Synergistic effects of ion doping and surface-modifying for lithium transition-metal oxide: Synthesis and characterization of La 2 O 3 -modified LiNi 1/3 Co 1/3 Mn 1/3 O 2

Design and synthesis of nickel-doped cobalt molybdate microrods: An effective electrocatalyst for the determination of antibiotic drug ronidazole

Ronidazole (RDZ) is a veterinary antibiotic drug that has been used in animal husbandry as feed. However, improper disposal and illegal use of pharmaceuticals have severely polluted water resources. Doping/substitution of metal ions is an effective strategy to change the material's crystal phase, morphology, and electrocatalytic activity. In this work, nickel (Ni²⁺)-doped cobalt molybdate microrods (NCMO MRs) were prepared for the electrochemical detection of RDZ. The catalyst was prepared by reflux method followed by calcination at 500 °C. The prepared catalyst was confirmed by various spectroscopic and microscopic analyses. XRD and Raman spectroscopy demonstrated that the phase transition from β-CoMoO₄ to α-CoMoO₄ was achieved by Ni²⁺ doping. The SEM analysis showed that cobalt molybdate (CMO) microrods were self-assembled during Ni²⁺ doping and formed an urchin-like structure, and the average diameter of the MRs was ±50 nm. The electrocatalytic activity of the catalysts was analyzed using the CV technique. The NCMO MRs/GCE exhibited the higher current response than the pristine CMO. The electron transfer coefficient (α = 0.56) and heterogeneous rate constant (ks = 0.32 s^-1) of NCMO MRs/GCE were evaluated by kinetic studies. In addition, the diffusion coefficient of RDZ was determined to be 2.32 × 10^-5 cm²/s. Moreover, NCMO MRs/GCE exhibits a low detection limit for RDZ (15 nM) as well as a higher sensitivity (1.57 μA μM^-1 cm^-2). The fabricated RDZ sensor was successfully applied to analysis of lake and tap water samples. Based on the results, we believe that the as-prepared NCMO MRs/GCE is a viable electrode material for RDZ sensors in environmental monitoring.

Demystifying the Lattice Oxygen Redox in Layered Oxide Cathode Materials of Lithium-Ion Batteries

The practical application of lithium-ion batteries suffers from low energy density and the struggle to satisfy the ever-growing requirements of the energy-storage Internet. Therefore, developing next-generation electrode materials with high energy density is of the utmost significance. There are high expectations with respect to the development of lattice oxygen redox (LOR)-a promising strategy for developing cathode materials as it renders nearly a doubling of the specific capacity. However, challenges have been put forward toward the deep-seated origins of the LOR reaction and if its whole potential could be effectively realized in practical application. In the following Review, the intrinsic science that induces the LOR activity and crystal structure evolution are extensively discussed. Moreover, a variety of characterization techniques for investigating these behaviors are presented. Furthermore, we have highlighted the practical restrictions and outlined the probable approaches of Li-based layered oxide cathodes for improving such materials to meet the practical applications.

Fluorine-Doped LiNi0.8Mn0.1Co0.1O2 Cathode for High-Performance Lithium-Ion Batteries

For advanced lithium-ion batteries, LiNixCoyMnzO2 (x + y + z = 1) (NCM) cathode materials containing a high nickel content have been attractive because of their high capacity. However, to solve severe problems such as cation mixing, oxygen evolution, and transition metal dissolution in LiNi0.8Co0.1Mn0.1O2 cathodes, in this study, F-doped LiNi0.8Co0.1Mn0.1O2 (NCMF) was synthesized by solid-state reaction of a NCM and ammonium fluoride, followed by heating process. From X-ray diffraction analysis and X-ray photoelectron spectroscopy, the oxygen in NCM can be replaced by F− ions to produce the F-doped NCM structure. The substitution of oxygen with F− ions may produce relatively strong bonds between the transition metal and F and increase the c lattice parameter of the structure. The NCMF cathode exhibits better electrochemical performance and stability in half- and full-cell tests compared to the NCM cathode.

Precise Surface Engineering of Cathode Materials for Improved Stability of Lithium-Ion Batteries

As lithium-ion batteries continue to climb to even higher energy density, they meanwhile cause serious concerns on their stability and reliability during operation. To make sure the electrode materials, particularly cathode materials, are stable upon extended cycles, surface modification becomes indispensable to minimize the undesirable side reaction at the electrolyte-cathode interface, which is known as a critical factor to jeopardizing the electrode performance. This Review is targeted at a precise surface control of cathode materials with focus on the synthetic strategies suitable for a maximized surface protection ensured by a uniform and conformal surface coating. Detailed discussions are taken on the formation mechanism of the designated surface species achieved by either wet-chemistry routes or instrumental ones, with attention to the optimized electrochemical performance as a result of the surface control, accordingly drawing a clear image to describe the synthesis-structure-performance relationship to facilitate further understanding of functional electrode materials. Finally, perspectives regarding the most promising and/or most urgent developments for the surface control of high-energy cathode materials are provided.

Enhancing High-Voltage Performance of Ni-Rich Cathode by Surface Modification of Self-Assembled NASICON Fast Ionic Conductor LiZr2(PO4)3

Coating methodology is commonly employed in the enhancement of Ni-rich cathodes for Li-ion batteries as an efficient approach, while its strategy and effect are still great challenges to achieve success in surface modifications for comprehensive electrochemical properties. In this work, the surface of Ni-rich cathode LiNi_0.82Co_0.15Al_0.03O₂ (NCA) is modified by intimately coating NASICON-type solid electrolyte LiZr₂(PO₄)₃ (LZP) via a facile approach involving electrostatic attraction. With well-designed architecture and a uniform NASICON-type LZP nanolayer wrapping over the NCA microsphere, the entire electrode demonstrates exceptional Li⁺ diffusion and conductivity and suppresses the side reaction between electrolyte and electroactive NCA, stabilizing the phase interface with less Li⁺/Ni²⁺ cation mixing. As a result, the NCA@LZP can deliver a high reversible capacity of 182 mAh g^-1 at 1C in 2.7-4.3 V, maintaining the capacity retention of 84.6% after 100 cycles. More importantly, the structure stability of NCA is enhanced substantially by surface modification of LZP at high cutoff voltage. It achieves a reversible capacity of 204 mAh g^-1 and keeps 100.4 mAh g^-1 after 500 cycles at 1C in the potential range of 2.7-4.5 V. This effective strategy of using NASICON fast ionic conductor like LZP as a coating layer may provide a new insight to modify the surface of Ni-rich electrode, improving the rate capability and cyclic performance under high voltage.