Uniform Na⁺ Doping‐Induced Defects in Li‐ and Mn‐Rich Cathodes for High‐Performance Lithium‐Ion Batteries

Abstract

The corrosion of Li‐ and Mn‐rich (LMR) electrode materials occurring at the solid–liquid interface will lead to extra electrolyte consumption and transition metal ions dissolution, causing rapid voltage decay, capacity fading, and detrimental structure transformation. Herein, a novel strategy is introduced to suppress this corrosion by designing an Na + ‐doped LMR (Li 1.2 Ni 0.13 Co 0.13 Mn 0.54 O 2 ) with abundant stacking faults, using sodium dodecyl sulfate as surfactant to ensure the uniform distribution of Na + in deep grain lattices—not just surface‐gathering or partially coated. The defective structure and deep distribution of Na + are verified by Raman spectrum and high‐resolution transmission electron microscopy of the as‐prepared electrodes before and after 200 cycles. As a result, the modified LMR material shows a high reversible discharge specific capacity of 221.5 mAh g −1 at 0.5C rate (1C = 200 mA g −1 ) after 200 cycles, and the capacity retention is as high as 93.1% which is better than that of pristine‐LMR (64.8%). This design of Na + is uniformly doped and the resultanting induced defective structure provides an effective strategy to enhance electrochemical performance which should be extended to prepare other advanced cathodes for high performance lithium‐ion batteries.

Pseudo‐Bonding and Electric‐Field Harmony for Li‐Rich Mn‐Based Oxide Cathode

“…[1b,13] It is noteworthy that, in clear, the intensities of (003) and (104) diffraction peaks for the pristine sample are stronger than those of the other modified samples, which are perhaps ascribed that the exposure of the basic material is inhibited by the coating layer, suggesting that the coating layer has been adhered on the surface of LMO (Figure 2A). [14] Besides, the clear and distinct splitting diffraction peaks of (006)/(012) and (018)/(110) reveal that the layered structure of all samples is maintained and the bulk structure is not dramatically changed after linkage-functionalized modification, which could boost the Li + shuttling ( Figure 2B). [15] As shown in Figure 2C, the (003) and (104) diffraction peaks of the modified samples are slightly shifted to lower angles compared with the pristine sample, implying that the lattice parameters of a and c are increased, which may be attributed to the insertion of some Ce 3+ into the bulk structure.…”

Na/Al Codoped Layered Cathode with Defects as Bifunctional Electrocatalyst for High‐Performance Li‐Ion Battery and Oxygen Evolution Reaction

“…Thus, the presence of Al in conjunction with Na helps in boosting the electrical conductivity without increasing the resistance across the interphase of electrode and electrolyte. Thus, the presence of reduced charge transfer resistance with defects/dislocations [ 33 ] assists in reduced overpotentials of NaAl‐LRNO .…”

“…It is well-known that the similarity in ionic radius of Na to that of Li could lead to the facile substitution of Na into Li-sites. [33,39] In addition, Na + having a radius slightly larger to that of Li + could increase the interplanar spacing of the Li slab (Figure S3 and Discussion S7, Supporting Information). It acts a blockade to incoming TMs during lithium (de)intercalation, and accentuate facile diffusion of Li + ions showing as a pillaring effect, [29] whereas the positively charged center Al 3+ acts to boost the conductivity and stabilize the structure by impeding the structural transformations.…”

“…In LIB, these defects/dislocations impede the layered‐to‐spinel transformations and promote facile Li diffusion. Na acts as a pillar to expand the Li slab, while Al as a positive centre forms a strong bond with the oxygen framework, [ 33 ] thereby prevents oxygen loss, suppresses phase transition even during high‐cutoff voltage (4.6 V), and ensures long term structural integrity.…”

Electrochemical and Thermal Behavior of Modified Li and Mn‐Rich Cathode Materials in Battery Prototypes: Impact of Pentasodium Aluminate Coating and Comprehensive Understanding of Its Evolution upon Cycling through Solid‐State Nuclear Magnetic Resonance Analysis

“…[18][19][20] Several approaches and advanced treatments have been suggested so far to achieve stable electrochemical performances. Cationic or anionic doping, [21][22][23][24][25] surface coatings using metal oxides [26][27][28] or Li-ion conducting materials [29][30][31] and reactive gas treatment [32][33][34][35] (such as F 2 , NH 3 , SO 2 CO 2 , etc.) at elevated temperatures became useful in receiving stable electrochemical behavior.…”