UAFA 2) are experimentally investigated. The maximum temperature (Tmax) and temperature standard deviation (SD) of battery module during charge and discharge process are compared with the variation of the volume flow rate (qv), the cooling water inlet temperature (Tin) and the charge–discharge rate (CR). The experimental results demonstrate that increasing qv and decreasing Tin would contribute to lower Tmax but higher SD. Both Tmax and SD increase with the CR increasing. The cooling effectiveness of the non-uniform airfoil fins arrangement is validated by the reduced Tmax and the robustness in SD control. In particular, the newly designed N-UAFA 2 microchannel could relief the contradiction between cooling capacity and the temperature uniformity. For all the working conditions, the N-UAFA 2 exhibited the best performance. Especially at the CR of 0.5C, the N-UAFA 2 could manage the Tmax and the SD below 36.8 °C and 1.5 °C, respectively.

Hierarchically nanofibers embedded with NiMnS nanocrystals as anode for high-performance lithium-ion batteries: Experimental and theoretical studies

Transition metal sulfides (TMSs) have been appraised as promising anode materials for lithium-ion batteries (LIBs), however, the average conductivity and drastic pulverization produced by specific volume variation during discharge–charge cycles limit their practical application. To resolve these critical issues, an in-situ fabrication approach has been utilized to develop binary TMS-embedded carbon nanofibers (CFs) by regulating the loading of metallic (cationic) components. Herein, a series of NiMnS/CFs-n composites was prepared by controlling Ni/Mn feeding ratios (n) via successive electrospinning, carbonization and sulfidation method. The inventive engineering procedure provides excellent durability (∼99 % compared to 2nd cycle) up to 250 cycles at 1 A g−1 and superb rate performance for NiMnS/CFs-2.0 anode. The final discharge capacities of NiMnS/CFs-2.0 are 730, 608, 562, 468, 370, and 306 mA h g−1 at 0.1, 0.3, 0.5, 1, 3, and 5 A g−1, respectively. Theoretical calculations enable us to understand the role of typical Ni/Mn feeding ratio on electronic properties and confirm that the hybrid NiMnS/CFs-2.0 surface provides enhanced material conductivity, improved Li adsorption energies for S-top sites, and fast discharge–charge rate with low diffusion energy barrier. Meanwhile, the full-cell containing NiMnS/CFs-2.0 anode outperforms the commercialized graphite anode with a high specific energy of ∼529 W h kg−1 and stable durability, which also successfully enlightens a light bulb. The present study will provide a scalable and simple method to fabricate the integrated composite of binary TMS/CFs by proper cationic regulation and offer useful guidelines for commercial applications of TMS-based anode.

Linear ether-based highly concentrated electrolytes for Li-sulfur batteries.

Li-S batteries have attracted attention as next-generation rechargeable batteries owing to their high theoretical capacity and cost-effectiveness. Sparingly solvating electrolytes hold promise because they suppress the dissolution and shuttling of polysulfide intermediates to increase the coulombic efficiency and extend the cycle life. This study investigated the solubility of polysulfide (Li2S8) in a range of liquid electrolytes, including organic electrolytes, highly concentrated electrolytes, and ionic liquids. The Li2S8 solubility was well correlated with the donor number (DNNMR), estimated via23Na-NMR, and was lower than 100 mM_(elemental sulfur) in electrolytes with DNNMR < 14, regardless of the type of electrolyte. Highly concentrated electrolytes comprising lithium bis(trifluoromethanesulfonyl)amide (LiTFSA) and linear chain dialkyl ethers such as methyl propyl ether (MPE), n-butyl methyl ether (BME), and ethyl propyl ether (EPE) were studied as sparingly solvating electrolytes for Li-S batteries. Monomethyl ethers, such as BME, showed more pronounced Li-ion coordination and higher ionic conductivity, whereas the steric hindrance of the longer alkyl chains in EPE lowered the solvation number, enhanced ion association, and lowered the ionic conductivity despite the solvents having similar dielectric constants. The charge-discharge rate capabilities of Li-S cells with dialkyl ether-based electrolytes were more impressive than those of cells with a localized high-concentration electrolyte using sulfolane (SL) and hydrofluoroether (HFE), [Li(SL)2][TFSA]-2HFE. The higher rate performance was attributed to the superior Li-ion transport properties of the dialkyl ether-based electrolytes. A pouch-type cell using lightweight [Li(BME)3][TFSA] demonstrated an energy density exceeding 300 W h kg-1 under lean electrolyte conditions.

Dilute nanocomposites for capacitive energy storage: progress, challenges and prospects.

Electrostatic capacitors (ECs) are critical components in advanced electronics and electric power systems due to their rapid charge-discharge rate and high power density. While polymers are ideal for ECs due to their high voltage tolerance and mechanical flexibility, their low dielectric constants (K) and limited energy density remain significant limitations. Traditional polymer nanocomposites, which incorporate high-K ceramic fillers, have shown promise in enhancing dielectric properties but often at the cost of electric breakdown strength and scalability. In this perspective, we explore a pioneering approach that utilizes ultralow loadings of small-sized inorganic nanofillers to significantly improve dielectric constants without compromising other key properties. We delve into the unconventional effects observed in these polymer nanocomposites, including dielectric enhancements, charge trapping, mechanical reinforcements, and microstructural changes, and highlight the impressive energy storage performance achieved with minimal filler contents. We discuss innovative design strategies from viewpoints of polymer and filler structures and showcase recent advancements in nanoscale characterization and theoretical modelling for understanding the crucial role of polymer-filler interfaces. Finally, we stress fundamental challenges and prospects, providing insights into the transformative potential of these nanocomposites for next-generation energy storage applications.

Insight into the potential of M-NbS2 (M = Pd, Ti and V) monolayers as anode materials for alkali ion (Li/Na/K) batteries.

Doping engineering significantly improves the electrochemical characteristics of electrode materials in alkali ion batteries. Herein, first-principles calculations were performed to systematically explore the effects of metal atom doping in NbS2 monolayers by substituting the Nb atoms with metal M atoms (M = Pd, Ti and V) on the structural stability and electrochemical performances. The results demonstrate that M-NbS2 monolayers can exhibit superior characteristics, including outstanding mechanical flexibility, excellent electronic conductivity, fast charge-discharge rate, low open circuit voltage and high theoretical capacity for alkali ion (Li, Na, and K) storage. Additionally, when alkali ions approach the doping sites of M-NbS2 monolayers, the diffusion energy barriers for Li ions and Na ions can decrease significantly. More importantly, NbS2 monolayers with metal doping can obtain the maximum theoretical capacity of 1470.87 mA h g-1 and the lowest open circuit voltage of 0.17 V. The results of our research can provide a valuable theoretical foundation for the advancement of doped-engineering transition metal chalcogenide monolayers as anode materials in alkali ion battery applications.

From lab to field: Prussian blue frameworks as sustainable cathode materials.

Prussian blue and Prussian blue analogues have attracted increasing attention as versatile framework materials with a wide range of applications in catalysis, energy conversion and storage, and biomedical and environmental fields. In terms of energy storage and conversion, Prussian blue-based materials have emerged as suitable candidates of growing interest for the fabrication of batteries and supercapacitors. Their outstanding electrochemical features such as fast charge-discharge rates, high capacity and prolonged cycling life make them favorable for energy storage application. Furthermore, Prussian blue and its analogues as rechargeable battery anodes can advance significantly by the precise control of their structure, morphology, and composition at the nanoscale. Their tunable structural and electronic properties enable the detection of many types of analytes with high sensitivity and specificity, and thus, they are ideal materials for the development of sensors for environmental detection, disease trend monitoring, and industrial safety. Additionally, Prussian blue-based catalysts display excellent photocatalytic performance for the degradation of pollutants and generation of hydrogen. Specifically, their excellent light capturing and charge separation capabilities make them stand out in photocatalytic processes, providing a sustainable option for environmental remediation and renewable energy production. Besides, Prussian blue coatings have been studied particularly for corrosion protection, forming stable and protective layers on metal surfaces, which extend the lifespan of infrastructural materials in harsh environments. Prussian blue and its analogues are highly valuable materials in healthcare fields such as imaging, drug delivery and theranostics because they are biocompatible and their further functionalization is possible. Overall, this review demonstrates that Prussian blue and related framework materials are versatile and capable of addressing many technical challenges in various fields ranging from power generation to healthcare and environmental management.

Improved energy storage properties of polypropylene-based composite dielectrics by introducing surface-charged BaTiO3@chitisan ultrafine constructions

Surface-charged BaTiO3@chitisan ultrafine constructions can effectively improve the energy storage properties of PP-based composite dielectrics through interfacial-regulation and trap introduction.

Green synthesis of polyimide by using an ethanol solvothermal method for aqueous zinc batteries.

Polyimides (PIs) are welcomed by battery researchers because of their exceptional heat resistance, structural design versatility, and ion-bearing capabilities. However, most of the reported PIs are synthesized by using toxic and hazardous reagents, such as ethylenediamine, p-phenylenediamine, 1-methyl-2-pyrrolidone (NMP), N,N-dimethylacetamide (DMAc), N,N-dimethylformamide (DMF), etc., which are not conducive to environmentally friendly development. In this paper, we aim at employing green solvents and raw materials to prepare PIs using a facile solvothermal method. The reactants are urea and 1,4,5,8-naphthalene tetracarboxylic acid dianhydride (NTCDA). The solvents include pure water, pure ethanol, or water-ethanol mixed solvent. The volume ratio of ethanol in the mixed solvent is regulated to obtain the optimum synthesis condition. Depending on the proportion of ethanol, the polyimide products are labeled as U-PI-0, U-PI-50, U-PI-100, etc. The polymerization degree and structure of synthesized PIs are characterized by gel permeation chromatography (GPC), X-ray diffraction (XRD), scanning electron microscopy (SEM), etc. The results indicate that U-PIs exhibit diverse morphological features, including small fragmented, strip-like, and sheet-like structures, and have relative molecular weights ranging from 7500 to 83 000. Notably, the sheet-like U-PI-100 possesses the largest specific surface area, reaching up to 4.20 m2 g-1. When employed as an electrode material in aqueous zinc batteries, U-PI-100 demonstrates superior electrochemical performance compared to others. At a charge-discharge rate of 0.05C, the initial charge/discharge capacity of U-PI-100 is measured to be 314.2/443.7 mA h g-1.