3.4 | LITHIUM ALLOYS MODIFIED ELECTROLYTES
In the past decades, all-solid-state Li batteries received increasing
attentions due to nonflammability, dendrite blocking, and stability over
large potential windows[123]. But how to realize high safety, high
power density, and high energy density for all-solid-state Li batteries
is still a challenge. Recently, Hu’s group creatively combined the
lithium alloy anode with garnet electrolyte to solve the problems of
all-solid-state Li batteries[123-126]. For example, in 2017, they
first proposed a new methodology for reducing the garnet/Li-metal
interfacial resistance by forming Li-Ge alloy. First a thin Ge layer (20
nm) was evaporated onto the garnet pellet by an electron beam
evaporation system, then put a small piece of Li metal disc on the
Ge-modified garnet, after heating, the Li-Ge alloy anode would be
formed. Because the effective contact area between Ge-modified-garnet
and Li-metal anode increased more than eight times compared to bare
garnet due to the alloying reaction between Li and Ge as shown in Figure
9a, the Li/Ge-modified garnet delivered a small interfacial resistance
of 115 Ω·cm2, far smaller than the Li/bare garnet
(≈900 Ω·cm2). When it assembled with
LiFePO4 to form an all-solid-state Li battery as shown
in Figure 9b, the cycling performance of this all-solid-state Li battery
has been improved significantly, even comparable with the full batteries
using the liquid electrolyte as shown in Figure 9c. Even the coulombic
efficiency was better than the full cells using liquid electrolyte in
Figure 9d.