The lithium salt, bis(oxalato)borate, LiBC4O8 (LiBOB), is one of the most important Li salts which are explored today in connection with R & D of novel, high energy density rechargeable Li batteries. The thermal stability of this salt in the temperature range of 40–350°C was rigorously studied by accelerating rate calorimetry (ARC), differential scanning calorimetry (DSC), and thermal gravimetric analysis (TGA). XRD, FTIR, SEM, and ICP were used to analyze the products of its thermal decomposition reactions. Studies by DSC and pressure measurements during ARC experiments with LiBOB detected an endothermic reaction with an onset at ∼293°C, involving a complete irreversible decomposition of the LiBOB in which gaseous products are formed. In the first stage, Li2C2O4 (crystalline), B2O3 (glass), CO and CO2 gases are formed in both confined and open volumes. The next (final) stage in the thermal reactions is an irreversible formation of lithium triborate LiB3O5 (glass).