Electric Vehicle Charging in 15 Minutes... Development of Single-Crystal Material for High-Speed Charging

Professor Jae-Pil Cho, Distinguished Professor of Energy Chemical Engineering at UNIST and CEO of SMLab.

[Asia Economy Yeongnam Reporting Headquarters Reporter Hwang Dooyul] A technology for charging electric vehicle (EV) batteries in 15 minutes using ‘cathode material’ has been developed. It is a revolutionary method that reduces lifespan degradation caused by fast charging while using the existing anode material as is.

SMLAB, a faculty startup company from UNIST, has developed a ‘single-crystal cathode material’ technology that can improve the fast-charging characteristics of lithium-ion batteries.

Simply by changing the shape and surface structure of the cathode material, the lifespan characteristics improved by more than 30%.

The material has completed customer verification and is currently in pilot production on SMLAB’s mass production line, with sample sales already occurring.

When rapid charging is repeatedly applied to lithium-ion batteries used in electric vehicles (EVs), side reactions occur at both the cathode and anode, causing lifespan degradation. During fast charging, lithium ions cannot penetrate into the graphite particles of the anode and instead react with the electrolyte, resulting in loss.

At the cathode, lithium ions move in and out at a rapid rate, and repeated charging and discharging cause volume expansion that collapses the cathode structure, making lithium-ion transport difficult.

These issues ultimately raise the battery cell temperature and accelerate decomposition on the surfaces of the electrolyte, cathode, and anode materials, leading to lifespan degradation.

Technologies to solve these problems have mainly focused on improving anode materials. Attempts were made to shorten charging time by using lithium metal instead of graphite or by using a combination of graphite and silicon.

This is because lithium ions move faster in lithium metal or silicon than in graphite.

The fast-charging technology developed by SMLAB dramatically improved fast-charging characteristics by maintaining graphite in the anode while changing the formation and surface structure of the cathode material.

The developed cathode material is a single-crystal NCA(M) material (NiCoAlMn) with 97% nickel (Ni) and less than 2% cobalt (Co) content.

Scanning electron microscope image of Ni97% NCA(M) single crystal material.

Jae-pil Cho, CEO of SMLAB, said, “Existing cathode materials for fast charging are polycrystalline with about 80% nickel content and expensive cobalt content exceeding 5%. The single-crystal cathode material, which increases nickel content to 97% and reduces cobalt content to less than 2%, enhancing price competitiveness, is being reported for the first time.”

SMLAB conducted fast-charging evaluations using its in-house pouch-type lithium-ion battery manufacturing facility.

The cathode was a 1Ah cell with an energy density of 187Wh/kg and a capacity of 4.07mAh/cm² under 25°C conditions, using only graphite for the anode.

As a result, even after 300 cycles of charging (to 90%) and discharging (to 0%) over 15 minutes, the lifespan characteristic was maintained at 85%.

In contrast, polycrystalline materials with the same composition showed a rapid decline to 40% lifespan retention after 225 charge-discharge cycles.

Comparison of cycle life retention during 15-minute fast charging of Ni 97% NCA(M) material.

The results indicate that rapid lithium-ion movement in polycrystalline materials accelerates the collapse of the polycrystalline surface structure.

Since the polycrystalline structure consists of small particles of several hundred nanometers clustered to form a large particle, rapid lithium-ion movement causes the surface structure to collapse and breaks apart the clustered particles.

Comparison of Rolling Between Single-Crystal and Polycrystalline Materials.

CEO Jae-pil Cho stated, “To improve battery lifespan during fast charging, we made the cathode material shape ‘single-crystal’ and completely overcame the high resistance problem occurring at high currents by doping manganese (Mn) and trace additives. Particularly, directing lithium ions to move maximally along specific crystal plane orientations on the single-crystal surface demonstrates that the shape and surface structure of the cathode affect fast charge-discharge characteristics.”

SMLAB was founded in July 2018 by Distinguished Professor Jae-pil Cho of the Department of Energy and Chemical Engineering at UNIST.

The company possesses technology to mass-produce NCM(A) and NCA with nickel content above 80% in single-crystal form without water washing processes.

Currently, the annual production volume of materials with nickel content above 94% is 7,200 tons, and the company plans to expand by 21,600 tons to reach 28,800 tons by 2023.

This content was produced with the assistance of AI translation services.