Chinese rose-derived nanostructure carbon as new anode material for lithium-ion batteries

Renewable biomass carbon materials are of wide interest for energy storage applications. Using high-temperature pyrolysis, we carbonized Chinese rose for the first time at different temperatures to investigate the performance of lithium-ion batteries (LIBs) of the resulting materials under different temperature conditions. The fluffy folded structure after carbonization exhibits multiple active sites, which helps to improve the electrical conductivity and mitigate the damage to the material structure caused by electrode expansion. The negative electrode made from the 1000 °C carbonized material can provide a high specific capacity of 725 mAh g−1 after 250 cycles at 0.1 A g−1, and maintains a specific capacity of 373 mAh g−1 at a high current density of 1 A g−1, with excellent rate performance. The results show that Chinese rose-derived carbon (CRDC) materials can be naturally green anode materials for next-generation lithium-ion batteries.


Introduction
The sustained deterioration of climate warming is posing a growing threat to human society and the global ecosystem with the booming global economy and ongoing social development [1][2][3].The requirement for clean energy sources like solar, electric, and biomass energy will rise as a result, displace non-sustainable fossil fuels, and become more prevalent.In the field of new energy, lithium-ion batteries (LIBs) grasp a prominent position [4].When compared to other battery technologies (similar to chromium-nickel batteries), LIBs provide multiple advantages including a high energy density, a low self-discharge rate, small size and weight that make them easy to carry, safety, and the absence of a memory effect [5].The explosion of new energy vehicles has given LIBs an extended platform, but it has also raised expectations for their performance and environmental protection [6][7][8].Obtaining a lithium-ion battery anode material that has the benefits of being inexpensive, pollution-free and high energy density is still an extraordinarily challenging challenge [9].
Several studies have been carried out in recent years to investigate acceptable electrode materials, nevertheless, carbon material remain to be the most common selection for battery materials [10,11].Because of their vast variety, inexpensive price, and distinctive three-dimensional internal arrangement, biomass resources make the best antecedents for the creation of carbon material [12].The preparation procedure has a considerable impact on both the physical and chemical characteristics of biomass carbon materials, even though the structure and composition of biomass are exceedingly complicated [13].Therefore, by varying the kinds of raw materials and preparation techniques, researchers are primarily looking for lithium anode materials with outstanding performance.Typically, biomass that has been carefully chosen for its greater carbon content and higher residual carbon rate after carbonization is utilized as the raw material to manufacture biomass carbon [14].As the researchers Yu et al established biomass porous carbon nanospheres from maize stalks, for instance, they were enabled to achieve beneficial electrochemical characteristics (546 mAh g −1 at the end of 100 cycles at 0.2 C) [15].Yan et al reported a bamboo leaf-derived layered porous carbon material as an advanced anode material for LIBs.The synthesised carbon material provided a high discharge capacity of 450 mA h g −1 after 500 cycles at a current density of 0.2 A g −1 [16].Because of their solid structure and large specific surface area, biomass carbon materials are becoming increasingly prevalent [17].Additionally, they are easily obtainable, recyclable, inexpensive, and ecologically benign, giving them an array of development opportunities [18].
The Chinese rose, regarded as the queen of flowers, has a complex structure, high carbon content, and the ability to develop into a high-quality biomass carbon precursor.As a consequence, Chinese rose has been employed in this research as a precursor to carbon materials, and high-temperature pyrolysis was used to produce biomass carbon materials with a determined structural morphology.A large reversible specific capacity and good cycle stability can be attained by using this structure to enhance the material's contact with the electrolyte, use it as the anode material of the LIB, and accelerate the transmission rate of Li + .It can provide a high specific capacity of 725 mAh g −1 after 250 cycles at 0.1 A g −1 .

Experimental procedures
2.1.Synthesis and characterization of CRDC Take a Chinese rose that is currently in bloom, remove the stamens while rendering the petals on, scrub the surface three times with deionized water to eliminate any exterior pollutants, and subsequently dry it at room temperature.For pre-oxidation treatment, the dried petals were broken up and heated to 220 °C in an aluminum tube furnace at a temperature rate of 2 °C min −1 .A heating rate of 5 °C min −1 was employed to insulate them at 800, 900, and 1000 °C for an aggregate of 3 h.The materials were donated and given the designations CRDC-800, CRDC-900, and CRDC-1000, respectively.Making use of ESCALAB_250Xi x-ray diffraction technology, a material's crystal phase has been investigated within an angle that varies from 10°to 80°.It was conceivable to view and examine the surface structure of synthetic materials via a scanning electron microscope (SEM, Hitachi S-4800).Through the usage of Raman spectroscopy, the order degree of the structure of synthetic materials is examined.

Preparation of electrodes and electrochemical characterization of batteries
A mass ratio of 7:2:1 had been selected to match the made-up CRDC-X (800, 900, and 1000), acetylene black, and binder (PVDF).The appropriate amount of NMP solution was added collectively with the measured PVDF, and after 30 min of stirring at room temperature in a magnetic agitator, solution A emerged.For 30 min, grind CRDC and acetylene black in a mortar.Add to solution A after grinding roughly, in turn, stir for 12 h to create an even slurry.Upon spraying the alcohol-cleansed copper foil evenly with the merged paste, it is then set in a vacuum drying oven and dried for 12 h at 60 °C.Finally, the battery electrode sheet punching machine slices the copper foil into electrode sheets with a diameter of 12 mm, and the quality of each electrode sheet is precisely measured for use in constructing the working electrode.

Electrochemical studies
The buckle battery's anode and cathode shells, gasket insulator, and shrapnel are removed, dried for 4 h in a vacuum drying oven to remove surface moisture, and then assembled in the reverse order: cathode shell, shrapnel, gasket insulator, electrolyte, lithium sheet, electrolyte, separator, electrolyte, electrode [19].The batteries were evaluated using constant current charge-discharge and rate trials after standing for 12 h, and cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were tested on the electrochemical workstation [20].The instrument used in the electrochemical performance test process is CHI 760E (Shanghai Chenhua, China).

Results and discussion
The structural morphology and schematic diagram of the CRDC-1000 preparation procedure are shown in figure 1 CRDC material preparation can be divided approximately into three steps: (1) Select the proper rose petals; (2) Wash and dry the petals; (3) Roast the petals to create a fold structure with stripes akin to soup dumplings.The structure was attached to the lithium-ion battery's negative electrode, and an electrochemical workstation was implemented to test the device's functionality.
XRD and Raman spectroscopy (Raman) were implemented to characterize the CRDCS (CRDC-800, CRDC-900, and CRDC-1000) structures which have been annealed at 800, 900, and 1000 °C, respectively.Establishing whether CRDCS are extremely locally organized or disordered at the nanoscale is the intention.As portrayed in figure 2(a), the three samples all show partial graphitization of the material in the manner of massive diffraction peaks at about 24°and weak diffraction peaks close to 44°, which correspond to the (0 0 2) and (1 0 0) planes of graphite, respectively [21].The two peaks' intensities drop as the temperature rises, therefore indicating the layer gap is expanding.The Raman spectra of the CRDC-800, CRDC-900, and CRDC-1000 are depicted in figure 2(b) [22].The D and G peaks, that travel at 1342 cm −1 and 1591 cm −1 , respectively, can be observed in the graphic.Failures in the material lead to the D peak, which becomes more pronounced and harder the more errors there are in the material.As a consequence, the size of the I D /I G can typically be used to estimate the level of material disorder.The figure clearly shows that the D-peak to G-peak ratios for the CRDC-800, CRDC-900, and CRDC-1000 are 0.97, 1.02, and 1.15, respectively.The degree of graphitization dropped and the number of shortcomings in the material grew as the temperature rose, according to the rising trend in I D /I G measurements.Since there are more active sites for the insertion and removal of Li + even if there are many imperfections around, CRDC-1000 presents the most superior electrochemical performance among the three materials.
SEM observations of CRDC-1000's morphology were taken.The SEM envision of the CRDC-1000 at a scale of 10 μm shows up in figure 3(a) [23].The graphic indicates that the material structure has some regularity and that there are several gullies.The contact location between the electrolyte and the active material can be increased by using the gully as a Li + transportation corridor.Figure 3(b), which shows that the structure of Chinese rose petal cells is not destroyed after annealing at 1000 °C, but shrinks into a multi-fold structure similar to Guantang Bao, is obvious when shrunk to just 4 μm.The structure has a significant amount of specific surface area, which may significantly boost the effective contact area between the active substance and the electrolyte [24].It can also provide more active sites for Li + insertion, which is instructive for Li + diffusion and enhanced electrochemical performance.The harm caused by electrode expansion to the material structure can also be effectively reduced by its unique structure, which can stop materials from stacking up to produce a fluffy  structure.The structure of a single soup packet is shown in greater detail in figure 3(c), and it is evident that the structure is completed.An expanded image of the structure of a soup package from various perspectives is apparent in figure 3(d).
Figure 4 shows the comparison of the discharge specific capacity of CRDC-800, 900, and 1000 at a current density of 0.1 A g −1 , respectively [25].The chart is readily apparent that the CRDC-1000's specific capacity is maximum at various cycles, implying that the sample treated at 1000 °C performs best when compared to 800 °C and 900 °C [26].Since the internal active material is gradually activated in its entirety with the number of cycles, the discharge-specific capacity of the CRDC-1000 increases with the number of cycles.The next section will focus on analysing the electrochemical properties of CRDC-1000.
The CRDC-1000's CV curve is displayed in figure 5(a) at 0.1 mV s −1 .A lack of a distinct redox peak in the graph indicates that most of the elements in the rose blossom are pyrolyzed at a temperature of 1000 °C, leaving behind nearly pure carbon [27].The charge-discharge curve for the CRDC-1000 electrode at 0.1 A g −1 current density at 0.01-3 V is shown in figure 5(b) [28].According to the figure, the CRDC-1000 electrode experienced a first discharge of 1327 mAh g −1 and a second discharge that attenuated to 585 mAh g −1 , with a capacity  retention rate of 44.0% and an enormous irreversible capacity.The following may be because the battery's first cycle is when a solid electrolyte interface (SEI) film forms.The carbon substance still contains H and O atoms, and this continued presence of these atoms results in the irreversible trapping of lithium.In an initial cycle of carbon material generated from biomass, this loss is typical.On the other hand, some lithium is incorporated in carbon materials with porous structures that produce passivation products, leading to holes and holes being obstructed and lithium-ion that cannot be released.The performance diagram of the CRDC-1000 for 500 cycles at a constant current density of 1 A g −1 is shown in figure 5(c).It is crucial to recall that the capacity increased gradually throughout the cycle, which may be the result of the electrolyte gradually penetrating the entire electrode material and the full formation of the SEI layer throughout the entire charge-discharge cycle test [29].The negative active material's structure often has a steady composition.The material structure exhibits a high degree of reversibility to the lithium inputting/delithium behavior during charge and discharge, as seen by the Coulombic efficiency, which is almost 100%.The results of the CRDC-1000 electrode's rate performance test between 0.1 and 10 A can be found in figure 5(d).The specific power discharge capacities are 432 mAh g −1 , 356 mAh g −1 , 290 mAh g −1 , 235 mAh g −1 , 187 mAh g −1 , 130 mAh g −1 and 93 mAh g −1 at 0.1 A g −1 , 0.2 A g −1 , 0.5 A g −1 , 1 A g −1 , 2 A g −1 , 5 A g −1 and 10 A g −1 , respectively [30].The capacity can return to 431 mAh g −1 , which is about the same as the original capacity, when the current density dips to 0.1 A g −1 , disclosing the effective multiplier performance of the CRDC-1000 electrode.
CV curves were measured between 0.1 and 1.0 mV s −1 sweep rate and 0.01-3 V voltage, as shown in figure 6(a).According to the power law formula (1), the capacity contribution of the CRDC-1000 electrode can be computed in detail [31].
Where v is the scanning rate and i is the peak current.It goes without mentioning that determining the graph's slope yields the b value.When the b value is 0.5, the ion diffusion process is the electrode's electrochemical behavior, and the electrode material exhibits characteristics of a battery [32].The electrode material displays battery and pseudocapacitance properties when the b value lies within 0.5 and 1.0, corresponding to a mixed mechanism involving ion diffusion and the capacitive process.When the material exhibits the pseudocapacitance worth, the b value can't be larger than or equal to 1 [33].The electrochemical behavior of the CRDC-1000 electrode material is a Faraday process based on ion absorption/desorption, as shown in figure 6(b), and the electrode material demonstrates a very excellent linear relationship, as evidenced by the computed b value of 1.1761.Formula (2) can be used to determine the contribution rate of pseudocapacitance behavior to charge storage [34]: The contribution rate of pseudocapacitance in the 0.1-1.0 mV s -1 sweep speed range is depicted in figure 6(c).As can be seen, the contribution rate is 50.6%,57.9%, 68.5%, 77.6%, 84.2%, and 90.6% at sweep velocities of 0.1 mV s −1 , 0.2 mV s −1 , 0.4 mV s −1 , 0.6 mV s −1 , 0.8 mV s −1 and 1 mV s −1 , respectively [35].The contribution ratio of the pseudocapacitance decreases with the increase in scanning rate, hitting 90.6% when the scanning rate reaches 1 mV s −1 , as shown in figure 6(d).

Conclusions
In summary, we have investigated Chinese rose-derived carbon materials using high-temperature pyrolysis for the first time, it shows excellent lithium performance at 1000 °C.Its unique fluffy folded structure after carbonization not only has high electrical conductivity but also provides an effective channel for lithium-ion diffusion [36].When assembling the electrodes, CRDC electrodes have a high discharge-specific capacity and excellent rate performance [37].This study provides a new idea for the design of biomass carbon materials as electrodes and opens up a new way for the preparation and development of natural green electrode materials.

Figure 2 .
Figure 2. (a) XRD patterns of CRDC at different temperatures, (b) Raman spectra of CRDC at different temperatures.

Figure 5 .
Figure 5. (a) CV diagram of CRDC-1000 at 0.1 A g −1 , (b) Charge and discharge curve of CRDC-1000 at 0.1 A g −1 current density, (c) Cyclic performance and Coulomb efficiency diagram of the CRDC-1000 at 1 A g −1 current density, (d) Rate performance diagram of the CRDC-1000.

Figure 6 .
Figure 6.(a) CV diagram of CRDC-1000 electrode at different scanning rates, (b) Determination of b value, (c) Contribution rate of pseudocapacitance in CRDC-1000 at different scanning rates, (d) Contribution of pseudocapacitance to CRDC-1000 at a scan rate of 1 mV s −1 .