Facile Synthesis and Electrochemical Performance of LiFePO4/C Composites Using Fe–P Waste Slag

Enhanced Electrochemical Performance and Safety of Silicon by a Negative Thermal Expansion Material of ZrW2O8

Silicon (Si) faces big challenges in serious volume changes for applications in spite of its high theoretical capacity. Herein, a novel and facile method was proposed to decrease the volume change by simultaneously in situ absorbing the generated heat of only Si using a negative thermal expansion (NTE) material of ZrW₂O₈. The Si modified with 2 wt % of ZrW₂O₈ exhibits excellent structural integrity, electrochemical performance, and safety under various conditions, especially at elevated temperatures. Its reversible capacities can remain 1187.2 mA h g^-1 after 50 cycles and 643.8 mA h g^-1 after 100 cycles at 2 A g^-1 (∼199 and ∼190% higher than that of Si, respectively) at 25 °C. In addition, 930.6 mA h g^-1 is maintained after 50 cycles at 60 °C (∼219% higher than that of Si). As current densities increase to 2 and 4 A g^-1, the values still remain 1389.4 and 757.5 mA h g^-1, respectively, much higher than that of Si. Furthermore, the strain of Si is reduced by 37.2% using ZrW₂O₈ at 60 °C. Various products were analyzed, and the possible enhanced mechanism was discussed using multiple techniques. These findings exhibit significant potential for the improvement of energy materials using NTE materials by combining thermal effects and volume changes as well as the improved interface behavior.

Recycling Iron-Containing Sludges from the Electroflocculation of Printing and Dyeing Wastewater into Anode Materials for Lithium-Ion Batteries

Iron-containing sludges (DW/Fe) were prepared by the electroflocculation of industrial printing and dyeing wastewater (DW). To investigate the formation process and the properties of the DW/Fe sludges and their application in anode materials in Li-ion batteries, the DW/Fe sludges were compared to three other sludges (MB/Fe, RB/Fe, Ta/Fe) prepared from model solutions that contained either methyl blue (MB), rhodamine B (RB), or tartrazine (Ta). The DW/Fe sludges were calcined at 500 °C under N₂ to form iron oxide/carbon composite C-DW/Fe. The composition and structure of the sludges and the C-DW/Fe composite were analyzed by using FTIR spectroscopy, XRD, thermogravimetric analysis, SEM, TEM, and X-ray photoelectron spectroscopy, and their performances as anodes of Li-ion batteries were studied by adding different proportions of conductive agent (super P® conductive carbon black). Our results show that the sludges are a complex mixture of Fe₃ O₄ and organic matter. The specific capacity and stability can be improved during the charge-discharge test by increasing the amount of carbon black. Importantly, this improvement is more pronounced on DW/Fe that does not require high-temperature carbonization, which means that the sludges cannot only protect the environment and avoid the waste of resources but also can be used directly and widely in decentralized energy storage devices.

A Novel Strategy for the Synthesis of Fe3(PO4)2 Using Fe-P Waste Slag and CO2 Followed by Its Use as the Precursor for LiFePO4 Preparation

A novel method whose starting materials was Fe-P waste slag and CO2 using a closed-loop carbon and energy cycle to synthesize LiFePO4/C materials was proposed recently. In the first step, Fe-P slag was calcinated in a CO2 atmosphere to manufacture Fe3(PO4)2, in which the solid products were tested by XRD (X-ray diffraction) analysis and the gaseous products were analyzed by the gas detection method. In the second step, as-synthesized Fe3(PO4)2 was further used as the Fe and P source to manufacture LiFePO4/C materials. Also, the influence of the preparation conditions of Fe3(PO4)2, including calcination time and calcination temperature, on the energy storage properties of as-obtained LiFePO4/C was investigated. It was found that the LiFePO4/C materials, which was synthesized from Fe3(PO4)2 obtained by calcining Fe-P waste slag at 800 °C for 10 h in CO2, exhibited a higher capacity, better reversibility, and lower polarization than other samples. The discharge capacity of as-obtained LiFePO4/C can reach 145 mAh/g at 0.1 C current rate. This work puts forward an environment-friendly method of manufacturing LiFePO4/C cathode materials, which has a closed-loop carbon and energy cycle.

Influence of charge status on the stress safety properties of Li(Ni1/3Co1/3Mn1/3)O2 cells

The stresses in lithium cells are real-time monitored without destruction, and the relationship between stress and electrochemical performance is discussed.