What are various battery technologies available?
From first ever battery invention in 1800, by Volta; till the latest technology which allows us to charge up our smartphones; the progress in battery technology seems to be unbelievable. But did that happen in a single battery technology? Not really. Every new battery technology tends to use different construction material to provide more energy density in as small size as possible.
Here we are going to take a quick overview on famous battery technologies from past and now. Every new battery technology was developed to overcome issues faced in preceding technologies. But how much did their efforts actually succeed?
Every battery manufacturer is well aware and learns from their customer reviews that what new they need to introduce in improved products. Sometimes new technologies tend to have higher prices but eventually new inventions help them to bring down the prices.
We will check all possible attributes while comparing all the battery technologies. We scrutinize battery technologies in terms of energy density as well as life cycles, maintenance requirements, self-discharge, operation cost etc.
Let’s evaluate every battery technology for advantages and limitations
Nickel Cadmium (NiCd)
Nickel Cadmium cell. Image courtesy: Google
Nickel Cadmium chemistry is well matured and understood technology but it has relatively low energy density. NiCd chemistry is used where long life is required in economic price.
NiCd performs well in rough working environment, but large crystals are formed on cell plate if the battery is kept idle which is also called as “Memory Effect”. Because of the memory effect cell loses it’s performance. NiCd batteries are needed to fully charge periodically to avoid this damage to the charge capacity.
Among rechargeable battery technologies, NiCd is popular choice for portable devices.
Batteries with higher densities overcoming shortcomings of NiCd are causing diversion from NiCd chemistry. Also it is noticed that NiCd contains non-environment friendly toxic elements which made consumers look for better technologies.
- Fast and simple to charge
- If maintained well, can provide almost 1000 charge/discharge cycles
- Good Load Performance
- Allows recharging at low temperature
- Simple storage and transportation (Most airfreight companies accept NiCd batteries without any special conditions)
- Good low temperature performance
- NiCd batteries are the most rugged rechargeable batteries
- Economic price: Lowest in all types of rechargeable batteries
- Available in wide variety of size, but cylindrical cells are relatively more famous.
- Comparing with newer technologies, NiCd has lower energy density
- Memory effect causes NiCd to lose its charge capacity and eventually the performance
- Contains toxic elements
- NiCd cells have a high self-discharge. They are needed to recharge after storage
- Nickel-Metal Hydride (NiMH)
NIMH cell. Image Courtesy: lowes.com
NiMH has higher energy density than NiCd but it fails to give life cycle as good as NiCd. NiMH has advantage of not containing any toxic metal which makes it environment friendly. NiMH cells are used for portable appliances. NiMH batteries offer up to 40% higher energy density than NiCd chemistry. Still NiMH cells are less durable than NiCd cells. Under heavy load and at high temperature NiMH loses it’s service life. Also, NiMH has high self-discharge, even more than NiCd.
NiMH technology has improved greatly over the years, but it still has limitations.
- 30-40% higher capacity than standard NiCd chemistry. NiMH cells have potential for yet higher energy density.
- Less prone to memory effect, so periodic charging is required less often
- Simple to store and transport
- Environment friendly
- Limited service life. Performance starts degrading after 200 to 300 cycles.
- Limited discharge current. Although NiMH cells are capable of delivering high discharge currents, repeated high discharges affect the battery life. Best results are obtained only when current is constrained to 0.2C or 0.5C discharge currents.
- High self-discharge. NiMH has nearly 50% higher self discharge compared to the NiCd cells. Trickle charge is critical in NiMH and it needs to be controlled properly.
- Performance degrades if stored in higher temperature than operating temperatures.
- Cell needs to be charged fully periodically to avoid crystal formation
- Lead Acid
Image courtesy: Google
charging and discharging cycle of Lead acid cells. Image courtesy: researchgate.net
Lead Acid battery was invented by French Physician Gaston Planté in 1859. Lead acid was the first rechargeable battery which is used for commercial purposes. Today, flooded lead acid batteries are used almost in all automobiles, UPS Systems etc.
During 1970s, maintenance-free lead acid batteries were developed. The liquid electrolyte was replaced by moistened separators and enclosure was sealed. Also safety valves were added to allow venting out the gas generated during charge and discharge process. According to the requirement for various applications, two battery designs were developed: First, Small Sealed Lead Acid (SLA) and Second, large Valve Regulated Lead Acid (VRLA). Technically both batteries are similar. Unlike the flooded lead acid batteries, both SLA and VRLA are developed with a low potential to prevent battery from reaching its gas generating potential during charge cycle. Excess charging can cause generation of gas and water. That’s why; these batteries cannot be used up to their full potentials.
Lead acid battery does not suffer from memory effect. Charge retention capacity of SLA is better than NiCd batteries. NiCd batteries self-discharge approximately 40% of its stored capacity in 3 months, when SLA faces same self-discharge level in 12 months.
SLA does not support fast charging. Typical charging time for SLA is 8 to 16 hours. SLA always needs to be stored in charged state. IF battery is left discharged for significant amount of time, it causes sulfation. Sulfation makes battery difficult to charge.
Also battery eventually loses its capacity slowly if subjected to deep charge discharge cycles. So using SLA to its full potential is not possible. SLA provides only 200 to 300 cycles only when maintained properly. The main reason for the relatively short life is grid corrosion of the positive electrode, depletion of active material and expansion of the positive plates. These changes are prominent at elevated temperature.
The operating temperature is needed to be maintained around 25⁰C. The thumb rule is, every 8⁰C rise in temperature will cut the battery life in half.
In all modern rechargeable batteries, the lead acid batteries have the lowest energy density which makes it unsuitable for portable applications. Also lead content in batteries make them non-environment friendly.
- Economic and very simple to manufacture. In terms of cost per watt hours, the SLA batteries are the most affordable
- Matured and well understood technology
- No memory effect
- Cannot be stored in discharged state
- Low energy density
- Only limited number of charge-discharge cycles
- Lead content makes it environment unfriendly
- Transportation restrictions on flooded lead acid batteries
- Thermal runaway can occur if improperly charged
- Very bulky, cannot be used for portable applications
- Lithium Ion
Lithium Ion cell. Image courtesy: osha.gov
Pioneer work for Lithium batteries began in 1912 under G.N. Lewis but non–rechargeable lithium batteries were available commercially in early 1970s. Lithium has greatest electrochemical potential and provides highest energy density.
Several attempts were made in 1980s to make Li-ion rechargeable batteries but failed due to safety issues because of inherent instability of lithium metal, especially during charge cycle. Several research attempts were made to shift to non-metallic Li-ion battery technology. Although Li-ion has slightly less energy density, it is safer to use than Lithium metal. in 1991, Sony Corporation commercialized Li-ion rechargeable batteries and today li-ion technology is looked upon as the most promising technology of present and future.
Energy density of the Li-ion battery is twice that of the standard NiCd battery. Also potential efforts are taken up to increase it more than three times that of NiCd. Because of the high cell voltage, it is possible to make batteries with one cell only. This simplifies the designs of portable devices such as mobile phones etc. Low cell resistance allows drawing more current.
Li-ion batteries are low maintenance batteries. Li-ion cells do not suffer from memory effect and also it does not require periodic charging to prolong the battery life. Self-discharge is less than half that of NiCd.
Despite a lot of advantages over preceding battery technologies, Li-ion chemistry has some drawbacks as well. Li-ion cells are fragile and they require protection circuits to maintain safe operation. Protection circuit limits the peak voltage of each cell during charging cycle and prevent the cell voltage from dropping too low on discharge. In addition cell temperature is monitored to prevent rise in temperature during the operation.
Aging of Li-ion cells are main concern. Storing the cells in a cool place slows down the aging process. Also, cells should be partially charged during storage.
- High energy density. Has potential for yet higher capacities.
- Low self discharge
- No memory effect
- No periodic charging needed
- Low maintenance
- Requires protection circuit to limit voltage and current for safe operation
- Subject to transportation regulations. One has to follow some rules and regulations on method of transportation while sending shipments
- Expensive to manufacture than other battery technologies
- Not completely matured technology
- Lithium Ion Polymer
Lithium Ion Polymer Cell. Image Courtesy: Google
Li-Ion polymer batteries use different type of electrolyte for the construction. The Li-ion cells were originally developed in 1970s which were using dry solid polymer electrolyte. This polymer electrolyte is plastic like thin film which does not conduct electricity but allows an exchange of ions. The dry polymer cells offer simplifications in terms of fabrication, durability and safety. Also Lithium Ion Polymer chemistry allows constructing thin profile geometry.
Li-ion Polymer technology offers maximum safety as no flammable liquid or gelled electrolyte is present in it.
Drawback of Li-ion Polymer cells is, they have high internal resistance which results into poor conductivity. Heating the cell around 60⁰C can increase the current burst but it is not suitable for portable applications such as cellular phones.
Small Li-ion polymer battery is made more conductive by using some gelled electrolytes. Most of the commercially used polymer batteries are using gelled electrolyte.
Though, Li-ion batteries still do not have any cost advantage. Also its energy density is still lower then the Li-ion Technology.
- Light weight
- Very small profiles are possible
- Improved safety; more resistant to overcharge and less change of electrolyte leakage
- Low energy density and less charge discharge cycles
- Expensive to manufacture