Graphical Double time : It is demonstrated that the concentrated solution of 3 M LiPF 6 -ethyl methyl carbonate/trimethyl phosphate (7 : 3 by vol.) is also compatible with graphite negative and works well for full dual-graphite batteries. Although trimethyl phosphate (TMP)-based electrolyte solutions are effective to resist flames in non-aqueous electrical energy storage devices, they are usually not so compatible with Li-graphite negative electrodes. Herein, we solve this problem by increasing the concentration of LiPF 6 salt in the solution. A benchmark graphite negative electrode (MCMB, mesocarbon microbeads) can deliver a capacity over 325 mAh g −1 and maintain good cyclability in a solution of 3 M LiPF 6 -ethyl methyl carbonate (EMC)/TMP (7 : 3 by vol.). Moreover, our previous work has confirmed that the graphite positive electrode also works very well in the above solution. Therefore, this solution can cater to both anion-graphite and Li-graphite intercalation electrodes, which enables the construction of dual-graphite batteries (DGBs). There are some problems arising during the DGB operation, and corresponding strategies are proposed.
Imide salt–polymer plastic crystal electrolytes (PPCEs) have been demonstrated to be very promising solid-state electrolytes for ambient lithium ion batteries (LIBs). However, anodic Al dissolution at high voltage, due to these salts, cannot form an AlF3/LiF passivation film (like LiPF6) on an Al surface, which limits their application in high-voltage solid-state LIBs. In this work two ambient workable PPCEs with different lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) concentrations are designed to investigate anodic Al dissolution suppression in solid-state imide salt-based electrolytes. The anodic Al dissolution is examined by a scanning electron microscope (SEM) and an energy dispersive spectrometer (EDS). The electrochemical performance is evaluated by solid-state LiCoO2/PPCE/Li4Ti5O12 cells. The results demonstrate that anodic Al dissolution is efficiently suppressed and the cell electrochemical performance is greatly elevated by optimizing LiTFSI concentration in PPCEs. The suppression mechanism of Al corrosion in concentrated PPCE is analyzed and suggested.
Solid-state electrolytes have become a promising approach for rechargeable lithium batteries with enhanced safety and high energy density . However, the rigid nature of ceramic electrolytes would result in the poor interfacial contact, and polymer electrolytes suffer from inferior electrochemical performance and unsatisfied mechanical strength to suppress Li dendrites. In this work, we report a flexible Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 (LATP)-reinforced polyvinylidene fluoride (PVDF)-based solid composite electrolyte with superior performances in terms of high ionic conductivity (1.64 × 10 −3 S cm −1 at room temperature), high lithium transference number (0.45), wide electrochemical window (0–4.76 V) and enhanced tensile strength (14.2 MPa). The existence of LATP permits the utilization of high Li-salt content which increases the charge carrier concentration. Meanwhile, LATP facilitates the Li + conduction process and enhances the mechanical strength, leading to a long-term electrochemical stability of symmetric Li cell for 600 h at 0.2 mA cm −2 . Assembled with LiFePO 4 cathode, the all-solid-state Li battery delivers a high capacity of 153.7 mA h g −1 at 0.3 C with remarkable cycle stability. This work provides a bright future for composite polymer electrolytes in the application of all-solid-state lithium batteries .
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