Although lithium-ion battery technology has already been successfully developed and used in modern society for efficient energy storage over a long period of time, strategies are still being sought to address the problem of the inevitable shortening of cell lifetime caused by degradation processes. One of the key contributors is the loss of lithium inventory, which is irreversibly consumed primarily through the formation of interphase layers on the cathode and anode and through reactions occurring on them. This thesis investigates a strategy for compensating this loss by means of microcapsules that, upon thermal activation, release a sacrificial lithium salt from their core. The core of the microcapsules contains lithium squarate, enclosed by a porous SiO2 shell, which is in turn surrounded by a thermo-responsive polymer responsible for the time-controlled release of the salt at elevated temperature. During electrode preparation, the microcapsules were incorporated into the cathode composite, based on lithium manganese iron phosphate (LMFP), at a mass fraction of 2 wt.%, while a natural graphite electrode was used as the anode. Compared with the related lithium iron phosphate (LFP), LMFP enables cell operation at a higher average voltage, which consequently results in a higher energy density. Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) were used to characterize the cathode composite. Electrochemical characterization of both half-cells and full cells was performed using the galvanostatic cycling with potential limitation (GCPL) method. The strategy was qualitatively evaluated by comparing different test regimes, and the effect of the anode-to-cathode capacity ratio (N/P) following thermal activation was also briefly presented.
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