Scalable Nitrate Treatment for Constructing Integrated Surface Structures to Mitigate Capacity Fading and Voltage Decay of Li‐Rich Layered Oxides

Abstract

Capacity fading and voltage decay is one of the biggest obstacles for the practical application of Li‐rich layered oxides due to the serious surface‐related detrimental reactions. Herein, we develop a versatile and scalable method to construct a robust surface‐integrated structure. All the designed samples deliver outstanding capacity and voltage stability, among which the Zn‐treated sample possesses the best electrochemical performance. Its capacity retention is larger than 90 % after 400 cycles with a voltage decay ratio as small as 0.73 mV per cycle. What is more, the rules of surface‐integrated structure with different cations in terms of capacity and voltage stability is further deciphered by combining with density function theory (DFT) calculations. It is found that to obtain advanced Li‐rich layered oxide cathodes, cations in Li‐sites should firstly ensure the binding energy of the surface‐integrated structure in a lower level and then provide Bader charge for the nearest O atoms as small as possible.

Modulating local electronic structure enhances superior electrochemical activity in Li-rich oxide cathodes

“…1b and S2b †). Based on the equation between the average valence state of Mn (Mn AVS ) and the splitting energy of Mn 3s (DE), Mn AVS = 8.956 − 1.126DE, 34,35 the Mn AVS in LMO, B-LMO and B-LMO-600 was calculated to be +3.89, +3.97 and +3.90, respectively. Meanwhile, compared with LMO, a shi of Mn 2p spectra to higher energies is observed in B-LMO (Fig.…”

Constructing an Inhomogeneous Surface to Suppress the Capacity Decay of Li-Rich Layered Cathode Materials

“…All the samples appear a slope region between 3.7 and 4.4 V and an evident long plateau region at about 4.5 V in the initial charge curves. The slope region is attributed to the extraction of Li + ions from the rhombohedral LiTMO 2 and TM ion oxidation of Ni 2+ to Ni 4+ , while the typical plateau at 4.5 V is ascribed to oxygen activation and the electrochemical activation of monoclinic Li 2 MnO 3 phase (Li 2 MnO 3 → Li 2 O + MnO 2 ) . Note that both M-LMNO and N-LMNO samples exhibit shorter charging plateau than the P-LMNO sample.…”

Phosphorylation of Li-Rich Mn-Based Layered Oxides for Anion Redox and Structural Stability

“…The binding energy of P 2p is 133 eV, referring to PO 4 3– , manifesting the metal phosphate formed on the surface, − and the phosphate ion was induced to the oxygen site. It suggests that surface labile oxygen can be removed by phosphorylation, leading to the reduction of σ bonding O 2p states, which can enhance the structural stability . This also implies that TM ions on the surface layer have migrated.…”

“…It suggests that surface labile oxygen can be removed by phosphorylation, leading to the reduction of σ bonding O 2p states, 7 which can enhance the structural stability. 37 This also implies that TM ions on the surface layer have migrated. Therefore, XPS results interpret that phosphorylation does not change the oxidation state of the TM in the samples and the rearrangement of the surface structure may have occurred.…”