Electrochemical properties of PX-phase PbTiO3 electrode for sodium ion batteries

Abstract

PX-phase PbTiO3 (PT) nanowires have been investigated for the first time as an anode material for sodium ion batteries (NIBs). Their sodium storage properties are presented by employing sodium-carboxyl-methyl-cellulose (CMC) and styrene-butadiene-rubber (SBR) as binders. Electrochemical results show that the PT/CMC-SBR electrode delivers a specific capacity of 84.2 mA h g-1 after 100 cycles. The PT nanowires are found to undergo an irreversible conversion reaction to transform into a composite structure composed of 5-8 nm Pb nanoparticles uniformly dispersed in the amorphous matrixes in the initial discharge process. In the subsequent cycling process, the discharge capacity is primarily attributed to alloying reaction between Pb and Na and conversion reaction between Pb and PbO2. Furthermore, we use polyvinylidene fluoride (PVDF) instead of CMC-SBR as binder to study the influence of binders on the electrochemical performance of PX-phase PT anode. It is found that PT/CMC-SBR electrode exhibits better electrochemical properties than PT/PVDF electrode in both cyclic performance and rate capability. Detailed analysis is conducted to understand the underlying mechanism for the distinct NIBs anode performance of PT nanowires caused by use of different binders. It is found that compared to PT/CMC-SBR electrode, the conversion reaction between Pb and PbO2 is missing in the PT/PVDF electrode, and that Pb active material has diffused out from the wires and reprecipitated as microsized hexagonal particles during the discharge/charge process, leading to the inferior electrochemical performance of PT/PVDF electrodes. This work signifies the importance of binders to optimize the electrochemical performance for alloy anode materials in NIBs.