Zhao Jiang,Zhongxu Li,Xiuli Wang,Changdong Gu,Xinhui Xia,Jiangping Tu
All-solid-state lithium-metal batteries (ASSLMBs) with sulfide electrolytes have attracted attention owing to their superior safety and high energy density. However, interfacial instability of sulfide electrolytes against Li metal still hinders their applications. Herein, F-doping is adopted to optimize the structure of Li10SnP2S12. It is demonstrated that the Li9.95SnP2S11.95F0.05 (LSPSF) electrolyte exhibits a high ionic conductivity of 6.4 mS cm–1 because of F-doping, which can reduce the impurity Li2SnS3 and generate Li+ vacancies. In addition, the Li6PS5I (LPSI) glass–ceramic interlayer is employed to enhance the interfacial stability between the sulfide electrolyte and Li metal by restraining the reduction of Sn4+ cations, as indicated by X-ray photoelectron spectroscopy (XPS). As a result, the assembled ASSLMBs with the LPSI interlayer deliver high initial discharge capacity and remarkable cycling stability. This work provides a new design route for manufacturing high-performance ASSLMBs.
Argyrodites, Li 6 PS 5 X ( X =Cl, Br, I), have piqued the interest of researchers by offering promising lithium ionic conductivity for their application in all-solid-state batteries (ASSBs). However, other than Li 6 PS 5 Cl (651Cl) and Li 6 PS 5 Br (651Br), Li 6 PS 5 I (651I) shows poor ionic conductivity (10 −7 S cm −1 at 298 K). Herein, we present Al-doped 651I with I − /S 2− site disordering to lower activation energy ( E a ) and improve ionic conductivity. They formed argyrodite-type solid solutions with a composition of (Li 6−3 x Al x )PS 5 I in 0⩽ x ⩽0.10, and structural analysis revealed that Al 3+ is located at Li sites. Also, the Al-doped samples contained anion I − /S 2− site disorders in the crystal structures and smaller lattice parameters than the non-doped samples. Impedance spectroscopy measurements indicated that Al-doping reduced the ionic diffusion barrier, E a , and increased the ionic conductivity to 10 −5 S cm −1 ; the (Li 5.7 Al 0.1 )PS 5 I had the highest ionic conductivity in the studied system, at 2.6×10 −5 S cm −1 . In a lab-scale ASSB, with (Li 5.7 Al 0.1 )PS 5 I functioned as a solid electrolyte, demonstrating the characteristics of a pure ionic conductor with negligible electronic conductivity. The evaluated ionic conduction is due to decreased Li + content and I − /S 2− disorder formation. Li-site cation doping enables an in-depth understanding of the structure and provides an additional approach to designing better-performing SEs in the argyrodite system.
Argyrodite-type sulfide solid electrolytes (SEs) Li6PS5X (X = Cl, Br, I) have attracted considerable interest lately by providing a promising lithium-ion transport capability for its application in all-solid-state lithium batteries (ASSLBs). However, other than Li6PS5Cl and Li6PS5Br, Li6PS5I shows poor ionic conductivity of 10–7 S cm–1, which is originated from the I–/S2– site ordered arrangement in its structure. Herein, we report a silicon-doped solid electrolyte Li6+xP1–xSixS5I in this sulfide class, which can remarkably increase the conductivity to 1.1 × 10–3 S cm–1 and lower the activation energy to 0.19 eV as a consequence of changing the structural unit in the argyrodite network. The Li6+xP1–xSixS5I solid electrolytes are employed in ASSLBs with Li(Ni0.8Mn0.1Co0.1)O2 (NCM-811) as cathode and Li metal as an anode to evaluate the electrochemical performance. With x = 0.55, the battery displays an initial discharge capacity of 105 mA h g–1 at a rate of 0.05C and achieves high Coulombic efficiency. Moreover, chemical reactions occurring on the interfaces of the NCM/SE and Li/SE in regard to the degradation of cell performance are also investigated.
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