Performance of LiNi1/3Co1/3Mn1/3O2 prepared from spent lithium-ion batteries by a carbonate co-precipitation method

Spherical LiNi_1/3Co_1/3Mn_1/3O₂ cathode particles were resynthesized by a carbonate co-precipitation method using spent lithium-ion batteries (LIBs) as a raw material. The physical characteristics of the Ni_1/3Co_1/3Mn_1/3CO₃ precursor, the (Ni_1/3Co_1/3Mn_1/3)₃O₄ intermediate, and the regenerated LiNi_1/3Co_1/3Mn_1/3O₂ cathode material were investigated by laser particle-size analysis, scanning electron microscopy–energy-dispersive spectroscopy (SEM-EDS), thermogravimetry–differential scanning calorimetry (TG-DSC), X-ray diffraction (XRD), inductively coupled plasma–atomic emission spectroscopy (ICP-AES), and X-ray photoelectron spectroscopy (XPS). The electrochemical performance of the regenerated LiNi_1/3Co_1/3Mn_1/3O₂ was studied by continuous charge–discharge cycling and cyclic voltammetry. The results indicate that the regenerated Ni_1/3Co_1/3Mn_1/3CO₃ precursor comprises uniform spherical particles with a narrow particle-size distribution. The regenerated LiNi_1/3Co_1/3Mn_1/3O₂ comprises spherical particles similar to those of the Ni_1/3Co_1/3Mn_1/3CO₃ precursor, but with a narrower particle-size distribution. Moreover, it has a well-ordered layered structure and a low degree of cation mixing. The regenerated LiNi_1/3Co_1/3Mn_1/3O₂ shows an initial discharge capacity of 163.5 mA h g^?1 at 0.1 C, between 2.7 and 4.3 V; the discharge capacity at 1 C is 135.1 mA h g^?1, and the capacity retention ratio is 94.1% after 50 cycles. Even at the high rate of 5 C, LiNi_1/3Co_1/3Mn_1/3O₂ delivers the high capacity of 112.6 mA h g^?1. These results demonstrate that the electrochemical performance of the regenerated LiNi_1/3Co_1/3Mn_1/3O₂ is comparable to that of a cathode synthesized from fresh materials by carbonate co-precipitation.     

CeF3-modified LiNi1/3Co1/3Mn1/3O2 cathode material for high-voltage Li-ion batteries

A facile chemical deposition method has been adopted to prepare cerium fluoride (CeF₃) surface modified LiNi_1/3Co_1/3Mn_1/3O₂ as cathode material for lithium-ion batteries. Structure analyses reveal that the surface of LiNi_1/3Co_1/3Mn_1/3O₂ particles is uniformly coated by CeF₃. Electrochemical tests indicate that the optimal CeF₃ content is 1 wt%. The 1 wt% CeF₃-coated LiNi_1/3Co_1/3Mn_1/3O₂ can deliver a discharge capacity of 107.1 mA h g⁻¹ even at 5 C rate, while the pristine does only 57.3 mA h g⁻¹. Compared to the pristine, the 1 wt% CeF₃-coated LiNi_1/3Co_1/3Mn_1/3O₂ exhibits the greatly enhanced capacity and cycling stability in the voltage range of 3.0–4.5 V, which suggests that the CeF₃ coating has the positive effect on the high-voltage application of LiNi_1/3Co_1/3Mn_1/3O₂. According to the analyses from electrochemical impedance spectra, enhanced electrochemical performance is mainly because the stable CeF₃ coating layer can prevent the HF-containing electrolyte from continuously attacking the LiNi_1/3Co_1/3Mn_1/3O₂ cathode and retard the passivating layer growth on the cathode.     

Fine-sized LiNi0.8Co0.15Mn0.05O2 cathode particles prepared by spray pyrolysis from the polymeric precursor solutions

Fine-sized LiNi_0.8Co_0.15Mn_0.05O₂ cathode particles with high discharge capacities and good cycle properties were prepared by spray pyrolysis from the polymeric precursor solutions. The cathode particles obtained from the spray solution without polymeric precursors had irregular morphology and hardly aggregated morphology. On the other hand, the cathode particles obtained from the spray solution with citric acid and ethylene glycol had fine size and regular morphologies. The cathode particles obtained from the spray solution containing adequate amounts of citric acid and ethylene glycol had several hundreds nanometer and narrow size distribution. The maximum discharge capacity of the cathode particles was 218 mAh/g when the excess of lithium component added to the spray solution was 6 mol% of the stoichiometric amount to obtain the LiNi_0.8Co_0.15Mn_0.05O₂ particles. The discharge capacities of the fine-sized LiNi_0.8Co_0.15Mn_0.05O₂ particles dropped from 218 to 213 mAh/g by the 50th cycle at a current density of 0.1 C.     

Synthesis and structural characterization of layered Li[Ni1/3Co1/3Mn1/3]O2 cathode materials by ultrasonic spray pyrolysis method

The layered Li[Ni_1/3Co_1/3Mn_1/3]O₂ materials were synthesized by a spray pyrolysis method using citric acid as a polymeric agent. The Li[Ni_1/3Co_1/3Mn_1/3]O₂ powders were characterized by means of X-ray diffraction (XRD), charge/discharge cycling, cyclic voltammetry, and high-resolution transmission electron microscopy (TEM). The discharge capacity increases linearly with the increase of the upper cut-off voltage limit. TEM analysis showed that particles in the as-prepared powder possessed a polycrystalline structure. During cycling, the particle structure is mostly preserved although some surface grains on the polycrystalline particle became separated and transformed to the spinel phase.     

Synthesis of LiNi1/3Mn1/3Co1/3O2@graphene for lithium-ion batteries via self-assembled polyelectrolyte layers

LiNi_1/3Co_1/3Mn_1/3O₂ cathode coated with a thin layer of graphene (~8 nm) is successfully synthesized by self-assembly and pyrolysis of polyelectrolyte layers on the surface of NMC particles. The graphene coated NMCs still possess a layered structure with good crystallinity and demonstrate a superior electrochemical performance (e.g., rate capability and cycling stability). The best graphene coated NMC cathode is prepared at a calcination temperature of 800 °C, exhibiting a capacity retention of ~90% vs. 78% for pristine NMC @ cycle 100 and 1 C rate. The improvement in cycling performance is further enlarged after 500 cycles (74% vs. 51%). This can be attributed to the dual functions of graphene coating in enhancing electronic conductivity and protecting NMC surface from the contact with electrolyte during the electrochemical reaction.     

Synthetic optimization of spherical Li[Ni1/3Mn1/3Co1/3]O2 prepared by a carbonate co-precipitation method

A carbonate co-precipitation method was employed to prepare spherical Li[Ni_1/3Co_1/3Mn_1/3]O₂ cathode material. The precursor, [Ni_1/3Co_1/3Mn_1/3]CO₃, was prepared using ammonia as chelating agent under CO₂ atmosphere. The spherical Li[Ni_1/3Co_1/3Mn_1/3]O₂ was prepared by mixing the precalcined [Ni_1/3Co_1/3Mn_1/3]CO₃ with LiOH followed by high temperature calcination. The preparation conditions such as ammonia concentration, co-precipitation temperature, calcination temperature and Li/[Ni_1/3Co_1/3Mn_1/3] ratio were varied to optimize the physical and electrochemical properties of the prepared Li[Ni_1/3Co_1/3Mn_1/3]O₂. The structural, morphological, and electrochemical properties of the prepared LiNi_1/3Co_1/3Mn_1/3O₂ were characterized by XRD, SEM, and galvanostatic charge-discharge cycling. The optimized material has a spherical particle shape and a well ordered layered structure, and it also has an initial discharge capacity of 162.7 mAh g^− 1 in a voltage range of 2.8-4.3 V and a capacity retention of 94.8% after a hundred cycles. The optimized ammonia concentration, co-precipitation temperature, calcination temperature, and Li/[Ni_1/3Co_1/3Mn_1/3] ratio are 0.3 mol L^− 1, 60 °C, 850 °C, and 1.10, respectively.     

Nano-sized LiNi0.5Mn1.5O4 cathode powders with good electrochemical properties prepared by high temperature flame spray pyrolysis

LiNi_0.5Mn_1.5O₄ cathode powders with a mean particle size of 140 nm are prepared by high-temperature flame spray pyrolysis. Li/LiNi_0.5Mn_1.5O₄ cells show two plateaus at approximately 4.1 and 4.7 V during discharge, irrespective of any excess of the lithium component in the spray solution, although the 4.1 V plateau decreases when the spray solution contained 20% excess lithium. The discharge capacity of the powder prepared from a spray solution with 20% excess lithium decreases from 133 to 126 mAh g^?1 by the 50th cycle at a current density of 0.1 C, which is a capacity retention of 95%.     

Characterization of high tap density Li[Ni1/3Co1/3Mn1/3]O2 cathode material synthesized via hydroxide co-precipitation

Li[Ni_1/3Co_1/3Mn_1/3]O₂ cathode material for lithium ion batteries was prepared by mixing metal hydroxide, (Ni_1/3Co_1/3Mn_1/3)(OH)₂, with 6% excess LiOH followed by calcinations. The (Ni_1/3Co_1/3Mn_1/3)(OH)₂ with secondary particle of about 12 μm was prepared by hydroxide co-precipitation. The tap density of the obtained Li[Ni_1/3Co_1/3Mn_1/3]O₂ powder was 2.56 ± 0.21 g cm⁻³. The powder was characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), particle size distribution (PSD) and galvanostatic charge-discharge cycling. The XRD pattern of Li[Ni_1/3Co_1/3Mn_1/3]O₂ revealed a well ordered hexagonal layered structure with low cation mixing. Secondary particles with size of 13-14 μm and primary particles with size of about 1 μm can be identified from the SEM observations. In the voltage range of 2.8-4.3 V, the initial discharge capacity of the Li[Ni_1/3Co_1/3Mn_1/3]O₂ electrode was 166.6 mAh g⁻¹, and 96.5% of the initial capacity was retained after 50 charge-discharge cycling.     

The effect of AlF3 modification on the physicochemical and electrochemical properties of Li-rich layered oxide

Lithium (Li)-rich layered oxides are considered promising cathode materials for Li-ion batteries because of their favorable properties. Here, we report our recent finding in the novel oxide, aluminum fluoride (AlF₃)-modified Li_1.2Mn_0.54Ni_0.13Co_0.13O₂ (LMNCAF), which was synthesized via a facile, cost-effective and readily scalable solid-state reaction. LMNCAF possess an F and Al co-doped core structure with a LiF nano-coating on its surface which leads to considerably enhancement in the electrochemical performance of the oxide. The initial discharge capacity (at 0.05 C) increased from 212 mA h g⁻¹ for Li_1.2Mn_0.54Ni_0.13Co_0.13O₂ to 291 mA h g⁻¹ for LMNCAF. A much higher discharge capacity of 211 mA h g⁻¹ was obtained for LMNCAF after 99 charge/discharge cycles at 0.2 C compared with that of Li_1.2Mn_0.54Ni_0.13Co_0.13O₂ (160 mA h g⁻¹). Our preliminary results suggest that AlF₃ modification is an effective strategy to tailor the physicochemical and electrochemical properties of Li-rich layered oxides.     

Hydrothermal synthesis of 3D NixCo1−xS2 particles/graphene composite hydrogels for high performance supercapacitors

In this work, three dimensional (3D) Ni_xCo_1−xS₂/graphene composite hydrogels with different Ni contents (denoted as Ni_xCo_1−xS₂/GH (x = 0, 0.31, 0.56, 0.66, 1)) have been synthesized by a simple one-step hydrothermal method and utilized as the active materials of supercapacitors. The as-prepared samples present a 3D interconnected porous network with the pore sizes in the range of several to tens micrometers. Interestingly, the Ni_xCo_1−xS₂ particles are uniformly located on the graphene network and the particle size is evolved from ∼50 nm to ∼1.5 μm with the increase of Ni content. The electrochemical measurements revealed that the specific capacitance, rate capability and cyclability of different Ni_xCo_1−xS₂/GH electrodes are strongly affected by their different Ni content. Among these, the 3D Ni_0.31Co_0.69S₂/GH composite has the highest specific capacitance of 1166 F/g at a current density of 1 A/g. Furthermore, a specific capacitance of 559 F/g can be still maintained at high current density of 20 A/g. After 1000 charge–discharge cycles at 5 A/g, the specific capacitance remains a high value of 755 F/g.     

Nanosized barium ferrite powders prepared by spray pyrolysis from citric acid solution

Highly crystalline nanosized barium ferrite (BaFe₁₂O₁₉) powders were prepared by spray pyrolysis from a spray solution containing a high concentration of the metal components. The precursor powders obtained from the spray solution containing citric acid were amorphous with a porous and hollow structure. Purely crystalline and fine BaFe₁₂O₁₉ powders were obtained after post-treatment between 700 and 1000 °C and subsequent mechanical grinding in an agate mortar. The mean sizes of the powders post-treated at 700 and 1000 °C were 125 and 550 nm, respectively. The specific magnetization of the powders prepared from the spray solution containing citric acid was 57 emu/g.     

Effect of citric acid content on synthesis of LiNi1/3Mn1/3Co1/3O2 and its electrochemical characteristics

LiNi_1/3Mn_1/3Co_1/3O₂ has been synthesized using different citric acid (chelating agent) contents to study the effect on morphology and electrochemical characteristics of the powdered compound synthesized. The citric acid content is expressed as R′ which is the ratio of citric acid to metal ions. The processing with large value of R′ yields the powder having particle size of about 200 nm. X-ray diffraction (XRD) analysis shows the powder has single phase layered rhombohedral structure. First cycle coulombic efficiency of the powder prepared with R′ = 3, is ～93% in the voltage range of 4.6–2.5 V.     

La2O3-coated Li1.2Mn0.54Ni0.13Co0.13O2 as cathode materials with enhanced specific capacity and cycling stability for lithium-ion batteries

Li-rich layered oxides are the most promising cathode candidate for new generation rechargeable lithium-ion batteries. In this work, La₂O₃-coated Li_1.2Mn_0.54Ni_0.13Co_0.13O₂ cathode materials were fabricated via a combined method of sol-gel and wet chemical processes. The structural and morphological characterizations of the materials demonstrate that a thin layer of La₂O₃ is uniformly covered on the surface of Li_1.2Mn_0.54Ni_0.13Co_0.13O₂ particles, and the coating of La₂O₃ has no obvious effect on the crystal structure of Li-rich oxide. The electrochemical performance of La₂O₃-coated Li-rich cathodes including specific capacity, cycling stability and rate capability has been significantly improved with the coating of La₂O₃. The Li_1.2Mn_0.54Ni_0.13Co_0.13O₂ coated with 2.5 wt% La₂O₃ exhibits the highest discharge capacity, improved cycling stability and reduced charge transfer resistance, delivering a large discharge capacity of 276.9 mAh g⁻¹ in the 1st cycle and a high capacity retention of 71% (201.4 mAh g⁻¹) after 100 cycles. The optimal rate capability of the materials is observed at the coating level of 1.5 wt% La₂O₃ such that the material exhibits the highest discharge capacity of 90.2 mAh g⁻¹ at 5 C. The surface coating of La₂O₃ can effectively facilitate Li⁺ interfacial diffusion, reduce the structural change and secondary reactions between cathode materials and electrolyte during the charge-discharge process, and thus induce the great enhancement in the electrochemical properties of the Li_1.2Mn_0.54Ni_0.13Co_0.13O₂ materials.     

Hydrothermal synthesis of layered Li[Ni1/3Co1/3Mn1/3]O2 as positive electrode material for lithium secondary battery

In attempts to prepare layered Li[Ni_1/3Co_1/3Mn_1/3]O₂, hydrothermal method was employed. The hydrothermal precursor, [Ni_1/3Co_1/3Mn_1/3](OH)₂, was synthesized via a coprecipitation route. The sphere-shaped powder precursor was hydrothermally reacted with LiOH aqueous solution at 170 °C for 4 days in autoclave. From X-ray diffraction and scanning electron microscopic studies, it was found that the as-hydrothermally prepared powders were crystallized to layered α-NaFeO₂ structure and the particles had spherical shape. The as-prepared Li[Ni_1/3Co_1/3Mn_1/3]O₂ delivered an initial discharge of about 110 mA h g⁻¹ due to lower crystallinity. Heat treatment of the hydrothermal product at 800 °C was significantly effective to improve the structural integrity, which consequently affected the increase in the discharge capacity to 157 (4.3 V cut-off) and 182 mA h g⁻¹ (4.6 V cut-off) at 25 °C with good reversibility.     

Synthesis and characterization of high-density non-spherical Li(Ni1/3Co1/3Mn1/3)O2 cathode material for lithium ion batteries by two-step drying method

Non-spherical Li(Ni_1/3Co_1/3Mn_1/3)O₂ powders have been synthesized using a two-step drying method with 5% excess LiOH at 800 °C for 20 h. The tap-density of the powder obtained is 2.95 g cm⁻³. This value is remarkably higher than that of the Li(Ni_1/3Co_1/3Mn_1/3)O₂ powders obtained by other methods, which range from 1.50 g cm⁻³ to 2.40 g cm⁻³. The precursor and Li(Ni_1/3Co_1/3Mn_1/3)O₂ are characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and scanning electron microscope (SEM). XPS studies show that the predominant oxidation states of Ni, Co and Mn in the precursor are 2⁺, 3⁺ and 4⁺, respectively. XRD results show that the Li(Ni_1/3Co_1/3Mn_1/3)O₂ material obtained by the two-step drying method has a well-layered structure with a small amount of cation mixing. SEM confirms that the Li(Ni_1/3Co_1/3Mn_1/3)O₂ particles obtained by this method are uniform. The initial discharge capacity of 167 mAh g⁻¹ is obtained between 3 V and 4.3 V at a current of 0.2 C rate. The capacity of 159 mAh g⁻¹ is retained at the end of 30 charge-discharge cycle with a capacity retention of 95%.     

The characteristics of Ni–Co–Mn–O precursor and Li(Ni1/3Co1/3Mn1/3)O2 cathode powders prepared by spray pyrolysis

Ni–Co–Mn–O precursor powders with spherical shape and dense structure were prepared by spray pyrolysis from a spray solution containing a drying control chemical additive (DCCA) and polymeric precursors. In contrast, the Ni–Co–Mn–O precursor powders obtained from a spray solution without additives had a hollow and porous morphology. Ni–Co–Mn–O precursor powders with a spherical shape and dense structure yielded Li(Ni_1/3Co_1/3Mn_1/3)O₂ cathode powders with a spherical shape and fine size by means of a solid-state reaction with lithium hydroxide. The mean size of the spherical cathode powder was 1.1 μm. The discharge capacity of the Li(Ni_1/3Co_1/3Mn_1/3)O₂ powders with spherical shape and filled morphology was 195 mA h g⁻¹ at a current density of 0.1 C. The discharge capacities of the cathode powders with spherical shape and filled morphology at 55 °C decreased from 183 to 154 mA h g⁻¹ by the 30th cycle at a current density of 0.5 C.     

Electrochemical characterization of P2-type layered Na2/3Ni1/4Mn3/4O2 cathode in aqueous hybrid sodium/lithium ion electrolyte

P2-type layered Na_2/3Ni_1/4Mn_3/4O₂ has been synthesized by a solid-state method and its electrochemical behavior has been investigated as a potential cathode material in aqueous hybrid sodium/lithium ion electrolyte by adopting activated carbon as the counter electrode. The results indicate that the Na⁺/Li⁺ ratio in aqueous electrolyte has a strong influence on the capacity and cyclic stability of the Na_2/3Ni_1/4Mn_3/4O₂ electrode. Increase on the Li⁺ content leads to a shift of the redox potential towards a high value, which is favorable for the improvement of the working voltage of the layered material as cathode. It is found that the coexistence of Na⁺ and Li⁺ in aqueous electrolyte can improve the cyclic stability for the Na_2/3Ni_1/4Mn_3/4O₂ electrode. A reversible capacity of 54 mAh g⁻¹ was obtained with a high cyclability as the Na⁺/Li⁺ ratio was 2:2. Furthermore, an aqueous hybrid ion cell was assembled with the as-proposed Na_2/3Ni_1/4Mn_3/4O₂ as cathode and NaTi₂(PO₄)₃/graphite synthesized in this work as anode in 1 M Na₂SO₄/Li₂SO₄ (mole ratio as 2:2) mixed electrolyte. The cell shows an average discharge voltage at 1.2 V, delivering an energy density of 36 Wh kg⁻¹ at a power density of 16 W kg⁻¹ based on the total mass of the active materials.     

Co0.35Mn0.65Fe2O4 magnetic particles: Preparation and kinetics research of thermal process of the precursor

Precursor of nanocrystalline Co_0.35Mn_0.65Fe₂O₄ was synthesized by solid-state reaction at low heat using CoSO₄·7H₂O, MnSO₄·H₂O, FeSO₄·7H₂O, and Na₂C₂O₄ as raw materials. Nanocrystalline Co_0.35Mn_0.65Fe₂O₄ with spinel structure was obtained via calcining the precursor. The precursor and its calcined products were characterized using TG/DSC, FT-IR, XRD, SEM, EDS, and vibrating sample magnetometer. The results showed that the precursor dried at 353 K was a mixture consisted of CoC₂O₄·2H₂O, MnC₂O₄·2H₂O, and FeC₂O₄·2H₂O. However, when the precursor was calcined at 623 K for 2 h, highly crystallization Co_0.35Mn_0.65Fe₂O₄ [space group R-3 m (166)] was obtained with a crystallite size of 22 nm. Magnetic characterization indicated that the specific saturation magnetization of Co_0.35Mn_0.65Fe₂O₄ obtained at 773 K was 66.14 Am²/kg. The thermal process of precursor experienced two steps, which involves the dehydration of the waters of crystallization at first, and then decomposition of Co_0.35Mn_0.65Fe₂(C₂O₄)₃ and formation of crystalline Co_0.35Mn_0.65Fe₂O₄ together. Based on the Kissinger equation, the values of the activation energy associated with the thermal processes of the precursor were determined to be 78 and 146 kJ/mol for the first and second thermal process steps, respectively.     

Optimal synthesis and new understanding of P2-type Na2/3Mn1/2Fe1/4Co1/4O2 as an advanced cathode material in sodium-ion batteries with improved cycle stability

A sol-gel method with ethylene diamine tetraacetic acid and citric acid as co-chelates is employed for the synthesis of P2-type Na_2/3Mn_1/2Fe_1/4Co_1/4O₂ as cathode material for sodium-ion batteries. Among the various calcination temperatures, the Na_2/3Mn_1/2Fe_1/4Co_1/4O₂ with a pure P2-type phase calcined at 900 °C demonstrates the best cycle capacity, with a first discharge capacity of 157 mA h g^?1 and a capacity retention of 91 mA h g^?1 after 100 cycles. For comparison, the classic P2-type Na_2/3Mn_1/2Fe_1/2O₂ cathode prepared under the same conditions shows a comparable first discharge capacity of 150 mA h g^?1 but poorer cycling stability, with a capacity retention of only 42 mA h g^?1 after 100 cycles. Based on X-ray photoelectron spectroscopy, the introduction of cobalt together with sol-gel synthesis solves the severe capacity decay problem of P2-type Na_2/3Mn_1/2Fe_1/2O₂ by reducing the content of Mn and slowing down the loss of Mn on the surface of the Na_2/3Mn_1/2Fe_1/4Co_1/4O₂, as well as by improving the activity of Fe³⁺ and the stability of Fe⁴⁺ in the electrode. This research is the first to demonstrate the origin of the excellent cycle stability of Na_2/3Mn_1/2Fe_1/4Co_1/4O₂, which may provide a new strategy for the development of electrode materials for use in sodium-ion batteries.     

Synthesis and improved electrochemical performance of Al (OH)3-coated Li[Ni1/3Mn1/3Co1/3]O2 cathode materials at elevated temperature

Spherical Li[Ni_1/3Co_1/3Mn_1/3]O₂ powders were synthesized from LiOH·H₂O and coprecipitated spherical metal hydroxide, (Ni_1/3Mn_1/3Co_1/3)(OH)₂ and coated with Al(OH)₃. The Al(OH)₃-coated Li[Ni_1/3Co_1/3Mn_1/3]O₂ showed a capacity retention of 80% at 320 mA g⁻¹ (2 C-rate) based on 20 mA g⁻¹ (0.1 C-rate), while the pristine Li[Ni_1/3Co_1/3Mn_1/3]O₂ delivered only 45% at the same current density. Also, unlike pristine Li[Ni_1/3Co_1/3Mn_1/3]O₂, the Al(OH)₃-coated Li[Ni_1/3Co_1/3Mn_1/3]O₂ cathode exhibits excellent rate capability and good thermal stability.