Effect of Concentrated Electrolyte on High Voltage Aqueous Sodium-ion - PowerPoint PPT Presentation

Effect of Concentrated Electrolyte on High Voltage Aqueous Sodium-ion Battery Kosuke Nakamoto, Ayuko Kitajou*, Masato Ito* and Shigeto Okada* (IGSES, Kyushu University, *IMCE, Kyushu University) Oct 6. (Thu) A01-0134

Introduction

Commercialized secondary batteries and post lithium-ion batteries Electrolyte Aqueous Organic Solid Commercial Nickel metal hydride Lithium-ion Sodium sulfur Post LIB Aqueous lithium-ion Sodium-ion This study Aqueous sodium-ion Advantage Non-inflammability, Cost, P ower � /disadvantage Energy density Hybrid capacitor (Aquion Energy) Components Lithium-ion Aqueous sodium-ion Electrolyte solvent Organic Water Electrolyte salt LiPF 6 , LiTFSI Na 2 SO 4 , NaClO 4 Separator Polypropylene porous Nonwoven fabric Anode current collector Cu Fe Cathode active material Co, Ni Fe, Mn Electrode slurry thickness ~ 100 µ m ~ 20,000 µ m Operation voltage ~ 4 V ~ 2 V Primary requirement to the large scale energy storage system is the cost (Wh/$), rather than specific energy density (Wh/kg).

Electrode materials for aqueous lithium-ion battery 2 5 LiNi 0.5 Mn 1.5 O 4 4 LiCoO 2 LiMn 2 O 4 1 LiNi 0.5 Mn 1.5 O 4 E = 1.23 – 0.059pH 1 4 O 2 ↑ LiFePO 4 E (V) vs. Na/Na + 3 Theoretical stability window LiMn 2 O 4 0 E (V) vs. NHE E (V) vs. Ag/AgCl E (V) vs. Li/Li + 0 of water 3 Mo 6 S 8 LiV 3 O 8 Polyimide H 2 ↑ VO 2 LiTi 2 (PO 4 ) 3 Mo 6 S 8 2 -1 E = – 0.059pH -1 2 TiO 2 Li 4 Ti 5 O 12 1 -2 -2 1 Extended practical stability window of aqueous lithium-ion electrolyte 0 -3 -3 0 0 7 14 pH Very recent aqueous lithium-ion battery with highly concentrated electrolyte realized high voltage operation exceeding 1.23 V theoretical stability window.

Aqueous lithium-ion batteries Voltag Discharge capacity Cathode Anode Electrolyte e Ref. /mAh g -1 /V LiMn 2 O 4 VO 2 5 mol/l LiNO 3 aq. 1.5 50 (electrodes) 1 LiNi 0.81 Co 0.19 O 2 LiV 3 O 8 1 mol/l Li 2 SO 4 aq. 0.9 20 (electrodes) 2 LiMn 2 O 4 LiTi 2 (PO 4 ) 3 1 mol/l Li 2 SO 4 aq. 1.5 40 (electrodes) 3 LiFePO 4 LiTi 2 (PO 4 ) 3 1 mol/l Li 2 SO 4 aq. 0.9 55 (electrodes) 4 LiCoO 2 Polyimide 5 mol/l LiNO 3 aq. 1.1 71 (electrodes) 5 LiMn 2 O 4 Mo 6 S 8 21 mol/kg LiTFSI aq. 2.0 47 (electrodes) 6 21 mol/kg LiTFSI LiMn 2 O 4 TiO 2 2.1 48 (electrodes) 7 + 7 mol/kg LiOTf aq. LiCoO 2 2.4 55 (electrodes) 20 mol/kg LiTFSI Li 4 Ti 5 O 12 8 + 8 mol/kg LiBETI aq. LiNi 0.5 Mn 1.5 O 4 3.0 30 (electrodes) Estimated cost of recent aqueous lithium-ion chemistries is still high. [1] W. Li, et al. , Science , 264 (1994) 1115. [2] J. Köhler, et al. , Electrochim. Acta , 46 (2000) 59. [3] J.Y. Luo, et al. , Adv. Funct. Mater. , 17 (2007) 3877. [4] J. Luo, et al. , Nat. Chem. , 2 (2010) 76 [5] H. Qin, et al. , J. Power Sources , 249 (2014) 367. [6] L. Suo, et al. , Science , 350 (2015) 938. [7] L. Suo, et al. , Angew. Chemie. , 85287 (2016) 7136. [8] Y. Yamada, et al. , Nat. Energy , 1 (2016) 16129.

Aqueous sodium-ion batteries *10 M NaClO 4 aq. ≒ 17 m NaClO 4 aq. Voltage Discharge capacity Cathode Anode Electrolyte Ref. /V /mAh g -1 λ -MnO 2 Active Carbon 1 mol/l Na 2 SO 4 aq. 1.2 50 (electrolyte) 9 NaVPO 4 F Polyimide 5 mol/l NaNO 3 aq. 1.1 40 (electrodes) 5 Na 3 V 2 O(PO 4 ) 2 F NaTi 2 (PO 4 ) 3 *10 mol/l NaClO 4 aq. 1.4 40 (cathode) 10 Na 4 Mn 9 O 18 NaTi 2 (PO 4 ) 3 1 mol/l Na 2 SO 4 aq. 1.0 100 (anode) 11 Na 2 FeP 2 O 7 NaTi 2 (PO 4 ) 3 4 mol/l NaClO 4 aq. 0.9 48 (cathode) 12 Na 2 Ni[Fe(CN) 6 ] NaTi 2 (PO 4 ) 3 1 mol/l Na 2 SO 4 aq. 1.3 100 (anode) 13 Na 2 Cu[Fe(CN) 6 ] NaTi 2 (PO 4 ) 3 1 mol/l Na 2 SO 4 aq. 1.4 102 (anode) 14 NaCr[Mn(CN) 6 ] Na 2 Mn[Mn(CN) 6 ] *10 mol/l NaClO 4 aq. 1.0 28 (electrodes) 15 Na 2 Co[Fe(CN) 6 ] NaTi 2 (PO 4 ) 3 1 mol/l Na 2 SO 4 aq. 1.6 120 (cathode) 16 NaFe[Fe(CN) 6 ] (Active Carbon) 1 mol/l Na 2 SO 4 aq. (> 1.5) 60 (cathode) 17 We focus on rocking-chair aqueous sodium-ion batteries (not capacitors). Active materials should be low cost & yield high voltage output to maximize the cost performance index. [9] J.F. Whitacre, et al. , J. Power Sources , 213 (2012) 255. [10] P.R. Kumar, et al ., Mater. Chem. A , 3 (2015) 6271. [11] W. Wu, et al ., J. Electrochem. Soc., 162 (2015) A803. [12] K. Nakamoto, et al ., J. Power Sources , 327 (2016) 327. [13] X. Wu, et al ., Electrochem. Commun., 31 (2013) 145. [14] X. Wu, et al ., ChemSusChem , 7 (2014) 407. [15] M. Pasta, et al ., Nat. Commun., 5 (2014) 3007. [16] X. Wu, et al ., ChemNanoMat., 1 (2015) 188. [17] X. Wu, et al ., Nano Energy , 13 (2015) 117.

Sodium metal hexacyanoferrates Na 2 M[Fe(CN) 6 ], M = Ni, Cu, Fe, Co, Mn M Ni Cu Co Fe E[V] vs. Ag/AgCl After Wu [13] After Wu [14] After Wu [16] After Wu [17] 1.0 O 2 ↑ 0.5 0.0 150 Capacity [mAh/g] Capacity [mAh/g] 150 0 Capacity [mAh/g] 150 150 Capacity [mAh/g] Initial C/D capacity 74/65 71/59 142/128 102/122 /mAh g -1 E/V vs. 0.9 1.0 0.5 0.6 0.4 0.2 Ag/AgCl Electrolyte 1 mol/l Na 2 SO 4 aq. 1 mol/l Na 2 SO 4 aq. 1 mol/l Na 2 SO 4 aq. 1 mol/l Na 2 SO 4 aq. Upper Inactive Inactive [Fe(CN) 6 ] 4-/3- Fe 2+/3+ redox Lower [Fe(CN) 6 ] 4-/3- [Fe(CN) 6 ] 4-/3- Co 2+/3+ [Fe(CN) 6 ] 4-/3- redox Weak Low capacity Low capacity Low initial capacity Expensive Expensive Expensive Air-stability point Na 2 Mn[Fe(CN) 6 ] is low cost and was reported high voltage operation in non-aqueous electrolyte but has never been realized in aqueous electrolyte.

Sodium metal hexacyanoferrates Na 2 M[Fe(CN) 6 ], M = Ni, Cu, Fe, Co, Mn M Mn (in Non-aq.) Co (in Aq.) Fe (in Aq.) E [V] vs. Ag/AgCl E [V] vs. Ag/AgCl After Song [18] After Wu [16] After Wu [17] E [V] vs. Na/Na + 1.0 1.0 4.0 O 2 ↑ 0.5 0.5 3.5 3.0 0.0 0.0 0 0 100 50 0 50 150 100 50 100 150 Capacity [mAh/g] Capacity [mAh/g] Capacity [mAh/g] After Song [18] After Wu [17] After Wu [16] Morph. Round particle Cubic Cubic Property with defects without defects without defects Na 2 Mn[Fe(CN) 6 ] is attractive because of 2 redox-active sites. However, the round particles with defects may dissolve and cannot suppress water decomposition in diluted electrolyte. → Other methods should be considered as suppressing dissolution and water decomposition.

Electrolyte selection for aqueous sodium-ion battery Cation Approx. saturated Weak points Ref. concentration [mol/kg] Li + Na + Cl - 18 6 Anodic oxidation & gas evolution - OH - 5 32 Prussian blue decomposition in alkali 19 NO 3 - 13 10 Ti based NASICON corrosion 11 SO 4 2- 3 2 Low solubility - Anion N(SO 2 CF 3 ) 2 - 21 9 High cost TFSI - 6 SO 2 CF 3 - 22 9 High cost OTf - 7 N(SO 2 C 2 F 5 ) 2 - ND ND High cost BETI - 8 17 ClO 4 - 6 17 Explosive - Highly concentrated NaClO 4 aqueous electrolyte will suppress dissolution or side reaction and support high voltage operation. Cathode Electrolyte Anode Na 2 Mn[Fe(CN) 6 ] NaTi 2 (PO 4 ) 3 17 mol/kg NaClO 4 aq. (NMHCF) (NTP) [6] L. Suo, et al. , Science , 350 (2015) 938. [7] L. Suo, et al. , Angew. Chemie. , 85287 (2016) 7136. [8] Y. Yamada, et al. , Nat. Energy , 1 (2016) 16129. [11] W. Wu, et al ., J. Electrochem. Soc., 162 (2015) A803. [19] R. Koncki, et al. , Anal. Chem. , 70 (1998) 2544.

Experiment

Synthesis of Na x Mn[Fe(CN) 6 ] y ・ zH 2 O Conventional co-precipitation method [18] Na 4 [Fe(CN) 6 ] aq. NaCl aq. Stir (in H 2 O + EtOH) @ RT MnCl 2 aq. Filter & Wash (H 2 O + EtOH) Light green precipitation Vacuum dry @100 ℃ (over night) Green blue Na x Mn[Fe(CN) 6 ] y ・ zH 2 O Green blue Na x Mn[Fe(CN) 6 ] y ・ zH 2 O [18] J. Song, et al., J. Am. Chem. Soc ., 137 (2015) 2658.

Morphological & structural properties of NMHCF XRD SEM As-prepared NMHCF Intensity/a. u. [20] 200 nm Na 2 MnFe(CN) 6 By ICP-AES & TGA Pm-3m Cubic (100) ICSD #75-4637 (110) (200) Na Mn Fe H 2 O (210) (300) (310) (211) (220) 1.24 1 0.81 1.28 10 20 30 40 50 60 Na 1.24 Mn[Fe(CN) 6 ] 0.81 · 1.28H 2 O 2 θ / degree NMHCF powder was identified as cubic with Pm-3m diffraction pattern consistent with Na 2 Mn[Fe(CN) 6 ]. Approx. 200 nm sized round particles not nano-cubes were observed. [20] Y. Morimoto, et al., Energies , 8 (2015) 9486.

Electrochemical cell (AB : Acetylene black, PTFE ： Polytetrafluoroethylene) Working electrode Electrolyte Reference electrode Counter electrode (WE) (EL) (RE) (CE) Na 2 Mn[Fe(CN) 6 ] ： AB ： PTFE 1 or 17 mol/kg Silver-silver chloride NaTi 2 (PO 4 ) 3 ： AB ： PTFE ＝ 70 ： 25 ： 5 (wt%) NaClO 4 aq. (Ag/AgCl) in sat. KCl aq. ＝ 70 ： 25 ： 5 (wt%) RE WE CE Ti mesh Ti mesh WE pellet CE pellet (~ 2 mg) (~ 3 mg) Prussian blue analogues [21] NASICON-type Na 2 Mn[Fe(CN) 6 ] NMHCF NaTi 2 (PO 4 ) 3 NTP EL Sodium manganese hexacyanoferrate Sodium titanium phosphate Beaker-type cell Na 2 MnFe(CN) 6 //NaTi 2 (PO 4 ) 3 Ion-type cell Na 2 Mn[Fe(CN) 6 ] + NaTi 2 (PO 4 ) 3 ⇄ Mn[Fe(CN) 6 ] + Na 3 Ti 2 (PO 4 ) 3 [21] T. Tojo, et al., Electrochem. Acta , 207 (2016) 22.

Result & discussion

Cyclic voltammetry on Ti current collector & active materials Voltage/V vs. Na/Na + 1 2 3 4 1 2 3 4 0.5 0.5 1 mol/kg NaClO 4 17 mol/kg NaClO 4 aq. aq. Practical Practical O 2 Current/mA 2.7 V 1.9 V O 2 ↑ ↑ 0.0 0.0 H 2 H 2 ↑ ↑ Theoretical Theoretical 1.23 V pH = 7 1.23 V pH = 6 -0.5 -0.5 1 mol/kg NaClO 4 17 mol/kg NaClO 4 aq. 2 2 aq. Current density/A g -1 NMHCF O 2 1 NMHCF 1 ↑ 0 0 H 2 ↑ -1 -1 NTP NTP -2 -2 -2 -1 0 1 2 -2 -1 0 1 2 Voltage/V vs. Ag/AgCl 1 & 17 mol/kg NaClO 4 aqueous electrolyte had 1.9 V & 2.7 V practical stability windows, respectively. The windows were larger than 1.23 V theoretical stability window of water.