First‐principle study of doping effects (Ti, Cu, and Zn) on electrochemical performance of Li₂MnO₃ cathode materials for lithium‐ion batteries

Abstract

Li‐rich layered Mn‐based oxide (LMO) cathode materials, with the formation of Li2MnO3, have attracted much attention due to their potential in various applications with high energy density. However, these cathode materials for Lithium‐ion batteries still suffer from drawbacks such as poor rate capability and voltage decay, which makes further investigation vital and rational. Here, the doping strategy is employed to investigate the effect of TM = Ti, Cu, and Zn on Li2Mn0.5TM0.5O3 cathode materials for improving electrochemical performances of Li2MnO3. Electrochemical properties such as voltage, electrical conductivity, safety, structural stability, and kinetics and mechanism of Li‐ion diffusion are evaluated and compared. All doped cathodes decrease the voltage reduction and improve the electrical conductivity coefficient in comparison with LMO. Doping Cu notably increases the electrical conductivity of LMO by 77%. Ti doping exhibits the potential to increase the maximum voltage of LMO and structural stability. Doping Zn and Cu elements can delay the oxygen loss significantly, which leads to a higher life cycle and safety. In addition, doping Zn is expected to have a higher Li‐ion diffusion coefficient due to its low energy barrier and partial charge of oxygen atoms in its cathode structure. This first‐principle study of doping effects of TM = Ti, Cu, and Zn with α = 0.5 in Li2Mn0.5TMαO3 may be a useful leading study for further investigation into the synthesis of lithium‐rich materials with enhanced electrochemical performance.

Modulating Crystal and Interfacial Properties by W‐Gradient Doping for Highly Stable and Long Life Li‐Rich Layered Cathodes

“…In addition, the DFT calculations were implemented to investigate the electronic properties of the oxide structures. Based on the stoichiometric ratio of the Li‐rich cathode materials in our experiments, we fabricated layered supercells of Li 19 Mn 10 Ni 2 Co 1 O 32 (corresponding to pristine LLMO) and Li 19 Mn 10 Ni 2 Co 1 W 1 O 32 with one Mn atom substituted by one W atom (corresponding to W@LLMO) to perform the structure optimization calculations ( Figure a,b), both the total density of state and partial density of state [ 24 ] of the pristine LLMO and the W@LLMO are presented in Figure S4a,b, Supporting Information. According to the density of state results (Figure S4, Supporting Information), both samples display the semiconducting behavior with a small bandgap at E f , indicating relatively high electrical conductivity, which is essential for the electrode materials.…”

Understanding the Activation of Anionic Redox Chemistry in Ti4+-Substituted Li2MnO3 as a Cathode Material for Li-Ion Batteries

“…The on-site Coulomb interaction (PBE + U ) was used to describe the strongly correlated electrons of the Mn and Ti atoms. The Hubbard effective U values for Mn and Ti were taken as 3.9 and 4.2 eV, − respectively. The energy cutoff was set to 500 eV for the plane-wave basis set.…”

Multiscale Investigation into the Co‐Doping Strategy on the Electrochemical Properties of Li2RuO3 Cathodes for Li‐Ion Batteries

“…Mott et al [85] proposed a method for calculating the electrical conductivity coefficient of the conductor and semiconductor materials based on the TDOS data. In this method, the electrical conductivity coefficient of the doped cathodes can be estimated using the electrical conductivity coefficient of the LRO via Equation (16): [85] (16) where f(E) is Fermi-Dirac distribution function as a function of Energy State (E) that is calculated as Equation 17: [86] f E ð Þ ¼ 1 1 þ e ðEÀ E F Þ=kT : (17) The experimental value of the electrical conductivity coefficient for the LRO cathode is 18 (S m À 1 ). [23] For the other cathodes, the electrical conductivity coefficient for the P1D model has been calculated from Equation 17, and summarized in Table 5.…”

“…These include poor rate performance, low energy density, and inferior cycling stability. [5,6] Recently, lithium-rich layered oxides (LLOs) have received a lot of attention as promising cathode materials, [7][8][9][10][11][12][13][14][15][16] which can be generally written as Li 2 MO 3 (M=Mn, Co, Ru, etc.). Although LLO cathodes have shown efficient characteristics like high reversible capacity (above 250 mAh g À 1 ) [17] in a higher operational voltage (4.8, vs. Li + /Li) [18] and high energy density (1000 Wh kg À 1 ), [17] many efforts have been made to enhance the electrochemical properties of these positive cathodes to tackle the drawbacks such as first cycle capability loss and poor structural stability.…”