Research statement

Toru Hara, PhD

2014 - 2015

1. Proof of concept on flow-assist-free Zn/NiOOH battery (granted by the World Bank and the Government of the Republic of Kazakhstan)

January 2015 to August 2015

As the inventor, the initiator, and the Co-Principal Investigator.

- Patents = 1 Kazakhstan Patent, 1 PCT, 1 US Patent, 1 Chinese patent, 1 European patent, applied.

- Publications = 1 conference paper.

- Supervision = 1 postdoctoral researcher, 4 MBA candidates, 2 master's degree holders, 2 bachelor's degree holders.

- The uniqueness (novelty) of the flow-assist-free Zn/NiOOH battery is realized in combination: (1) a carbon-based porous current collector such as polyacrylonitrile-based carbon fiber paper or felt having an electrodeposited anode material, zinc, thereon, thereby forming a porous anode; (2) an electropolymerized Zn whisker growth suppressor conformally coated onto the Zn anode; (3) a carbon-based porous current collector such as polyacrylonitrile-based carbon fiber paper or felt having an electrodeposited cathode material, NiOOH, thereon, thereby forming a porous cathode; and (4) a separator and an aqueous (water-based) electrolyte solution such as KOH solution.

Renewable energy integration into electrical grids is crucial for energy security, leading to the highly secured communication network, traffic control, industrial activities, etc. However, renewable energies are intermittent and cannot be directly integrated to electric grids without using batteries. These batteries must be safe and inexpensive from the viewpoint of life-cycle-cost. Aqueous batteries are non-flammable that can be a great merit compared with traditional lithium-ion batteries that use flammable organic electrolyte solutions.

Among various types of aqueous rechargeable batteries, Zn/NiOOH system is a promising candidate: it does not use toxic materials unlike lead-acid batteries; it uses the Zn anode that delivers a higher gravimetric capacity (818 mAh g-1) than metal hydride (e.g., LaNi3.55Co0.75Mn0.4Al0.3, 300 mAh g-1 or less) and a comparable potential (-0.76 V vs. Standard Hydrogen Electrode, SHE) in aqueous media with metal hydride (e.g., LaNi3.55Co0.75Mn0.4Al0.3, -0.75 to -0.85 V vs. SHE). The problem is Zn dendrite formation resulting in internal short circuit failure. NiOOH can deliver 292 - 467 mAh g-1.

In order to suppress Zn dendrite formation, the following strategy has been suggested by Parker et al. [1,2]: (i) facilitating long-range electronic conductivity through the inner core of Zn

electrode, (ii) increasing Zn-electrolyte interfaces to distribute current uniformly throughout the electrode structure, and (iii) forming partially confined void volume elements within the interior of the porous Zn anode that expedite dissolution/deposition. Parker et al. used sintered Zn electrode in order to prepare a porous, monolithic, three-dimensional aperiodic architecture; however, a more ideal architecture can be realized by electroplating Zn onto a three-dimensional porous current collector such as carbon fiber.

Although I did not teach them the following: the more important strategy is, to optimize the relation between void-space volume in above-mentioned three-dimensional current collector and anode/cathode capacity ratio. Dendrite forms, anyway: Li and Zn dissolve into electrolyte solutions and re-deposit. The strategy is, confine dendrite into the void space in three-dimensional electrode. One tactic is, to optimize the relation between void-space volume in above-mentioned three-dimensional current collector and anode/cathode capacity ratio. More detailed explanation can be, to optimize the void-space volume/re-deposit volume ratio.

Replacing Zn to another material will be another project (my personal future plan 1).

References

[1] J. F. Parker, C. N. Chervin, E. S. Nelson, D. R. Rolison, J. W. Long, Energy Environ. Sci. 7 (2014) 1117-1124.

[2] J. F. Parker, E. S. Nelson, M. D. Wattendorf, C. N. Chervin, J. W. Long, D. R. Rolison, ACS Appl. Mater. Interfaces 6 (2014) 19471–19476.

2. Development of innovative nonflammable, low cost, and highly durable rechargeable battery (granted by the Ministry of Education and Science of Kazakhstan)

January 2015 to Present

As the inventor, the initiator, and the Principal Investigator

- Patents = 1 KP applied, 1 PCT applied.

- Publications = 1 oral presentation.

- Supervision: 2 master's degree holders, 2 bachelor's degree holders.

- The uniqueness (novelty) of the battery is realized in combination: (1) a carbon-based porous current collector such as polyacrylonitrile-based carbon fiber paper or felt having an electrodeposited anode material, zinc, thereon, thereby forming a porous anode; (2) an electropolymerized Zn whisker growth suppressor conformally coated onto the Zn anode; (3) a carbon-based porous current collector such as polyacrylonitrile-based carbon fiber paper or felt having an impregnated cathode material, LiFePO4, therein, thereby forming a cathode; and (4) an aqueous (water-based) electrolyte solution including Zn2+ and Li+ ion.

Renewable energy integration into electrical grids is crucial for energy security, leading to the highly secured communication network, traffic control, industrial activities, etc. However,

renewable energies are intermittent and cannot be directly integrated to electric grids without using batteries. These batteries must be safe and inexpensive from the viewpoint of life-cycle-cost. Aqueous batteries are non-flammable that can be a great merit compared with traditional lithium-ion batteries that use flammable organic electrolyte solutions.

Among various types of aqueous rechargeable batteries, Zn/LiFePO4 system is a promising candidate: it does not use toxic materials unlike lead-acid batteries; it uses the Zn anode that delivers a higher gravimetric capacity (818 mAh g-1) than metal hydride (e.g., LaNi3.55Co0.75Mn0.4Al0.3, 300 mAh g-1 or less) and a comparable potential (-0.76 V vs. Standard Hydrogen Electrode, SHE) in aqueous media with metal hydride (e.g., LaNi3.55Co0.75Mn0.4Al0.3, -0.75 to -0.85 V vs. SHE). The problem is Zn dendrite formation resulting in internal short circuit failure. LiFePO4 can theoretically deliver 170 mAh g-1.

In order to suppress Zn dendrite formation, the following strategy has been suggested by Parker et al. [1,2]: (i) facilitating long-range electronic conductivity through the inner core of Zn electrode, (ii) increasing Zn-electrolyte interfaces to distribute current uniformly throughout the electrode structure, and (iii) forming partially confined void volume elements within the interior of the porous Zn anode that expedite dissolution/deposition. Parker et al. used sintered Zn electrode in order to prepare a porous, monolithic, three-dimensional aperiodic architecture; however, a more ideal architecture can be realized by electroplating Zn onto a three-dimensional porous current collector such as carbon fiber.

Although I did not teach them the following: the more important strategy is, to optimize the relation between void-space volume in above-mentioned three-dimensional current collector and anode/cathode capacity ratio. Dendrite forms, anyway: Li and Zn dissolve into electrolyte solutions and re-deposit. The strategy is, confine dendrite into the void space in three-dimensional electrode. One tactic is, to optimize the relation between void-space volume in above-mentioned three-dimensional current collector and anode/cathode capacity ratio. More detailed explanation can be, to optimize the void-space volume/re-deposit volume ratio.

References

[1] J. F. Parker, C. N. Chervin, E. S. Nelson, D. R. Rolison, J. W. Long, Energy Environ. Sci. 7 (2014) 1117-1124.

[2] J. F. Parker, E. S. Nelson, M. D. Wattendorf, C. N. Chervin, J. W. Long, D. R. Rolison, ACS Appl. Mater. Interfaces 6 (2014) 19471–19476.

3. Development of economically feasible three-dimensional lithium/sulfur battery (granted by the Ministry of Education and Science of Kazakhstan).

January 2015 to Present

As the inventor and the initiator.

- Patents = 1 KP applied, 1 PCT applied.

- Supervision = 3 postdoctral researchers, 3 master's degree holders, 4 bachelor's degree holder, 1 student.

- The uniqueness (novelty) of the battery is realized in combination: (1) a metal-based porous current collector such as Ni foam having an electrodeposited anode material, Sn (can be intermetallic), thereon, thereby forming a porous anode; (2) an ultrathin separator conformally coated onto the Sn anode; (3) an impregnated cathode material therein, thereby forming a cathode; and (4) an aprotic electrolyte solution including Li+ ion.

4. Development of innovative lithium metal-free lithium-ion sulfur battery for renewable energy, electric transport and electronics (granted by the World Bank and the Government of the Republic of Kazakhstan)

February 2014 to December 2015.

- Patents: 2 KP applied.

- Publications: 1 paper, 1 conference paper, 1 oral presentation.

- My strategy is as follows: (i) cathode: any sulfur-based cathodes are OK but LiPF6/carbonate-compatible one that is based on pyrolyzed polyacrylonitrile (PAN) [1] is preferable – patenting strategy is about hierarchical carbon consisting of PAN and other carbon-based materials, (ii) anode: starting from graphite for the sake of easy-start, hard carbon (or mesoporous carbon) and Si are investigated (Si is main but hard carbon is a sort of “insurance”) – anode is pre-lithiated instead of using explosive Li2S.

Possible further project (or I may have to do this at another place) can include (a) N-methylpyrrolidone (NMP) elimination from cathode manufacturing process, (b) doubling electrode thickness without compromising power density, and (c) reducing anode electrolyte wetting and solid-electrolyte interphase (SEI) layer formation period as Wood et al. [2] have suggested for cost reduction for conventional lithium-ion batteries based on intercalation materials. Regarding (a) NMP elimination from cathode manufacturing process, sulfur has a less positive potential than conventional LiCoO2 etc.; thus, there is no problem. Regarding (b) doubling electrode thickness without compromising power density, I already reported about increasing sulfur mass-loading from >> 2 mg cm-2 to 2 - 4 mg cm-2 (roll-press down to 50% instead of conventional 70 - 80%) [3]: by using high surface area anode materials, anode surface inactivation becomes less serious than when Li foil is used as an anode as I already implied [3] and mentioned [4]. Regarding (c) reducing anode electrolyte wetting and solid-electrolyte interphase (SEI) layer formation period, the pre-lithiation of the anode is a solution, already. Considering the compatibility with sulfur-based cathode, it may need a further improvement: it will be another project (a part of my personal future plan 3).

References

[1] J. Wang, J. Yang, J. Xie, N. Xu, Adv. Mater. 14 (2002) 963-965.

[2] D. L. Wood III, J. Li, C. Daniel, J. Power Sources 275 (2015) 234-242.

[3] T. Hara, A. Konarov, A. Mentbayeva, I. Kurmanbayeva, Z. Bakenov, Front. Energy Res. 3 (2015) 22.

[4] T. Hara, A. Konarov, A. Mentbayeva, I. Kurmanbayeva, Z. Bakenov, Front. Energy Res. 3 (2015) 22.

5. Flow-free zinc nickel battery. Market and technology analysis. (Nazarbayev University Graduate School of Business)

October 2015 to November 2015

- Supervision = 4 MBA candidates.

6. Design and engineering of ultimate three-dimensional electrochemical capacitors (3D-ECC) (Nazarbayev University Capstone Project)

September 2014 to April 2015

- Supervision = 5 bachelor's degree candidates.

- The uniqueness (novelty) of the capacitor is realized by employing a carbon-based porous current collector such as polyacrylonitrile-based carbon fiber paper or felt having an electrodeposited cathode material, polyaniline (PANI), thereon, thereby forming a porous cathode that offers a pseudo capacitance via surface ion adsorption/desorption accompanying PANI oxidation/reduction. Among many ongoing projects on lithium-ion battery research, various nano materials have been researched: nano materials have large surface areas and relatively small bulk volumes; thus, the surface chemistry becomes more dominant than the bulk one compared with conventional bulky materials. PANI is a well-established typical material that can be electrochemically active only via surface chemistry; therefore, it offers students a good opportunity to learn a required concept for understanding the basic concept on ongoing lithium-ion battery research without challenging any risky non-established chemistry.