RESUMEN
As a mainstream technology for recycling spent lithium-ion batteries, direct regeneration is rapidly developed due to its high efficiency and green characteristics. However, efficient reuse of spent LiNixCoyMn1- x - yO2 cathode is still a significant challenge, as the rock salt/spinel phase on the surface hinders the Li replenishment and phase transformation to the layered structure. In this work, the fundamental understanding of the repair mechanism is confirmed that the oxidizing atmosphere is the crucial factor that can greatly improve the rate and degree of phase restoration. Particularly, a ternary-component molten salt system (LiOH-Li2CO3-LiNO3) is proposed for direct regeneration of LiNi0.5Co0.2Mn0.3O2 (NCM523), which can in situ generate the strong oxidizing intermediate of superoxide radicals. Additionally, it shows a liquid-like reaction environment at a lower temperature to acceclerate the transport rate of superoxide-ions. Therefore, the synergistic effect of LiOH-Li2CO3-LiNO3 system can strengthen the full restoration of rock salt/spinel phases and achieve the complete Li-supplement. As anticipated, the regenerated NCM523 delivers a high cycling stability with a retention of 91.7% after 100 cycles, which is even competitive with the commercial NCM523. This strategy provides a facile approach for the complete recovery of layer structure cathode, demonstrating a unique perspective for the direct regeneration of spent lithium-ion batteries.
RESUMEN
As a promising high energy density cathode, single-crystal Ni-rich cathode face poor diffusion dynamics, which leads to poor structural evolution, poor cyclic stability and unfavorable rate performance, thus impeding its wider application. Herein, the strategy of synergistic surface modification by ionic conductor coating and trace element doping is delicately designed. The surface protective Li3BO3 layer is wrapped on the single-crystal LiNi0.83Co0.11Mn0.06O2 (NCM83), which can improve the compatibility of cathode/electrolyte with reduced interface resistance. While Zr is incorporated into bulk to stabilize the crystal structure and migration channel. This synergistic strategy achieves the improvement of ionic transport and structural stability of single-crystal NCM83 (Zr-NCM83@B) from the outer surface to the inner body. As expected, the modified cathode Zr-NCM83@B demonstrates a satisfying electrochemical performance. It delivers a high reversible capacity of 169 mAh g-1 in coin-type half-cell at 4C within 3.0-4.3 V. Remarkably, it displays excellent capacity retention of 83.5 % in Zr-NCM83@B || graphite pouch-type full-cell over 1400 cycles at 1C with high voltage range of 2.8-4.4 V. This synergistic surface modification provides a reference for commercial development of advanced single-crystal Ni-rich cathode under harsh testing conditions.
RESUMEN
Ni-rich layered oxides are considered as promising cathode materials for Li-ion batteries (LIBs) due to their satisfying theoretical specific capacity and reasonable cost. However, poor cycling stability caused by structural collapse and interfacial instability of the Ni-rich cathode material limits the further applications of commercialization. Herein, a series of B-doped single-crystal LiNi0.83Co0.05Mn0.12O2 (NCM) are designed and fabricated, aiming to improve the structural stability and enlarge the Li+-ions diffusion paths simultaneously. It reveals that B-doping at TM layers will facilitate the formation of stronger B-O covalent bonds and expand the layered distance, significantly enhancing the thermodynamics and kinetic of NCM electrode. With the synergistic effect of single-crystalline architecture and appropriate B-doping, it can effectively alleviate the occurrence of internal strain with structural degradation and boost the intrinsic rate capability synchronously. As anticipated, the 0.6 mol % B-doped NCM electrode exhibits enhanced rate property and superior cycle stability, even at the harsh condition of high-temperature and elevated cut-off voltage. Remarkably, when tested in pouch-type full-cell, it maintains high reversible capacity with superior capacity retention of 91.35% over 500 cycles with only 0.0173% decay per cycle. This research illustrates the feasibility of B-doping and single-crystalline architecture to improve the electrochemical performance, which is beneficial to understand the enhancement effect and provides the design strategy for the commercialization progress of Ni-rich cathode materials.