Supporting Information Nanoscale Porous Lithium Titanate Anode for ...
Supporting Information
Nanoscale Porous Lithium Titanate Anode for Superior High Temperature Performance
Pankaj K Alaboina†, Yeqian Ge‡, Md-Jamal Uddin†, Yang Liu§, Dongsuek Lee¥, Seiung Park¥, Xiangwu Zhang‡, and Sung-Jin Cho†,∗ †
Joint School of Nanoscience and Nanoengineering, North Carolina Agricultural and Technical
State University, Greensboro, NC, 27401, USA ‡
Department of Textile Engineering, Chemistry, and Science, North Carolina State University,
Raleigh, NC, 27695, USA §
Department of Materials Science and Engineering, North Carolina State University, Raleigh,
NC, 27695, USA ¥
Panaxetec Inc., Nonsan-si, Chungchenongnamdo, 320-944, South Korea
Corresponding Author *
E-mail: [email protected]
S1
COMPARISION TESTS FOR SIZE OPTIMIZATION
Moisture Absorption Test. For the water absorption test, 100 grams of LTO powder samples were dried in an oven. After drying, the weight of the samples is measured which are referred to as the dry weights. The samples are then placed in a beaker at room temperature atmosphere for moisture absorption. The weight of the samples is measured at 30 min, 60 min, 90 min, and 120 min to check the levels of moisture absorption at atmosphere, which are the wet weights. Water absorption can be expressed as an increase in weight percent. Percent Water Absorption = [(Wet weight - Dry weight)/ Dry weight] x 100
Table S1. Detailed information about LTO-150, LTO-200, and LTO-CNT. Analysis Primary Particle Size (nm) Additive Secondary Particle Size Distribution (µm)
D1
D50 D90 D100 Brunauer Emmett Teller (BET) surface area (m2 g-1) Tap Density (g cm-3) Processing
LTO-150
LTO-200
LTO-CNT
150
200
150
None
None
5% Carbon nanotubes
2.0
5.0
5.5
7.3 19.9 70.2
11.1 26.3 52.7
11.3 24.5 52.5
5.3
2.7
10.3
1.0 Calcination at 760°C
1.1 Calcination at 850°C
1.0 Mechanically mixed with LTO-150
It should be noted that the water absorption of LTO material is directly proportional to its specific surface area. LTO-200 has a very low surface area (Table S1) and thus moisture absorption is very low compared to LTO-150 and LTO-CNT as illustrated in Figure S1. In LTO-
S2
200, the water content increases till the first 30min and reaches saturation at around 500 ppm. However, LTO-150 and LTO-CNT having higher surface area showed two to five-fold moisture absorption compared to LTO-200 as extended exposure to air.
Figure S1. Moisture absorption test comparison.
Slurry Viscosity Test. The Brookfield Viscometer was used for slurry viscosity test. It investigates the viscosity by measuring the force required to rotate a spindle in the sample slurry which in this case is comprised of LTO: Carbon Black (Super C65): PVDF (Solvay PVDF 5130). The viscosity of LTO slurry is measured by multiplying the reading by a constant related to the particular rotational speed used from 1 to 100 shear rate (spindle rotation speed). Viscosity is a measure of the ratio of shearing stress to rate of shear. Poises= Shear Stress (Dynes)/Rate Shear (cm sec-1)
S3
LTO-200 even with increasing spindle shear rate showed a steady viscosity behavior compared to LTO-150 and LTO-CNT (Figure S2), indicating good dispersion of the nanoparticles in the slurry which determines for a good quality electrodes.
Figure S2. Slurry viscosity measurement test comparison.
Adhesion Strength Test. Good adhesion and good slurry are mutually associated. For the adhesion strength check, a peeling test was performed after the LTO sample slurries were coated and dried on Al foils. The test was performed using a load cell and the peeling forces were measured. The LTO-200 and LTO-CNT exhibit a higher adhesion strength of 39.27 gf (25mm)-1 and 40.95 gf (25mm)-1, respectively. LTO-150 showed a low adhesion strength of 15.12 gf (25mm)-1 as shown in Figure S3.
S4
Figure S3. Adhesion strength test comparison.
S5
Nanoscale Porous Lithium Titanate Anode for Superior High Temperature Performance
Pankaj K Alaboina†, Yeqian Ge‡, Md-Jamal Uddin†, Yang Liu§, Dongsuek Lee¥, Seiung Park¥, Xiangwu Zhang‡, and Sung-Jin Cho†,∗ †
Joint School of Nanoscience and Nanoengineering, North Carolina Agricultural and Technical
State University, Greensboro, NC, 27401, USA ‡
Department of Textile Engineering, Chemistry, and Science, North Carolina State University,
Raleigh, NC, 27695, USA §
Department of Materials Science and Engineering, North Carolina State University, Raleigh,
NC, 27695, USA ¥
Panaxetec Inc., Nonsan-si, Chungchenongnamdo, 320-944, South Korea
Corresponding Author *
E-mail: [email protected]
S1
COMPARISION TESTS FOR SIZE OPTIMIZATION
Moisture Absorption Test. For the water absorption test, 100 grams of LTO powder samples were dried in an oven. After drying, the weight of the samples is measured which are referred to as the dry weights. The samples are then placed in a beaker at room temperature atmosphere for moisture absorption. The weight of the samples is measured at 30 min, 60 min, 90 min, and 120 min to check the levels of moisture absorption at atmosphere, which are the wet weights. Water absorption can be expressed as an increase in weight percent. Percent Water Absorption = [(Wet weight - Dry weight)/ Dry weight] x 100
Table S1. Detailed information about LTO-150, LTO-200, and LTO-CNT. Analysis Primary Particle Size (nm) Additive Secondary Particle Size Distribution (µm)
D1
D50 D90 D100 Brunauer Emmett Teller (BET) surface area (m2 g-1) Tap Density (g cm-3) Processing
LTO-150
LTO-200
LTO-CNT
150
200
150
None
None
5% Carbon nanotubes
2.0
5.0
5.5
7.3 19.9 70.2
11.1 26.3 52.7
11.3 24.5 52.5
5.3
2.7
10.3
1.0 Calcination at 760°C
1.1 Calcination at 850°C
1.0 Mechanically mixed with LTO-150
It should be noted that the water absorption of LTO material is directly proportional to its specific surface area. LTO-200 has a very low surface area (Table S1) and thus moisture absorption is very low compared to LTO-150 and LTO-CNT as illustrated in Figure S1. In LTO-
S2
200, the water content increases till the first 30min and reaches saturation at around 500 ppm. However, LTO-150 and LTO-CNT having higher surface area showed two to five-fold moisture absorption compared to LTO-200 as extended exposure to air.
Figure S1. Moisture absorption test comparison.
Slurry Viscosity Test. The Brookfield Viscometer was used for slurry viscosity test. It investigates the viscosity by measuring the force required to rotate a spindle in the sample slurry which in this case is comprised of LTO: Carbon Black (Super C65): PVDF (Solvay PVDF 5130). The viscosity of LTO slurry is measured by multiplying the reading by a constant related to the particular rotational speed used from 1 to 100 shear rate (spindle rotation speed). Viscosity is a measure of the ratio of shearing stress to rate of shear. Poises= Shear Stress (Dynes)/Rate Shear (cm sec-1)
S3
LTO-200 even with increasing spindle shear rate showed a steady viscosity behavior compared to LTO-150 and LTO-CNT (Figure S2), indicating good dispersion of the nanoparticles in the slurry which determines for a good quality electrodes.
Figure S2. Slurry viscosity measurement test comparison.
Adhesion Strength Test. Good adhesion and good slurry are mutually associated. For the adhesion strength check, a peeling test was performed after the LTO sample slurries were coated and dried on Al foils. The test was performed using a load cell and the peeling forces were measured. The LTO-200 and LTO-CNT exhibit a higher adhesion strength of 39.27 gf (25mm)-1 and 40.95 gf (25mm)-1, respectively. LTO-150 showed a low adhesion strength of 15.12 gf (25mm)-1 as shown in Figure S3.
S4
Figure S3. Adhesion strength test comparison.
S5
