Week 1 Understanding Different Battery Chemistry

AIM:- Understanding Different Battery Chemistry

OBJECTIVE:-

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

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

OBJECTIVE:- 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

 Introduction to batteries:-

.The battery is an energy storage device formed by one or more electrochemical cells that can store and delivered electricity by an internal chemical process, more specifically, redox reactions.

.The amount of energy stored and delivered by the cell is determined by the active material mass in the electrodes.

.Batteries can be divided into two major groups, primary and secondary.

.Primary batteries are non-rechargeable systems, due to non-reversibility of the redox reaction.

.Secondary batteries differ from the primary by the ability to reverse the redox reaction and therefore be able to have several discharge/charge cycles. Rechargeable batteries are mostly produced in the discharged state thus an initial charge process is needed prior the use.

Lithium-ion battery Chemistry:-

. Lithium-ion battery consists of reversible redox reactions that take places on the electrode surface facing the electrolyte.

. It is defined that the anode (negative electrode) is where the oxidation happens while in the cathode(positive electrode) the reduction, both during the discharge process.

.The commonly active materials used for LIB are graphitised carbon (C) in anodes and lithium cobalt oxide
(LiCoO2) in cathodes.

. Anode reaction: Ca + bLi+ + be- ↔ LibCa 

. Cathode reaction: LiCoO2 ↔ Li(1 - b)CoO2 + bLi+ + be-

. Total reaction: Ca + LiCoO2↔ LibCa + Li(1 - b)CoO2

. In a LIB, during the discharge, the Li ions released from the anode, de-intercalate in the case of graphite, are solvated by the electrolyte molecules, and transported to the cathode driven by the difference of potential.

. As the name suggests, lithium ions (Li ) are involved in the reactions driving the battery.

Both electrodes in a lithium-ion cell are made of materials which can intercalate or ‘absorb’ lithium ions .

 . Intercalation is when charged ions of an element can be ‘held’ inside the structure of a host material without significantly disturbing it.

. In the case of a lithium-ion battery, the lithium ions are ‘tied’ to an electron within the structure of the anode.

. When the battery discharges, the intercalated lithium ions are released from the anode, and then travel through the electrolyte solution to be absorbed (intercalated) in the cathode.

. A lithium-ion battery starts its life in a state of full discharge:

. All its lithium ions are intercalated within the cathode and its chemistry does not yet have the ability to produce any electricity.

.Before you can use the battery, you need to charge it.

 . As the battery is charged, an oxidation reaction occurs at the cathode, meaning that it loses some negatively charged electrons.

.To maintain the charge balance in the cathode, an equal number of some of the positively charged intercalated lithium ions are dissolved into the electrolyte solution.

.These travel over to the anode, where they are intercalated within the graphite.

.This intercalation reaction also deposits electrons into the graphite anode, to ‘tie’ up the lithium ion.

Types of Li-ion Cells:-

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.

.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 as Energy cells or power Cells.

.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 ion phosphate(LiFepo4) - LFP:-

.In 1996, 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. 

.Li-phosphate is often used to replace the lead acid starter battery.

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. 

. summarizes the six key characteristics. 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 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.

FUTURE OF BATTERIES:-

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

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

.Lithium-air: High specific energy but poor loading, needs clean air to breath 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 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):-

OBJECTIVE:-2

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

.Compromises also exist on lithium-based batteries.

.Li‑ion packs are being produced for defense applications that far exceed the energy density of the commercial equivalent.

.Unfortunately, these super-high capacity Li‑ion batteries are deemed unsafe in the hands of the public and the high price puts them out of reach of the commercial market.

.In this article we look at the advantages and limitations of the commercial battery.

.The so-called miracle battery that merely live in controlled environments is excluded.

.We scrutinize the batteries not only in terms of energy density but also longevity, load characteristics, maintenance requirements, self-discharge and operational costs.

.Since NiCd remains a standard against which other batteries are compared, we evaluate alternative chemistries against this classic battery type.

Nickel Cadmium (NiCd) — mature and well understood but relatively low in energy density.

.The NiCd is used where long life, high discharge rate and economical price are important.

.Main applications are two-way radios, biomedical equipment, professional video cameras and power tools.

.The NiCd contains toxic metals and is environmentally unfriendly.

Nickel-Metal Hydride (NiMH) — has a higher energy density compared to the NiCd at the expense of reduced cycle life.

.NiMH contains no toxic metals. Applications include mobile phones and laptop computers.

Lead Acid — most economical for larger power applications where weight is of little concern.

.The lead acid battery is the preferred choice for hospital equipment, wheelchairs, emergency lighting and UPS systems.

Lithium Ion (Li‑ion) — fastest growing battery system. Li‑ion is used where high-energy density and lightweight is of prime importance.

.The technology is fragile and a protection circuit is required to assure safety.

. Applications include notebook computers and cellular phones.

Lithium Ion Polymer (Li‑ion polymer) — offers the attributes of the Li-ion in ultra-slim geometry and simplified packaging. Main applications are mobile phones.