Korean researchers have developed a technology that could make electric-vehicle (EV) batteries smaller and lighter while helping EVs travel farther on a single charge. A KAIST research team has proposed a new solution to a persistent problem in anode-free batteries, which reduce weight and volume by eliminating anode materials such as graphite that normally store lithium during charging. In these batteries, lithium can grow into sharp, spike-like structures that shorten battery life. The key lies in using nanofabrication techniques employed in semiconductor manufacturing to create uniform sites for lithium deposition and promote the formation of a robust protective layer.

KAIST (President Choongsik Bae) announced on September 22 that a joint research team led by Professors Jinwoo Lee and Hee-Tae Jung from the Department of Chemical and Biomolecular Engineering, working with researchers from Kyungpook National University (President Heo Young-woo) and the National NanoFab Center (President Park Heung Soo), has developed a new technology that extends the lifespan of anode-free batteries by applying the ultrafine fabrication processes used in semiconductor device manufacturing to batteries.

Conventional lithium-ion batteries store lithium in an anode material such as graphite during charging. Anode-free batteries, by contrast, deposit lithium directly onto a thin copper foil without a separate anode material. Because they eliminate the weight and volume that the anode material would otherwise occupy, they are drawing attention as a next-generation technology capable of packing more energy into a battery of the same size.

However, repeated charging and discharging cause lithium to deposit unevenly on the copper foil, growing into branch- or spike-like structures known as dendrites. The protective layer over the lithium also becomes unstable, causing the battery’s performance and lifespan to deteriorate rapidly. This is one of the most significant obstacles standing in the way of commercializing anode-free batteries.

Some previous approaches to extending the lifespan of anode-free batteries involved adding excess lithium or applying a thick protective layer to the surface. These methods provide extra lithium to compensate for losses during use or coat the surface with a protective film. However, adding more material makes the battery heavier and thicker, undercutting the very advantage of a small, lightweight anode-free battery.

To minimize added weight and volume, the research team modified the copper foil on which lithium is deposited. Much like marking out closely spaced parking bays in a flat lot, the team created an array of microscopic tube-shaped structures on the copper surface so that lithium spreads out and deposits evenly rather than concentrating in one spot.

To do this, the team used a process called secondary sputtering lithography (SSL), used for the precise micromachining of semiconductors. Fabricating microscopic tubes about 300 nanometers in diameter and 150 nanometers in height on the copper foil increased the surface area available for lithium deposition to about four times that of flat copper foil, helping to reduce localized, spike-like lithium growth.

The team then coated the copper foil with a roughly 10-nanometer-thick layer of MXene, a two-dimensional material, forming an ultrathin film only a few thousandths the thickness of a human hair. Rather than serving as a finished protective layer itself, the MXene acts like a primer that draws together the components needed to form one. In the LiPF6-based electrolyte used in the study, the MXene surface promotes the formation of a robust protective layer rich in lithium fluoride (LiF) as the battery operates.

This protective layer reduces unwanted reactions between the lithium and the electrolyte and also suppresses the spike-like growth of lithium. By examining electrode surfaces and cross sections while minimizing air exposure, the research team confirmed that a nanoscale protective layer forms uniformly along the MXene and identified the mechanism behind its formation. The analysis employed X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS), and transmission electron microscopy (TEM), among other techniques.

Professor Jinwoo Lee said, “This study shows how ultrafine fabrication techniques used in semiconductor manufacturing can create both uniform sites for lithium deposition and a stable protective layer without changing the bulk electrolyte formulation or adding excess lithium.” He added that the technology is expected to serve as a foundation for accelerating the commercialization of high-energy anode-free batteries by extending battery life while minimizing increases in weight and volume.

KAIST researchers Eunji Kim, Hyunju Jung, and Jinuk Kim participated as co-first authors on the study. The findings were published online in the international journal Advanced Functional Materials on September 1.

Paper title: Anion-Interactive Anode Interfaces for Stable Anode-Free Lithium Metal Batteries, DOI 10.1002/adfm.77931
Author information: Eunji Kim (KAIST/National NanoFab Center, co-first author), Hyunju Jung (KAIST, co-first author), Jinuk Kim (KAIST, co-first author), Hee-Tae Jung (KAIST, corresponding author), Yonghee Lee (Kyungpook National University, corresponding author), Jinwoo Lee (KAIST, corresponding author)

This research was supported by the Nano&Material Technology Development Program through the National Research Foundation of Korea (NRF) funded by Ministry of Science and ICT (RS-2026-25542167), as well as the Global Semiconductor Advanced Fab Utilization Project through the National Nano Fab Center (NNFC). This work was also supported by Semiconductor-Secondary Battery Interfacing Platform Technology Development Project of NNFC.