On theory energy,  loss can’t be avoided during store. Its proper electrochemistry construction makes the losing unavoidable. Self-discharge is the best-known causation. Generally,  this has to do with the electrolytic solubility of the positive electrode material or its thermodynamic instability (easy spontaneous decomposition). Self-discharge in rechargeable batteries is particularly high in comparison to the primary battery. Furthermore,  every month a battery self-discharge rate is various depending on the system. It changes in the range of 10%-35%. Primary battery self-discharge is considerably lower . At room temperature it may even be below 2%. However, various processes take place in parallel with this which leads to an increase of the battery’s internal resistance during storage. These processes lead to a reduction in load capability. However energy loss is more noticeable at relatively high discharge current. The below table lists the self-discharge approximation under normal storage conditions:

Type of Self-discharge: Alkali manganese, MnO2/Zn, cycloidal 2%;  Zinc carbon, MnO2/Zn, cycloidal  4%;   Li-ion(LiMnO2), cycloidal and button cell Approx 1%;   Ni-MH/Ni-Cd cell , 35% .