Abstract
In this work, we report the development of separators coated with hexagonal boron nitride (hBN) to improve the thermal stability of Li-ion batteries (LIBs). Aiming to achieve a synergistic effect of separators and anodes on thermal stability and electrochemical performance, multiwalled carbon nanotubes (MWCNTs) were prepared via plasma-enhanced chemical vapor deposition (PECVD) method and used as potential anode materials for LIBs. The grown MWCNTs were well characterized by using various techniques which confirmed the formation of MWCNTs. The prepared MWCNTs showed a crystalline structure and smooth surface with a diameter of ~9–12 nm and a length of ~10 μm, respectively. Raman spectra showed the characteristic peaks of MWCNTs and BN, and the sharpness of the peaks showed the highly crystalline nature of the grown MWCNTs. The electrochemical studies were performed on the fabricated coin cell with a MWCNT anode using a pristine and BN-coated separators. The results show that the cell with the BN-coated separator in a conventional organic carbonate-based electrolyte and MWCNTs as the anode resulted in a discharge capacity (at 65 °C) of ~567 mAhg−1 at a current density of 100 mAg−1 for the first cycle, and delivered a capacity of ~471 mAhg−1 for 200 cycles. The columbic efficiency was found to be higher (~84%), which showed excellent reversible charge–discharge behavior as compared with the pristine separator (69%) after 200 cycles. The improved thermal performance of the LIBs with the BN-coated separator and MWCNT anode might be due to the greater homogeneous thermal distribution resulting from the BN coating, and the additional electron pathway provided by the MWCNTs. Thus, the fabricated cell showed promising results in achieving the stable operation of the LIBs even at higher temperatures, which will open a pathway to solve the practical concerns over the use of LIBs at higher temperatures without compromising the performance.
Highlights
Due to their extended life cycle and high energy density, lithium-ion batteries (LIBs) are proven to be a standard source of energy for portable electronic devices
We demonstrate the fabrication of a LIBs system based on a BN-coated polypropylene separator and multiwalled carbon nanotubes (MWCNTs) as the anode
XRD, Raman, field emission scanning electron microscopy (FESEM), and high-resolution transmission electron microscopy (HRTEM) studies showed the successful formation of MWCNTs with a crystalline nature and high purity
Summary
Due to their extended life cycle and high energy density, lithium-ion batteries (LIBs) are proven to be a standard source of energy for portable electronic devices. The improvement in the electrolyte wettability and thermal stability was achieved by the coating of ceramic particles, including SiO2 or Al2 O3 , on the surface of polyolefin membranes [20,21,22]. The performance of CNT-based anodes in LIBs could be improved further by introducing defects into CNTs and producing randomly oriented, “spaghetti-like” CNTs. Defects created in CNTs can reduce the energy barrier and facilitate Li+ diffusion into the inner core of the CNTs as well as their adsorption on the walls [29], while, spaghetti-like CNTs could enhance the charge storage capacity due to the large surface area of the nanotubes [28]. The fabricated LIBs will open up the possibility to produce a safe, rechargeable LIBs technology with the capability to operate at elevated temperatures
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