1. Carbon Additives for Improved Lead Acid Battery Performance
Nisrit Pandey
Guy Reynolds
André Deiraz
Advisor: Dr Benjamin Church
Department of Materials Science and Engineering

2. Introduction and Objective
Lead Acid Batteries currently feature poor Dynamic Charge Acceptance (DCA)
This adversely affects start-stop and regenerative braking capabilities
Carbon Additives feature high surface area and are known to improve DCA and prevention of PbSO4 Passivation.
Effectiveness of Carbon Nanotubes Previously Tested
Current Focus on Graphene

3. The Slurry and Electrochemistry+
Leady Oxide
Carbon Additives
Lignin
BaSO4
10% PVDF +NMP
NMP
Electrochemistry at the negative plate
All conditions: PbSO4 + 2H+ + 2e- ↔ Pb + H2SO4
Overpotential conditions: 2H+ + 2e- ↔ H2
2H2O ↔ O2 + 4H+ +4e-

4. Test Setup Cyclic Voltammetry (CV) Conditions Test Setup:
Working Electrode: cm2 diameter Pb-Battery Anode with the Slurry Layer
Counter Electrode: Copper (Cu) Plate
Reference Electrode: Mercury/Mercurous Sulfate (Hg/Hg2SO4, saturated K2SO4) design
Electrolyte: 1.28 g/ml aqueous H2SO4 (Standard Pb-Acid Battery electrolyte)
Cyclic Voltammetry (CV) Conditions
The CV was carried out using Princeton Applied Research Versastat 3 under the following conditions:
Potential Voltage Window of -1.8 – 1.9 V
Scan Rate of 20µV/s
10 Cycles
Copper Counter Electrode
Hg/HgSO4 reference electrode
Pt wire connected to the anode
Teflon Blocks to hold H2SO4 and anode

5. Figure (a) shows one complete CV plot
Figure (a) shows one complete CV plot. Figure (b) is the calculation of hydrogen evolution potential and slope. Figure (c) is the measurement of DCA a c b
The CV Results
High Hydrogen Evolution denotes faster and easier evolution of Hydrogen – Increased Loss of Water!
Carbon Additives = High Dynamic Charge Acceptance but may accelerate deterioration
Water Loss in elevated temperature = carbon oxidation, hydrogen evolution and grid corrosion!

6. BET Surface Area
The figure on the left shows the absorption/desorption BET chart used to measure the surface areas of the graphenes.
The testing was done using liquid nitrogen (77K) adsorption to determine the total surface area
This will be compared to dynamic charge acceptance.

7. Dynamic Charge Acceptance and Hydrogen Evolution
As hypothesized the Dynamic Charge Acceptance of the batteries dramatically increases with the increase in total surface area of the graphene. Increasing surface area by 80 times nearly doubled the DCA.
There is also a dramatic increase in H2 evolution for anodes with high surface area graphene (No. 90 and No.105).
Average DCA from Carbon Nanotubes as carbon additive was determined to be around the graphene (~0.0003) however, its Hydrogen evolution was doubled (~0.06) owing to much higher surface area.

8. Conclusions
Addition of Graphene and Carbon Nanotubes leads to improved Dynamic Charge Acceptance (DCA) properties due high carbon surface area
Increase in surface area of carbon leads to increased electrolysis of water and hydrogen evolution, Therefore, electrochemical properties of these carbons must be properly studied before putting them to practice.
The test procedure set up, therefore, allows for better quantification of DCA and materials selection without having to create large batteries.
The test method developed provides a good and repeatable method of measuring DCA, which is a significant challenge in Pb-Acid Battery Industry.

9. Acknowledgements
Dr. Benjamin Church
Johnson Controls Inc.
SURF Award