Week 1 Understanding Different Battery Chemistry

Aim:

The aim of this challenge is to familarise with the variouse EV batteries (With lithium iron cell battery being the best at the moment and the foccus of this course.). Its compositon from Cathode to anode. The difference between the different types on Lithium iron cell battery currently on the market and the advantage over one another.

1.Prepare a table which includes materials & chemical reactions occurring at the anode and cathode of LCO, LMO, NCA, NMC, LFP and LTO type of lithium ion cells.Give your detailed explanation on it

*Below is and image of a lithium iron cell battery and its component at charge and discharge state.

-Some of the differnt types of lithium iron battery on the market include.

- (LCO) Lithium Cobalt.

-(LMO) Lithium Manganese Oxide(Spinal)

-(NCA) Lithium Nickel Cobal Aluminium

-(NMC) Lithium Nickel Manganese Cobalt

-(LFP) Lithium Iron Phosphate

-(NTO) Lithium Titanium Oxide

Battery Anode, Cathode and Electrolytes(Conductors):

Lithium-ion uses a cathode (positive electrode), an anode (negative electrode) and electrolyte which is a non electron conductor midium that permites conduction of irons between the anode and the cathode(electron do not pass through electrolytes, just irons pass through electrolytes). (The anode of a discharging battery is negative and the cathode positive . The cathode is metal oxide and the anode consists of porous carbon.

-The Cathode and the Anode is separated by a layer called Separator which is permeable to the irons.

-The Cathode is the positive or oxidizing electrode that acquires electrons from the external circuit and is reduced during the electrochemical reaction. The Electrolyte is the medium that provides the ion transport mechanism between the cathode and anode of a cell.

-Anode materials are the negative electrode in lithium-ion batteries and are paired with cathode materials in a lithium-ion cell. The anode materials in lithium-ion cells act as the host where they reversibly allow lithium-ion intercalation / deintercallation during charge / discharge cycles.

Advantage:

-Lithium-iron batteries are able to be recharged hundreds of times and are more stable makng it reusable over a considrable duration.

-They tend to have a higher energy density, voltage capacity and lower self-discharge rate than other rechargeable batteries.

-This makes for better power efficiency as a single cell has longer charge retention than other battery types.

Disadvantage:

- lithium-ion batteries in electric cars is the use of organic liquid electrolytes, which are volatile and flammable when operating at high temperatures.

-An external force such as a crash can also lead to chemical leakage

-It lasts only few years after manufacturer.

-It is relatively expensive.

*What happens durng charging and discharging of battery.

*During Chargeing

During charging negative electrode (Anode) accepts electroncs and get reduced.

*During Discharging

During discharging the negative electrode (Anode) gives up electrons and get oxidized.

2.Compare the differences between each type of Li+ion batteries based on their characteristics

*The different type of Lithium iron battery include

- (LCO) Lithium Cobalt.

-(LMO) Lithium Manganese Oxide(Spinal)

-(NCA) Lithium Nickel Cobal Aluminium

-(NMC) Lithium Nickel Manganese Cobalt

-(LFP) Lithium Iron Phosphate

-(NTO) Lithium Titanium Oxide

1) (LCO) Lithium Cobalt:

LCO (Lithium cobalt oxide) was invented in the year 1991. Its anode material is LiaC6, the cathode material is LibCoO2 and the carrier is Li+.It is used in various applications ranging from electronic devices to all laptops and phone batteries.The majority of lithium-ion batteries for the portable devices are cobalt based. The system contains a cobalt oxide cathode (positive electrode) and graphite carbon anode (negative electrode).

The main advantages of the LCO batteries are:

• High energy density.
• Long runtime making it optimum for new technologies

The main disadvantages of the LCO batteries are:

• It has a relatively low discharge current so high load can lead to pack overheat
• The safety circuit of the LCO battery is typically limited to a 1C for charging and discharging.
• The internal resistance increases with cycling and aging. This high internal resistance can cause the battery to become unserviceable due to a large voltage drop under the load after a couple of years of use.

2) (LMO) Lithium Manganese Oxide(Spinal):

LNMO (Lithium Nickel Manganese Oxide) cathode material is a cobalt-free high-voltage spinel for use in next-generation lithium-ion rechargeable batteries. LNMO battery chemistry has numerous advantages. The high working potential and high energy density pave the way to either longer operating ranges or a smaller battery package, whilst the three-dimensional spinel structure makes it possible to achieve high discharge rates and fast battery charging. The absence of cobalt and the relatively low nickel content make this a cost-effective alternative to today’s mainstream lithium-ion battery chemistries.A typical application of Lithium Manganese Dioxide cells is to provide memory or microcontroller backup power in the event of a power failure or rechargeable battery depletion.

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.

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.

3) (NCA) Lithium Nickel Cobal Aluminium:

For most applications of lithium-ion batteries (LiBs), such as electric vehicles (EVs), the end of life (EoL) criterion is defined as the decrease of the dischargeable capacity of the battery by as little as 20 % or 30 % of its initial value.How fast this threshold is reached will vary considerably depending on intrinsic factors, such as chemistry and manufacturing quality, and on extrinsic factors such as operation temperature, exposition to certain voltage/current windows, rest periods, and the presence of efficient battery (thermal) management systems.

Lithium Nickel-Cobalt-Aluminum Oxide (NCA) is used as the cathode material for lithium ion batteries, and is mainly used in electric automobiles. Due to a high nickel content of the Lithium Nickel-Cobalt-Aluminum Oxide (NCA) manufactured by the company, the capacity of batteries can be increased, which contributes to a longer distance that can be covered with a single-time charging.

-NMC is a novel lithium insertion electrode material for advanced lithium-ion batteries. Mn doping significantly increases the thermal stability besides increasing the electrochemical charge-discharge behavior.

4) (NMC) Lithium Nickel Manganese Cobalt:

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 18650 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. This offers a unique blend that also lowers the raw material cost due to reduced cobalt content. Another successful combination is NCM with 5 parts nickel, 3 parts cobalt and 2 parts manganese (5-3-2). Other combinations using various amounts of cathode materials are possible.

Battery manufacturers move away from cobalt systems toward nickel cathodes because of the high cost of cobalt. Nickel-based systems have higher energy density, lower cost, and longer cycle life than the cobalt-based cells but they have a slightly lower voltage.

5) (LFP) Lithium Iron Phosphate:

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. 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.

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.

6 (NTO) Lithium Titanium Oxide:

Batteries with lithium titanate anodes have been known since the 1980s. 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. Typical uses are electric powertrains, UPS and solar-powered street lighting.

*Summary of future of battery