Constructing high-energy–density and low-cost batteries is the ultimate pursuit of energy market. However, fast kinetics becomes a critical bottleneck, when the volume and weight parameters to be constantly optimized. Herein, sheet-like SnS/SnS2/rGO heterostructure is designed rationally for kinetics challenges of compact energy storage under high mass loading. Abundant heterogeneous grain boundaries and ideal buffer space are provided by in-situ growth of heterostructures, achieving fast conductivity and structural stability. As anode for sodium ion battery, mass loading of ~3 mg cm−2 SnS/SnS2/rGO exhibit rapid rate capability (460.9 mAh g−1 at 2.0 A g−1) and excellent cycling stability (81% capacity retention for 500 cycles at 1.0 A g−1). The assembled full cell demonstrates a promising energy density of 130.3 Wh kg−1. Importantly, first-principles calculations unravel that interior electric-field induced by heterojunction of phase interfaces can accelerate the charge transfer. Additionally, the anode can also demonstrate good electrochemical performance in potassium-ion batteries. This work provides a new perspective to realize rational structural engineering for high-energy–density devices.