Ether based electrolytes are essential to enable stable lithium metal batteries. Low concentration electrolyte composed with 1M lithium bis(fluorosulfony)imide (LiFSI) and 1,2-dimethoxyethane (DME) is alluring due to low viscosity and superior ion conductivity. Although lower salt concentration is desirable to reduce cost, it is believed that low concentration ether electrolyte cannot sustain more than 4V, diminishing their application in high-voltage batteries. Here, we report that the measured electrochemical stability window (ESW) of low concentration 1M LiFSI/DME electrolyte is largely affected by working electrode (WE). The measured ESW extends to ~4.4 V with aluminum WE compared with less than 4V with stainless steel WE. Furthermore, we demonstrate that Li||LiNi_0.8Co_0.1Mn_0.1O₂ battery can operate in 1M LiFSI/DME electrolyte at 4.2 V with long calendar life (97% capacity retention after 100 cycles) under high areal capacity (2.5 mAh/cm²) and low N/P ratio (~2:1). This work opens avenue for low concentration electrolyte applying in high-energy and cost-efficiency batteries.