Properties of lithium iron phosphate prepared by biomass-derived carbon coating for flexible lithium ion batteries

Doping LiFePO4 with Al3+: Suppression of Anti-Site Defects and Implications for Battery Recycling

In this study, a group of aluminum-doped lithium iron phosphate (LFP) with varying dopant concentrations (Li1-3x Al x FePO4/C, where x = 0.01-0.03) was synthesized via a solid-state reaction. Comprehensive analysis revealed that the aluminum dopant was uniformly distributed across the crystals of the synthesized samples. Notably, minor doping (x ≤ 0.01) helped reduce the formation of antisite defects within the LFP structure, lowering the defect content to 1.67% compared to 2.04% in undoped LFP. Further examination corroborated the presence of antisite defects and confirmed their reduced concentration in aluminum-doped LFP. Electrochemically, LAFP01 with x = 0.01 (or 1% aluminum doping) demonstrated an increased lithium-ion diffusion coefficient and superior electrochemical performance, achieving a discharge capacity of 155.6 mA h/g at a 0.1 C rate and surpassing that of undoped LFP. The performance improvement was more evident under rapid charge and discharge conditions, where LAFP01 maintained a higher specific capacity (86 mA h/g compared to 78 mA h/g for undoped LFP) at a current density of 5 C or greater. This study suggests that the reduced antisite defects with small aluminum doping could potentially contribute to the improved electrochemical characteristics of LFP cathodes, offering insights into enhancing lithium-ion battery performance and managing aluminum impurities in battery recycling processes.

Biomass-Derived Carbon Utilization for Electrochemical Energy Enhancement in Lithium-Ion Batteries

Cathodes made of LiFePO4 (LFP) offer numerous benefits including being non-toxic, eco-friendly, and affordable. The distinctive olivine structure of LFP cathodes contributes to their electrochemical stability. Nonetheless, this structure is also the cause of their low ionic and electronic conductivity. To enhance these limitations, an uncomplicated approach has been effectively employed. A straightforward solid-state synthesis technique is used to apply a coating of biomass from potato peels to the LFP cathode, boosting its electrochemical capabilities. Potato peels contain pyridinic and pyrrolic nitrogen, which are conducive to ionic and electronic movement and facilitate pathways for lithium-ion and electron transfer, thus elevating electrochemical performance. When coated with nitrogen-doped carbon derived from potato peel biomass (PPNC@LFP), the LFP cathode demonstrates an improved discharge capacity of 150.39 mAh g-1 at a 0.1 C-rate and 112.83 mAh g-1 at a 1.0 C-rate, in contrast to the uncoated LFP which shows capacities of 141.34 mAh g-1 and 97.72 mAh g-1 at the same rates, respectively.

Enhanced stability of nitrogen doped porous carbon fiber on cathode materials for high performance lithium–sulfur batteries

Lithium–sulfur (Li–S) batteries are considered to be one of the candidates for high-energy density storage systems due to their ultra-high theoretical specific capacity of 1675 mA h g⁻¹. However, problems of rapid capacity decay, sharp expansion in volume of the active material, and the shuttle effect have severely restricted their subsequent development and utilization. Herein, we design a nitrogen-doped porous carbon nanofiber (NPCNF) network as a sulfur host by the template method. The NPCNF shows a feather-like structure. After loading sulfur, the NPCNF/S composite can maintain a hierarchically porous structure. A high discharge capacity of 1301 mA h g⁻¹ is delivered for the NPCNT/S composite at 0.1C. The reversible charge/discharge capacity at 2C is 576 mA h g⁻¹, and 700 mA h g⁻¹ is maintained after 500 cycles at 0.5C. The high electrochemical performance of this NPCNT/S composite is attributed to the synergy effects of abundant N active sites and high electrical conductivity of the material.

The conductive network of nitrogen-doped porous carbon nanofibers was successfully prepared by the template method. The doping of nitrogen and the synergistic effect of mesopores and micropores reduce the energy barrier of Li⁺ migration in the material.

Enhanced Electrochemical Performance of LiFePO4 Originating from the Synergistic Effect of ZnO and C Co-Modification

Olivine-structure LiFePO₄ is considered as promising cathode materials for lithium-ion batteries. However, the material always sustains poor electron conductivity, severely hindering its further commercial application. In this work, zinc oxide and carbon co-modified LiFePO₄ nanomaterials (LFP/C-ZnO) were prepared by an inorganic-based hydrothermal route, which vastly boosts its performance. The sample of LFP/C-xZnO (x = 3 wt%) exhibited well-dispersed spherical particles and remarkable cycling stability (initial discharge capacities of 138.7 mAh/g at 0.1 C, maintained 94.8% of the initial capacity after 50 cycles at 0.1 C). In addition, the cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) disclose the reduced charge transfer resistance from 296 to 102 Ω. These suggest that zinc oxide and carbon modification could effectively minimize charge transfer resistance, improve contact area, and buffer the diffusion barrier, including electron conductivity and the electrochemical property. Our study provides a simple and efficient strategy to design and optimize promising olivine-structural cathodes for lithium-ion batteries.

Porous SnO2/C Nanofiber Anodes and LiFePO4/C Nanofiber Cathodes with a Wrinkle Structure for Stretchable Lithium Polymer Batteries with High Electrochemical Performance

Stretchable lithium batteries have attracted considerable attention as components in future electronic devices, such as wearable devices, sensors, and body-attachment healthcare devices. However, several challenges still exist in the bid to obtain excellent electrochemical properties for stretchable batteries. Here, a unique stretchable lithium full-cell battery is designed using 1D nanofiber active materials, stretchable gel polymer electrolyte, and wrinkle structure electrodes. A SnO2/C nanofiber anode and a LiFePO4/C nanofiber cathode introduce meso- and micropores for lithium-ion diffusion and electrolyte penetration. The stretchable full-cell consists of an elastic poly(dimethylsiloxane) (PDMS) wrapping film, SnO2/C and LiFePO4/C nanofiber electrodes with a wrinkle structure fixed on the PDMS wrapping film by an adhesive polymer, and a gel polymer electrolyte. The specific capacity of the stretchable full-battery is maintained at 128.3 mAh g-1 (capacity retention of 92%) even after a 30% strain, as compared with 136.8 mAh g-1 before strain. The energy densities are 458.8 Wh kg-1 in the released state and 423.4 Wh kg-1 in the stretched state (based on the electrode), respectively. The high capacity and stability in the stretched state demonstrate the potential of the stretchable battery to overcome its limitations.

Cr2P2O7 as a Novel Anode Material for Sodium and Lithium Storage

The development of new appropriate anode material with low cost is still main issue for sodium-ion batteries (SIBs) and lithium-ion batteries (LIBs). Here, Cr2P2O7 with an in-situ formed carbon layer has been fabricated through a facile solid-state method and its storage performance in SIBs and LIBs has been reported first. The Cr2P2O7@C delivers 238 mA h g-1 and 717 mA h g-1 at 0.05 A g-1 in SIBs and LIBs, respectively. A capacity of 194 mA h g-1 is achieved in SIBs after 300 cycles at 0.1 A g-1 with a high capacity retention of 92.4%. When tested in LIBs, 351 mA h g-1 is maintained after 600 cycles at 0.1 A g-1. The carbon coating layer improves the conductivity and reduces the side reaction during the electrochemical process, and hence improves the rate performance and enhances the cyclic stability.

Enhancement of Electrochemical Performance of LiFePO4@C by Ga Coating

LiFePO₄ (LFP) is one of the cathode materials widely used in lithium ion batteries at present, but its electronic conductivity is still unsatisfactory, which will affect its electrochemical performance. Ga-coated LiFePO₄@C (LFP@C) samples were prepared by a hydrothermal method and ultrasonic dispersion technology. Ga has good electrical conductivity and can rapidly conduct electrons within the LFP cathode material under the synergistic effect with C coating, thus improving the dynamic performance of the LFP cathode material. The experimental results show that LFP@C/Ga samples exhibit good electrochemical performance. Compared with the pristine LFP@C, the 1.0 wt % Ga-coated LFP@C cathode exhibits excellent discharge capacity and cycle stability. The former shows a discharge capacity of 152.6 mA h g^-1 at 1 C after 100 cycles and a discharge capacity retention rate of 98.77%, while pristine LFP@C shows only a discharge capacity of 114.5 mA h g^-1 and a capacity retention rate of 95.84% after 100 cycles at 1 C current density.

Nitrogen-doped Carbon with Modulated Surface Chemistry and Porous Structure by a Stepwise Biomass Activation Process towards Enhanced Electrochemical Lithium-Ion Storage

Controllable conversion of biomass to value-added carbon materials is attractive towards a wide variety of potential applications. Herein, hydrothermal treatment and KOH activation are successively employed to treat the cheap and abundant camellia oleifera shell as a new carbon raw material. It is shown that this stepwise activation process allows the production of porous nitrogen-doped carbon with optimized surface chemistry and porous structure compared to the counterparts prepared by a single activation procedure. Benefiting from the modulated porous structure, the as-produced porous nitrogen-doped carbon electrode delivered a high reversible capacity of 1080 mAh g⁻¹ at a current density of 100 mA g⁻¹, which is 3.3 and 5.8 times as high as that of the carbon materials prepared by bare hydrothermal treatment or KOH activation, respectively. Moreover, the optimized surface composition of the porous nitrogen-doped carbon endows it with a highest initial Coulombic efficiency among the three samples, showing great potentials for practical applications. This work is expected to pave a new avenue to upgrade biomass to carbon materials with tunable surface properties and microstructures for target applications.

Electrode Materials with a Crater-Type Morphology Prepared by Electrospraying for High-Performance Lithium-Ion Batteries

Rechargeable lithium-ion batteries with good electrochemical properties require nanostructured electrode materials, which are usually prepared through complex synthesis processes. Herein, a new facile method is reported for the synthesis of high-performance electrode materials with a crater-like morphology through repulsion between positive charges. The produced electrode material does not possess a nanostructure. However, it is capable of rapidly transferring lithium ions and electrons owing to the large contact area with electrolyte and the high concentration sp² -hybridized carbon coating. LiFePO₄ and LiNi_1/3 Co_1/3 Mn_1/3 O₂ electrodes prepared by this process achieved high discharge capacities of 165.7 and 199.9 mAh g^-1 at 0.1 C, with excellent rate capability of 127.5 and 162.6 mAh g^-1 at 10 C, respectively. Although the crater-type materials might decrease the electrode tap density, they facilitate better electrochemical properties such as high capacity, high power, and fast charging. Furthermore, this new method can be applied trough a sol-gel process for the synthesis of electrode materials to improve their electrochemical characteristics.