Lead Acid Battery with Composite Cathode of Active Material and Graphite Current Collector
Authors: Sugimoto Kaito , Ohira Fumiya , Hano Yuta , Okano Hiroshi , Iwai Taichi , Yabutsuka Takeshi , Takai Shigeomi , Akamatsu Yusuke , Hosokawa Toshihiro , Kuninaka Masayuki , Miki Motomi , Yoshikawa Susumu , Yao Takeshi 
Published: July 2021

Introduction

Lead Acid Batteries (LAB) are used in various fields, due to its low cost and excellent recyclability. Conventionally, LAB cannot be recharged after over-discharged and its performance is greatly declined. We have found that the above deterioration is causedby the formation of α-PbO2 on the surface of cathode active material β-PbO2 due to the reduction by local cell reaction between β-PbO2 and lead current collector. We also have revealed that the formation of α-PbO2 can be prevented by using gold instead of lead as current collector. In this case, the LAB can be recharged even after either discharging to 0 V or discharging to 0 V followed by 48 h open circuit [1,2]. In the case of carbon, electrode potential does not come out, so we thought that carbon has a role of stopping local cell reaction. We revealed that the LAB using graphite sheet with 5wt% polypropylene as current collector has high resistance to over-discharge [3,4,5]. This LAB can charge-discharge without performance degradation even after full discharge followed by 48 h rest period. In this study, we fabricated composite cathode composed of β-PbO2 as active material and expanded graphite as current collector, in order to get higher performance and ease of fabrication. We investigated performance of the LAB using the composite cathode.

Experiment

We made various kind of the composite cathode composed of β-PbO2 of 0.18-3.6 g, expanded graphite of 1.8 g and polypropylene of 0.09 g by a pressure molding. We conducted charge-discharge experiments by using the composite cathode. We used two-electrode glass cell for charge-discharge experiments. We used 35 % H2SO4 as electrolyte and lead plate as anode. Composite cathode was processed to 40 mm × 14 mm and the area immersed in sulfuric acid was 10 mm × 14 mm. As the stabilization cycle, we repeated discharge at 0.25 mA for 30 min and charge at 2 mA for 20 min for 20 times, then we conducted charge discharge experiment.

Results and discussion

After the stabilization cycle, we discharged LAB deep to 0 V and opened the circuit for 48 h, then we resumed charge-discharge cycle.
Figure 1(a) shows the charge-discharge characteristics of conventional type LAB using lead plate cathode current collector. Conventional type LAB could not resume charge-discharge cycle after full discharge followed by48 h open circuit.
Figure 1(b) shows the case of the LAB using composite cathode. It is indicated that the LAB can resume charge-discharge cycle even after full discharge followed by 48 h open circuit. It is confirmed that the composite cathode made the LAB so durable to over-discharge.
Figure 2 shows detailed discharge curve of the LAB using the composite cathode composed of β-PbO2 of 3.6 g, expanded graphite of 1.8 g and polypropylene of 0.09 g. Weight composition of β-PbO2 in this composite cathode is about 65%. The charge rate was 2 mA, and the discharge rate was 0.1 mA, respectively. The flat discharge potential around at 1.6 V was observed. This means that the LAB using the composite cathode has excellent practical performance.
It was indicated that the composite cathode made the LAB not only very durable in over discharge but also highly practical for use.

Reference

[1] T.Iwai, D.Kitajima, S.Takai, T.Yabutsuka and T.Yao, J. Electrochem. Soc. Vol 163, Issue 14, A3087-A3090 (2016)
[2] T.Iwai, M.Murakami, S.Takai, T.Yabutsuka and T.Yao, Journal of Alloys and Compounds, Vol 780, 85-89 (2019)
[3] T.Yao, H.Okano, T.Iwai, S.Takai, T.Yabutsuka, T.Hosokawa, N.Misaki, K.Kurihara “Positive Electrode for Lead Storage Battery and Lead Storage Battery Using Same” PCT/JP2018/005947
[4] Y.Nakamura, T.Ohkubo, H.Okano, T.Inoue, T.Hosokawa, A.Takeda, T.Iwai, T.Yabutsuka, S.takai and T.Yao, 235th ECS Meeting. Soc. Z01-2143 (2019)
[5] Y.Hano, H.Okano, T.Inoue, T. Hosokawa, A.Takeda, T.Iwai, T.Yabutsuka, S.Takai, and T. Yao, PRIME 2020. Soc. Z01-3448 (2020)

Figure 1