Researchers in South Korea have doubled the volumetric energy density of an anode-free lithium metal battery to boost the range of EVs, writes Nick Flaherty.

The team from three universities achieved a volumetric energy density of 1270 Wh/L in an anode-free lithium metal pouch cell battery. This value is nearly twice that of current lithium-ion batteries used in EVs, which typically deliver around 650 Wh/L.

The team was led by Professor Soojin Park and Dr Dong-Yeob Han of the Department of Chemistry at POSTECH, together with Professor Nam-Soon Choi and Dr Saehun Kim of KAIST, and Professor Tae Kyung Lee and researcher Junsu Son of Gyeongsang National University.

An anode-free lithium metal battery eliminates the conventional anode altogether. Instead, lithium ions stored in the cathode move during charging and deposit directly onto a copper current collector. By removing unnecessary components, more internal space can be devoted to energy storage, increasing the volumetric energy density.

However, this design comes with serious challenges. If lithium deposits unevenly, dendrites can form, increasing the risk of short-circuits and potential safety hazards. Repeated charging and discharging can also damage the lithium surface, rapidly shortening battery life.

To address these issues, the research team combined a Reversible Host (RH) and a Designed Electrolyte (DEL). The RH consists of a polymer framework embedded with uniformly distributed silver nanoparticles, guiding lithium to deposit in designated locations rather than in a random fashion.

The designed electrolyte provides stability by forming a thin but robust protective layer composed of Li2O and Li3N on the lithium surface using commercially available salts, solvents and additives to establish stable electrode–electrolyte interphases at both electrodes. This layer prevents harmful dendrite growth while maintaining open pathways for lithium ion transport.

High areal capacity of 4.6 mAh/cm² and current density of 2.3 mA/cm² was delivered by the combined RH–DEL system and the battery retained 81.9% of its initial capacity after 100 cycles with an average Coulombic efficiency of 99.6%. These results enabled the team to reach the record-breaking 1270 Wh/L volumetric energy density in an anode-free lithium metal battery.

A key factor was that the performance was validated in pouch-type batteries, which are closer to real-world EV applications. Even with a minimal 2.5 g/Ah of electrolyte and under low stack pressure (20 kPa), the batteries operated stably, demonstrating strong potential for reducing battery weight and volume while lowering manufacturing burdens, thereby significantly improving commercial viability.

“This represents a meaningful breakthrough by simultaneously addressing efficiency and lifetime issues in anode-free lithium metal batteries,” said Professor Soojin Park.

Using commercial electrolytes was also key to scaling up the battery. “Our study demonstrates that electrolyte design based on commercially available solvents can achieve both high lithium-ion mobility and interfacial stability,” said Professor Tae Kyung Lee.