Eliminating the “Dead By‐Product” Effect Realizes Powerful Vanadium‐Based Zinc‐Ion Batteries: An Overlooked Case

Abstract The accumulation of inactive by‐products caused by the parasitic side reaction on cathode side is an overlooked question leading to performance degradation of zinc‐ion batteries. In this research, taking the MnV ₂ O ₄ as a model, an amorphous carbon interphase is proposed as a pre‐implanted cathode‐electrolyte interphase (CEI) to design ultrafast‐kinetics MnV ₂ O ₄ @C cathode. It is noted that such CEI integrates hydrophobic and conductive characteristics, contributing to dissolution shielding, continuous interfacial conductive channel, and thus preventing inactive by‐product accumulation on the cathode interface. Unexpectedly, such electrode shows superior storage performance at a wide temperature range of −20–55 °C. It can deliver a specific capacity of 253.3 mAh g ⁻¹ at the high current density of 10 A g ⁻¹ even after 8000 cycles. Moreover, a high specific capacity of 393.8 mAh g ⁻¹ (0.1 A g ⁻¹ ) can be retained after 300 cycles at 55 °C, as well as 205.1 mAh g ⁻¹ at the condition of −20 °C and 5 A g ⁻¹ . Beyond that, flexible solid‐state zinc‐ion batteries based on MnV ₂ O ₄ @C cathode with excellent wide temperature performance are demonstrated. This work highlights the importance of eliminating the dead by‐product effect to design advanced cathode materials for zinc‐ion batteries.