In this work, we demonstrate the concept of localized high-concentration electrolytes in PFAS-free LFP || Li cells by directly comparing LiFSI-DME electrolytes (lithium bis(fluorosulfonyl)imide in 1,2-dimethoxy ethane) with two aromatic diluents –- toluene and its fluorinated analogous m-fluorotoluene (mFT). Liquid FT-Raman spectroscopy confirmed the presence of contact ion pairs and aggregates in both LHCE-toluene and LHCE-mFT and the absence of uncoordinated DME molecules. Longterm cycling in LFP || Li cells show outstanding capacity retention for LHCE-toluene of 81% SOH after 3000 cycles. Surprisingly, the LHCE-mFT shows SOH <20% after 420 cycles which is still better than the state-of-the-art electrolyte for LIBs. Further investigations of the Li surface by scanning electron microscopy and time-of-flight secondary ion mass spectrometry (ToF-SIMS) showed minor differences between the Li electrodes cycled with LHCE-toluene or LHCE mFT. Recovery of the electrolyte after 20 cycles and subsequent LC-MS-MS investigation revealed an electrochemically induced reaction mechanism between mFT and FSI- leading to conductive salt depletion and cell failure. With this study we successfully demonstrated that Li metal electrodes can reach up to 3000 cycles in a liquid electrolyte based on the concept of LHCE with a PFAS-free cell setup. Additionally, small structural differences of the diluents can lead to major effects on the electrochemical performance even though the diluent is often described to play a minor role on the performance.