Influences of surface Al concentration on the structure and electrochemical performance of core-shell LiNi0.8Co0.15Al0.05O2 cathode material

Understanding the Feasibility of Manganese Substitution for Cobalt in the Synthesis of Nickel-Rich and Cobalt-Free Cathode Materials

“…36 The sloping lines in the lowfrequency region indicate the intergranular contact impedance and the Warburg diffusion impedance of lithium ions in the material. 3,7,30 As shown in Table 4, the R ct values of the Mn partially substituted materials after activation were all greater than those of the LNCA materials, indicating that Mn may not be as effective as Co in stabilizing the layered structure of materials. However, the R ct values of the Mn-substituted materials did not change much before and after activation.…”

“…The size of this semicircle is attributed to the migration resistance of lithium ions through the solid electrolyte interphase (SEI) film and is mainly determined by the thickness of the SEI film; the diameter of the semicircle is a measure of the charge-transfer resistance, which is related to the contact between the particles, between the electrode and the electrolyte, and the surface quality of the active material and the variation of R ct is related to the structural collapse and side reactions occurring on the surface of the electrode material . The sloping lines in the low-frequency region indicate the intergranular contact impedance and the Warburg diffusion impedance of lithium ions in the material. ,, As shown in Table , the R ct values of the Mn partially substituted materials after activation were all greater than those of the LNCA materials, indicating that Mn may not be as effective as Co in stabilizing the layered structure of materials. However, the R ct values of the Mn-substituted materials did not change much before and after activation.…”

“…The ratio of I (003)/(104) , which represents the degree of Ni Li mixing, and the ratio of lattice constant c/a, which reflects the degree of lattice deviation from a cubic symmetric structure, both decreased with the increase in the Mn content and the decrease in the Co content, indicating that the degree of mixing of materials gradually became serious, but the value of c/a was not lower than 4.9, indicating that the lattice expansion of materials was still in the cubic phase although there was a slight expansion. 7,23 The cell volume also became larger with the increase in the Mn content, and the larger unit cell volume is favorable to reduce the potential barrier of lithium transition, 26 which will affect the lithium-ion diffusion coefficient of materials. Since the radii of Co 3+ (0.54 Å) and Mn 4+ (0.53 Å) are essentially the same, considering the corresponding ionic radius of Ni 2+ (0.69 Å) and Ni 3+ (0.60 Å) and the charge balance of materials, the increase in Mn substitution for Co might lead to an increase in the Ni 2+ concentration, which further led to the expansion of lattice parameters a and b and promoted to form a higher degree of cation mixing and a worse degree of layered structure formation, which, in turn, affected the cyclic and multiplicative properties of materials.…”

“…Nevertheless, the high Ni content of ternary materials will make their properties approach LiNiO 2 , leading to the deterioration of the stability and safety of the materials. , The instability of the electrode material structure is the main reason for the capacity fading of Ni-rich materials. At present, exogenous metal ions are used as dopants to integrate into the host structure to improve and solve the problem of the instability of the structure. − After the report that Ni ions were partially replaced by Co ions, a large number of studies focused on the substitution of Ni ions with limited Co and Mn to reduce the cost and improve the performance . Many researchers found that Co 3+ can inhibit the phase transformation of LiNiO 2 and stabilize the lamellar structure.…”

Enhancing the Electrochemical Performance of Ni-Rich LiNi0.88Co0.09Al0.03O2 Cathodes through Tungsten-Doping for Lithium-Ion Batteries

“…Numerous strategies have been employed to strengthen the host structure by doping, coating, and establishing special architectures such as the core-shell model [9,13,27,30]. Atomic doping is widely considered to enjoy a promising development, with simple operation to significantly improve battery lifetime, rate capability, and structural integrity of nickel-rich cathode materials.…”