Battery systems are provided that include a plurality of modules positioned within an enclosed space (e.g., a room, data center or storage system), wherein at least one of the modules includes a plurality of lithium ion cells and thermal insulator(s) positioned between adjacent lithium ion cells, and wherein the battery systems offer a requisite level of safety by scaling the system such that the internally available volume of the enclosed space (measured in liters) is in the range of about 39±5 times and 80±5 times the amp-hour (Ah) capacity of lithium ion cell(s) positioned therewithin, and associated methods for safe deployment of battery systems in enclosed spaces. The relevant lithium ion cell(s) for determination of Ah capacity is/are the lithium ion cell(s) that is/are thermally insulated relative to adjacent lithium ion cell(s).