Using Intimate Carbon to Enhance the Performance of NaTi₂(PO₄)₃Anode Materials: Carbon Nanotubes vs Graphite

Abstract

The effect of intermixed carbon nanotubes and graphite on the electrochemical functionality of NaTi 2 (PO 4 ) 3 was examined. Specifically, the performance of NaTi 2 (PO 4 ) 3 made with "intimate carbons" containing carbon nanotubes (or graphite) introduced at the precursor stage was compared to the performance of similar materials made with the carbons added post synthesis. Specifically, different combinations of carbon nanotubes and graphite were used as carbon sources both in the precursor blend prior to sintering as well as conductive additives in the test electrodes. Graphite-coated NaTi 2 (PO 4 ) 3 with additional carbon nanotubes added (post synthesis) as conductive agent exhibited the best overall performance: the first cycle discharge specific capacity is 130 mAh/g (close to theoretical value 133 mAh/g) at 0.1C rate. The combination also exhibits good cycling stability in aqueous electrolyte: 86% capacity retention under continuous charge/discharge without relaxation at 1C rate for 100 cycles. This suggests that fully coating the precursor material with carbon is critical for performance, and that a graphite additive in the precursor phase is more effective than nanotubes at performing this function.

High Performance TiP2O7Based Intercalation Negative Electrode for Aqueous Lithium-Ion Batteries via a Facile Synthetic Route

“…The synergy of the graphite added in precursor with active materials has been discussed in details in our previous work. 33 Fig . S1 shows elemental analysis obtained from energy dispersive X-ray spectroscopy (EDS) where the existence of Ti, P, O and C are confirmed.…”

“…The improvement is mainly attributed to the intimate graphite coating introduced during the sintering stage which improves the stability and rate capability of TiP 2 O 7 as our previous work has demonstrated the effectiveness of intimate carbon in improving cycling and rate capability of NaTi 2 (PO 4 ) 3 . 11,31,33,[35][36][37][38] Fig . 9 shows the rate performance of a LiMn 2 O 4 // C-TiP 2 O 7 cell.…”

Effect of Concentrated Electrolyte on Aqueous Sodium-ion Battery with Sodium Manganese Hexacyanoferrate Cathode

“…16 A stoichiometric mixture of Na 2 CO 3 (99.7%, Kishida Chemical Co., Ltd.), TiO 2 (99%, Sigma-Aldrich), and NH 4 H 2 PO 4 (99%, Wako Pure Chemical Industries Ltd.) was potted into an alumina container along with 3 mmT zirconia balls. The precursor was subsequently prepared by wet ball-milling in acetone at 400 rpm for 1 h. After the acetone was evaporated to obtain a dry mass, the precursor was ground and decomposed at 350°C for 3 h in air to eliminate the ammonia.…”

“…11 Accordingly, we focused on NaClO 4 as a highly soluble conventional sodium salt, because its concentration can be increased to 10 M, which corresponds to 17 m. 12 Since our first report about NTP, 7 it has been used as actually unique anode for aqueous SIB in many literatures. [13][14][15][16][17][18][19][20] NTP has the 2.1 V (vs. Na/Na + ) flat voltage plateau derived from the Ti 4+ /Ti 3+ redox. It is slightly under H 2 evolution potential at pH = 7, nevertheless it is available as anode for aqueous SIB.…”

NaTi₂(PO₄)₃/Carbon and NaTi₂(PO₄)₃/Graphite Composites as Anode Materials for Aqueous Rechargeable Na-ion Batteries

“…NTP/G with additional carbon nanotubes exhibited first cycle discharge capacity of 130 mAh g ¹1 at 0.1 C rate. 30 Pechini method has been widely used in the preparation of electrode materials, such as NaTi 2 (PO 4 ) 3 , LiTi 2 (PO 4 ) 3 and LiCoO 2 , 21,31,32 in which citric acid and ethylene glycol were used as monomers to form the polymeric matrix. However, the formed polymeric matrix was usually decomposed completely during the following calcination process in other works.…”