Nowadays, lithium (Li) metal batteries arouse widespread concerns due to its ultrahigh specific capacity (3,860 mAh g
−1
). However, the growth of Li dendrites has always limited their industrial development. In this paper, the use of concentrated electrolyte with lithium difluoro(oxalate)borate (LiODFB) salt in 1, 2-dimethoxyethane (DME) enables the good cycling of a Li metal anode at high Coulombic efficiency (up to 98.1%) without dendrite growth. Furthermore, a Li/Li cell can be cycled at 1 mA cm
−2
for over 3,000 h. Besides, compared to conventional LiPF
6
-carbonate electrolyte, Li/LiFePO
4
cells with 4 M LiODFB-DME exhibit superior electrochemical performances, especially at high temperature (65°C). These outstanding performances can be certified to the increased availability of Li
+
concentration and the merits of LiODFB salt. We believe that the concentrated LiODFB electrolyte is help to enable practical applications for Li metal anode in rechargeable batteries.
Lithium (Li) metal is regarded as the ideal anode for rechargeable Li-metal batteries such as Li-S and Li-air batteries. A series of problems caused by Li dendrites, such as low Coulombic efficiency (CE) and a short circuit, have limited the application of Li-metal batteries. In this study, a graphene-modified three-dimensional (3D) Copper (Cu) current collector is addressed to enable dendrite-free Li deposition. After Cu foam is immersed into graphene oxide (GO) suspension, a spontaneous reduction of GO, induced by Cu, generates reduced graphene oxide on a 3D Cu (rGO@Cu) substrate. The rGO@Cu foam not only provides large surface area to accommodate Li deposition for lowering the local effective current density, but also forms a rGO protective layer to effectively control the growth of Li dendrites. As current collector, the rGO@Cu foam shows superior properties than commercial Cu foam and planar Cu foil in terms of cycling stability and CE. The rGO@Cu foam delivers a CE as high as 98.5% for over 350 cycles at the current density of 1 mA cm−2. Furthermore, the full cell using LiFePO4 as cathode and Li metal as anode with rGO@Cu foam as current collector (LiFePO4/rGO@Cu-Li) is assembled to prove the admirable capacities and indicates commercialization of Li-metal batteries.
Two-dimensional (2D) MoS 2 is one of the most representative materials of the transition metal dichalcogenide (TMD) family, which is mostly studied in the semiconductor 2H and metal 1T phases. However, the properties of the metalloid 1T′ phase remain unclear because of its immature preparation process and thermodynamic instability (metastable state). Herein, this study used theoretical calculations to discover the relationship and conditions for MoS 2 to transition between the 2H, 1T, and 1T′ phases. Meanwhile, charge and discharge voltages and current density were controlled by ion insertion technology, and then 1T′-MoS 2 with large size and definite morphology (the whole process was called "phase transition engineering") was prepared. The prepared 1T′-MoS 2 was used as the anode material for lithium-ion batteries. Compared with 2H-MoS 2 , the cyclic stability and specific capacity of 1T′-MoS 2 were greatly improved. In addition, phase transformation of natural molybdenite (2H-MoS 2 ) by phase transition engineering also yielded promising electrochemical properties. Consequently, phase transition engineering not only provided an opportunity for the phase transformation of TMDs of natural sulfide metals such as molybdenite but also offered an effective method to investigate the properties of 2D metastable polymorphic materials.
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