Ba‐doping to Improve the Cycling Stability of LiNi_0.5Mn_0.5O₂ Cathode Materials for Batteries Operating at High Voltage

Abstract

LiNi0.5−xBaxMn0.5O2 (x=0, 0.03, 0.05, 0.08) samples were prepared by using a combination of co‐precipitation and solid‐state methods. All of the cathode materials were analyzed by inductively coupled plasma mass spectrometry (ICP‐MS), X‐ray diffraction (XRD), Rietveld refinement, X‐ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). The results of them show that we have successfully prepared the target materials, and Ba‐doping can keep the structure stable and lower Li/Ni cation mixing. In addition, Ba‐doping does not change the structure, the chemical states, or the morphology of LiNi0.5Mn0.5O2. The electrochemical properties of the samples were explored systematically by rate performance and charge–discharge tests at room temperature and high temperature. The performances of the cathode materials indicate that 5 mol % Ba‐doping of LiNi0.5Mn0.5O2 can improve the capacity retention at 0.2 C by approximately 41 % and 13 %, at room temperature and 60 °C, respectively. in the range between 2.5 and 4.8 V. In addition, the 5 mol % Ba‐doped material shows better rate performances than that of the un‐doped material, especially at higher current densities. Cyclic voltammetry (CV) and electrochemical impedance spectroscope (EIS) tests were used to analyze the reason for the improved electrochemical properties, which may be attributed to lower Li/Ni cation mixing, higher structural stability, lower polarization, and lower charge transfer resistance.

Recent Progress and Perspective of Advanced High‐Energy Co‐Less Ni‐Rich Cathodes for Li‐Ion Batteries: Yesterday, Today, and Tomorrow

“…[ 56 ] Yin and co‐workers reported that partial Ba‐doping in the Li[Ni 0.5 Mn 0.5 ]O 2 structure improved the structural stability and reduced the Li + /Ni 2+ cation mixing. [ 57 ] Specifically, Ba 2+ is an attractive dopant or substituent owing to its higher bond dissociation energy of the BaO bond (562 kJ mol −1 ) than that of the NiO bond (382.0 kJ mol −1 ) (Figure 4b). [ 58 ] Li and co‐workers suggested that Mg 2+ ‐doped Li[Ni 0.45 Mg 0.05 Mn 0.5 ]O 2 displays enhanced cell performance because the inert Mg 2+ acts as a pillar to stabilize the layered structure.…”

Low-Cost Mn-Based Cathode Materials for Lithium-Ion Batteries

“…Element doping is an efficacious strategy to enhance the electrochemical properties of cathode materials. Numerous elements have been attempted to dope into LiNi 0.5 Mn 0.5 O 2 , such as Al [29,30], Mg [31], Ba [32], Cu [33], Sb [34], Ti [35], Zr [36], Si [37], Mo [38] and F [39]. All these doping ions can suppress the Li/Ni cation mixing in LiNi 0.5 Mn 0.5 O 2 , and further improve the rate capability, specific capacity, and cycling performance.…”

“…This is because Al doping could narrow the size distribution and decrease Li + migration resistance with extended lattice parameter of c axle. Ba doping can effectively promote the cycling performance of LiNi 0.5 Mn 0.5 O 2 because the Ba-O bond has a greater dissociation energy than the Ni-O bond (563 kJ mol -1 vs. 391.6 kJ mol -1 ), which helps to stabilize the crystal structure [32]. As a result, after 100 cycles, Ba-doped LiNi 0.5 Mn 0.5 O 2 can still operate at 97% of its initial specific capacity.…”

“…As a result, after 100 cycles, Ba-doped LiNi 0.5 Mn 0.5 O 2 can still operate at 97% of its initial specific capacity. Cu doping could extend the migration channels of lithium ions in LiNi 0.5 Mn 0.5 O 2 , which, in turn, improves the rate performance effectively [32]. In addition to single-element doping, the double-element co-doping is applied in LiNi 0.5 Mn 0.5 O 2 , which has shown better improvement than single-element doping.…”

Enhanced Li-ion intercalation kinetics and lattice oxygen stability in single-crystalline Ni-rich Co-poor layered cathodes

“…Besides, the resultant strong Ba–O (563 kJ mol −1 ) and Al–O (512 kJ mol −1 ) bonds can effectively stabilize the lattice O. 21,24 These merits endow BA-NCM85 with superior rate ability and cycle stability.…”