Microwave-enhanced electrochemical cycling performance of the LiNi_0.2Mn_1.8O₄ spinel cathode material at elevated temperature

Abstract

The well-established poor electrochemical cycling performance of the LiMn2O4 (LMO) spinel cathode material for lithium-ion batteries at elevated temperature stems from the instability of the Mn(3+) concentration. In this work, a microwave-assisted solid-state reaction has been used to dope LMO with a very low amount of nickel (i.e., LiNi0.2Mn1.8O4, herein abbreviated as LMNO) for lithium-ion batteries from Mn3O4 which is prepared from electrolytic manganese oxide (EMD, γ-MnO2). To establish the impact of microwave irradiation on the electrochemical cycling performance at an elevated temperature (60 °C), the Mn(3+) concentration in the pristine and microwave-treated LMNO samples was independently confirmed by XRD, XPS, (6)LiMAS-NMR and electrochemical studies including electrochemical impedance spectroscopy (EIS). The microwave-treated sample (LMNOmic) allowed for the clear exposure of the {111} facets of the spinel, optimized the Mn(3+) content, promoting structural and cycle stability at elevated temperature. At room temperature, both the pristine (LMNO) and microwave-treated (LMNOmic) samples gave comparable cycling performance (>96% capacity retention and ca. 100% coulombic efficiency after 100 consecutive cycling). However, at an elevated temperature (60 °C), the LMNOmic gave an improved cycling stability (>80% capacity retention and ca. 90% coulombic efficiency after 100 consecutive cycling) compared to the LMNO. For the first time, the impact of microwave irradiation on tuning the average manganese redox state of the spinel material to enhance the cycling performance of the LiNi0.2Mn1.8O4 at elevated temperature and lithium-ion diffusion kinetics has been clearly demonstrated.

High-Voltage LiNi0.5Mn1.5O4-δSpinel Material Synthesized by Microwave-Assisted Thermo-Polymerization: Some Insights into the Microwave-Enhancing Physico-Chemistry

“…The details in preparation of the electrochemical cells were reported elsewhere. [19][20][21][22] Coin cells of 2032 configuration were assembled using as-synthesized samples (LMNO, LMNOmic) as cathode, lithium metal as anode, Celgard 2400 as separator, 1M solution of LiPF 6 dissolved in 1:1:1 volume ratio mixture of ethylene carbonate (EC), dimethyl carbonate (DMC) and diethylene carbonate (DEC) as the electrolyte. The coin cells were assembled in an argon-filled glovebox (MBraun, Germany) with moisture and oxygen levels maintained at less than 1 ppm.…”

Cryochemically Processed Li1+yMn1.95Ni0.025Co0.025O4 (y = 0, 0.1) Cathode Materials for Li-Ion Batteries

“…According to the literature data, the apparent lithium diffusion coefficient for LiMn 2 O 4 -based cathode material, where Mn is partly substituted by Ni [44] is varied in the range from 10 −12 to 10 −13 cm 2 s −1 and from 10 −13 to 10 −16 cm 2 ·s −1 for the materials, where Mn is substituted by Ni and Cu, respectively [45]. In our case, the lowest D values are equal to 2.28 × 10 −14 and 2.60 × 10 −14 cm 2 ·s −1 for the potentials 3.9 and 4.1 V, respectively.…”

Enhanced Electrochemical Performance in Ni‐Doped LiMn2O4‐Based Composite Cathodes for Lithium‐Ion Batteries

“…Li/Li + ) and low cost. [31,32] Nevertheless, the Ni-modified LiMn 2 O 4 materials are still unsatisfactory for the commercial demand due to the intrinsic slow ionic diffusivity and low electronic conductivity; [33][34][35] in addition, the doping of Ni does not significantly improve the discharge capacity of the LiMn 2 O 4 -based materials and most of Ni-doped LiMn 2 O 4 materials exhibit relatively low discharge capacities of 110-130 mAh g À1 . [14,15] To overcome these shortcomings of LiMn 2 O 4 materials, many investigations have been carried out, including different synthesismethods (e. g., sol-gel method, [16] one-step precipita-tion method, [17] solid-state reaction method, [18] etc.…”

“…[10,12] Unfortunately, the commercial application of LiMn 2 O 4 -based materialshas been limited due to its low discharge capacity (theoretical capacity~146.7 mAh g À1 ) and fast fading of the capacity, which is caused by the following chemical factors: (1) John-Teller distortion of Mn 3 + ; [12] (2) dissolution of Mn ions via a chemical reaction: 2Mn 3 + !Mn 2 + + Mn 4 + at high electrode potential; [13] and (3) the formation of oxygen vacancies. [31][32][33][34][35][36] On the other hand, the polyanion-type material (Li 2 MnSiO 4 ) has attracted great attention in recent years because of its overwhelming advantages, such as good thermal stability and high theoretical capacity (330 mAh g À1 ). ), partial substitutions of Mn ions by Ni, [19] Co, [20] Al [21] and Ti, [22] and coating modification (e. g., AlPO 4 , Al 2 O 3 , CuO, YBaCu 3 O 7 , SiO 2 , and ZrO 2 [23][24][25][26][27][28][29][30] ).…”