3D‐Printed, Carbon‐Nanotube‐Wrapped, Thermoresponsive Polymer Spheres for Safer Lithium‐Ion Batteries

Abstract

Safety of lithium‐ion batteries (LIBs) has persistently plagued their development, despite widespread commercialization and usage. Thermal runaway is a notorious event where the overheating of the LIB results in a chain of events leading to the catastrophic failure of the device. Here, an in situ safety mechanism that shutdowns the LIB at critical temperatures before the onset of thermal runaway is developed. This is achieved by the deposition of thermal responsive polyethylene (PE) microspheres coated with multiwalled carbon nanotubes (CNTs) on electrodes via 3D printing. Rapid shutdown of LIB full cells under 60 s with ≈1 mg of additive is demonstrated. The mechanism of the shutdown is investigated through post‐mortem analysis of the heat‐treated cells that provides evidence of the formation of an insulating PE film that prevents ionic flow, disabling the LIB. Further, galvanostatic cycling of CNT‐coated PE‐loaded cells is used to demonstrate the advantages of the approach, where the precise and low loading of the conductive additive exhibits no impact on the full cell normal operation.

Design and Manufacture of 3D-Printed Batteries

“…In addition, Yang and co-workers achieved safer LIBs by depositing CNT-wrapped thermoresponsive polyethylene microspheres on the electrodes via FDM, which can form an insulating PE film to prevent ionic flow at high temperatures, thereby rapidly causing a shutdown in the LIBs. 150 Most importantly, FDM enables the precise deposition of a minimal amount of CNT-coated PE microspheres onto electrodes, which simultaneously perform the function as a battery shutdown additive.…”

Additive Manufacturing of Batteries

“…Carbon nanotubes (CNTs) have been widely used to manufacture different devices such as sensors, transistors, supercapacitors, and especially 3D‐printed batteries, due to their high mechanical strength, high chemical stability, large specific surface area, as well as excellent electrical and thermal properties. For instance, Kim et al reported a printed highly conductive CNT microarchitecture ( Figure a) .…”

Thermo‐responsive polymers for thermal regulation in electrochemical energy devices

“…However, to reduce the shutdown time to effectively prevent thermal runaway, the necessary loading of PE microspheres in the electrode shown to be 10.5 mg cm −2 , which leads to visible electrode thickness increase (>50 um) and reduction of the cell energy density. Another example of such electrode design was demonstrated in a 3D‐printable carbon nanotube (CNT) coated PE microspheres 55 as a thermal responsive layer (Figure 5(D)). The CNT‐coated PE microspheres not only exhibit improved electrical and thermal conductivity, but also greatly reduce the loading of PE microspheres required to completely shut down the cells to 1 mg cm −2 (Figure 5(B),(E)).…”

“…(F) Cycling profile of PE‐CNT‐printed cell demonstrating shutdown at 120°C. (reproduced with permission 55 …”