Unravelling the Impact of Reaction Paths on Mechanical Degradation of Intercalation Cathodes for Lithium-Ion Batteries

Abstract

The intercalation compounds are generally considered as ideal electrode materials for lithium-ion batteries thanks to their minimum volume expansion and fast lithium ion diffusion. However, cracking still occurs in those compounds and has been identified as one of the critical issues responsible for their capacity decay and short cycle life, although the diffusion-induced stress and volume expansion are much smaller than those in alloying-type electrodes. Here, we designed a thin-film model system that enables us to tailor the cation ordering in LiNi(0.5)Mn(1.5)O4 spinels and correlate the stress patterns, phase evolution, and cycle performances. Surprisingly, we found that distinct reaction paths cause negligible difference in the overall stress patterns but significantly different cracking behaviors and cycling performances: 95% capacity retention for disordered LiNi(0.5)Mn(1.5)O4 and 48% capacity retention for ordered LiNi(0.5)Mn(1.5)O4 after 2000 cycles. We were able to pinpoint that the extended solid-solution region with suppressed phase transformation attributed to the superior electrochemical performance of disordered spinel. This work envisions a strategy for rationally designing stable cathodes for lithium-ion batteries through engineering the atomic structure that extends the solid-solution region and suppresses phase transformation.

An insight into failure mechanism of NASICON-structured Na3V2(PO4)3 in hybrid aqueous rechargeable battery

“…More importantly, the mechanical degradation of Na 3 V 2 (PO 4 ) 3 /C cathode material driven by structure nanocrystallization is the major reason for the more serious capacity fading of Na 3 V 2 (PO 4 ) 3 /C in Na-Zn hybrid aqueous rechargeable battery than that in Zn-ion battery. Cracking induced capacity fading has been confirmed in several lithium ion intercalation cathodes (layered LiCoO 2 , spinel LiMn 2 O 4 , spinel LiNi 0.5 Mn 1.5 O 4 , olivine LiFePO 4 ), which display volume changes only 2 % -7% during Li + ion extraction/insertion [30][31][32][33][34] . Compared to Li ions ( r Li + = 0.73 Å ) and Zn ions ( r Zn 2+ + = 0.74 Å ), the ionic radius of Na ions ( r Na + = 1.13 Å ) is much larger and seems to impact the host structure of electrode more severely during Na + extraction/insertion.…”

Phase transformation mechanism in lithium manganese nickel oxide revealed by single-crystal hard X-ray microscopy

“…Striking inhomogeneity in the strain distribution throughout the particle was also reported. Further evidence was provided by in situ multi-beam optical stress sensor on LMNO thin-film electrodes, which showed that the stress in LMNO increases with lithium removal and it can reach up to 126 MPa at fully delithiated state (MNO)48. Strain survey on Li x MNO crystals was not feasible with FF-TXM as the contrast mechanism of the technique is not sensitive to the local crystal structure distortion.…”

Mechanical stresses at the cathode–electrolyte interface in lithium-ion batteries

“…Nevertheless, it is still unable to claim that these stresses are reasons for mechanical degradation in lithium-ion batteries. As Dr. Nancy Dudney has pointed out, 51 mechanical failure should not be a concern for intercalation-type cathodes, since the volume change upon cycling is only 2-7%, much smaller than that in alloying-type anodes which is typically 100%. Moreover, Christensen and Newman 23 have showed that a compressive external stress could reduce the likelihood of particle fracture because the fracture threshold for the tensile stress is typically much lower than that for the compressive stress.…”