Sodium-ion batteries (SIBs) operating under high-voltages suffer from unstable cathode-electrolyte interphase (CEI) formed on the cathode surface , resulting in continuous electrolyte decomposition, surface reconstruction, transition metal dissolution, and eventually capacity decay. Therefore, designing high-voltage electrolyte and constructing the robust CEI are critical for high-energy SIBs. Herein, a localized high-concentration electrolyte (LHCE) is fabricated by dissolving sodium hexafluorophosphate in methyl ethyl carbonate, fluorinated ethylene carbonate and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, which demonstrates oxidative stability exceeding 6 V relative to Na + /Na. The dense and homogeneous inorganics-rich CEIs are generated by the preferential decomposition of PF 6 − anions during the electrochemical charge to 4.4 V, which lower interface impedance, facilitate Na + transportation and suppress subsequent side reactions. Consequently, the cell integrating high-voltage P2-Na 0.7 Li 0.03 Mg 0.03 Ni 0.27 Mn 0.6 Ti 0.07 O 2 cathode and Na anode exhibits a capacity retention of 87.3% after 200 cycles and a high-rate discharge capacity of 84 mA h g −1 at 20 C under a high cut-off voltage of 4.4 V. This work offers a feasible pathway to tailor electrolyte chemistry and interphase properties for practical next generation high-voltage SIBs.
Xiangyu Ge,Jinjin Li,Chenhui Zhang,Yuhong Liu,Jianbin Luo
Several ionic liquids (ILs) are formed in situ with monovalent metal salts and ethylene glycol (EG). The macroscale superlubricity and antiwear properties of the ILs were studied between ceramic materials. Superlow coefficients of friction of less than 0.01 could be obtained for all ILs at silicon nitride (Si3N4) interfaces induced by tribochemical reactions. Notably, the IL ([Li(EG)]PF6) formed with LiPF6 and EG exhibited the greatest superlubricity and antiwear properties. The results of film thickness calculations and surface analysis showed that the lubrication regime during the superlubricity period was the mixed lubrication, and a composite tribochemical layer (composed of phosphates, fluorides, silica (SiO2), and ammonia-containing compounds), hydration layer, and fluid film contributed to superlubricity and wear protection. It was found that the small size of metal cations was beneficial for alleviating wear, and PF6– anions exhibited the smallest friction and best antiwear performance at Si3N4 interfaces. This work studied the lubricity and antiwear properties of ILs with different cations and anions, enriching the range of alternative ILs for macroscale superlubricity and low wear, and is of importance to engineering applications.
Chao Li,Jing Xue,Ao Huang,Jing Ma,Fangzhu Qing,Aijun Zhou,Zhihong Wang,Yuehui Wang,Jingze Li
Owing to the unique redox reaction and the relative low molar mass of the repeating unit, poly(N-vinylcarbazole) (PVK) was selected as an advanced organic cathode for potassium-ion-based dual-ion battery (PDIB) with the K foil anode and KPF 6 -based electrolyte. The operation mechanism of this PDIB is that PF 6 − anions are migrated from the electrolyte and incorporated into PVK cathode via the attraction to the positively charged N atom of carbazole ligand, and then are released into the electrolyte in the subsequent discharge process; simultaneously, K + cations are reversibly stored/removed in/from the anode during charging/discharging. It shows a high median operation potential of 4.05 V vs. K + /K and can achieve a high specific capacity of 117 mAh g −1 at 20 mA g −1 , which is close to its theoretical value of 138 mAh g −1 . More impressively, even at the highest current density of 2000 mA g −1 for 500 cycles, a high average specific capacity of 61 mAh g −1 can still be obtained with capacity rentation of 55%.
危险品化学品经营许可证（带存储）