Li
metal anode is deemed the most promising candidate anode for
high-energy battery systems such as Li-sulfur and Li-fluoride batteries.
However, some severe challenges, for example, facile formation and
growth of Li dendrites, large volume evolution of hostless Li ,and
low Coulombic efficiency of Li plating/stripping, still hinder the
commercialization of Li-metal batteries (LMBs). Herein, a free-standing
and highly flexible 3D current collector made of carbon nanofibers
(CNFs) conformally coated by continuous Sn layer is synthesized by
electrospinning method. Sn layer enables a lithiophilic and alloyable
carbon skeleton surface and provides uniform and continuous Li nucleation
sites, leading to unusual conformal Li plating behavior and effective
inhibition of Li dendrites. The spatial confinement of Li plating
mitigates the volume expansion and network distortion of CNFs. The
electric contact reinforced by Sn interlayer achieves highly reversible
Li stripping for more than 850 h for CNF-Sn@Li symmetric cell. The
small nucleation overpotential (28 mV) and potential polarization
(14 mV for symmetric cell) benefit from the low energy barrier of
Li–Sn alloying and following Li nucleation on Li–Sn
layer. For CNF-Sn@Li-LiFePO4 full cell, the capacity retention
ratio is as high as 92.2% after 150 cycles at 0. 5C and the reversible capacities are maintained at 134.3 and 106.7
mAh g–1 at 2C and 5C respectively. The design of 3D lithiophilic current collector instead
of planar Cu is a potential solution to highly safe LMBs.
Detrimental dendritic lithium (Li) growth, infinite volume expansion of Li deposition and inevitable excess electrolyte consumption have always impeded the successful application of Li metal anodes. Herein, a unique lithiophilic vertical cactus-like framework (LVCF) derived from a Zn/Cu-based coordination polymer through in situ chemical etching of Cu foam is proposed to enhance the safety and electrochemical performance of Li metal anodes. An ingenious strategy of releasing Cu ions from Cu foam in the presence of organic ligands is implemented successfully to achieve the coordination polymer precursor, resulting in the coexistence of massive lithiophilic nitrogen-containing functional groups, ZnO quantum dots and in situ grown carbon nanotubes (CNTs) in the LVCF, which is beneficial to avoiding the generation of harmful Li dendrites. Benefiting from the positive effects of the improved lithiophilicity, decreased local current density and relieved volume expansion, LVCF delivers an ultrastable Coulombic efficiency of 98.6% for 600 cycles at 1 mA cm-2 and an improved cycling lifespan of 1800 h for symmetric cells. Full cells comprising LVCF@Li anodes and LiFePO 4 cathodes can deliver an ultrahigh capacity of 101.8 mAh g-1 (capacity retention ratio: 77.9%) after 900 cycles at 1 C and excellent rate performance.
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