Specific Capacity Research Articles

Ethanediamine Intercalation Induced Hydrogen Bond Network in Vanadium Oxide for Ultralong‐Life Aqueous Ammonium Ion Batteries

Aqueous ammonium‐ion batteries (AAIBs) have received tremendous attention as a potential energy technology, but their development is severely challenged by the fact that the as‐reported electrode materials are usually unable to meet the requirements of high capacity and high stability simultaneously. Herein, an organic‐inorganic hybrid material of ethanediamine (EDA) intercalated vanadium oxide (VO‐EDA) is synthesized as a high‐performance anode material for AAIBs. The intercalated EDA molecules not only act as an electron donor to bind with NH4+, but also form hydrogen bonding network structures with vanadium oxides to facilitate charge/ion transfer. As a result, this hybrid material provides a high specific capacity of 104.4 mAh g−1 at 0.5 A g−1 and good cycling stability after 5000 cycles 10 A g−1 with a coulombic efficiency of ~100%. Moreover, the ammonium‐ion full cell based on VO‐EDA anode and NiHCF cathode achieves a specific capacity of 55 mAh g−1 at 0.1 A g−1 and impressive cycling stability with 88.6% capacity retention after 10000 cycles at 5 A g−1.

In‐situ Construction of Self‐Healing Polyelectrolyte/Polyzwitterion Coacervate Framework for High‐Performance Silicon Anodes

AbstractSilicon is considered as a promising candidate for anode materials due to its ultrahigh theoretical capacity and natural abundance. However, the commercialization is severely hampered by the large strain and short cycle life. Herein, we have synthesized a reversible polyelectrolyte/polyzwitterion coacervate framework to achieve high‐performance silicon anodes with high initial Coulombic efficiency (ICE) and stable cyclability. Such coacervate framework is formed via in‐situ free radical polymerization of zwitterionic 2‐methacryloyloxy ethyl phosphorylcholine (MPC) with polyacrylic acid (pAA) during heating the slurry. The resulting pAA/pMPC coacervate framework presents excellent adhesion, thermal stability, and negligible swelling in the electrolyte. Comparing with pAA, pAA/pMPC0.1 coacervate framework binder exhibits superior performance during charge/discharge. The ICE is improved from 84.41 %, to 87.61 %. After 250 cycles, the specific capacity of pAA/pMPC0.1 silicon anode is 1678 mAh g−1 with a retention of 78 % while the pAA silicon anode completely failed after less than 200 cycles. Such improvement is ascribed to the structural integrity of the electrode endowed by the self‐healing ability of pAA/pMPC coacervate framework. This work not only offers a feasible method to in‐situ construct coacervate framework with self‐healing capability to achieve high‐performance silicon anodes but also a compatible electrode preparation process for other high‐capacity materials.

Surface Gradient Desodiation Chemistry in Layered Oxide Cathode Materials

Sodium‐ion batteries (SIBs) as a promising technology for large‐scale energy storage have received unprecedented attention. However, the cathodes in SIBs generally suffer from detrimental cathode‐electrolyte interfacial side reactions and structural degradation during cycling, which leads to severe capacity fade and voltage decay. Here, we have developed an ultra‐stable Na0.72Ni0.20Co0.21Mn0.55Mg0.036O2 (NCM‐CS‐GMg) cathode material in which a Mg‐free core is encapsulated by a shell with gradient distribution of Mg using coprecipitation method with Mg‐hysteretic cascade feedstock followed by calcination. From the interior to outer surface of the shell, as the content of electrochemically inactive Mg gradually increases, the Na+ deintercalation amount gradually decreases after charged. Benefiting from this surface gradient desodiation, the surface transition metal (TM) ion migration from TM layers to Na layers is effectively inhibited, thus suppressing the layered‐to‐rock‐salt phase transition and the resultant microcracks. Besides, the less formation of high‐valence TM ions on the surface contributes to a stable cathode‐electrolyte interface. The as‐prepared NCM‐CS‐GMg exhibits remarkable cycling life over 3000 cycles with a negligible voltage drop (0.127 mV per cycle). Our findings highlight an effective way to developing sustainable cathode materials without compromising on the initial specific capacity for SIBs.

Surface Gradient Desodiation Chemistry in Layered Oxide Cathode Materials.

Sodium-ion batteries (SIBs) as a promising technology for large-scale energy storage have received unprecedented attention. However, the cathodes in SIBs generally suffer from detrimental cathode-electrolyte interfacial side reactions and structural degradation during cycling, which leads to severe capacity fade and voltage decay. Here, we have developed an ultra-stable Na0.72Ni0.20Co0.21Mn0.55Mg0.036O2 (NCM-CS-GMg) cathode material in which a Mg-free core is encapsulated by a shell with gradient distribution of Mg using coprecipitation method with Mg-hysteretic cascade feedstock followed by calcination. From the interior to outer surface of the shell, as the content of electrochemically inactive Mg gradually increases, the Na+ deintercalation amount gradually decreases after charged. Benefiting from this surface gradient desodiation, the surface transition metal (TM) ion migration from TM layers to Na layers is effectively inhibited, thus suppressing the layered-to-rock-salt phase transition and the resultant microcracks. Besides, the less formation of high-valence TM ions on the surface contributes to a stable cathode-electrolyte interface. The as-prepared NCM-CS-GMg exhibits remarkable cycling life over 3000 cycles with a negligible voltage drop (0.127 mV per cycle). Our findings highlight an effective way to developing sustainable cathode materials without compromising on the initial specific capacity for SIBs.

Carbon-modified NiCo2O4 as an electrode material for supercapacitors

Transition metal oxides are a promising class of electrode materials for pseudocapacitors due to their high electrochemical activity and eco-friendly nature. However, they possess poor intrinsic conductivity which results in the low energy density of the assembled supercapacitors. In this study, electrodes composed of amorphous C-modified NiCo2O4 (C/NiCo2O4/NF) on nickel foam substrate were prepared by electrochemical deposition and thermostatic heating method. The incorporation of amorphous C compensates for the low electrical conductivity of NiCo2O4 materials, thereby significantly enhancing the electrochemical performance. The galvanostatic charge-discharge (GCD) test results reveal an impressive specific capacitance of 379.4 mF/cm2 at a current density of 1.5 mA/cm2, and with a capacitance retention rate of 87.1 %. In addition, the symmetric supercapacitor assembled using C/NiCo2O4 electrode materials exhibits exceptional energy density and power density, reaching maximum values of 522.3 μWh/cm2 and 900 μW/cm2 respectively. The device is capable of illuminating LED for up to 8 min, further demonstrating its practical applicability. These results underscore the feasibility and promise of C/NiCo2O4 as an electrode material for the advancement of high-performance supercapacitors.

By Introducing Multiple Hydrogen Bonds Endows MOF Electrodes with an Enhanced Structural Stability.

Recently, metal-organic frameworks (MOFs) have attracted great interest in energy storage areas. However, the poor structural stability of MOFs derived from weak coordination bonds limits their applications. Here, quadruple hydrogen bonds (H-bonds) were introduced onto the MOFs to enhance their structural stability. Cross-linked networks could be formed between molecules owing to multiple H-bonds, strengthening the framework stability. Moreover, the dynamic reversibility of H-bonds could endow MOFs with self-healing ability. Furthermore, due to lower binding energy compared to coordination bonds, H-bonds break preferentially when subjected to internal stress, thus protecting the MOFs. Consequently, the as-prepared self-healing hybrid (SHH-Cu-MOF@Ti3C2TX) exhibited high capacitance retention (89.4%) after 5000 cycles at 1 A g-1, while that hybrid without dynamic H-bonds (H-Cu-MOF@Ti3C2TX) presented a 79.9% retention, delivering an enhancement in cycling stability. Moreover, an asymmetric supercapacitor (ASC) was fabricated by employing SHH-Cu-MOF@Ti3C2TX and activated carbon (AC) as the electrodes. The ASC delivered a specific capacitance (47.4 F g-1 at 1 A g-1), an energy density (16.9 Wh kg-1), and a power density (800 W kg-1) as well as good rate ability (retains 81% of its initial capacitance from 0.2 A g-1 to 5 A g-1).

A eutectic mixture catalyzed straight forward production of functional carbon from Sargassum tenerrimum for energy storage application

Here, we present a sustainable and scalable approach for synthesizing functionalized nanomaterials directly from an abundant natural seaweed resource coupled with a green eutectic mixture. The study utilized crushed seaweed granules obtained from fresh brown seaweed Sargassum tenerrimum (ST) and a eutectic mixture generated through the complexation of urea and a metal salt, which act as both solvent and catalyst to facilitate the straightforward production of metal oxide functionalized nanomaterials. Subjecting seaweed granules and the eutectic mixture to pyrolysis at temperatures between 700 °C and 900 °C in a nitrogen (N2) atmosphere resulted in the formation of ST-derived carbon (STC) functionalized with β-MnO2. The nanoneedles thus synthesized were examined for their electrochemical properties in both three-electrode and two-electrode configurations, employing 6 M KOH and 1 M Na2SO4 as electrolytes. Within the three-electrode framework, β-MnO2 functionalized STC at 800 °C (MSTC-8) displayed a remarkable specific capacitance, of 685.1 F g−1 in alkaline electrolyte and 308.3 F g−1 in neutral electrolyte at 0.1 A g−1, demonstrating a superior performance compared to MSTC-7 and MSTC-9. Additionally, two-electrode experiments and evaluations of cyclic stability were performed on MSTC-7, MSTC-8, and MSTC-9 symmetric supercapacitors. The fabricated symmetric supercapacitor in Na2SO4 with the operational voltage window up to 1.7 V, achieved a maximum energy density of 45.5 Wh/kg and a power density of 172.66 W kg−1. Moreover, the current investigation highlights the enduring performance of MSTC-8//MSTC-8 symmetric supercapacitor, with a capacitance retention of 95 % and 80 % over 20,000 cycles in KOH and Na2SO4 electrolytes respectively.

Hydrogen‐Bonded Organic Frameworks‐based Electrolytes with Controllable Hydrogen Bonding Networks for Solid‐State Lithium Batteries

The lack of stable solid‐state electrolytes (SSEs) with high‐ionic conductivity and rational design of electrode/electrolyte interfaces remains challenging for solid‐state lithium batteries. Here, for the first time, a high‐performance solid‐state lithium–oxygen battery is developed based on the Li‐ion‐conducted hydrogen‐bonded organic framework (LHOF) electrolyte and the core‐shell HOF‐DAT@CNT cathode with a few layers of HOF‐DAT on surface of carbon nanotubes. Benefiting from the abundant dynamic hydrogen bonding network in LHOF‐DAT SSEs, fast Li+ ion transport (2.2 × 10–4 S cm–1), a high Li+ transfer number (0.88), and a wide electrochemical window of 5.05 V are achieved. Symmetric batteries constructed with LHOF‐DAT SSEs exhibit a stably cycled duration of over 1400 h, which mainly stems from the jumping sites that promote a uniformly high rate of Li+ flux and the hydrogen‐bonding network structure that can relieve the structural changes during Li+ transport. LHOF‐DAT SSEs‐based Li–O2 batteries exhibit high specific capacity (10335 mAh g−1), and stable cycling life up to 150 cycles. Moreover, the solid‐state lithium metal battery with LHOF‐DAT SSEs endow good rate capability (128.8 mAh g–1 at 1 C), long‐term discharge/charge stability (210 cycles). The design of LHOF‐DAT SSEs opens an avenue for the development of novel SSEs‐based solid‐state lithium batteries.

Direct Upcycling of Degraded LiCoO2 Material Toward High‐Performance Single‐Crystal NCM Cathode

AbstractThe growing volume of spent lithium‐ion batteries (LIBs) with degraded LiCoO2 (D‐LCO) cathodes is arising as an environmental concern as well as a waste of strategic resources. Current recycling strategies for D‐LCO materials primarily focus on metal extractions (Li and Co), which produce large quantities of wastewater and waste residues and consume substantial amounts of energy. Inspiringly, the rapid proliferation of electric vehicles has catalyzed the ever‐increasing production of LIBs with ternary layered oxides as the prevalent cathode materials. Herein, this work reports a simple, green, and economic upcycling strategy for direct transformation of D‐LCO into high‐performance single‐crystal LiNi1/3Co1/3Mn1/3O2 (NCM111) cathode materials. By simultaneous lithium replenishment, particle size reduction, and chemical composition engineering in the upcycling process, the NCM111 product delivers a high specific capacity (159.0 mAh g−1 at 0.1 C) and an excellent cycling stability (82.1% retention after 200 cycles at 1 C), outperforming those of commercial materials. This work highlights the immense potential of upcycling strategies in mitigating the environmental ramifications of spent LIBs and paves the way for the sustainable development of LIBs industry.

Hydrogen-Bonded Organic Frameworks-based Electrolytes with Controllable Hydrogen Bonding Networks for Solid-State Lithium Batteries.

The lack of stable solid-state electrolytes (SSEs) with high-ionic conductivity andrational design of electrode/electrolyte interfaces remains challenging for solid-state lithium batteries. Here, for the first time, a high-performance solid-state lithium-oxygen battery is developed based on the Li-ion-conducted hydrogen-bonded organic framework (LHOF) electrolyte and the core-shell HOF-DAT@CNT cathode with a few layers of HOF-DAT on surface ofcarbon nanotubes. Benefiting from the abundant dynamic hydrogen bonding network inLHOF-DAT SSEs, fast Li+ ion transport (2.2 × 10-4 S cm-1), a high Li+ transfer number (0.88), and a wide electrochemical window of 5.05 V are achieved. Symmetric batteries constructed with LHOF-DAT SSEs exhibit a stably cycled duration of over 1400 h, which mainly stems from the jumping sites that promote a uniformly high rate of Li+ flux and the hydrogen-bonding network structure that can relieve the structural changes during Li+ transport. LHOF-DAT SSEs-based Li-O2 batteries exhibit high specific capacity (10335 mAh g-1), and stable cycling life up to 150 cycles. Moreover, the solid-state lithium metal battery with LHOF-DAT SSEs endow good rate capability (128.8 mAh g-1 at 1 C), long-term discharge/charge stability (210 cycles). The design of LHOF-DAT SSEs opens an avenue for the development of novel SSEs-based solid-state lithium batteries.

Recent Advances in Oxygen Redox Activity of Lithium‐Rich Manganese‐Based Layered Oxides Cathode Materials: Mechanism, Challenges and Strategies

AbstractLithium‐rich manganese‐based layered oxides (LRMOs) have been regarded as a promising category of cathode materials due to their high specific capacity on basis of joint anionic(oxygen) /cationic redox chemistry at a high voltage, thus high energy density. The anionic redox play the key and restive roles in LRMOs, contributing the extra capacity, meanwhile being associated with several unfavorable structural and electrochemical issues. This work systematically enumerates the oxygen redox mechanisms, and challenges associated with oxygen‐anion redox in LRMOs, including irreversible transition metal migration, phase transition, and the capacity/voltage decay, etc. The recent progress made in modification of LRMOs with particular emphasis to promoting the reversible oxygen redox reaction and inhibiting the irreversible oxygen release are summarized, followed by an outlook on the future rational design and development of LRMOs. This comprehensive review and perspective are expected to provide insights for the greater utilization of oxygen redox in LRMOs and other related materials.

Manipulation of Linked Phosphorus Chemistry to Enhance the Battery Performance of Phenazine‐Based Porous Polymers

AbstractOrganic p‐type cathodes have captured increasing attention for lithium‐organic batteries due to their high voltage output. However, because of the low electronic and ionic conductivity, the p‐type organic electrode materials often show sluggish reaction kinetics and hence low capacities and poor cyclability. In this work, three conjugated polymers (Pz‐TPPO, Pz‐TPPS, and Pz‐TPP) based on p‐type phenazine linked with triphenyl phosphine are reported with different chemical modifications of phosphorus atom. Through oxidation and sulfuration of phosphorus atoms, the electron‐accepting property strength is increased, resulting in higher electronic conductivity of Pz‐TPPO and Pz‐TPPS. It is also found that the P═O unit in Pz‐TPPO exhibits stronger Li+ coordination, which can bring anions into close proximity to the redox centers, further improving the anion shuttling during charge and discharge. All these lead to the best lithium‐organic battery performance of Pz‐TPPO, such as high voltage output (3.1–3.9 V), high reversible specific capacity (149 mAh g−1 at 0.2 A g−1) and excellent cycle stability. The potential application has also been demonstrated in Pz‐TPPO//graphite full battery. This work provides a novel strategy for designing donor–acceptor (D–A) conjugated polymer by simple phosphorus modification toward high‐performance organic batteries.

KHCO3 chemical-activated hydrothermal porous carbon derived from jackfruit inner skin for supercapacitor applications

The reuse of waste biomass resources had become a hot spot in the sustainable development of human society. Due to the complexity of biomass composition and microstructure, the quality reproducibility of biomass porous carbon was poor. Therefore, it was of great significance to develop a reliable method for preparing porous carbon from biomass. In this paper, a combination of hydrothermal carbonization treatment and mild activation of KHCO3 was used to prepare iron-modified porous carbon with carbon spheres/nanoplates structure, which promoted ion/electrolyte diffusion and increased the accessibility between surface area and electrolyte ions. Therefore, the active porous carbon from the Jackfruit inner skin has good specific capacitance (273.2 F/g at 1 A/g) and good cycle stability, and the capacitance loss is only 6.6 % after 10,000 charge discharge cycles. The above results showed that hydrothermal treatment and mild activation methods provided an effective way to transform waste biomass into high-performance electrode material.

Ni3V2O8 Marigold Structures with rGO Coating for Enhanced Supercapacitor Performance.

In this work, Ni3V2O8 (NVO) and Ni3V2O8-reduced graphene oxide (NVO-rGO) are synthesized hydrothermally, and their extensive structural, morphological, and electrochemical characterizations follow subsequently. The synthetic materials' crystalline structure was confirmed by X-ray diffraction (XRD), and its unique marigold-like morphology was observed by field emission scanning electron microscopy (FESEM). The chemical states of the elements were investigated via X-ray photoelectron spectroscopy (XPS). Electrochemical impedance spectroscopy (EIS), Galvanostatic charge-discharge (GCD), and cyclic voltammetry (CV) were used to assess the electrochemical performance. A specific capacitance of 132 F/g, an energy density of 5.04 Wh/kg, and a power density of 187 W/kg were demonstrated by Ni3V2O8-rGO. Key electrochemical characteristics were b = 0.67; a transfer coefficient of 0.52; a standard rate constant of 6.07 × 10-5 cm/S; a diffusion coefficient of 5.27 × 10-8 cm2/S; and a series resistance of 1.65 Ω. By employing Ni3V2O8-rGO and activated carbon, an asymmetric supercapacitor with a specific capacitance of 7.85 F/g, an energy density of 3.52 Wh/kg, and a power density of 225 W/kg was achieved. The series resistance increased from 4.27 Ω to 6.63 Ω during cyclic stability tests, which showed 99% columbic efficiency and 87% energy retention. The potential of Ni3V2O8-rGO as a high-performance electrode material for supercapacitors is highlighted by these findings.

Tailored synthesis of a unique two-dimensional pretzel-like core-shell SnO2/C composite for improved lithium storage performance

In this research, a unique two-dimensional (2D) core-shell SnO2/C composite with a distinctive pretzel-like morphology was successfully synthesized using the tin-citrate complex as the tin source, and glucose as the carbon source through a hydrothermal synthesis, and followed by a high-temperature carbonization process. When assessed as an anode for lithium-ion batteries (LIBs), the composite demonstrated a significant specific capacity of 529 mAh g−1 at a current density of 200 mA g−1 after 100 cycles. Furthermore, it maintained ca. 200 mAh g−1 at a high current density of 1.6 A g−1, indicating excellent cycling stability and rate capability. The remarkable electrochemical performance can be ascribed to the well-dispersed nanoscale SnO2 particles within the amorphous carbon matrix, the distinctive core-shell structure and 2D pretzel-like conductive network. The prepared SnO2/C composite can be a promising alternative anode for future LIBs, offering higher energy density, prolonged cycle life, and faster charging capability compared to traditional graphite-based anodes.

Multifunctional surface modification to enhance the electrochemical performance of lithium-rich manganese-based cathode materials

The preparation of high-performance lithium-rich manganese-based cathode materials (LLOs) require attention to the redox of anions and the migration of transition metals (TM) during the cycling process. In this study, Ce ion-doped Li-rich cathode coated with La0.2Ce0.8O2, which has abundant oxygen vacancies on its surface, was prepared. The presence of the oxygen storage material La0.2Ce0.8O2 can effectively absorb the irreversible oxygen generated during cycling, preventing it from reacting with the electrolyte to form thick cathode electrolyte interface (CEI) coatings. These coatings hinder the relative activity of lattice oxygen in the bulk phase, reducing the specific capacity of the material. Additionally, the 5d metal ion Ce carries a large nuclear charge, causing a 'pinning effect' when it integrates into the LLOs structure. This effect reduces thermal oscillation in the lattice, impedes TM migration during battery charging and discharging, and effectively prevents voltage decay. Results indicate that after 100 cycles at 1C and 25 °C, the surface-coated materials maintain a discharge-specific capacity of 194 mAh/g, compared to 158 mAh/g for uncoated material. Voltage decay decreased from 4.4 mV/cycle to 1.8 mV/cycle, with an ICE of 91.5 % versus the original material's 82.8 %. The modified material also exhibits improved rate performance, retaining a specific capacity of 162 mAh/g at 3C, in contrast to the original material's 123 mAh/g.

Interfacial engineering in SnO2-embedded graphene anode materials for high performance lithium-ion batteries

Tin dioxide is regarded as an alternative anode material rather than graphite due to its high theoretical specific capacity. Modification with carbon is a typical strategy to mitigate the volume expansion effect of SnO2 during the charge process. Strengthening the interface bonding is crucial for improving the electrochemical performance of SnO2/C composites. Here, SnO2-embedded reduced graphene oxide (rGO) composite with a low graphene content of approximately 5 wt.% was in situ synthesized via a cetyltrimethylammonium bromide (CTAB)-assisted hydrothermal method. The structural integrity of the SnO2/rGO composite is significantly improved by optimizing the Sn–O–C electronic structure with CTAB, resulting a reversible capacity of 598 mAh g−1 after 200 cycles at a current density of 1 A g−1. CTAB-assisted synthesis enhances the rate performance and cyclic stability of tin dioxide/graphene composites, and boosts their application as the anode materials for the next-generation lithium-ion batteries.

Low-carbon emitting Fe-cycle recovery of battery-grade FePO4 from biogas slurry for Li-battery application

Under the background of carbon peaking and carbon neutrality in China, anaerobic digestion of sludge to produce methane was an important way to recover biomass energy. But plenty of as-generated biogas slurry (BS) with high P concentration was valuable and difficult to dispose. Here, this work proposed a low-carbon emitting Fe-cycle strategy to recover battery-grade FePO4 from BS. At pH=1.0, the P-leaching rate of Fe-sludge (42.93 ± 1.49 mg g−1) generated by polymerized ferrous sulfate (an inorganic polymer coagulant) addition into BS was 93.46 ± 3.56% and high-purity FePO4 (99.0%) could further be obtained by Fe3+ supplement and pH adjustment (pH=2.0). The contents of all elements in recovered FePO4 product fully complied with the battery grade of national industry standard of China (HG/T 4701-2021). After battery-grade FePO4 precipitate separation, recovery solution (RS) with remaining Fe3+ was reutilized to remove 88.05 ± 1.77% of P when mixed with BS wit RS/BS ratio of 2:1, thus achieving a Fe cycle utilization. Meanwhile, the recovery cost of 5.42 $/kg P and CO2 emissions of 80.83 kg/kg P were lower than those of current FePO4 industrial production (14.60 $/kg P and 110.60 kg/kg P). Finally, the LiFePO4/C cathode material based on recovered FePO4 from BS exhibited stable discharge specific capacity of 84.6–100.2 mAh/g during 100 charge–discharge cycles. In general, this study successfully manifested the feasibility of novel Fe-cycle battery-grade FePO4 recovery strategy from wastewater, paving a viable low-carbon emitting pathway for future Li-battery manufacture industry.

Facile hydrothermal synthesis of a tri-metallic Cu-Mn-Ni oxide-based electrochemical pseudo capacitor.

Transition metal oxide nanocomposites with heterostructures have gained a lot of attention for use in supercapacitors owing to their low cost, high surface area, fast transport of ions and electrons and high specific capacitance due to efficacious interplay between the electrode and the electrolytes. In this study, we fabricated tri-metallic Cu, Mn, Ni(CMNO), bi-metallic Mn, Ni(MNO) and mono-metallic Ni(NO) oxides through a facile hydrothermal route. All the fabricated materials were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and energy dispersive spectroscopy (EDX), and their electrochemical properties were studied using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and galvanostatic charge-discharge (GCD). The CMNO material showed remarkable electrochemical performance with a specific capacitance of 790.63 F g-1 at a current density of 1 A g-1, surpassing the performance of MNO (438.4 F g-1) and NO (290.82 F g-1). Furthermore, CMNO showed high cycling stability with a retention of 96.7% specific capacitance after 8000 cycles. Based on remarkable and unique properties, the CMNO material is regarded as a promising material for new-generation pseudo-capacitor applications.

Nitrogen and sulfur co-doped carbonized lignin nanotubes for supercapacitor applications

Carbon electrode material is crucial for the development of electric double-layered supercapacitor in clean energy storage and rechargeable aspects. Although lignin consists the promising biomass based carbon resource for containing higher carbon atom ratio than 60 %, it is still the difficult challenge to precisely tailoring the porous structure characteristics and surface property to facilitate the electrolyte penetration and rapid ion transportation. Herein, the lignin nanotubes (LNT) were successfully synthesized in a convenient molecular self-assembly way, which were subsequently carbonized and activated, with introduction of melamine as nitrogen doping agent, into hetero-atom doped lignin carbon nanotubes (LCNT) as electrode material for supercapacitor. The resultant LCNT exhibit excellent pore structure, and high degree of graphitization. At a current density of 0.5 A/g, the as high specific capacitance as 391.4 F/g was achieved. Furthermore, under symmetric double-layered capacitor electrode systems, the as prepared N, S co-doped LCNT electrode demonstrated a specific capacitance of 28.6 F/g at a high current density of 20 A/g, which presented a practically applicable energy storage efficiency. It has convincingly demonstrate the substantial potential of LCNT as biomass derived carbon materials for electrochemical energy storage devices, positioning them as a promising and competitive candidate for electrode materials.