Co-precipitation synthesis of pseudocapacitive λ-MnO2 for 2D MXene (Ti3C2Tx) based asymmetric flexible supercapacitor

Abstract

The rapid growth of wearable/portable electronics imposes a development of flexible, lightweight and highly efficient energy storage devices. In this work, we have synthesized λ-MnO2 nanoplates through one step co-precipitation method and used for flexible asymmetric supercapacitor (SC). The structural, morphological and electrochemical properties of synthesized λ-MnO2 were systematically investigated. The optical and electronic properties of λ-MnO2 were studied using UV–vis spectroscopy and density functional theory (DFT) calculations. The pseudocapacitive λ-MnO2 nanoplates-like electrode showed a maximum specific capacitance of 288.5 F g−1 at the scan rate of 5 mV s−1. To check the practicability, symmetric (λ-MnO2//λ-MnO2) as well as asymmetric (λ-MnO2//AC and λ-MnO2//Ti3C2Tx MXene) SCs were fabricated and their performances were compared. The asymmetric λ-MnO2//Ti3C2Tx MXene SC demonstrated a maximum energy density of 15.5 Wh kg−1 at the power density 1100 W kg−1 along with 86.3 % of capacitive retention after 5000 cycles. Besides, to confirm the suitability of these electrodes for flexible energy storage, a flexible λ-MnO2//Ti3C2Tx asymmetric SC was fabricated using PVA: Na2SO4 gel polymer electrolyte that operated in the potential window of 2 V and supplies high areal energy density of 39.9 μWh cm−2 at a power density of 8586 μW cm−2. Therefore, the λ-MnO2 prepared with a simple and scalable co-precipitation method may play a promising role in flexible energy storage.