Deying Mu

Optimized Li and Fe recovery from spent lithium-ion batteries via a solution-precipitation method

A new process is optimized and presented for the recovery and regeneration of LiFePO4 from spent lithium-ion batteries (LIBs). The recycling process reduces the cost and secondary pollution caused by complicated separation and purification processes in spent LIB recycling. Amorphous FePO4·2H2O was recovered by a dissolution-precipitation method from spent LiFePO4 batteries. The effects of different surfactants (i.e. CTAB, SDS and PEG), which were added to the solution on the recovered FePO4·2H2O, were investigated. Li2CO3 was precipitated by adding Na2CO3 to the filtrate. Then the LiFePO4/C material was synthesized by a carbon thermal reduction method using recycled FePO4·2H2O and Li2CO3 as the Fe, P, and Li sources. The as-prepared LiFePO4/C shows comparable electrochemical performance to that of commercial equivalents.

Supercritical CO2 extraction of organic carbonate-based electrolytes of lithium-ion batteries

Supercritical fluid extraction (SFE) was applied to reclaim organic carbonate-based electrolytes of spent lithium-ion batteries. To optimize the SFE operational conditions, the response surface methodology was adopted. The parameters studied were as follow: pressure, ranging from 15 to 35 MPa; temperature, between 40 °C and 50 °C and static extraction time, within 45 to 75 min. The optimal conditions for extraction yield were 23 MPa, 40 °C and was dynamically extracted for 45 min. Extracts were collected at a constant flow rate of 4.0 L min−1. Under these conditions, the extraction yield was 85.07 ± 0.36%, which matched with the predicted value. Furthermore, the components of the extracts were systematically characterized and analyzed by using FT-IR, GC-MS and ICP-OES, and the effect of SFE on the electrolyte reclamation was evaluated. The results suggest that the SFE is an effective method for recovery of organic carbonate-based electrolytes from spent lithium-ion batteries, to prevent environmental pollution and resource waste.

The impact of aluminum impurity on the regenerated lithium nickel cobalt manganese oxide cathode materials from spent LIBs

In this paper, an effective recycling process from spent LIBs has been developed. The aluminum residual commonly exists in hydrometallurgy, and also aluminum is considered as a resultant additive in LIB modification, therefore, the tolerability of aluminum was studied in this work. Li[(Ni1/3Co1/3Mn1/3)1−xAlx]O2 (0.01 ≤ x ≤ 0.05) cathode materials were regenerated from spent ternary LIBs. X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and electrochemical measurements were carried out to characterize the performances of all of the samples. XRD and XPS results indicate that Mn and Ni are possibly replaced by Al. When x ≤ 0.03, the initial discharge capacity is up to 170 mA h g−1 at 0.05C between 2.5 and 4.5 V, and more than 100 mA h g−1 at 2C. The results showed that the existence of aluminum of up to x = 0.03 has no significant impact on the cathode materials of Li[(Ni1/3Co1/3Mn1/3)1−xAlx]O2, and the content surpasses the conventional limitations.

Enhancing coulombic efficiency and rate capability of high capacity lithium excess layered oxide cathode material by electrocatalysis of nanogold

A Lithium-rich cathode material Li1.2Mn0.56Ni0.16Co0.08O2 modified with nanogold (Au@LMNCO) for lithium-ion (Li-ion) batteries was prepared using co-precipitation, solid-state reaction and surface treatment techniques. Au@LMNCO was prepared by thermally spraying gold on the surface of the lithium-rich cathode material (LMNCO). X-ray diffraction (XRD) and energy dispersive spectrometry (EDS) results indicate that Au was successfully integrated into the surface of LMNCO. The cyclic voltammogram of Au@LMNCO shows a significant reduction in the reaction overpotential compared to that of LMNCO, which was a result of the nanogold formation. The stable reversible capacity of the Au@LMNCO electrode was 249 mA h g−1, and it could be retained at 244 mA h g−1 (98% retention) after 100 cycles at 0.5C. The coulombic efficiencies were over 98% except for the first five cycles. Moreover, Au@LMNCO also exhibited excellent rate capability. Even at a 5.0C rate, its discharge capacity was about 190 mA h g−1. The superior electrochemical performance can be attributed to its unique nanoplate characteristics, its structural stability, and the electrocatalytic activity of nanogold.

Magnesium/chloride co-doping of lithium vanadium phosphate cathodes for enhanced stable lifetime in lithium-ion batteries

A Mg and Cl co-doped Li3V2(PO4)3/C (LVMPCl/C) material has been synthesized via a solid state method. The effects of Mg and Cl co-doping on the electrochemical properties, structure and morphology of Li3V2(PO4)3 are investigated. Detailed analysis of the XRD patterns suggests that Mg and Cl atoms partly occupy V and O sites in the crystal structure of Li3V2(PO4)3, respectively. The valence states of Mg and Cl elements are investigated using X-ray photoelectron spectroscopy (XPS). Combining XRD patterns with 31P NMR spectra, it is further demonstrated that doped Mg and Cl atoms affect the local electronic structure of P atoms in Li3V2(PO4)3. According to the results of electrochemical performance, LVMPCl/C exhibits excellent discharge capacity as high as 129.1 mA h g−1 at 0.1C. In addition, the capacity retention of LVMPCl/C is almost 100% after 100 cycles at 3.0–4.3 V. Impedance spectroscopy (EIS) and cyclic voltammetry (CV) curves illustrate the lower charge transfer resistance and much more decreased polarization of LVMPCl/C than the pristine one. The excellent electrochemical performance of LVMPCl/C can be attributed to its larger Li ion diffusion channels, which is ascribed to the increased unit-cell volumes, smaller particle sizes and higher electronic conductivity.

Cycling stability of the Li3(V0.9Mg0.1)2(PO4)3/C cathode with an increase in the charge cut-off voltage

The problem of the decrease in cycling stability of Li3(V0.9Mg0.1)2(PO4)3/C limits its practical application in a broad electrochemical window. However, the cause of the cycling stability decrease in Li3(V0.9Mg0.1)2(PO4)3/C has not been studied in previous research. In this paper, to illustrate the cause of the decreased cycling stability of the Li3(V0.9Mg0.1)2(PO4)3/C samples, we investigated the crystal structure changes in the cathode materials in a broad electrochemical window. The structure of the Li3(V0.9Mg0.1)2(PO4)3/C samples was analyzed by XRD refinement, SEM and TEM. The results indicate that the higher the charge cut-off voltage is, the worse the cycling stability of the sample is. It was concluded that the cell volume of the Li3(V0.9Mg0.1)2(PO4)3/C samples expands irreversibly after cycling in different voltage ranges, and the bond lengths of Li(3)–O become longer while those of Li(2)–O and Li(1)–O become shorter. This means that the bond energy of the Li(3) ion increased, and the bond energy of the Li(1) and Li(2) ions decreased. This is not beneficial to the intercalation/deintercalation of Li ions with the increase in the charge cut-off voltage. The TEM test shows that the carbon layer of the samples is destroyed with the increase in the charge cut-off voltage. It is reasonably inferred that the crystal structure change in the Li3(V0.9Mg0.1)2(PO4)3/C samples causes poor cycling stability with the increase in the charge cut-off voltage.

Transcritical CO2 extraction of electrolytes for lithium-ion batteries: optimization of the recycling process and quality–quantity variation

Electrolyte solutions have a vital function in lithium-ion batteries. In consideration of their toxic and harmful characteristics and widespread applications in the EVs, the treatment or recovery of the electrolyte is of concern and accurate analysis is needed for the resource and environment benefits. In this work, we present a highly-selective electrolyte recovery method—transcritical CO2 extraction—that combined the extraction and separation processes together. The use of response surface methodology helps in obtaining a simplified and optimized extraction protocol at room temperature and low pressure saving time and reagents. In order to evaluate these extracts, various techniques like GC-MS, GC-FID, FITR and NMR were applied. The GC-FID quantitative analysis and calculation formula may help with realizing the oriented control of the extraction process, and hexafluorophosphate (PF6−), fluoride (F−) and difluorophosphate (PO2F2−) detected by both 19F and 31P spectra imply the degradation pathway.