Investigation of Water‐Soluble Binders for LiNi_0.5Mn_1.5O₄‐Based Full Cells

Abstract

Two water-soluble binders of carboxymethyl cellulose (CMC) and sodium alginate (SA) have been studied in comparison with N-methylpyrrolidone-soluble poly(vinylidene difluoride-co-hexafluoropropylene) (PVdF-HFP) to understand their effect on the electrochemical performance of a high-voltage lithium nickel manganese oxide (LNMO) cathode. The electrochemical performance has been investigated in full cells using a Li 4 Ti 5 O 12 (LTO) anode. At room temperature, LNMO cathodes prepared with aqueous binders provided a similar electrochemical performance as those prepared with PVdF-HFP. However, at 55 °C, the full cells containing LNMO with the aqueous binders showed higher cycling stability. The results are supported by intermittent current interruption resistance measurements, wherein the electrodes with SA showed lower resistance. The surface layer formed on the electrodes after cycling has been characterized by X-ray photoelectron spectroscopy. The amount of transition metal dissolutions was comparable for all three cells. However, the amount of hydrogen fluoride (HF) content in the electrolyte cycled at 55 °C is lower in the cell with the SA binder. These results suggest that use of water-soluble binders could provide a practical and more sustainable alternative to PVdF-based binders for the fabrication of LNMO electrodes.

Tris(trimethylsilyl) Phosphite and Lithium Difluoro(oxalato)borate as Electrolyte Additives for LiNi0.5Mn1.5O4‐Graphite Lithium‐Ion Batteries

“…%) and LiDFOB (2 wt. %) additives are included in the electrolyte, because the intensity of Na 1s peak is decreased compared to the spectra of LP40 sample, and Mn 2p spectra is diminished [41] . This could be the reason behind the high internal resistance as observed in the ICI experiment, and could also advocate less dissolution of Mn into the electrolyte (Figure S6b, top image no cross talk of Mn over graphite surface).…”

“…%) additives are included in the electrolyte, because the intensity of Na 1s peak is decreased compared to the spectra of LP40 sample, and Mn 2p spectra is diminished. [41] This could be the reason behind the high internal resistance as observed in the ICI experiment, and could also advocate less dissolution of Mn into the electrolyte (Figure S6b, top image no cross talk of Mn over graphite surface). On graphite, no Na 1s peak is detected for the cycled graphite in the baseline electrolyte indicating SEI is thicker than probing depth of the XPS analysis (i. e., about 10 nm).…”

Understanding the Capacity Fade in Polyacrylonitrile Binder‐based LiNi0.5Mn1.5O4 Cells**

“…Another interesting observation is that binders with significantly lower theoretical oxidative stability than PAN, such as carboxymethyl cellulose (CMC), has been shown to function as equally well as PVdF-HFP binders in several battery cathode chemistries, including LNMO. [36][37][38][39] The probable reason for the good performance of binders such as CMC could be that any decomposition products formed during cell cycling form a stable passivating layer on the cathode, allowing for stable cycling. This implies that kinetic stability, rather than thermodynamic stability, is the deciding factor in a practical high-voltage cell.…”

Understanding the capacity fade in polyacrylonitrile binder-based LiNi0.5Mn1.5O4 cells

“…Another interesting observation is that binders with significantly lower theoretical oxidative stability than PAN, such as carboxymethyl cellulose (CMC), has been shown to function as equally well as PVdF-HFP binders in several battery cathode chemistries, including LNMO. [34][35][36][37] The probable reason for the good performance of binders such as CMC could be that any decomposition products formed during cell cycling form a stable passivating layer on the cathode, allowing for stable cycling. This implies that kinetic stability, rather than thermodynamic stability, is the deciding factor in a practical high-voltage cell.…”