Cathode-doped sulfide electrolyte strategy for boosting all-solid-state lithium batteries

Abstract

• FeS 2 cathode was used as doping agent for Li 7 P 3 S 11 -type glass–ceramic electrolyte. • The highest lithium-ion conductivity of 2.22 mS cm −1 was achieved by suitable FeS 2 doping. • The crystallization degree in the designed electrolyte was evaluated by solid-state NMR. • The cathode-doped electrolyte strategy reduced cathode/electrolyte interfacial resistance. • The fabricated all-solid-state batteries presented higher initial capacity and better cycling stability. Low lithium ionic conductivity of the solid-state electrolyte and large interface resistance have hampered the application of all-solid-state lithium batteries. Although various methods have been proposed to address these challenge, a high-efficient method still needs for all-solid-state batteries. For the first time that Pyrite (FeS 2 ) cathode is used as doping agent for Li 7 P 3 S 11 -type glass–ceramic electrolyte that could simultaneously improve the ionic conductivity and decrease the interfacial resistance between FeS 2 cathode and electrolyte. A new series of Li 7 P 3 S 11 -type glass–ceramic electrolytes (x = 0, 0.5, 1, 2) are prepared by high energy ball milling method, and the 99.5(70Li 2 S–30P 2 S 5 )–0.5FeS 2 glass–ceramic electrolyte shows a high lithium ionic conductivity, up to 2.22 mS cm −1 at room temperature. Solid-state NMR studies found that the presence of FeS 2 doping could controllably adjust the crystallisation portions in glass–ceramic electrolyte, thus achieving the superior ionic conductivity. Moreover, the fabricated FeS 2 /99.5(70Li 2 S–30P 2 S 5 )–0.5FeS 2 /Li–Ln cell exhibited lower resistance. As a result, the novel all-solid-state lithium battery presented a higher initial capacity of 543 mAh g −1 at the current density of 0.03 mA cm −2 and also better cycling stability (462 mAh g −1 after 20 cycles) than the counterpart. The proposed cathode-doped electrolyte strategy not only figure out the key factors that determine the ionic conductivity of the glass–ceramic electrolyte and cathode/electrolyte interfacial resistance, and also provides an efficient route for design electrode configuration of high-performance solid-state lithium batteries.