Ternary Heterostructures With Gradient Built‐In Electric Fields Through Stepwise Screening for Highly Reversible Sodium Storage at Low Temperature

Heterostructure engineering is considered a promising approach to improve sodium storage at low temperatures (LTs). However, the trial‐and‐error fabrication method as well as insufficient interface control dimensions in traditional two‐component heterojunctions result in low efficiency and limited electrochemical performance improvement. Herein, a screening‐driven strategy guided by theoretical descriptors is proposed to identify MoS 2 /MoO 2 as the optimal binary heterostructure for improving sodium storage performance at LTs. Importantly, this result reveals a clear relationship between heterostructure configuration and electrochemical performance, where the work function ( W f ) difference and the resulting charge redistribution regulate Na + storage behavior. Inspired by this understanding, Ti 3 C 2 T x MXene is introduced to construct a multi‐interface system with cascaded W f alignment, establishing a gradient built‐in electric field that overcomes the localized modulation of conventional binary heterostructures. Such heterostructure induces an electron‐enriched region that acts as a Na + reservoir, thereby facilitating efficient Na + storage and transport at LTs. Meanwhile, the multiphase heterointerface optimizes the reaction pathway and mitigates kinetic limitations. Consequently, the MoS 2 /MoO 2 /Ti 3 C 2 T x ternary heterostructure delivers high reversible capacity, excellent rate performance, and robust cycling stability even at −20°C. This work establishes a general and predictive strategy for accelerating the rational design of high‐performance electrodes through the proposed screening framework.