Improving the rate performance of LiNi0.5Mn0.5O2 material at high voltages by Cu-doping

Cobalt‐Free Cathode Materials: Families and their Prospects

“…[47] A study has shown that the capacity of 1 mol% Cu 2+ -doped LiNi 0.5 Mn 0.5 O 2 is 18% higher than that of the original LiNi 0.5 Mn 0.5 O 2 in the range of 2.5-4.6 V at 0.2C. [141] Li et al [142] reported LiNi 0.495 Mn 0.495 Mo 0.01 O 2 possesses a high capacity of 180 mAh g −1 at 20 mA g −1 , while the undoped LiNi 0.5 Mn 0.5 O 2 only has the capacity of 156 mAh g −1 . It has been explained that Mo as a dopant can hinder Li + /Ni 2+ disordering and suppress phase transformations close to the surface of the electrode, and at intragranular grain boundaries of particles, thus enhancing reversible capacity and cycling stability.…”

“…[ 47 ] A study has shown that the capacity of 1 mol% Cu 2+ ‐doped LiNi 0.5 Mn 0.5 O 2 is 18% higher than that of the original LiNi 0.5 Mn 0.5 O 2 in the range of 2.5–4.6 V at 0.2C. [ 141 ] Li et al. [ 142 ] reported LiNi 0.495 Mn 0.495 Mo 0.01 O 2 possesses a high capacity of 180 mAh g −1 at 20 mA g −1 , while the undoped LiNi 0.5 Mn 0.5 O 2 only has the capacity of 156 mAh g −1 .…”

Understanding the Stability of LiNi0.5Mn0.5O2 as a Co-Free Positive Electrode

“…16 The poor rate capacity is considered to be predominantly attributed to cation mixing at the lithium site; therefore, the strategy of straining the lattice through ion doping has been extensively used to prevent nickel from occupying the lithium site. 17 The theory regarding the presence of Ni 2+ and Mn 4+ ions in LiNi x Mn 1−x O 2 originated from conventional element valence analyses using X-ray photoelectron spectroscopy (XPS) 18 and cyclic voltammetry. 19 However, XPS can only characterize the properties of a material originating from a few nanometers below the surface, 20 and the redox potentials of Ni 2+ /Ni 3+ and Ni 3+ / Ni 4+ determined via cyclic voltammetry are too similar to be distinguished.…”

“…Hence, considerable efforts have been devoted to elucidating these problems and improving the electrochemical properties based on the above-mentioned assumptions. − For example, the capacity loss during the initial cycles is considered to arise from the surface reaction of the cathode with the electrolyte; thus, various coating methods have been developed to isolate the cathode from the electrolyte . The poor rate capacity is considered to be predominantly attributed to cation mixing at the lithium site; therefore, the strategy of straining the lattice through ion doping has been extensively used to prevent nickel from occupying the lithium site . The theory regarding the presence of Ni 2+ and Mn 4+ ions in LiNi x Mn 1– x O 2 originated from conventional element valence analyses using X-ray photoelectron spectroscopy (XPS) and cyclic voltammetry .…”

Understanding the Stability for LiNi0.5Mn0.5O2 as a Co-free positive electrode material

“…A lot of efforts have been made to elucidate these problems and to improve the electrochemical properties based on the above mentioned assumptions [8][9][10][11][12][13][14][15][16]. For example, the capacity loss during the initial cycles was considered to be arising from surface reaction of cathode with electrolyte, so various coating methods have been developed to isolate the cathode from electrolyte [16]; the poor rate capacity was consider to mainly be attributed to cation mixing at lithium site, so a strategy has been widely used that lattice was strained by ions doping to inhibit nickel occupying the lithium site [17]. This theory about N i 2+ and M n 4+ in LiN i x M n 1−x O 2 originated from the conventional element valence analysis characterized by X-ray photoelectron spectroscopy (XPS) [18] and cyclic voltammetry [19].…”