A Cellulose-Derived Nanofibrous MnO2-TiO2-Carbon Composite as Anodic Material for Lithium-Ion Batteries

A bio-inspired nanofibrous MnO₂-TiO₂-carbon composite was prepared by utilizing natural cellulosic substances (e.g., ordinary quantitative ashless filter paper) as both the carbon source and structural matrix. Mesoporous MnO₂ nanosheets were densely immobilized on an ultrathin titania film precoated with cellulose-derived carbon nanofibers, which gave a hierarchical MnO₂-TiO₂-carbon nanoarchitecture and exhibited excellent electrochemical performances when used as an anodic material for lithium-ion batteries. The MnO₂-TiO₂-carbon composite with a MnO₂ content of 47.28 wt % exhibited a specific discharge capacity of 677 mAh g⁻¹ after 130 repeated charge/discharge cycles at a current rate of 100 mA g⁻¹. The contribution percentage of MnO₂ in the composite material is equivalent to 95.1% of the theoretical capacity of MnO₂ (1230 mAh g⁻¹). The ultrathin TiO₂ precoating layer with a thickness ca. 2 nm acts as a crucial interlayer that facilitates the growth of well-organized MnO₂ nanosheets onto the surface of the titania-carbon nanofibers. Due to the interweaved network structures of the carbon nanofibers and the increased content of the immobilized MnO₂, the exfoliation and aggregation, as well as the large volume change of the MnO₂ nanosheets, are significantly inhibited; thus, the MnO₂-TiO₂-carbon electrodes displayed outstanding cycling performance and a reversible rate capability during the Li⁺ insertion/extraction processes.     

Micron-Sized Monodisperse Particle LiNi0.6Co0.2Mn0.2O2 Derived by Oxalate Solvothermal Process Combined with Calcination as Cathode Material for Lithium-Ion Batteries

Ni-rich cathode LiNi_xCo_yMn_1-x-yO₂ (NCM, x ≥ 0.5) materials are promising cathodes for lithium-ion batteries due to their high energy density and low cost. However, several issues, such as their complex preparation and electrochemical instability have hindered their commercial application. Herein, a simple solvothermal method combined with calcination was employed to synthesize LiNi_0.6Co_0.2Mn_0.2O₂ with micron-sized monodisperse particles, and the influence of the sintering temperature on the structures, morphologies, and electrochemical properties was investigated. The material sintered at 800 °C formed micron-sized particles with monodisperse characteristics, and a well-order layered structure. When charged–discharged in the voltage range of 2.8–4.3 V, it delivered an initial discharge capacity of 175.5 mAh g⁻¹ with a Coulombic efficiency of 80.3% at 0.1 C, and a superior discharge capacity of 135.4 mAh g⁻¹ with a capacity retention of 84.4% after 100 cycles at 1 C. The reliable electrochemical performance is probably attributable to the micron-sized monodisperse particles, which ensured stable crystal structure and fewer side reactions. This work is expected to provide a facile approach to preparing monodisperse particles of different scales, and improve the performance of Ni-rich NCM or other cathode materials for lithium-ion batteries.     

Hollow Hemispherical Lithium Iron Silicate Synthesized by an Ascorbic Acid-Assisted Hydrothermal Method as a Cathode Material for Li Ion Batteries

High-capacity and high-voltage cathode materials are required to meet the increasing demand for energy density in Li ion batteries. Lithium iron silicate (Li₂FeSiO₄) is a cathode material with a high theoretical capacity of 331 mAh·g⁻¹. However, its poor conductivity and low Li ion diffusion coefficient result in poor capability, hindering practical applications. Morphology has an important influence on the properties of materials, and nanomaterials with hollow structures are widely used in electrochemical devices. Herein, we report a novel hollow hemispherical Li₂FeSiO₄ synthesized by a template-free hydrothermal method with the addition of ascorbic acid. The hollow hemispherical Li₂FeSiO₄ consisted of finer particles with a shell thickness of about 80 nm. After carbon coating, the composite was applied as the cathode in Li ion batteries. As a result, the hollow hemispherical Li₂FeSiO₄/C exhibited a discharge capacity as high as 192 mAh·g⁻¹ at 0.2 C, and the average capacities were 134.5, 115.5 and 93.4 mAh·g⁻¹ at 0.5, 1 and 2 C, respectively. In addition, the capacity increased in the first few cycles and then decayed with further cycling, showing a warm-up like behavior, and after 160 cycles the capacities maintained 114.2, 101.6 and 79.3 mAh·g⁻¹ at 0.5, 1 and 2 C, respectively. Such a method of adding ascorbic acid in the hydrothermal reaction can effectively synthesize hollow hemispherical Li₂FeSiO₄ with the enhanced electrochemical performance.     

A Hierarchical SnO2@Ni6MnO8 Composite for High-Capacity Lithium-Ion Batteries

Semiconductor-based composites are potential anodes for Li-ion batteries, owing to their high theoretical capacity and low cost. However, low stability induced by large volumetric change in cycling restricts the applications of such composites. Here, a hierarchical SnO₂@Ni₆MnO₈ composite comprising Ni₆MnO₈ nanoflakes growing on the surface of a three-dimensional (3D) SnO₂ is developed by a hydrothermal synthesis method, achieving good electrochemical performance as a Li-ion battery anode. The composite provides spaces to buffer volume expansion, its hierarchical profile benefits the fast transport of Li⁺ ions and electrons, and the Ni₆MnO₈ coating on SnO₂ improves conductivity. Compared to SnO₂, the Ni₆MnO₈ coating significantly enhances the discharge capacity and stability. The SnO₂@Ni₆MnO₈ anode displays 1030 mAh g⁻¹ at 0.1 A g⁻¹ and exhibits 800 mAh g⁻¹ under 0.5 A g⁻¹, along with high Coulombic efficiency of 95%. Furthermore, stable rate performance can be achieved, indicating promising applications.     

Tuning the Defects of Two-Dimensional Layered Carbon/TiO2 Superlattice Composite for a Fast Lithium-Ion Storage

Defect engineering is one of the effective ways to improve the electrochemical property of electrode materials for lithium-ion batteries (LIB). Herein, an organic functional molecule of p-phenylenediamine is embedded into two-dimensional (2D) layered TiO₂ as the electrode for LIB. Then, the 2D carbon/TiO₂ composites with the tuning defects are prepared by precise control of the polymerization and carbothermal atmospheres. Low valence titanium in metal oxide and nitrogen-doped carbon nanosheets can be obtained in the carbon/TiO₂ composite under a carbonization treatment atmosphere of N₂/H₂ gas, which can not only increase the electronic conductivity of the material but also provide sufficient electrochemical active sites, thus producing an excellent rate capability and long-term cycle stability. The prepared composite can provide a high capacity of 396.0 mAh g⁻¹ at a current density of 0.1 A g⁻¹ with a high capacitive capacity ratio. Moreover, a high specific capacity of 80.0 mAh g⁻¹ with retention rate of 85% remains after 10,000 cycles at 3.0 A g⁻¹ as well as the Coulomb efficiency close to 100%. The good rate-capability and cycle-sustainability of the layered materials are ascribed to the increase of conductivity, the lithium-ion transport channel, and interfacial capacitance due to the multi-defect sites in the layered composite.     

Improving Fast Charging-Discharging Performances of Ni-Rich LiNi0.8Co0.1Mn0.1O2 Cathode Material by Electronic Conductor LaNiO3 Crystallites

Fast charging-discharging is one of the important requirements for next-generation high-energy Li-ion batteries, nevertheless, electrons transport in the active oxide materials is limited. Thus, carbon coating of active materials is a common method to supply the routes for electron transport, but it is difficult to synthesize the oxide-carbon composite for LiNiO₂-based materials which need to be calcined in an oxygen-rich atmosphere. In this work, LiNi_0.8Co_0.1Mn_0.1O₂ (NCM811) coated with electronic conductor LaNiO₃ (LNO) crystallites is demonstrated for the first time as fast charging-discharging and high energy cathodes for Li-ion batteries. The LaNiO₃ succeeds in providing an exceptional fast charging-discharging behavior and initial coulombic efficiency in comparison with pristine NCM811. Consequently, the NCM811@3LNO electrode presents a higher capacity at 0.1 C (approximately 246 mAh g⁻¹) and a significantly improved high rate performance (a discharge specific capacity of 130.62 mAh g⁻¹ at 10 C), twice that of pristine NCM811. Additionally, cycling stability is also improved for the composite material. This work provides a new possibility of active oxide cathodes for high energy/power Li-ion batteries by electronic conductor LaNiO₃ coating.     

Preparation and Electrochemical Properties of LiNi2/3Co1/6Mn1/6O2 Cathode Material for Lithium-Ion Batteries

The cathode material LiNi_2/3Co_1/6Mn_1/6O₂ with excellent electrochemical performance was prepared successfully by a rheological phase method. The materials obtained were characterized by X-ray diffraction, scanning electron microscopy, electrochemical impedance spectroscopy and charge-discharge tests. The results showed that both calcination temperatures and atmosphere are very important factors affecting the structure and electrochemical performance of LiNi_2/3Co_1/6Mn_1/6O₂ material. The sample calcinated at 800 °C under O₂ atmosphere displayed well-crystallized particle morphology, a highly ordered layered structure with low defects, and excellent electrochemical performance. In the voltage range of 2.8–4.3 V, it delivered capacity of 188.9 mAh g⁻¹ at 0.2 C and 130.4 mAh g⁻¹ at 5 C, respectively. The capacity retention also reached 93.9% after 50 cycles at 0.5 C. All the results suggest that LiNi_2/3Co_1/6Mn_1/6O₂ is a promising cathode material for lithium-ion batteries.     

Effect of Residual Trace Amounts of Fe and Al in Li[Ni1/3Mn1/3Co1/3]O2 Cathode Active Material for the Sustainable Recycling of Lithium-Ion Batteries

As the explosive growth of the electric vehicle market leads to an increase in spent lithium-ion batteries (LIBs), the disposal of LIBs has also made headlines. In this study, we synthesized the cathode active materials Li[Ni_1/3Mn_1/3Co_1/3]O₂ (NMC) and Li[Ni_1/3Mn_1/3Co_1/3Fe_0.0005Al_0.0005]O₂ (NMCFA) via hydroxide co-precipitation and calcination processes, which simulate the resynthesis of NMC in leachate containing trace amounts of iron and aluminum from spent LIBs. The effects of iron and aluminum on the physicochemical and electrochemical properties were investigated and compared with NMC. Trace amounts of iron and aluminum do not affect the morphology, the formation of O3-type layered structures, or the redox peak. On the other hand, the rate capability of NMCFA shows high discharge capacities at 7 C (110 mAh g⁻¹) and 10 C (74 mAh g⁻¹), comparable to the values for NMC at 5 C (111 mAh g⁻¹) and 7 C (79 mAh g⁻¹), respectively, due to the widened interslab thickness of NMCFA which facilitates the movement of lithium ions in a 2D channel. Therefore, iron and aluminum, which are usually considered as impurities in the recycling of LIBs, could be used as doping elements for enhancing the electrochemical performance of resynthesized cathode active materials.     

Flake (NH4)6Mo7O24/Polydopamine as a High Performance Anode for Lithium Ion Batteries

Ammonium molybdate tetrahydrate ((NH₄)₆Mo₇O₂₄) (AMT) is commonly used as the precursor to synthesize Mo-based oxides or sulfides for lithium ion batteries (LIBs). However, the electrochemical lithium storage ability of AMT itself is unclear so far. In the present work, AMT is directly examined as a promising anode material for Li-ion batteries with good capacity and cycling stability. To further improve the electrochemical performance of AMT, AMT/polydopamine (PDA) composite was simply synthesized via recrystallization and freeze drying methods. Unlike with block shape for AMT, the as-prepared AMT/PDA composite shows flake morphology. The initial discharge capacity of AMT/PDA is reached up to 1471 mAh g⁻¹. It delivers a reversible discharge capacity of 702 mAh g⁻¹ at a current density of 300 mA g⁻¹, and a stable reversible capacity of 383.6 mA h g⁻¹ is retained at a current density of 0.5 A g⁻¹ after 400 cycles. Moreover, the lithium storage mechanism is fully investigated. The results of this work could potentially expand the application of AMT and Mo-based anode for LIBs.     

Enhanced Cyclability of Cr8O21 Cathode for PEO-Based All-Solid-State Lithium-Ion Batteries by Atomic Layer Deposition of Al2O3

Cr₈O₂₁ can be used as the cathode material in all-solid-state batteries with high energy density due to its high reversible specific capacity and high potential plateau. However, the strong oxidation of Cr₈O₂₁ leads to poor compatibility with polymer-based solid electrolytes. Herein, to improve the cycle performance of the battery, Al₂O₃ atomic layer deposition (ALD) coating is applied on Cr₈O₂₁ cathodes to modify the interface between the electrode and the electrolyte. X-ray photoelectron spectroscopy, scanning electron microscope, transmission electron microscope, and Fourier transform infrared spectroscopy, etc., are used to estimate the morphology of the ALD coating and the interface reaction mechanism. The electrochemical properties of the Cr₈O₂₁ cathodes are investigated. The results show that the uniform and dense Al₂O₃ layer not only prevents the polyethylene oxide from oxidization but also enhances the lithium-ion transport. The 12-ALD-cycle-coated electrode with approximately 4 nm Al₂O₃ layer displays the optimal cycling performance, which delivers a high capacity of 260 mAh g⁻¹ for the 125th cycle at 0.1C with a discharge-specific energy of 630 Wh kg⁻¹.     

Synthesis and Characterization of Sn/SnO2/C Nano-Composite Structure: High-Performance Negative Electrode for Lithium-Ion Batteries

Tin oxide (SnO₂) and tin-based composites along with carbon have attracted significant interest as negative electrodes for lithium-ion batteries (LIBs). However, tin-based composite electrodes have some critical drawbacks, such as high volume expansion, low capacity at high current density due to low ionic conductivity, and poor cycle stability. Moreover, complex preparation methods and high-cost carbon coating procedures are considered main challenges in the commercialization of tin-based electrodes for LIBs. In this study, we prepared a Sn/SnO₂/C nano-composite structure by employing a low-cost hydrothermal method, where Sn nanoparticles were oxidized in glucose and carboxymethyl cellulose CMC was introduced into the solution. Scanning electron microscope (SEM) and transmission electron microscope revealed the irregular structure of Sn nanoparticles and SnO₂ phases in the conductive carbon matrix. The as-prepared Sn/SnO₂/C nano-composite showed high first-cycle reversible discharge capacity (2248 mAhg⁻¹) at 100 mAg⁻¹ with a first coulombic efficiency of 70%, and also displayed 474.64 mAhg⁻¹ at the relatively high current density of about 500 mAg⁻¹ after 100 cycles. A low-cost Sn/SnO₂/C nano-composite with significant electrochemical performance could be the next generation of high-performance negative electrodes for LIBs.     

Electrical and Structural Properties of Li1.3Al0.3Ti1.7(PO4)3—Based Ceramics Prepared with the Addition of Li4SiO4

The currently studied materials considered as potential candidates to be solid electrolytes for Li-ion batteries usually suffer from low total ionic conductivity. One of them, the NASICON-type ceramic of the chemical formula Li_1.3Al_0.3Ti_1.7(PO₄)₃, seems to be an appropriate material for the modification of its electrical properties due to its high bulk ionic conductivity of the order of 10⁻³ S∙cm⁻¹. For this purpose, we propose an approach concerning modifying the grain boundary composition towards the higher conducting one. To achieve this goal, Li₄SiO₄ was selected and added to the LATP base matrix to support Li⁺ diffusion between the grains. The properties of the Li_1.3Al_0.3Ti_1.7(PO₄)₃−xLi₄SiO₄ (0.02 ≤ x ≤ 0.1) system were studied by means of high-temperature X-ray diffractometry (HTXRD); ⁶Li, ²⁷Al, ²⁹Si, and ³¹P magic angle spinning nuclear magnetic resonance spectroscopy (MAS NMR); thermogravimetry (TG); scanning electron microscopy (SEM); and impedance spectroscopy (IS) techniques. Referring to the experimental results, the Li₄SiO₄ additive material leads to the improvement of the electrical properties and the value of the total ionic conductivity exceeds 10⁻⁴ S∙cm⁻¹ in most studied cases. The factors affecting the enhancement of the total ionic conductivity are discussed. The highest value of σ_tot = 1.4 × 10⁻⁴ S∙cm⁻¹ has been obtained for LATP–0.1LSO material sintered at 1000 °C for 6 h.     

Synthesis and Electrochemical Characterization of LiNi0.5Co0.2Mn0.3O2 Cathode Material by Solid-Phase Reaction

In this paper, using four carbonates as raw materials, the cathode material LiNi_0.5Co_0.2Mn_0.3O₂ was prepared with the “ball milling-calcining” solid-phase synthesis method. The specific reaction process, which consists of the decomposition of the raw materials and the generation of target products, was investigated thoroughly using the TG-DSC technique. XRD, SEM and charge/discharge test methods were utilized to explore the influence of different sintering temperatures on the structure, morphology and electrochemical performance of the LiNi_0.5Co_0.2Mn_0.3O₂ cathode. The results show that 900~1000 °C is the appropriate synthesis temperature range. LiNi_0.5Co_0.2Mn_0.3O₂ synthesized at 1000 °C delivers optimal cycling stability at 0.5 C. Meanwhile, its initial discharge specific capacity and coulomb efficiency reached 167.2 mAh g⁻¹ and 97.89%, respectively. In addition, the high-rate performance of the cathode sample prepared at 900 °C is particularly noteworthy. Cycling at 0.5 C, 1 C, 1.5 C and 2 C, the corresponding discharge specific capacity of the sample exhibited 148.1 mAh g⁻¹, 143.1 mAh g⁻¹, 140 mAh g⁻¹ and 138.9 mAh g⁻¹, respectively.     

Highly Loaded and Binder-Free Molybdenum Trioxide Cathode Material Prepared Using Multi-Arc Ion Plating for Aqueous Zinc Ion Batteries

Aqueous zinc-ion batteries (ZIBS) are becoming more popular as the use of energy storage devices grows, owing to advantages such as safety and an abundant zinc supply. In this study, molybdenum powder was loaded directly on carbon fiber cloth (CFC) via multi-arc ion plating to obtain Mo@CFC, which was then oxidatively heated in a muffle furnace for 20 min at 600 °C to produce high mass loading α-MoO₃@CFC (α-MoO₃ of 12–15 mg cm⁻²). The cells were assembled with α-MoO₃@CFC as the cathode and showed an outstanding Zn²⁺ storage capacity of 200.8 mAh g⁻¹ at 200 mA g⁻¹ current density. The capacity retention rate was 92.4 % after 100 cycles, along with an excellent cycling performance of 109.8 mAh g⁻¹ following 500 cycles at 1000 mA g⁻¹ current density. Subsequently, it was shown that CFC-loaded α-MoO₃ cathode material possessed significantly improved electrochemical performance when compared to a cell constructed from commercial MoO₃ using conventional slurry-based electrode methods. This work presents a novel yet simple method for preparing highly loaded and binder-free cathodic materials for aqueous ZIBs. The results suggest that the highly loaded cathode material with a high charge density may be potentially employed for future flexible device assembly and applications.     

Enhanced Structural Stability and Electrochemical Performance of LiNi0.6Co0.2Mn0.2O2 Cathode Materials by Ga Doping

Structural instability during cycling is an important factor affecting the electrochemical performance of nickel-rich ternary cathode materials for Li-ion batteries. In this work, enhanced structural stability and electrochemical performance of LiNi_0.6Co_0.2Mn_0.2O₂ cathode materials are achieved by Ga doping. Compared with the pristine electrode, Li[Ni_0.6Co_0.2Mn_0.2]_0.98Ga_0.02O₂ electrode exhibits remarkably improved electrochemical performance and thermal safety. At 0.5C rate, the discharge capacity increases from 169.3 mAh g⁻¹ to 177 mAh g⁻¹, and the capacity retention also rises from 82.8% to 89.8% after 50 cycles. In the charged state of 4.3 V, its exothermic temperature increases from 245.13 °C to more than 271.24 °C, and the total exothermic heat decreases from 561.7 to 225.6 J·g⁻¹. Both AC impedance spectroscopy and in situ XRD analysis confirmed that Ga doping can improve the stability of the electrode/electrolyte interface structure and bulk structure during cycling, which helps to improve the electrochemical performance of LiNi_0.6Co_0.2Mn_0.2O₂ cathode material.     

Synthesis and Electrochemical Performance of V6O13 Nanosheets Film Cathodes for LIBs

V₆O₁₃ thin films were deposited on indium-doped tin oxide (ITO) conductive glass by a concise low-temperature liquid-phase deposition method and through heat treatment. The obtained films were directly used as electrodes without adding any other media. The results indicate that the film annealed at 400 °C exhibited an excellent cycling performance, which remained at 82.7% of capacity after 100 cycles. The film annealed at 400 °C with diffusion coefficients of 6.08 × 10⁻¹² cm²·s⁻¹ (Li⁺ insertion) and 5.46 × 10⁻¹² cm²·s⁻¹ (Li⁺ extraction) in the V₆O₁₃ film electrode. The high diffusion coefficients could be ascribed to the porous morphology composed of ultrathin nanosheets. Moreover, the film endured phase transitions during electrochemical cycling, the V₆O₁₃ partially transformed to Li_0.6V_1.67O_3.67, Li₃VO₄, and VO₂ with the insertion of Li⁺ into the lattice, and Li_0.6V_1.67O_3.67, Li₃VO₄, and VO₂ partially reversibly transformed backwards to V₆O₁₃ with the extraction of Li⁺ from the lattice. The phase transition can be attributed to the unique structure and morphology with enough active sites and ions diffusion channels during cycles. Such findings reveal a bright idea to prepare high-performance cathode materials for LIBs.     

Electrochemically Driven Phase Transition in LiCoO2 Cathode

Lithium cobalt oxide (LiCoO₂), which has been successfully applied in commercial lithium-ion batteries for portable devices, possesses a theoretical specific capacity of 274 mAh g⁻¹. However, its actual capacity is only half of the theoretical specific capacity, because the charging voltage is restricted below 4.2 V. If a higher charging voltage is applied, an irreversible phase transition of LiCoO₂ during delithiation would occur, resulting in severe capacity fading. Therefore, it is essential to investigate the electrochemically driven phase transition of LiCoO₂ cathode material to approach its theoretical capacity. In this work, it was observed that LiCoO₂ partially degraded to Co₃O₄ after 150 charging-discharging cycles. From the perspective of crystallography, the conventional cell of LiCoO₂ was rebuilt to an orthonormal coordinate, and the transition path from layered LiCoO₂ to cubic Co₃O₄ proposed. The theoretical analysis indicated that the electrochemically driven phase transition from LiCoO₂ to Co₃O₄ underwent several stages. Based on this, an experimental verification was made by doping LiCoO₂ with Al, In, Mg, and Zr, respectively. The doped samples theoretically predicted behavior. The findings in this study provide insights into the electrochemically driven phase transition in LiCoO₂, and the phase transition can be eliminated to improve the capacity of LiCoO₂ to its theoretical value.     

Enhancement of Y5−xPrxSb3−yMy (M = Sn,Pb) Electrodes for Lithium- and Sodium-Ion Batteries by Structure Disordering and CNTs Additives

The maximally disordered (MD) phases with the general formula Y_5−xPr_xSb_3−yM_y (M = Sn, Pb) are formed with partial substitution of Y by Pr and Sb by Sn or Pb in the binary Y₅Sb₃ compound. During the electrochemical lithiation and sodiation, the formation of Y_5-xPr_xSb_3-yM_yLi_z and Y_5−xPr_xSb_3−yM_yNa_z maximally disordered–high entropy intermetallic phases (MD-HEIP), as the result of insertion of Li/Na into octahedral voids, were observed. Carbon nanotubes (CNT) are an effective additive to improve the cycle stability of the Y_5−xPr_xSb_3−yM_y (M = Sn, Pb) anodes for lithium-ion (LIBs) and sodium-ion batteries (SIBs). Modification of Y_5−xPr_xSb_3−ySn_y alloys by carbon nanotubes allowed us to significantly increase the discharge capacity of both types of batteries, which reaches 280 mAh · g⁻¹ (for LIBs) and 160 mAh · g⁻¹ (for SIBs), respectively. For Y_5−xPrxSb_3−yPb_y alloys in which antimony is replaced by lead, these capacities are slightly smaller and are 270 mAh · g⁻¹ (for LIBs) and 155 mAh · g⁻¹ (for SIBs), respectively. Results show that structure disordering and CNT additives could increase the electrode capacities up to 30% for LIBs and up to 25% for SIBs.     

Insight into a Nitrogen-Doping Mechanism in a Hard-Carbon-Microsphere Anode Material for the Long-Term Cycling of Potassium-Ion Batteries

To investigate the alternatives to lithium-ion batteries, potassium-ion batteries have attracted considerable interest due to the cost-efficiency of potassium resources and the relatively lower standard redox potential of K⁺/K. Among various alternative anode materials, hard carbon has the advantages of extensive resources, low cost, and environmental protection. In the present study, we synthesize a nitrogen-doping hard-carbon-microsphere (N-SHC) material as an anode for potassium-ion batteries. N-SHC delivers a high reversible capacity of 248 mAh g⁻¹ and a promoted rate performance (93 mAh g⁻¹ at 2 A g⁻¹). Additionally, the nitrogen-doping N-SHC material also exhibits superior cycling long-term stability, where the N-SHC electrode maintains a high reversible capacity at 200 mAh g⁻¹ with a capacity retention of 81% after 600 cycles. DFT calculations assess the change in K ions’ absorption energy and diffusion barriers at different N-doping effects. Compared with an original hard-carbon material, pyridinic-N and pyrrolic-N defects introduced by N-doping display a positive effect on both K ions’ absorption and diffusion.     

Establish TiNb2O7@C as Fast-Charging Anode for Lithium-Ion Batteries

Intercalation-type metal oxides are promising active anode materials for the fabrication of safer rechargeable lithium-ion batteries, as they are capable of minimizing or even eliminating Li plating at low voltages. Due to the excellent cycle performance, high specific capacity and appropriate working potential, TiNb₂O₇ (TNO) is considered to be the candidate of anode materials. Despite a lot of beneficial characteristics, the slow electrochemical kinetics of the TNO-based anodes limits their wide use. In this paper, TiNb₂O₇@C was prepared by using the self-polymerization coating characteristics of dopamine to enhance the rate-performance and cycling stability. The TNO@C-2 particles present ideal rate performance with the discharge capacity of 295.6 mA h g⁻¹ at 0.1 C. Moreover, the TNO@C-2 anode materials exhibit initial discharge capacity of 177.4 mA h g⁻¹, providing 91% of capacity retention after 400 cycles at 10 C. The outstanding electrochemical performance can be contributed to the carbon layer, which builds fast lithium ion paths, enhancing the electrical conductivity of TNO. All these results confirm that TNO@C is a valid methodology to enhance rate-performance and cycling stability and is a new way to provide reliable and quickly rechargeable energy storage resources.