Atomic-Level Shock-Absorbing Spring: Curvature-Driven Mechanical Homogenization of Hard Carbon for High-Stability Sodium-Ion Batteries.

Abstract

In sodium-ion batteries, the insufficient cycling stability of hard carbon anode stems from the physical essence of electrochemical-mechanical coupling failure. Herein, a highly heterogeneous state with extensive weak regions was transformed into a rigid skeleton by adapting a metal-catalyzed carbon structure reconfiguration strategy. Crucially, the introduction of long-range ordered curvature features establishes a pool of atomic-level shock-absorbing spring systems within the carbon network. It not only reversibly accommodates mechanical strain along the <i>z</i>-axis direction but also homogenizes the localized stress of the <i>xy</i> plane. As the balanced enhancement of mechanical properties was achieved across multiple dimensions, electrochemical tests confirmed that the architected rigid framework shows no capacity degradation after 1000 cycles at a current density of 2 A g^-1. Thus, our study provides a new design paradigm for developing high-performance anodes via a mechanical homogenization design of hard carbon.