RESUMEN
Cobalt-free (Co-free) and nickel-rich (Ni-rich) cathode materials have attracted significant attention and undergone extensive studies due to their affordability and superior energy density. However, the commercialization of these Co-free materials is hindered by challenges such as cation disorder, irreversible phase changes, and inadequate high-voltage performance. To overcome these challenges, a Co-free ternary cathode material of Mg/Al double-pillared LiNiO2 (NMA) synthesized via a wet-coating and lithiation-sintering technique is proposed. Fundamental studies reveal that Mg and Al have the potential to form a distinctive double-pillar structure within the layered cathode, enhancing its structural stability. To be specific, the strategic placement of Mg and Al in Li and Ni layers, respectively, effectively reduces Li+/Ni2+ disorder and prevents irreversible phase transitions. Additionally, the inclusion of Mg and Al refines the primary grains and compacts the secondary grains in the cathode material, reducing stress from cyclic usage and preventing material cracking, thereby mitigating electrolyte erosion. As a result, NMA demonstrates exceptional electrochemical performance under a high charge cutoff voltage of 4.6 V. It maintains 70% of initial specific capacity after 500 cycles at 1 C and exhibits excellent rate performance, with a capacity of 162 mAh g-1 at 5 C and 149 mAh g-1 at 10 C. As a whole, the produced NMA achieves a high structural stability in cases of excessive delithiation, providing a groundbreaking solution for the development of cost-effective and high-energy-density cathode materials for lithium-ion batteries.
RESUMEN
Li metal anodes are extensively studied owing to their unparalleled advantages in achieving high energy density. However, safety issues originating from dendritic Li growth are always a huge hindrance for applications in Li metal batteries (LMBs). In this study, a functional additive, 4,6-dimethyl-2-mercaptopyrimidine (DMP), which is a typical leveler in the copper electroplating industry, is selected to suppress Li dendrite formation. Various Li-metal-based batteries are systematically investigated and they show stable performances, such as excellent cycling stability above 800 h at 3 mA cm-2 in Li||Li cells and 400 cycles with high coulombic efficiencies (CEs >98%) at 1 mA cm-2 in Li||Cu cells. Furthermore, a comprehensive verification of the protective mechanism induced by the DMP leveling agent shows that the leveler updated the Li+ solvation structure and occupied the inner Helmholtz plane of the Li anode. The planar DMP molecular layer absorbed on the surface of the Li metal can suppress side reactions and modify the Li deposition behavior via steric hindrance, inducing homogeneous Li deposition. Interestingly, the DMP leveler does not participate in the formation of the solid electrolyte interphase. This study can stimulate further ideas on non-depleting but effective levelers as electrolyte additives for high-performance LMBs.
RESUMEN
Concentration of electrolyte has significant effects on performances of rechargeable batteries. Previous studies mainly focused on concentrated electrolytes. So far, only several recipes on low-concentration electrolytes were studied, performing enhanced performance in advanced rechargeable batteries. Here, based on common electrolyte components, a low-concentration electrolyte composed of 0.2â M lithium hexafluorophosphate (LiPF6 ) solvated in fluoroethylene carbonate (FEC) and ethyl methyl carbonate (EMC) is employed for high-voltage Li metal battery. The synergistic working mechanisms of introducing fluorine-containing solvent in the solvated structure and low salt concentration effect are revealed, resulting in LiF-rich, uniform, and robust solid electrolyte interphase layer and fewer unfavorable decomposition products. As a result, this low-concentration electrolyte significantly enhances electrochemical performances of Li||Li symmetric cells and high-voltage LiCoO2 ||Li batteries.