Toward\nMultifunctional Electronics: Flexible NBT-Based\nFilm with a Large Electrocaloric Effect and High Energy Storage Property

Abstract

Advances in smart\nand wearable devices are driving innovations\nin multifunctional flexible materials at a tremendous pace. Here,\ndrawing support from the unique flexible fluorophlogopite mica platform,\nwe present a promising all-inorganic bendable Mn-modified 0.65­(0.94Na_0.5Bi_0.5TiO₃–0.06BaTiO₃)–0.35SrTiO₃ (NBBST) film with dual use in electrocaloric\n(EC) refrigeration and energy storage via a cost-effective transfer-free\nprocess. An appreciable room-temperature EC effect with adiabatic\ntemperature change of 12 K and isothermal entropy of 18 J K^–1 kg^–1 was realized in the NBBST film, which benefits\nfrom the large change in dipolar ordering near depolarization temperature.\nAlso, the film exhibits a broad operating temperature span over 25\n°C because of its relaxor feature. Most importantly, the film\ncan maintain a high EC performance either under bending deformation\nat 5 mm radius or after undergoing 10⁴ bending–unbending\ncycles. Meanwhile, the flexible NBBST film possesses good energy storage\nproperty with a recoverable energy density of 56 J cm^–3 and an efficiency of 66%. This is the first example of a lead-free\nall-inorganic multifunctional film capacitor toward the flexible EC\nrefrigeration and energy storage devices. This work shows bright prospects\nin the emerging flexible e-market.