Supporting Information Phase Evolution of Tin Nanocrystals in Lithium ...
Supporting Information
Phase Evolution of Tin Nanocrystals in Lithium Ion Batteries Hyung Soon Im, Yong Jae Cho, Young Rok Lim, Chan Su Jung, Dong Myung Jang, Jeunghee Park,* Fazel Shojaei, and Hong Seok Kang*
Figure S1. XRD patterns of Sn, SnS, and SnO2 NCs. The peaks of the Sn, SnS, o-SnO2, and t-SnO2 NCs matched those of tetragonal-phase Sn (JCPDS No. 86-2265; a = 5.831 Å, c = 3.181 Å), orthorhombic-phase SnS (JCPDS No. 39-0354; a = 4.329 Å, b = 11.19 Å; c = 3.983 Å), orthorhombic-phase SnO2 (JCPDS No. 78-1063; a = 4.737 Å, b = 5.708 Å, c = 15.865 Å), and tetragonal-phase SnO2 (JCPDS No. 77-0452; a = 4.755 Å, c = 3.199 Å),
(101) (022)
30
(130)
(025)
(042)
(112) (151) (122)
Sn (301)
(211)
(220)
40
(211)
SnS (210) (141) (002)
(040) (111) (101)
(101)
(023) (200)
Orthorhombic SnO2
(131)
(112)
(200)
(120) (021)
(110)
(111)
(113)
Intensity (arb. units) 20
(002)
(211) (220)
Tetragonal SnO2 (200) (111)
(110)
respectively.
50
60
2θ (Degree)
S1
Figure S2. EDX shows for the (a) Sn, (b) SnS, and (c) SnO2 NCs.
Figure S3. Charge and discharge voltage profiles of coin-type half cells using (a) Sn, (b) SnS, and (c) SnO2 NCs for 1, 2, 5, 10, 30, and 70 cycles tested between 0.01 and 1.2 V at a rate of 100 mA/g (=1/10 C).
(a) The first discharge and charge capacities of Sn were 1580 and 880 mAh/g, respectively, with an initial coulombic efficiency of 56 %. After the first cycle, a complete reversibility of capacity was observed with an average coulombic efficiency of 98 % for 70 cycles. A plateau region appears at approximately 0.3 V for all cycles, corresponding to the reversible process of Li insertion/desertion of Sn (Sn + xLi ↔ LixSn).
S2
(b) The first discharge and charge capacities of SnS were 1620 and 965 mAh/g, respectively, with an initial coulombic efficiency of 60 %. A plateau at ~1.2 V in the first discharge process is ascribed to the irreversible decomposition of SnS into Sn and Li2S; Sn + 2Li → Sn + Li2S. A plateau region at approximately 0.2 V corresponds to the reversible process of Sn + xLi ↔ LixSn.
(c) The first discharge and charge capacities of SnO2 were 1260 and 585 mAh/g, respectively, with an initial coulombic efficiency of 46 %. The first dischage curve shows a plateau at ~0.8 V, which is ascribed to the irreversible decomposition of SnO2 into Sn and Li2O; SnO2 + 4Li → Sn + 2Li2O. All discharge curves show a plateau region at approximately 0.2 V for all cycles, respectively, corresponding to the reversible process of Sn + xLi → LixSn.
Figure S4. CV curve for (a) Sn, (b) SnS, and (d) SnO2 NC electrodes at a scan rate of 0.1 mVs-1 over the voltage range 0.01 to 2.5 V for 20 cycles.
(a)
Sn has a reduction (cathodic) current peak at a potential of ~0.3 V and two oxidation
(anodic) current peaks at 0.5 and 0.65 V, probably due to the overpotential resulting from the constant current or non-equilibrium states. The averaging gives 0.3 V and 0.57 V, which is ascribed to the alloying (cathodic scan)/dealloying (anodic scan) of Li with Sn, respectively; Sn + xLi ↔ LixSn. S3
(b) SnS exhibits a cathodic peak at 1.1 V in the first potential sweeping, and the peak disappears in the second sweeping. The peak was assigned it to the decomposition of SnS into Sn and Li2S. The cathodic peak shifted to the higher voltage region with a reduced intensity in the subsequent sweeping. We tentatively assigned it to the irreversible formation of LixSnS (SnS + xLi → LixSnS) and/or its decomposition into Sn and Li2S: LixSnS + (2x)Li → Sn + Li2S. The signature of the alloying (cathodic scan)/dealloying (anodic scan) of Li from Sn (Sn + xLi ↔ LixSn) appears as a pair of redox peaks at potentials of around 0.3 V and 0.55 V, respectively, consistently with the case of Sn. (c) SnO2 shows a cathodic peak at 0.7 V in the first potential sweeping, which is assigned to the decomposition into Sn and Li2O: SnO2 + 4Li → Sn + 2Li2O. Similarly to the case of SnS, the cathodic peak shifted to the higher voltage region with a reduced intensity in the subsequent sweeping. It was tentatively assigned to the irreversible formation of LixSnO2 and/or its decomposition into Sn and Li2O: LixSnO2 + (4-x)Li → Sn + 2Li2O. A pair of redox peaks at 0.3 V and 0.6 V (average value of 0.5 and 0.7 V) is assigned to the reversible alloying/dealloying reaction of Li with Sn. Figure S5. Structure of α-Sn8Li6 projected onto the ab and ac planes.
S4
Phase Evolution of Tin Nanocrystals in Lithium Ion Batteries Hyung Soon Im, Yong Jae Cho, Young Rok Lim, Chan Su Jung, Dong Myung Jang, Jeunghee Park,* Fazel Shojaei, and Hong Seok Kang*
Figure S1. XRD patterns of Sn, SnS, and SnO2 NCs. The peaks of the Sn, SnS, o-SnO2, and t-SnO2 NCs matched those of tetragonal-phase Sn (JCPDS No. 86-2265; a = 5.831 Å, c = 3.181 Å), orthorhombic-phase SnS (JCPDS No. 39-0354; a = 4.329 Å, b = 11.19 Å; c = 3.983 Å), orthorhombic-phase SnO2 (JCPDS No. 78-1063; a = 4.737 Å, b = 5.708 Å, c = 15.865 Å), and tetragonal-phase SnO2 (JCPDS No. 77-0452; a = 4.755 Å, c = 3.199 Å),
(101) (022)
30
(130)
(025)
(042)
(112) (151) (122)
Sn (301)
(211)
(220)
40
(211)
SnS (210) (141) (002)
(040) (111) (101)
(101)
(023) (200)
Orthorhombic SnO2
(131)
(112)
(200)
(120) (021)
(110)
(111)
(113)
Intensity (arb. units) 20
(002)
(211) (220)
Tetragonal SnO2 (200) (111)
(110)
respectively.
50
60
2θ (Degree)
S1
Figure S2. EDX shows for the (a) Sn, (b) SnS, and (c) SnO2 NCs.
Figure S3. Charge and discharge voltage profiles of coin-type half cells using (a) Sn, (b) SnS, and (c) SnO2 NCs for 1, 2, 5, 10, 30, and 70 cycles tested between 0.01 and 1.2 V at a rate of 100 mA/g (=1/10 C).
(a) The first discharge and charge capacities of Sn were 1580 and 880 mAh/g, respectively, with an initial coulombic efficiency of 56 %. After the first cycle, a complete reversibility of capacity was observed with an average coulombic efficiency of 98 % for 70 cycles. A plateau region appears at approximately 0.3 V for all cycles, corresponding to the reversible process of Li insertion/desertion of Sn (Sn + xLi ↔ LixSn).
S2
(b) The first discharge and charge capacities of SnS were 1620 and 965 mAh/g, respectively, with an initial coulombic efficiency of 60 %. A plateau at ~1.2 V in the first discharge process is ascribed to the irreversible decomposition of SnS into Sn and Li2S; Sn + 2Li → Sn + Li2S. A plateau region at approximately 0.2 V corresponds to the reversible process of Sn + xLi ↔ LixSn.
(c) The first discharge and charge capacities of SnO2 were 1260 and 585 mAh/g, respectively, with an initial coulombic efficiency of 46 %. The first dischage curve shows a plateau at ~0.8 V, which is ascribed to the irreversible decomposition of SnO2 into Sn and Li2O; SnO2 + 4Li → Sn + 2Li2O. All discharge curves show a plateau region at approximately 0.2 V for all cycles, respectively, corresponding to the reversible process of Sn + xLi → LixSn.
Figure S4. CV curve for (a) Sn, (b) SnS, and (d) SnO2 NC electrodes at a scan rate of 0.1 mVs-1 over the voltage range 0.01 to 2.5 V for 20 cycles.
(a)
Sn has a reduction (cathodic) current peak at a potential of ~0.3 V and two oxidation
(anodic) current peaks at 0.5 and 0.65 V, probably due to the overpotential resulting from the constant current or non-equilibrium states. The averaging gives 0.3 V and 0.57 V, which is ascribed to the alloying (cathodic scan)/dealloying (anodic scan) of Li with Sn, respectively; Sn + xLi ↔ LixSn. S3
(b) SnS exhibits a cathodic peak at 1.1 V in the first potential sweeping, and the peak disappears in the second sweeping. The peak was assigned it to the decomposition of SnS into Sn and Li2S. The cathodic peak shifted to the higher voltage region with a reduced intensity in the subsequent sweeping. We tentatively assigned it to the irreversible formation of LixSnS (SnS + xLi → LixSnS) and/or its decomposition into Sn and Li2S: LixSnS + (2x)Li → Sn + Li2S. The signature of the alloying (cathodic scan)/dealloying (anodic scan) of Li from Sn (Sn + xLi ↔ LixSn) appears as a pair of redox peaks at potentials of around 0.3 V and 0.55 V, respectively, consistently with the case of Sn. (c) SnO2 shows a cathodic peak at 0.7 V in the first potential sweeping, which is assigned to the decomposition into Sn and Li2O: SnO2 + 4Li → Sn + 2Li2O. Similarly to the case of SnS, the cathodic peak shifted to the higher voltage region with a reduced intensity in the subsequent sweeping. It was tentatively assigned to the irreversible formation of LixSnO2 and/or its decomposition into Sn and Li2O: LixSnO2 + (4-x)Li → Sn + 2Li2O. A pair of redox peaks at 0.3 V and 0.6 V (average value of 0.5 and 0.7 V) is assigned to the reversible alloying/dealloying reaction of Li with Sn. Figure S5. Structure of α-Sn8Li6 projected onto the ab and ac planes.
S4
