Water-Soluble Binders That Improve Electrochemical Sodium-Ion Storage Properties in a NaTi 2 (PO 4 ) 3 Anode

Abstract

Water-soluble binders are demonstrated to provide significantly better capacity, cycle life stability and rate response for NASICON-type NaTi 2 (PO 4 ) 3 Na-ion battery anodes during reversible sodiation compared to electrodes made using polyvinylidene difluoride-containing slurries. The role of carboxymethyl cellulose (CMC) binders on the physical structure and chemical interfacial reactions with sodium-poor NaTi 2 (PO 4 ) 3 are uncovered using electron microscopy and spectroscopy data and we show that a more stable NASICON NaTi 2 (PO 4 ) 3 structure is found from the desodiation process from compensation of sodium deficiencies in the NaTi 2 (PO 4 ) 3 by extra sodium from the CMC binder. When the binder comprises CMC and a styrene butadiene rubber (SBR) additive, the electrode delivers significantly better voltammetric and galvanostatic electrochemical response with a specific capacity of ∼120 mAh g −1 with capacity retention of 90.5% for 500 cycles at 0.2 C (1 C = 133 mAh g −1 ), and ∼54 mAh g −1 at 20 C. The durability of the electrode during cycling and the stability of the redox processes ensures a higher capacity, longer cycle life electrode which is important for sustainable materials development for Na-ion technologies.