g'' g'functional hydrogels with enhanced physiochemical properties for highly energy...

Functional hydrogels with enhanced physiochemical properties for

highly energy dense rechargeable Zn-MnO2 batteriesAditya Upreti1, Meir Weiner1, Gautam G. Yadav1*, Jinchao Huang1, Roman Yakobov1, David J. Arnot2, Noah B. Schorr2, Nelson S.

Bell2, Timothy N. Lambert2, Sanjoy Banerjee1

*Corresponding author: gautam@urbanelectricpower.com1. Urban Electric Power Inc., Pearl River, NY, 2. Sandia National Laboratories, NM

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1. Develop rechargeable energy dense

Zn|MnO2 battery systems with non spill-

able characteristics using a polymer

hydrogel electrolyte.

2. Increase the energy density of Zn|MnO2

batteries by increasing utilization of the

electrodes and test in applications like

solar microgrid.

Objective

Introduction

1. Zn|MnO2 batteries are resilient to abusive

cycling conditions and safer than most

traditional batteries. But in order to

compete with the status quo of lead acid

batteries, Zn|MnO2 batteries need to have

high energy densities.

2. In order to achieve high energy densities

in Zn|MnO2 batteries, higher capacity

utilization of the electrodes is paramount.

However, accessing higher capacity

utilizations of the electrodes is challenging

because of the following reasons:

• At high utilizations, Zn mobility is high and

the probability for Zn migration to other

regions of the cell increases substantially

• MnO2 volume expansion is extensive at

high utilizations

3. These issues can be addressed by using

a hydrogel electrolyte. The hydrogel

electrolyte:

• Limits Zn mobility within the cell

• Prevents MnO2 from expanding un-

controllably

To achieve optimal battery performance the

hydrogels need to be tuned for parameters

like viscosity and free KOH concentration.

An in-situ gelation process based on the free

radical polymerization scheme of acrylic acid

has been adopted as:

i. CH2 = CHCOOH + KOH excess ⟶ CH2 =CHCOO

−K

+Potassium Acrylate + H2O

ii. CH2 = CHCOO−K

++Initiator ⟶

Potassium Polyacrylate Hydrogel

Hydrogel Preparation

Cell Preparation

1. All electrodes used in the experiments

were manufactured on the UEP electrode

line.

2. Various cell geometries were tested like

prismatic and cylindrical.

3. Control cells were cycled using liquid

electrolyte

Results & Discussion

Cell Performance:

1. 20% Utilization of Zn capacity (820mAh/g)

in a gel system

2. 20% utilization of Zn capacity (820 mAh/g)

Comparison between a hydrogel system

and a conventional electrolyte system

3. 30% utilization of Zn capacity (820mAh/g)

4. Very high utilization (>50%) of Zn capacity

(820 mAh/g)

The hydrogel electrolyte conditions were optimized

by varying the final KOH concentration in the network

and the density of crosslinking. Very low KOH

concentrations limit utilizations for both the

electrodes while high KOH concentrations decrease

sustained high energy performance.

Optimal crosslinking density was achieved using

conventional crosslinking agents and the gel point

was defined using the crossover point in the

rheological studies.

Additionally, rheological behavior was studied as a

function of KOH concentration, initiator conditions

and crosslinker content to get a hydrogel with

optimal electrochemical performance.

Conclusion

• Sustainable high energy performance for Zn-

MnO2 battery systems has been shown.

• A non spill-able hydrogel electrolyte has been

developed

Future Work

• Correlating the rheological behavior of the

hydrogel with varying preparation conditions to

electrochemical performance.

• Publishing the findings in peer reviewed articles

Acknowledgement

This work was supported by the U.S. Department

of Energy, Office of Electricity. Sandia National

Laboratories is a multi-program laboratory

managed and operated by National Technology

and Engineering Solutions of Sandia, LLC., a

wholly owned subsidiary of Honeywell

International, Inc., for the U.S. Department of

Energy's National Nuclear Security Administration

under contract DE-NA-0003525. Dr. Imre Gyuk,

Director of Energy Storage Research, Office of

Electricity is thanked for his continued support. The

views expressed herein do not necessarily

represent the views of the U.S

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Sandia National Laboratories is a multi-mission laboratory managed and

operated by National Technology & Engineering Solutions of Sandia, LLC, a

wholly owned subsidiary of Honeywell International Inc., for the U.S.

Department of Energy’s National Nuclear Security Administration under

contract DE-NA0003525.

SANDNo._