Week 1 Understanding Different Battery Chemistry

Lithium-Ion-Battery :-

A lithium-ion-battery or Li-ion-battery is a type of rechargable battery in which lithium ions move from the negative electrode through an electrolyte to the positive electrode during discharge and back when charging. Li-ion-batteries use an intercalated lithium compound as the material at the positive electrode and typically graphite at the negative electrode.

Li-ion-batteries have a high energy denstiy, no memory effect and low self-discharge. Cells can be manufactured to either prioritize energy or power density. They can however be a safety hazard since they contain flammable electrolytes and if damaged or incorrectly charged can lead to explosions and fires.

Chemistry, performance cost and safety characteristics vary acroos types of lithium-ion batteries. Handheld electronics mostly use lithium polymer batteries a lithium cobalt oxide(LiCoO2) cathode material, and a graphite anode which together offer a high energy density. Lithium iron phospphate(LiFePO4), lithium manganese oxide(LiMn2O4 or Li2MnO3-based lithiun rich layered materials, LMR-NMC), and lithium nickel manganese cobalt oxide (LiNiMnCoO2 or NMC) may offer longer lives and widely used for electric tools, medical equipment, and other roles, NMC and its derivatives are widely used in electric vehicles.

Research areas for lithiumm-ion batteries include extending lifetime, increasing energy density, improving safety, reducing cost, and increasing charging speed, among others. Research has been under way in the area of non-flammable electrolytes as a pathway to increased safety based on the flammability and voltatility of the organic solvents used in the typical electrolyte. Strategies include aqueous lithium-ion batteries, ceramic solid electrolytes, polymer electrolytes, ionic liquids and heavily fluorinated systems.

Types of Lithium-ion :-

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 from 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.

Lithium Cobalt Oxide(LiCoO2) - LCO :-

Its high specific energy makes Li-cobalt the popular choice for mobile phones, laptops and digital camers. The battery consists of a coblat 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 reverse short life span, low thermal stability and limited load capabilities.

The cathode has a layered structure. During discharge the lithium ions move from the anode to the cathode; on charge the flow is from cathode to anode. Source: Cadex.

The drawback of Li-cobalt is relatively short life span, low thermal stability and limited load capacbilities. Like other cobalt-blended Li-ion, Li-cobalt has a graphite anode that limits the cycle life by a charging solid electrolyte interface thickening on the anode and lithium plating while fast charging and charging at low temperature. Never systems include nickel, manganese and or aluminium to improve iongevity, loading capabilities and cost.

Lithium Manganese Oxide(LiMn2O4) - LMO :-

Li-ion with manganese spinel was first published in the materials research bulet in 1983. In 1996, Moli energy commercialized a Li-ion cell with lithiu manganese oxide as cathode material. The architecture form 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 18650 packages, Li manganese can be discharged at currently of 20-30A with moderate heat buildup. It is also possible to apply one second load pulses of up to 50A. A contiuous 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.

Lithium Nickel Manganese Cobalt Oxide(LiNiMnCo2O) - NMC :-

One of the most successful Li-ion system is a cathode combination of nickel-manganese -cobalt(NMC). Similar to Li-manganese these system 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 curret 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 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 metal enhance each other strengths.

Lithium Iron Phosphate(LiFePO4) - LFP :-

It is discovered for rechargable phophate as cathode material for rechargable lithiu 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. 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 shortens the service life and Li-phophate is no exception 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 cycle.

Lithium Nickel Cobalt Aluminum Oxide(LiNiCoAlO2) - NCA :-

Lithium nickel cobalt aluminum oxide battery, or NCA has been around since 1999 for special applications. It shares similarities with NMC by offering high specific energy, reasonability good specific power and a long life span. Less flattering are safety and cost. Summarizes the six key characteristics. NCA is a further development of lithium nickel oxide; adding aluminum gives the chemistry greater stability.

Lithium Titanate(Li2TiO3) - LTO:-

Batteries with lithium titanate anodes have been known since the 1980s. Li-titanate replace the graphite in the anode of a typically 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 dddand 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.

LTO has advantage 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-titate charges to 2.80V/cell, and the end of discharge is 1.80V/cell.

Future Batteries :-

i. Solid-state Li-ion : High specific energy but poor loading and safety.

ii. Lithium-sulfur : High specific energy but poor cycle life and poor loading.

iii. Lithium-air : High specific energy but poor loading, needs clean air to breathe and has short life.

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 outives 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.

Anode Reaction :-

LiC6 == xLi++xe-+C6

Cathode Reaction :-

Li1 - xCoO2 + xLi + + xe == LiCoO2

Li1 - xMn2O4 + xLi + + xe == LiMnO2

Li1 - xMO2 + xLi + + xe == LiMO2

LiFe(lll)PO4 + xLi + + xe == LiFe(ll)PO4

Li1 - xMO2 + xLi + + xe == LiMO2

4Mn2O4 + 4Li + + 4e == 4LiMn2O4

Over all Reaction :-

C6 + LiCoO2 == LixC6 + Li1 - xCoO2

LiC6 + Mn2O4 == C6 + LiMnO2

Lix - xMO2 + LiC6 == Li1 - xMO2 + C6

LiFePO4 + 6C == LiC6 + FePO4

Li1 - xMO2 + LiC6 == Li1 - xMO2 + C6

Li4Ti5O12 + 4Mn2O4 == 4LiMn2O4 + Ti5O12

Separator :-

Polylefin for all Type of batteries.