title: Ordered Mesoporous Titanium Nitride as a Promising Carbon-Free Cathode for Aprotic Lithium-Oxygen Batteries.
abstract: Despite the extraordinary gravimetric energy densities, lithium-oxygen (Li-O2) batteries are still facing a technological challenge; limited round trip efficiency leading to insufficient cycle life. Recently, carbonaceous electrode materials were found to be one of the primary origins of the limited cycle life, as they produce irreversible side products during discharge. A few investigations based on noncarbonaceous materials have demonstrated largely suppressed accumulation of irreversible side products, but such studies have focused mainly on the materials themselves rather than delicate morphology control. As such, here, we report the synthesis of mesoporous titanium nitride (m-TiN) with a 2D hexagonal structure and large pores (>30 nm), which was templated by a block copolymer with tunable chain lengths, and introduce it as a stable air-cathode backbone. Due to the well-aligned pore structure and decent electric conductivity of TiN, the battery reaction was quite reversible, resulting in robust cycling performance for over 100 cycles under a potential cutoff condition. Furthermore, by protecting the Li metal with a poreless polyurethane separator and engaging a lithium iodide redox mediator, the original capacity was retained for 280 cycles under a consistent capacity condition (430 mAh g-1). This study reveals that when the appropriate structure and material choice of the air-cathode are coupled with an advanced separator and an effective solution-phase redox mediator, the cycle lives of Li-O2batteries can be enhanced dramatically.
authors.affiliation: Graduate School of Energy, Environment, Water, and Sustainability (EEWS) and KAIST Institute NanoCentury, Korea Advanced Institute of Science and Technology (KAIST) , 291 Daehakro, Yuseong-gu, Daejeon 34141, Republic of Korea.
authors.forename: Byung Gon
authors.initials: BG
authors.lastname: Kim
authors.forename: Changshin
authors.initials: C
authors.lastname: Jo
authors.affiliation: Graduate School of Energy, Environment, Water, and Sustainability (EEWS) and KAIST Institute NanoCentury, Korea Advanced Institute of Science and Technology (KAIST) , 291 Daehakro, Yuseong-gu, Daejeon 34141, Republic of Korea.
authors.forename: Jaeho
authors.initials: J
authors.lastname: Shin
authors.forename: Yeongdong
authors.initials: Y
authors.lastname: Mun
authors.forename: Jinwoo
authors.initials: J
authors.lastname: Lee
authors.affiliation: Graduate School of Energy, Environment, Water, and Sustainability (EEWS) and KAIST Institute NanoCentury, Korea Advanced Institute of Science and Technology (KAIST) , 291 Daehakro, Yuseong-gu, Daejeon 34141, Republic of Korea.
authors.forename: Jang Wook
authors.identifier: 0000-0001-8783-0901
authors.initials: JW
authors.lastname: Choi
keywords: mesoporous structure; poreless separator; redox mediator; self-assembly; titanium nitride