Critical Perspective on the Industry-centred Engineering of Single Crystalline NCM Cathodes

Abstract

Ever growth in the demand of the energy has catapulted us to explore various energies and henceforth, multiple energy storage devices have been under intense research that can quench this desire. To meet these ends, among the various cathode active materials, Nickel(Ni) rich polycrystalline cathode materials have been known to aptly serve the purpose. Yet, with an increase in the voltage, temperature and the number of cycles, these Ni polycrystalline rich cathode active materials were found in a deteriorated condition and have yielded inferior performances. This is mainly attributed to the polycrystallinity of the cathode materials where micro/Nano-sized primary particles have aggregated to form the secondary particles.[1] As the number of charge-discharge cycles increase, battery operating voltage goes beyond 4.2 V, the anisotropic mechanical strain arises in the c direction of the layered structure and the non-uniform distribution of the strain in the randomly oriented primary particles causes the intergranular cracking, which initiates the parasitic side reactions. These inter-grain cracks lead to rapid impedance growth and capacity decay. Owing to few of these cracks that arise during the calendaring process, the compact density of the electrode and the volumetric density are limited to a considerable extent.[2] Adding to these setbacks, cation mixing has been widely reported as a factor in plummeting the output performances. As a result, the scientific community has focused on the Single Crystalline NCM cathode materials to combat this below par performance. The absence of grain boundaries in the intrinsic structure, high mechanical strength, high thermal stability, and controllable crystal faucet led to the major EV battery sectors eyeing for the development of SC cathodes. Yet, there are challenges to overcome in the SC cathodes like larger crystals hinder the Li+ transport and longer ionic transport pathway, this leads to disappointing electrochemical performance. In recent months, we have seen immense growth in publication of papers in SC cathodes suggesting various synthesis methods, various strategies to overcome the challenges involving cation doping and surface coating which involves less complicated processes and scalability which is an important parameter in the perspective of the industries. Dopants or Coating elements have complementary effect and mitigate the losses that have been observed in the pristine material. Various dopants such as Aluminium, Magnesium,[3] Boron [1], Tungsten, Vanadium have been doped to enhance the ability to tackle the anomalies at high temperatures and voltages. Through this perspective article we wish to elucidate the crucial factors that facilitate the growth of SC-NCM Cathode, on-going research on the SC-NCM, viable dopants and coating materials that could possibly be used to enhance the performance, future scope, and scalability of SC-NCM at Industrial level. Additionally, we have presented the preparation of the pristine Single crystalline NCM Cathode and Boron doped Single Crystalline NCM cathode material (B SC NCM) through Co-precipitation method in Continuous stirred Tank Reactor, characterization results of the precursor are presented, Fig. 1. This perspective article explores the possible solutions and lapses that facilitate a conducive environment to the scientific fraternity in reducing the need gap in the energy storage sector.[4] Identification of lapses in the pivotal aspect in battling this ever-growing problem. Through this paper, we aspire that it leads to manufacturing of batteries that would effectively operate for longer durations and support in lowering the amount of toxic chemicals that are released into the atmosphere.