The Liquid Argon (LAr) calorimeter detector in ATLAS is instrumental in measuring the energy deposits of particles traveling through the detector and for identifying electrons, photons, and jets. As Run 3 introduces higher luminosity, LAr must adapt to the increased radiation and pileup conditions to preserve acceptable trigger thresholds. During the second Long Shutdown, new boards were installed on- and off-detector as a part of the Phase-I upgrade, resulting in a ten fold granularity improvement and increased precision for data sent to the Level-1 Calorimeter (L1Calo) trigger. The Phase-I upgrade is compatible with the planned high-luminosity LHC (HL-LHC). We present an overview of the Phase-I upgrade for LAr and its performance for the start of Run 3.