Researchers at Nanjing University (China) have introduced a new layered C2/m oxide—Li₂Ni_0.2Mn_0.4Ru_0.4O₃ (LNMR)—which undergoes a low volume variation of 1.5% in the voltage window of 2.0-4.6 V. Compared with Li₂MnO₃ (LMO), LNMR displays superior capacity, a more stable capacity retention rate, higher energy density and average discharge voltage.

An open-access paper on the work is published in the RSC journal Chemical Communications.

The typical charge/discharge profiles of LNMR and LMO electrodes at 10mA g^-1. Ke et al.

Coupled with oxygen redox chemistry and cationic redox reactions, layered lithium rich oxides (LLROs) are standing out overall structure as candidate cathode materials for next-generation LIBs. LLROs are usually consist of two phases of Li₂MnO₃ (LMO) with a space group of C2/m and LiTMO₂ (TM refers to a transition metal element) with a space group of R-3m. The ordinary modification of LLROs is usually aimed at xLi₂MnO₃·(1−x)LiTMO₂, the solid solution of two layered components.

The high operating voltage and large capacity of LLROs tend to depend on LMO phase. In such materials, 1/3 of the TM sites are occupied by Li phase. In such materials, 1/3 of the TM sites are occupied by Li, forming a honeycomb structure. The layered LMO oxide is considered as an attractive candidate cathode material due to its high capacity and voltage.

… However, irreversible oxygen release occurs during the initial charging process of LMO, leading to irreversible redox of oxygen, which is the only redox process without cationic redox. Meanwhile, LMO also face other challenges such as capacity attenuation and low discharge capacity, which hinder its commercial application.

Here, we propose a means of atomic mixing in transition metal layer manufacturing a new material Li₂Ni_0.2Mn_0.4Ru_0.4O₃ (LNMR). Ru⁵⁺ and Ni²⁺ are introduced into the structure to partially replace Mn⁴⁺ and Li⁺ in transition metal layer, and the introduced two different elements play their respective strengths.

—Ke et al.

Resources

• Bingyu Ke, Shiyong Chu, Jing-Chang Li, Xiang-Qun Xu, Huan Yao, Shaohua Guo and Haoshen Zhou (2022) “A new Li-rich layered cathode with low lattice-strain for Lithium-ion batteries” Chem. Commun. doi: 10.1039/D2CC04044A