Elevated electrochemical performance of (NH4)3AlF6-coated 0.5Li2MnO3·0.5LiNi1/3Co1/3Mn1/3O2 cathode material via a novel wet coating method

Exploring the Effect of a MnO2 Coating on the Electrochemical Performance of a Li1.2Mn0.54Ni0.13Co0.13O2 Cathode Material

The effect of electrochemically active MnO2 as a coating material on the electrochemical properties of a Li1.2Mn0.54Ni0.13Co0.13O2 (LTMO) cathode material is explored in this article. The structural analysis indicated that the layered structure of the LTMO was unchanged after the modification with MnO2. The morphology inspection demonstrated that the rod-like LTMO particles were encapsulated by a compact coating layer. The MnO2 layer was able to hinder the electrolyte solution from corroding the LTMO particles and optimized the formation of a solid electrolyte interface (SEI). Meanwhile, lithium ions were reversibly inserted into and extracted from MnO2, which afforded an additional capacity. Compared with the bare LTMO, the MnO2-coated sample exhibited enhanced electrochemical performance. After the MnO2 coating, the first discharge capacity rose from 224.2 to 239.1 mAh/g, and the initial irreversible capacity loss declined from 78.2 to 46.0 mAh/g. Meanwhile, the cyclic retention climbed up to 88.2% after 100 cycles at 0.5 C, which was more competitive than that of the bare LTMO with a value of 71.1%. When discharging at a high current density of 2 C, the capacity increased from 100.5 to 136.9 mAh/g after the modification. These investigations may be conducive to the practical application of LTMO in prospective automotive Li-ion batteries.

The Effect of Excessive Sulfate in the Li-Ion Battery Leachate on the Properties of Resynthesized Li[Ni1/3Co1/3Mn1/3]O2

In order to examine the effect of excessive sulfate in the leachate of spent Li-ion batteries (LIBs), LiNi_1/3Co_1/3Mn_1/3O₂ (pristine NCM) and sulfate-containing LiNi_1/3Co_1/3Mn_1/3O₂ (NCMS) are prepared by a co-precipitation method. The crystal structures, morphology, surface species, and electrochemical performances of both cathode active materials are studied by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and charge-discharge tests. The XRD patterns and XPS results identify the presence of sulfate groups on the surface of NCMS. While pristine NCM exhibits a very dense surface in SEM images, NCMS has a relatively porous surface, which could be attributed to the sulfate impurities that hinder the growth of primary particles. The charge-discharge tests show that discharge capacities of NCMS at C-rates, which range from 0.1 to 5 C, are slightly decreased compared to pristine NCM. In dQ/dV plots, pristine NCM and NCMS have the same redox overvoltage regardless of discharge C-rates. The omnipresent sulfate due to the sulfuric acid leaching of spent LIBs has a minimal effect on resynthesized NCM cathode active materials as long as their precursors are adequately washed.

The Decay Mechanism Related to Structural and Morphological Evolution in Lithium-Rich Cathode Materials for Lithium-Ion Batteries

Li-rich oxides have garnered intense interest recently for their excellent capacity in rechargeable lithium-ion batteries (LIBs). However, poor cycling stability and capacity degradation during the cycling process impede their practical application. Herein, two ball-shaped cobalt-free oxide materials, Li_1.1 Mg_0.05 Ni_0.3 Mn_0.55 O₂ and Li_1.1 Zn_0.05 Ni_0.3 Mn_0.55 O₂ , which exhibit excellent cycling performance at a high current between 2 V and 4.8 V, are demonstrated. The two Li-rich materials are prepared from hydrothermally synthesized carbonated precursors. Both oxides exhibit high reversible capacities of 237 and 231 mAh g^-1 at 20 mA g^-1 , respectively, originating from the redox of Ni²⁺ /Ni⁴⁺ and O^2- /(O₂ )^n- . Li_1.1 Mg_0.05 Ni_0.3 Mn_0.55 O₂ presents excellent cycling stability after 200 cycles with 90 % capacity retention. Studies of the structural evolution upon electrochemical cycling implies the cathodes undergo a volume expansion, which results in continuous expanding, cracking, and crushing of the spherical particles, which further induces capacity fading in the cathodes.

Mitigating the Surface Degradation and Voltage Decay of Li1.2Ni0.13Mn0.54Co0.13O2 Cathode Material through Surface Modification Using Li2ZrO3

In the quest to tackle the issue of surface degradation and voltage decay associated with Li-rich phases, Li-ion conductive Li₂ZrO₃ (LZO) is coated on Li_1.2Ni_0.13Mn_0.54Co_0.13O₂ (LNMC) by a simple wet chemical process. The LZO phase coated on LNMC, with a thickness of about 10 nm, provides a structural integrity and facilitates the ion pathways throughout the charge-discharge process, which results in significant improvement of the electrochemical performances. The surface-modified cathode material exhibits a reversible capacity of 225 mA h g^-1 (at C/5 rate) and retains 85% of the initial capacity after 100 cycles. Whereas, the uncoated pristine sample shows a capacity of 234 mA h g^-1 and retains only 57% of the initial capacity under identical conditions. Electrochemical impedance spectroscopy reveals that the LZO coating plays a vital role in stabilizing the interface between the electrode and electrolyte during cycling; thus, it alleviates material degradation and voltage fading and ameliorates the electrochemical performance.

The positive role of (NH4)3AlF6 coating on Li[Li0.2Ni0.2Mn0.6]O2 oxide as the cathode material for lithium-ion batteries

A Li-rich cathode material Li_1.2Ni_0.2Mn_0.6O₂ coated with (NH₄)₃AlF₆ and its enhanced electrochemical cycling performance.

Facile synthesis of nanostructured MoO3 coated Li1.2Mn0.56Ni0.16Co0.08O2 materials with good electrochemical properties

Li_1.2Mn_0.56Ni_0.16Co_0.08O₂ cathode materials were synthesized by a co-precipitation method, and consequently coated with MoO₃ by a molten salt method.

Enhanced cycling stability and rate capability of Bi2O3-coated Li1.2Mn0.54Ni0.13Co0.13O2 cathode materials for lithium-ion batteries

The LMNC-BO electrode presents an enhanced cycle performance, better rate capability and structural stability than bare LMNC.