Before knowing the power capacity of any battery, having an understanding of its energy density is highly important. A battery with a higher energy density tends to run for a longer period of time than any other battery.
Batteries like lithium-ion batteries are now moving towards an increase in energy density. This is because increasing the density can highly increase the battery’s voltage capacity and discharge rate.
However, there are some requirements and goals to improve energy density. What are these? Let’s have a detailed look at them below.
What Is Energy Density in Batteries?
People often confuse energy density with the term power density. But, both are different terms used for different measurements. For instance, power density is the measure of energy efficiency of a battery while energy density is the energy measured in response to its weight.
To measure how quickly energy can be delivered from one cell to another, you can use the term power density. Whereas, energy density corresponds to the amount of energy a battery contains in accordance with its weight.
Moreover, how you measure the energy density of lithium-ion battery is simple and is done in watt-hours per kilogram or simply symbolized as Wh/kg. It is also the unit of electrical energy which indicates how much energy is consumed per hour in a watt.
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What Is the Energy Density of Lithium-ion Battery?
At this point, you clearly know what it means by measuring the energy density of a cell or a battery. But, how can you measure the energy of the lithium-ion battery is still under question. Well, energy density is generally divided into two sections:
I. Weight energy density
II. Volume energy density
The amount of energy a battery contains is a highly important characteristic of any battery and is necessary to measure its run time. For lithium-ion batteries, the energy density ranges between 50-260 Wh/kg which is comparatively in between the density range of other batteries.
How to Calculate Lithium-ion Battery Energy Density?
Generally, there are two ways to determine the energy density of a battery. One is the gravimetric energy measurement and the other is the volumetric energy measurement. Both these measurements are taken in the standard unit of Wh/kg and thus equal to one watt and one hour of consumption.
To calculate the energy density of the lithium-ion battery, different formulas are used. The standard and simple formula of calculations are as follows:
● Nominal Battery Voltage (V) x Rated Battery Capacity (Ah) / Battery Weight (kg) = Specific Energy or Energy Density (Wh / kg).
From this measurement, we can easily calculate the energy density of lithium-ion batteries if we know the values of nominal voltage, battery capacity, and weight of the cell. Besides, here are two other formulas for calculating the energy density of a lithium-ion battery:
● Energy density (Wh/L) = battery capacity ×discharge platform voltage/ volume
● Battery weight Energy density = battery capacity × discharge platform/ weight
The first one involves the Wh/L as a standard unit of calculation while the second one has Wh/kg as the standard unit. Both formulas are vital in calculating the amount of energy in lithium-ion batteries.
If one wishes to calculate the energy density of lithium-ion batteries at different intervals, he can use the following formula for different time periods:
● For Daily Power Consumption
Daily Power Consumption = Wattage rating x time in hours. 2000 Watts x 3 Hrs = 6000 Watts-Hour.
● For Monthly Power Consumption
Monthly Power Consumption = Wattage rating x time in hours. 2000 Watts x 3 Hrs x 30 days = 180000 Watts-Hour
Moreover, to calculate the energy density in joules, you can multiply the number of watts by the number of seconds as (60 watts) x (120 seconds) = 7200 Joules.
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Power Density vs Energy Density: What’s the Difference?
As mentioned earlier, both power density and energy density are entirely different terms and have their own usage in different battery cells. Power density simply refers to how quickly a battery can deliver the energy or the efficiency of a cell.
On the other hand, energy density is the measure of the amount of energy posses by a battery in response to its weight. To understand it better, here are some major differential points between the two:
● Power density is not an important metric for calculating the runtime of a battery. On the other hand, energy density measures how much time your battery can last.
● To measure the battery performance, its weight, size, and dimensions, energy density is widely applicable other than the power density.
● The lifespan of a battery totally measured by the energy density and not by the power density.
Energy Density Comparison: What Battery has the Highest Energy Density?
When it comes to determining the energy density of different cell batteries, you have to be very careful as all the cells have different density ranges. Therefore, the best way to know which cell has the highest energy density is by looking at its internal chemistry.
We have discussed the energy density of lithium-ion batteries. But, is this the maximum amount of energy a battery has? No, here is a list of some other popular battery cells that show different energy ranges:-
➔ The lead acid battery has an energy density in the range of 30-50 Wh/kg
➔ Nickel-cadmium battery has an energy density in the range of 45-80 Wh/kg
➔ Nickel-metal hydride battery has an energy density in the range of 60-120 Wh/kg
➔ The lithium-ion battery has an energy density in the range of 50-260 Wh/kg
The table shows the energy density variations of different battery types:
| Battery Type | Cost $ per Wh | Wh/kg | Wh/liter |
| Lead-acid | $0.17 | 41 | 100 |
| Alkaline long-life | $0.19 | 110 | 320 |
| Carbon-zinc | $0.31 | 36 | 92 |
| NiMH | $0.99 | 95 | 300 |
| NiCad | $1.50 | 39 | 140 |
| Lithium-ion | $0.47 | 128 | 230 |
From here, it is clearly understood that lithium-ion batteries have the maximum energy density and thus possess a large amount of energy than any other battery on the market. However, it also shows some variations.
As you know, lithium-ion batteries further consist of a group of smaller cells in their composition which helps in increasing the battery’s performance. These battery types have different electrolytes in their solution.
Some have graphite as cathode while other has aluminium so they contain different energy density. Let’s have a look at the energy densities of different battery types of lithium-ion.
1. Lithium Titanate (LTO) Batteries
One of the widely used lithium-ion batteries as industry titans are lithium titanate(LTO) batteries. Although these are oldest in nature and composition yet have an energy density of 50 to 80 Wh/kg.
In LTO battery-type of lithium cells, lithium titanate is used as an anode in place of carbon which permits a quick entry and exit of electrons in the cells. Although their energy density is comparatively low than other lithium-ion cells, they are used in medical devices and vehicles.
2. Lithium Cobalt Oxide (LCO) Batteries
Unlike lithium titanate batteries, lithium cobalt oxide batteries have higher energy density and thus form the basis of cell phones, laptops and other electric vehicles. The amount of energy they carry ranges from 150 to 200 Wh/kg.
Due to the high energy of these battery types of lithium, they are expensive and need high maintenance than any other battery cells. Moreover, LCO batteries use cobalt oxide as a typical cathode which is a very dense and volatile material. Thus, these batteries have a higher risk of overheating and are sensitive to higher temperature ranges.
3. Lithium Nickel Manganese Cobalt Oxide (NMC) Batteries
Just like LCO batteries, this battery type of lithium use cobalt as a cathode in its composition. Besides cobalt, they also have nickel and manganese which helps in increasing the stability of the battery cells. With that, NMC batteries have a battery energy density of 150 to 220 Wh/kg.
The wide use of NMC battery types is in electric vehicles but they are also a major part of medical devices and e-bikes. Their high battery energy density and manufacturing capability have made them the stable and most popular lithium-ion batteries in the market.
Unlike LCO batteries, Nickel manganese cobalt batteries are not sensitive to high temperatures. Thus, they can easily handle high temperature and pressure ranges as well.
4. Lithium Iron Phosphate (LFP) Batteries
One of the most adorable, safe, and reliable batteries in the industry is the Lithium iron phosphate (LFP) battery. They have a high energy density of 90 to 160 Wh/kg, which is lower than cobalt batteries but is still more than some other popular battery types of lithium.
Moreover, the graphite electrode and the metallic backing of the anode in LFP batteries made them inexpensive, non-toxic, and ideal batteries for heavy equipment. The plus point is LiFePo4 is a natural organic mineral and thus is highly reliable as compared to lead acid batteries.
To illustrate the difference and comparison of energy density between the different energy types of lithium-ion cells, have a look at the chart below:
| Lithium-Ion Battery Type | Energy Density (Wh/kg) | Pros | Cons |
| Lithium Titanate (LTO) | 50-80 | Long life, stable | Low energy density, more expensive |
| Lithium Cobalt Oxide (LCO) | 150-200 | High energy density | Volatile and expensive |
| Lithium Nickel Manganese Cobalt Oxide (NMC) | 150-220 | High energy density | Safer than LCO but still relatively unstable and expensive |
| Lithium Iron Phosphate (LFP) | 90 -160 | Medium-high energy density | Stable, long lasting and higher energy density |
FAQs about Lithium-ion Battery Energy Density
How to Increase the Energy Density of the Battery?
The structure of a battery cell is designed in a way that you can easily improve the manufacturing capabilities of a battery when needed. Thus, if you wish to increase the energy density of the lithium-ion battery, you should focus on the following two factors:
I. Increasing the Battery Size
By increasing the size or dimensions of a battery, you can easily improve the battery’s performance. By changing the original battery size, you can easily improve the energy density to a larger scale.
Ii. Modifying the Chemical Composition
The composition of a battery also matters a lot. Changing the electrolyte composition can also enhance the battery capacity. You can do this by upgrading the positive and negative electrodes of your battery and modifying them with strong material.
What is the Difference Between Power Density and Energy Density?
Power density is the measure of energy efficiency of a battery while energy density is the energy measured in response to its weight. Hence, both are two different terms and have a major role in determining the power capacity and lifespan of a battery.
To measure how quickly energy can be delivered from one cell to another, you can use the term power density. Whereas, energy density corresponds to the amount of energy a battery contains in accordance with its weight.
What is the Difference in Energy Density Between Gasoline and Lithium-ion Batteries?
As far as the battery energy density of Gasoline and Lithium-ion batteries is concerned gasoline has 100 times more energy density than any other battery. As we know, a lithium-ion battery has an energy density of around 0.3MJ/Litre while gasoline has an energy density of 13KWh/kg. This is the reason why gasoline is widely used in fully fueled cars and vehicles.
Do Lithium-ion Batteries Have a Higher Energy Density than Lead-acid Batteries?
Although lead-acid batteries are of wide importance among the popular rechargeable batteries in terms of energy density, they stand low in the chart. With an energy density range of 30 to 50 Wh/kg, lead-acid batteries lag behind lithium-ion batteries’ energy density range of 50 to 260 Wh/kg.
Moreover, lithium-ion batteries consist of smaller cell types with different energy ranges and thus they are thermally more stable. This high energy density makes them the ideal battery type to be used in power backups, UPS, and electronic goods. Moreover, they are the first choice of the automotive sector and automobile electronics.
Final Verdict
Now, you have clearly understood the energy density of lithium-ion batteries and how you can measure them. However, make sure to check the electrolyte composition and the weight of the battery before doing a final purchase. In this way, you will be able to increase the battery capacity and overall performance over time.
