Xinhua News Agency recently reported a breakthrough research published in Nature Sustainability by Huang Xuejie of the Institute of Physics of the Chinese Academy of Sciences, Yao Xiayin of Ningbo Institute of Materials, Zhang Heng of Huazhong University of Science and Technology and other teams.

The core of this study proposes a novel design strategy called "Dynamic Adaptive Interface (DAI)", which activates anion migration in solid-state electrolytes to spontaneously form a protective layer at the interface during battery cycling, solving the problem of interface contact failure in solid-state batteries.

The soft pack battery based on this strategy has achieved stable operation under "zero external pressure" conditions for the first time, providing a disruptive new idea for the industrialization path of all solid state batteries.

One of the core pain points in the industrialization of all solid state batteries is the failure of the solid solid contact between the lithium metal negative electrode and the rigid electrolyte. The traditional approach relies on applying extremely high external pressure to maintain contact, but this is extremely difficult to sustain in practical battery systems.

This study proposes the "Dynamic Adaptive Interphase (DAI)" strategy. The core mechanism is to subvert the traditional electrolyte in which anions are "fixed and immobile". Through material design, anions (such as I ⁻) have controllable migration ability under electric field drive.

During the lithium stripping process, these migratory anions will move to the interface and combine with lithium ions to form a dynamic, dense, and stable interface layer in situ (such as a LiI rich layer).

The research team vividly likened it to an "octopus tentacle", emphasizing its unique role in dynamic adaptation. This interface layer can actively fill the pores generated by lithium volume changes like an octopus tentacle, maintaining tight interface contact in real time, thereby eliminating dependence on high external pressure.

Why choose iodine doped sulfide electrolyte?

To verify the feasibility of the DAI strategy, the research team screened through high-throughput calculations and found that iodide ion (I ⁻) is a candidate anion with suitable migration ability. They chose Li ∝ ₂PS₄I₀. ₂ (iodine doped sulfide electrolyte) as a model system for implementing and validating the DAI concept.

The experimental data proves the success of this strategy:

Clear interface contrast: Batteries using traditional Li ∝ PS ₄ electrolytes exhibit micrometer sized pores at the interface, leading to failure; And using Li ∝ ₂PS₄I₀. The ₂ battery formed a uniform LiI rich interface layer of about 5 μ m in situ, with intact contact and no dendrites.

Significant performance improvement: The full battery based on DAI strategy has a capacity retention rate of up to 90.7% after 2400 cycles at 1.25 mA · cm ⁻ ²; The soft pack battery has been cycled 300 times under zero external pressure, and the capacity retention rate still reaches 74.4%.

The industrial significance of this research is significant, as it provides a completely new approach. The design of future solid-state electrolytes should not only focus on optimizing the conduction of lithium ions, but also consider the contribution of anion migration ability to interface self-healing.

Although Li ∝ ₂PS₄I₀. As a "model material" here, the success of the DAI strategy undoubtedly provides a stronger theoretical basis and experimental verification for the iodine (halogen) doped/composite sulfide electrolyte route.

The iodine sulfide electrolyte based on the DAI approach is expected to become a highly promising industrialization direction.

It is worth noting that the iodine sulfide electrolyte industry chain has a forward-looking layout.

Dangsheng Technology has disclosed the construction of a small-scale trial production line for sulfide solid electrolytes with a capacity of several tons. The solid electrolyte of chlorinated iodine composite sulfide developed by it is said to have achieved stable preparation and has the ability to be supplied on a large scale.