Dual-doping to suppress cracking in spinel LiMn₂O₄: a joint theoretical and experimental study

Abstract

Electrochemical cycling stabilities were compared for undoped and Al/Co dual-doped spinel LiMn2O4 synthesized by solid state reactions. We observed the suppression of particle fracture in Al/Co dual-doped LiMn2O4 during charge/discharge cycling and its distinguishable particle morphology with respect to the undoped material. Systematic first-principles calculations were performed on undoped, Al or Co single-doped, and Al/Co dual-doped LiMn2O4 to investigate their structural differences at the atomistic level. We reveal that while Jahn-Teller distortion associated with the Mn(3+)O6 octahedron is the origin of the lattice strain, the networking -i.e. the distribution of mixed valence Mn ions - is much more important to release the lattice strain, and thus to alleviating particle cracking. The calculations showed that the lattice mismatching between Li(+) intercalation and deintercalation of LiMn2O4 can be significantly reduced by dual-doping, and therefore also the volumetric shrinkage during delithiation. This may account for the near disappearance of cracks on the surface of Al/Co-LiMn2O4 after 350 cycles, while some obvious cracks have developed in undoped LiMn2O4 at similar particle size even after 50 cycles. Correspondingly, Al/Co dual-doped LiMn2O4 showed a good cycling stability with a capacity retention of 84.1% after 350 cycles at a rate of 1C, 8% higher than the undoped phase.

Oriented LiMn2O4 Particle Fracture from Delithiation-Driven Surface Stress

“…For instance, manganese ion dissolution into the electrolyte − typically occurs alongside irreversible formation of a static Jahn–Teller-distorted tetragonal phase during cycling (below 3 V vs Li/Li + ) . Additionally, there is a 7.7% volume expansion and contraction for each charge and discharge cycle between LMO and λ-MnO 2 . , The significant volume change between the charged and discharged states leads to lattice mismatch between Li + -rich and Li + -deficient domains in the electrode , and can result in substantial mechanical degradation and particle fracture. ,− As a result, the concentration of defects and reactive surface area of the electrode may increase, accelerating capacity fade and delamination from the current collector. Therefore, further understanding the relationship between stress, strain, and particle fracture is necessary for improving intercalation electrode design and reducing mechanical degradation.…”

Insights into Electrochemistry and Mechanical Stability of α- and β-Li2MnP2O7 for Lithium-Ion Cathode Materials: First-Principles Comparison

“…Lithium ion batteries (LIBs), as one of the most promising candidates for chemical energy storage and conversion devices, have captured a dominant market share of the portable electronics and electric transportation in the past decades. − Because the cathode material is vital for energy storage and cost-effectiveness, tremendous efforts are devoted to design and develop next-generation cathode materials with excellent electrochemical properties. Typical examples comprise the layered LiCoO 2 , − olivine LiMPO 4 (M = Fe and Mn), − and spinel LiMn 2 O 4 . − However, under the ever-increasing usage of LIBs expanding to large-scale application, the conventional cathode materials could not meet the requirement as a consequence of cost-effectiveness or safety hazards. Therefore, searching novel cathode materials for LIBs is an integral aspect of the ongoing quest for building better batteries.…”

Effect of Co3+ Doping on Crystal Structure and Electrochemical Properties of Spinel LiMn2O4 Cathode Material

“…32 The change of the valence distribution state of Mn in LiMn 2−x Co x O 4 effectively releases the lattice tension, which can alleviate the cracking phenomenon on the grain surface during long-cycle charge and discharge. 33 Impressively, when the doping amount of Co was x = 0.04, the initial discharge specific capacity of LMO-0.04 was 115.5 mAh• g −1 , and the discharge specific capacity was still 93.6 mAh•g −1 after 500 cycles. However, when the doping amount of Co was too much (x = 0.06), the cycle performance of the battery will also decrease.…”