As lithium-ion batteries are now found everywhere, from your mobile phone to your electric car, this article will show the 10 key differences between the two technologies.
It will also demonstrate how lithium-ion batteries are taking over the century-old lead-acid technology.
Lead-Acid Vs. Lithium-Ion: How Do They Work?
Lead-acid and lithium-ion batteries share the same working principle based on electrochemistry. They store (charge) and release (discharge) electrons (electricity) through electrochemical reactions.
Both of them feature the following parts:
- Two electrodes: Anode (-), Cathode (+)
- Membrane separator
They differ in the material used for each component:
|Cathode||PbO2||Lithium Oxide (LiFePO4, LiCoO2, LiMn2O4, etc…)|
|Electrolyte||H2SO4 (liquid, gel)||Lithium salt (liquid, solid, gel)|
Below is a schematic representation of the working principle of a lithium battery during discharging and charging. The same applies to lead-acid:
While discharging, Lithium ions (Li+) are exchanged between the negative electrode (anode) and the positive electrode (cathode). To balance the reaction, electrons are released from the negative electrode to the positive electrode.
While charging, the opposite reaction occurs, and electrons are flowing from the positive electrode to the negative.
For lead-acid, similar reactions occur, but in this instance, it is the acid electrolyte (H2SO4) that
participates in the reaction with 2H+(aqueous protons).
Lead-Acid Vs Lithium-Ion: Which One Has The Best Capacity?
From a microscopic point of view, the capacity of a battery is related to the global charge of the transferred ions (Li+ or H+), multiplied by the working voltage of the electrochemical reaction.
Here we have the main difference between Lead-Acid and Lithium-Ion – weight. Lithium is the lightest metal on earth, one kg of lithium contains 29 times more atoms than lead. In addition, the working voltage of Lithium-Ion is 3.2V vs 2V for lead-acid. Consequently, you can store much more energy in 1kg of lithium battery than in lead-acid.
The chart below summarizes the energy storage capacity of both technologies. The theoretical density does not take into account the mass of the electrolytes and other components (battery casing, safety equipment…).
|Storage capacity theory||167 Wh/kg||11’600 Wh/kg|
|Storage capacity practice||30 – 40 Wh/kg||110 – 250 Wh/kg|
Two other interesting figures are the battery compacity, also called energy density in Wh/l and the specific power of the battery in W/kg.
|Energy density||80-90 Wh/l||250 – 670 Wh/l|
|Specific power||180 W/kg||250 – 340 W/kg|
In the end, Lithium-Ion batteries are lighter (up to 6 times for the same capacity) than lead-acid, more compact, and up to two times more powerful.
Lead-Acid Vs Lithium-Ion: Can You Fully Discharge?
Maximum Depth Of Discharge
If you’ve already purchased a lead-acid battery, you might have noticed that the manufacturer advises not to discharge the battery below 50% of its full capacity to improve its life duration. In lead-acid batteries, over-discharging creates parasite reactions (sulfation) at the electrodes, slowly damaging the system.
Researchers and engineers worked hard on this matter and introduced the GEL and AGM batteries. Both of them offer a better depth of discharge (DOD) than the traditional flooded lead-acid battery but are still affected if fully discharged.
Conversely, degradations in lithium batteries only start when the depth of discharge reaches 60%, therefore manufacturers recommend 80% DOD to improve their total life duration. Recent improvement enables 100% DOD without extra damage to the battery.
Both technologies, when stored, will slowly lose their initial capacity. The discharge rate is affected by the initial charging state of the battery. It is recommended to fully charge your battery before storing it. For Lead-acid, the self-discharge rate is 3-20% a month, and for Lithium-Ion 0.35-2.5% per month.
The charge efficiency reflects the actual quantity of energy effectively stored in the battery. For example, when charging a 1 kWh battery you might use more than 1 kWh, due to internal loss.
For lead-acid technologies, you’ll get around 90% efficiency and for lithium batteries, 95% to 99%.
Lead-Acid Vs. Lithium-Ion: Which Is More Durable?
Durability is one of the most important factors to consider when buying a product.
The same applies to batteries; unfortunately, this is not the strength of Lead-Acid batteries. Over the years, some improvements were made: lead-acid batteries became maintenance-free, and AGM and GEL technologies were introduced that slightly improved their performance.
With only 2 years of good service (when discharged at 50% of its maximum capacity) the life duration is extremely low, especially for a century-old technology. If deeply discharged at each cycle (80% or more), your lead-acid battery will only work well for 350 cycles or one year.
On the other side, lithium batteries have increased their life duration over the last 5 years, and manufacturers are now offering warranties as high as 10,000 cycles or 10 years (70% of initial capacity).
Lead-Acid Vs. Lithium-Ion: Do They Support Quick Charge/Discharge?
Due to technical limitations, lead-acid batteries don’t support quick charge. Their charging time range from 6 to 15 hours and follow a three-step process as outlined below:
- Bulk charge: charging voltage increases steadily to its maximum value and charging current is kept at its maximum value. The battery will reach up to 80% of its full capacity in approximately 6 to 8 hours.
- Absorption charge: Charging voltage is kept at its maximum value, while the current slowly decreases until the battery is charged at 90-95%.
- Float charge: Charging voltage and current decreases to zero, while the battery reaches full charge.
On the other hand, lithium batteries are fit for quick charge. You can charge them to 80% of their full capacity in 1 to 2 hours (depending on the power output of your charger). The remaining 20% will take another 2 to 3 hours. Therefore, you can fully charge a lithium-ion battery in 3 to 5 hours.
Both types of batteries support quick discharge and can provide intense pulses of current (hundreds of amps) if required.
Lead Acid Vs Lithium Ion: Which One Is The Best For Solar Energy?
Solar energy, like all renewables, is intermittent. Therefore, its power output varies depending on the time of the day, and the weather. Passing clouds generate drastic power output modifications that strongly affect the battery charging current. As previously mentioned, lead-acid batteries can be damaged by these occurrences before they follow the three-step process for proper charging.
In addition, their charging time could reach 15 hours, and in most countries, days are shorter than 15 hours, meaning full charge can never be achieved.
On the other hand, intermittent charging does not affect lithium-ion batteries and it can take only a few hours to charge fully. Consequently, they are perfectly fit for solar energy storage.
Lead-Acid Vs Lithium-Ion: Are They Safe?
Lead-acid and lithium-ion both contain hazardous material that could possibly harm the users and the environment.
To make their products safe, manufacturers have developed different strategies summarized in the chart below:
|Lead-acid||Spilling of acidic electrolyte||Electrolyte as a Gel or absorbed on a glass mat (AGM)|
|Release of highly toxic H2S gas||Valve Regulation|
|Battery Management System (BMS)|
Most of the lead-acid batteries available on the market are now Valve Regulated (VRLA) and maintenance-free, therefore safe to use.
Pure lithium is highly flammable when in contact with air. Battery Management Systems (BMS) were developed for safety purposes to monitor each battery cell and make sure that there is no overcharge/discharge.
In the end, both types of batteries are safe to use, but they still need to be handle with caution.
Lead Acid Vs. Lithium Ion: Which One Is Cheaper?
The Levelized Cost of Storage (LCOS) is the best way to compare the cost of different battery technologies. LCOS is expressed in USD/kWh and takes into account all the expenses related to energy storage over the lifespan of a battery.
As batteries are maintenance-free, the only cost would be the price of the battery itself.
Let’s have a look at the example below:
|Lithium-ion 12V, 100Ah||Lead-acid 12V, 100Ah|
|Upfront cost||739.99 USD||174.99 USD|
|Depth of discharge||80%||50%|
|Total number of cycles||(10 years) – 3600 cycles||(2 years) – 700 cycles|
|Total kWh over lifetime||3’456 kWh||420 kWh|
|LCOS||0.214 USD/kWh||0.417 USD/kWh|
At first, the lithium-ion battery (LiFePO4) costs 4 times more than the lead-acid battery. However, it lasts much longer and in the end, has the lowest LCOS. Therefore, over its lifetime the lithium battery is two times cheaper than the lead-acid.
Lead Acid Vs. Lithium Ion: Can You Recycle?
As previously mentioned, both batteries contain hazardous, highly toxic material and should be disposed of properly.
Lead-acid batteries are the most recycled product in the world. The recycling rate reaches almost 100% in the US as nearly all parts (sulfuric acid electrolyte, ABS casing, lead plates) can be recycled. New lead-acid batteries usually contain more than 80% recycled material.
On the other hand, lithium-ion is a new technology and as such, recycling this material still proves to be challenging. However, recent studies show that lithium batteries could be recycled up to 96%. In 2018, 97,000 tons of lithium batteries were recycled and battery recycling is now seen as a source of material as demand rises.
Lead Acid Vs Lithium Ion: Can You DIY?
Lead Acid batteries are sealed and cannot be upgraded or modified.
On the contrary, lithium-ion batteries are modular and you can build your own battery pack at home.
When purchasing a lithium battery, you’re actually buying multiple battery cells that are assembled together – all of which are connected to the Battery Management System (BMS).
All elements constituting the lithium battery pack can be bought individually online.
Manufacturers are selling prismatic lithium battery cells of various capacities (from 10Ah to 300Ah), all rated at 3.2V.
This illustrates the great modularity of lithium batteries.
This is an overwhelming victory for lithium-ion batteries over Lead-acid batteries.
Lithium-ion batteries offer larger capacities, are more durable, lightweight, efficient, and cheaper to use than lead-acid. Furthermore, they are modular and you can build your battery pack at home.
Thanks to the rapid development of electric vehicles, lithium battery prices will continue to drop, making this technology even more attractive in the years to come.