Role of Al-doping with different sites upon the structure and electrochemical performance of spherical LiNi0.5Mn1.5O4 cathode materials for lithium-ion batteries

Enhanced Electrochemical Performance of a Ti-Cr-Doped LiMn1.5Ni0.5O4 Cathode Material for Lithium-Ion Batteries

Ti, Cr dual-element-doped LiMn_1.5Ni_0.5O₄ (LNMO) cathode materials (LTNMCO) were synthesized by a simple high-temperature solid-phase method. The obtained LTNMCO shows the standard structure of the Fd3®m space group, and the Ti and Cr doped ions may replace the Ni and Mn sites in LNMO, respectively. The effect of Ti-Cr doping and single-element doping on the structure of LNMO was studied by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM) characteristics. The LTNMCO exhibited excellent electrochemical properties with a specific capacity of 135.1 mAh·g^-1 for the first discharge cycle and a capacity retention rate of 88.47% at 1C after 300 cycles. The LTNMCO also has high rate performance with a discharge capacity of 125.4 mAh·g^-1 at a 10C rate, 93.55% of that at 0.1C. In addition, the CIV and EIS results show that the LTNMCO showed the lowest charge transfer resistance and the highest diffusion coefficient of lithium ions. The enhanced electrochemical properties may be due to a more stable structure and an optimized Mn³⁺ content in LTNMCO through TiCr doping.

Enhanced Electrochemical Performance of the LiNi0.5Mn1.5O4 Cathode Material by the Construction of Uniform Lithium Silicate Nanoshells

In order to alleviate the rapid capacity decay caused by the instability of the crystal structure and electrode/electrolyte interface, a series of Li₂SiO₃-coated LiNi_0.5Mn_1.5O₄ materials have been prepared via the lithium acetate-assisted sol-gel method followed by a short-term calcination process. During the sol-gel process, TEOS is hydrolyzed, condensed, and polymerized with the assistance of lithium acetate to form a Li⁺-embedded [Si-O-Si]_n network structure to ensure the uniformity of the coating. By changing the amount of TEOS and lithium acetate, the coating thickness can be precisely controlled, whose effects on the structural and electrochemical properties of LiNi_0.5Mn_1.5O₄ materials are intensively investigated. The results show that the material with an appropriate thickness of Li₂SiO₃ coating exhibits a larger primary particle size and reduced secondary particle agglomeration. The uniform Li₂SiO₃ coating with appropriate thickness can not only improve Li⁺ ion diffusion kinetics but also suppress side reactions and CEI growth at the electrode/electrolyte interface. Besides, the interaction of Li₂SiO₃ with HF can alleviate electrode corrosion and the dissolution of transition metal ions. All the abovementioned factors together promote the significant improvement of the electrochemical performance of Li₂SiO₃-coated LiNi_0.5Mn_1.5O₄ materials.

N-doped engineering of a high-voltage LiNi0.5Mn1.5O4 cathode with superior cycling capability for wide temperature lithium-ion batteries

Spinel LiNi_0.5Mn_1.5O₄ (LNMO) is one potential cathode candidate for next-generation high energy-density lithium-ion batteries (LIBs). However, serious capacity decay from its poor structural stability, especially at high operating temperatures, shadows its application prospects. In this work, N-doped LNMO (LNMON) was synthesized by a facile co-precipitation method and multistep calcination, exhibiting a unique yolk-shell architecture. Concurrently, N dopants are introduced into a LNMO lattice, endowing LNMON with a more stable structure via stronger Ni-N/Mn-N bindings. Benefiting from the synergistic effect of the yolk-shell structure and N-doped engineering, the obtained LNMON cathode exhibits an impressive rate and the state-of-the-art cycling capability, delivering a high capacity of 103 mA h g^-1 at 25 °C after 8000 cycles. Even at a high operating temperature of 60 °C, the capacity retention remains at 92% after 1000 cycles. The discovery of N dopants in improving the cycling capability of LNMO in our case offers a prospective approach to enable 5 V LNMO cathode materials with excellent cycling capability.