Ironing Controllable Lithium into Lithiotropic Carbon Fiber Fabric: A Novel Li-Metal Anode with Improved Cyclability and Dendrite Suppression

摘要

Lithium metal as an anode in lithium-ion batteries is attracting more attention because of the high gravimetric/volumetric energy density and low electrochemical potential. However, the irreversible Li plating/striping can reduce the cycling capability and very possibly introduce dendrite growth, thus leading to a series of issues such as infinite volume change, low Coulombic efficiency, and uncontrollable solid electrolyte interphase. Here, we report a novel, single-side Li-infused carbon fiber fabric (LiCFF) with a controllable, minimized Li loading, which shows a highly reversible plating/stripping with an extremely low overpotential of less than 30 mV (Li foil: >1.0 V over 50 cycles) upon >3000 cycles (6000 and 2000 h) at 1 and 3 mA/cm(2) in symmetric cells, respectively. With a high areal capacity up to 10 mA h/cm(2) and a high current density of 10 mA/cm(2), the cell still shows a minimum overpotential of 150-175 mV after 250 cycles (500 h). Full-cell batteries using the LiCFF as "all-in-one" anodes without the additional slurry-making process and nickel-manganese-cobalt oxide (NMC) as cathodes exhibit an improved capacity retention when compared with Li foil: 32% at 0.5 C and 119% at 1.0 C capacity improved after 100 cycles. In parallel, the mossy/dendritic Li on the LiCFF was largely suppressed, which was confirmed using in situ observations of Li plating/striping in a capillary cell. The excellent electronic conductivity of the carbon fabric leads to small contact/transfer resistances of 3.4/3.8 Omega (Li foil: 4.1/44.4 Omega), enabling a drastically lowered energy barrier for Li nucleation/growth. Thus, a uniform current distribution results in forming a homogeneous Li layer instead of forming dendrites. The current LiCFF as the anode with controllable Li (n/p ratio), improved cycling stability, mitigated dendrite formation, and flexibility displays promising applications in versatile Li-metal batteries such as Li-NMC, Li-S, and Li-O-2.