Borong Wu

Recovery of cobalt and lithium from spent lithium ion batteries using organic citric acid as leachant

In this work, a hydrometallurgical process based on leaching is applied to recover cobalt and lithium from spent lithium ion batteries (LIBs). Citric acid and hydrogen peroxide are introduced as leaching reagents and the leaching of cobalt and lithium with a solution containing C(6)H(8)O(7) x H(2)O is investigated. When both C(6)H(8)O(7) x H(2)O and H(2)O(2) are used an effective recovery of Li and Co as their respective citrates is possible. The leachate is characterized by scanning electron micrography (SEM) and X-ray diffraction (XRD). The proposed procedure includes the mechanical separation of metal-containing particles and a chemical leaching process. Conditions for achieving a recovery of more than 90% Co and nearly 100% Li are achieved experimentally by varying the concentrations of leachant, time and temperature of the reaction as well as the starting solid-to-liquid ratio. Leaching with 1.25 M citric acid, 1.0 vol.% hydrogen peroxide and a S:L of 20 g L(-1) with agitation at 300 rpm in a batch extractor results in a highly efficient recovery of the metals within 30 min of the processing time at 90 degrees C. This hydrometallurgical process is found to be simple, environmentally friendly and adequate for the recovery of valuable metals from spent LIBs.

Enhanced Electrochemical Performance of ZnO-Loaded/Porous Carbon Composite as Anode Materials for Lithium Ion Batteries

ZnO-loaded/porous carbon (PC) composites with different ZnO loading amounts are first synthesized via a facile solvothermal method and evaluated for anode materials of lithium ion batteries. The architecture and the electrochemical performance of the as-prepared composites are investigated through structure characterization and galvanostatic charge/discharge test. The ZnO-loaded/PC composites possess a rich porous structure with well-distributed ZnO particles (size range: 30-100 nm) in the PC host. The one with 54 wt % ZnO loading contents exhibits a high reversible capacity of 653.7 mA h g(-1) after 100 cycles. In particular, a capacity of 496.8 mA h g(-1) can be reversibly obtained when cycled at 1000 mA g(-1). The superior lithium storage properties of the composite may be attributed to its nanoporous structure together with an interconnected network. The modified interfacial reaction kinetics of the composite promotes the intercalation/deintercalation of lithium ions and the charge transfer on the electrode. As a result, the enhanced capacity of the composite electrode is achieved, as well as its high rate capability.

Sphere-shaped hierarchical cathode with enhanced growth of nanocrystal planes for high-rate and cycling-stable li-ion batteries.

High-energy and high-power Li-ion batteries have been intensively pursued as power sources in electronic vehicles and renewable energy storage systems in smart grids. With this purpose, developing high-performance cathode materials is urgently needed. Here we report an easy and versatile strategy to fabricate high-rate and cycling-stable hierarchical sphered cathode Li(1.2)Ni(0.13)Mn(0.54)Co(0.13)O2, by using an ionic interfusion method. The sphere-shaped hierarchical cathode is assembled with primary nanoplates with enhanced growth of nanocrystal planes in favor of Li(+) intercalation/deintercalation, such as (010), (100), and (110) planes. This material with such unique structural features exhibits outstanding rate capability, cyclability, and high discharge capacities, achieving around 70% (175 mAh g(-1)) of the capacity at 0.1 C rate within about 2.1 min of ultrafast charging. Such cathode is feasible to construct high-energy and high-power Li-ion batteries.

New Synthesis of a Foamlike Fe3O4/C Composite via a Self-Expanding Process and Its Electrochemical Performance as Anode Material for Lithium-Ion Batteries

A novel foamlike Fe3O4/C composite is prepared via a sol-gel type method with gelatin as the carbon source and ferric nitrate as the iron source, following a postannealing treatment. Its lithium storage properties as anode material for a lithium-ion battery are thoroughly investigated in this work. With the interaction between ferric nitrate and gelatin, the foamlike architecture is attained through a unique self-expanding process. The Fe3O4/C composite possesses abundant porous structure along with highly dispersed Fe3O4 nanocrystal embedment in the carbon matrix. In the constructed architecture, the 3D porous network property ensures electrolyte accessibility; meanwhile, nanosized Fe3O4 promotes lithiation/delithiation, owing to numerous active sites, large electrolyte contact area, and a short lithium ion diffusion path. As a result, this Fe3O4/C composite electrode demonstrates an excellent cycling stability with a reversible capacity of 1008 mA h g(-1) over 400 cycles at 0.2C (1C = 1000 mA g(-1)), as well as a superior rate performance with reversible capacity of 660 and 580 mA h g(-1) at 3C and 5C, respectively.

Effect of lithium carbonate precipitates on the electrochemical cycling stability of LiCoO2 cathodes at a high voltage

An electrolyte (LiPF6–EC/PC/DEC) containing a lithium carbonate (Li2CO3) additive is used to enable the high cycling stability of a lithium cobalt oxide (LiCoO2) cathode which is charged to 4.5 V for a higher capacity. A capacity as high as 162.8 mA h g−1 (1 C) is maintained after 116 cycles, which is twice as high as the capacity of 88.5 mA h g−1 which was achieved in the Li2CO3 free instance. The interface properties of the electrode are investigated by cyclic voltammetry, electrochemical impedance spectroscopy and X-ray photoelectron spectroscopy. It is found that the solid electrolyte interphase (SEI) film tends to be thin and steady, and that the electrolyte decomposition is suppressed with the addition of Li2CO3. A possible mechanism is proposed according to the DFT calculation. The results indicate that the Co4+…CO32− coordination may decrease the oxidizability of Co4+ on the electrode surface so that the electrolyte decomposition could be suppressed.

Enhanced electrochemical performance of LiFePO4 cathode with the addition of fluoroethylene carbonate in electrolyte

The effect of the fluoroethylene carbonate (FEC) addition in electrolyte on LiFePO4 cathode performance was investigated in low-temperature electrolyte LiPF6/EC/PC/EMC (0.14/0.18/0.68). Cyclic voltammetry, electrochemical impedance spectroscopy, and charge/discharge tests were conducted in this work. In the presence of FEC, the polarization of LiFePO4 electrode decreased both at room and low temperatures. Meanwhile, the exchange current density increased. The rate capability of LiFePO4 electrode was greatly enhanced as well. The morphology of the solid electrolyte interphase (SEI) on LiFePO4 surface was modified with the addition of FEC as confirmed by scanning electron microscopy measurement. A compact film with small impedance was formed on LiFePO4 surface compared to the case of FEC-free. The compositions of the film were analyzed by X-ray photoelectron spectroscopic measurement. The contents of LixPOyFz, LiF, and the carbonate species generated from solvents decomposition were reduced. The modified SEI promoted the migration of lithium ion through the electrode/electrolyte interphase and enhanced the electrochemical performance of the cathode.

Density Functional Theory Research into the Reduction Mechanism for the Solvent/Additive in a Sodium-Ion Battery.

The solid-electrolyte interface (SEI) film in a sodium-ion battery is closely related to capacity fading and cycling stability of the battery. However, there are few studies on the SEI film of sodium-ion batteries and the mechanism of SEI film formation is unclear. The mechanism for the reduction of ethylene carbonate (EC), propylene carbonate (PC), vinylene carbonate (VC), ethylene sulfite (ES), 1,3-propylene sulfite (PS), and fluorinated ethylene carbonate (FEC) is studied by DFT. The reaction activation energies, Gibbs free energies, enthalpies, and structures of the transition states are calculated. It is indicated that VC, ES, and PS additives in the electrolyte are all easier to form organic components in the anode SEI film by one-electron reduction. The priority of one-electron reduction to produce organic SEI components is in the order of VC>PC>EC; two-electron reduction to produce the inorganic Na2 CO3 component is different and follows the order of EC>PC>VC. Two-electron reduction for sulfites ES and PS to form inorganic Na2 SO3 is harder than that of carbonate ester reduction. It is also suggested that the one- and two-electron reductive decomposition pathway for FEC is more feasible to produce inorganic NaF components.

Suppression of lithium dendrite growth by introducing a low reduction potential complex cation in the electrolyte

A low reduction potential complex cation (LRPCC) N-methyl-N-butylpiperidinium was introduced to the LiPF6/EC/DEC electrolyte to investigate its effect on the interface properties of a lithium anode. The reduction of N-methyl-N-butylpiperidinium LRPCC is analyzed by density functional theory (DFT) calculations using the Gaussian 09 package. Lithium dendrites and fractured metal Li are examined by scanning electron microscopy (SEM) and X-ray diffraction (XRD) respectively. The solid electrolyte interface (SEI) film of the metal Li surface is analyzed by X-ray photoelectron spectroscopy (XPS). It is indicated that the LUMO energy level of the LRPCC is higher than lithium ions one. It exhibits a better electrostatic shield around the initial protuberances, reducing the growth of the Li dendrites. The shield effect could play a role even at a higher current density and a wider electrostatic repulsion shield owing to the stronger reduction resistance ability and the higher concentration of the LRPCC. It is demonstrated that there is an interaction among Li dendrites, dead Li and the SEI film. It is shown that the electrolyte containing the complex ion can effectively enhance the coulombic efficiency of Li deposition as well.

Lithium–air and lithium–copper batteries based on a polymer stabilized interface between two immiscible electrolytic solutions (ITIES)

We propose and demonstrate the direct application of immiscible aqueous/organic interfaces in lithium–air and lithium–copper batteries. Therefore, the two half-reactions are separated in their respectively favourable electrolytic environments without using any other membranes. In order to prevent water and oxygen from interrupting the reaction in organic phases, we add poly(methyl methacrylate) (PMMA) to propylene carbonate (PC) and investigate its concentration effects using Pt ultramicroelectrodes (UMEs). Pt UMEs provide us the sensitive measure of water contamination as well as the diffusion property of oxygen in the polymer electrolytes. By studying the discharge profiles under various electrolytic conditions, we demonstrate that these batteries are of longer discharge time and higher specific capacity when the polymer electrolyte contains about 10 to 20% of PMMA.

Electrochemical performance of a nickel-rich LiNi0.6Co0.2Mn0.2O2 cathode material for lithium-ion batteries under different cut-off voltages

A spherical-like Ni0.6Co0.2Mn0.2(OH)2 precursor was tuned homogeneously to synthesize LiNi0.6Co0.2Mn0.2O2 as a cathode material for lithium-ion batteries. The effects of calcination temperature on the crystal structure, morphology, and the electrochemical performance of the as-prepared LiNi0.6Co0.2Mn0.2O2 were investigated in detail. The as-prepared material was characterized by X-ray diffraction, scanning electron microscopy, laser particle size analysis, charge–discharge tests, and cyclic voltammetry measurements. The results show that the spherical-like LiNi0.6Co0.2Mn0.2O2 material obtained by calcination at 900°C displayed the most significant layered structure among samples calcined at various temperatures, with a particle size of approximately 10 μm. It delivered an initial discharge capacity of 189.2 mAh•g−1 at 0.2C with a capacity retention of 94.0% after 100 cycles between 2.7 and 4.3 V. The as-prepared cathode material also exhibited good rate performance, with a discharge capacity of 119.6 mAh•g−1 at 5C. Furthermore, within the cut-off voltage ranges from 2.7 to 4.3, 4.4, and 4.5 V, the initial discharge capacities of the calcined samples were 170.7, 180.9, and 192.8 mAh•g−1, respectively, at a rate of 1C. The corresponding retentions were 86.8%, 80.3%, and 74.4% after 200 cycles, respectively.