Core–Shell Microcapsules Containing Flame Retardant Tris(2-chloroethyl phosphate) for Lithium-Ion Battery Applications

Abstract

Flame retardant tris(2-chloroethyl phosphate) (TCP) is successfully encapsulated in core–shell poly(urea-formaldehyde) microcapsules by in situ polymerization. The microcapsules are electrochemically stable in lithium-ion (Li-ion) battery electrolytes and thermally stable to ca. 200 °C. Thermal triggering of these microcapsules at higher temperatures ruptures the shell wall, releasing the liquid core (flame retardant), and NMR spectroscopy confirms the presence of the flame retardant in the electrolyte solution. Li-ion pouch cell experiments demonstrate that microencapsulation of TCP and its incorporation into the battery electrolyte provide latent fire retardants that improve battery safety while maintaining inherent battery performance and cycling capability.

Hydrocolloids: Nova materials assisting encapsulation of volatile phase change materials for cryogenic energy transport and storage

“…Capsules have long enjoyed their popularity in drug carrier design, [14][15][16] fragrance retention, [17][18][19] and self-healing materials, [20][21][22] while seeking niche application frontiers in reaction scavengers, 23 lithium-ion batteries, [24][25][26][27] fuel cells, 28 carbon capture, 29 and thermal energy storage. [30][31] In most cases, the active ingredients are non-volatile liquids or even solids at room temperature, 32 which extenuates the leakage problem and endorses a diverse range of synthesis routes.…”

Autonomous Strategies for Improved Performance and Reliability of Li‐Ion Batteries

“…reported the encapsulation of tris(2‐chloroethyl phosphate) (TCP) in poly(urea‐formaldehyde) (pUF) microcapsules and alleviated the capacity degradation due to the addition of TCP in the battery electrolyte. [ 29 ] Encapsulation of flame retardants in thermo‐responsive microcapsules is a promising approach to improve battery safety.…”

“…Responsive microcapsules are triggered by changes in many different environmental stimuli. [ 30,55 ] To date, only thermal triggers, [ 28,29 ] time release, [ 5 ] and damage‐induced rupture and release [ 6,43 ] have been demonstrated in the battery environment. Chemically or electrically triggered‐release of additives has not been reported, despite the potential advantages.…”

“…Microcapsules for battery applications are typically prepared by emulsion‐based techniques. The encapsulation of hydrophobic payloads such as flame retardants, [ 28,29 ] solvent suspensions of conductive particles, [ 43 ] and precursors for cathode passivation [ 6 ] is easily achieved by emulsification polymerization. In contrast, microcapsules with core materials such as VC, FEC cannot be directly prepared by emulsion‐based techniques due to the miscibility of core materials with both oil phase and water phase.…”

“…[ 5,6 ] In extreme conditions, autonomous strategies allow batteries to self‐shutdown or self‐extinguish in case of thermal runaway or ignition. [ 7,27–29 ]…”