Time Release of Encapsulated Additives for Enhanced Performance of Lithium-Ion Batteries

Abstract

Time release of encapsulated vinylene carbonate (VC) from microcapsules in Li-ion batteries is demonstrated to enhance the rate performance without sacrificing capacity retention. VC-filled microcapsules are successfully prepared by the solvent exchange method that allows VC to diffuse through the microcapsule shell wall at an elevated temperature. The concentration of VC added directly to the electrolyte in a pouch cell (2 wt %) significantly decreases after the first cycle at C/10-rate. In pouch cells that contain 5 wt % VC-filled microcapsules, the concentration of VC increases from 0 to 3 wt % over the first cycle because of the diffusion of microencapsulated VC in the electrolyte. Electrochemical impedance spectroscopy, rate capability, and long-term cycling tests are conducted for pouch cells with VC additives (0, 2, and 5 wt %) and VC microcapsules (5 wt %). Pouch cells with both 5 wt % VC additive and microencapsulated VC show improved capacity retention over 400 cycles at 1 C-rate compared to the cells without VC additive. When VC is added directly, the high initial concentration leads to increased interfacial resistance and decreased rate capability. By contrast, time release of microencapsulated VC by diffusion through microcapsules increases the discharge capacity 2.5 times at 5 C-rate compared to the direct VC addition to the electrolyte.

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

“…[ 30 ] When microcapsules are incorporated in Li‐ion batteries, the polymeric shell‐wall is selected to physically insulate the encapsulated additive from electrode or electrolyte and prevents unwanted interactions between these components. [ 5,6,28 ] Upon external trigger (time, heat, chemical trigger, or mechanical damage), microcapsules release the payload and deliver desirable additives into the battery environment.…”

“…Adapted with permission. [ 5 ] Copyright 2017, American Chemical Society. b) Autonomous shutdown of battery upon thermal runaway with thermo‐responsive microcapsules.…”

“…[ 3,4 ] In contrast, autonomous strategies improve battery performance through site‐specific triggered responses to mitigate damage, restore electrochemical function, or prevent thermal runaway. [ 5–8 ] These strategies have been implemented in a broad range of electrochemical systems and complement on‐going materials development efforts.…”

“…[ 8,21–26 ] Autonomous delivery of battery additives during the cycling process helps to improve capacity retention over time (summarized in Table S1 in Supporting Information). [ 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 ]…”