Pulse High Temperature Sintering to Prepare Single‐Crystal High Nickel Oxide Cathodes with Enhanced Electrochemical Performance

Abstract

is still the most popular cathode material in the LIBs for 3C products, mainly owing to its extraordinarily high tap density, [2] since there is a stricter requirement on the volumetric energy density. To reduce the amount of high-cost Co, part of Co was substituted by Ni and Mn with the generation of Li(Ni x Co y Mn z )O 2 (NCM, x + y + z = 1), which not only improves the structural and thermal stability but also allows more reversible extraction-intercalation of Li + and so endows more capacity, making it currently the dominant cathode materials in the market of power batteries of EVs. [3] Currently, compared with internal combustion engine vehicles, the main concerns for the popularization of EVs are the higher price, lower continue voyage course, and heavier safety risk, mainly resulting from the LIBs.For NCM cathodes, the capacities increase gradually with the increment of Ni contents; for instance, from Li(Ni 0.5 Co 0.2 Mn 0.3 )O 2 (NCM523) to Li(Ni 0.8 Co 0.1 Mn 0.1 )O 2 (NCM811), the capacity rises from 165 to 200 mAh g −1 , around 20% promotion. [4] However, with the increment of capacity, more Li + will reversibly intercalate into and extract from the NCM layered structure, resulting in larger volumetric change, more intergranular microcracks, and heavier interfacial reactions. [5] In addition, with the increase of Ni content, more superficial Ni 4+ ions lead to heavier catalytic oxidation of electrolytes, causing more serious capacity fading and safety risks. [6] To reduce the intergranular microcracks

Perspective on the Preparation Methods of Single Crystalline High Nickel Oxide Cathode Materials

“…[85] It is observed that with the ascending of Sr content and the rise of Li/TM ratio and the increase of sintering temperature, the particle size keeps growing progressively (Figure 8a). Similar to other reports, [11] with the increment of SC-NCM particle size, the Li + /Ni 2+ disorder rates are gradually increased. For instance, the Li + /Ni 2+ disorder rate was only 2.7% for SC-D1, but it progressively grew to 3.9%, 4.6%, 5.0%, and 5.1% for SC-D3, SC-D5, SC-D7, and SC-D9 samples, respectively.…”

“…Based on these considerations, very recently, Zhou and Qiu proposed a PHTS to prepare SC-NCM90 and SC-NCM80 materials. [11] It has been demonstrated that the Li-loss start to be serious at higher than 950 °C, which is also the lowest single crystalline growth temperature and is widely used in CHTS. In PHTS, on the basis of the traditional calcination procedure for ensuring phase generation, an additional shortterm higher temperature process was introduced as a pulse heating for primary particles' fusion, in which, the applied temperature is ≈150 °C higher than that used in CHTS and is ≈300 °C higher than the temperature used in preparing PC-NCM.…”

“…Combing the advantages of UHTS and CHTS, a strategy of pulse high-temperature sintering (PHTS) was developed for the preparation of SC-NCM materials (Figure 1). [11] In the middle of regular CHTS process, a 250-300 °C higher temperature sintering section for 1 min was introduced, producing well-defined octahedron SC-NCM particles. Such a strategy is compatible with the current calcination instruments for potential roll-out in large-scale production.…”

“…g) In situ CO 2 generation test of PC-NCM90 and SC-NCM90 by differential electrochemical mass spectrometry(DEMS) charging up to 4.7 V.h) The SC-NCM90 prepared using Li 2 CO 3 as lithium source and through PHTS at 1040 °C for 1 min. Reproduced with permission [11]. Copyright 2022, Wiley-VCH.…”

Pulse-Assisted Low-Temperature Sintering to Enhance the Fast-Charging Capability for P2-Layered Na-Based Cathodes

“…Notably, both the concentration of OVs and particle morphology are correlated to the parameters of the sintering process, such as the temperature, time, and atmosphere. For example, Zhou et al prepared octahedral particles through nonisothermal sintering . Cui et al proposed a temperature swing-like sintering strategy with a heating and cooling rate of 0.125 °C min –1 to stabilize the lattice oxygen .…”