Mesoporous LixMn2O4 Thin Film Cathodes for Lithium-Ion Pseudocapacitors

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• 作者：Benjamin K. Lesel ; Jesse S. Ko ; Bruce Dunn ; Sarah H. Tolbert
• 刊名：ACS Nano
• 出版年：2016
• 出版时间：August 23, 2016
• 年：2016
• 卷：10
• 期：8
• 页码：7572-7581
• 全文大小：521K
• 年卷期：0
• ISSN：1936-086X

文摘

Charge storage devices with high energy density and enhanced rate capabilities are highly sought after in today’s mobile world. Although several high-rate pseudocapacitive anode materials have been reported, cathode materials operating in a high potential range versus lithium metal are much less common. Here, we present a nanostructured version of the well-known cathode material, LiMn₂O₄. The reduction in lithium-ion diffusion lengths and improvement in rate capabilities is realized through a combination of nanocrystallinity and the formation of a 3-D porous framework. Materials were fabricated from nanoporous Mn₃O₄ films made by block copolymer templating of preformed nanocrystals. The nanoporous Mn₃O₄ was then converted via solid-state reaction with LiOH to nanoporous Li_xMn₂O₄ (1 < x < 2). The resulting films had a wall thickness of ∼15 nm, which is small enough to be impacted by inactive surface sites. As a consequence, capacity was reduced by about half compared to bulk LiMn₂O₄, but both charge and discharge kinetics as well as cycling stability were improved significantly. Kinetic analysis of the redox reactions was used to verify the pseudocapacitive mechanisms of charge storage and establish the feasibility of using nanoporous Li_xMn₂O₄ as a cathode in lithium-ion devices based on pseudocapacitive charge storage.