Seongjae Ko, Yuki Yamada, Atsuo Yamada
The energy stored in batteries is defined as the product of capacity and voltage. Because the capacity is reaching the theoretical limit of the Li-ion battery concept, increasing the voltage from the current 3.8 to 5 V is the major target to achieve high-energy densities. Various approaches have been taken to address the issues of 5 V Li-ion batteries, including the oxidative decomposition of the electrolyte at high voltages. However, their stable charge-discharge operation has not been achieved, suggesting the presence of an unknown yet essential issue that must be solved. Here, we unveil the intercalation of counter anion of an electrolyte into cathode conductive carbon as an overlooked critical issue. On this basis, we design a specific electrolyte that blocks the anion intercalation and demonstrate the unprecedented stable charge-discharge cycling of 5 V Li-ion batteries. This finding offers a fundamental basis for developing advanced Li-ion batteries with high-energy densities.