Carbon superstructure nanoflower derived from self-assembly of polyimide for superior lithium storage

Abstract

In this paper, three-dimensional carbon superstructures (CSSs) have been proposed through an effective method. Specifically, the hierarchical self-assembly of polyimide (PI) is followed by thermal annealing. Moreover, the structural evolution of PI under the various pyrolysis time was also comprehensively studied. It is noted that the as-prepared CSSs as anode composites for LIBs, especially CSS-5 h, exhibited extraordinary electrochemical properties, exhibiting a high reversible performance, great rate performance, and excellent cycling stability. As expected, the superior electrochemical capability can be ascribed to the synergistic effect of combining the nanoflower-like carbon superstructures with nitrogen contents. Such a method might encourage the inspirations to devise and obtain various heteroatom-modulated and hierarchical polymer-derived carbon composites for LIBs.

Keywords

itrogen-modulated carbon superstructures polyimide anode materials LIBs

Introduction

With the development of renewable energy and electric devices, the exploitation of low-cost energy-based composites and convenient energy storage apparatus is of great importance to meeting global requirements of energy [1,2]. Because of the merits, in large specific capacity, great cycle life as well as environmentally friendly characteristics, LIBs are commonly and widely applied in electronic devices and EVs [3–7]. Nevertheless, there are weaknesses in LIBs, including the relatively low specific capacity (372 mAh g^–1) and unsatisfactory rate capability, which hinder graphite act as commercial LIBs anode material [8–10]. Hence, it is urgent to devise a brand-new anode to take the place of graphite.

Three-dimensional carbon superstructures (CSSs) assembled from low-dimensional constituents such as carbon nanotubes or graphene sheets, as promising alternatives, have gained increasing interests due to the promoted storage performance together with high-rate capability [11–14]. On the one hand, the thermal treatment of polymers containing aromatic skeletons is a promising strategy for preparing carbon nanosheets, and polymer precursors have the advantages of good thermal stability and high carbon yield. The selection of monomers and the control of polymerization conditions can effectively regulate polymer precursors’ chemical composition, microstructure, and self-assembly behaviour [15–18]. Polymer crystallization is a ‘bottom-up’ self-assembly process that typically contains folding the polymer chain back and forth to form a two-dimensional layered structure that develops into a three-dimensional spherulite [19–25]. Therefore, the formation of lamellar structures and spherulites can be easily regulated by changing the crystallization conditions. The self-assembly of polymers becomes an effective strategy for the construction of finely adjustable polymer superstructures. However, the research on self-assembly mechanisms is still limited [26–30].

On the other hand, numerous investigations in exploring the alternative to anode materials have demonstrated that amorphous carbon materials are promising ones because of their high lithium-ion storage performance and great rate capability, as well as the adjustable morphology [24,31–33]. For instance, Jessl [34] et al. prepared 1D vertically aligned carbon nanotube (CNT) forests coated with metal oxides using microwave-assisted hydrothermal synthesis, which exhibited gravimetric capacity of over 900 mAh g^–1. Wu et al. [35] fabricated nitrogen-modulated flower-like carbon composites, which result in a great reversible performance (1488.1 mAh g^–1@0.05 A g^–1), excellent rate capability (287.6 mAh g^–1@2 A g^–1), as well as satisfactory cycling capacity. Sankar [36] et al. fabricated spherical mesoporous activated carbon through KOH immersion and the hydrochloric acid treatment, which exhibited a discharge and reversible capacity of 781 and 498 mAh g⁻¹ after 100 cycles with a remarkable rate performance. Among these, the three-dimensional carbon superstructures are the attractive electrode composites because it reduce the lithium-ion diffusion distance as well as provide a more extensive electrode/electrolyte interface that is beneficial to the lithium-ion charge transfer [37–40]. At the same time, it could hinder the pulverization and agglomeration of electrode composites and improve the stability of cycling [41,42]. Therefore, the three-dimensional carbon superstructures, leveraging polyimide as the precursor, could be a hopeful alternative for the anode of LIBs [43].

Therefore, we fabricated a three-dimensional carbon superstructure (CSSs) as high-performance anode composites. CSSs owing different morphologies, such as nanoplates, nanoflowers, and nanospheres, were synthesized by changing the polymerization time. Interestingly, when using nanoflowers as the precursor, thanks to the unique morphology, high areas of the surface, adequate distribution of pore size, and high content of nitrogen doping, the as-obtained CSSs-5 h exhibits superior electrochemical performance, such as an extraordinary reversible capacity (534 mAh g⁻¹@0.2 A g⁻¹), wonderful rate capability (636.3 mAh g⁻¹@1 A g⁻¹), as well as satisfactory cycling performance (538.9 mAh g⁻¹ together with 98% retention at 0.2 A g⁻¹ after 200 cycles).

Experiment section

Preparation of PIs and CSSs

PIs were fabricated by a simple hydrothermal approach. Specifically, 0.01 mol p-phenylenediamine (p-PDA) and 0.01 mol 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BTDA) were dissolved in 50 mL NMP. After that, the mixture was stirred for 24 h at room temperature. The precursor Polyamide acid (PAA) was transferred into a Teflon-lined stainless steel autoclave. Then it would undergo hydrothermal treatment at 180°C for 1, 5, and 8 h, which were labelled as PI-1 h, PI-5 h, PI-8 h, respectively. When cooling down to room temperature, PIs were first purified with NMP to remove the unreacted PAA, and then rinsed with deionized water and ethanol to remove the solvent, and dried under vacuum at 60°C for several hours. At last, PIs were pyrolysed at 550°C for 3 h with a heating rate of 5°C min⁻¹ under the N₂ atmosphere to get the product CSSs. The synthesized CSSs were dubbed CSS-1 h, CSS-5 h, and CSS-8 h, respectively.

Characterization of CSSs

The crystal structures of the various CSSs were tested by an X-ray diffractometer (XRD) (D2 Phaser) using Cu-Ka radiation (λ = 1.5406 Å) ranging from 10 to 80. And a field-emission scanning electron microscope (FE-SEM, Hitachi S-8010) is leveraged to study the microstructure at 5.0 kV. And a transmission electron microscope (TEM, JEM-2100F*) is also utilized to characterize the microstructure of CSSs at 120 kV. Further, the X-ray photoelectron spectroscopy (XPS) measurements were conducted on a Escalab 250Xi (Mg Ka) to confirm the element states. All of the binding energies were calibrated by the C 1s peak at 284.6 eV. Raman spectra were collected with an InVia Reflex confocal microscope Raman spectrometer. Moreover, the surface area was analysed via N₂ sorption tests by utilizing an Autosorb IQ Gas Sorption instrument at 77 K. The thermal stability were determined by Thermogravimetric Analyzer (TGA) utilizing a TG 209 F1 Iris.

Electrochemical measurements of CSSs

To prepare the working electrode, the conducting Super-P, polyvinylidene fluoride (PVDF) was mixed in N-methylpyrrolidone (NMP), and our prepared active material at a weight ratio of 7:2:1 to make a uniform slurry. Following that, the mixture was homogeneously coated on copper foil, and the copper foil was dried in a vacuum at 70°C for 12 h. After that, coin cells were assembled in a glove box (<0.1 ppm, H₂O and O₂) filled with Ar, where lithium was utilized as the counter electrode, Celgard 2400 membrane as the separator and 1 M LiPF₆/EC + DEC (1: 1 in volume) as the electrolyte. On the battery test system (Land-CT2001A), the galvanostatic discharge/charging process of the battery is carried out at room temperature in the voltage range of 0.01–3.0 V. Electrochemical impedance spectroscopy (EIS) was performed in the fixed frequency range of 100 kHz∼0.01 Hz. In addition, cyclic voltammetry (CV) tests were carried out for the same potential window. CV and EIS studies were conducted at the Electrochemical Workstation (CHI600E, China).

Results and discussion

Figure 1 vividly depicted the synthesis procedure of carbon superstructures (CSSs). At first, PAA was prepared by the pre-polymerization of BTDA and p-PDA. Then, due to the PAA polymer chain folded back and forth spontaneously, it was easy to form two-dimensional layered nanosheet structures through a solvothermal polymerization process. According to the different solvent thermal durations for 1, 5 and 8 h, the morphologies of PI obtained by self-assembly process evolved from nanoplates to nanoflowers and then to nanospheres. The PIs were then carbonized in an inert N₂ environment, which were denoted as CSS-1 h, CSS-5 h, and CSS-8 h, respectively. The as-prepared PIs are offered with aromatic amides skeletons, which is an idea carbon precursor due to its high thermal stability and rich nitrogen contents, the self-assembled polymer spherulite structures after pyrolysis treatment can be transformed into nitrogen-containing carbon superstructures without any morphological changes [44,45].

Figure 1

Illustration of the synthetic procedure of CSSs. PAA was prepared by the pre-polymerization of BTDA and p-PDA followed by carbonization

The morphologies of PI and CSSs were explored by the field-emission scanning electron microscope (FE-SEM) and transmission electron microscope (TEM). The obtained SEM images of PIs (Figure 2(a–c)) at solvothermal temperature of 180°C shows the appearance of different morphologies, the as-prepared PI-1 h showed the shape of nanoplates, while the PI-5 h exhibited the three-dimensional (3D) nanoflower hierarchical superstructures with the diameters about 1–2 µm, which were composed of inter wined nanosheet subunits. With the extension of solvent thermal time, PI-8 h displayed the morphologies of nanospheres due to the over assembly of nanosheets. SEM images of PI (Figure S1 in the Supporting information) revealed that the hierarchical nanostructures are assembled from 2D nanosheets with average thickness, and the nanostructures particle size is average. Similarly, the CSSs reveal hierarchical nanostructures (Figure 2(d–f)), whose microstructure as same as the corresponding PI after carbonization thanks to the thermal stability of the PI. It could be demonstrated that CSSs material shows integral 3D nanoplates, nanoflowers, and nanospheres comprised of carbon nanosheets with ultra-thin characteristics from the high magnification TEM (HRTEM) image (Figure 2(g–i)). Moreover, the nanosheets that make up CSS-1 h are relatively thick;the shape of the central dense part of CSS-5 h is similar to the overall shape of CSS-1 h, and the sparse edge part shows that the nanosheet forming CSS-5 h becomes thinner; and CSS-8 h is a completely great dense nanosphere.

Figure 2

FESEM restults of (a, d) CSS-1 h; (b, e) CSS-5 h; (c, f) CSS-8 h; TEM images of (g) CSS-1 h, (h) CSS-5 h and (i) CSS-8 h.

In order to explore the structures of the PI and CSSs, X-ray diffractometer (XRD) tests were performed. XRD pattern of PI-5 h presence of six Bragg peaks were at 10°, 15°, 19°, 22°, 26° and 27° (Figure 3(a)), which can be attributed to (002), (004), (110), (200), (006) and (008) planes, respectively, this indicates good crystallinity of PI. However, the CSSs only show two very broad and gentle Bragg diffraction peaks at 26° and 44°, which can be attributed to (002) and (101) planes of carbon. Note that the broad (002) diffraction peak is attributable to the disordered carbon backbone, originating from the formation of randomly oriented polyimide-derived layered carbons. Diffraction of the (101) peak can be homogeneous to the superposition of the (100) and (101) planes that are also characteristic of the turbine framework [46].

Figure 3

(a) XRD spectra; (b) FTIR spectra of PI-5 h and CSS-1 h, CSS-5 h and CSS-8 h; (c) Raman spectra of CSS-1 h, CSS-5 h and CSS-8 h;(d) TGA of PI-5 h and CSS-5 h.

To detect the chemical constitution of CSSs, Fourier transform infrared spectroscopy (FTIR) was carried out. As we can see in Figure 3(b), there are two absorption peaks located at 1710 cm⁻¹ and 1770 cm⁻¹ in the PI-5 h sample, which could be clearly observed and be ascribed to the C = O stretching vibration. Moreover, the absorption peak at 1370 cm⁻¹ could be regarded as the C–N asymmetric and symmetric stretching vibrations, respectively [19,47], these features are also well retained by CSSs. The Raman spectra of CSS-1 h, CSS-5 h, CSSs-8 h showed nearly same patterns as two humpy peaks (Figure 3(c)), which emerged a D-band related to disorder carbon at 1340 cm⁻¹, while a specific G-band interrelated with graphitic carbon at 1560 cm⁻¹. Further, the existence of D bands and G bands proves the disordered structure as well as degree of graphitization of CSS. The intensity ratio could be calculated between the D-band to the G-band (I_D/I_G) of CSS-1 h (0.87), CSS-5 h (0.88), and CSSs-8 h (0.89), reflecting that there were some defects in carbon composites [17]. The D-band may correspond to lattice defects and disordered structures of carbon atoms in carbon composites. In contrast, the G-band results from the stretching vibrations of carbon atoms in a carbon network of all sp² hybridized carbons in a carbocyclic ring or chain [35,48,49].

In order to gain insight into the evolution process from PI to CSSs, TGA was also performed to observe the change process of physical and thermal properties. PI-5 h and CSS-5 h showed excellent thermal stability under nitrogen atmosphere via the TGA (Figure 3(d)). It is worth noting that PI-5 h has no skeleton degradation at 400°C and is a typical glassy high rigidity polyimide [50]. The main loss of the weight of PI happens in the temperature range of 450–600°C. This process mainly includes main chain breakage, deoxygenation, dehydrogenation, aromatization together with the formation of amorphous carbon, and the remaining residual weight should be the carbon material. CSSs-5 h exhibits better stability than PI, starting pyrolysis at higher residual rates.

Based on the above analysis, the layered PI nanoflower was then grown by winding the nanosheets together through a ‘bottom-up’ self-assembly of the polymer crystals (Figure 4). This process involved folding a one-dimensional polymer chain back and forth to form a two-dimensional layered nanosheet that grew into a three-dimensional spherulite superstructure [45], and with the growth of hydrothermal time, the morphology of PI changes from disc-like to flower-like to spherical, which is a crystal growth process, and this is proved by XRD. Owing to the excellent thermal stability of PI, the CSS after carbonization can retain the structure and morphology of the corresponding PI very well.

Figure 4

Illustration of the evolution process of CSSs.

To analyse elemental compositions of the CSSs, X-ray photoelectron spectroscopy (XPS) was conducted. As we can see in Figure 5(a), it is clearly shown in the XPS spectra that the three peaks at the binding energy of 284, 400, and 531 eV that can be attributed to the C 1s, N 1s, and O 1s, respectively [51]. And three different CSSs all exhibit similar characteristics. Moreover, high-resolution N 1s peaks of CSS-1 h, CSS-5 h, CSSs-8 h are also investigated. It is obvious that the CSS-1 h showed two peaks at 400.8 and 398.8 eV, attributing to the pyrrolic-N and pyridinic-N (Figure 5(b)). Differently, the N 1s peaks of the CSS-5 h could be deconvoluted into three peaks at 398.8, 400.8, and 400.9 eV, corresponding to pyridinic-N, pyrrolic-N and graphitic-N, respectively (Figure 5(c)). Furthermore, the N 1s peaks of the CSS-8 h (Figure 5(d)) could also be deconvoluted into three different peaks [52,53]. In contrast, the types of nitrogen in CSS generated from PI synthesized in different hydrothermal time ranges varied significantly with the assembly structure. Pyridinic-N is predominant for CSS-5 h, while pyrrolic-N is predominant for CSS-8 h (Figure 5(e)). Since pyrrolic-N is derived from the pentagonal ring, demonstrating the pyrolysis of PI-8 h is incomplete. Recent works have proved that pyridinic-N is more conducive for the storage of Li ion [40,54–56]. Herein, the CSS-5 h exhibits superior electrochemical performance to other CSSs.

Figure 5

(a) XPS patterns of the CSSs; High-resolution N 1s XPS spectra for (b) CSS-1 h, (c) CSS-5 h and (d) CSS-8 h; (e) The comparison on the content of three types of N in CSSs; (f) The N₂ absorption of CSSs.

Furthermore, the porous structure and surface areas of CSSs were comprehensively studied by N₂ adsorption–desorption analysis. As a result, the Brunauer–Emmett–Teller (BET) specific surface area of CSS-5 h is 802.04 m²/g, while the BET surface area of CSS-1 h and CSS-8 h are 214.20 and 415.59 m²/g, respectively (Figure 5(f)). The high specific surface area of CSS-5 h may be derived from nanoflower morphologies of the precursor, and it is helpful to the intercalation and extraction of Li ions [36,57]. Furthermore, Barrett–Joyner–Halenda (BJH) pore size distributions of CSSs with vairous morphologies are shown in Figure S4 (in the Supporting information). It can be observed that the pore size distribution of all CSSs materials mainly concentrates between 2 and 5 nm, indicating the existence of obvious mesoporous skeleton. The porous skeleton structure of CSSs provided abundant conductive pathways for electrons and ions, beneficial for improving the electrochemical performance of CSSs. It has been confirmed that the specific surface area, pore volume, pore size distribution, and nitrogen doping content are very important factors affecting the electrochemical performance of carbon composites [19].

Encouraged by the special morphology and composition, the electrochemical capabilities of the set of CSSs were studied via coin-type cells. CSSs showed obvious differences in capacity (Figure 6(a–c)). The discharge/charge curves clearly reveal that there is a voltage plateau in the amorphous carbon composites. The discharging/charging capacity of different CSSs samples increased initially and then decreased. In contrast, the CSS-5 h had the best discharge/charge performance because of the high N content, especially the high pyridine-N content, which was confirmed in XPS. As shown in Figure 6(d–f), the CSS-5 h exhibits better rate capability as well as the reversible performance of 620.9, 510.2, 388, 269.5, 203.9, and 153.3 mAh g⁻¹ at the current densities of 0.2, 0.4, 0.8, 1.6, 3.2, and 6.4 A g⁻¹, respectively. Under the high current density of 12.8 A g⁻¹, the CSS-5 h could keep the capacity at 125.5 mAh g⁻¹. Notably, it is worth noting that after the high rate and 60 cycles, CSS-5 h can still maintain 605.3 mAh g⁻¹ discharge capacity when the current density returns to 0.2 A g⁻¹, with good rate performance. Note that we directly discharge as-prepared batteries in the first cycle, which contains a certain amount of electricity. Therefore, it doesn't have to go through the charging process, leading to relatively low Columbic efficiency in the first cycle. Therefore, it can be concluded that the CSS-5 h manifests better rate capability than other CSSs.

Figure 6

Discharge/charge performance of (a) CSS-1 h, (b) CSS-5 h and (c) CSS-8 h at 0.2 A g⁻¹. Rate performance of (d) CSS-1 h, (e) CSS-5 h and (f) CSS-8 h at different current densities

In order to unveil lithium storage capabilities of CSSs, cyclic voltammograms (CV) performance along with discharge–charge tests were conducted. At first, the two broad peaks (Figure 7(a)) at 0.7–0.3 V and 1.5–1.0 V in the first cathodic scan from the CV curves of CSS-5 h can be ascribed to the decomposition of electrolyte, formation of solid electrolyte interface (SEI) as well as other side-reactions [58]. Second, the peak located at 0.2 V can be attributed to the extraction reaction of lithium from the graphitic layers in the anodic scan. Moreover, the peak at 1.2 V originates from the Li⁺ extraction reaction from the defects in the CSS-5 h. In the following cycles, the SEI has formed and the extraction reaction has not occurred, resulting in no peaks appearing. Note that the CV curves are nearly overlapped in the next cycles, indicating the remarkable reversibility of Li⁺ insertion and extraction [59]. Further, it is found that the CV curves of the CSS-1 h and CSS-8 h (Figure S6a and S6c in the Supporting information) are consistent to the discharge/charge performance of CSS-1 h and CSS-8 h.

Figure 7

(a) CV results of CSSs-5 h under the scan rate of 0.5 mV s⁻¹ (3–0.01 V); (b) Discharge/charge performances of CSS-5 h at different current densities;(c) Electrochemical impedance spectroscopy (EIS) of CSS-1 h, CSS-5 h and CSS-8 h before charging-discharging testing; (d) Cycling performance of CSS-5 h at 1 A g⁻¹.

Subsequently, the charge/discharge results of CSS-5 h at various current densities are shown in Figure 7(b). It is shown that the specific capacity of CSS-5 h decreases with increasing current density, but the electrochemical activity can still be maintained at high magnification. Furthermore, the Nyquist plot (Figure 7(c)) shows that CSSs have a semicircle in the mid-high frequency and a straight line related to the diffusion impedance in both low frequency. The ohmic impedance (Rs) of the test cell can be obtained from the real axis value of the high-frequency intercept point. The semicircle in the middle and high frequencies can be attributed to the electrochemical charge transfer resistance (Rct). The low-frequency line is related to the Warburg resistance associated with the CSSs and the diffusion of lithium ions in the electrolyte. The CSS-5 h electrodes both exhibit an interfacial charge transfer resistance (Rct) less than 300 Ω, which indicates a fast kinetic process compared with CSS-1 h and CSS-8 h. To study the cycling performance of CSS-5, tests were conducted at 0.2 A g⁻¹. It is shown in Figure S6 (Supporting information) that the discharge and charge capacities in the first cycle are 2203 and 924.8 mAh g⁻¹, respectively, demonstrating an initial coulombic efficiency of 42.0%. Note that there are about 58.0% loss in the irreversible capacity, because of the formation of SEI and the inevitable decomposition reaction of electrolyte. During subsequent cycles, Coulombic efficiency reached over 94.08% in the second cycle, and remained above 98% throughout the 200 cycles. When cycling for 200 cycles, the CSS-5 h delivered a remarkable capacity of 538.9 mAh g⁻¹, while CSS-1 h and CSS-8 h delivered lower capacity of 266 and 355 mAh g⁻¹. There results manifests better capacity retention of 98% to the second capacity. As we can see in Figure S5a and Figure S5c (in the Supporting information), the CSS-5 h showed excellent reversible capacities superior to PI-5 h, CSS-1 h, and CSS-8 h, because of the complete pyrolysis as well as the abundant nitrogen content of CSS-5 h. Moreover, when applying a high current density of 1 A g⁻¹ on CSS-5 h, the remarkable reversible specific capacity of 600 mAh g⁻¹ is fulfilled after 1000 cycles (Figure 7(d)), proving the great high-rate cycling stability. The reversible capacity of CSS-5 h is better than CSS-1 h and CSS-8 h with 310 mAh g⁻¹ and 266 mAh g⁻¹ (Figure S5b and Figure S5d in the Supporting information), respectively. Note that the capacities gradually decrease in the first few cycles due to the activation of the electrode material not being completed. After the activation has been completed, the capacities undergo a certain increment. The excellent electrochemical results of CSS-5 h can be ascribed to the unique properties of CSSs. The reasons can be explained as follows: At first, the carbon superstructure nanoflowers consist of nanosheets owning a large surface area that can bring about a large amount of activity for Li+ insertion and exit sites, shortens the Li+ diffusion path, and provides sufficient space for volume expansion during lithiation and sodiumation process, thereby improving electrochemical kinetics and cycle stability. Second, nitrogen-modulated carbon empowers it with great electrical conductivity as well as plenty of surface defects, resulting in enhanced rate performance and reversible capacity. Furthermore, the synergistic effect of carbon superstructure nanoflowers and nitrogen doping leads to great capacity, satisfactory rate performance, and remarkable cycle stability [60].

Conclusions

In conclusion, with the help of the hierarchical self-assembly of PI and following the thermal process, a simple and effective method is present for synthesizing nitrogen-doped carbon composites with carbon superstructure nanoflowers assembled by nanosheets. The main contribution of this paper can be concluded as follow: (1) The CSSs exhibit remarkable electrochemical performance when utilized as anode for LIBs; (2) Moreover, the influence of thermal-imidization time on the structure evolution process of PI and the accompanied lithium storage performance was systematically investigated; (3) With the merits of the synergistic relationship of carbon superstructure nanoflowers and nitrogen doping, satisfactory reversible capacity, significant rate performance, and excellent cycle stability are obtained; (4) This strategy might provide a brand new idea for the design of various hierarchical carbon composites derived from polymers further to improve the lithium storage performance of carbon composites.

Footnotes

Disclosure statement

No potential conflict of interest was reported by the author(s).

References

Armand

, Tarascon

JM.

Building better batteries. Nature. 2008;451:652–657.

Larcher

, Tarascon

JM.

Towards greener and more sustainable batteries for electrical energy storage. Nat Chem. 2015;7:19–29.

, Maier

, Yu

Guidelines and trends for next-generation rechargeable lithium and lithium-ion batteries. Chem Soc Rev. 2020;49:1569–1614.

Nitta

, Wu

, Lee

, . Li-ion battery materials: present and future. Mater Today. 2015;18:252–264.

, Yushin

Conversion cathodes for rechargeable lithium and lithium-ion batteries. Energ Environ Sci. 2017;10:435–459.

Dunn

, Kamath

, Tarascon

JM.

Electrical energy storage for the grid: a battery of choices. Science. 2011;334:928–935.

Nitta

, Yushin

High-capacity anode materials for lithium-ion batteries: choice of elements and structures for active particles. Part Part Syst Char. 2014;31:317–336.

Cai

, Yan

, Yao

, . The boundary of lithium plating in graphite electrode for safe lithium-ion batteries. Angew Chem Int Edit. 2021;60:13007–13012.

Guo

, Wang

, Fulvio

, . Soft-templated mesoporous carbon-carbon nanotube composites for high performance lithium-ion batteries. Adv Mater. 2011;23:4661–4666.

10.

Ali

, Muhammad

, Qian

, . Recent advances in material design and reactor engineering for electrocatalytic ambient nitrogen fixation. Mater. Chem. Front. 2022;6:843–879.

11.

Zou

, Kitta

, Hong

, . Fabrication of a spherical superstructure of carbon nanorods. Adv Mater. 2019;31:1900440.

12.

, Xiao

, Huang

, . Enhanced potassium-ion storage of the 3D carbon superstructure by manipulating the nitrogen-doped species and morphology. Nano-Micro Lett. 2021;13:1–14.

13.

Hou

, Zou

, Wang

, . MOF-mediated fabrication of a porous 3D superstructure of carbon nanosheets decorated with ultrafine cobalt phosphide nanoparticles for efficient electrocatalysis and zinc-air batteries. Angew Chem Int Edit. 2020;59:21360–21366.

14.

Cao

, Dai

, Tang

, . Spherical superstructure of boron nitride nanosheets derived from boron-containing metal-organic frameworks. J Am Chem Soc. 2020;142:8755–8762.

15.

Choi

, Lee

, Ahn

, . High-conductivity two-dimensional polyaniline nanosheets developed on ice surfaces. Angew Chem Int Edit. 2015;54:10497–10501.

16.

Jeon

, An

, Yoon

, . Synthesis of ultra-thin polypyrrole nanosheets for chemical sensor applications. Polymer. 2011;52:652–657.

17.

Wei

, Peng

, Ji

, . Rational construction and decoration of Li₅Cr₇Ti₆O₂₅@C nanofibers as stable lithium storage materials. J Energy Chem. 2022;71:400–410.

18.

T-F

, Wei

T-T

, Li

, . Efforts on enhancing the Li-ion diffusion coefficient and electronic conductivity of titanate-based anode materials for advanced Li-ion batteries. Energy Storage Mater. 2020;26:165–197.

19.

Peng

, Qi

, Miao

, . Hierarchical polyimide-derived nitrogen self-doped carbon nanoflowers for large operating voltage aqueous supercapacitor. J Energy Storage. 2020;30:101493.

20.

Tyson

, Mirabello

, Calatayud

, . Thermally reduced graphene oxide nanohybrids of chiral functional naphthalenediimides for prostate cancer cells bioimaging. Adv Funct Mater. 2016;26:5641–5657.

21.

Shtukenberg

, Punin

, Gunn

, . Spherulites. Chem Rev. 2012;112:1805–1838.

22.

Granasy

, Pusztai

, Tegze

, . Growth and form of spherulites. Phys Rev E. 2005;72:011605.

23.

Prokofiev

, Assmus

, Removic-Langer

, . Crystal growth and magnetic properties of the copper coordination polymer [Cu(mu-C₂O₄)(4-aminopyridine)(2)(H₂O)(n). Cryst Res Technol. 2007;42:394–399.

24.

Bassett

DC.

Crystal-growth and the properties of polymers. Nato Adv Sci I B-Phy. 1989;210:267–273.

25.

Ali

, Qiao

, Zhang

, . Surface sulfur vacancy engineering of metal sulfides promoted desorption of hydrogen atoms for enhanced electrocatalytic hydrogen evolution. J Phys Chem C. 2021;125:12707–12712.

26.

Zhang

, Marson

, Ge

, . Simultaneous nano- and microscale control of nanofibrous microspheres self-assembled from star-shaped polymers. Adv Mater. 2015;27:3947–3952.

27.

Yoo

, Byun

, Jeong

, . Performance enhancement of electronic and energy devices via block copolymer self-assembly. Adv Mater. 2015;27:3982–3998.

28.

Ikkala

, ten Brinke

Functional materials based on self-assembly of polymeric supramolecules. Science. 2002;295:2407–2409.

29.

Percec

, Ahn

, Ungar

, . Controlling polymer shape through the self-assembly of dendritic side-groups. Nature. 1998;391:161–164.

30.

Ali

, Yan

2 d Materials for inhibiting the shuttle effect in advanced lithium-sulfur batteries. Chemsuschem. 2020;13:1447–1479.

31.

Qie

, Chen

, Wang

, . Nitrogen-doped porous carbon nanofiber webs as anodes for lithium ion batteries with a superhigh capacity and rate capability. Adv Mater. 2012;24:2047–2050.

32.

Horvath

, Gombar

, Varga

, . Crystallization, melting, supermolecular structure and properties of isotactic polypropylene nucleated with dicyclohexyl-terephthalamide. J Therm Anal Calorim. 2017;128:925–935.

33.

Varga

Supermolecular structure of isotactic polypropylene. J Mater Sci. 1992;27:2557–2579.

34.

Jessl

, Copic

, Engelke

, . Hydrothermal coating of patterned carbon nanotube forest for structured lithium-ion battery electrodes. Small. 2019;15:1901201.

35.

, Liu

, Yuan

, . Nitrogen-doped 3D flower-like carbon materials derived from polyimide as high-performance anode materials for lithium-ion batteries. Appl Surf Sci. 2017;425:1082–1088.

36.

Sankar

, Saravanan

, Ahmed

ATA

, . Spherical activated-carbon nanoparticles derived from biomass green tea wastes for anode material of lithium-ion battery. Mater Lett. 2019;240:189–192.

37.

Xiao

, Ma

, Tan

, . Three-dimensional hierarchical ZnCo₂O₄@C₃N₄-B nanoflowers as high-performance anode materials for lithium-ion batteries. Rsc Adv. 2020;10:32609–32615.

38.

Wang

, Zhang

, Wang

, . Unleashing ultra-fast sodium ion storage mechanisms in interface-engineered monolayer MoS₂/C interoverlapped superstructure with robust charge transfer networks. J Mater Chem A. 2020;8:15002–15011.

39.

Zhu

, Shen

, Luo

, . Low temperature carbonization of cellulose nanocrystals for high performance carbon anode of sodium-ion batteries. Nano Energy. 2017;33:37–44.

40.

Ali

, Wang

, Iqbal

, . Electro-Synthesis of organic compounds with heterogeneous catalysis. Adv Sci. 2022;10:2205077.

41.

Wang

, Shi

, Lan

, . Improving cycle stability of SnS anode for sodium-ion batteries by limiting Sn agglomeration. J Power Sources. 2018;377:1–6.

42.

Byles

, Clites

, Cullen

, . Improved electrochemical cycling stability of intercalation battery electrodes via control of material morphology. Ionics. 2019;25:493–502.

43.

Mullen

Graphene as a target for polymer synthesis. Adv Polym Sci. 2013;262:61–92.

44.

Peng

, Qi

, Miao

, . Formation of nitrogen-doped holey carbon nanosheets via self-generated template assisted carbonization of polyimide nanoflowers for supercapacitor. J Power Sources. 2021;482:228993.

45.

Baumgartner

, Bojdys

, Unterlass

MM.

Geomimetics for green polymer synthesis: highly ordered polyimides via hydrothermal techniques. Polym Chem-Uk. 2014;5:3771–3776.

46.

Sun

, Wu

, Wang

, . Favorable lithium deposition behaviors on flexible carbon microtube skeleton enable a high-performance lithium metal anode. J Mater Chem A. 2018;6:19159–19166.

47.

Ahmad

, Wu

, Guo

, . A graphene supported polyimide nanocomposite as a high performance organic cathode material for lithium ion batteries. Rsc Adv. 2016;6:33287–33294.

48.

Zhao

, Zou

, Qiu

, . Rose-like N-doped porous carbon for advanced sodium storage. Electrochim Acta. 2017;240:24–30.

49.

Ling

, Wang

, Zhang

, . Sustainable synthesis and assembly of biomass-derived B/N co-doped carbon nanosheets with ultrahigh aspect ratio for high-performance supercapacitors. Adv Funct Mater. 2016;26:111–119.

50.

, Yi

, Wang

, . Preparation and gas permeation of crown ether-containing co-polyimide with enhanced CO₂ selectivity. J Membr Sci. 2018;551:191–203.

51.

Wei

, Liang

, Parvez

, . Nitrogen-doped carbon nanosheets with size-defined mesopores as highly efficient metal-free catalyst for the oxygen reduction reaction. Angew Chem Int Edit. 2014;53:1570–1574.

52.

Xing

, Zheng

, Li

, . Observation of active sites for oxygen reduction reaction on nitrogen-doped multilayer graphene. ACS Nano. 2014;8:6856–6862.

53.

Lai

, Potts JR , Zhan

, . Exploration of the active center structure of nitrogen-doped graphene-based catalysts for oxygen reduction reaction. Energ Environ Sci. 2012;5:7936–7942.

54.

Zhu

, Yang

, Zhang

, . High-level pyrrolic/pyridinic N-doped carbon nanoflakes from pi-fused polyimide for anodic lithium storage. Chemistryselect. 2017;2:9007–9013.

55.

T-F

, Pan

J-J

, Wei

T-T

, . NiCo₂S₄-based nanocomposites for energy storage in supercapacitors and batteries. Nano Today. 2020;33:100894.

56.

T-F

, Qiu

L-Y

, Mei

, . Porous spherical NiO@NiMoO₄@PPy nanoarchitectures as advanced electrochemical pseudocapacitor materials. Science Bulletin. 2020;65:546–556.

57.

Vinayan

, Nagar

, Raman

, . Synthesis of graphene-multiwalled carbon nanotubes hybrid nanostructure by strengthened electrostatic interaction and its lithium ion battery application. J Mater Chem. 2012;22:9949–9956.

58.

Wang

, Deng

, Qu

, . Ultrahigh-capacity organic anode with high rate capability and long cycle life for lithium-ion batteries. Acs Energy Lett. 2017;2:2140–2148.

59.

Wang

, Yao

, Du

, . Polyimide Schiff base as a high-performance anode material for lithium-ion batteries. J Power Sources. 2021;482:228931.

60.

, Fei

Two-dimensional transition metal-based electrocatalyst and their application in water splitting. Mater Sci Technol. 2022;38:535–555.