Structural and magnetic properties of LiNi
 0.5
 Mn
 1.5
 O
 4
 and LiNi
 0.5
 Mn
 1.5
 O
 4−δ
 spinels: A first-principles study

Ben

et al. 2018

Adv Materials Inter

electric vehicles, hybrid electric vehicles, and plug-in hybrid electric vehicles. [1][2][3][4] High energy density materials for LIBs are strongly desired to further enhance the electrochemical performance, creating the next generation of LIBs. [5] The current market of cathode materials is dominated by LiCoO 2 , which offers limited energy density and suffers from high cost and safety problems. [6] To increase the energy density, high voltage cathode materials for LIBs have received much interest, among which the spinel LiNi 0.5 Mn 1.5 O 4 (LNMO) is well-known for its high operation voltage of ≈4.7 V compared to that of Li + / Li, high specific capacity of 146.7 mAh g −1 , high rate capability, low cost, nontoxicity, and good safety features. [7][8][9][10][11] Despite the advantages, the highvoltage LNMO cathode material still has several issues that need to be solved urgently before commercialization. Particularly, LNMO suffers from a capacity fading issue caused by surface structural distortion and associated dissolution of Mn ions into the electrolyte during electrochemical cycling at elevated temperature. [12,13] In addition, the high operating voltage exceeds the stability window of standard electrolytes, which results in the oxidation of electrolytes and the formation of a cathode electrolyte interface on the surface of the cathode, which consequently increased impedance and decreased columbic efficiency during cycling. [12,13] These issues indicate that a major challenge for the LNMO system is related to the interface stability between the cathode and the electrolyte at high temperatures and high voltages.To further improve the electrochemical performance of LNMO, surface modifications with a small amount of metal oxides for LNMO particles have been studied in several experimental studies. [14][15][16][17][18][19][20][21][22] Wang et al. reported Ru-doped Li 1.1 Ni 0.35 Ru 0.05 Mn 1.5 O 4 and LiNi 0.4 Ru 0.05 Mn 1.5 O 4 enhanced rate capability and cyclic performance by minimizing polarization and improving electrical conductivity. [14] Yi et al. found that Nb doping increased the diffusion coefficient of the lithium ion of LNMO by enlarging the lattice parameter, thus improving the electrochemical performance. [16] Yan et al. reported that a thin Al 2 O 3 coating layer on the surface of Li 1.2 Ni 0.2 Mn 0.6 O 2Surface modification of a high-voltage spinel LiNi 0.5 Mn 1.5 O 4 cathode is a common method to improve its cycling performance for next generation lithium-ion batteries, but the exact surface structural stabilization mechanism is not well-understood. Here, detailed density function theory investigations based on the first-principles calculations of high valence state Ti-/ Ta-surfacedoped LiNi 0.5 Mn 1.5 O 4 are reported. The migration of Ni/Mn ions is simulated into the surface structure of bare and Ti-/Ta-coated LiNi 0.5 Mn 1.5 O 4 . The calculation results suggest that Ti/Ta doping promotes Ni/Mn migration toward the formation of the rocksalt phase. Integrated net spin suggests that the valence...

mentioning

confidence: 99%

Impact of High Valence State Cation Ti/Ta Surface Doping on the Stabilization of Spinel LiNi_0.5Mn_1.5O₄ Cathode Materials: A Systematic Density Functional Theory Investigation

Ben

et al. 2018

Adv Materials Inter

“…The LiNi 0.375 Mn 1.625 O 4 supercell, on the other hand, was modeled with a the cubic disordered Fd

\bar{3}

m phase, which is known to be the most stable phase for a similar LiNi 0.5 Mn 1.5 O 4 system [38,39] and was also verified by SAED to be dominant in our as-prepared LNMO. The stoichiometric LiNi 0.375 Mn 1.625 O 4 supercell of 56 atoms considered in this work consisted of 8 Li, 3 Ni, 13 Mn and 32 O atoms.…”

Section: Resultsmentioning

confidence: 66%

“…To account for strong on-site Coulomb repulsion for the 3D electrons of the Mn and Ni atoms, the Hubbard parameter U was added to the GGA functional in the rotationally invariant approach [55], in which only the difference (U eff = U−J) between the Coulomb repulsion U and screened exchange J parameters must be specified. In the present work, we chose U eff = 4.5 eV for both Mn and Ni, as these values have been shown to produce reasonably good estimates in previous studies [36,37,38]. The calculated lattice constants and bond lengths were benchmarked thoroughly against results from previous studies and are provided in the Supplementary Materials.…”

Section: Methodsmentioning

confidence: 99%

See 1 more Smart Citation

Electrochemical and Electronic Charge Transport Properties of Ni-Doped LiMn2O4 Spinel Obtained from Polyol-Mediated Synthesis

et al. 2018

LiNi0.5Mn1.5O4 (LNMO) spinel has been extensively investigated as one of the most promising high-voltage cathode candidates for lithium-ion batteries. The electrochemical performance of LNMO, especially its rate performance, seems to be governed by its crystallographic structure, which is strongly influenced by the preparation methods. Conventionally, LNMO materials are prepared via solid-state reactions, which typically lead to microscaled particles with only limited control over the particle size and morphology. In this work, we prepared Ni-doped LiMn2O4 (LMO) spinel via the polyol method. The cycling stability and rate capability of the synthesized material are found to be comparable to the ones reported in literature. Furthermore, its electronic charge transport properties were investigated by local electrical transport measurements on individual particles by means of a nanorobotics setup in a scanning electron microscope, as well as by performing DFT calculations. We found that the scarcity of Mn3+ in the LNMO leads to a significant decrease in electronic conductivity as compared to undoped LMO, which had no obvious effect on the rate capability of the two materials. Our results suggest that the rate capability of LNMO and LMO materials is not limited by the electronic conductivity of the fully lithiated materials.

“…For example, using density functional theory, professor S. Shi and his team studied the magnetic properties of LNMO with two space groups ( P 4 3 32 and Fd 3̄ m ) and demonstrated that LNMO with the Fd 3̄ m space group with O vacancies has higher electronic conductivity than LNMO with the P 4 3 32 space group. 117…”

Section: Discussionmentioning

confidence: 99%

Advances in modification methods and the future prospects of high-voltage spinel LiNi_0.5Mn_1.5O₄— a review

Fu¹,

Lu²,

Yao³

et al. 2023

J. Mater. Chem. A