Role of Cobalt Content in Improving the Low-Temperature Performance of Layered Lithium-Rich Cathode Materials for Lithium-Ion Batteries

Abstract

Layered lithium-rich cathode material, Li1.2Ni0.2-xCo2xMn0.6-xO2 (x = 0-0.05) was successfully synthesized using a sol-gel method, followed by heat treatment. The effects of trace amount of cobalt doping on the structure, morphology, and low-temperature (-20 °C) electrochemical properties of these materials are investigated systematically. X-ray diffraction (XRD) results confirm that the Co has been doped into the Ni/Mn sites in the transition-metal layers without destroying the pristine layered structure. The morphological observations reveal that there are no changes of morphology or particle size after Co doping. The electrochemical performance results indicate that the discharge capacities and operation voltages are drastically lowered along with the decreasing temperature, but their fading rate becomes slower when increasing the Co contents. At -20 °C, the initial discharge capacity of sample with x = 0 could retain only 22.1% (57.3/259.2 mAh g(-1)) of that at 30 °C, while sample with x = 0.05 could maintain 39.4% (111.3/282.2 mAh g(-1)). Activation energy analysis and electrochemical impedance spectroscopy (EIS) results reveal that such an enhancement of low-temperature discharge capacity is originated from the easier interface reduction reaction of Ni(4+) or Co(4+) after doping trace amounts of Co, which decreases the activation energy of the charge transfer process above 3.5 V during discharging.

A Novel Strategy to Suppress Capacity and Voltage Fading of Li‐ and Mn‐Rich Layered Oxide Cathode Material for Lithium‐Ion Batteries

“…For the prolonged cycling stability (Figure 1b), the CMC10 cathode exhibits the discharge capacity of 152 mA h g −1 and the capacity retention 83% of the initial discharge capacity of 183 mA h g −1 after 500 cycles at 200 mA g −1 , but the PAN10 and PVDF10 electrodes illustrate the poor prolonged cycling performance with capacity retention only 37% and 40%, respectively. [40] The fitted results (Table S2, Supporting Information) demonstrate that the charge transfer resistance (R ct ) value (134.05 Ω) of the CMC10 electrode is larger than those of the PVDF10 and PAN10 (90.01 and 78.48 Ω) electrodes, which can be ascribed to the lower electronic conductivity of the CMC10 electrode. The equivalent circuit based on this Nyquist plots is applied to fit the primary data from EIS measurements ( Figure S2c, Supporting Information).…”

Li‐ and Mn‐Rich Cathode Materials: Challenges to Commercialization

“…Energy Mater. [90] Doping with cations such as Ru, [91] Sn, [92] or Mo [57] has been reported to expand the interslab spacing and increase the rate capability of LMR cathode materials though with different compositions. Generally, a suitable amount of Co is beneficial for improving the electrical conductivities and decreasing the activation energy of the charge transfer process in LMR cathodes, which enhances the discharge capacity of LMR cathodes at different current densities [89] and also improves the low temperature performance.…”

Recent Progress in Structural and Electrochemical Properties in Composite Based LiFePO4 Batteries

“…In particular, the olivine type LiFePO 4 (triphylite) has attracted much attention as a suitable cathode material [9,60]. LiFePO 4 has been extensively studied because of its attractive properties such as inexpensiveness, non toxicity, high theoretical capacity (170mAhg −1 ), excellent cycling and thermal stability [5,8,61,62]. Figure 6 showed the unit cell structure of the 1 st neighboring distances of LiFePO 4 by using the Gnxas program and lattice parameters are taken from the ref [63].…”

“…So Co was replaced with Ni. So LiNiO 2 , which also forms the α-NaFeO 2 structure, is lower in cost and has a higher energy density (15% higher by volume, 20% higher by weight) but is less stable and less ordered [8] as compared to LiCoO 2 . Another promising cathode material is LiMn 2 O 4, which is lower in cost and safer than LiCoO 2 .…”

“…LiCoO 2 is found reasonably thermally and chemically stable and environmental friendly. However, there are associated challenges as well, such as its low conductivity and reversible capacity [7][8][9][10]. Also, Co is less available and expansive as compared other transition metals such as Mn, Ni and Fe.…”