Author – Aman Singh
Electrical power is one of the most basic human needs today. However, when the main power supply is not available, temporary storage of power in batteries becomes essential. Lead acid battery is the oldest and the most widely used rechargeable battery, which was invented in 1859. These batteries find vast range of applications right from automobile ignition systems, to standby and uninterrupted power supply due to their low cost, robustness and ability to supply high surge currents.
Lead acid batteries are made up of lead dioxide and metallic lead plates, which are dipped in sulfuric acid as their electrolyte. The high amount of lead used in these batteries is extremely toxic and is poisonous to humans as well as animals. During the manufacturing process, thousands of metric tons of lead fumes are released into the atmosphere by lead smelters. Even after proper disposal and recycling, more than 40,000 metric tons of this heavy metal end up in landfills every year. Moreover, sulfuric acid is also highly corrosive in nature. So there is an immediate need to look for viable alternatives to lead acid batteries for preventing lead’s detrimental effects on the environment.
Newer and greener cell chemistries are being developed to replace this century-old lead acid battery technology to meet the power demands of our ever growing industries. Typically, a better battery technology needs to provide much higher energy density (amount of energy stored) and more cycle durability (number of charge-discharge cycles) than the lead acid battery. Here are some of the relatively safer and better alternatives that are available in India to replace the lead acid battery –
Lithium-ion batteries (Li-ion) are composed of carbon and metal oxide electrodes along with lithium salt as the electrolyte. The electrolytes used are non-aqueous salts such as lithium hexafluorophosphate and lithium tetrafluoroborate. The Li-ion battery has much higher energy density and more cycle durability (number of charge-discharge cycles) then the lead acid battery. This battery does not contain any heavy metals such as lead or cadmium, hence is it categorized as non-hazardous waste. It contains metals like iron, copper, nickel and cobalt, which are generally considered to be safe for incineration and can be easily recycled and reused.
Lithium-ion batteries are today widely used in consumer durables such as mobile phones, laptops, cordless drill machines, etc. However, due to their high cost, their use is currently limited to smaller devices only. With further research and improved manufacturing techniques, the cost could be brought down to a level where developing nations like India will be able to completely replace lead acid batteries.
Widespread application of Lithium-ion batteries is limited due to their high cost. Although these are safer and better than the lead acid ones, they suffer some minor issues. They can be dangerous under certain circumstances since they contain a flammable electrolyte under pressurized condition; they could explode if they are overheated or overcharged. These batteries have a limited charging temperature range of 0oC to 45oC.
Nickel-Metal Hydride battery
Nickel-Metal Hydride (Ni-Mh) battery is a type of rechargeable battery that is made up of nickel oxyhydroxide (Ni-OOH) as the positive electrode and a hydrogen-absorbing alloy at the negative electrode. This is a newer variant of the Nickel-Cadmium battery (NiCd), which is essentially the same as the Ni-Mh, the only difference being cadmium used at the negative electrode instead. The Ni-Mh battery has two to three times more capacity than an equivalent NiCd battery and it is eco-friendly as well since it replaces heavy metal, cadmium.
The energy density of Ni-Mh is comparable to a Li-ion battery. Due to its low internal resistance, Ni-Mh batteries can deliver high power currents without the loss of capacity. Further, these batteries contain very few mild toxins that can be easily recycled. Nickel-Metal Hydride batteries are mainly used in standalone vacuum cleaners, remote control cars, digital cameras and other high drain devices. Applications of Ni-Mh batteries in electric vehicles include the Ford Ranger EV and the Honda Civic Hybrid.
The electrodes in Nickel-Metal Hydride battery undergo corrosion if placed in strong alkaline environments, resulting in gradual loss of power and permanent damage. Ni-Mh batteries have higher self discharge rates. These are less expensive than the LiON batteries but cost much more than the Lead acid batteries.
The Nickel–Zinc (NiZn) battery is another competitive technology in the industry. This battery’s electrodes are made up of zinc, which is a cheap element to process. Further, zinc is safe and non-toxic to the human health. NiZn batteries have high cell voltage, making them an excellent choice for situations where a higher voltage is required, like the flash in digital cameras. They do not have any flammable material and can be fully recycled. The NiZn cells are more powerful and possess higher energy density than all of the above types. NiZn batteries die out very fast, they do not last very long hence are commonly used where higher power is needed for very short time.
Nickel–Zinc batteries have a very short battery life, however research underway to enhance their durability. These batteries cannot be completely discharged to 0 volts or the cells may damage. Further, their production cost is very high since it requires special manufacturing techniques.
Tech Specs Table – Comparison of various battery technologies
|Energy Density (Watt/liter)||60 -110||250-620||140-300||260-300|
|Power to Weight Ratio (Watt/Kg)||180||250-340||250-1000||3000|
|Cycle durability (number of charge discharge cycles)||500-800||400-1200||500-2000||400-800|
|Nominal cell voltage (Volts)||2 V||3.6 V||1.2 V||1.85 V|
|Charge/Discharge efficiency||50 – 90%||80-90%||66%||50-70%|
|Toxic/Harmful material||Lead, H2SO4||Pressurized flammable electrolyte||Mild toxins||None|
|Availability in India||Available||AAA to D||AAA, AA, C||Not available|
|Cost - Rupees per watt-hour of energy||8 to 12||28 to 32||60 to 62||60 to 65|
Feature Image Source – Freestockphotos.biz