Structurally disordered Ta2O5 aerogel for high-rate and highly stable Li-ion and Na-ion storage through surface redox pseudocapacitance

Electrode materials that combine the high energy density of batteries and the high power density of supercapacitors become an increasing need for current and near-future applications. Ta2O5 delivers a high theoretical capacity but suffers from unsatisfactory rate capabilities. Here we prepare a structurally disordered Ta2O5 nanoparticle aerogel via a nonaqueous sol-gel process followed by CO2 super-critical drying. The resulting aerogels exhibit large surface area, high porosity, fast ion diffusion, and extrinsically pseudocapacitive Li+/Na+ storage behavior (through surface redox reactions). With these merits, when evaluated as anode material for both lithium-ion and sodium-ion half cells (LIBs and NIBs), the Ta2O5 aerogels show excellent rate capabilities (97.0 and 43.7 mA h g(-1) at 5000 mA g(-1) for LIBs and NIBs, respectively) and highly stable cycling performance (20000 cycles at 5000 mA g(-1) and 10000 cycles at 1000 mA g(-1) without obvious capacity fading for LIBs and NIBs, respectively). This work introduces Ta2O5, a typical conversion-type metal oxide without intrinsic pseudocapacitance, as a promising anode material with high extrinsic pseudocapacitance for both LIBs and NIBs, which may open the door to achieve high-rate alkali-ion storage with low synthesis cost for durable microbatteries. (C) 2019 Elsevier Ltd. All rights reserved.