An ultra‐stable sodium half/full battery based on a unique micro‐channel pine‐derived carbon/SnS2@reduced graphene oxide film

Developing super stability, high coulomb efficiency, and long‐span life of sodium‐ion batteries (SIBs) can significantly widen their practical industrial applications. In this study, we report a pine‐derived carbon/SnS2@reduced graphene oxide (PDC/SnS2@rGO) film with fast ion/electron transport micro‐channel used as a SIB anode, which shows ultrahigh stable stability and long‐span life. Functionally, a biomass PDC/SnS2@rGO film with ~30 μm micro carbon channel and ~1.2 μm thick carbon wall can simultaneously provide the fast electron transport path and the Na+ transport channel. Also, the two‐dimensional (2D) layered SnS2 particles attached to the carbon wall of PDC can increase more Na+ contact sites and shorten the Na+ transport path in the NaPF6 electrolyte. To avoid the separation of SnS2 from PDC during the sodiation process, rGO with excellent conductivity and flexibility is wrapped in the SnS2 outer layer as an “electronic garment”. A ~650 mA h g−1 high Na+ storage capacity at 0.1 A g−1 and ~99.8% ultrahigh coulomb efficiency after 800 cycles at 5 A g−1 are obtained when PDC/SnS2@rGO film is used as a SIB anode. Furthermore, a SIB full‐cell is assembled using PDC/SnS2@rGO film (anode) and Na3V2(PO4)3 (cathode), which exhibits a ~163.9 mA h g−1 high reversible capacity and ~99.7% coulomb efficiency performance. Our work provides a reasonable design strategy for the application of biomass‐derived carbon in SIBs, which may inspire more biomass‐derived material studies.


| INTRODUCTION
Achieving low-cost, environmentally friendly, safe and high energy-density storage devices is a major challenge for a sustainable society. 1,2 Commercial lithium-ion batteries (LIBs) have been unable to adapt to the current social needs due to the lack of lithium resources (0.0065% in the crust), high prices, and uneven distribution. 3,4 Sodium-ion batteries (SIBs) with rich sodium resources (2.64% in the crust) and low cost have been considered one of the most potential alternatives for LIBs. 5 Moreover, Na and Li belong to the same main group, which determines that both have similar physical and chemical properties. 6 Many theories of LIBs, such as battery operation mechanism, ion storage mode, and electronic charge transfer mechanism, can be applied to the field of SIBs. 7 Differently, Na + has a~1.02 Å larger radius than Li + (~0.76 Å), leading to sluggish reaction kinetics, large lattice strain and rapidly decreasing storage capacity in the sodium intercalation process. 8,9 Therefore, an important node for promoting industry applications of SIBs is to find a suitable electrode material to solve the above problems. 10 Many efforts have been made to develop suitable SIB anodes. 11 Owing to an 875 mAh g −1 (Na 15 Sn 4 ) theoretical capacity, Tin (Sn)-based materials were considered as SIB suitable anodes, and have been widely investigated. 12 For example, SnS 2 has a two-dimensional (2D) layered CdI2type structure (space group P3m1), which is composed of van der Waals connected S-Sn-S three stacked atomic layers. 13 Besides, SnS 2 has a large interlayer spacing (c = 0.5899 nm), which can be suitable for the insertion/ extraction of Na + , thereby effectively alleviating the volume expansion of host materials. 14,15 However, owing to the poor electronic conductivity and severe pulverization of SnS 2 , SnS 2 anode in SIBs exhibits low Na + storage capacity, short cycle performance, and low coulomb efficiency during the sodiation and desodiation process. 16 Zheng et al. 17 prepared pure SnS 2 nanoparticles as SIB anodes, which showed only 85.6 mAh g −1 reversible capacity and~16.3% capacity retention after 700 cycles. Therefore, the poor conductivity and severe pulverization of pure SnS 2 is an important obstacle for highperformance SIB anodes. 18 As an effective strategy, reducing the size of SnS 2 and adding highly conductive carbon-based materials can significantly enhance the electrochemical behaviors of SIB anodes. 19,20 SnS 2 particles with nano size can provide more Na + contact sites and effectively improve Na + storage efficiency. 21 Moreover, some suitable conductive carbonaceous-based materials, such as carbon nanowires (CNWs), reduced graphene oxide (rGO), carbon fibers (CFs), and biomass-derived carbon (BDC), can simultaneously provide high-speed electron transport channels and disperse SnS 2 nanoparticles. 22,23 Among them, BDC materials have been widely concerned by researchers due to their high conductivity, sustainability, low cost, and special internal carbon structure. 24 Interestingly, BDC materials were designed as carbon matrices for Sn-based materials to disperse nanoparticles and improve the electron transport capacity of the structure. 25,26 In our previously reported, a biomass silk wading-derived carbon fiber film can be used as a carbon matrix for loading Sn-based nanoparticles (<100 nm) as SIB anodes, which showed that the assembled SIB halfcell exhibited~572.2 mA h g −1 high specific capacity at 0.1 A g −1 and more than 1000 cycles span-life. 25 Similarly, a nitrogen/oxygen co-doping peanut shell-derived carbon sheet with Sn nanoparticles (Sn@NOC) was prepared as a SIB anode, exhibiting 123.6 mA h g −1 reversible capacity at 0.1 A g −1 . 27 Owing to different growth mechanisms, BDC with different internal structures and high conductivity can be used as a carbon matrix to composite Sn-based materials to design suitable SIB electrodes. 24,28 Especially, comparing with other biomass materials, pine-derived carbon (PDC) has a distinct microporous structure and strong conductivity, which is more conducive to the design of composite structures. 2 Furthermore, PDC can maintain a complete structure and can be prepared into a self-supporting film directly used as a SIB electrode, while other biomaterials are mostly powders. 2,24,25 However, the low specific Na + storage performance and poor cycle stability at large current density are still unsatisfactory and seriously hinder the practical application of Sn-based materials in SIB anodes. 29 Therefore, it is vital to develop a low-cost, Sn/BDC composite for SIB anodes with high specific capacity and ultrahigh stability at high current density.
Here, a unique pine-derived carbon/SnS 2 @reduced graphene oxide (PDC/SnS 2 @rGO) film was prepared as an ultra-stable SIB anode by the hydrothermal and selfstanding process. In the fabricated film, PDC/SnS 2 @rGO film with microchannels can provide the fast electron transport path and the Na + transport channel, which is conducive to accelerating the reaction kinetics of SIBs. Moreover, ultra-small SnS 2 nanoparticles were attached to the PDC carbon wall to increase more Na + contact sites and shorten the Na + transport path. rGO with excellent conductivity and flexibility is wrapped in the SnS 2 outer layer and can simultaneously adapt to the volume expansion of SnS 2 nanoparticles and form a double electron conductive system with PDC. Consequently, PDC/SnS 2 @rGO film as the SIB half-cell anode possesses a~650 mA h g −1 high Na + storage capacity and 99.8% ultra-stable coulomb efficiency after 800 cycles at high current density, while the SIB full-cell exhibits a ~163.9 mA h g −1 high specific capacity with~99.7% high coulomb efficiency. This work provides a reasonable design strategy for SIB to work under high current density.
2 | EXPERIMENTAL SECTION 2.1 | Preparation of GO and Na 3 V 2 (PO 4 ) 3 A 2.0 mg ml −1 GO aqueous dispersion was purchased from Jiangsu Xianfeng Nano Material Technology Co., Ltd. Na 3 V 2 (PO 4 ) 3 powder was provided by Hangzhou Heshi New Material Technology Co., Ltd.

| Preparation and activation of PDC film
Pinewood was cut into 4 cm * 4 cm * 4 cm cubes, and then calcined at the heating rate of 5°C min −1 to 800°C with Ar 2 (80 ml min −1 flow rate) for 5 h to form PDC cubes. Subsequently, the~10 mm diameter and~0.2 mm thickness of PDC film was obtained by physical cutting and grinding of PDC cubes. We controlled the weight of each PDC film to be almost the same. Furthermore, PDC film was heated to 70°C in 20% (wt) KOH solution for 2 h, and then heated to 60°C in 3 L mol −1 HCl solution for 3 h. We used deionized water and ethanol to wash the PDC film alternately and then dried the cleaned sample in a vacuum drying oven at 120°C for 12 h to prepare activated PDC film.

| Preparation of PDC/SnS 2 @rGO film
First, 1 mmol SnCl 4 ·4H 2 O and 2.5 mmol thiourea (CH 4 N 2 S) were dissolved in 70 ml deionized water and ultrasonicated for 0.5 h. Activated PDC film was put into the dispersion solution to ultrasonic dispersion for 2 h. Second, the above mixture was moved to a 100 ml polytetrafluoroethylene reactor heated at 180°C for 10 h. SnS 2 nanoparticles were attached to the surface of the PDC carbon wall through a hydrothermal process. The films were washed three times with deionized water and ethanol solution respectively, labeled PDC/SnS 2 film after drying at 80°C. Finally, PDC/SnS 2 film and the reducing agent ascorbic acid were put into a 2.0 mg ml −1 GO aqueous dispersion to ultrasonic dispersion for 1 h, and then statically self-standing at 90°C for 3 h (PDC/ SnS 2 @rGO film). The content of PDC, rGO, and SnS 2 in PDC/SnS 2 @rGO film was controlled according to the weight ratio of 3:1:6. It should be noted that SnCl 4 ·4H 2 O, CH 4 N 2 S, and ascorbic acid were provided by Sinopharm Chemical Reagent Co., Ltd.

| Characterization of samples
A D/max2200PC Cu Kα X-ray diffraction (XRD) device was measured to determine the crystal structure and crystallinity of the sample. We employed an AXIS SUPRA X-ray photoelectron spectroscopy (XPS) equipment to analyze the bonding energy and the elemental composition of the sample. A Renishaw inVia plus model of the Raman spectrometer was used to characterize the disorder of carbonaceous materials. Moreover, a transmission electron microscopy (TEM) with the model of Tecnai F20 S-TWIN and a scanning electron microscopy (SEM) with the model of Verios 460 was used to observe the morphologies of PDC, PDC/ SnS 2 , and PDC/SnS 2 @rGO films.

| Coupling and testing process of SIB half-cell and full-cell
PDC, PDC/SnS 2 , and PDC/SnS 2 @rGO films can be directly treated as anodes to couple SIB half-cell and full-cell. Notably, the loading of SnS 2 nanoparticles was regulated between 1.2 and 1.7 mg cm −2 . Owing to PDC and rGO can also provide a part of the sodium storage capacity, the whole PDC/SnS 2 @rGO film was prepared as an active mass to characterize the electrochemical behaviors of SIB half-cell and full-cell. Besides, 1 M NaPF 6 salt was dissolved in Ethylene carbonate (EC) and Dimethyl carbonate (DMC; the volume ratio of EC:DEC is 1:1) to form an electrolyte solution. The CR2032 SIB half-cell and full-cell were assembled in moisture and oxygen values below 0.1 ppm Ar-filled glove box. Notably, sodium metal was carried as the counter electrode of PDC, PDC/SnS 2 , and PDC/SnS 2 @rGO film to couple the SIB half-cell, while a SIB full-cell was assembled by using PDC/SnS 2 @rGO film as anodes and Na 3 V 2 (PO 4 ) 3 as cathodes. Furthermore, we carried out a LAND-CT2011A test system with a suitable potential of 0.01-3.0 V to record the charge and discharge of SIB at 0.05~10 A g −1 .
Electrochemical impedance spectroscopy (EIS) was tested at room temperature by using a CHI618D electrochemical station with three-electrode cells. The EIS was performed with an alternating current (AC) voltage of 5 mV under the frequency range from 100 kHz to 10 mHz. Na 3 V 2 (PO 4 ) 3 power was selected as a cathode to assemble the SIB full-cell and its coating and couple SUN ET AL. process as follows. First, Na 3 V 2 (PO 4 ) 3 , acetylene black, and polyvinylidene fluoride (PVDF) with a mass ratio of 7:2:1 were mixed into N-Methylpyrrolidone (NMP) and then ball milled at low speed (300 rpm/min) for 4 h to form a slurry. We controlled the height of the scraper to ensure the active materials of Na 3 V 2 (PO 4 ) 3 and evenly applied the slurry on Al foil. Subsequently, the Al foil with active materials was dried at 80°C for 24 h in a vacuum drying oven. Finally, a 12 mm diameter disc with the loading of Na 3 V 2 (PO 4 ) 3 between 1.2 and 1.7 mg cm −2 was pressed as a SIB full-cell cathode.

| RESULTS AND DISCUSSION
The preparation process of PDC/SnS 2 @rGO film and its internal structure is shown in Figure 1. As a sustainable, low-cost biomass-derived carbon, the PDC block with a unique microporous carbon channel was prepared by a simple carbonization process. Then, PDC film activated with KOH was further used as a carbon matrix to load SnS 2 nanoparticles by using a hydrothermal method (PDC/SnS 2 film). It is worth noting that SnS 2 nanoparticles tend to agglomerate due to large surface energy. 30 To prevent the separation of SnS 2 nanoparticles from PDC, the flexible rGO was wrapped in the outer layer of the particles by a simple self-standing process (PDC/ SnS 2 @rGO film). The larger microporous carbon channel of PDC contributes to better encapsulation of rGO in the outer layer of SnS 2 nanoparticles. Besides, the internal crystal structures of PDC/SnS 2 and PDC/SnS 2 @rGO film are shown in Figure 1. Clearly, SnS 2 nanoparticles with a CdI2 type 2D layered structure have a large interlayer spacing of 5.8990 Å, which is conducive to the insertion/ extraction of Na + , and in turn, suppresses the volume expansion of PDC/SnS 2 @rGO film.
The optical photos of biomass pine wood before and after carbonization are shown in Figure 2A. Compared with the one before calcination, the internal volume of the PDC block after carbonization is almost halved. Fortunately, the carbonized PDC block with microporous carbon channel well preserves the original internal structure of naturally grown pine trees. To avoid damaging the inside pore structure, the PDC block was cut and polished into films along the parallel direction, which can be used as a carbon matrix for SnS 2 . Figure 2B displays the microporous carbon channel model of PDC. Benefiting from the magic of nature, there are many straight multi-channels in the upward growth direction of the tree, and many tiny holes in the vertical direction. 2,24 As a highly conductive carbon substrate, the PDC can simultaneously provide a high-speed electron transport path and a fast Na + diffusion microporous channel, thereby significantly improving the reaction kinetics of SIBs. Moreover, owing to the growth characteristics of biomass pine trees, many small pores are distributed on the PDC carbon wall, which is conducive to the longitudinal circulation of Na + inside the PDC.
SEM and TEM were used to analyze the structural morphology of PDC/SnS 2 @rGO film in detail. Figure 2C-E shows the SEM morphologies of PDC. Obviously, many carbon pores with a diameter of~30 μm are uniformly arranged in the PDC, and the thickness of the carbon wall is~1.2 μm. The micron-sized pores are conducive to the rapid penetration of NaPF 6 electrolyte, F I G U R E 1 Preparation process and internal structure diagram of PDC/SnS 2 @rGO film. Here, PDC is abbreviated from pine-derived carbon, and rGO is abbreviated from reduced graphene oxide. effectively shortening the transport path between Na + and SnS 2 , thereby improving the coulomb efficiency of SIB. In the vertical direction of PDC ( Figure 2E), many small holes are distributed on the carbon wall, which facilitates the longitudinal flow of electrolytes in the carbon channel and further accelerates the reaction kinetics of SIBs. Figure 2F,J displays the SEM and TEM images of the PDC/SnS 2 @rGO film. As shown in Figure 2F, PDC/SnS 2 @rGO film can still maintain the complete carbon channel structure through hydrothermal and self-standing processes. Besides, many SnS 2 nanoparticles are gathered to form~3 μm particles, which distributes on the PDC carbon wall due to the large surface energy of nanoparticles. Moreover, the flexible, highly conductive rGO can simultaneously avoid the detachment of SnS 2 nanoparticles from the PDC and adapt to the volume expansion of SnS 2 nanoparticles. rGO and PDC together constitute two electron layers inside and outside, thereby significantly enhancing the electron transport ability of PDC/SnS 2 @rGO film. As shown in Figure 2J, the high-resolution (HRTEM) image reveals the lattice spacings of 0.277 nm which relate to the (101) crystal plane of hexagonal SnS 2 . 31 Furthermore, SnS 2 nanoparticles with a diameter of <5 nm were calculated. The ultra-small size SnS 2 nanoparticles are beneficial to alleviate the volume change of SnS 2 during the alloying/dealloying process, which provides a prerequisite for PDC/SnS 2 @rGO film to withstand the shock of large current density. Notably, the electron diffraction pattern of the selected region in Figure 2K was used as proof of the good crystallization of SnS 2 nanoparticles. The distribution of elements in Figure 2L is shown in Figure 2M-O. Clearly, C, S, and Sn elements are uniformly distributed in PDC, indicating that SnS 2 nanoparticles are also uniformly distributed in the carbon channel of PDC/SnS 2 @rGO film.
The crystal structure of PDC/SnS 2 @rGO film was determined by XRD, and the results are shown in Figure 3A. All diffraction peaks of PDC/SnS 2 @rGO film accurately correspond to the SnS 2 standard patterns (PDF #23-0677), showing that SnS 2 nanoparticles have excellent crystallinity. 18,32 The peaks at 28.2°, 32.1°, 41.8°, 49.9°, 52.4°, and 54.9°can be assigned to (100), (101), (102), (110), (111), and (103) planes of SnS 2 . Besides, the XRD analysis results correspond to those of the diffraction pattern in Figure 2K. As shown in Figure 3B, Raman spectroscopy of PDC, PDC/SnS 2 , and PDC/SnS 2 @rGO film was measured to characterize the compositional effects. Clearly, two sharp peaks at 1334 and 1577 cm −1 were assigned to the disordered (D) and graphitic (G) bands of carbonaceous materials, respectively. 33,34 The defect induction and disordered structure of carbonaceous materials are represented by the D peak, while the existence of SP 2 -hybrid graphite carbon structure needs to be reflected by the G peak. 35  X-ray photoelectron spectroscopy (XPS) was used to measure the in-depth element composition and surface chemical state of PDC/SnS 2 @rGO film, and the results are shown in Figure 3C-F. The full XPS spectrum shows obvious peaks of C 1s, S 2p, and Sn 3d, indicating that these three elements are distributed in PDC/SnS 2 @rGO film. Figure 3D shows the Sn 3d spectrum, in which two obvious peaks with 486.3 and 494.7 eV binding energy values are assigned as Sn 3d 5/2 and Sn 3d 3/2 , respectively. 36 The Sn 3d XPS spectrum analysis results are consistent with the Sn 4+ in SnS 2 , and also with the previously reported results. 37,38 The S 2p XPS spectrum of the PDC/SnS 2 @rGO film ( Figure 3E) was peak-fitted to three peaks, which were considered S 2p 3/2 (161.2 eV), S 2p 1/2 (162.9 eV) of Sn-S bonds. 39 Moreover, a 168.2 eV binding energy value peak was clearly observed, which contributed to partially oxidized sulfur species on the surface of the PDC/SnS 2 @rGO film. 39,40 Figure 3F shows the C 1s high-resolution XPS spectrum. A peak located at 284.0 eV was attributed to sp2-hydridized C-C or C=C, while the other two peaks at 285.8 and 288.1 eV are assigned as C-O and O-C=O. 39,41 Figure 3G,H shows the N 2 adsorption and desorption isotherm of PDC/ SnS 2 @rGO film. The microporous structure was demonstrated by observing type-IV isotherm. The specific surface area and pore volume of PDC/SnS 2 @rGO film were further calculated by the Brunauer-Emmett-Teller (BET) method, and the results are shown in Figure 3G,H. A large specific surface area of 33.527 m 2 g −1 and a pore volume of 0.48 cm 3 g −1 were obtained, showing PDC/ SnS 2 @rGO film can provide more Na + active sites for the electrolyte solution.
The electrochemical performance of the SIB half-cell was tested by using PDC/SnS 2 @rGO film as an anode. Figure 4A displays the electrochemical behaviors of PDC, PDC/SnS 2 , and PDC/SnS 2 @rGO film after 60 cycles at 0.1 A g −1 . Obviously, a charge/discharge capacity of 618.5/633.4 mA h g −1 was observed after 60 cycles of PDC/SnS 2 @rGO film, showing excellent Na + storage properties. As a comparison, PDC/SnS 2 and PDC only obtained the charge/discharge specific capacity of 496.9/ 508.1 mA h g −1 and 310.0/312.7 mA h g −1 in the same case. The cycling properties of PDC/SnS 2 film have an obvious downward trend, which is mainly caused by the volume expansion of SnS 2 nanoparticles during the sodiation/desodiation process, thereby making SnS 2 fall off the PDC surface. Moreover, PDC with KOH as an activator also can provide a~310.0/312.7 mA h g −1 Na + storage capacity. As shown in Figure 4B, the coulomb efficiency of PDC/SnS 2 @rGO film was further used to illustrate the cyclic stability of the SIB half-cell. The initial coulomb efficiency of PDC/SnS 2 @rGO film was only 74.9% at 0.1 A g −1 , and gradually stabilized at 98%-103% in the subsequent cycles, showing excellent cycle stability. To illustrate the structural advantage of PDC/SnS 2 @rGO film with a fast Na + /electron transport channel, SIB half-cell was further tested for 100 cycles at a large current density of 1 and 3 A g −1 , respectively ( Figure 4C). Even under the large density impact, PDC/ SnS 2 @rGO film can still maintain the high charge reversible capacity of 327.2 mA h g −1 at 1 A g −1 and 295.7 mA h g −1 at 3 A g −1 after 100 cycles, which illustrates that PDC/SnS 2 @rGO film has a super stable composite structure. Increasing the current density from 1 to 3 A g −1 , the cycle-specific capacity of PDC/SnS 2 @rGO film only decreases by 31.5 mA h g −1 . In the 0.01-3.0 V voltage range, the galvanostatic charge and discharge curves of PDC/SnS 2 @rGO film were measured at 1 A g −1 , as shown in Figure 4D. PDC/ SnS 2 @rGO film displays 97.5% high coulombic efficiency with 393.3 mA h g −1 charge capacity and 403.3 mA h g −1 discharge capacity. In the subsequent cycles, the charge and discharge curves of PDC/SnS 2 @rGO film were highly coincident, illustrating that the reversible specific capacity decreased slowly. Even after 100 cycles, PDC/ SnS 2 @rGO film can still maintain a coulomb efficiency of 97.9%, indicating excellent coulomb efficiency.
Good rate performance was recognized as an important index to measure the electrochemical performance of PDC/SnS 2 @rGO film. 2 As shown in Figure 4E, the rate behavior of PDC/SnS 2 @rGO film was measured at various current densities. The reversible specific capacity of 913.5, 604.9, 442.3, 296.0, and 129.9 mA h g −1 were obtained at 0.05, 0.5, 1.0, 5.0, and 10.0 A g −1 , respectively. When the current intensity returns to 0.05 A g −1 , PDC/ SnS 2 @rGO film still maintains a reversible specific capacity of 708.3 mA h g −1 . Even after a large current intensity impact of 10.0 A g −1 , PDC/SnS 2 @rGO film can still show good structural stability. The specific capacity is only reduced by 205.2 mA h g −1 compared with that under the same density before. Figure 4F shows the Nyquist plots of PDC, PDC/SnS 2 , and PDC/SnS 2 @rGO film. As can be seen, PDC and PDC/SnS 2 have a similar radius of medium and high frequency, which shows that the electron transmission capacity of PDC film is slightly reduced after adding SnS 2 nanoparticles. Compared with PDC and PDC/SnS 2 , PDC/SnS 2 @rGO film has a smaller radius, indicating that the double conductive system with PDC and rGO can effectively enhance the electron transmission capacity. Figure 4G shows the long-cycle performance diagram of PDC/SnS 2 @rGO film at 5.0 A g −1 . A 139.8 mA h g −1 high reversible specific capacity and~99.8% coulomb efficiency can be observed  [42][43][44][45][46][47] after 800 cycles of PDC/SnS 2 @rGO film, which indicate that PDC/SnS 2 @rGO film with fast ion and electron channels can withstand the test of 5.0 A g −1 larger current density. Moreover, we also compared our results with previous studies [42][43][44][45][46][47] related to SnS 2 -based electrodes, as shown in Figure 4H. Obviously, PDC/SnS 2 @rGO film as SIB anode shows more excellent electrochemical performance than the predecessors. [42][43][44][45][46][47] To deeply explore the fast Na + and electron transport principle of PDC/SnS 2 @rGO film, we further analyzed the charge/discharge process. Figure 5A shows the fast electron/Na + transport mechanism of PDC/SnS 2 @rGO film. PDC/SnS 2 @rGO films with micro carbon channels can simultaneously allow a large amount of Na + to enter rapidly and provide abundant active sites, which greatly shortens the transport path of Na + , thereby accelerating the progress of SIB reaction kinetics. Furthermore, the two-layer electronic transmission system composed of PDC and rGO provides a fast electronic highway for PDC/SnS 2 @rGO films. Notably, the flexible rGO can effectively alleviate the internal stress caused by the volume expansion of SnS 2 and avoid the shedding of SnS 2 , which can provide a prerequisite for the impact of high current intensity. Figure 5B illustrates the desolvation process of Na + in the NaPF 6 electrolyte. During the SIB charging process, the action of the external electric field causes Na + in the electrolyte to be carried to the SIB anode side. 48 Na + was used to form a NaF-rich SEI film on the anode side, which causes the loss of some Na + during the first charge and discharge process. 49 Meanwhile, the formation of a stable SEI layer is conducive to the stability of PDC/ SnS 2 @rGO film. 50 The sodiation and desodiation processes of PDC/SnS 2 @rGO films are shown in Figure 5C. In the charging process, the desolvated Na + can quickly contact PDC/SnS 2 @rGO films from multiple directions. Moreover, SnS 2 has a large interlayer spacing (c = 0.5899 nm) that can favor the sodiation and desodiation process. The structure of PDC/SnS 2 @rGO films will be slightly damaged to form PDC/Na x SnS 2 @rGO to store Na + in the sodiumpoor period. With many Na + embedded (sodiumrich), the structure of PDC/Na x SnS 2 @rGO has changed greatly, and the volume expansion phenomenon is more obvious. During the discharging process, Na + will be left from PDC/Na x SnS 2 @rGO to form PDC/SnS 2 @rGO and re-enter the electrolyte solution. Part of the Na + is trapped in PDC/SnS 2 @rGO structures and cannot be released smoothly, which can cause irreversible loss of capacity, thereby leading to the low coulomb efficiency of SIB in the first cycle.
To further clarify the practical value, the SIB fullcell was assembled by using PDC/SnS 2 @rGO film as the anode, Na 3 V 2 (PO 4 ) 3 as the cathode, and NaPF 6 as the electrolyte. The operation model of the SIB F I G U R E 5 (A) Fast electron/Na + convey principle of PDC/SnS 2 @rGO film. (B) The desolvation process of Na + in the NaPF 6 electrolyte. (C) Simulation diagram of PDC/SnS 2 @rGO film during charging and discharging. Here, SEI is abbreviated from solid electrolyte interface.
full-cell is shown in Figure 6A. It should be noted that PDC/SnS 2 @rGO film can be directly used as a selfsupporting anode to assemble a SIB full-cell. Figure 6B,C displays the optical photograph of the SIB full-cell used to light LEDs with the help of the electrode plate. Obviously, SIB full-cell can light five small LEDs for a period of time, demonstrating the potential of PDC/SnS 2 @rGO film for market application. Moreover, the SIB full-cell was tested at 0.1 A g −1 for 300 cycles, and the electrochemical properties were illustrated in Figure 6D. A~163.9 mA h g −1 high reversible specific capacity with~99.7% coulomb efficiency can be observed after 300 cycles of SIB full-cell, indicating that SIB full-cell has ultrastable cycle span-life and ultrahigh reversible specific capacity. Figure 6E displays the charge and discharge curves of SIB full-cell after 20, 100, 200, and 300 cycles respectively. The curves close to each other illustrate that the reversible capacity of SIB full-cell decreases less after multiple charging and discharging, showing excellent cycle stability.

| CONCLUSION
In this study, a sustainable PDC/SnS 2 @rGO film with a fast ion/electron transport microchannel was prepared as an ultra-stable, long-span life SIB anode. The as-designed SIB half-cell shows~650 mA h g −1 high Na + storage capacity and 800 cycles long-span life at 5 A g −1 high current density, while the SIB full-cell exhibits ã 163.9 mA h g −1 high specific capacity and a~99.7% coulomb efficiency performance. After detailed structural and electrochemical characterization, we attribute these excellent properties to the following structural features: (1) biomass PDC/SnS 2 @rGO film with micro carbon channel can provide a fast electron transport path and a Na + transport channel; (2) the sizes of~5 nm 2D layered SnS 2 nanoparticles were attached on the PDC carbon wall can provide more Na + contact sites and shorten the Na + transport path; (3) rGO with excellent conductivity and flexibility is wrapped in the SnS 2 outer layer as an "electronic garment," which can simultaneously enhance the conductivity of PDC/SnS 2 @rGO film and adapt to the volume expansion of SnS 2 nanoparticles, thereby protecting the impact of large current density. This work contributes strategies to the structural design of Sn-based/biomass-derived materials and provides a preparation method for the application of low-cost BDC materials in SIBs.

DATA AVAILABILITY STATEMENT
The data that support the findings of this study are available from the corresponding author upon reasonable request.