Lithium-ion batteries (LIBs), mainly used as the power of 3 C electronic products, require higher energy density, longer cycling life, faster charging capability, and broader operating temperature range to meet the growing consumer demands.

LiCoO₂ (LCO) is the primary cathode material for LIBs. Currently, the advanced electrolytes for LCO cannot meet the high energy density and fast-charging performance of LIBs.

Recently, a research group led by Prof. WU Zhongshuai from the Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences (CAS) developed a novel universal additive-containing "cocktail electrolyte" based on the synergistic cooperation of multi-component additives. This electrolyte enabled commercial LCO with high voltage (4.6 V) and ultra-fast charging (5 C) in a wide temperature range (-20 to 45 ℃). It also exhibited high applicability to high-Ni and Co-free cathodes. This study was published in Energy & Environmental Science.

In principle, increasing the charging cut-off voltage can improve the energy density of the batteries. However, it can lead to the continuous oxidative decomposition of electrolytes, excessive growth of non-uniform cathode-electrolyte interphase (CEI), and sluggish interfacial kinetics, which hinders LCO from achieving high voltage and fast charging.

To solve the above problems, the researchers proposed a novel "cocktail electrolyte" (FPE), which could improve the ultra-stable fast-charging cycle stability of commercial LCO at 4.6 V.

They revealed that the cooperation between multiple components in FPE led to the robust and kinetically fat electrode/electrolyte interphases on both cathode and anode. These interfaces, enriched with LiF and Li₃PO₄, displayed strong mechanical stability and enhanced ionic conductivity. As a result, they prevented cathode surface degradation, suppressed unwanted interfacial reactions, accelerated reaction kinetics, and mitigated the formation of lithium dendrites even under extremely high current densities. Therefore, they achieved a high-performance 4.6 V Li-ion battery.

The results showed that the capacity retention in FPE was as high as 73.2%, even at 5 C over 1000 cycles. In practical pouch-type cells, this electrolyte enabled graphite||LCO battery to maintain up to 72.1% capacity retention after 2000 cycles and long-term cyclability over 3800 cycles.

Besides, the researchers showed the general application of FPE in high-voltage Ni-rich and Co-free cathodes.

"This work provides a practical strategy for high-energy-density and fast-charging batteries," said Prof. WU.