The introduction of lithium batteries has been one of the most critical steps in the evolution of battery technology. Lithium batteries provide the opportunity to replace big bulky, leaky lead-acid batteries with compact Li-ion battery systems with significantly better capacity.
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The lithium-ion battery industry has dominated over traditional options, such as lead-acid batteries. In fact, lithium battery technology is so popular that many different types of lithium batteries are available on the market for all applications and needs.
In this article, we will compare different types of lithium batteries, their advantages, disadvantages, and uses.
What is a Lithium Battery?
Lithium batteries are rechargeable batteries that create electric current due to the movement of lithium ions between the cathode material (negative electrode) and the anode material (positive electrode).
The materials used in a lithium-ion battery are lithium-based compounds for the anode and usually a graphite carbon cathode. The electrodes are separated by an electrolyte which varies based on the particular type of lithium battery technology.
The lithium ions move from the cathode to the anode during the charging process. During discharging of the lithium-ion battery, the lithium ions move from the anode to the cathode.
What Are the Different Types of Lithium Batteries?
Lithium-ion battery types differ based on the lithium compound used in the anode electrode. There are six different types of lithium batteries:
LFP batteries have Lithium Ferrous Phosphate (LiFePO4) as the anode material, and this is one of the most widely adopted battery technologies nowadays. The anode is made of Lithium Iron Phosphate, one of the most stable and non-toxic lithium compounds.
It results in greater thermal stability in fully charged conditions. Whereas other lithium-ion battery types tend to exhibit thermal runaway in these conditions.
A Lithium Cobalt Oxide battery contains a Lithium Cobalt Oxide cathode and a graphite carbon anode. The unique selling point of lithium cobalt oxide batteries is their high energy density, which makes them the best choice for some particular applications with this requirement.
LCO batteries have a significantly low specific power. This means there is a limitation to their load capability, making them unsuitable for applications such as electric vehicles.
In LMO batteries, the cathode is made of Lithium Manganese Oxide (LiMn2O4). This results in a three-dimensional spinel structure, enabling a better movement of lithium ions. This structure also makes it thermally more stable and safer. But it lowers the life span of the battery.
Lithium manganese oxide batteries have design flexibility and can be modified by adding other materials to improve their chemical properties. The specific energy of these batteries is low.
Li-NMC batteries are second only to LFP batteries. These batteries contain a cathode made of Nickel Manganese Cobalt Oxide (LiNiMnCoO2). Due to the presence of Manganese and Cobalt, Lithium Nickel Manganese Cobalt batteries offer the best benefits of LMO and LCO batteries.
The two common ratios of nickel, cobalt, and manganese are 1:1:1 or 5:3:2. Cobalt, being a rare element, is the major driving factor in the cost of these batteries.
LTO batteries are different from the other lithium-ion batteries mentioned previously. These batteries use Lithium Titanate (Li2TiO3) as the anode material instead of a graphite anode. The cathode materials are Li-NMC or Lithium Manganese Oxide.
NCA batteries replace the Manganese in NMC batteries with Aluminium. Due to the similar materials used and cell construction, NCA and NMC batteries share some common features. The addition of Aluminium to Lithium Nickel Cobalt Oxide adds the element of chemical stability to an NCA battery.
Cell Form Classification of Lithium Ion Batteries
Besides the classification based on electrode materials, there is another way to classify lithium-ion battery systems. There are three types of lithium-ion batteries based on this classification:
These are the most widely used commercial lithium-ion cells. They form the batteries used in toys, medical devices, gadgets, and more. Cylindrical lithium-ion battery cells differ from conventional batteries, as the former are rechargeable lithium batteries with a higher capacity.
This type of cell features sealed electrodes and electrolytes in a protective cylindrical metal can. A cylindrical lithium-ion battery offers excellent safety and the best protection against thermal elements. Cylindrical Li-ion batteries are also the cheapest ones to manufacture.
Unlike a cylindrical or prismatic cell, a lithium pouch cell is physically flexible. The battery cell is sealed in flexible foil or plastic film for protection. A lithium pouch cell is very lightweight and can be made into batteries of any shape or size. These batteries are used in drones, RC vehicles, jump starters, etc.
Pouch cells tend to swell when used. Therefore, when integrating these cells into any application, it is important to allocate extra space to account for the swelling of the cell.
Prismatic cells are cubic lithium batteries that contain electrode sheets and separators in a sturdy plastic housing. Prismatic cells are made in a single-row or two-row module of four cells, with arrestors having the same polarity. Prismatic cells are more expensive batteries than cylindrical cells but provide much greater storage.
Lithium batteries in cell phones and laptops are all prismatic energy cell batteries. While lightweight and thin, these batteries are prone to heating due to the metal casing used.
How Do Different Types of Lithium-ion Batteries Compare?
The table below gives an overview of the comparison between different types of lithium-ion batteries:
There are many different types of lithium-ion batteries, and as is evident from the information above, lithium batteries vary drastically in terms of their characteristics. This makes different lithium-ion batteries suitable for different purposes and requirements.
Even among any particular lithium-ion battery type, the properties of the battery can vary significantly among different battery manufacturers.
For instance, while most lithium iron phosphate batteries last for about five to six years, LiFePO4 batteries from Eco Tree Lithium last at least eight to ten years. The manufacturer provides a six-year warranty policy so that you know your battery will last at least that long.
Eco Tree Lithium&#;s LFP batteries also come with an integrated Battery Management System (BMS). This system provides protection from elements such as overcharging, overheating, operation in cold temperatures, etc.
Frequently Asked Questions
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Here are the answers to some commonly asked questions regarding lithium batteries:
Are all lithium batteries the same?
No, all lithium batteries are not the same. In fact, the difference between two lithium-ion batteries can be that of night and day due to their technological complexity. The characteristics of a lithium-ion battery depend on the particular lithium-based compound used at the electrodes.
How many different types of cells are used for lithium batteries?
Based on electrode materials, there are six different types of lithium cells: LFP, NMC, LCO, NCA, LTO, and LMO. Based on the cell shape, there are three types of lithium-ion batteries- cylindrical, pouch, and prismatic, each with distinct battery performance parameters.
Which type of lithium battery is safest?
Lithium iron phosphate batteries (LFP batteries) are the safest among current lithium-ion batteries on the market. LFP batteries do not contain toxic substances like cobalt and have excellent thermal and chemical stability characteristics.
Lithium iron phosphate batteries (LFP batteries) are considered to be the safest batteries out there. These batteries do not contain toxic substances like cobalt and have very good thermal and chemical stability.
Lithium-ion is named for its active materials; the words are either written in full or shortened by their chemical symbols. A series of letters and numbers strung together can be hard to remember and even harder to pronounce, and battery chemistries are also identified in abbreviated letters.
For example, lithium cobalt oxide, one of the most common Li-ions, has the chemical symbols LiCoO2 and the abbreviation LCO. For reasons of simplicity, the short form Li-cobalt can also be used for this battery. Cobalt is the main active material that gives this battery character. Other Li-ion chemistries are given similar short-form names. This section lists six of the most common Li-ions. All readings are average estimates at time of writing.
Its high specific energy makes Li-cobalt the popular choice for mobile phones, laptops and digital cameras. The battery consists of a cobalt oxide cathode and a graphite carbon anode. The cathode has a layered structure and during discharge, lithium ions move from the anode to the cathode. The flow reverses on charge. The drawback of Li-cobalt is a relatively short life span, low thermal stability and limited load capabilities (specific power). Figure 1 illustrates the structure.
The drawback of Li-cobalt is a relatively short life span, low thermal stability and limited load capabilities (specific power). Like other cobalt-blended Li-ion, Li-cobalt has a graphite anode that limits the cycle life by a changing solid electrolyte interface (SEI), thickening on the anode and lithium plating while fast charging and charging at low temperature. Newer systems include nickel, manganese and/or aluminum to improve longevity, loading capabilities and cost.
Li-cobalt should not be charged and discharged at a current higher than its C-rating. This means that an cell with 2,400mAh can only be charged and discharged at 2,400mA. Forcing a fast charge or applying a load higher than 2,400mA causes overheating and undue stress. For optimal fast charge, the manufacturer recommends a C-rate of 0.8C or about 2,000mA. (See BU-402: What is C-rate). The mandatory battery protection circuit limits the charge and discharge rate to a safe level of about 1C for the Energy Cell.
The hexagonal spider graphic (Figure 2) summarizes the performance of Li-cobalt in terms of specific energy or capacity that relates to runtime; specific power or the ability to deliver high current; safety; performance at hot and cold temperatures; life span reflecting cycle life and longevity; and cost. Other characteristics of interest not shown in the spider webs are toxicity, fast-charge capabilities, self-discharge and shelf life. (See BU-104c: The Octagon Battery &#; What makes a Battery a Battery).
The Li-cobalt is losing favor to Li-manganese, but especially NMC and NCA because of the high cost of cobalt and improved performance by blending with other active cathode materials. (See description of the NMC and NCA below.)
Li-ion with manganese spinel was first published in the Materials Research Bulletin in . In , Moli Energy commercialized a Li-ion cell with lithium manganese oxide as cathode material. The architecture forms a three-dimensional spinel structure that improves ion flow on the electrode, which results in lower internal resistance and improved current handling. A further advantage of spinel is high thermal stability and enhanced safety, but the cycle and calendar life are limited.
Low internal cell resistance enables fast charging and high-current discharging. In an package, Li-manganese can be discharged at currents of 20&#;30A with moderate heat buildup. It is also possible to apply one-second load pulses of up to 50A. A continuous high load at this current would cause heat buildup and the cell temperature cannot exceed 80°C (176°F). Li-manganese is used for power tools, medical instruments, as well as hybrid and electric vehicles.
Figure 4 illustrates the formation of a three-dimensional crystalline framework on the cathode of a Li-manganese battery. This spinel structure, which is usually composed of diamond shapes connected into a lattice, appears after initial formation.
Li-manganese has a capacity that is roughly one-third lower than Li-cobalt. Design flexibility allows engineers to maximize the battery for either optimal longevity (life span), maximum load current (specific power) or high capacity (specific energy). For example, the long-life version in the cell has a moderate capacity of only 1,100mAh; the high-capacity version is 1,500mAh.
Figure 5 shows the spider web of a typical Li-manganese battery. The characteristics appear marginal but newer designs have improved in terms of specific power, safety and life span. Pure Li-manganese batteries are no longer common today; they may only be used for special applications.
Most Li-manganese batteries blend with lithium nickel manganese cobalt oxide (NMC) to improve the specific energy and prolong the life span. This combination brings out the best in each system, and the LMO (NMC) is chosen for most electric vehicles, such as the Nissan Leaf, Chevy Volt and BMW i3. The LMO part of the battery, which can be about 30 percent, provides high current boost on acceleration; the NMC part gives the long driving range.
Li-ion research gravitates heavily towards combining Li-manganese with cobalt, nickel, manganese and/or aluminum as active cathode material. In some architecture, a small amount of silicon is added to the anode. This provides a 25 percent capacity boost; however, the gain is commonly connected with a shorter cycle life as silicon grows and shrinks with charge and discharge, causing mechanical stress.
These three active metals, as well as the silicon enhancement can conveniently be chosen to enhance the specific energy (capacity), specific power (load capability) or longevity. While consumer batteries go for high capacity, industrial applications require battery systems that have good loading capabilities, deliver a long life and provide safe and dependable service.
One of the most successful Li-ion systems is a cathode combination of nickel-manganese-cobalt (NMC). Similar to Li-manganese, these systems can be tailored to serve as Energy Cells or Power Cells. For example, NMC in an cell for moderate load condition has a capacity of about 2,800mAh and can deliver 4A to 5A; NMC in the same cell optimized for specific power has a capacity of only about 2,000mAh but delivers a continuous discharge current of 20A. A silicon-based anode will go to 4,000mAh and higher but at reduced loading capability and shorter cycle life. Silicon added to graphite has the drawback that the anode grows and shrinks with charge and discharge, making the cell mechanically unstable.
The secret of NMC lies in combining nickel and manganese. An analogy of this is table salt in which the main ingredients, sodium and chloride, are toxic on their own but mixing them serves as seasoning salt and food preserver. 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 offers a low specific energy. Combining the metals enhances each other strengths.
NMC is the battery of choice for power tools, e-bikes and other electric powertrains. The cathode combination is typically one-third nickel, one-third manganese and one-third cobalt, also known as 1-1-1. Cobalt is expensive and in limited supply. Battery manufacturers are reducing the cobalt content with some compromise in performance. A successful combination is NCM532 with 5 parts nickel, 3 parts cobalt and 2 parts manganese. Other combinations are NMC622 and NMC811. Cobalt stabilizes nickel, a high energy active material.
New electrolytes and additives enable charging to 4.4V/cell and higher to boost capacity. Figure 7 demonstrates the characteristics of the NMC.
There is a move towards NMC-blended Li-ion as the system can be built economically and it achieves a good performance. The three active materials of nickel, manganese and cobalt can easily be blended to suit a wide range of applications for automotive and energy storage systems (EES) that need frequent cycling. The NMC family is growing in its diversity.
In , the University of Texas (and other contributors) discovered phosphate as cathode material for rechargeable lithium batteries. Li-phosphate offers 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.
Li-phosphate 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. (See BU-808: How to Prolong Lithium-based Batteries). As a trade-off, its lower nominal voltage of 3.2V/cell reduces the specific energy below that of cobalt-blended lithium-ion. With most batteries, cold temperature reduces performance and elevated storage temperature shortens the service life, and Li-phosphate is no exception. Li-phosphate has a higher self-discharge than other Li-ion batteries, which can cause balancing issues with aging. This can be mitigated by buying high quality cells and/or using sophisticated control electronics, both of which increase the cost of the pack. Cleanliness in manufacturing is of importance for longevity. There is no tolerance for moisture, lest the battery will only deliver 50 cycles. Figure 9 summarizes the attributes of Li-phosphate.
Li-phosphate is often used to replace the lead acid starter battery. Four cells in series produce 12.80V, a similar voltage to six 2V lead acid cells in series. Vehicles charge lead acid to 14.40V (2.40V/cell) and maintain a topping charge. Topping charge is applied to maintain full charge level and prevent sulfation on lead acid batteries.
With four Li-phosphate cells in series, each cell tops at 3.60V, which is the correct full-charge voltage. At this point, the charge should be disconnected but the topping charge continues while driving. Li-phosphate is tolerant to some overcharge; however, keeping the voltage at 14.40V for a prolonged time, as most vehicles do on a long road trip, could stress Li-phosphate. Time will tell how durable Li-Phosphate will be as a lead acid replacement with a regular vehicle charging system. Cold temperature also reduces performance of Li-ion and this could affect the cranking ability in extreme cases.
See Lithium Manganese Iron Phosphate (LMFP) for manganese enhanced L-phosphate.
Lithium nickel cobalt aluminum oxide battery, or NCA, has been around since for special applications. It shares similarities with NMC by offering high specific energy, reasonably good specific power and a long life span. Less flattering are safety and cost. Figure 11 summarizes the six key characteristics. NCA is a further development of lithium nickel oxide; adding aluminum gives the chemistry greater stability.
Batteries with lithium titanate anodes have been known since the s. Li-titanate replaces the graphite in the anode of a typical lithium-ion battery and the material forms into a spinel structure. The cathode can be lithium manganese oxide or NMC. Li-titanate has a nominal cell voltage of 2.40V, can be fast charged and delivers a high discharge current of 10C, or 10 times the rated capacity. The cycle count is said to be higher than that of a regular Li-ion. Li-titanate is safe, has excellent low-temperature discharge characteristics and obtains a capacity of 80 percent at &#;30°C (&#;22°F).
LTO (commonly Li4Ti5O12) has advantages over the conventional cobalt-blended Li-ion with graphite anode by attaining zero-strain property, no SEI film formation and no lithium plating when fast charging and charging at low temperature. Thermal stability under high temperature is also better than other Li-ion systems; however, the battery is expensive. At only 65Wh/kg, the specific energy is low, rivalling that of NiCd. Li-titanate charges to 2.80V/cell, and the end of discharge is 1.80V/cell. Figure 13 illustrates the characteristics of the Li-titanate battery. Typical uses are electric powertrains, UPS and solar-powered street lighting.
Figure 13: Snapshot of Li-titanate.Figure 15 compares the specific energy of lead-, nickel- and lithium-based systems. While Li-aluminum (NCA) is the clear winner by storing more capacity than other systems, this only applies to specific energy. In terms of specific power and thermal stability, Li-manganese (LMO) and Li-phosphate (LFP) are superior. Li-titanate (LTO) may have low capacity but this chemistry outlives most other batteries in terms of life span and also has the best cold temperature performance. Moving towards the electric powertrain, safety and cycle life will gain dominance over capacity. (LCO stands for Li-cobalt, the original Li-ion.)
Figure 15: Typical specific energy of lead-, nickel- and lithium-based batteries.[1] Source: RWTH, Aachen
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