The development of high-energy-density and high-safety lithium-ion batteries requires advancements in electrolytes. The state-of-the-art carbonate electrolyte faces challenges for operation at high voltage and has low thermal stability. This study proposes an ionic liquid/ether composite high-entropy electrolyte that consists of N-propyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (PMP–TFSI) ionic liquid, dimethoxymethane (DME), lithium difluoro(oxalato)borate (LiDFOB), fluoroethylene carbonate (FEC), and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE). In this electrolyte, a unique coordination structure forms, where Li+ is surrounded in a high-entropy environment consisting of DME, FEC, TTE, TFSI–, DFOB–, and PMP+. The effects of this solution structure on the solid-electrolyte interphase chemistry and Li+ desolvation kinetics are examined. The proposed electrolyte has low flammability, high thermal stability, negligible corrosivity toward an Al current collector, and ability to withstand a high potential of up to 5 V without showing a significant side reaction current. Importantly, this electrolyte is highly compatible with graphite and SiOx anodes, as well as a high-nickel LiNi0.8Co0.1Mn0.1O2 cathode. Operando X-ray diffraction data confirm that the co-intercalation of DME and PMP+ into the graphite lattice, a long-standing challenge, is eliminated with this electrolyte. Graphite, SiOx, and LiNi0.8Co0.1Mn0.1O2 electrodes all exhibit better rate capability and cycling stability in the proposed electrolyte compared to those measured in a conventional carbonate electrolyte. A 4.5-V LiNi0.8Co0.1Mn0.1O2//graphite full cell with the proposed high-entropy electrolyte is shown to have superior specific capacity, rate capability, and cycling stability, demonstrating the great potential of the proposed electrolyte for practical applications.
Small-Molecule Polycyclic Aromatic Hydrocarbons
In article number 2400273, Jeng-Kuei Chang, Elise Yu-Tzu Li, Yu-Sheng Su, and co-workers present geometric variations of pyrene crystals during the electrochemical process in Li-ion batteries. The image illustrates the irreversible structural collapse caused by the vertical expansion of pyrene dimers, leading to the dissolution of pyrene into the electrolyte, a key factor affecting the long-term cycling stability of the anode material.
Lithium-sulfur batteries (LSBs) present a promising alternative to conventional lithium-ion (Li-ion) batteries due to their high energy density and theoretical capacity. However, their practical application is hindered by issues such as poor sulfur utilization, highly soluble lithium polysulfides (LiPSs), and rapid capacity decay. This study introduces an innovative cell configuration using a separator coated with reduced graphene oxide/carbon nanotube (rGO/CNT) microspheres. The rGO/CNT-coated separator aims to enhance electron transfer, confine LiPSs within the cathode region, and mitigate their migration to the anode. In particular, the LSB cell with an rGO/CNT-modified separator delivers an impressive initial capacity of 1482 mAh g−1 and demonstrates a low capacity decay rate of 0.09% per cycle. The highly conductive rGO/CNT-coated separator enhances active material utilization even at high rates, resulting in a significant capacity of 824 mAh g−1 at 4C. Furthermore, the rGO/CNT-modified separator shows an impressive capacity of 895 mAh g−1 under high sulfur loading of 4.8 mg cm−2 with long-term cycling performance. The results demonstrate that the rGO/CNT-coated separator significantly enhances sulfur reutilization, reduces capacity decay, and improves the electrochemical stability of LSBs. This configuration simplifies the manufacturing process and offers a viable solution for the practical application of LSBs.
