LG Energy Solution, Seoul National University cut LMR battery gassing via voltage limits

LG Energy Solution and Seoul National University have found a set of operating conditions that suppresses gas generation in lithium manganese-rich (LMR) cells, one of the obstacles to using the chemistry in large-format EV batteries. The joint research, carried out with Jongwoo Lim's team in Seoul National University's Department of Chemistry, was published in Nature Communications.

LMR cathodes use manganese as a primary material and contain no cobalt, which LG Energy Solution says lowers material costs. LMR gets its energy density from storing energy in both the transition metals, such as nickel and manganese, and the oxygen in the cathode material.

Oxygen oxidized during charging that does not fully return to its original state during discharge damages the cell's internal structure and produces gas. Large-format EV cells have little spare internal volume, so the gas raises internal pressure and degrades performance.

The team analyzed oxygen redox across different charge and discharge conditions and found that oxygen recovery depends on both the upper cutoff voltage used in charging and the cutoff voltage used in discharging. Lowering the upper charging voltage from 4.6 V to 4.3 V increased the share of oxidized oxygen that was reduced again from 86% to 97%. Lowering the discharge cutoff from the conventional 3.0 V to 2.0 V let the oxygen recover to nearly its original state.

LG Energy Solution's researchers then redesigned the operating voltage range and the formation process for 40 Ah-class large-format LMR cells, including a lower-temperature formation step to hold down gas generation. The optimized cells retained 92.2% of their initial energy after 883 charge and discharge cycles. That result expands LMR's potential beyond small-format applications, according to the company.

The company is separately developing LMR prismatic cells with General Motors, and the two plan to begin US production in 2028.

"This study identified the causes of degradation in LMR batteries from the perspective of oxygen reversibility and demonstrated that cell stability can be improved through electrochemical protocol design alone," said Jongwoo Lim, Professor in Seoul National University's Department of Chemistry. "We confirmed that achieving long-term stability in LMR batteries requires comprehensive consideration of not only charging conditions but also discharge conditions."

Source: LG Energy Solution