Introduction
At EAI’s consulting division and more so at EV Next, our specialty consulting division for e-mobility and electric vehicles, we get a number of enquiries from large companies as well as startups/small businesses keen on investing in the battery space. It is fairly clear to most of them that battery storage is one of the most exciting and fast-growth areas to invest in.
There can no doubt about the main inference: Energy storage, especially battery-based energy storage, is becoming a large and an attractive business opportunity that also presents a critical business case: after all, if the future world we will all be powered by renewables and transported by electric vehicles, energy storage becomes an almost indispensable ingredient in the mix.
Of course, there are avenues beyond batteries for energy storage – fuel cells, thermal storage, flywheels, pumped hydro, compressed air… – but it is a fair bet that batteries will comprise one of the largest, if not by far the largest, component of energy storage market for the foreseeable future.
Not surprising then that our consulting team at EAI had suddenly seen a significant rise in battery-related market intelligence and consulting in the past two years. Interestingly, almost all the work we had done was for Li-ion batteries, with most of the businesses approaching us for assistance almost having decided that there was really no business left in Lead Acid batteries anymore.
Our specialty focus areas include 
It was almost the lead acid business was dead. But is it?
The answer is quite nuanced. And one should have expected it to be, given the large and diverse end applications for batteries, and also because of the complex interplay of technology, life cycle dimension, pricing and cost trends, and more.
While we do not intend this blog post to be a primer on either lead acid or Li-ion batteries, we will try to point out the key characteristics and trends for these two types of batteries to arrive at an inference.
Let’s first look at the various end uses of lead acid batteries:
- UPS and inverters
- Solar power plants
- Natural gas power plants
- Backup power stations
- Electric vehicles
Characteristics, advantages and disadvantages of lead acid batteries vis-a-vis Li-ion batteries
Lead acid batteries
The lead-acid battery is a combination of lead, lead dioxide, and an electrolyte composed of sulfuric acid and water.
Lead acid batteries have been around for more than 130 years since the first known type of lead-acid battery was first suggested by the French physicist Dr. Planté in 1860. They are a highly reliable storage solution. Lead-acid batteries are low cost, can operate under a wide range of temperatures, have strong surge capabilities, high efficiency (65-80%), and are usually good for uninterruptible power supply, power quality, and spinning reserve applications.
The resources for the manufacture of lead acid batteries are easily available in many countries. Additionally, almost 98% of the materials used in a lead–acid battery is recyclable.
All the above factors make lead acid batteries the most widely used rechargeable electrochemical devices for small and medium-scale storage applications, currently occupying over 50% of the total global battery market as of 2019. These factors also make lead acid batteries a serious contender to be used in electric vehicles and renewable energy, specifically solar power plants.
The major disadvantage of the lead acid battery is that these have a low energy density (30-50 Wh/Kg) and a relatively short life (500-1,000 cycles) compared to other battery types such as Li-ion.
Commercially available lead-acid batteries are of two main types:
- The flooded lead acid battery is the cheapest and tends to be used in automotive and industrial applications
- The sealed lead acid battery, also called valve-regulated lead-acid (VRLA) has been rapidly used in a wide range of applications including power supplies and stand-alone power supplies for remote areas.
Flooded lead acid batteries
Flooded lead acid batteries are the most commonly used batteries in many storage applications. They have long lives and low costs, and can operate safely on a wide temperature range with little need for temperature control. Their main drawback is that they require regular maintenance.
Valve Regulated Lead Acid (VRLA) batteries
VRLA batteries require much less maintenance compared to flooded type; in addition, they also do not emit any gases that flooded batteries sometimes do. On the other hand, VRLA batteries might require stricter control of temperature as they cannot cope with significant water loss caused by elevated temperatures.
There are two main types of VRLA batteries:
- Gelled Electrolyte Sealed Lead Acid: These batteries contain a silica type gel in which the electrolyte is suspended. The advantage of these batteries is that they would not spill and they also require little maintenance.
- Absorbed Glass Mat (AGM) Batteries: In this type of battery, the electrolyte is suspended in a very fine fibre boron-silicate glass mat instead of a gel. Similar to gelled batteries, they will not leak acid even when broken, and hence are safer to handle compared to the flooded lead acid batteries. AGM batteries also have features such as lower self-discharge rate and higher tolerance to temperature variations. But AGM batteries are more expensive compared to a standard flooded lead acid battery of similar rating.
Lithium-ion batteries
Lithium-ion batteries already power a wide variety of consumer goods ranging from mobile phones to children’s toys to cars and e-bikes. Today, they are used in stationary grid energy storage systems too. The batteries have nominal cell voltages in the range 3.2-3.8 V and sport energy densities up to 200 Wh/kg.
There are multiple li-ion battery chemistries in use currently, based on the choice of cathode and anode.
Cathode materials
Prominent combinations of the cathode materials include oxides of Lithium Nickel Cobalt Aluminum (NCA), Lithium Cobalt (LCO) and Lithium Nickel Cobalt Manganese (NCM or NMC) as well as Lithium Iron Phosphate (LFP).
- Nickel Manganese Cobalt (NMC)
- Nickel Cobalt Aluminum (NCA)
- Lithium Iron Phosphate (LFP)
- Lithium Manganese Oxide (LMO)
- Lithium Cobalt Oxide (LCO)
Details on the prominent cathode chemistries are provided below.
One of the most successful Li-ion systems is a cathode combination of nickel-manganese-cobalt (NMC). The secret of NMC lies in combining nickel and manganese. Nickel is known for its high specific energy but poor stability; manganese has the benefit of forming a spinel structure to achieve low internal resistance but has a low specific energy. Combining the metals enhances each other’s strengths.
Lithium iron phosphate (LFP) batteries offer good electrochemical performance with low resistance. This is made possible with nano-scale phosphate cathode material. The key benefits are high current rating and long cycle life, besides good thermal stability, enhanced safety and tolerance if abused.
LFP is more tolerant to full charge conditions and is less stressed than other lithium-ion systems if kept at high voltage for a prolonged time. As a trade-off, its lower nominal voltage of 3.2 V / cell reduces the specific energy below that of cobalt-blended lithium-ion.
Lithium nickel cobalt aluminum oxide (NCA)
Lithium nickel cobalt aluminum oxide battery, or NCA, has been around since 1999 for special applications. It shares similarities with NMC by offering high specific energy, reasonably good specific power and a long-life span. However, challenges exist in safety and cost.
Anode materials
Vast majority of lithium-ion batteries use graphite powder as an anode material. Graphite anodes meet the voltage requirements of most common li-ion cathodes, are relatively affordable, extremely light, porous and durable. There are however other contenders for anode, the most prominent being silicon and lithium titanate.
Lithium-titanate (LTO)
In this chemistry, lithium-titanate (LTO) replaces the graphite in the anode of a typical lithium-ion battery. The cathode can be lithium manganese oxide or NMC. Cells with LTO as the anode have a nominal cell voltage of 2.40 V, can be fast charged and deliver a high discharge current. It has excellent low-temperature discharge characteristics and obtains a capacity of 80 percent at –30°C (–22°F). However, batteries of this chemistry are far more expensive than the NMC or LFP batteries, making them viable only for select applications as of 2019.[1]
Electrolyte solution
Commonly used electrolyte comprises lithium salt, such as LiPF6 (Lithium hexafluorophosphate) in an organic solvent which comprises mainly of organic carbonates.
Separator
Two prominent separator categories are:
- Polymer separators – Polyethylene (PE) and tri-layer polyethylene/polypropylene (PP) with the polyethylene sandwiched between the polypropylene layers (PP-PE-PP).
- Ceramic-coated separators
Other emerging lithium-based batteries
The other emerging battery technologies in the li-ion batteries include Li-air and Li-S batteries.
Li-air batteries
The lithium air battery, also known as lithium oxygen battery refers to the type of battery which utilizes the lithium oxidation reaction to produce electricity. The lithium air battery combines the features of both lithium and oxygen, thereby possessing nearly 5 to 15 times of specific energy and almost three times of power compared to the traditional Li-ion batteries.
Lithium–sulfur (Li-S) batteries have high energy density and reasonable costs from the use of sulfur. Currently the best Li-S batteries offer specific energies on the order of 350 Wh/kg, significantly better than most traditional lithium-ion batteries. The key challenge with Li-S battery is the loss of active material due to the formation of several side products leading to low cycle life. With the use of sulfur alloys, higher cycle life can be obtained.
In spite of the advances in other lithium-based batteries, the lithium-ion battery is expected to remain the technology of choice for the next decade. Other technology options mentioned above are expected to become available only around 2030 or later.
[1] https://batteryuniversity.com/learn/article/types_of_lithium_ion
Lead acid vs. Li-ion batteries for EVs and solar power plants – a comparison
Lead acid vs. Li-ion: electric vehicles
The following table provides a quick overview of the types of batteries used for different types of electric vehicles, for countries in different economic categories.
Table 1: Battery types in EVs across regions
| Economy type | Vehicle type | |||
| 2-wheeler | 3-wheeler | 4-wheeler | HCV | |
| Developed(Eg: USA) | Li-ion | Li-ion | Li-ion | Li-ion |
| Developing(Eg: India) | Li-ion and lead acid | Li-ion and lead acid | Li-ion | Li-ion |
| Under-developed (Eg: Somalia) | Lead acid | Lead acid | Li-ion | Li-ion[1] |
The above table shows how currently, both lead acid and L-ion batteries are used in the e-mobility sector worldwide. While the developed economies have mostly moved to i-ion batteries, developing economies (including India) and underdeveloped economies still use lead acid batteries to a considerable extent.
Lead acid vs. Li-ion: solar power
The following table provides a quick overview of the types of batteries used for different types of solar power plants, for countries in different economic categories.
Table 2: Battery types in solar power plants across regions
| Economy type | Type of solar power plant | ||
| Off-grid | Rooftop | Ground-mounted | |
| Developed(Eg: USA) | Li-ion | Li-ion | Li-ion |
| Developing(Eg: India) | Lead acid | Lead acid | NA |
| Under-developed (Eg: Somalia) | Lead acid | Lead acid | NA |
The above table shows how currently, both lead acid and L-ion batteries are used in the solar power sector worldwide. While the developed economies have mostly moved to Li-ion batteries, developing economies (including India) and underdeveloped economies still use lead acid batteries to a considerable extent.
Table 3: Expected trends for battery use in electric vehicles and solar power (2020-2025)[2]
| Parameter | E-mobility | Solar power | ||
| Lead acid | Li-ion | Lead acid | Li-ion | |
| Key comparative advantages & disadvantages – 2020 | · Low cost· Reliability· Recycling potential | · High energy density & lightweight· Long life | · Low cost· Reliability· Recycling potential | · Long life |
| Key comparative advantages & disadvantages – 2025 | · Recycling potential | · High energy density & lightweight· Fast charging times· Long life | · Recycling potential | · Long life· Fast charging times |
| Current applications – 2020 | · Mainly for smaller vehicles· Mainly in developing and under-developed economies | · Both for smaller and larger vehicles in developed economies· Mainly for larger vehicles in developing economies | · Used as the dominant energy storage technology both for rooftop and ground-mounted solar power projects worldwide | · Used in small scale rooftop solar power projects in developed economies· Starting to get used in select large-scale ground mounted solar power plants in developed economies |
| Expected applications by 2025 | · Likely to be used only for small vehicles in under-developed countries | · Expected to dominate across all vehicle types in most regions of the world | · Expected to be used in many rooftop solar systems in under-developed economies.· Will still dominate in large-scale ground-mounted solar power plants in developing and under-developed economies | · Expected to completely dominate both rooftop and ground-mounted solar power systems in most of the developed and developing economies |
Key takeaways
Thus far, the use of batteries has been mainly in stationary and conventional applications. From now on, we can expect significant battery utilizations in emerging end uses, especially in e-mobility and solar power systems.
While currently both lead acid and Li-ion batteries are used in both solar power and electric vehicles, one can expect Li-ion batteries to play a more dominant role in both these sectors in the near future.
That said however, do not expect the lead acid batteries to fade away into oblivion. At EV Next, we expect that the lead acid batteries for ESS have at least a 10 year time window (until about 2030) where their presence will still be felt. Significant declines for lead acid battery use in ESS sectors in India can be expected only close to, or post, 2030.
[2] EAI data and analyses
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References
And here’s an interesting article in Forbes in this regard: Link
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