The battery is one of the most common types of energy storage technologies that store energy in the form of chemical energy and later convert it into electrical energy when required. Batteries are categorized into two types: primary and secondary batteries.
Primary batteries are non-rechargeable as the electrochemical reactions in these batteries are non-reversible. Examples of primary batteries include alkaline and dry-cell batteries.
On the other hand, secondary batteries are rechargeable and can be used continuously during their lifetime by recharging them once the charge has been drained out. Secondary batteries include lead acid batteries, lithium-ion batteries, Nickel-cadmium, etc.
This post will examine some key pros and cons of nine popular battery technologies today.
1. Lead acid
Lead acid batteries are the most affordable and widely used rechargeable batteries. Lead acid batteries, also known as wet batteries, are electrolytes that store electrical energy. It has lead dioxide in the positive plate, leads in the negative plate, and an electrolyte solution in a charged state with a high concentration of aqueous sulfuric acid. Each cell has an EMF of 2.1 volts. The battery comprises several cells connected in series to provide the required voltage. For the battery to produce voltage, it must first be charged. To allow current to flow into the cell, the voltage must be greater than 2.1 volts; otherwise, the charge will flow out.
- Low price: Lead-acid batteries cost significantly less for a similar setup than lithium-ion batteries. Lead acid batteries typically have a lower purchase (average cell cost of $65/KWh) and installation cost as compared to lithium-ion batteries.
- Tolerant to overcharging: Flooded lead acid batteries are tolerant to overcharging, making them less prone to thermal runaways, which reduces chances of catching fire or exploding as compared to lithium-ion batteries.
- Temperature tolerance: Lead acid batteries have a temperature tolerance of -40⁰ C to +50⁰ C. AGM batteries resist cold weather damage. When frozen, the electrolyte in the glass mat won’t expand like liquid preventing battery cracks.
- Weight: Most lead acid batteries are heavy. For traction applications, a lead acid battery would weigh more than three times that a lithium-ion battery.
- Sulfation: This phenomenon occurs in lead-acid batteries during normal operation upon subjecting to insufficient charging. Due to this, some lead sulfates do not recombine into electrolytes and convert into a stable crystalline form that does not dissolve on recharging. It results in longer charging times, low efficiency, and higher battery temperature.
- Serious environmental concerns: Lead acid batteries have serious environmental concerns. Lead and sulfuric acid can contaminate soil and groundwater if they leak. This can further cause fires and explosions and damage the ecosystem.
Lithium-ion batteries are rechargeable batteries originally designed for consumer electronics use. Lithium serves as the core of lithium-ion batteries. The electrolyte transports positively charged lithium ions from the anode to the cathode through the separator. In the anode, the movement of the lithium ions generates free electrons. This causes a charge to accumulate at the positive current collector. Electric current flows from the charge collector to the negative charge collector via a given device. This battery charges and discharges in cycles by generating electricity as lithium ions move between the anode and cathode. The energy stored by the battery is affected by the repeated charging and discharging cycles.
Several materials can be used as electrodes in lithium-ion batteries; the most common cathode is lithium cobalt oxide, and the most common anode is graphite. Other common cathodes include lithium magnesium oxide and lithium iron phosphates. The electrolyte in lithium-ion batteries is ether. The EV market’s rapid growth is propelling lithium-ion batteries’ growth.
- Compact size, as compared to bulky lead acid batteries.
- Longer service life: Lithium-ion batteries have a longer service life (1000-4000 cycles) as compared to lead acid batteries (500 – 1000 cycles).
- Faster charging rate, as well as compared to lead acid batteries.
- No memory effects: In certain batteries, after repeated charging/ discharging, the batteries memorize the decreased life cycle, hence the next time the battery is charged, it will have a significantly shorter operating life.
- Doesn’t require priming: Primming is a conditioning cycle applied to improve battery performance used in nickel-based batteries. Lithium-ion batteries do not require primming to improve battery performance.
- Lower self-discharging rate: Self-discharging rate of 0.35 – 2.5% as compared to lead acid batteries, which have a self-discharge rate of 5%.
- Protection circuitry to establish safe operation limits: Overcharging lithium-ion batteries can create unstable conditions inside the battery, increasing pressure and causing thermal runaway. Hence, they need protection circuitry to prevent excessive buildup of pressure and cut the flow of ions when the temperature is high.
- Unusable after deep discharge: Deep discharges could permanently damage the lithium-ion battery. It can lead to internal metal plating, causing a short circuit, thereby making the battery unsafe and unusable. A deep discharge limit (2 -2.5 V) should be set, and the battery should not be discharged lower than the limit.
- Restrictions in transportation: All lithium-ion cells and batteries are forbidden for transport as cargo on passenger aircraft as they can pose an unreasonable risk to safety, health, and property when transported.
- Sensitivity to high temperatures: Lithium-ion batteries must not be charged above 45⁰ C and discharged above 60⁰ C. These limits can be pushed higher at the expense of cell life.
3. Flow battery
Flow batteries are rechargeable batteries with two liquid electrolytes rather than electrolyte plates. An ion-selective membrane separates these liquid electrolytes, allowing ions to pass through and chemically react under charging and discharging conditions. Because of the ease with which electrolytes can be replaced, they are considered a better substitute for lead-acid, solid-state, and lithium-ion batteries.
Batteries are two separate electrolyte tanks (mostly vanadium) with different charges connected to a centrally located fuel cell stack within the flow. The electrolyte is pumped through the stack of fuel cells, where ion exchange occurs across a membrane. A reversible electrochemical reaction occurs during this exchange, allowing electrical energy to be stored.
- Lower levelized cost of storage: These batteries easily offer a service life of 25 years. Their capital expense is similar to lithium-ion batteries but has a much lower operating cost than lithium-ion batteries. Hence the cost of ownership could be less by a margin of 40%.
- Flow batteries can operate in ambient conditions (-10 to 60⁰C) without heating/air conditioning as compared to utility-scale lithium-ion batteries, which always require ventilation.
- Do not need voltage equalization: Lithium-ion batteries need voltage equalization to maximize the capacity of the whole battery pack and keep the cells away from overcharging and over-discharging. Flow batteries, on the other hand, do not need them.
- Flow batterie is non-flammable, non-toxic, and has no risks of explosion, unlike lithium-ion batteries.
- Requirement of larger tanks: to store large amounts of energy. Larger tanks increase the overall weight of these batteries as well.
- Complex battery systems: Flow battery systems are complex as they require pumps, sensors, secondary containment vessels, flow, and power management for their operation. These components make the battery system larger and more complex than other technologies.
4. High-temperature battery
These batteries use two liquid metals as electrodes and molten salts as electrolytes. In addition, the electrolyte is divided into three layers according to immiscibility and density. These batteries combine high energy, long life, high power density, and inexpensive materials to address grid-scale electricity storage issues. The anode, cathode, and electrolyte layers spread during activation at high temperatures because of their immiscibility and relative densities. The components of these high-temperature batteries remain solid at room temperature and can be kept inactive for a long time. Because of the electrolyte’s high ionic conductivity, ionic species move through it as the charging and discharging process takes place.
- Low cost: Compared to lithium-ion batteries.
- Higher operating temperatures: High-temperature batteries operate at high temperatures (245⁰-350⁰ C).
- They are immune to the degradation of the microstructural electrode.
- They can store energy for long hours.
- Active cell components are highly corrosive.
- They have a higher possibility of metallic solubility of metal electrodes in molten salt.
- Requirement of a heat source: These batteries require a heat source for maintaining operational conditions, which also drains the battery efficiency as the heat is maintained by using the battery’s stored energy.
- Immobility: The presence of a heat source makes this battery-less useable to mobile solutions.
A nickel-cadmium battery is rechargeable with electrodes made of nickel oxide hydroxide and metallic cadmium. Nickel-cadmium batteries comprise a metal case and a sealing plate with a self-sealing safety valve.
The cathode terminal is the cadmium layer. Above it is the separator layers (which provide OH ions). It’s also soaked in water to help with the initial reactions. Cadmium Oxide and Nickel Oxide are formed when nickel reacts with water and cadmium. This reaction is followed by electron flow, resulting in a potential difference between two terminals.
- Relatively Inexpensive when compared to newer chemistries.
- Tolerant to overcharging: Nickel-cadmium batteries are less sensitive to overcharging. Hence, this reduces the requirements for the charging regimes.
- Can be fully discharged: Nickel Cadmium batteries can be fully discharged without causing any damage to the battery as compared to other battery chemistries, which do not support full discharge.
- Reduced temperature sensitivity: As the electrolyte composition does not change during charging and discharging, Nickel Cadmium batteries are less susceptible to freezing at lower temperatures than lead acid batteries. NiCd batteries can tolerate temperatures up to -50⁰ C.
- Memory effect: After repeated charging/ discharging, the battery memorizes the decreased life cycle; hence the next time it is charged, it will have a significantly shorter operating life.
- Higher self-discharging rate: NiCd has a self-discharge rate of 10-20% as compared to lead acid batteries, which have a self-discharge rate of 5%.
- Toxic to the environment: Cadmium is a toxic and heavy metal, hence discarding these batteries will damage the environment.
6. Nickel metal hydride
NiMH is one of the most advanced and widely available rechargeable batteries on the market. Its positive electrode is made of Nickel Oxide Hydroxide, and its negative electrode is made of a hydrogen-absorbing alloy. The electrodes are separated by a permeable membrane, which allows ionic and electron flow between them. The membrane is immersed in the electrolyte and made of aqueous potassium hydroxide. This membrane undergoes no significant change during battery operation. They are alkaline battery substitutes due to their small size, compatible cell voltage, and leak and explosion resistance. A resettable fuse in the battery breaks the circuit if the current or temperature is too high. They are much safer than NiCad and produce more power. However, they do not outperform Lithium-Ion batteries in terms of performance.
- Higher energy density as compared to Nickel Cadmium batteries by a margin of 30-40%.
- Lesser requirement of periodic exercise cycles.
- Environment-friendly as no cadmium, lead, or mercury is used in these batteries.
- Resistant to leakage and explosion.
- Easier to store and transport than battery technologies like lead acid, flow batteries, etc.
- Expensive, as compared to NiCad.
- Higher self-discharging rate: Higher self-discharging rate (10-15% in first 24 hours, then 10-15% per month) as compared to lead acid or lithium-ion batteries.
- Complex charging algorithm: NiMH batteries use a dT/dt charge system which is more expensive as compared to the charging methods of NiCd or Li-Ion batteries. Also, extended trickle charging can damage a NiMH battery; hence a timer should be used to regulate the recommended total charging time.
7. Metal-air battery
Metal air batteries have metal anodes with aqueous or nonaqueous electrolytes. It creates voltage from the availability of oxygen molecules (O2) at the cathode, which reacts with positively charged metal ions to form an oxide and generate electric energy. These batteries hold great potential to resolve future energy and environmental issues.
The type of anode used in these batteries determines whether the electrolyte is aqueous or nonaqueous; the air-breathing cathode frequently has an open porous architecture that allows continuous oxygen supply from the surrounding air. Future energy and environmental problems could be greatly reduced by using metal-air batteries. It produces voltage by reacting positively charged lithium ions with oxygen molecules (O2) at the cathode to form Li2O2 and produce electricity23. Metal is oxidized at the anode during discharge, while O2 in the surrounding air is reduced.
- Less charging time: Metal air batteries take lower time to charge (10 mins) as compared to lithium-ion batteries or any other chemistry.
- Higher energy density: Metal air batteries have a higher energy density (350-500 Wh/Kg) as compared to lithium-ion batteries (100-325 Wh/Kg).
- Dendrite formation: During the charging cycle, the chemical and electrochemical processes drive a complex reaction resulting in the deposition of dendrites inside the battery.
8. Solid state batteries
In contrast to the liquid or polymer gel electrolytes used in other Li-ion batteries, solid electrodes, and electrolytes are used in solid-state batteries. Future-looking, highly developed, next-generation batteries that deliver high performance and safety are solid-state batteries. Solid-state batteries are safe, non-flammable, have less self-discharge, and have high energy density (since cells are 80–90% thinner) (electrolyte does not get heated much, so it suits fast charging).
On the other hand, manufacturing solid-state batteries are pricey. Due to the use of solid electrolytes, their conductivity is also reduced at low temperatures. Additionally, because of the uneven deposition of lithium during the charge-discharge process, Li dendrites frequently form at the lithium metal anode. Short circuits may result from these dendrites’ penetration of the separator.
- Non-toxic as compared to other battery technologies.
- Very low self-discharge rate: of 1.5-2% as compared to lithium-ion batteries which have a self-discharge rate of less than 5%.
- Safety: Solid-state batteries are safer and more stable as compared to lithium-ion batteries with liquid electrolytes.
- Expensive: Mass production and manufacturing methods are quite expensive and complex as compared to other battery chemistries.
- They have less conductivity at low temperature.
- Dendrite formation: Dendrites commonly form during electrodeposition during the charging and discharging cycle, causing degradation in their performance.
Sodium-ion batteries (SiB) work on the same principle as lithium-ion batteries in that sodium ions alternate between cathode and anode to charge and discharge energy. Sodium ions have a larger ionic radius than Lithium ions, resulting in different battery materials. Because graphite, the dominant anode in Limbs, cannot be used in SiBs, Hard Carbon is the anode of choice. In SiBs, aluminum foil is known to be a better current collector than copper foil. The main electrolytes in SiBs are sodium-based NaFP6 rather than the lithium-based LiFP6 found in Lithium-ion batteries.
Sodium-ion batteries, by definition, do not contain rare metals and are, therefore, low-cost battery solutions. Sodium-ion batteries share several constituents with Lithium-ion batteries, including Aluminum, Iron, Potassium, Magnesium, Titanium, Zinc, Copper, and other abundant elements compared to Nickel, Cobalt, and Lithium.
- Low battery BOM cost compared to LFP batteries (-25%28).
- Abundance of raw materials in comparison to Lithium-ion batteries.
- Broader operating temperature range with more than 90% capacity retention at -20°C.
- Capability to be transported at zero volts relative to Li-ion batteries which need to retain 40% of charge to preserve performance.
- Lower energy density in comparison to Li-ion batteries leads to higher weight-limiting applications in Grid storage.