Benefiting from the distinctive ordering degree and local microstructure characteristics, hard carbon (HC) is considered as the most promising anode for sodium-ion batteries (SIBs). Unfortunately, the low initial Coulombic efficiency (ICE) and limited reversible capacity severely impede its extensive application. Here, a homogeneous curly graphene (CG) layer with a micropore structure on HC is designed and executed by a simple chemical vapor deposition method (without catalysts). CG not only improves the electronic/ionic conductivity of the hard carbon but also effectively shields its surface defects, enhancing its ICE. In particular, due to the spontaneous curling structural characteristics of CG sheets (CGs), the micropores (≤ 2 nm) formed provide additional active sites, increasing its capacity. When used as a sodium-ion battery anode, the HC-CG composite anode displayed an outstanding reversible capacity of 358 mAh·g⁻¹, superior ICE of 88.6%, remarkable rate performance of 145.8 mAh·g⁻¹ at 5 A·g⁻¹, and long cycling life after 1000 cycles with 88.6% at 1 A·g⁻¹. This work provides a simple defect/microstructure turning strategy for hard carbon anodes and deepens the understanding of Na⁺ storage behavior in the plateau region, especially on the pore-filling mechanism by forming quasi-metallic clusters.

High-entropy oxides (HEOs) are a new class of emerging materials with fascinating properties (such as structural stability, tensile strength, and corrosion resistance). High-entropy oxide coated Ni-rich cathode materials have great potential to improve the electrochemical performance. Here, we present a facile self-ball milling method to obtain (La_0.2Nd_0.2Sm_0.2Eu_0.2Gd_0.2)₂Zr₂O₇ (HEO) coated LiNi_0.8Co_0.1Mn_0.1O₂ (NCM811). The HEO coating endows NCM811 with a stable surface, reduces the contact with the external environment (air and electrolyte), and inhibits side reactions between cathode and electrolyte. These favorable effects, especially when the coating amount is 5 wt%, result in a significant reduction of the battery polarization and an increase in the capacity retention from 57.3% (NCM811) to 74.2% (5HEO-NCM811) after 300 cycles at 1 C (1 C = 200 mA·h·g^-1). Moreover, the morphology and spectroscopy analysis after the cycles confirmed the inhibitory effect of the HEO coating on electrolyte decomposition, which is important for the cycle life. Surprisingly, HEO coating reduces the viscosity of slurry by 37%-38% and significantly improves the flowability of the slurry with high solid content. This strategy confirms the feasibility of HEO-modified Ni-rich cathode materials and provides a new idea for the design of high-performance cathode materials for Li-ion batteries.