Week 1 Understanding Different Battery Chemistry

AIM:

1. To 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.

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

INTRODUCTION

Battery:

A battery is a device that converts chemical energy contained within its active materials directly into electric energy by means of an electrochemical oxidation reduction (redox) reaction. This type of reaction involves the transfer of electrons from one material to another via an electric circuit. While the term battery is often used the cell is the actual electrochemical unit used to generate or store electric energy. In understanding the differences between a cell and a battery, one should think of a battery as one or more of these cells connected in series or parallel or both, depending on the desired output voltage and capacity.

Battery is of two types Primary and Secondary.

Here we are going to discuss about the secondary cell (Lithium ion)

LiTHIUM ION CELL:

A lithium-ion (Li-ion) battery is an advanced battery technology that uses lithium ions as a key component of its electrochemistry. During a discharge cycle, lithium atoms in the anode are ionized and separated from their electrons. The lithium ions move from the anode and pass through the electrolyte until they reach the cathode, where they recombine with their electrons and electrically neutralize. The lithium ions are small enough to be able to move through a micro-permeable separator between the anode and cathode. In part because of lithium’s small size (third only to hydrogen and helium), Li-ion batteries are capable of having a very high voltage and charge storage per unit mass and unit volume.

Li-ion batteries can use a number of different materials as electrodes. The most common combination is that of lithium cobalt oxide (cathode) and graphite (anode), which is most commonly found in portable electronic devices such as cellphones and laptops. Other cathode materials include lithium manganese oxide (used in hybrid electric and electric automobiles) and lithium iron phosphate. Li-ion batteries typically use ether (a class of organic compounds) as an electrolyte.

WORKING OF LITHIUM ION CELL:

A "positive electrode" connects to the battery's positive (+) terminal. A negative electrode connects to the negative (−) terminal. And a chemical called an electrolyte in between them.

1. Cathode:

• They are the positive elctrodes of the cell.
• The cathode elctrode is usually made up of,

* Layered Transition metal oxides

* Spinels

* Olivines

2. Anode:

• They are the negative elctrodes of the cell.
• The anode elctrode is usually made up of,

* Graphite

* Hard Carbon

3. Electrolyte:

• An electrolyte is a substance that produces an electrically conducting solution when dissolved in a polar solvent.
• The dissolved electrolyte separates into cations and anions, which disperse uniformly through the solvent.
• Generally Lithium ion cells have electrolyes of Organic solvents such as, Ethylene carbonate, dimethyl carbonate, propylene carbonate and lithium salt as solute.

4. Seperator:

• Battery separators provide a barrier between the anode (negative) and the cathode (positive) while enabling the exchange of lithium ions from one side to the other.
• They are materials that conducts ions but they do not conduct the electrons through them.
• Li-ion cells use polyolefin as a separator. This material has excellent mechanical properties, good chemical stability and is low-cost as well.

Charging Cycle:

The electrolyte carries positively charged lithium ions from the anode to the cathode.The movement of the lithium ions creates free electrons in the anode which creates a charge at the positive current collector. The electrical current then flows from the current collector through a device being powered to the negative current collector. The separator blocks the flow of electrons inside the battery.

Discharging cycl:

While the battery is discharging and providing an electric current, the anode releases lithium ions to the cathode, generating a flow of electrons from one side to the other. When plugging in the device, the opposite reaction happens, the cathode releases lithium ions and anode receives them. This is how the Lithium-ion battery works.

In this battery, the energy density and power density are most common things of the battery. Generally, the energy density measures in watt-hours per kilogram (wh/kg) and is the amount of energy the battery can store with respect to its mass. Power density measures in watts per kilogram (W/kg) and is the amount of power of battery with respect to its mass.

Adventage:

• Compared to the other high-quality rechargeable battery technologies.
• Li-ion battery cells can deliver up to 3.6 Volts, 3 times higher than technologies such as Ni-Cd or Ni-MH.
• They do not contain toxic cadmium, which makes them easier to dispose of than Ni-Cd batteries.
• They can deliver large amounts of current for high-power applications

Disadventage:

• Li-ion batteries still have a number of shortcomings, particularly with regards to safety.
• Li-ion batteries have a tendency to overheat, and can be damaged at high voltages.
• This can lead to thermal runaway and combustion.
• Cost which is around 40% higher than Ni-Cd.

Types of Li-ion Battery

• Lithium Cobalt Oxide (LiCoO2) — LCO
• Lithium Manganese Oxide (LiMn2O4) — LMO
• Lithium Nickel Manganese Cobalt Oxide (LiNiMnCoO2) - NMC
• Lithium Iron Phosphate (LiFePO4) — LFP
• Lithium Nickel Cobalt Aluminum Oxide (LiNiCoAlO2) — NCA
• Lithium Titanate (Li2TiO3) — LTO

Lithium Cobalt Oxide (LiCoO2) — LCO:

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).

Lithium Manganese Oxide (LiMn2O4) — LMO

Li-ion with manganese spinel was first published in the Materials Research Bulletin in 1983. In 1996, 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.

Lithium Nickel Manganese Cobalt Oxide (LiNiMnCoO2 ) — NMC

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 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.

Lithium Iron Phosphate(LiFePO4) — LFP

This cell has a high discharge rate and, because phosphate (PO ) can cope with high temperatures, the battery has good thermal stability, improving its safety. This makes it a good choice for things like electric vehicles and power tools, and for storing energy at power stations. It also has a long cycle life, meaning it can be discharged and charged many times. However, it has a lower energy density than a lithium cobalt oxide cell, and a higher self-discharge rate.A lithium iron phosphate battery cell is similar to the lithium cobalt oxide cell. The anode is still graphite and the electrolyte is also much the same. The difference is that the lithium cobalt dioxide cathode has been replaced with the more stable lithium iron phosphate. In fact, no lithium or iron ions remain in the iron phosphate (FePO4) cathode of a fully charged cell. The lithium ions can intercalate into or out of the cathode material through well-defined tunnels in its structure without significantly altering the iron phosphate framework.

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, reasonably good specific power and a long life span. Less flattering are safety and cost. NCA is a further development of lithium nickel oxide; adding aluminum gives the chemistry greater stability. High energy and power densities, as well as good life span, make NCA a candidate for EV powertrains. High cost and marginal safety are negatives.

Lithium Titanate (Li2TiO3) — LTO

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 lowtemperature 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.

Table below shows the materials includes & chemical reactions :

Cell Name (chemical name)	Cathode Material	Anode Material	Chemical Reaction at Cathode	Chemical Reaction at Anode	Overall Reaction
LCO(LiCo02)	Lithium Cobalt Oxide	Graphite Carbon	Li1-xCo02 +xLi+ + x e- --> LiCo02	C6Li --> 6C + Li+ + e-	C6+ LiCo02 --> LixC6+ Li1-xCoO2
LMO(LiMn204)	Lithium Manganese Oxide	Graphite Carbon	Mn02 + Li+ + e- --> LiMn02	Li --> Li++ e-	Li + Mn02 --> LiMn02
NMC(LiNiMnCo02)	Lithium Nickel Manganese Cobalt Oxide	Graphite Carbon	Li 1-x (Ni 1xy MnxCoy )02+ xLi+ + x e- --> LiNiMnCo02	LixCn -->nC + xLi+ + x e-	Li1-x(Ni1-x-y MnxCoy)02 + LixCn --> LiNiMnCoO2 +nC
LFP(LiFePO4)	Lithium Iron Phosphate	Graphite Carbon	Li 1-x FePo4+ xLi+ + x e- -->LiFePo4	LixC6 --> 6C + x Li+ + x e-	C6 + LiFePo4 --> LixC6 + FePo4
NCA(LiNiCoAl02)	Lithium Nickel Cobalt Aluminium Oxide	Graphite Carbon	NiCoAlO2+ Li+ + e- --> LiNiCoA102	CsLi --> 6C + Li+ + e-	C6Li + NiCoA102 --> Li1-x NiCoAlO2 + LixC6
LTO(Li2TiO3)	Manganese Oxide	Lithium Titanium Oxide	4Li1-x Mn204 + 4Li+ + 4 e- --> 4LiMn204	Li7Ti5O12­­ --> TisO12 + 4Li+ + 4e­-	Li7TisO12+ 4Mn2O4 --> 4LiMn2O4 + Ti5O12

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

The main differences between the lithium ion batteries can be differentiated on the characteristics. There are 6 major types of lithium ion batteries was have been discussed early. Now the major differences in the characteristics can be found when choosing a battery.

The major things that are.

• Nominal Voltage.
• Charge current rate.
• Discharge current rate.
• Cycle life.
• Specific energy.
• Thermal runaway.

1. Nominal Voltage.

Most of the batteries are very close when it comes to characteristics. LMO (3.7) has the highest range and LTO (2.4) has the lowest range in volts.

2. Charge current rate.

Higher the charge current, the less time the battery will take to get fully charged. LTO and LTP are highest NCA comes close to its condenders.

3. Discharge current rate.

If we need higher discharge rates and faster charging times we should choose a high rated battery instead. LTO has a discharge rate 10 times higher than the others and it t=is one of the safest batteries.

4. Cycle life.

They differ by a significant amount from each other. LTO battery has the longest life cycle so that it can last longer period of time and it is exactly opposite for the LMO type batteries.

5. Specific energy.

The specific energy density can be calculated by integrating from 0 to t_cutoff. We can obtain the specific energy density in Wh Kg^-1. Lithium ion with cobalt cathodes offer the highest energy densities. This types of applications are cell phones, laptops and digital cameras. Power density indicates how much power a battery can deliver on demand.

6. Thermal runaway.

A thermal runaway occurs in situations where an increase in temperature changes the conditions in a way that causes increase in temperature often leading a destructive result. LTO has the highest temperature rating in this and NCA and LCP has its lowest.

For the case of choosing a battery from laymans perspective, the 6 key features are given a value within 0-4 range are given with the same parameters which are considered in case of 5 point hexagonal analysis of the batteries. They are

1. Specific energy.
2. Specific power.
3. Safety.
4. Performance.
5. Life span.
6. Cost.

Lithium Cobalt Oxide (LCO):

This battery has the highest energy density. The specific energy is in the range of 150 to 200 Wh/Kg. The limitation is thermal instablitiy the anode can overheat. At high temp the cathode can decompose and produce oxygen SOmetimes the electrolute used is diethyl carbonate which is flammable in nature hence, this type of battery can catch fire due to overheating the thermal runaway occurs at 150 degree c. It has a short life span due to formation of solid Electrolyte Layer (SEI) at anode and lithium plating due to fast charging and charging at low temp.typically it has life span of 500 to 1000 cycles. It has limited load capabilities since it cannot be charged or discharged beyond its C-rate should be maintained in the range of 0.7 c to 1c.

Li-cobalt excels on high specific energy but offers only moderate performance specific power, safety and life span.

Applications:

Mobile phones, Laptops, camera etc

Lithium Manganese Oxide:

The spinel structure (AB2O4 Structure) of Lithium manganese enables this type of battery to have better thermal stability so it is better in terms of safety The high charge promotes thermal runaway at a high temp of 250c. The Spinel structure promotes the ion flow within the electrolyte and this reduces the internal resistance of the battery. The limitation is that it loses the battery power over time. It has shorter lifetime of 300-700 cycles and lower capacity The specific energy of this battery is 100-150 Wh/kg. It has ability to charge and discharge at higher C-rate, So it is used for a high current boost on acceleration in EV.

Although moderate in overall performance, newer designs of Li-manganese offer improvements in specific power, safety and life span.

Application:

Power tools, Medical devices, Electrical Power trains.

Lithium Nickel Manganese Cobalt Oxide:

This type of battery has the advantage of Lithium cobalt oxide. & Lithium Manganse Oxide. Thermal runaway occurs at a high temp of 210c. It has a life span of 1000 to 2000 cycles. This combination has a mixture of one third nickel, one third Cobalt, and one third Manganese, Cobalt is expensive and limited in supply. Hence the proportion of cobalt in the recent batteries. This battery is preferred for electric vehicles due to its low self heating rate

NMC has good overall performance and excels on specific energy. This battery is the preferred candidate for the electric vehicle and has the lowest self heating rate.

Application:

Electrically-powered cars, including hybrid vehicles.

Lithium Iron Phosphate:

This battery has a high discharge rate because of low internal resistance made possible by nano scale phosphate cathode material. Due to the presence of phosphate (PO4) that can cope up with high temp At cathode Phosphate anions are bonded with iron cations. This structure holds the oxygen molecules tightly and give cathode chemical stability This battery has good thermal stability Thermal runaway is caused at 270 c. It can be used for higher number of discharge cycles as high as 2000.It has higher self discharge rate. This battery is more tolerant to full charge and less stressed when kept at full voltage for prolonged period.

Li-phosphate has excellent safety and long life span but moderate specific energy and elevated self discharge.

Application:

portable devices needed high load current and endurance.

Lithium Nickel Cobalt Aluminium Oxide:

It is a further development of lithium Nickel oxide Adding Auminium to the chemistry gives the battery greater stability. It has feature similar to NMC Battery high specific energy (200-260 Wh/kg) Good specific power and a long life span

High energy and power densities as well as a good life span make NCA a candidate for EV powertrains. High cost and marginal safety are negative.

Applications:

Medical Equipments and EV (Tesla)

Lithium Titanate:

In this battery Graphite as anode is replaced by Lithium Titanate formed into a spinel strcture. It has fast charge capability and a high discharge curent of 10c which is 10 times the usual capacity. This battery is safe it has good low temp. discharge capability and can acheive c charger level of 80% atv -30 c. It is advantage over lithium cobalt oxide because ther is no solid Electrolyte interface formation or lithium plating while fast charging or discharging at low temp. It has a greater life span than any other Lithium-ion battery It can go up to 5000 Cycles.

Li-titanate excels in safety, low temperature performance and life span. Efforts are being made to improve the specific energy and lower the cost

Applications:

Electrical Powertrains, SOlar Street lights.

Concluction:

These types of lithium ion batteries are some of the most popular. As technology is continously seeing more development, new lithium technologies are always being developed and those which exists are being developed.

Differences between each type of Li+ion batteries based on their characteristics has been done

Reference :

ngton.edu/education/science-of-solar/battery-technology/

https://robu.in/working-of-lithium-ion-battery/

https://www.onecharge.biz/lithium-cell-chemistry/#:~:text=Of%20all%20the%20various%20types,cobalt%20aluminum%20oxide%20(NCA).

https://batteryuniversity.com/article/bu-205-types-of-lithium-ion