What is the Role of Nb in Nickel-Rich Layered Oxide Cathodes for Lithium-Ion Batteries?

Abstract

Nickel-rich layered metal oxide LiNi 1−y−z Mn y Co z O 2 (1 − y − z ≥ 0.8) materials are the most promising cathodes for next-generation lithium-ion batteries in electric vehicles. However, they lose more than 10% of their capacity on the first cycle, and interfacial/structural instability causes capacity fading. Coating and substitution are possible direct and effective solutions to solve these challenges. In this Letter, Nb coating and Nb substitution on LiNi 0.8 Mn 0.1 Co 0.1 O 2 (NMC811) is easily produced through a scalable wet chemistry method followed by sintering from 400 to 800 °C. A Li-free Nb oxide treatment is found to remove surface impurities forming a LiNbO 3 /Li 3 NbO 4 surface coating, to reduce the first capacity loss and to improve the rate performance. Nb substitution stabilizes the structure, as evidenced by less heat evolution on heating, thus providing better long cycling stability with a 93.2% capacity retention after 250 cycles.

A Cobalt‐ and Manganese‐Free High‐Nickel Layered Oxide Cathode for Long‐Life, Safer Lithium‐Ion Batteries

“…[ 32 ] By virtue of this surface‐enriched Ti distribution, pernicious side reactions between electrolyte and the active material might be mitigated, according to literature reports on similar functional elements, such as Y 3+ , Zr 4+ , and Nb 5+ . [ 21,35–38 ]…”

“…[ 6,7 ] Therefore, increasing efforts have been devoted to the development of cathode materials with ultrahigh Ni contents of no less than 90 mol% and reduced or zero usage of Co. Meanwhile, the challenges brought by ultrahigh‐Ni cathodes, including the aggravated electrode–electrolyte interphase deterioration, [ 7–9 ] surface rock‐salt phase (NiO) formation through lattice reconstruction, [ 10–12 ] microcrack formation leading to particle pulverization, [ 7,13,14 ] and transition metal dissolution, [ 15,16 ] are under intensive investigations with an emphasis on stabilization strategies, such as cationic doping, [ 17,18 ] surface engineering, [ 19–21 ] microstructure regulation, [ 22 ] and electrolyte optimization. [ 23,24 ] A few examples of Co‐free, ultrahigh‐Ni cathodes are LiNi 0.90 Mn 0.10 O 2 , [ 25 ] LiNi 0.90 Mn 0.05 Al 0.05 O 2 , [ 26 ] and LiNi 0.96 Mg 0.02 Mn 0.02 O 2 , [ 27 ] which all exhibit a prolonged cycled life compared to the current commercial cathodes.…”

Enhancing Surface Chemical Stability of LiMn2O4 Cathode by Strontium Enrichment at Grain Boundaries

“…However, this phenomenon does not mean that Sr can easily and uniformly enter the bulk phase of LMO, because atoms can occupy sites of other atoms on the surface of the material that originated from high temperature, and this phenomenon also occurs in other material systems. [28] As shown in Scheme 1, we designed a route to synthesize Sr-modified LMO materials by a one-step calcination route. The morphologies of LMO and modified samples were investigated by SEM.…”

Synthesis and Processing by Design of High‐Nickel Cathode Materials

“…It has been demonstrated that Nb coating/doping in NMC 811 was prepared in a one‐step heat treatment, with the coating layer to increase the capacity while doping to stabilize the layered structure. As a result, significant improvement was achieved in the 1 st capacity loss, discharge capacity, rate performance and cycling stability [73,74] …”