Ionic Liquid Electrolytes in Mg-Air Batteries

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1 Ionic Liquid Electrolytes in Mg-Air Batteries A dissertation by Yajing Yan BE (Materials) (Hons.) Submitted in fulfilment of the requirements for the degree of Doctor of Philosophy Institute for Frontier Materials Deakin University January, 2016

2 I Ionic Liquid Electrolytes in MgAir Batteries... Signed:..... Date:...25/01/

3 .... Signed:......

5 Yafei, Rossie, Fangfang, Matzi, and Rob. The list is too long, so don t be mad at me if I forgot tell me to be honest and kind, and I ll always remember that. Also, than

6 ᵒ

7 reasonably high current density (1 ma cm

8 (50 μa cm lower than that of the three electrode half cell test (1 ma cm EG/IL electrolyte can support stable Mg discharge at 0.5 ma cm

9 at 7.5 μa cm the cell could perform at relatively stable potentials was 0.2 ma cm off voltage was about 6.4 mah cm

10 ] Cl Mg(OH) OH)Cl] 4

11 0.2 ma cm

14 air battery at 0.2 ma cm

15 . invention of the first wet cell battery that produced a reliable and steady current of

18 =

19 = =0.40 ( 2.38) =2.78

20 maximum current per unit electrode surface area, expressed in ma cm or A cm conditions during operation. In the first place, not all of the G can be conve

24 metalair batteries

26 at the same time. Compared with lithium, zinc and magnesium don t show any advantages

30 anode surface and improve the current distribution, were studied by McBreen s group.

35 ctions at high current densities (180 or 300 ma cm density up to 94.5 mw cm

37 issues owing to the ether s volatility and also its low ionic conductivity make it a poor choice electrochemical window of over 2.5 V. Subsequently, Aurbach s group achieved a higher lectrolyte. Morita s group has reported reversible

42 e studies date back to Yamamoto s finding of powdery Zn deposits from

44 was stable at a high current density of 1 ma cm discharge at 0.2 ma cm

51 A. Lewandowski, A. Świderska

54 at 1 ma cm μa cm, which fell far short of the impressive current density of 1 ma cm

59 ed properties for a good interphase and the nature of a bad interphase can be established.

62 ᵒ

63 was α carbon paper, α ᵒ

64 ᵒ ᵒ

69 ᵒ = =

70 ᵒ

73 XPS measurements. A Kratos Nova imaging XPS spectrometer with an Al Kα ᵒ

76 ᵒ barely support Mg discharge; even at 1 μa cm 10 μa cm 10 h with little decay. The charge delivered at 72 mol% was 120 μah cm densities. For instance, the discharge potential of the neat IL at 1 μa cm more negative than that of the 72 mol% toluene/il electrolyte at 10 μa cm

77 ᵒ ᵒ mol%, the mixed electrolyte has a viscosity of ca. 82 mpa s, which is almost comparable to some conventional solvents such as tetraglyme (58.3 mpa s). This is expected since diluents

78 ᵒ (mpa s) capability of the electrolyte was 6 μa cm μa cm over a 12 h period. At 20 μa cm at 20 μa cm in the figure at 30 μa cm occurs when an even higher current density at 40 μa cm lity at 72 mol% is between 20 μa cm 30 μa cm

79 ᵒ more THF was added into the ionic liquid, along with the increase of the electrolyte s ionic

80 ᵒ (mpa s) μa cm μa cm at a discharge current of 0.1 ma cm d also support discharge at 0.5 ma cm mah cm

81 μa cm ma cm ma cm ᵒ (mpa s)

82 ᵒ

85 ᵒ μa cm

86 μa cm μa cm

87 μa cm μa cm μa cm μah cm μa cm μa cm

88 0 μa cm discharge rate was increased to 50 μa cm

89 of additives on the nature of the Mg interphase were investigated. Three glyme family members ᵒ

90 diluted IL on the anode side at current densities from 30 to 50 μa cm diluted IL electrolyte systems. At 30 μa cm

91 density was increased to 50 μa cm at a rate higher than 30 μa cm μa cm about 270 mv. When the current density was increased to 40 μa cm discharge rate was further stepped up to 80 μa cm 3.6 mah cm

92 at 20 μa cm μa cm was decreased back to 50 μa cm delivered was around 4.5 mah cm than 4.5 mah cm μa cm

94 rest of the 12 h. At the end of the discharge at 30 μa cm

97 such a long period at 50 μa cm capabilities than triglyme. The Mg interphase during discharge at 30 μa cm long term stable discharge at 50 μa cm

98 support Mg discharge at 500 μa cm μa cm at 200 μa cm before a charge of 1600 μah cm for another 8 h delivering charge of 1600 μah cm at 200 μa cm

100 ace after discharge at 200 μa cm of time at 0.2 ma cm

101 = = = 3.73 = 90.64

102 μa cm during discharge at 200 μa cm at 200 μa cm

103

104 port Mg discharge at 40 μa cm a stable Mg discharge at 500 μa cm d still only support the Mg discharge at a current density no higher than 20 μa cm

105 increased to 50 μa cm discharge at 30 μa cm μa cm up to between 40 and 50 μa cm μa cm degree after 8 h discharge at 200 μa cm

106

107 discharge at 200 μa cm h when an α Ah cm (with a discharge capacity less than 500 μah cm at 100 μa cm

108 oxygen battery at 50 and 100 μa cm capacity at current densities of 50 and 100 μa cm the discharge test. At 50 μa cm 24.4 h, resulting in a discharge capacity of 1.22 mah cm

109 μa cm quickly reached 1 V in 4 h, leading to a small capacity of less than 0.4 mah cm oxygen cell is smaller than 100 μa cm surprising since a stable Mg discharge at 500 μa cm Air battery at 50 and 125 μa cm air cell at 50 and 125 μa cm discharge are presented in this figure, it is clear that even at 125 μa cm was sustained over a discharge capacity of ca μah cm dropping. A total discharge capacity of ca μah cm the experiment was stopped at 116 h and a capacity of 5800 μah cm Therefore the discharge capacity in this case must be larger than 5800 μah cm

110 00 μah cm at 100 μa cm densities of 7.5, 10, 25, 50 and 125 μa cm and 125 μa cm μa cm μa cm

111 Ah cm μa cm μa cm μa cm Ah cm Ah cm μa cm μa cm 200 μa cm

112 Ah cm

113 Air cell at 200 μa cm the ambient air over the discharge at 200 μa cm air cell at 200 μa cm At 200 μa cm Ah cm

114

115 Figure 5.5 compares the discharge behaviour at 50 μa cm air battery using glass fibre filter paper separator at 50 μa cm polypropylene separator at 50 μa cm

116 was at rest for 24 h and then discharged at 200 μa cm at 200 μa cm μa cm air full cell at 200 μa cm

117 air batteries at 200 μa cm without the α Ah cm air cell using α carbon paper as cathode at 200 μa cm discharge behaviour at 200 μa cm When α Ah cm

118 that the α

119 A cm cell could sustain was 100 μa cm μa cm 100 μa cm 125 μa cm carbon paper cathode at 200 μa cm A cm

120 ... =109.2 μa cm (2.65 mah cm ) at 100 μa cm at about 1 mah cm +

121

122 μa cm arge stability at 200 μa cm αair cell at 200 μa cm

123

124 at 0.5 ma cm

125 images of a Mg electrode a) after 8 h discharge at 0.5 ma cm ion 2.5x; b) after 8 h discharge at 0.5 ma cm 0.5 ma cm

126 SEM images of a Mg electrode after 8 h discharge at 0.5 ma cm SEM image of the Mg electrode surface after an 8 h discharge at 0.5 ma cm

127

128 and magnesium surface after 24 h discharge at 0.2 ma cm

129

130

131 FTIR spectra of the Mg surface after 24 h discharge at 0.2 ma cm the Mg surface after 24 h discharge at 50 μa cm

132

133 after 24 h discharge at 50 μa cm

134 oxygen full cell after 24 h discharge at 50 μa cm

135

136

137

138 and Mg electrode after an 8 h discharge at 0.5 ma cm

139 XPS spectra of the Mg electrode after 8 h discharge at 0.5 ma cm

140

141

142

143

144 ᵒ ᵒ ᵒ ᵒ ᵒᵒ h discharge at 50 μa cm

145 μa cm arged at 50 μa cm

146 Mg (OCHOH) Cl 2Mg (OCHOH) Cl 2Mg (OCHOH) 3Cl 3Mg (OCH Cl OH Mg OH) Cl. This assignment is based on the combination of the ion species that Mg electrode after 24 h discharge at 50 μa cm charge at m/z has been identified as (3Mg Cl OH)

147 Mg 3Cl Mg (OCH ] Cl ] 2Cl OH ] 2Cl Mg [P] 2Cl (OCH ] 3Cl (OCHOH) ( OCHOH) OH ] 2Cl As such, these peaks are identified as Mg 3Cl (Mg

148 ] Cl ] 3Cl (OCH

149 at 50 μa cm

150 ] Cl OH)Cl] 4 Mg 3Cl, each of the 9 Mg atoms should coordinate with three chloride ions. The rest of the

151

152 FTIR spectra of Mg anode surface after 24 h discharge at 100 μa cm 50 μa cm cell and 24 h discharge at 200 μa cm

153

154 μa cm at 100 μa cm

155 2Mg 2Cl ] H ] Mg 2Cl OH ] Cl ] Mg 2Cl OH and (2[P] [Cl] to (2Mg 2Cl) Mg OH) Cl. Apart from these,

156 Mg 3Cl Mg 3Cl (OCHOH) OH Mg 3Cl (OCHOH) 2OH Mg 5Cl (OCHOH) OH 2Mg 5Cl (OCHOH) OH Mg [P] 3Cl OH ] 3Cl negative ion mass spectrum were identified as Mg 3Cl (Mg 3Cl (OCHOH) 2OH) (2Mg 5Cl (OCHOH) OH) ] 2Cl. So far, except for Mg 3Cl ] 2Cl

157 assigned to (Mg [P] 3Cl OH)

158

159 electrolyte. The discharged Mg surface was shown to be gel like under the ] Cl Mg(OH) OH)Cl] 4

160

161 discharge at 1 ma cm only 50 μa cm, much lower than 1 ma cm

162 A cm μa cm for toluene and 30 μa cm

163 could support a stable Mg discharge at 0.5 ma cm

164

165

166 pure oxygen with a high rate capability of 0.2 ma cm only 50 μa cm potential of ca V at 0.2 ma cm capacity of 4.9 mah cm with the α increased ca. 30% at 0.2 ma cm lower than 0.2 ma cm With the optimized separator material and α around 32 h at 0.2 ma cm and can deliver a charge of 6.4 mah cm

167 than the 50 μa cm work on α

168

169 ] Cl Mg(OH) OH)Cl] 41H

170

171

172

173

174 =

175 air full cell at 200 μa cm air full cell without catalyst at 200 μa cm air full cell using α200 μa cm

176 air battery at 0.2 ma cm As mentioned in Chapter 5 section 5.1.1, the discharge experiment results at 0.2 ma cm IL electrolyte at 0.2 ma cm

177 cell after 24 h discharge at 50 μa cm oxygen cell after 24 h discharge at 50 μa cm

178 oxygen cell after 24 h discharge at 50 μa cm

179

180

181

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