Introduction
The ever-growing energy demand with the increasing population and rise
in the economy has led to a rapid increase in the total energy demand
globally.1,2 More than 80 % of the energy supplies
come from carbon-rich non-renewable energy sources in the current
situation.3 Battery technologies are being established
rapidly due to its increasing demand in portable devices, stationary
frameworks, and electric vehicles.4,5 Among present
various battery technologies, Lead-Acid (PbA), Nickel-Metal Hydride
(NiMH), Nickel-Cadmium (NiCd) and Lithium-ion (Li-ion) are the major
chemistries towards different applications due to their specific
characteristics related to energy density, power density, durability,
and economic feasibility.6–8 Even though the growing
popularity of Li-ion and NiMH batteries, the demand for PbA batteries
grows proportionately due to their ease in availability, manufacturing,
maintenance, reliability, recycling and cost.9 Lead
acid battery demand is higher in large-scale applications such as
renewable energy storage system, e.g., wind and solar technologies
despite having lower energy density (< 50 Wh/kg). Lead acid
battery market share is the largest for stationary energy storage system
due to the development of innovative grid with Ca and Ti additives and
electrodes with functioning carbon,
Ga2O3 and
Bi2O3 additives.10,11In the current scenario, leak-proof and maintenance-free Sealed Lead
Acid batteries (SLAs) are used in multiple applications such as
motorcycles, ATVs, home alarm systems, toys, backup systems, workout
equipment and generators.12–14
Temperature plays a key role in the battery operation as it affects the
cycle life, performance, and available capacity. The PbA battery system
are designed to perform optimally at ambient temperature (25 °C) for
performance, capacity and cyclability. However, they degrade faster when
operated at higher than ambient conditions leading to shorter cycle life
due to the degradation of electrode and grid
materials.6 The oxidation and reduction rates increase
significantly at both Pb anode and PbO2 cathode, leading
to higher discharge capacity at elevated
temperatures.7,12 Besides having a deleterious impact
on the cycle life at elevated temperatures, several other impacts
include self-discharge reactions, loss of electrolyte, active material
shedding, grid corrosion, and loss of mechanical strength of the
positive electrode (PbO2).15–17Shedding or loss of positive active mass particles into the electrolyte
could also increase corrosion and macro defects on the lugs of the
negative electrode.16,17 While operating at lower
temperature, low electrolyte conductivity and active material results in
reduced available capacity.6 To reduce the corrosion
or degradation rate of the PbA battery, limiting the internal
temperature to < 60 °C could minimize the electrolyte
vaporization.18 The cell internal pressure should be
in acceptable range for long term optimum performances. However, it was
reported that charging efficiency and cyclability were improved under
high internal pressure with the favorable crystal structure of the
electrodes.16 Performance evaluation of the batteries
at elevated temperatures and near-freezing temperature is critical for
using these batteries for outdoor energy storage applications in hot and
cold conditions.6
The adverse effect of temperature also includes reduced discharge
capacity, increased internal resistance and self-discharge with
increased duration at extreme temperatures. Typical PbA batteries
undergo many charge/discharge cycles during their life
time.10 Hence it is necessary to understand the
complete cycling behavior of PbA battery in various operating
conditions, including incomplete charging, slow discharging, extreme
conditions such as temperature fluctuations, and vibrations that cause
degradation of internal components leading to failure of the battery.
In this work, a systematic study was conducted to analyze the 2V/5Ah
Enersys® Cyclon sealed lead-acid (SLA) cells cycled at -10, 0, 25 and 40
°C, to minimize the experimentation duration as these conditions are
practical for vehicles used or stored in frozen tundra and arid desert
climates. To evaluate these condition, electrochemical impedance
spectroscopy (EIS) was carried out to evaluate internal resistance
(ohmic and charge transfer) to explain the degradation mechanism of the
battery. Further, electrode materials were extracted post cycling
analysis for morphology characterization using X-ray diffraction (XRD),
and Energy-dispersive X-ray spectroscopy analysis (EDX). SLA batteries
were observed to degrade faster at higher temperatures (25 and 40°C).
However, the degradation is minimal at lower temperatures (0 and -10 °C)
due to less active material and slower kinetics. The impedance values,
x-axis intercept of Nyquist plot was observed to increase with cycling
at all the temperatures.