Low-Pressure and Durable Interface Design for Sulfide All-Solid-State Battery
| Jerry Huang
On April 21, 2026, Academician Xueliang Sun and Changhong Wang's team at Eastern Institute of Technology, Ningbo published a research article entitled "Ionic Elastomer Interface for Low-Pressure and Durable All-Solid-State Batteries" in Advanced Energy Materials. This study proposes an ionically conductive elastomer interface strategy that constructs a composite interface combining mechanical flexibility with ionic conductivity, enabling stable operation of all-solid-state batteries (ASSBs) under low external pressure. The designed ionic elastomer, composed of SIBS (styrene-isobutylene-styrene block copolymer) and LiTFSI-G3 (lithium bis(trifluoromethanesulfonyl)imide with triglyme), exhibits outstanding comprehensive performance: a room-temperature ionic conductivity of 0.3 mS cm⁻¹, a composite electrolyte conductivity as high as 5.23 mS cm⁻¹, a low elastic modulus of 29.8 MPa, and excellent thermal stability (≥400 °C). Leveraging this interface design, the battery delivers an initial capacity of 200 mAh g⁻¹ at a low stack pressure of only 5 MPa and achieves stable cycling for over 700 cycles at 1C rate. Thanks to researchers’ efforts to bring a key solution about the interface treatment in sulfide-based ASSB.
Abstract All-solid-state batteries (ASSBs) hold significant promise as next-generation energy storage systems due to their high energy density and intrinsic safety. However, their practical deployment is impeded by the need for high external pressure (typically tens of megapascals) to maintain solid–solid interfacial contact and ensure long-term cycling stability. Here, we report an ionic elastomer specifically designed to enable stable ASSB operation under substantially reduced stack pressure. The elastomer combines a mechanically flexible polymer matrix with an ionically conductive phase, delivering high room-temperature ionic conductivity (0.3 mS cm−1), a low elastic modulus (29.8 MPa), excellent thermal stability (≥400°C), and strong chemical compatibility with sulfide-based solid-state electrolytes (SSEs). When integrated with sulfide SSEs, the composite exhibits a remarkable room-temperature ionic conductivity of 5.23 mS cm−1. Incorporation of this composite into ASSBs with high-nickel cathodes (Ni ≥ 90%) yields an initial capacity of 200 mAh g−1 at 0.05C and outstanding cycling stability over 700 cycles at 1C under a low stack pressure of just 5 MPa. This ionic-elastomer strategy mitigates electrochemical-mechanical degradation, eliminates the high-pressure requirement, and offers a scalable pathway toward practical, durable ASSBs technologies.
Let’s take a look at the current solid-solid interface challenges in sulfide-based ASSB:italic text The solid-solid interface problem in sulfide-based all-solid-state batteries fundamentally stems from the inability of solids to "wet" and conformally adhere to one another the way liquid electrolytes do, resulting in poor contact, excessive interfacial reactions, and crack formation. This represents the most formidable hurdle in transitioning sulfide ASSBs from the laboratory to mass production. The specific challenges can be categorized into three classes: physical contact deficiency, chemical side reactions, and mechanical failure.
Poor Physical Contact — "Open Circuit" of Ion Pathways • Point contact: Both cathode and electrolyte particles are rigid solids; after mixing, they can only form point-to-point contact with abundant interfacial voids, leading to obstructed lithium-ion transport channels and high interfacial impedance. • No self-healing capability: In liquid batteries, the electrolyte flows to fill gaps as electrodes expand and contract; once a solid-solid interface detaches, the disconnection is permanent.
Abundant Chemical Side Reactions — Interface "Poisoning" • Cathode side: Under high voltages, sulfide electrolytes are prone to oxidation and react with cathode materials to form low-conductivity interfacial layers (e.g., Li₂S, P₂Sₓ). A "space-charge layer" also forms — lithium ions are depleted at the interface, something like a sudden speed-limit zone on a highway, causing a dramatic increase in impedance. • Anode side: In contact with lithium metal, reduction reactions readily occur, producing high-impedance byproducts and promoting lithium dendrite growth along grain boundaries that can penetrate the electrolyte and cause short circuits.
Mechanical Failure — "Disintegration" After Cycling • Volume changes: During charge and discharge, electrode materials undergo expansion and contraction (silicon anodes can swell by over 300%). After hundreds of cycles, the solid-solid contact surfaces crack and delaminate, leading to a diving in capacity. • Requirement for external pressure: In the laboratory, interfacial contact can be forcibly maintained by applying tens to hundreds of megapascals of external stack pressure. However, such pressurization systems cannot be deployed in vehicles. Achieving stable contact under zero or low pressure during mass production remains a formidable engineering challenge.
Notably, sulfide electrolytes are extremely sensitive to moisture — exposure to water releases toxic H₂S gas. This necessitates that the entire manufacturing process be conducted under inert atmosphere or ultra-low dew-point conditions, further compounding the difficulty of interface engineering.
Reference https://doi.org/10.1002/aenm.202504652