Ultrahigh Rate Performance of a Robust Lithium Nickel Manganese Cobalt Oxide Cathode with Preferentially Orientated Li-Diffusing Channels

Abstract

Lithium nickel manganese cobalt oxide (NMC) materials, with low cost and high energy density, are considered to be among the most promising cathode materials for Li-ion batteries (LIBs). However, several issues have hindered their further deployment, particularly for high-powered applications, including limited rate capability, capacity loss during cycling (especially at high temperatures and high voltages), and difficulty in reproducibly preparing the desired particle morphology. In this work, we have developed a robust LiNi0.33Mn0.33Co0.33O2 cathode material (NMC-111) capable of high-rate performance for LIBs. Our high power NMC-111 (HP-NMC) cathode materials showed significantly enhanced electrochemical performance, relative to a commercial NMC-111 (c-NMC), with discharge capacities of 138 and 131 mAh/g at high current rates of 20 and 30 C, respectively. The material also exhibited enhanced cycling stability under both room temperature and at 50 °C. We ascribe the high performance of our material to a unique crystalline microstructure observed by electron microscopy characterization, which showed preferential orientation of the Li-diffusing channels radially outward. This HP-NMC material achieved one of the highest performance metrics among NMC materials reported to date, especially for high-powered electric vehicles.

Recent Developments of Nanomaterials and Nanostructures for High‐Rate Lithium Ion Batteries

“…Since the diffusion channels of lithium ions between LiNi 0.33 Mn 0.33 Co 0.33 O 2 layers are parallel to the long axes, this unique geometry can dramatically improve the reaction kinetics due to the establishment of oriented diffusion pathways. Devices with high capacity (131 mAh g −1 ) at ultrahigh current rate (30 C, 1 C=278 mA g −1 ) were reported in the study, showing much better performance than that of counterparts prepared with commercial LiNi 0.33 Mn 0.33 Co 0.33 O 2 ‐based cathode …”

“…[300] Recently, Ren et al prepared an interesting crystal structure based on LiNi 0.33 Mn 0.33 Co 0.33 O 2 , in which preferential diffusion channels for lithium ions with a radially outward orientation was observed. [301] As shown in Figure 30b, the synthesised particle is formed by a large number of nanoplates whose long axes are oriented radially outward from the particle interior (shown in the grain map in the inset of Figure 30b). Since the diffusion channels of lithium ions between LiNi 0.33 Mn 0.33 Co 0.33 O 2 layers are parallel to the long axes, this unique geometry can dramatically improve the reaction kinetics due to the establishment of oriented diffusion pathways.…”

“…Devices with high capacity (131 mAh g À 1 ) at ultrahigh current rate (30 C, 1 C = 278 mA g À 1 ) were reported in the study, showing much better performance than that of counterparts prepared with commercial Li-Ni 0.33 Mn 0.33 Co 0.33 O 2 -based cathode. [301] In order to fulfil the increasing demand for cathode material with excellent electrochemical properties, various modification approaches are often combined together to improve the performance of lithium nickel manganese cobalt oxides. [302] As an example, F127-assisted fluorine doped lithium nickel manganese cobalt oxide (F127-NCMF) was synthesised by a facile co-precipitation procedure developed by Li et al [303] In detail, an aqueous solution of F127 (a type of non-ionic surfactant) and Na 2 CO 3 was added into the metal salt solution containing Ni (CH 3 COOH) 2 • 4H 2 O, Co(CH 3 COOH) 2 • 4H 2 O and Mn (CH 3 COOH) 2 • 4H 2 O, which was then followed by a series of cleaning steps (filtering, washing and drying) to produce the precursor (F127-Ni 0.5 Co 0.2 Mn 0.3 CO 3 ), as shown in Figure 30c.…”

“…(b) SEM image of the as-prepared layered LiNi 0.33 Mn 0.33 Co 0.33 O 2 particle (the inset shows the grain structure determined by scanning transmission electron microscopy diffraction map). [301] Reproduced with permission from Ref. [301].…”

“…Recently, Ren et al. prepared an interesting crystal structure based on LiNi 0.33 Mn 0.33 Co 0.33 O 2 , in which preferential diffusion channels for lithium ions with a radially outward orientation was observed . As shown in Figure b, the synthesised particle is formed by a large number of nanoplates whose long axes are oriented radially outward from the particle interior (shown in the grain map in the inset of Figure b).…”