The electrochemical stability window (ESW) is a fundamental consideration for choosing polymers as solid electrolytes in lithium-ion batteries. The inherent morphological and chemical intricacy of the polymer matrix and complicated interactions with lithium salts make the theoretical and experimental determination of polymer electrolytes ESWs difficult. Considering the dominant role of the polymer matrix in governing the ESW of polymer electrolytes, in this work, we propose a computational procedure to estimate ESW of the polymer matrix using first-principles density functional theory computations and classical molecular dynamics simulations. Taking polymer diversity and its utilization in Li-ion batteries into account, 10 model polymer matrix were investigated, namely, polyethylene, polyketone, polyethylene oxide, polypropylene oxide, polyvinyl alcohol, polycaprolactone, poly(methyl methacrylate), polyethyl acrylate, polyvinyl chloride, and polyvinylidene fluoride. Utilizing an increasingly complex hierarchy of models (i.e., the single-chain, ordered and disordered slabs), the role of polymer chemistry and the morphological complexity in determining ESW have been elucidated. We found that the former can modify the ESW by introducing different bonding/anti-bonding orbitals, while the latter can degrade the band edges, resulting in a decrease of ESW widths (i.e., the single-chain > ordered slabs > disordered slabs). Furthermore, a good agreement between computed ESW of disordered slabs and experimental values has been achieved, showing our computational procedures (DFT coupled with MD simulations) can successfully predict established ESW values of polymer electrolytes. Additionally, the proposed computational procedure and models lay the groundwork to systematically investigate impacts of lithium salts and electrode-electrolyte interfaces on the ESW parameters. All these contributions can assist the rational design of novel polymer electrolytes with desired ESW values.