Rubber-like polymer boosts solid-state battery life and performance, Korean researchers say

Korea Research Institute of Chemical Technology solves internal cracking problem in sulfide-based all-solid-state batteries

Student researcher Kim Ju-hyung (from left), principal researcher Kim Dong-wook and student researcher Bae Hyo-won, who conducted the research at the Korea Research Institute of Chemical Technology. [Korea Research Institute of Chemical Technology]

Korean researchers have developed a new material that can significantly extend the lifespan and stability of all-solid-state batteries — a technology seen as key to eliminating the fire risks associated with conventional lithium-ion batteries.

A team led by Kim Dong-wook of the Korea Research Institute of Chemical Technology, working with professors Hwang Sung-joo of Yonsei University and Park Ho-seok of Sungkyunkwan University, said Sunday it had developed a technique that embeds an "elastic ion-conducting polymer" inside sulfide-based all-solid-state batteries to reduce cracking and interfacial damage during charging and discharging, thereby improving battery life.

The global all-solid-state battery market is projected to grow from $149.43 million in 2026 to approximately $3.36 billion by 2034, at a compound annual growth rate of 47.57 percent. Despite considerable progress, commercialization remains in its early stages, with most solid-electrolyte batteries still at the prototype or pilot production phase.

Sulfide-based all-solid-state batteries are particularly prone to internal cracking because their rigid solid electrolyte sits in direct contact with the electrodes. Repeated charging and discharging causes the electrodes to expand and contract, and the accumulated volume changes generate cracks that block the movement of electrons and ions, sharply shortening battery life. Keeping the components pressed together also requires high-pressure clamping hardware, adding to battery weight and production costs.

Previous attempts to address the problem — such as inserting layers of rubber binders like nitrile butadiene rubber or polyethylene oxide between the electrode and the sulfide electrolyte — fell short due to reduced ion conductivity and the formation of unwanted byproducts.

Researchers display a sulfide electrolyte membrane containing the elastic ion-conducting polymer. [Korea Research Institute of Chemical Technology]

The research team solved the problem by infusing an elastic ion-conducting polymer directly into the sulfide electrolyte. A liquid-state precursor was injected into the electrolyte and then cured into a network structure, filling the voids between electrolyte particles.

The injected elastic polymer serves two functions. Like a seismic damper in a building, it absorbs the mechanical stress caused by electrode expansion and contraction during charging and discharging, and it binds the electrolyte and electrode together to reduce crack formation. It also fills the empty spaces within the electrolyte, providing additional pathways for lithium-ion movement and maintaining ion-conducting performance.

In experiments simulating repeated charge-discharge cycles through lithium plating and stripping, batteries incorporating the elastic polymer operated stably for more than 2,500 hours. Conventional sulfide electrolyte batteries showed cumulative interfacial damage over repeated cycles, while those with the elastic polymer maintained a stable interface throughout.

A sulfide all-solid-state battery pouch cell and the highly elastic ion-conducting material developed by the research team. [Korea Research Institute of Chemical Technology]

The new batteries also retained higher capacity under fast charge-discharge conditions. After 200 cycles, capacity retention stood at just 22 percent for batteries using a conventional sulfide electrolyte, compared with 75 percent for those incorporating the elastic polymer — a more than threefold improvement that translates to significantly less performance degradation over extended use.

The team also confirmed that the technology reduces batteries' dependence on external pressure. Conventional sulfide all-solid-state batteries require high operating pressure to maintain contact between the electrode and electrolyte. The new approach delivered relatively stable performance even under low-pressure conditions, which the researchers said could help lower manufacturing costs and simplify battery structure — a meaningful step toward commercialization.

The team plans to conduct further validation in large-format batteries and in conditions suited to electric vehicle applications.

"This is a technology that can solve the mechanical stability problem, which is a core challenge for sulfide all-solid-state batteries," Kim said.

The research, supported by the National Research Council of Science and Technology's Global TOP Strategic Research program, was published in the May issue of the international journal Energy Storage Materials.

nbgkoo@heraldcorp.com