A team from Argonne National Laboratory and Pacific Northwest National Laboratory (PNNL) has developed a new cobalt-free cathode for high-energy lithium-ion cells. The novel LiMn0.5Ni0.5O2 cathode with a predominant, partially-disordered lithiated-spinel structure was prepared by a low-temperature (LT) synthesis.
In an open-access paper in the RSC journal Chemical Communications, the team reports that Li/LT-LiMn0.5Ni0.5O2 cells operate between 5.0 and 2.5 V with good cycling stability, yielding a capacity of 225 mAh/g, principally by redox reactions on the nickel ions on distinct voltage plateaus at ~3.6 V and ~4.6 V.
The growing penetration of lithium-ion batteries (LIBs) into the transportation- and stationary-storage markets requires low-cost, high-capacity cathode materials. Recent development of layered Li(Ni1-x-yMnxCoy)O2 cathodes (NMCs) has focused on increasing the nickel content while decreasing the cobalt content to optimize energy and cost. However, the structural and thermal instability of Ni-rich oxides pose concerns about their long-term viability.There is, therefore, a need to develop new cathode materials based on inexpensive, earth-abundant elements, such as Mn and Fe, for further growth and long-term sustainability of the market.
… Here, we report a new, polymorphic form of LiMn0.5Ni0.5O2. It has a partially-disordered rock salt structure with predominant lithiated-spinel-like character. This cathode material, denoted LT-LiMn0.5Ni0.5O2 (or LT-Li2MnNiO4 in lithiated-spinel notation) to differentiate it from the layered, ‘high-temperature’ HT-LiMn0.5Ni0.5O2 polymorph, delivers a high specific capacity (225 mAh/g) with good cycling stability over 50 cycles. … The discovery of LT-LiMn0.5Ni0.5O2, in which the nickel ions play a significant role in generating stable electrochemical capacity with only a small change to the volume of the cubic unit cell, holds promise for developing a high-capacity, Co-free cathode for an all-solid-state lithium-ion cell.
Boyu Shi, Jihyeon Gim, Linze Li, Chongmin Wang, Anh Vu, Jason Croy, Michael M. Thackeray and Eungje Lee (2021) “LT-LiMn0.5Ni0.5O2: A Unique Co-Free Cathode for High Energy Li-Ion Cells” Chem. Commun. doi: 10.1039/D1CC04334J