# Low-temperature Highly Graphitized Porous Biomass-based Carbon as an Efficient and Stable Electrode for Lithium-ion Batteries and Supercapacitors

Sruthy S, Alejandro Grimm, Menestreau Paul, Christie Thomas Cherian, Mikael Thyrel, Palanivel Molaiyan, Ulla Lassi, Shaikshavali Petnikota, Glaydson Simões Dos Reis

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To cite this version:

Sruthy S, Alejandro Grimm, Menestreau Paul, Christie Thomas Cherian, Mikael Thyrel, et al. Low-temperature Highly Graphitized Porous Biomass-based Carbon as an Efficient and Stable Electrode for Lithium-ion Batteries and Supercapacitors. Chemical Engineering Journal Advances, 2025, 22, pp.100762. 10.1016/j.ceja.2025.100762. hal-05047322

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# Low-temperature Highly Graphitized Porous Biomass-based Carbon as an Efficient and Stable Electrode for Lithium-ion Batteries and Supercapacitors

Sruthy E S<sup>a,b</sup>, Alejandro Grimm<sup>b,* c</sup>, Menestreau Paul<sup>b,c</sup>, Christie Thomas Cherian<sup>a c</sup>, Mikael Thyrel<sup>b</sup>, Palanivel Molaiyan<sup>d</sup>, Ulla Lassi<sup>d,e</sup>, Shaikshavali Petnikota<sup>b</sup>, Glaydson Simões Dos Reis<sup>f,*</sup>

## ARTICLE INFO

### Keywords:

Logging residue

Koh activation

Porous graphitic carbon

Electrodes/anodes

Lithium-ion batteries

Supercapacitors

## ABSTRACT

Graphite is a widely used fossil material valued for its versatility, thanks to its excellent thermal and electrical conductivity as well as high chemical stability. Producing graphitic carbon from biomass offers a promising alternative to fossil graphite, but the process requires extremely high temperatures—up to 3000 °C—leading to significant energy consumption. In this work, we report a greener and more sustainable low-temperature method (900 °C) for the synthesis of highly graphitized biomass carbon using pure boron as a catalyst and logging residues (LR) as a carbon source. The work focuses on the correlation between the structural transformation of the precursors into graphitic carbon and their corresponding electrochemical characteristics as electrodes for lithium-ion batteries (LIBs) and supercapacitors. The carbons were prepared in two steps, i.e., carbonization at 500 °C with boron, followed by activation with KOH at 900 °C. A control carbon, produced using the same method but without boron, was used for comparison. The physicochemical characterization results demonstrated the successful graphitization of the LR-based carbon. In addition, the carbon materials exhibited highly porous structures with specific surface areas (BET) of 2645 m² g⁻¹ for the boron-treated carbon (BCLR), and 3141 m² g⁻¹ for the control carbon (CLR). The CLR and BCLR electrodes tested in LIBs delivered specific capacities of 386 and 505 mAh g⁻¹ at a 1 C rate at the end of 200 cycles, respectively. CLR and BCLR electrodes were also tested for supercapacitors, delivering specific capacitances of 87 and 144 F g⁻¹ at a current rate of 1 A g⁻¹, respectively. This work opens a gateway for a straightforward and cost-effective synthesis method for scaling up biomass-based carbon electrodes for LIBs and supercapacitors, facilitating sustainable precursors and an industrially viable approach.

## 1. Introduction

Rechargeable lithium-ion batteries (LIBs) are today the leading choice for portable electronic devices and electric vehicles. However, the increasing demand for clean energy makes further research and development of LIBs essential. Similarly, supercapacitors play a key role in energy-related applications, offering exceptional power density, long cycle life, and rapid charging capabilities [1]. Beyond LIBs, supercapacitors are widely used in backup power systems, electric vehicles,

and hybrid electric vehicles [2,3]. Carbon-based materials have been extensively explored as anode materials for lithium-ion batteries and electrode materials in supercapacitors [4,5], attributed to their superior conductivity, cost-effectiveness, diverse structure, and natural abundance [6]. Graphite has been predominant among them owing to its remarkable electrochemical stability, lower lithium intercalation potential, and high conductivity [7,8]. Nevertheless, the critical supply of natural graphite, the need for high-temperature graphitization to synthesize artificial graphite, and the low theoretical capacity of 372 mAh

<footnote><sup>a</sup> School of Electronic Systems and Automation, Digital University Kerala, Thiruvananthapuram, India</footnote>

<footnote><sup>b</sup> Biomass Technology Centre, Department of Forest Biomaterials and Technology, Swedish University of Agricultural Sciences, SE, 90183, Umeå, Sweden</footnote>

<footnote><sup>c</sup> Public Research University Engineering School, IMT Mines Albi, Albi, 81000, France</footnote>

<footnote><sup>d</sup> Research Unit of Sustainable Chemistry, University of Oulu, PO Box 3000, Oulu, FI, 90014, Finland</footnote>

<footnote><sup>e</sup> University of Jyvaskyla, Kokkola University Consortium Chydenius, PO Box 567, Kokkola, FI, 67100, Finland</footnote>

<footnote><sup>f</sup> Laboratory of Industrial Chemistry and Reaction Engineering, Faculty of Science and Engineering, Åbo Akademi University, 20500, Åbo/Turku, Finland</footnote>

<footnote>* Corresponding authors.</footnote>

<footnote>E-mail addresses: Alejandro.Grimm@slu.se (A. Grimm), Glaydson.SimoesdosReis@abo.fi (G.S.D. Reis).</footnote>
<figure><img src="image_4.png" /><figcaption>Fig. 1. a) SEM of CLR at 2 K of magnification, b) SEM of BCLR at 2 K of magnification, c) SEM of CLR at 10 K of magnification, d) SEM of BCLR at 10 K of magnification.</figcaption></figure>

$g^{-1}$ are forcing researchers to explore other promising alternatives [7,9]. In the case of supercapacitors, various carbon materials have been explored to date as electrochemical double-layer capacitor (EDLC) electrodes, including graphene, templated carbon, and carbon nano-tubes [4]. However, the intricate production process is stagnating the development of several such electrode materials. The demand for graphite is high, and the graphite market is expected to reach around ~ USD 21.6 billion by 2027, due to its multifunctional application in photovoltaics, electronics, and energy storage devices such as super-capacitors and batteries [10,11]. Therefore, more sustainable strategies are required to meet the high demand for graphite. Graphite can be sustainably produced from biomass resources; however, the process is energy-intensive, as it is produced at very high temperatures.

In pursuit of a viable solution to these bottlenecks, biomass-derived activated carbons are drawing attention due to their capability of replacing graphite as an anode material in LIBs and different types of carbons used in supercapacitors [12–15]. The intrinsic molecular structures and architectures of biomass precursors are highly sought-after in battery applications as they are favorable for charge transport and storage [16,17]. Therefore, different biomass precursors, such as rice husk [18,19], peanut shells [20], shells of broad bean [21], lignin [22], olive and cherry stones [23], gelatin [24], spent coffee grounds [25], and cotton [26] have been investigated so far for deriving carbonaceous anode materials for LIBs. These biomass-derived carbons were able to impart higher capacity and cycling stability as anode materials to LIBs. Recent works of literature have reported different ranges of specific capacities, depending on the biomass precursors chosen for LIB anodes. Among them, carbon derived from spent coffee grounds

delivered a reversible capacity of 285 mAh $g^{-1}$ at 0.1 A $g^{-1}$ over 100 cycles [25]. A specific capacity of 460.4 mAh $g^{-1}$ has been illustrated in carbon anodes developed from plane tree leaves at a current density of 50 mA $g^{-1}$ in LIBs [27]. Besides, studies have shown that boron-treating electrode samples significantly improve the electrochemical properties, as is evident in the work demonstrated by Kim et al. [28], where they prepared boron-doped carbon from pyrolysis fuel oil which showed a reversible capacity of 301 mAh $g^{-1}$ at a current density of 0.1 C.

Aiming to enhance the graphitization of biomass-based carbon, many catalysts based on Fe, Co, Ni, and Mn have been utilized [29–32]. Non-metal catalysts, such as boron are a sustainable, efficient, and environment-friendly alternative to replace toxic and expensive metals. The use of boron catalysts greatly enhances the graphitization process at relatively low temperatures, thereby improving the electrochemical performance of various electrode materials [33]. It is well known that chemical activation of carbon with KOH as an activation agent helps to develop a highly porous network with high specific surface area that may lead to superior electrochemical properties [34]. The activation process with potassium hydroxide proceeds via complex chemical activation mechanisms that involve the formation of $K_2O_3$, $K_2O$, and metallic K. During pyrolysis at high temperatures, water vapor and gases such as $CO_2$ and CO are generated, which also helps during the process to develop a porous carbon matrix [35]. Herein, the graphitic activated carbon was synthesized from pine tree logging residues using boron as a graphitization catalyst and a facile two-step carbonization process with KOH activation at temperatures of 900 °C, i.e., significantly lower than temperatures employed for producing graphite from biomass-carbon via heat treatments at around 2400 - 3000 °C. The produced graphitized
<figure><img src="image_5.png" /><figcaption>Fig. 2. HRTEM images of CLR (a,b) and BCLR (c,d).</figcaption></figure>

carbon presented an exceptional electrochemical performance. As found in other studies, boron treatment significantly enhanced the formation of crystalline structures (graphite), which leads to better electrochemical performance [36].

To the best of our knowledge, no such approach has been reported in the literature for achieving a high graphitization degree under such a low temperature. The boron-treated highly graphitized carbon from pine logging residue (BCLR) was tested as an anode material in LIBs and electrodes in symmetric supercapacitors. A systematic electrochemical analysis was carried out to demonstrate the effect of boron treatment, the degree of graphitization, and chemical activation on the electrochemical performance of the synthesized material. The BCLR exhibited first charge capacities of 1343 mAh g⁻¹ and 886 mAh g⁻¹ at 0.1 C and 1 C rates, respectively (1 C = 372 mAh g⁻¹). Conversely, activated carbon without boron-treatment delivered 1482 and 834 mAh g⁻¹ at 0.1 C and 1 C rates, respectively. This study establishes a straightforward and cost-effective synthesis method for scaling up carbonaceous electrode materials for LIBs and supercapacitors, facilitated using sustainable precursors and an industrially viable approach.

## 2. Results and discussion

### 2.1. Physicochemical characterization of the CLR and BCLR electrode materials

SEM was used to examine the morphology of the CLR and BCLR carbons to gain insights into the impact of the boron-catalyst treatment

on the materials' morphological aspects. The SEM images of the CLR (Fig. 1a, 1c) and BCLR (Fig. 1b, 1d) show a clear difference: the boron-treated sample (BCLR) exhibits a much rougher morphology compared to the CLR sample, which has a smoother surface with no cracks or holes (Fig. 1a,c). Additionally, BCLR appears to exhibit a more disordered structure with an agglomeration of smaller particles, indicating the successful modification of the carbon sample's morphology after treatment with the boron catalyst.

The physical features of the CLR and BCLR samples were further evaluated in terms of their porosity and surface area characteristics, which are important properties that significantly influence the electrochemical performance of the electrode materials. Results from the N₂ adsorption/desorption isotherms are presented in the Supplementary Materials (Fig. S1). The N₂ isotherms of the CLR sample showed characteristics of type I with a slight hysteresis, meaning a carbon dominated by microporous structures. The BCLR sample showed a more pronounced hysteresis (from 0.45 to 0.99 of partial pressure), characteristic of type IV, meaning that this carbon has a broader pore size distribution, including micropores, and a larger amount of mesopores compared to the CLR [37]. Such difference between both isotherms could be attributed to the introduction of boron as a catalyst which may cause the collapse of small pores (micropores) and the formation of bigger pores (mesopores), that correspond to the N₂ isotherm curve of BCLR. This transformation is probably responsible for the reduction in the specific surface area of BCLR sample as the contribution of the micropores to the specific surface area (SSA) is larger compared to mesopores.

The CLR and BCLR samples exhibited extremely high SSA of 3141
<figure><img src="image_6.png" /><figcaption>Fig. 3. CV curves of a) CLR and b) BCLR at 0.1 mV s⁻¹scan rate, discharge-charge profiles of c) CLR and d) BCLR and corresponding cycling performance of e) CLR and f) BCLR at 1 C current rate.</figcaption></figure>

and 2645 m² g⁻¹, respectively [38]. The synergistic effect of mesopores and micropores leads to a positive impact on the electrochemical performance of the BCLR anode material because more mesopores can provide sufficient space and efficient transport channels for Li⁺, thus enabling a faster transport of Li⁺ [39]. Therefore, more presence of mesopores in BCLR sample could lead to an enhanced the charge transfer and shortened transport path of Li⁺. In addition, bigger pores could also be beneficial for buffering the volume change during the lithiation/delithiation [39].

Raman spectroscopy was employed to evaluate how the boron catalyst affected the carbon structure in terms of the degree of disorder

and graphitization of the BCLR (Supplementary Information Fig. S2a, S2b) [38]. The Raman spectra of the LR-based carbons displayed characteristic signatures related to G and D bands centered at ~ 1340 and 1610 cm⁻¹, respectively. However, a remarkable difference in the Raman spectra is observed in the BCLR spectrum (Fig. S2b), with a sharp G' peak (2D peak) at 2680 cm⁻¹. G' peak strongly indicates the presence of graphene structures with a very high degree of stacking. The G band suggests the presence of graphitic structure in the carbon network, while the D band is indicative of structural defects in the carbon lattice. To further evaluate the graphitization process of the boron-treated sample, I<sub>D</sub>/I<sub>G</sub> was calculated, which indicates graphitization degree. BCLR
<figure><img src="image_7.png" /><figcaption>Fig. 4. Rate capability test of a) CLR and b) BCLR samples under various C-rates.</figcaption></figure>

possesses an $I_D/I_G$ value of nearly 0.45 while CLR presented a value of around 0.81. This clearly suggests that the boron, acting as a catalyst, effectively enhanced the graphitization degree of LR carbon under lower graphitization temperatures.

The crystallinity of the CLR and BCLR samples were further evaluated by XRD patterns (Fig. S2c, S2d, Supplementary Information). The pattern shows two evident diffraction peaks that correspond to the (002) and (100) crystal planes of graphitic carbon. The sharp peaks at 26.3° (002) and 44.9° (100) confirm the crystalline structure of both carbons, which suggests the alignment of graphitic carbon layers to form a crystalline turbostratic structure [40]. The XRD spectra (plotted with the same scale for both samples) show that the BCLR has more intense peaks compared to CLR, which can indicate a more crystallographic and better organized aromatic carbon structure in BCLR. These results are in agreement with the Raman spectroscopic data, highlighting the efficient graphitization process of the LR carbon by using boron as a catalyst.

The microstructure of the CLR and BCLR materials was investigated by HRTEM (Fig. 2). Firstly, the TEM images suggest highly porous structures despite of boron catalyst treatment corroborating the BET data. TEM images undoubtedly show that the boron-treated sample

(Fig. 2c,d) exhibits a high degree of graphitization, since orderly stacked graphene layers are visible in the images. Much less amorphous phases compared to CLR carbon can be seen (Fig. 2a,b), which although some graphitic structures are observed it has a lot more obvious amorphous phase (disordered/random structures). As previously discussed, boron is an efficient catalyst to promote the graphitization process.

Table S1 shows the elementary composition of the CLR and BCLR materials. The results were obtained from XPS analysis [38]. The results from Table S1 show that both CLR and BCLR are composed of carbon and oxygen. BCLR presented more content of graphitic carbon (C—C bonds) than CLR, corroborating what was observed by TEM and Raman analysis. In BCLR sample, boron content was found in traces (0.25%, a.t-%), confirming the fact that the boron acted as catalyst not as a dopant.

## 2.2. Electrochemical performance of the anode materials in LIBs

The electrochemical performance of CLR and BCLR anodes was evaluated through CV tests and the resulting curves are shown in Fig. 3a, 3b. The curves for both samples show typical CV curves for biomass-based carbons [39]. In the first cycle, the broad cathodic peak

<table><caption>**Table 1**

Comparative electrochemical performance of CLR and BCLR anodes with the biomass carbonaceous materials as LIBs anodes.</caption><thead><tr><th>Biomass source</th><th>Synthesis Method and Morphology</th><th>Specific surface area (SBET, m² g<sup>-1</sup>)</th><th>Potential (V vs Li<sup>+</sup>/Li)</th><th>Current rate (C or mA g<sup>-1</sup>)</th><th>Initial capacity (Discharge/Charge) (mAh g<sup>-1</sup>)</th><th>Capacity retention (mAh g<sup>-1</sup>)/ (cycles)</th><th>Ref.</th></tr></thead><tbody><tr><td>Coffee waste grounds</td><td>Non-porous carbonaceous materials by mechanochemical dry milling of spent coffee grounds followed by further carbonization at 800 °C</td><td>&lt; 10</td><td>0.0 – 3.0</td><td>100 mA g<sup>-1</sup></td><td>764/ ~380</td><td>285 ± 5 (100)</td><td>[25]</td></tr><tr><td>Calotropis gigantea wasteland weed</td><td>Activated carbon produced by chemical activation with CaOCl<sub>2</sub> in normal atmospheric conditions</td><td>–</td><td>0.01 – 2.0</td><td>1 C</td><td>446</td><td>137 (100)</td><td>[44]</td></tr><tr><td>Microalgae</td><td>Pyrolysis process in nitrogen flow for 6 h at 900 °C at a heating rate of 10 °C min<sup>-1</sup></td><td>38</td><td>0 – 3.0</td><td>1 C</td><td>370</td><td>355 (500)</td><td>[45]</td></tr><tr><td>Portobello mushroom</td><td>Carbon nanoribbon as free-standing, binder-free, and current collector-free Li-ion battery anodes</td><td>19.6</td><td>0.01 – 3.0</td><td>50 mA g<sup>-1</sup></td><td>771.3/280</td><td>~260 (700)</td><td>[46]</td></tr><tr><td>Commercial Loofah</td><td>Treated with KOH solution (5 M) and pyrolysed at 1000 °C for 2 h.</td><td>270</td><td>0.01 – 3.0</td><td>100 mA g<sup>-1</sup></td><td>250</td><td>225 (400)</td><td>[47]</td></tr><tr><td>Hazelnut shells</td><td>Hydrothermal carbonization plus pyrolysis at 600 °C for 2 h with KOH activation</td><td>150</td><td>0.05 – 2.0</td><td>1 C</td><td>511</td><td>307 (100)</td><td>[48]</td></tr><tr><td>Bagasse</td><td>N,P co-doped bagasse-based sheet-like mesoporous carbon by hydrothermal activation method</td><td>1307.21 to 2118.59</td><td>0.01 – 3.0</td><td>100 mA g<sup>-1</sup></td><td>2347.56/ 1186.59</td><td>816.36 (50)</td><td>[49]</td></tr><tr><td>Spongy pomelo peels</td><td>Carbonized at 900 °C for 3 h with a heating ramp of 2 °C min<sup>-1</sup>.</td><td>114</td><td>0.0 – 2.0</td><td>90 mA g<sup>-1</sup></td><td>450</td><td>452 (200)</td><td>[50]</td></tr><tr><td>CLR</td><td>Pyrolysed at 500 °C and further activated with KOH (1:6) at 900 °C for 1 h.</td><td>3141</td><td>0.005 – 3.0</td><td>1 C (372 mA g<sup>-1</sup>)</td><td>~834</td><td>386 (200)</td><td>This work</td></tr><tr><td>BCLR</td><td>Pyrolysed at 500 °C with 30 wt. % of pure boron, and further activated with KOH (1:6) at 900 °C for 1 h</td><td>2645</td><td>0.005 – 3.0</td><td>1 C (372 mA g<sup>-1</sup>)</td><td>~886</td><td>505 (200)</td><td>This work</td></tr></tbody></table>
<figure><img src="image_8.png" /><figcaption>Fig. 5. CV curves of a) CLR and b) BCLR at various scan rates, GCD curves for c) CLR and d) BCLR at different current densities, and discharge capacitances of e) CLR and f) BCLR at different current densities.</figcaption></figure>

between 1.5 and 0.1 V can be related to the irreversible solid electrolyte interface (SEI) film formation. This peak is not observed in the subsequent cycles, suggesting that the SEI formation predominantly occurred in the first cycle. The irreversible SEI formation in the first cycle is due to

the decomposition of the electrolyte that traps Li-ions permanently onto surfaces of the carbon materials, leading to a significant drop in the capacity (Fig. 3c, 3d) and resulted in an extremely low first cycle Coulombic efficiency (CE). From the second cycle onwards a non-zero
<table><caption>**Table 2**
Gravimetric capacitance of selected biomass-carbon-based non-aqueous supercapacitors.</caption><thead><tr><th>Electrode material</th><th>Capacitance (F g<sup>-1</sup>)</th><th>Electrolyte</th><th>Current (A g<sup>-1</sup>)</th><th>Ref.</th></tr></thead><tbody><tr><td>Porous graphene nanosheets</td><td>128.2</td><td>2.0 M EMIMBF<sub>4</sub>/ acetonitrile [BMIM]BF<sub>4</sub>/AN</td><td>1.0</td><td>[58]</td></tr><tr><td>Porous carbon material (CBW)</td><td>80</td><td>EMIMBF<sub>4</sub></td><td>2.0</td><td>[51]</td></tr><tr><td>3D hierarchical porous carbon from fulvic acid biomass</td><td>~124</td><td>EMIMBF<sub>4</sub></td><td>1.0</td><td>[59]</td></tr><tr><td>N and S co-doped activated carbon</td><td>70</td><td>EMIMFSI</td><td>1.0</td><td>[60]</td></tr><tr><td>Sulfur-doped carbon nanotubes</td><td>27</td><td>1 M TEABF<sub>4</sub>/ AN</td><td>—</td><td>[57]</td></tr><tr><td>Pine cone activated carbon</td><td>118.01</td><td>1 M TEA-BF<sub>4</sub></td><td>1</td><td>[61]</td></tr><tr><td>Spruce cone activated carbon</td><td>122.53</td><td>1 M TEA-BF<sub>4</sub></td><td>1</td><td></td></tr><tr><td>Larch cone activated carbon</td><td>105.61</td><td>1 M TEA-BF<sub>4</sub></td><td>1</td><td></td></tr><tr><td>Birch wood activated carbon</td><td>105</td><td>1 M TEA-BF<sub>4</sub></td><td>1</td><td>[62]</td></tr><tr><td>Spent mushroom substrate activated carbon</td><td>87</td><td>1 M TEA-BF<sub>4</sub></td><td>1</td><td></td></tr><tr><td>Pine cone-activated carbon sprayed-coated</td><td>105</td><td>1 M TEA-BF<sub>4</sub></td><td>0.5</td><td>[63]</td></tr><tr><td>Pine cone-activated carbon blade-coated</td><td>93</td><td>1 M TEA-BF<sub>4</sub></td><td>0.5</td><td></td></tr><tr><td>Pine cone-activated carbon pelletized</td><td>90</td><td>1 M TEA-BF<sub>4</sub></td><td>0.5</td><td></td></tr><tr><td>CLR</td><td>87</td><td>EMIMBF<sub>4</sub>/ acetonitrile</td><td>1.0</td><td>This work</td></tr><tr><td>BCLR</td><td>144</td><td>EMIMBF<sub>4</sub>/ acetonitrile</td><td>1.0</td><td>This work</td></tr></tbody></table>

intercalation/de-intercalation of anions in graphitic structures could be another plausible reason behind the rectangular shapes. In general, the ionic transportation phenomenon is diffusion-dominant that results in rectangular-shaped CV features [51,52]. At higher scan rates, an obvious change in the CV curve is observed. It acquires a more prolate shape as seen in Fig. 5a-b due to the ionic transport mechanism change to surface dominant, which is otherwise also known as the C-rate effect [51,52]. At high scan rates or C-rates, part of the electroactive process becomes inactive, thus leading to prolate shapes, and those inactive reactions can be reactivated at low C-rates, switching the shapes back to rectangular [52,53], which could be due to the pseudocapacitance provided by oxygen functional groups (C—O, C = O, OH, COOH) as well as intercalation/de-intercalation of anions in graphitic structure. The electrochemical performance of the materials was further evaluated through GCD curves (Fig. 5c, 5d). As can be seen, GCD curves at high current rates exhibited a well-symmetrical triangle, which discloses the reversible ion adsorption/desorption process and efficient ionic transfer at the electrode/electrolyte interfaces, which further highlights the EDLC characteristics of the LR-carbon materials. Fig. 5e-f displays the specific capacitance at different current densities, and the maximum discharge capacitance was achieved by the BCLR electrode for all current densities, with the highest value being 141 F g⁻¹ at 0.1 A g⁻¹ for BCLR. Sun et al., [54] reported that Graphitic porous carbon possesses structural merits for SCs application because of its high BET surface area, well-developed graphitic carbon lattice, and high packing density. The specific capacitance of the BCLR was higher than that of the CLR due to the synergistic effect of its graphitic and porous structure within the carbon network. Such structures can facilitate electron transfer and charge storage because the electrons can be efficiently delivered into the pore surface along the graphitic carbon fringes, while the porous

structures surrounded by the graphitized framework facilitates surface as well as space charge storage.

The electrochemical stability of the CLR and BCLR-based SCs were evaluated by successive GCD assays in which a current of 2.0 A/g was applied, and their results are summarized in Fig. 6a-d. BCLR electrode showed high retention in the capacitance with almost no loss over 4000 cycles, while CLR exhibited a gradual capacitance decay trend within 3500 cycles (Fig. 6a,c). The degradation in the cycling performance of CLR samples may be attributed to its predominantly amorphous carbon framework, which exhibits predominantly lower electrical conductivity than the graphitic structure. Both samples indicate an electrical double-layer behavior (Fig. 6b,d), and the better electrochemical performances of BCLR compared to CLR could also be explained by the optimal balance between graphitization, pore structure richer in mesopores, and surface chemistry in BCLR, which provides high conductivity and sufficient active sites for ion storage [55], besides BCLR has a more mesoporous structure which facilitates the ions diffusion because they can accommodate a considerable number of solvated electrolyte ions, which serve as ion storage reservoirs [55], and thus, improving the capacitance by favoring a fast double-layer charging and discharging process [56].

Table 2 compares the gravimetric capacitance performance of CLR and BCLR-based SCs with other similar devices reported in recent literature. The data displayed in Table 2 confirms the potential of the graphitic material (BCLR) as the potential electrode for SCs since it exhibited a very good performance compared to the ones shown in Table 2. For instance, the SCs based on sulfur-doped carbon nanotubes [57], displayed a low capacitance of 27 F g⁻¹ at 1 A g⁻¹, moreover the carbon nanotubes are much more expensive and its synthesis is highly complex. The SCs based on graphene nanosheets exhibited a capacitance of 128 F g⁻¹ at 1 A g⁻¹, and graphene is an expensive material as well. Thus, it can be concluded that BCLR material exhibits highly promising performance on SCs application, as also indicated in LIBs, suggesting that the BCLR could be employed as an efficient electrode for SCs and LIBs.

### 3. Conclusions

In summary, pine tree logging residues, a highly abundant and inexpensive biomass feedstock in northern countries, were thermchemically transformed into highly porous graphitic carbon using pure boron as an efficient catalyst to enhance the graphitization process at low temperatures. The boron-treated sample (BCLR) exhibited a lower specific surface area (2645 m² g⁻¹) than that of non-boron treated (CLR, 3141 m² g⁻¹); however, the boron-treated sample exhibited far more graphitic layers in its structure, highlighting its high graphitization degree. The high graphitization degree alongside its well-developed porosity helped to deliver a much higher specific capacity of 505 mAh g⁻¹ at 1 C for the BCLR anode at the end of 200 cycles whilst the respective capacity for CLR was 386 mAh g⁻¹. When applied as supercapacitor electrodes, the BCLR delivered a much higher specific capacitance of 144 F g⁻¹ at 1 A g⁻¹ compared to non-boron treated (87 F g⁻¹ at 1 A g⁻¹). Furthermore, BCLR exhibited excellent cycle stability (capacitance retention of 98 % over 4000 cycles). The physicochemical and electrochemical results confirm that graphitized porous carbon derived from logging residues is a promising candidate for high-rate electrochemical performance as electrodes in LIBs and SCs applications.

Appendix. Supplementary materials: The materials and methods are found in the supplementary information.

### Funding information

This work was supported by the financial support of the EU/Interreg Aurora (Project GreenBattery, grant no 20,357,574), EU/Interreg Aurora (Project: Nature Refines, grant no. 20361711), the Swedish Research Council FORMAS (grant no. 2021-00877), and Kempstiftelserna (grant no. JCSMK23-0145). AG, SSP, and MT thank
Bio4Energy - a Strategic Research Environment appointed by the Swedish government and the Swedish University of Agricultural Sciences. Dr. Glaydson dos Simoes Reis gratefully acknowledges financial support from the Research Council of Finland (Academy Research Fellows 2024, Project: Bio-Adsorb&Energy, grant No. 361583). The authors also acknowledge Business Finland for research funding 2021–2024, the University of Oulu (BATCircle2.0, No. 44612/31/2020).

## CRediT authorship contribution statement

**Sruthy E S:** Writing – original draft, Validation, Software, Methodology, Investigation, Formal analysis, Conceptualization. **Alejandro Grimm:** Writing – review & editing, Methodology, Formal analysis. **Menestreau Paul:** Writing – review & editing, Methodology, Investigation, Formal analysis. **Christie Thomas Cherian:** Writing – review & editing, Visualization, Validation, Funding acquisition, Data curation. **Mikael Thyrel:** Project administration, Funding acquisition. **Palanivel Molaiyan:** Writing – review & editing, Validation. **Ulla Lassi:** Writing – review & editing, Project administration, Data curation. **Shaikshavali Petnikota:** Writing – review & editing, Visualization, Investigation, Data curation, Conceptualization. **Glaydson Simões Dos Reis:** Writing – review & editing, Writing – original draft, Methodology, Formal analysis, Data curation, Conceptualization.

## Declaration of competing interest

The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Glaydson Simoes dos Reis reports financial support provided by Swedish University of Agricultural Sciences. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

## Acknowledgments

This work was supported by the financial support of the EU/Interreg Aurora (Project GreenBattery, grant no. 20357574), EU/Interreg Aurora (Project: Nature Refines, grant no. 20361711), the Swedish Research Council FORMAS (grant no. 2021–00877), and Kempestiftelserna (grant no. JCSMK23–0145). AG, SSP, and MT thank Bio4Energy - a Strategic Research Environment appointed by the Swedish government and the Swedish University of Agricultural Sciences. Dr. Glaydson dos Simoes Reis gratefully acknowledges financial support from the Research Council of Finland (Academy Research Fellows 2024, Project: Bio-Adsorb&Energy, grant No. 361583).

## Supplementary materials

Supplementary material associated with this article can be found, in the online version, at doi:10.1016/j.ceja.2025.100762.

## Data availability

Data will be made available on request.

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