Research data supporting the publication "Evaluation of Ga0.2Li6.4Nd3Zr2O12 garnets: exploiting dopant instability to create a mixed conductive interface to reduce interfacial resistance for all solid state batteries"

The next major leap in energy storage is thought to arise from a practical implementation of all solid-state batteries, which remain largely confined to the small scale due to issues in manufacturing and mechanical stability. Lithium batteries are amongst the most sought after, for the high expected energy density and improved safety characteristics, however the challenge of finding a suitable solid-state electrolyte remains. Lithium rich garnets are prime contenders as electrolytes, owing to their high ionic conductivity (> 0.1 mS cm-1), wide electrochemical window (0 – 6 V) and stability with Li metal. However, the high Young’s modulus of these materials, poor wetting of Li metal and rapid formation of Li2CO3 passivating layers tends to give a detrimentally large resistance at the solid-solid interface, limiting their application in solid state batteries. Most studies have focused on La based systems, with very little work on other lanthanides. Here we report a study of the Nd based garnet Ga0.2Li6.4Nd3Zr2O12, illustrating substantial differences in the interfacial behaviour. This garnet shows very low interfacial resistance attributed to dopant exsolution which, when combined with moderate heating (175°C, 1h) with Li metal, we suggest forms Ga-Li eutectics which significantly reduces the resistance at the Li/Garnet interface to as low as 67 Ω cm2 (much lower than equivalent La based systems). The material also shows intrinsically high density (93%) and good conductivity (≥ 0.2 mS cm-1) via conventional furnaces in air. It is suggested these garnets are particularly well suited to provide a mixed conductive interface (in combination with other garnets) which could enable future solid-state batteries.

能源存储领域的下一次重大技术突破，被认为将来自全固态电池（all solid-state batteries）的实用化落地。目前这类电池因制造与机械稳定性方面的问题，仍大多局限于小规模应用场景。锂离子电池因预期拥有极高的能量密度与更优异的安全特性，成为当下最受追捧的电池技术之一，但寻找合适的固态电解质（solid-state electrolyte）仍是核心挑战。富锂石榴石（lithium rich garnets）是极具潜力的电解质候选材料，这得益于其高离子电导率（> 0.1 mS cm⁻¹）、宽电化学窗口（0 – 6 V）以及与金属锂的良好稳定性。然而，这类材料的杨氏模量（Young’s modulus）过高、与金属锂的润湿性较差，且会快速形成Li₂CO₃钝化层，往往会在固-固界面处产生极高的界面电阻，严重限制了其在全固态电池中的应用。目前绝大多数研究都聚焦于镧基体系，针对其他镧系元素（lanthanides）的相关工作极少。本文报道了钕基石榴石Ga₀.₂Li₆.₄Nd₃Zr₂O₁₂的研究结果，其界面行为与传统体系存在显著差异。该石榴石展现出极低的界面电阻，这归因于掺杂相的析出；当与金属锂在适度加热条件（175℃，1 h）下复合时，我们推测其会形成Ga-Li共晶相，可将锂/石榴石界面的电阻显著降低至67 Ω·cm²（远低于同等条件下的镧基体系）。该材料在空气气氛下通过常规烧结即可实现高致密度（93%）与优异的离子电导率（≥ 0.2 mS cm⁻¹）。研究表明，这类石榴石非常适合用于构建混合导电界面（与其他石榴石材料复配），有望为未来全固态电池的商业化应用提供支撑。