Unlike conventional lithium-ion batteries, all-solid-state lithium metal batteries (ASSLMBs) use solid electrolytes, offering high safety and energy density. However, the rigid solid-solid contact between the lithium metal anode and electrolyte often leads to void formation, contact loss, and failure, especially under low pressure. Current solutions require stack pressures above 5 MPa.

In a study published in Nature Sustainability, research teams led by Prof. HUANG Xuejie from the Institute of Physics of the Chinese Academy of Sciences (CAS), Prof. YAO Xiayin from the Ningbo Institute of Materials Technology and Engineering of CAS, and Prof. ZHANG Heng from Huazhong University of Science and Technology, developed a dynamically adaptive interphase (DAI) that enables stable battery operation under little or even zero external pressure, which is a critical step toward practical high-energy-density ASSLMBs.

The researchers proposed to pre-install mobile anions (iodide, I^-) into the solid electrolyte, which allowed them to migrate during operation and form a dynamic, self-healing interface at the anode. "Current all-solid-state batteries require enormous external pressure. Our solution acts like an automatic regulator, without the need for voluminous external compression systems," Prof. HUANG explained.

Using a LiI-doped sulfide electrolyte (Li_3.2PS₄I_0.2), the researchers demonstrated that iodide ions could migrate to the interface during cycling, forming a LiI layer that filled voids and ensured continuous ion transport. The DAI mechanism effectively eliminated dendrite growth and interfacial degradation. 

A lab-scale cell retained 90.7% of capacity after 2,400 cycles at a current density of 1.25 mA cm⁻². Notably, pouch cells with zero external pressure were assembled with 74.4% of capacity retention after 300 cycles.

"This work resolves the contact-loss problem without complex external mechanical systems. The DAI concept represents a paradigm shift in interfacial design and opens up a new pathway toward sustainable, high-energy, and practical solid-state batteries," said Prof. WANG Chunsheng, an expert in battery technologies from the University of Maryland.