Anchoring Interfacial Nickel Cations on Single-Crystal LiNi_0.8Co_0.1Mn_0.1O₂ Cathode Surface via Controllable Electron Transfer

Abstract

Severe Ni dissolution and the resulting impedance rise for the single-crystal LiNi 0.8 Co 0.1 Mn 0.1 O 2 cathode is the main challenge greatly hindering its industrial applications. Herein, we propose a novel concept of anchoring interfacial nickel cations on a single-crystal LiNi 0.8 Co 0.1 Mn 0.1 O 2 cathode through controllable electron transfer. This strategy is realized by applying an ultrathin PMMA surface layer. Different from traditional physical coatings, electron transfer from Ni 2+ to the ester group is confirmed, which contributes to anchoring the interfacial Ni cations and effectively inhibits Ni dissolution into the organic electrolyte. Meanwhile, Li diffusion on the cathode surface is significantly improved. As a result, the electrochemical performance of the LiNi 0.8 Co 0.1 Mn 0.1 O 2 cathode with a PMMA layer is improved. A reversible capacity of 181.1 mAh g −1 at 1C rate is obtained with enhanced rate capability and cycling stability. Moreover, the modified LiNi 0.8 Co 0.1 Mn 0.1 O 2 is able to work well at high voltage and high temperature, especially with incorporation of polyvinylidene fluoride.

Al-doping enables high stability of single-crystalline LiNi0.7Co0.1Mn0.2O2 lithium-ion cathodes at high voltage

“…The oxidation peaks (around 3.82 V) of NCM-0.2Al at rst cycle shi slightly toward a lower potential compared with that of the pristine (3.94 V), indicating the reduced Ni 2+ contents and alleviative polarization of NCM-0.2Al materials by the strategy of Aldoping. [24][25][26] In addition, the EIS results aer 90 cycles (Fig. 5c, d and Table S3 †) illustrate that the sample of NCM-0.2Al possesses the lower resistance value and higher D Li + (5.3278 Â 10 À11 cm 2 s À1 ) than that of NCM (4.6542 Â 10 À11 cm 2 s À1 ), showing the superior reaction kinetics.…”

Robust Surface Reconstruction Induced by Subsurface Ni/Li Antisites in Ni‐Rich Cathodes

“…[ 3 ] Accordingly, LiNi 0.8 Mn 0.1 Co 0.1 O 2 (NMC811) is capable of approaching an energy density of 300 Wh kg –1 at the cell level and is therefore assumed as one of the most promising cathode materials. [ 4 ]…”

“…Despite the desirable energy density, NMC811 suffers from rapid capacity decay, voltage fading, and thermal instability as compared to lower‐Ni‐content oxide cathodes. [ 5 ] Oxygen loss [ 6 ] and transition metal (TM) dissolution [ 4a ] are two pivotal problems that result in gradual phase transition from layered to spinel or rock salt‐like structures at the surface of NMC811, [ 7 ] thus leading to continuous electrochemical performance decay. Although the loss of TM and O ions at surface is widely known, the atomic‐scale outward migration paths of TM and O ions at surface have not been experimentally observed.…”

“…Although the loss of TM and O ions at surface is widely known, the atomic‐scale outward migration paths of TM and O ions at surface have not been experimentally observed. To suppress the loss of active materials, surface coating [ 4a ] and doping [ 8 ] are prevalent surface protection strategies, but they are usually hampered by anisotropic stress and low conductivity due to the incoherent coating layer or complicated doping mechanisms. Recently, the antisite‐rich surface structure in layered oxide cathodes, [ 9 ] so‐called Ni‐rich or passivated surface layer, was demonstrated to suppress the performance decay of the cathodes.…”

Rational Design of a Piezoelectric BaTiO3 Nanodot Surface‐Modified LiNi0.6Co0.2Mn0.2O2 Cathode Material for High‐Rate Lithium‐Ion Batteries

“…R s generally represents the Ohmic resistance of the electrolyte and current collector; R sf indicates the resistance of the surface film (including the cathode electrolyte interphase layer and surface modification layer) correspond to the semi-circle of the high-frequency region; The semi-circle of the intermediate frequency region is related to the transfer impedance and is presented by R ct ; W is the Warburg impedance, which on behalf of the diffusion impedance of lithium-ions in the electrode materials. [41,42] The values of R sf and R ct were calculated by fitting all impedance spectra to the equivalent circuits. The R sf value of 0.5 %-NCM622@BTO and pristine NCM622 are 75 Ω cm 2 and 96 Ω cm 2 at the 5 th cycle, respectively.…”