A Scalable Approach to Synthesize Cobalt-Free LNMO Cathode Materials for High Energy Density Lithium Ion Batteries
Authors: Hu Tao , Lin Yan , Tynjälä Pekka , Wang Shubo , Peta Gayathri , Singh Harishchandra , Aurbach Doron , Lassi Ulla 
Published: February 2024

The rapid growing demand for electric vehicles (EVs) has highlighted the need for high-energy-density batteries. The cathode material plays a vital role in achieving this goal[1]. As the limitations of cathode capacity improvement are approached, the pursuit for high-voltage materials becomes a viable option[2]. Lithium nickel manganese oxide LNMO (LiNi0.5Mn1.5O4) stands out due to its remarkable attributes including a substantial reversible capacity, excellent thermal stability, cost-effectiveness, environmental friendliness, and a high energy density[3]. Moreover, its cobalt-free composition aligns with sustainability objectives. Despite extensive research, the large-scale production and deployment of LNMO remain formidable challenges.
In this study an industrially applicable co-precipitation method-based scalable synthesis strategy is introduced. The LNMO spheres with controlled various sizes and morphologies were successfully fabricated by adjusting the pH environment during synthesis carefully (Fig. 1A). Scanning electron microscopy (SEM) revealed the presence of uniformly spherical particles with dimensions of appr. 6, 9, and 14 µm and unique morphological characteristics (Fig. 1Ad-f). Synchrotron X-ray diffraction (SXRD) of LNMO samples revealed a deviation from the optimal Ni-to-Mn ratio of 1:3 (Fig. 1B)[4,5]. This variation results from the pH-dependent metal ion precipitation dynamics during synthesis, introducing a fascinating dimension to LNMO material fabrication. As potential cathode materials for lithium-ion batteries, these samples underwent a thorough electrochemical evaluation as part of our research. Among the synthesized LNMO samples, LNMO-9 demonstrated the most promising specific capacity, surpassing approximately 138 mAh/g and working under high voltage of 4.75 V (Fig. 1C). Furthermore, the characterizations of the materials were also thoroughly investigated by a variety of advanced characterization techniques, including Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM).
This research reveals a strategy for synthesizing LNMO materials with certain regulated features and presents a successful strategy for industrial manufacturing as well. Particularly in the context of the EV industry, this research acquires critical significance in answering the growing demand for high-performance, sustainable energy storage systems.

Fig. 1 (A) Illustration of the synthesis process of LNMO-x samples with SEM images of (a‒c) NiMn-x precursors and (d‒f) LNMO-x products. (B) SXRD patterns with Rietveld refinements and (C) charge/discharge profile of LNMO-x samples.

Reference

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Figure 1