Introduction to Lithium-Ion Batteries
Imagine how many applications in today's world need Lithium-Ion batteries to function and how lithium batteries are integral part of our lives. Many times, we take these batteries for granted, but the world would be a much different and inhospitable place without them.
A "battery" is a general term for an electro-chemical well of power, which stores energy in a chemical form until changing over it into useful electric power needed to run devices used in our everyday lives. A battery can either be a single cell or numerous cells strung together in a series and/or parallel combinations.
Lithium batteries are classified as being either "primary" or "secondary". Lithium primary batteries are normally known as disposable batteries, like a standard alkaline cell, and are not designed for recharging (doing this would create a very dangerous situation).
On the other hand, lithium secondary batteries, more commonly known as Lithium-Ion batteries, are designed so they can be securely re-energized through charging and reused. The ability of a Lithium-Ion battery to be recharged is due to the way that the anode and cathode discharge characteristics in the battery are reversible. This is a little complicated and would require a physics degree to completely understand, so we will not get too deeply involved with it in this article.
For almost all purposes in battery design, the chemical reaction in a battery is not something you need know on a PhD level scale. The most important thing to realize that when a Lithium-Ion battery is appropriately designed and properly charged, it can be re-energized hundreds or even thousands of times in a safe and efficient manner.
A Brief History of Rechargeable Batteries
There are four main types of rechargeable battery chemistries. We will go in each one's history briefly. These battery chemistries are Lead Acid, Nickel Cadmium (Ni-Cd), Nickel Metal Hydride (Ni-MH), and Lithium-Ion.
Lead Acid Batteries
The formal use of lead-acid batteries (Pb/Ac) started in the 1800's. Due to low production costs, minimal raw material prices, superior performance characteristics, and long cycle life, the lead-acid battery has become, to today's date, the most recognized battery chemistry known to man, accounting for more than 40% to 45% of the total battery market, worldwide.
The lead-acid battery has many applications because of low manufacturing costs, high energy density, and an ever-growing market demand. The most widely known use of lead-acid batteries is starting automobiles, trucks, motorcycles, ATV's, etc. Lead acid batteries can also be used as a cheap way of storing massive amounts of electrical power (energy harvesting), needed in the solar and wind renewable energy markets.
NiCad batteries have been around for a while and have been an extremely researched and thoroughly tested battery technology. Nickel-cadmium batteries were invented and patented by Waldemar Jungnerin in 1899 and have been with us ever since.
Ni–Cd batteries are most frequently used in wireless and corded phones, emergency lights, and many other consumer and industrial applications. Ni–Cd batteries have a somewhat low internal resistance and have the potential to supply exceedingly high surge discharge currents. This makes them a popular choice for remote-controlled electric model airplanes, boats, and automobiles. Cordless hand power tools and flash cameras are other common applications.
Due to stricter EU environmental legislation and restriction on nickel and cadmium, NiCad batteries are expected to be gradually taken out of the consumer electronics market in Europe. However, NiCad batteries are expected to retain a strong position on several niche markets such as industrial and energy harvesting applications.
It is important to properly dispose of Ni–Cd batteries due to the toxicity of Nickel and Cadmium.
NiMH batteries are a recent battery technology developed in the early 1990s. NiMH batteries offer the same cell voltage as NiCad batteries at 1.2 VDC, so they can replace NiCad batteries in many applications without any sort of changes or modification being needed to the devices that they are powering.
The same cell voltage as NiCad combined with a higher energy density and better environmental properties are the driving forces and mitigating factors that enabled NiMH batteries to capture almost all the market share from NiCad batteries, in consumer electronics market, over the past decade or two.
Now, we get into the main chemistry covered of this article, Lithium-Ion batteries. Li-Ion batteries have completely dominated and taken over the mobile computer and smartphone battery markets. Although most of the batteries for portable electronics is of the Li-Ion flavor, there is still a market for portable NiMH batteries as a lower cost alternative to Li-Ion batteries.
Lithium-Ion batteries were first introduced onto the world stage in the mid-1990s and very quickly replaced NiMH batteries as the main power source in mobile phones, notebook computers, and other various portable electronic devices. Currently, the use of lithium batteries has spread into a wide array of less expensive consumer products such as smart watches, vape pens, and other small devices.
The term “Lithium-Ion battery” refers to an entire genome of Lithium-Ion battery chemistries, each chemistry with its own unique electrical properties. The differentiating properties of these chemistries has to do mainly with the negative and the positive electrode material and how these materials affect the transfer of Lithium-Ions though the Lithium-Ion battery’s non-aqueous electrolyte.
The chemically reactive energy of the lithium is different between the positive and negative electrode material and the difference between the two governs the available voltage from the battery. During charge and discharge phase of the battery, Lithium-Ions are transported between the two electrodes and electric energy is either absorbed or released, when current flows through the cell.
Lithium-Ion batteries have, by far, become the most common rechargeable batteries for consumer electronic applications due to their high energy densities, moderate to high cell voltages, and low weight when compared to other battery chemistries. They are also predicted to become the staple battery chemistry choice for industrial, transportation, and energy-storage applications.
Although Lithium-Ion batteries are more expensive than their lead acid, NiCad, and NiMh competitors, they are still in a relatively early phase of development and market life in relation to the energy storage industry. Li-Ion batteries have only been on the commercial market for 15 years and there is a lot of time and opportunity for technical development and cost reductions when looking into the future of this chemistry.
Non-Rechargeable Primary Lithium Batteries
It is important to mention that some lithium batteries are not rechargeable. Primary lithium batteries should never be charged - they could explode. If you are not sure if a lithium battery is rechargeable or not, check the battery's spec sheet to make sure!
Primary lithium batteries have been around since the 1970s. They are intended to provide convenient sources of electrical power for portable applications primarily in the industrial and military markets. Lithium primary batteries require little or no maintenance with an extremely long shelf life.
Primary batteries can usually be stored for up to 10 years with extraordinarily little loss of battery capacity. Some lithium primary batteries with specially formulated solid-state electrolyte can be stored for 20 years or more. The shelf-life tolerance at elevated temperatures is surprisingly good and the temperatures can rise to 70°C in some cases.
Two of the most common primary lithium battery chemistries on the market are lithium desulphated (LiFeS2) and lithium manganese dioxide (LiMnO2). Both chemistries have a solid cathode type and are sold mainly as consumer batteries from department stores, gas stations, and supermarkets. Other higher voltage primary non-rechargeable lithium batteries are mainly intended for the industrial market.
Lithium-Ion Battery Types
There are two general groups of rechargeable, secondary Lithium-Ion batteries.
The first group uses metal as the cell’s negative electrode, this type of battery is called a lithium metal battery. In a lithium metal battery, lithium reacts with the electrolyte and, as a result, forms dendrites on the outer surface of the electrode. Under repeated charging cycles, the outer surface of the anode will increase with a correlating increase in its response and thermal sensitivity.
The second type of rechargeable lithium battery is called a Lithium-Ion battery. The Li-Ion battery has a negative terminal whose structure is a carbon-based material that is usually constructed of graphite. The terminal can be another type of alloy or material as long as it permits interrelation through storage of lithium in the terminal structure. This category includes li-po (lithium polymer) batteries.
Lithium-Ion Cell Styles
Button cells are also known as ”coin cells “. As its name implies, button cells resemble a button or coin because their round, small design.
These cells are enclosed in a metal can (case) and they are available in standard sizes that are based on their diameter and thickness. For example, a LI2032 Lithium-Ion cell is 20mm in diameter and 3.2mm in thickness.
Button cells are used to provide a power source for back up memory in applications that do not need much capacity or current. The button cell's compact size makes it perfect for small portable electronic devices or personal consumer and medical devices such as smart watches, hearing aids, wearable medical implants, laser pointing devices, remote car starters, and key FOBs.
Lithium-Ion prismatic cells are named based on their height, width, and length. For example, a standard 103450 Lithium-Ion prismatic cell is 10mm thick, 34mm wide, and 50mm long. The low-profile design and footprint of this cell makes it possible to make a very small battery pack that will fit in portable electronics.
One disadvantage is that this cell type can be very costly to manufacture. In addition, prismatic cells are less efficient in temperature management, have a much shorter cycle life than cylindrical cells, and may exhibit swelling from pressure inside the cell. These cells are frequently found in portable handheld devices like cell phones, tablet computers, and laptops.
Lithium-Ion Polymer cells or "pouch" cells made their way into the battery market in 1995. They are in some ways like the Lithium-Ion prismatic cell, but have a soft, flexible exterior casing. Lithium-Ion Polymer cells are sealed in a flexible pouch, made of foil, which makes it easy to manufacture into a wide variety of sizes and shapes. Pouch cells have the greatest size efficiency of all the types of Lithium-Ion cells, along with a terrific energy density,
One disadvantage is that Lithium-Ion Polymer cells tend to swell and are easily penetrated due to having such a thin wall, foil case. Li-polymer cells are typically and most found in thin and lightweight handheld applications such as cell phones, tablet computers, and small laptops. They are also many times the best choice in portable applications requiring a high discharge current, such as drones and hobby devices.
Curved Lithium-Ion Polymer cells are used frequently in medical devices such as hearing aids. Very large sized Lithium-Ion Polymer cells are used in Energy Storage System (ESS) applications, electric vehicles, and hybrid vehicles.
When you think of a battery, the first thing that probably comes to mind are cylindrical cells, like a standard AA Alkaline battery. Cylindrical cells are the most used type of cells across all chemistries, including Lithium-Ion. Believe it or not, Lead Acid batteries come in cylindrical shape, not just the large rectangular form that we are used to. Cylindrical cells are enclosed in a metal can (usually nickel-plated steel) and are categorized and named based on their diameter and length. The most common Lithium-Ion cylindrical cells are the 18650’s (18mm diameter, 65mm length), the 26650 (26mm diameter, 65mm length), and the 21700’s (21mm diameter, 70mm length).
Cylindrical cells are proportioned symmetrically, have a strong mechanical form, and can be quickly and easily packed. The cylindrical shape helps to reduce and minimize stress and internal pressure within the cell.
When they are assembled into a battery pack, Lithium-Ion cylindrical cells have a higher energy density than button, polymer, and prismatic cells. The cylindrical cell is extremely multipurpose and the preferred choice for multi-cell battery pack configurations and are commonly used in a wide variety of market applications such as medical, military, consumer, industrial, EV and more.
Lithium-Ion Batteries FAQ's
1. How do Lithium-Ion batteries work?
A Lithium-Ion battery is made up of a negative and positive electrode an electrolyte liquid. The negative and positive electrodes are split by a porous separator to let electrolyte through. Each electrode consists of a particle material that lithium can be collected and stored in. Each electrode has porous polymer binders which holds the lithium together and ensures electrical contact.
A Lithium-Ion battery, when fully charged, has almost all lithium collected and stored on the negative electrode. If you connect an external wire or a nickel tab between the positive and negative electrodes, lithium will travel to the outer surface of the negative electrode where a chemical reaction process occurs and produces a Lithium-Ion and an electron.
The Lithium-Ion will then migrate through the electrolyte to the positive electrode, but electrons cannot travel through the electrolyte (like the Lithium-Ion). The electrons will travel through the electrode particles, polymer binder, external wire, and application (in turn, producing electrical current) back to the positive electrode. The Lithium-Ion and electron then chemically recombine through another chemical reaction to store lithium in the positive electrode particles. This entire process occurs in reverse when you apply voltage and a current to charge the battery.
2. What is the strongest Lithium-Ion battery?
LiFePo (Lithium Iron Phosphate) has the longest lasting cycle life, safest chemical makeup, and is tolerant to the deep discharges. There is also Lithium Nickel Manganese Cobalt Oxide that is used in the transportation industry due to its energy density and high capacity.
3. What's the typical life of Lithium-Ion battery?
The typical life of a Lithium-Ion battery is defined by its cycle life. The cycle life of a battery depends on several factors, some of which are:
- Temperature of battery in storage and in use
- Charging level (SoC)
- Depth of discharge (DoD)
- Rate of the current in charge / discharge
- Battery chemistry type and typical storage conditions
Under normal conditions that are specified on the spec sheet; and, when the discharge cycle is from fully charged condition to 80% DoD (Depth of Discharge), the Li ion battery has a projected cycle life of about 1000 — 1500 cycles.
You can extend the cycle life of the battery by opting for lower DoD by charging after 30– 40 % DoD and keeping the battery with its recommended temperature range.4. How dangerous are Lithium-Ion batteries?
If you do not abuse them, they are extremely safe.
The main concern with Lithium-Ion cells is their high energy density. There is a tremendous amount of energy in a small space, and it can be released quickly.
Lithium-Ion cells have internal resistance, so if you draw too much current from them too quickly, they cell will get hot. If they get too warm, they may vent hot electrolyte, lithium, and vapor. If the internal structures of the Lithium-Ion cell break down and collapse, the remaining energy will be released immediately, and you will get a boom!
Buy high quality cells to minimize the chance of “rapid disassembly” and catastrophic failure. Be 100% sure that you do not short circuit Lithium-Ion cells. Do not batteries in your pockets or store with loose change and keys.
Do not over charge – the cell will get hot, and damage will result. Also, they do not like being over discharged and damage will occur if this happens.
Applications and electronic devices using these cells should have battery management systems (BMS) to prevent over charge and discharge. If the cells are removable, they should be charged with the appropriate charging device.
5. Why do they use lithium for batteries?
Lithium is the lightest metal on the period table of elements. It has the highest energy density among the other metals.
Being situated as the first metal in the periodic table, it is the lightest metal. A battery built using lithium weighs significantly less compared to rechargeable batteries that use Lead, Cadmium or Nickel. Lithium batteries have higher Gravimetric Energy Density (i.e., Watt-hours per kg) than all other chemistries.
With the highest electro-chemical potential, Lithium batteries produce the highest the voltage among other battery types.
The combination of these batteries being light and having a high energy density make the use of Lithium-Ion batteries an attractive battery chemistry.6. What's the difference between a Lithium-Ion battery and a regular battery?
For the average consumer, both regular (say AA or AAA) alkaline batteries and Li-Ion appear the same, function the same, etc.
The main differences between alkaline and lithium batteries are both in performance and safety.
For example, an alkaline AA cell on average is around 1.5 V / 2,000mAh. An Energizer lithium cell at the same voltage has 3,000mAh. Much more energy can be stored in a lithium battery.
Because of the increased energy density, lithium cells can explode or vent if they are abused or rapidly discharged.7. What is the best Lithium-Ion battery?
Lithium-Ion batteries come in a wide variety of types, sizes, and voltages. They also have a diverse range of uses. Some Lithium-Ion batteries are better matched to particular application than other types are. Most importantly, choose the lithium battery best suited for the specific task at hand.
It’s also important to note that the Lithium-Ion battery industry is constantly changing and evolving. Companies and scientists around the world are creating new batteries to either work alongside Lithium-Ion batteries or replace them. At the same time, they are working on making lithium batteries more efficient and safer. As these new batteries develop and Lithium-Ion batteries become more refined, it will be interesting to watch which batteries will come to the forefront.8. Do Lithium-Ion batteries cause cancer?
Lithium-Ion batteries and cancer have not been correlated at all. Some people may be sensitive to handling lithium batteries because of the nickel and chrome, but its more an allergy thing than anything else. During their use, Lithium-Ion batteries will be inside the application - the only time you might have to encounter one is when you must replace it.
Lithium-Ion batteries do not release any type of radiation or fumes. If the “can” on cylindrical cells is not damaged or the aluminum foil material is not damaged on a pouch cell, they are safe. If the battery gets damaged enough to leak, the biggest problem is that lithium is a highly reactive metal and could create a fire if exposed to water. Also, the resulting lithium compound from lithium mixed water is caustic.
9. What is the shelf life of a Lithium-Ion battery that is in storage?
The shelf life of 3-6 years for Lithium-ion batteries. Depending on the type of Lithium-Ion battery, loss of capacity (self-discharge), occurs at a rate around 2% to 5% each month.
Store the lithium-ion batteries in a cool, dry, and temperature-controlled place to help minimize the rate of self-discharge. Also, make sure that there is no potential for the battery to short with other batteries in storage by keeping them tightly packed in a box or individually bagging.
10. Are all Lithium-Ion cells rechargeable?
All Lithium-Ion batteries are rechargeable since they are secondary (rechargeable) cells.
There are lithium primary cells which should never be recharged and are made for one time use only. Do not charge these types of cells since it is extremely dangerous to do so. This is important, so I will say it again - never attempt to recharge primary lithium cells; as a result, they will overheat, expand, and explode.
If you are not sure whether the lithium cell is rechargeable or not, refer to the spec sheet on the manufacturer’s website.
11. Is there any battery technology better than Lithium-Ion?
Right now, it looks like Lithium-Ion batteries are the best and most cost-effective battery chemistry.
There is a potential chemistry that could rival Lithium-Ion that called a metal-air battery. Metal-air batteries (MABs), that have certain theoretical and perceived advantages over Lithium-Ion batteries such as a lower overall cost and a higher energy density.
One MAB chemistry is the iron-air battery. It could be a great alternative for replacing Lithium-Ion batteries in the electric vehicle market due to its lower cost and higher energy density when compared to Lithium-Ion batteries. Tesla is extremely interested in iron-air batteries and are actively researching this chemistry. If they are considered to become a viable replacement in the EV market remains to be seen since Lithium-Ion batteries are still being refined and improved upon.
12. How were Lithium-Ion cells developed?
Surprisingly, a consumer electronics company developed and commercialized Lithium-Ion batteries, not a battery manufacturer. Who would have thought? The company is Sony.
In the early 1990’s, Sony needed smaller and lighter batteries for some of their smaller and portable electronic devices. First, they asked their general battery suppliers to develop and build a commercially available battery based on the Li-Ion chemistry. At that point in time, Lithium-Ion batteries had never made it out of R&D at research labs.
The battery manufacturers, prior to being approached by Sony, were going full force on the new chemistry of Nickel Metal Hydride (Ni-MH). These battery manufacturers were only focused on Nickel Metal Hydride and had no time, interest, or resources to research and develop a new Lithium-Ion battery for Sony. Manufacturers were happy with Status Quo of using Ni-MH as the newest form of battery.
As a response, Sony decided that they could be a dominant factor in the market for Lithium-Ion batteries and decided to develop and market these types of batteries for the consumer electronics market. Sony’s first Lithium-Ion battery was developed and released around 1995. Sony was the largest Lithium-Ion battery supplier for quite some time until the rest of the battery industry finally caught up and surpassed them in sales13. How do you tell if a Lithium-Ion battery is bad?
Below are four ways that you can tell if a Lithium-Ion battery is no good.
- Find the manufacturing date code on the side of the battery. Any Lithium-Ion battery 8 years or older will no longer be able to hold a charge and will discharge completely to the cutoff voltage in a short amount of time.
- You can determine the internal resistance (measured on Ohms) of the Lithium-Ion cell by using a Kelvin's double bridge. An old Lithium-Ion cell will have a higher internal resistance than a “fresh” cell. The best way to find the acceptable internal resistance value is to refer to the manufacturer’s specification sheet for that Lithium-Ion cell.
- Evaluate the run time by putting a small load across the battery with a 1W LED or similar component and compare it to the run time of a “fresh” cell. Run time can also be determined using the formula T = 10 * a / w (where (T) is the time, (a) is the amp hours (battery capacity) and (w) is the power output / usage). If the battery does not come within 25% of the run time after being fully charged, it can be considered end of life.
- Look for unusual heating issues when charging and discharging. If the battery gets hot, the internal resistance of the battery is beyond what is acceptable, and the battery can be viewed as no good. It is OK for the battery to get slightly warm, and this is normal.
14. What is the main difference between a primary lithium battery and a Lithium-Ion battery?
The main difference between a primary Lithium battery and Lithium-Ion battery is that a primary Lithium battery is a single cell construction. Lithium primary cells are single-use and cannot be recharged. Just the opposite for Lithium-Ion cells, they are secondary and can be recharged. Lithium-ion batteries can be charged and discharged hundreds or thousands of times.
Primary Lithium batteries have an exceedingly long shelf life. A lithium primary battery can last for 10 to 12 years and retain most of its capacity. Lithium-ion batteries completely self-discharge on the shelf after 2 to 3 years.
Although Lithium-Ion batteries might seem much better alternate than Lithium primary cells because of the ability to recharge, there are still some features that make primary Lithium batteries extremely useful in the battery world.
Primary Lithium batteries have a much higher energy density than lithium-ion batteries. This means they hold more capacity in comparison to Lithium-Ion batteries for their size. Additionally, primary Lithium batteries are less expensive and easier to manufacture than Lithium-Ion batteries.
Unfortunately, you cannot safely or effectively recharge primary Lithium batteries, but that is why Lithium-Ion batteries were developed and marketed in the first place.
15. What is the difference between Lithium-Ion and LiPo/Lithium Polymer?
Lithium-Ion has a much higher energy density (i.e., more energy for the same weight and size), longer cycle life (charge and discharge cycles) and are less costly to manufacture than LiPo/Lithium polymer batteries.
LiPo/Lithium polymer batteries are much safer because they are not as sensitive to overcharging, are very easily shaped to different forms, and they can run at remarkably high discharge rates safely.
Most will agree that Li-Ion is more widely used, but LiPo/Lithium Polymer batteries are still popular in the RC market, where a high rate of discharge is needed.