為滿足能源需求，高容量電池體系如鋰硫電池、鋰-空氣電池、鋰金屬電池等成為研究熱點。在這些體系中，鋰金屬負(fù)極存在許多問題：
(1)鋰枝晶的生長容易引發(fā)短路，造成安全隱患;
(2)固體電解質(zhì)界面膜(Solid electrolyteinter phase, SEI)的不穩(wěn)定性，導(dǎo)致電解液的消耗并降低電池庫倫效率和循環(huán)壽命，這些問題嚴(yán)重阻礙了這些高容量電池體系的發(fā)展和實際應(yīng)用。
固態(tài)電解質(zhì)具有較高的離子電導(dǎo)率和一定的機械強度，在很大程度上可提高鋰電池安全性，即使在全固態(tài)鋰電池(All-solid-state Li batteries,ASSLBs)中發(fā)生短路，不可燃的固態(tài)電解質(zhì)也可避免著火和爆炸的發(fā)生。
另外，固態(tài)電解質(zhì)可保證電池的高能量/功率密度和長循環(huán)壽命，在提高電池穩(wěn)定性方面有很大發(fā)展?jié)摿?。但電解質(zhì)-電極間往往有較大界面電阻，阻礙了離子傳輸。
最近，Luo等通過在石榴石型固態(tài)電解質(zhì)表面沉積硅層，實現(xiàn)電解質(zhì)表面從疏鋰到親鋰的轉(zhuǎn)變，減小固-固界面電阻，對提高鋰金屬電池的安全穩(wěn)定性有重要意義。
Figure 1. Transitionfrom Super-lithiophobicity to Super-lithiophilicity of Garnet leads to a muchsmaller interfacial resistance.
實驗以Nb、Ca共摻雜Li7La3Zr2O12為研究體系，制備Li6.85La2.9Ca0.1Zr1.75Nb0.25O12(LLZ)固態(tài)電解質(zhì)。其中Nb可穩(wěn)定立方相，增強鋰離子傳導(dǎo);Ca可降低燒結(jié)溫度。通過PECVD在表面沉積很薄的硅層，可使界面電阻減小7倍，并保持穩(wěn)定的循環(huán)性能。該團隊還通過理論計算對該現(xiàn)象進行論證。
綜上，該工作提出通過沉積親鋰金屬可有效降低固態(tài)電解質(zhì)-電極界面電阻，對提高鋰金屬電池的安全性具有指導(dǎo)意義。
Figure 2.Evaluation of LLZ wettability with Li metal. (a) Schematic showing the designed LLZ pellet with only one half (orange) selectively coated with amorphous Si.(b) SEM image showing the contrast between the bare LLZ area and the Si-coatedarea. (c) A homemade setup for the wettability evaluation, where molten Li was loaded in a stainless steel boat on a hot plate (～200 °C). Digitalimages of the half-coated LLZ pellet before and after dipping in molten Li for.(d) 0, (e) 1, and (f) 4 s. This shows the dramatic wettability transition of LLZ from superlithiophobicity to superlithiophilicity using an amorphous Si coating.
Figure 3. Electrochemical performance of symmetriccells using Si-coated and bare LLZ. Schematic illustration showing the structure of symmetric cells with (a) LLZ or (b) Si-coated LLZ SSEs.(c)Electrochemical impedance spectroscopy (EIS) measurements of symmetric cells where the interfacial resistance of the Si-coated garnet cell was significantlydecreased. (inset) Digital image of a Li/Si-coated LLZ/Li symmetric cell. (d)Long-term cycling performance of the Li/Si-coated LLZ/Li symmetric cell at current densities of 0.05 and 0.1mA/cm2. (e) Voltage profiles of theLi/Si-coated LLZ/Li symmetriccell at current densities of 0.1 and 0.2 mA/cm2.
相關(guān)研究成果發(fā)表在著名刊物Journal of the American Chemical Society上(DOI：10.1021/jacs.6b06777. WeiLuo,Yunhui Gong,Yizhou Zhu,Kun Kelvin Fu et al. Transition from Superlithiophobicity to Superlithiophilicity of Garnet Solid-State Electrolyte.J. Am. Chem. Soc. 2016.)
