Shuhuang Tan

The demand for high energy density in mobile devices (including vehicles and small ships) is increasing. Nickel–Manganese–Cobalt (NMC) ternary, as a battery cathode material, is increasingly being applied because of its higher energy density relative to LiFePO₄ or other traditional materials. But NMC also faces challenges, such as a high degeneration rate and heat generation. So these aspects of Ni content must be clarified. In the current study, two Ni-content battery cells were tested, and the results of other composition cathode cells from the literature were compared. And three typical Ni-content batteries were simulated for searching Ni effects on performance, capacity fade and heat generation. Some findings were achieved: (1) from 0.8 Ni content, it can be seen that the specific capacity growth rate (slope) was much greater than before; (2) cathode materials that have an odd number (that does not surpass 0.7) of Ni content showed a linear capacity degradation trend, but others did not; (3) the Li concentration within material particles did not correspond to absolute stress value but stress temporal gradient; and (4) during discharge, lower Ni content made the heat peak occur earlier but lowered the absolute value; the irreversible heat increased with Ni content non-linearly, so that the higher the Ni content went up, the higher the increase rate of the irreversible heat ratio. Thus, the results of this study can guide the design and application of high energy batteries for mobile devices.

High-performance electrode materials are fundamental to improving supercapacitor performance, serving as key factors in developing devices with high energy density, high power density, and excellent cyclic stability. Non-stoichiometric spinels with phase deficiencies can achieve electrochemical performance that surpasses that of stoichiometric materials, owing to their unique structural characteristics. In this study, we used a microwave-assisted method to synthesize a high-performance non-stoichiometric spinel material with phase deficiencies, Mn_0.5Co_2.5O₄, which displayed a wide potential window (1.13 V in a traditional aqueous three-electrode system) and high specific capacitance (716.9 F g⁻¹ at 1 A g⁻¹). More critically, through microwave-assisted doping engineering, nickel was successfully doped into the phase-deficient Mn_0.5Co_2.5O₄, resulting in a spinel material, Ni−Mn_0.5Co_2.5O₄, with significant lattice defects and a mixed 1D/2D morphology. The doping of nickel effectively promoted the high-state conversion of manganese valence states within the manganese cobaltite material, substantially increasing the quantity of highly active Co³⁺ ions. These changes led to an increase in the density of reactive sites, effectively promoting synergistic interactions, thereby significantly enhancing the material’s conductivity and energy storage performance. The specific capacitance of Ni−Mn_0.5Co_2.5O₄ reached 1180.6 F g⁻¹ at 1 A g⁻¹, a 64.7% improvement over the original Mn_0.5Co_2.5O₄; at a high current density of 10 A g⁻¹, the capacitance increased by 14.3%. Notably, the charge transfer resistance was reduced by a factor of 41.6. After 5000 cycles of testing, the capacity retention stood at 79.2%. This work reveals the effectiveness of microwave-assisted doping engineering in constructing high-performance non-stoichiometric spinel-type bimetallic oxide materials, offering advanced strategies for the development of high-performance electrode materials.