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Page 4 of 11 Lv et al. Energy Mater 2024;4:400018 https://dx.doi.org/10.20517/energymater.2023.90

RESULTS AND DISCUSSION
The LM-W5, LM-W10 and LM-W15 composites were prepared using a simple one-step grinding method.
As shown in Supplementary Figure 1, the pure LM (GaInSn) displays as a liquid droplet with a metallic
luster; after mixing with different mass ratio Nano-sized W powder, the LM-W5 still contains a lot of LM
droplets, showing not much change in the properties of LM; however, the LM-W10 and LM-W15 form a
paste that displays the characteristics of low surface tension and high viscosity. To further evaluate
electrochemical performance to select the optimal W content [Supplementary Figure 2], the Li/LM-W5/CF,
Li/LM-W10/CF and Li/LM-W15/CF electrodes were prestored with 1 mAh/cm of Li, respectively, and
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assembled into symmetrical cells with two identical electrodes. The Li/LM-W5/CF exhibited a relatively
high over-potential of 0.15 V and began to oscillate after 300 h, which was ascribed to high surface tension
of LM-W5 leading to poor wettability with the current collector at a current density of 5 mA/cm . The
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Li/LM-W10/CF and Li/LM-W15/CF displayed a relatively low over-potential at 5 mA/cm ; however,
considering that inactive metal W does not provide capacity and cost, we select LM-W10 preferentially for
the follow-up study.

As shown in Figure 1A and B, the schematic diagrams of LM-W10 and LM were presented, and contact
angles were tested to investigate the wettability with current collectors. On the glass slide substrate, the
contact angle of LM is 135°; by contrast, the LM-W10 could be easily spread on the glass slide, and it has
strong adhesion to the substrate. Then, both LM-W10 and LM were spread on CF to fabricate LM-W10/CF
and LM/CF. Observations from the optical microscope on morphology evolution [Supplementary Figure 3]
show that the surface morphology of LM/CF is smooth and flat, while the LM-W10/CF is rough and
convex. The mixing of W powder can completely change the physical properties of LM, thereby changing
its surface tension and viscosity. According to the results of elemental distribution
[Supplementary Figure 4], the W powder is evenly dispersed in LM. Figure 1C and D shows the
morphology of LM-W10/CF and LM/CF after lithium deposition with different amounts. The LM-W10/CF
reacts with Li smoothly, while the LM/CF surface still has a large amount of liquid droplets. With higher
amount of lithium deposition, a thin and dense layer of metallic Li is deposited on the LM-W10/CF;
however, the Li alloying process of LM/CF remains not optimistic, with a large amount of LM still present
on electrode surface and Li alloy compounds also prone to exfoliation from the CF. Meanwhile, the SEM
results also clearly revealed that the surface of LM-W10/CF after lithiation is more compact and flatter
[Supplementary Figure 5A]. In sharp contrast, the LM/CF still has plenty of LM spherical droplets that are
not involved in the alloying reaction after 1 mAh/cm of lithiation; with the increasing amount of Li, many
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cracks appear in the alloying area of the electrode surface, and these alloy compounds are also easy to fall off
the CF [Supplementary Figure 5B]. The main reason is the high fluidity of LM on the CF surface, and its
contact with CF is not close, resulting in the detachment of Li alloy compounds from CF, while the W
mixing tunes LM wettability, giving LM-W10 a stronger adhesion on CF, thus forming a complete
structure. It makes the charge transfer between the CF and the electrode material more rapid and stable,
homogenizing Li ion transfer flux of the anode surface and making the Li alloy compounds more uniform
and denser. Additionally, it demonstrates that we have successfully developed a new conductive-binder-free
anode of LM-W10/CF. To verify whether the W mixing will affect self-healing nature of the LM, the
morphological changes during lithiation/delithiation of the LM-W10/CF were observed by SEM. The
pristine electrode surface was observed to have an even layer of LM-W10, as shown in
Supplementary Figure 6A. After full lithiation, the surface of LM-W10 alloy compounds is more compact
and flatter [Supplementary Figure 6B]. The SEM image in Supplementary Figure 6C displays the formation
of numerous consistent, smaller and glittery LM-W10 spherical particles after the delithiation process with
some of the delithiation LM-W10 micro-particles also exhibiting a deformed shape, and the elemental
distribution also further verifies the formation of liquid droplet LM-W10 [Supplementary Figure 6C0-C4];
these results indicate that the metal mixing strategy has a negligible effect on the self-healing nature of LM.