KAIST Develops 'Electrolyte Additive Technology' to Extend LFP Battery Life

An electrolyte additive technology that can extend the lifespan of lithium iron phosphate (LFP) batteries has been developed domestically. When this technology is applied to batteries for electric vehicles, the high-temperature lifespan is expected to increase by 20% and the room-temperature lifespan by 9% compared to electrolytes without additives.

KAIST announced on the 16th that a research team led by Professor Choi Nam-soon from the Department of Biological Chemistry successfully developed an 'electrolyte additive technology' that increases the number of charge-discharge cycles at room and high temperatures for lithium-ion secondary batteries composed of low-cost lithium iron phosphate cathodes and graphite anodes.

High-performance energy density batteries are essential to extend the driving range of electric vehicles. Lithium iron phosphate attracts attention due to its advantage of securing high energy density at the pack level. However, the lithium iron phosphate cathode has limitations due to its low electronic conductivity, making it difficult to form an interfacial layer.

The technology developed by the research team is significant in that it provides a foundation to overcome the limitations of lithium iron phosphate.

C-AFM nanoscale imaging results of lithium iron phosphate cathodes without the developed additive and with the developed additive applied. The imaging results show that the case using the developed additive exhibits relatively higher 3D current signals (an increase in the green areas). Provided by KAIST

Previous electrolyte additive research mainly focused on protecting graphite anodes by designing additives that form an interfacial layer with high ionic conductivity while suppressing electrolyte side reactions and preventing the growth of lithium dendrites by having low electronic conductivity.

However, the electrolyte additive developed by the research team not only protects the graphite anode but also protects the lithium iron phosphate cathode through the introduction of Cell To Pack (CTP) technology, which has low heat generation characteristics and achieves high energy density at the pack level by omitting the module. It successfully balances electronic conductivity and ionic conductivity on the cathode surface. The core achievement is solving the problem of rapid capacity decline even after many charge-discharge cycles.

In particular, the technology developed by the research team is meaningful because it extended the battery’s room and high-temperature lifespan using graphite anodes with high compounding density demanded by companies and lithium iron phosphate cathodes, and it suggested a design direction for lithium iron phosphate electrolyte additives that maximize efficiency at low cost.

This research was conducted with support from Hyundai Motor Company. Professor Choi Nam-soon and researchers Moon Hyun-gyu and Kim Dong-wook (currently at LG Energy Solution) at KAIST were responsible for developing the electrolyte system and experimentally elucidating the principles. Professor Hong Seung-beom and researcher Park Geon (currently at LG Energy Solution) at KAIST visualized the electronic conductivity at the nanoscale on the lithium iron phosphate cathode surface with the electrolyte additive applied, using conductive atomic force microscopy (C-AFM) analysis.

Moon Hyun-gyu, a co-first author of the paper and a researcher in the Department of Biological Chemical Engineering, said, "The developed electrolyte additive forms an electrode interfacial layer with excellent heat resistance and conductivity, exhibiting 80.8% and 73.3% of the initial capacity after 500 cycles at 45 degrees Celsius and 1000 cycles at 25 degrees Celsius, respectively. This represents an improvement of 20.4% and 8.6% compared to electrolytes without additives. If the developed additive is applied to electric vehicle batteries, the guaranteed lifespan (currently 10 years → 11 to 12 years) is expected to be extended."

He added, "It also improved the low electronic conductivity characteristics of the lithium iron phosphate cathode and was effective under fast charging conditions."

Meanwhile, the research results of the team were published online on May 9 in the international journal Advanced Functional Materials.

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