Water-Soluble Binders That Improve Electrochemical Sodium-Ion Storage Properties in a NaTi2(PO4)3 Anode

Abstract

Water-soluble binders are demonstrated to provide significantly better capacity, cycle life stability and rate response for NASICON-type NaTi2(PO4)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 NaTi2(PO4)3 are uncovered using electron microscopy and spectroscopy data and we show that a more stable NASICON NaTi2(PO4)3 structure is found from the desodiation process from compensation of sodium deficiencies in the NaTi2(PO4)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.