Ping Liu - Academia.edu (original) (raw)
Papers by Ping Liu
Solid State Ionics, 2003
Electrochromic (EC) devices fabricated with liquid or polymeric gel electrolyte are often less du... more Electrochromic (EC) devices fabricated with liquid or polymeric gel electrolyte are often less durable than those constructed with inorganic solid-state electrolyte. Long-term degradation of the ion insertion layer (with extensive cycling) by the liquid/gel electrolyte may contribute to this durability problem. In this respect, two V 2 O 5 thin film electrodes were fabricated for extensive cyclic durability testing in a LiClO 4 /propylene carbonate (PC) liquid electrolyte: One V 2 O 5 film had no overlying coating while the other had a protective thin film of solid lithium ion-conducting LiAlF 4. The protected V 2 O 5 exhibited improved durability in terms of constant capacity with repeated cycling up to 800 cycles, while the uncoated V 2 O 5 electrode displayed significant capacity loss. Our results demonstrate that deposition of an inorganic solid electrolyte (LiAlF 4) on amorphous V 2 O 5 films serves as a protective overlayer and enhances the long-term cycling efficiency and stability of the V 2 O 5 in a liquid electrolyte.
Solid State Ionics, 2003
We report on the electrochromic behavior of amorphous ruthenium oxide thin films and their electr... more We report on the electrochromic behavior of amorphous ruthenium oxide thin films and their electrochemical characteristics for use as counterelectrodes for electrochromic devices. Hydrous ruthenium oxide thin films were prepared by cyclic voltammetry on ITO coated glass substrates from an aqueous ruthenium chloride solution. The cyclic voltammograms of this material show the capacitive behavior including two redox reaction peaks in each cathodic and anodic scan. The ruthenium oxide thin film electrode exhibits a 50% modulation of optical transmittance at 670 nm wavelength with capacitor charge/ discharge.
Journal of Power Sources, 2011
Combustion synthesized Li(Ni 1/3 Mn 1/3 Co 1/3)O 2 particles are coated with thin, conformal laye... more Combustion synthesized Li(Ni 1/3 Mn 1/3 Co 1/3)O 2 particles are coated with thin, conformal layers of Al 2 O 3 by atomic layer deposition (ALD). XRD, Raman, and FTIR are used to confirm that no change to the bulk, local structure occurs after coating. Electrochemical impedance spectroscopy (EIS) results indicate that the surface of the Li(Ni 1/3 Mn 1/3 Co 1/3)O 2 are protected from dissolution and HF attack after only 4-layers, or ∼8.8Å of alumina. Electrochemical performance at an upper cutoff of 4.5 V is greatly enhanced after the growth of Al 2 O 3 surface film. Capacity retention is increased from 65% to 91% after 100 cycles at a rate of C/2 with the addition of only two atomic layers. Due to the conformal coating, the effects on Li(Ni 1/3 Mn 1/3 Co 1/3)O 2 overpotential and capacity are negligible below six ALD-layers. We propose that the use of ALD for coating on Li(Ni 1/3 Mn 1/3 Co 1/3)O 2 particles makes the material a stronger replacement candidate for LiCoO 2 as a positive electrode in lithium ion batteries.
Journal of Applied Physics, 2000
The gasochromic mechanism in amorphous tungsten oxide films has been investigated using Raman sca... more The gasochromic mechanism in amorphous tungsten oxide films has been investigated using Raman scattering measurements. The Raman spectra of as-deposited films show two strong peaks at 770 and 950 cm Ϫ1 due to vibrations of the O-W 6ϩ-O and W 6ϩ ϭO bonds, respectively. When the Pd/a-WO 3 films are gasochromically colored by exposure to diluted hydrogen gas, extra Raman peaks due to O-W 5ϩ-O and W 5ϩ ϭO bonds appear at 330 and 450 cm Ϫ1 , respectively. The Raman spectra of a-WO 3 films bleached with isotopic heavy oxygen (18 O) show that the gasochromic coloration in a-WO 3 films is directly related to the double injection of hydrogen ions and electrons.
Journal of Applied Physics, 2002
Microstructural changes of amorphous V 2 O 5 films with lithium intercalation are studied using R... more Microstructural changes of amorphous V 2 O 5 films with lithium intercalation are studied using Raman-scattering measurements. The Raman spectra of as-deposited films show two broad peaks around at 520 and 650 cm Ϫ1 , due to the stretching modes of the V 3-O and V 2-O bonds, respectively, and a relatively sharp peak at 1027 cm Ϫ1 due to the V 5ϩ vO stretching mode of terminal oxygen atoms. In addition, there is a peak at 932 cm Ϫ1 that we attribute to the V 4ϩ vO bonds. Comparison of the Raman spectra of V 2 O 5 films with different oxygen deficiencies confirms this assignment. This Raman peak due to the stretching mode of the V 4ϩ vO bonds develops and shifts toward lower frequencies with increasing lithium concentration. Comparison to results from gasochromic hydrogen insertion indicates that the 932 cm Ϫ1 Raman peak is not a result of vibrations which involve Li or H atoms. We propose that the V 4ϩ vO bonds are created by two different mechanisms: a direct conversion from V 5ϩ vO bonds and the breaking of the single oxygen bonds involving V 4ϩ ions.
Electrochemical and Solid-State Letters, 2003
Amorphous hydrous ruthenium oxide thin films have been investigated and demonstrated to be an exc... more Amorphous hydrous ruthenium oxide thin films have been investigated and demonstrated to be an excellent optical modulating material as well as an electrochemical supercapacitor. The a-RuO 2 •xH 2 O films have been prepared by cyclic voltammetry on ITO-coated glass substrates from an aqueous ruthenium chloride solution. The cyclic voltammograms of this material show proof of capacitive behavior including two redox reaction peaks in each cathodic and anodic scan. The as-deposited a-RuO 2 •xH 2 O films exhibit an optical density change of 0.3 at 670 nm wavelength with capacitor charge/discharge in an anodic coloring fashion. This paper describes our electrochemical and electro-optical characterization results and analyses.
MRS Energy & Sustainability, 2015
ABSTRACTA variety of inherently robust energy storage technologies hold the promise to increase t... more ABSTRACTA variety of inherently robust energy storage technologies hold the promise to increase the range and decrease the cost of electric vehicles (EVs). These technologies help diversify approaches to EV energy storage, complementing current focus on high specific energy lithium-ion batteries.The need for emission-free transportation and a decrease in reliance on imported oil has prompted the development of EVs. To reach mass adoption, a significant reduction in cost and an increase in range are needed. Using the cost per mile of range as the metric, we analyzed the various factors that contribute to the cost and weight of EV energy storage systems. Our analysis points to two primary approaches for minimizing cost. The first approach, of developing redox couples that offer higher specific energy than state-of-the-art lithium-ion batteries, dominates current research effort, and its challenges and potentials are briefly discussed. The second approach represents a new insight into ...
![Research paper thumbnail of Lithium Thin-Film Battery with a Reversed Structural Configuration SS/Li/Lipon/Li[sub x]V[sub 2]O[sub 5]/Cu](https://a.academia-assets.com/images/blank-paper.jpg)
](Electrochemical and Solid-State Letters, 2003
... S.-H. Lee, P. Liu, CE Tracy, and DK Benson, All-Solid-State Rocking Chair Lithium Battery on... more ... S.-H. Lee, P. Liu, CE Tracy, and DK Benson, All-Solid-State Rocking Chair Lithium Battery on a Flexible Al Substrate, Electrochem. Solid-State Lett., 2, 425 (1999). X.-H. Yu, JB Bates, GE Jellison, and FX Hart, A Stable Thin-Film Lithium Electrolyte: Lithium Phosphorus ...
Electrochemical and Solid-State Letters, 2004
The electrochemical performance of single wall carbon nanotube ͑SWNT͒/Nafion composite electrodes... more The electrochemical performance of single wall carbon nanotube ͑SWNT͒/Nafion composite electrodes were studied in sulfuric acid solutions. Electrochemical oxidation of the highly dispersed SWNTs within the Nafion matrix results in a dramatic morphological change in the SWNTs. As evidenced by transmission electron microscopy, small bundles of straight-line SWNTs change into curved bundles with relatively sharp contours. Electrochemical impedance spectroscopy indicates increased electrochemical impedance in the oxidized SWNT/Nafion composites. Reduction of the composites at low potentials reverses impedance to near original values. However, the morphological change of the SWNTs is irreversible. In addition, the electrochemical capacitance of the composite electrode increases significantly after the oxidation-reduction cycle. Our results demonstrate that electrochemical oxidation and reduction treatment of the composite is also potentially useful for modifying the SWNT sidewalls, which results in an enhancement of the electrochemical capacitance of SWNTs.
Solid State Ionics, 2003
Electrochromic (EC) devices fabricated with liquid or polymeric gel electrolyte are often less du... more Electrochromic (EC) devices fabricated with liquid or polymeric gel electrolyte are often less durable than those constructed with inorganic solid-state electrolyte. Long-term degradation of the ion insertion layer (with extensive cycling) by the liquid/gel electrolyte may contribute to this durability problem. In this respect, two V 2 O 5 thin film electrodes were fabricated for extensive cyclic durability testing in a LiClO 4 /propylene carbonate (PC) liquid electrolyte: One V 2 O 5 film had no overlying coating while the other had a protective thin film of solid lithium ion-conducting LiAlF 4. The protected V 2 O 5 exhibited improved durability in terms of constant capacity with repeated cycling up to 800 cycles, while the uncoated V 2 O 5 electrode displayed significant capacity loss. Our results demonstrate that deposition of an inorganic solid electrolyte (LiAlF 4) on amorphous V 2 O 5 films serves as a protective overlayer and enhances the long-term cycling efficiency and stability of the V 2 O 5 in a liquid electrolyte.
Solid State Ionics, 2003
We report on the electrochromic behavior of amorphous ruthenium oxide thin films and their electr... more We report on the electrochromic behavior of amorphous ruthenium oxide thin films and their electrochemical characteristics for use as counterelectrodes for electrochromic devices. Hydrous ruthenium oxide thin films were prepared by cyclic voltammetry on ITO coated glass substrates from an aqueous ruthenium chloride solution. The cyclic voltammograms of this material show the capacitive behavior including two redox reaction peaks in each cathodic and anodic scan. The ruthenium oxide thin film electrode exhibits a 50% modulation of optical transmittance at 670 nm wavelength with capacitor charge/ discharge.
Journal of Power Sources, 2011
Combustion synthesized Li(Ni 1/3 Mn 1/3 Co 1/3)O 2 particles are coated with thin, conformal laye... more Combustion synthesized Li(Ni 1/3 Mn 1/3 Co 1/3)O 2 particles are coated with thin, conformal layers of Al 2 O 3 by atomic layer deposition (ALD). XRD, Raman, and FTIR are used to confirm that no change to the bulk, local structure occurs after coating. Electrochemical impedance spectroscopy (EIS) results indicate that the surface of the Li(Ni 1/3 Mn 1/3 Co 1/3)O 2 are protected from dissolution and HF attack after only 4-layers, or ∼8.8Å of alumina. Electrochemical performance at an upper cutoff of 4.5 V is greatly enhanced after the growth of Al 2 O 3 surface film. Capacity retention is increased from 65% to 91% after 100 cycles at a rate of C/2 with the addition of only two atomic layers. Due to the conformal coating, the effects on Li(Ni 1/3 Mn 1/3 Co 1/3)O 2 overpotential and capacity are negligible below six ALD-layers. We propose that the use of ALD for coating on Li(Ni 1/3 Mn 1/3 Co 1/3)O 2 particles makes the material a stronger replacement candidate for LiCoO 2 as a positive electrode in lithium ion batteries.
Journal of Applied Physics, 2000
The gasochromic mechanism in amorphous tungsten oxide films has been investigated using Raman sca... more The gasochromic mechanism in amorphous tungsten oxide films has been investigated using Raman scattering measurements. The Raman spectra of as-deposited films show two strong peaks at 770 and 950 cm Ϫ1 due to vibrations of the O-W 6ϩ-O and W 6ϩ ϭO bonds, respectively. When the Pd/a-WO 3 films are gasochromically colored by exposure to diluted hydrogen gas, extra Raman peaks due to O-W 5ϩ-O and W 5ϩ ϭO bonds appear at 330 and 450 cm Ϫ1 , respectively. The Raman spectra of a-WO 3 films bleached with isotopic heavy oxygen (18 O) show that the gasochromic coloration in a-WO 3 films is directly related to the double injection of hydrogen ions and electrons.
Journal of Applied Physics, 2002
Microstructural changes of amorphous V 2 O 5 films with lithium intercalation are studied using R... more Microstructural changes of amorphous V 2 O 5 films with lithium intercalation are studied using Raman-scattering measurements. The Raman spectra of as-deposited films show two broad peaks around at 520 and 650 cm Ϫ1 , due to the stretching modes of the V 3-O and V 2-O bonds, respectively, and a relatively sharp peak at 1027 cm Ϫ1 due to the V 5ϩ vO stretching mode of terminal oxygen atoms. In addition, there is a peak at 932 cm Ϫ1 that we attribute to the V 4ϩ vO bonds. Comparison of the Raman spectra of V 2 O 5 films with different oxygen deficiencies confirms this assignment. This Raman peak due to the stretching mode of the V 4ϩ vO bonds develops and shifts toward lower frequencies with increasing lithium concentration. Comparison to results from gasochromic hydrogen insertion indicates that the 932 cm Ϫ1 Raman peak is not a result of vibrations which involve Li or H atoms. We propose that the V 4ϩ vO bonds are created by two different mechanisms: a direct conversion from V 5ϩ vO bonds and the breaking of the single oxygen bonds involving V 4ϩ ions.
Electrochemical and Solid-State Letters, 2003
Amorphous hydrous ruthenium oxide thin films have been investigated and demonstrated to be an exc... more Amorphous hydrous ruthenium oxide thin films have been investigated and demonstrated to be an excellent optical modulating material as well as an electrochemical supercapacitor. The a-RuO 2 •xH 2 O films have been prepared by cyclic voltammetry on ITO-coated glass substrates from an aqueous ruthenium chloride solution. The cyclic voltammograms of this material show proof of capacitive behavior including two redox reaction peaks in each cathodic and anodic scan. The as-deposited a-RuO 2 •xH 2 O films exhibit an optical density change of 0.3 at 670 nm wavelength with capacitor charge/discharge in an anodic coloring fashion. This paper describes our electrochemical and electro-optical characterization results and analyses.
MRS Energy & Sustainability, 2015
ABSTRACTA variety of inherently robust energy storage technologies hold the promise to increase t... more ABSTRACTA variety of inherently robust energy storage technologies hold the promise to increase the range and decrease the cost of electric vehicles (EVs). These technologies help diversify approaches to EV energy storage, complementing current focus on high specific energy lithium-ion batteries.The need for emission-free transportation and a decrease in reliance on imported oil has prompted the development of EVs. To reach mass adoption, a significant reduction in cost and an increase in range are needed. Using the cost per mile of range as the metric, we analyzed the various factors that contribute to the cost and weight of EV energy storage systems. Our analysis points to two primary approaches for minimizing cost. The first approach, of developing redox couples that offer higher specific energy than state-of-the-art lithium-ion batteries, dominates current research effort, and its challenges and potentials are briefly discussed. The second approach represents a new insight into ...
Electrochemical and Solid-State Letters, 2003
... S.-H. Lee, P. Liu, CE Tracy, and DK Benson, All-Solid-State Rocking Chair Lithium Battery on... more ... S.-H. Lee, P. Liu, CE Tracy, and DK Benson, All-Solid-State Rocking Chair Lithium Battery on a Flexible Al Substrate, Electrochem. Solid-State Lett., 2, 425 (1999). X.-H. Yu, JB Bates, GE Jellison, and FX Hart, A Stable Thin-Film Lithium Electrolyte: Lithium Phosphorus ...
Electrochemical and Solid-State Letters, 2004
The electrochemical performance of single wall carbon nanotube ͑SWNT͒/Nafion composite electrodes... more The electrochemical performance of single wall carbon nanotube ͑SWNT͒/Nafion composite electrodes were studied in sulfuric acid solutions. Electrochemical oxidation of the highly dispersed SWNTs within the Nafion matrix results in a dramatic morphological change in the SWNTs. As evidenced by transmission electron microscopy, small bundles of straight-line SWNTs change into curved bundles with relatively sharp contours. Electrochemical impedance spectroscopy indicates increased electrochemical impedance in the oxidized SWNT/Nafion composites. Reduction of the composites at low potentials reverses impedance to near original values. However, the morphological change of the SWNTs is irreversible. In addition, the electrochemical capacitance of the composite electrode increases significantly after the oxidation-reduction cycle. Our results demonstrate that electrochemical oxidation and reduction treatment of the composite is also potentially useful for modifying the SWNT sidewalls, which results in an enhancement of the electrochemical capacitance of SWNTs.