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.