Facile synthesis of phosphorus-doped carbon under tuned temperature with high lithium and sodium anodic performances

Restraining the shuttle effect of polyiodides and modulating the deposition of zinc ions to enhance the cycle lifespan of aqueous Zn-I2 batteries

The boom of aqueous Zn-based energy storage devices, such as zinc-iodine (Zn-I2) batteries, is quite suitable for safe and sustainable energy storage technologies. However, in rechargeable aqueous Zn-I2 batteries, the shuttle phenomenon of polyiodide ions usually leads to irreversible capacity loss resulting from both the iodine cathode and the zinc anode, and thus impinges on the cycle lifespan of the battery. Herein, a nontoxic, biocompatible, and economical polymer of polyvinyl alcohol (PVA) is exploited as an electrolyte additive. Based on comprehensive analysis and computational results, it is evident that the PVA additive, owing to its specific interaction with polyiodide ions and lower binding energy, can effectively suppress the migration of polyiodide ions towards the zinc anode surface, thereby mitigating adverse reactions between polyiodide ions and zinc. Simultaneously, the hydrogen bond network of water molecules is disrupted due to the abundant hydroxyl groups within the PVA additive, leading to a decrease in water activity and mitigating zinc corrosion. Further, because of the preferential adsorption of PVA on the zinc anode surface, the deposition environment for zinc ions is adjusted and its nucleation overpotential increases, which is favorable for the dense and uniform deposition of zinc ions, thus ensuring the improvement of the performance of the Zn-I2 battery. This investigation has inspired the development of a user-friendly and high-performance Zn-I2 battery.

Boosting Thermal and Mechanical Properties: Achieving High-Safety Separator Chemically Bonded with Nano TiN Particles for High Performance Lithium-Ion Batteries

Currently, the commercial separator (Celgard2500) of lithium-ion batteries (LIBs) suffers from poor electrolyte affinity, mechanical property and thermal stability, which seriously affect the electrochemical performances and safety of LIBs. Here, the composite separators named PVDF-HFP/TiN for high-safety LIBs are synthesized. The integration of PVDF-HFP and TiN forms porous structure with a uniform and rich organic framework. TiN significantly improves the adsorption between PVDF-HFP and electrolyte, causing a higher electrolyte absorption rate (192%). Meanwhile, XPS results further demonstrate the tight link between PVDF-HFP and TiN due to the existence of TiF bond in PVDF-HFP/TiN, resulting in a strong impediment for the puncture of lithium dendrites as a result of the improved mechanical strengths. And PVDF-HFP/TiN can effectively suppress the growth of lithium dendrites by means of uniform lithium flux. In addition, the excellent heat resistance of TiN improves the thermal stability of PVDF-HFP/TiN. As a result, the LiFePO₄ ||Li cells assembled PVDF-HFP/TiN-12 exhibit excellent specific capacity, rate performance, and capacity retention rate. Even the high specific capacity of 153 mAh g^-1 can be obtained at the high temperature of 80 °C. Meaningfully, a reliable modification strategy for the preparation of separators with high safety and electrochemical performance in LIBs is provided.

Utilizing the cross-linked effect and reconstruction strategy of phytic acid to build Fe-Co-Ni trimetallic amorphous carbon-matrix compounds as efficient oxygen evolution catalyst

Developing low-cost electrocatalysts with excellent activity is significant for accelerating the slow oxygen evolution reaction (OER). In this work, an effective electrocatalyst is prepared via the cross-linked effect and reconstruction strategy based on inexpensive transition metals (Fe, Co, and Ni) and phytic acid (PA). The feasibility of utilizing the cross-linked effect and reconstruction strategy is due to that PA molecules with strongly electronegative phosphoric acid groups possess a great deal of complexing sites, which can facilitate the formation of large cross-linked network by randomly complexing Fe, Co and Ni ions. And the carboatomic rings in PA molecules will reconstructed as carbon-matrix when PA molecules decompose. The above structural evolution of large cross-linked network and reconstructing process is rigorously analyzed through the characterization methods such as XPS. These analysis results indicate that FeCoNi-PA-300 possesses a high degree of amorphization, an abundant nanoporous structure, and a small nanoparticle size, resulting in a large electrochemically active area. Consequently, FeCoNi-PA-300 just needs low overpotentials of about 271 mV and 286 mV to obtain the current densities of 50 and 100 mA cm-2, respectively. Meaningfully, this synthetic method is a general strategy to meliorate the OER activity and electrical conductivity of other catalysts.

Nitrogen/oxygen codoped hierarchical porous Carbons/Selenium cathode with excellent lithium and sodium storage behavior

A nitrogen/oxygen codoped carbon derived from sweet potato (SPC) with interconnected micro-mesopores is applied to encapsulate selenium composite (SPC/Se) with a high Se loading (74.3%). As a cathode for advanced Li-Se and Na-Se batteries, the SPC/Se exhibits superior electrochemical behavior in low-cost carbonate electrolyte. Including the hierarchically porous structure of SPC and the chemical bonding between Se and carbon, the strong binding energy between SPC and Li₂Se/Na₂Se is also proved by DFT method, which results in the effective mitigation of shuttle reaction and volume change for SPC/Se cathode. For Li-Se batteries, the SPC/Se composite shows the initial specific charge capacity of 668 mAh g^-1 with a high initial coulombic efficiency of 78%, and maintains a stable reversible capacity of 587 mAh g^-1 after 1000 cycles with a weak capacity decay of 0.082% at 0.2C. It still retains a reversible specific capacity of 375 mAh g^-1 even at 20C. For Na-Se battery, the SPC/Se composite displays the initial specific charge capacity of 671 mAh g^-1 at 0.2C and maintains a reversible specific capacity of 412 mAh g^-1 after 500 cycles with a capacity retention of 61.4%. When the current density increases to 20C, it still delivers a high reversible specific capacity of 420 mAh g^-1. Finally, the transformation mechanism of Se molecule is illustrated detailedly in (de)lithi/sodiation process.

Synthesis and electrochemical study of phosphorus-doped porous carbon for supercapacitor applications

In the present investigation, we report the incorporation of phosphorous (P) atoms in the activated carbon and study its effect on the electrochemical performance. Porous carbon is synthesized by the chemical activation method from a bioresource and then pretreated with nitric acid. Phosphorus atoms were doped by the simple chemical method. The obtained phosphorous-doped nano-materials show an appreciable change of porosity and creation of a more wide range of meso- and macropores, and this affects their adsorption and electrochemical performance. The electrochemical study shows that doped carbon obtained at 850 °C (ACtP-850) delivers the maximum specific capacitance (328 Fg−1) in neutral aqueous electrolyte (1 M Na2SO4). The doped carbon material not only exhibits good cycling performance but also the highest specific energy of 29 Wh kg−1 corresponding to a specific power of 646 W kg−1. The improved capacitive performance of phosphorous-doped porous carbon material proposes its use in energy storage applications.