Thin, Flexible Secondary Li-Ion Paper Batteries

TLDR

Thin, flexible energy storage devices are sought for applications such as interactive packaging, RF sensing, and consumer products. This work reports a novel thin, flexible Li‑ion battery that uses paper separators and free‑standing CNT thin films as current collectors. The battery is fabricated by laminating CNT thin films and Li‑ion materials onto a single paper sheet, which serves as both substrate and separator, while the CNT film provides low‑resistance, lightweight, flexible current collection. The resulting battery, only ~300 µm thick, remains mechanically flexible down to <6 mm bending radius and delivers a high energy density of 108 mWh g⁻¹.

Abstract

There is a strong interest in thin, flexible energy storage devices to meet modern society needs for applications such as interactive packaging, radio frequency sensing, and consumer products. In this article, we report a new structure of thin, flexible Li-ion batteries using paper as separators and free-standing carbon nanotube thin films as both current collectors. The current collectors and Li-ion battery materials are integrated onto a single sheet of paper through a lamination process. The paper functions as both a mechanical substrate and separator membrane with lower impedance than commercial separators. The CNT film functions as a current collector for both the anode and the cathode with a low sheet resistance (∼5 Ohm/sq), lightweight (∼0.2 mg/cm2), and excellent flexibility. After packaging, the rechargeable Li-ion paper battery, despite being thin (∼300 μm), exhibits robust mechanical flexibility (capable of bending down to <6 mm) and a high energy density (108 mWh/g).