View source for Lithium iron phosphate

{{chembox
| Verifiedfields = changed
| Watchedfields = changed
| verifiedrevid = 450705077
| ImageFile1 = Atomic structure of olivine 1.png
| ImageFile2 = Lithium iron phosphate.svg
| ImageSize = 
| IUPACName = iron(2+) lithium phosphate (1:1:1)
| OtherNames = 
|Section1={{Chembox Identifiers
| Abbreviations = 
| StdInChI_Ref = {{stdinchicite|correct|chemspider}}
| StdInChI = 1S/Fe.Li.H3O4P/c;;1-5(2,3)4/h;;(H3,1,2,3,4)/q+2;+1;/p-3
| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
| StdInChIKey = GELKBWJHTRAYNV-UHFFFAOYSA-K
| InChI = 1S/Fe.Li.H3O4P/c;;1-5(2,3)4/h;;(H3,1,2,3,4)/q+2;+1;/p-3
| InChIKey1 = GELKBWJHTRAYNV-UHFFFAOYSA-K
| CASNo_Ref = {{cascite|changed|??}}
| CASNo = 15365-14-7
| EINECS = 604-917-2
| PubChem = 15320824
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| ChemSpiderID = 10752170
| SMILES = [Fe+2].[Li+].[O-]P([O-])([O-])=O
| RTECS =
| MeSHName = 
| ChEBI_Ref = {{ebicite|correct|EBI}}
| ChEBI = 
| KEGG_Ref = {{keggcite|correct|kegg}}
| KEGG = 
}}
|Section2={{Chembox Properties
| Formula = {{chem|FeLiO|4|P}}
| MolarMass = 157.757
| Appearance =
| Density = 
| MeltingPt = 
| MeltingPt_notes =
| BoilingPt = 
| BoilingPt_notes = 
| Solubility = 
| SolubleOther = 
| Solvent = 
| pKa = 
| pKb = 
  }}
|Section7={{Chembox Hazards
| ExternalSDS = 
| MainHazards = 
| NFPA-H = 
| NFPA-F = 
| NFPA-R = 
| NFPA-S =
| FlashPt = 
| AutoignitionPt = 
| ExploLimits = 
| PEL = 
  }}
}}

'''Lithium iron phosphate''' or '''lithium ferro-phosphate''' ('''LFP''') is an [[inorganic compound]] with the formula '''{{chem|LiFePO|4}}'''. It is a gray, red-grey, brown or black solid that is insoluble in water. The material has attracted attention as a component of [[Lithium iron phosphate battery|lithium iron phosphate batteries]],<ref>Park, O. K.; Cho, Y.; Lee, S.; Yoo, H.-C.; Song, H.-K.; Cho, J., "Who Will Drive Electric Vehicles, Olivine or Spinel?", Energy Environ. Sci. 2011, volume 4, pages 1621-1633. {{doi|10.1039/c0ee00559b}}</ref><ref>{{Cite web |date=2025-03-26 |title=Lithium iron Phosphate Battery |url=https://www.ogniwa-lifepo4.pl/blog/akumulator-litowo-zelazowo-fosforanowy.html |access-date=2025-05-31}}</ref> a type of [[Lithium-ion battery|Li-ion battery]].<ref name="EngineeringIntegrations2021">{{cite book |last1=Chung |first1=Hsien-Ching |last2=Nguyen |first2=Thi Dieu Hien |last3=Lin |first3=Shih-Yang |last4=Li |first4=Wei-Bang |last5=Tran |first5=Ngoc Thanh Thuy |last6=Thi Han |first6=Nguyen |last7=Liu |first7=Hsin-Yi |last8=Pham |first8=Hai Duong |last9=Lin |first9=Ming-Fa |title=First-Principles Calculations for Cathode, Electrolyte and Anode Battery Materials |date=December 2021 |publisher=IOP Publishing |url=https://doi.org/10.1088/978-0-7503-4685-6ch16 |chapter=Chapter 16 - Engineering integrations, potential applications, and outlooks of Li-ion battery industry|doi=10.1088/978-0-7503-4685-6ch16 |isbn=978-0-7503-4685-6 }}</ref>  This battery chemistry is targeted for use in [[power tool]]s, [[electric vehicles]], solar energy installations<ref name="Batteries10(2024)202">{{cite journal |last1=Chung |first1=Hsien-Ching |title=The Long-Term Usage of an Off-Grid Photovoltaic System with a Lithium-Ion Battery-Based Energy Storage System on High Mountains: A Case Study in Paiyun Lodge on Mt. Jade in Taiwan |journal=Batteries |date=13 June 2024 |volume=10 |issue=6 |pages=202 |doi=10.3390/batteries10060202|doi-access=free |arxiv=2405.04225 }}</ref><ref>{{Cite web|title = New Energy Storage Startup to Take Hawaii Homes Off-Grid|url = http://www.hawaiiweblog.com/2015/07/06/blue-planet-energy-ion-battery|website = Hawaii Blog|accessdate = 2015-07-09|last = Ozawa|first = Ryan|date = 7 July 2015}}</ref> and more recently large [[Battery storage power station|grid-scale energy storage]].<ref>{{Cite web|url=https://datacenterfrontier.com/google-looks-to-batteries-as-replacement-for-diesel-generators/#:~:text=The%20pilot%20project%20at%20Google%27s,Free%20Energy%20Lead%20at%20Google.|title = Google Looks to Batteries as Replacement for Diesel Generators|date = 16 December 2020}}</ref>{{r|EngineeringIntegrations2021}}

Most lithium batteries (Li-ion) used in consumer electronics products use cathodes made of lithium compounds such as [[lithium cobalt oxide]] ({{chem|LiCoO|2}}), lithium manganese oxide ({{chem|LiMn|2|O|4}}), and lithium nickel oxide ({{chem|LiNiO|2}}). The [[anodes]] are generally made of [[carbon|graphite]].

Lithium iron phosphate exists naturally in the form of the mineral [[triphylite]], but this material has insufficient purity for use in batteries.

=={{chem|LiMPO|4}}==
With general chemical formula of {{chem|LiMPO|4}}, compounds in the {{chem|LiFePO|4}} family adopt the [[olivine]] structure.  M includes not only Fe but also Co, Mn and Ti.<ref>{{Cite journal|last1=Fedotov|first1=Stanislav S.|last2=Luchinin|first2=Nikita D.|last3=Aksyonov|first3=Dmitry A.|last4=Morozov|first4=Anatoly V.|last5=Ryazantsev|first5=Sergey V.|last6=Gaboardi|first6=Mattia|last7=Plaisier|first7=Jasper R.|last8=Stevenson|first8=Keith J.|last9=Abakumov|first9=Artem M.|last10=Antipov|first10=Evgeny V.|date=2020-03-20|title=Titanium-based potassium-ion battery positive electrode with extraordinarily high redox potential|journal=Nature Communications|language=en|volume=11|issue=1|page=1484|doi=10.1038/s41467-020-15244-6|pmid=32198379|pmc=7083823|bibcode=2020NatCo..11.1484F|issn=2041-1723|quote=LiTiPO4F|doi-access=free}}</ref> As the first commercial {{chem|LiMPO|4}} was C/{{chem|LiFePO|4}}, the whole group of {{chem|LiMPO|4}} is informally called “lithium iron phosphate” or “{{chem|LiFePO|4}}”. However, more than one olivine-type phase may be used as a battery's cathode material. Olivine compounds such as {{chem|A|''y''|MPO|4}}, {{chem|Li|1−''x''|MFePO|4}}, and {{chem|LiFePO|4−''z''|M}} have the same crystal structures as {{chem|LiMPO|4}}, and may replace it in a cathode. Although the term '{{chem|LiFePO|4}}' (LFP) strictly refers to the iron-based compound, related olivine-type phosphates with similar structures—such as {{chem|A|''y''|MPO|4}}, {{chem|Li|1−''x''|MFePO|4}}, and {{chem|LiFePO|4−''z''|M}}—are sometimes informally included under the LFP designation due to structural and electrochemical similarity.<ref>{{Cite web |last=Wang |first=J. |last2=Sun |first2=X. |date=2015-04-15 |title=Olivine LiFePO₄: The Remaining Challenges for Future Energy Storage |url=https://doi.org/10.1039/C4EE04016C |url-status=live |access-date=2025-05-30 |website=Energy & Environmental Science |doi=10.1039/C4EE04016C |quote=Various substituted LiMPO₄ compounds, while structurally analogous to LiFePO₄, are often informally grouped under the LFP designation due to their shared olivine structure and comparable electrochemical behavior.}}</ref>

Manganese, phosphate, iron, and lithium also form an [[Olivine|olivine structure]]. This structure is a useful contributor to the cathode of lithium rechargeable batteries.<ref>{{cite journal|last=Kim|first=Jongsoon|title=Thermal Stability of Fe-Mn Binary Olivine Cathodes for Li Rechargeable Batteries.|journal=Journal of Materials Chemistry|year=2012|volume=22|issue=24|page=11964|url=http://pubs.rsc.org/en/content/articlehtml/2012/JM/C2JM30733B|publisher=The Royal Society of Chemistry|doi=10.1039/C2JM30733B|accessdate=19 Oct 2012|url-access=subscription}}</ref> This is due to the olivine structure created when lithium is combined with manganese, iron, and phosphate (as described above). The olivine structures of lithium rechargeable batteries are significant, for they are affordable, stable, and can be safely used to store energy.<ref>Wang, J.; Sun, X., "Olivine Lifepo4: The Remaining Challenges for Future Energy Storage", Energy Environ. Sci. 2015, volume 8, pages 1110-1138. {{doi|10.1039/C4EE04016C}}</ref>

==History and production==
[[Arumugam Manthiram]] and [[John B. Goodenough]] first identified the [[polyanion]] class of cathode materials for [[lithium ion batteries]].<ref>{{cite journal |last1=Masquelier |first1=Christian |last2=Croguennec |first2=Laurence |title=Polyanionic (Phosphates, Silicates, Sulfates) Frameworks as Electrode Materials for Rechargeable Li (or Na) Batteries |doi=10.1021/cr3001862 |work=Chemical Reviews |volume=113 |issue=8 |pages=6552–6591 |year=2013|pmid=23742145 }}</ref><ref>{{cite journal |last1=Manthiram |first1=A. |last2=Goodenough |first2=J. B. |doi=10.1016/0378-7753(89)80153-3 |title=Lithium insertion into Fe<sub>2</sub>(SO<sub>4</sub>)<sub>3</sub> frameworks |work=Journal of Power Sources |volume=26 |issue=3–4 |pages=403–408 |year=1989 |bibcode=1989JPS....26..403M }}</ref><ref>{{cite journal |last1=Manthiram |first1=A. |last2=Goodenough |first2=J. B. |doi=10.1016/0022-4596(87)90242-8 |title=Lithium insertion into Fe<sub>2</sub>(MO<sub>4</sub>)<sub>3</sub> frameworks: Comparison of M = W with M = Mo |work=Journal of Solid State Chemistry |volume=71 |issue=2 |pages=349–360 |year=1987 |bibcode=1987JSSCh..71..349M |doi-access=free }}</ref> {{chem|LiFePO|4}} was then identified as a cathode material belonging to the polyanion class for use in batteries in 1996 by Padhi et al.<ref>{{cite conference |last1=Padhi |first1=A. K. |last2=Nanjundaswamy |first2=K. S. |last3=Goodenough |first3=J. B. |date=May 1996|title={{chem|LiFePO|4}}: A Novel Cathode Material for Rechargeable Batteries |work=Electrochemical Society Meeting Abstracts |volume=MA1996-01 |pages=73 |location=Los Angeles |conference=189th ECS Meeting |doi= |doi-access=}}</ref><ref>{{cite journal |last1=Padhi |first1=A. K. |last2=Nanjundaswamy |first2=K. S. |last3=Goodenough |first3=J. B. |date=April 1997 |title=Phospho‐olivines as Positive‐Electrode Materials for Rechargeable Lithium Batteries |work=Journal of The Electrochemical Society |volume=144 |issue=4 |pages=1188–1194 |bibcode=1997JElS..144.1188P |doi=10.1149/1.1837571 |doi-access=free}}</ref> Reversible extraction of lithium from {{chem|LiFePO|4}} and insertion of lithium into {{chem|FePO|4}} was demonstrated.  [[Neutron diffraction]] confirmed that LFP was able to ensure the security of large input/output current of lithium batteries.<ref>Nature Materials, 2008, 7, 707-711.</ref> Most production occurs in China, where iron sulfate and phosphoric acid react to produce iron phosphate, mixed with lithium carbonate and baked at {{cvt|700|C|F}}. Some production is in USA, using iron oxide.<ref>{{cite web |last1=Blois |first1=Matt |title=Lithium iron phosphate comes to America |url=https://cen.acs.org/energy/energy-storage-/Lithium-iron-phosphate-comes-to-America/101/i4 |website=Chemical & Engineering News |language=en |date=29 January 2023}}</ref>

The material can be produced by heating a variety of iron and lithium salts with phosphates or [[phosphoric acid]].  Many related routes have been described including those that use [[hydrothermal synthesis]].<ref>{{cite journal |doi=10.1016/j.jpowsour.2009.01.074 |issn=0378-7753 |volume=190 |issue=2 |pages=538–544 |last1=Jugović |first1=Dragana |last2=Uskoković |first2=Dragan |title=A review of recent developments in the synthesis procedures of lithium iron phosphate powders |work=Journal of Power Sources |access-date= |date=2009-05-15 |url=http://itn.sanu.ac.rs/opus4/files/1199/Jugovic%20et%20al_revised%20manuscript_doi_10%201016_jjpowsour200901074.pdf |bibcode=2009JPS...190..538J}}</ref>

==Physical and chemical properties==
In {{chem|LiFePO|4}}, lithium has a +1 charge, iron +2 charge balancing the −3 charge for phosphate.  Upon removal of Li, the material converts to the ferric form {{chem|FePO|4}}.<ref name= Love>{{cite journal|title=Review of {{chem|LiFePO|4}} phase transition mechanisms and new observations from X-ray absorption spectroscopy|author1=Love, Corey T.|author2=Korovina, Anna|author3=Patridge, Christopher J.|author4=Swider-Lyons|author5=Karen E.|author6=Twigg, Mark E.|author7=Ramaker, David E.|journal= Journal of the Electrochemical Society|year=2013|volume=160|issue=5|pages=A3153–A3161|doi=10.1149/2.023305jes|doi-access=free}}</ref>

The iron atom and 6 oxygen atoms form an [[octahedron|octahedral coordination sphere]], described as {{chem|FeO|6}}, with the Fe ion at the center. The phosphate groups, {{chem|PO|4}}, are tetrahedral. The three-dimensional framework is formed by the {{chem|FeO|6}} octahedra sharing O corners. Lithium ions reside within the octahedral channels in a zigzag manner. In [[crystallography]], this structure is thought to belong to the P<sub>mnb</sub> space group of the [[orthorhombic]] crystal system. The [[lattice constants]] are: ''a'' = 6.008&nbsp;Å, ''b'' = 10.334&nbsp;Å, and ''c'' = 4.693&nbsp;Å. The volume of the [[unit cell]] is 291.4&nbsp;Å<sup>3</sup>.

In contrast to two traditional cathode materials, {{chem|LiMnO|4}} and {{chem|LiCoO|2}}, lithium ions of {{chem|LiFePO|4}} migrate in the lattice's one-dimensional free volume. During charge/discharge, the lithium ions are extracted concomitant with oxidation of Fe:
:{{chem2 | LiFe^{II}PO4 <-> Fe^{III}PO4 + Li+ + e- }}

Extraction of lithium from {{chem|LiFePO|4}} produces {{chem|FePO|4}} with a similar structure. {{chem|FePO|4}} adopts a P<sub>mnb</sub> space group with a unit cell volume of 272.4&nbsp;Å<sup>3</sup>, only slightly smaller than that of its lithiated precursor. Extraction of lithium ions reduces the lattice volume, as is the case with lithium oxides. {{chem|LiFePO|4}}'s corner-shared {{chem|FeO|6}} octahedra are separated by the oxygen atoms of the {{chem|PO|4|3-}} tetrahedra and cannot form a continuous {{chem|FeO|6}} network, reducing conductivity.

A nearly close-packed hexagonal array of oxides centers provides relatively little free volume for {{chem|Li|+}} ions to migrate within.  For this reason, the [[conductivity (electrolytic)|ionic conductivity]] of {{chem|Li|+}} is relatively low at ambient temperature.  The details of the lithiation of {{chem|FePO|4}} and the delithiation of {{chem|LiFePO|4}} have been examined.  Two phases of the lithiated material are implicated.<ref name= Love/><ref>Malik, R.; Abdellahi, A.; Ceder, G., "A Critical Review of the Li Insertion Mechanisms in {{chem|LiFePO|4}} Electrodes", J. Electrochem. Soc. 2013, volume 160, pages A3179-A3197. {{doi|10.1149/2.029305jes}}</ref>

==Applications==
{{see also|lithium iron phosphate battery}}
LFP cells have an operating voltage of 3.3&nbsp;V, [[charge density]] of 170 mAh/g, high [[power density]], long cycle life and stability at high temperatures.<ref name="SciData8(2024)165">{{cite journal |last1=Chung |first1=Hsien-Ching |title=Charge and discharge profiles of repurposed LiFePO4 batteries based on the UL 1974 standard |journal=Scientific Data |date=2021-07-02 |volume=8 |issue=1 |page=165 |doi=10.1038/s41597-021-00954-3|pmid=34215731 |pmc=8253776 }}</ref>

LFP's major commercial advantages are that it poses few safety concerns such as overheating and explosion, as well as long cycle lifetimes, high power density and has a wider operating temperature range. Power plants and automobiles use LFP.<ref>[https://www.slideshare.net/ArunKumar2443/rechargeable-liion-batteries-based-on-olivinestructured-lifepo4-cathode-materials Rechargeable Li-ion batteries based on Olivine-structured (LiFePO4) cathode materials - Kumar et al.], Nov 15, 2015, retrieved April 1, 2020</ref><ref>{{Cite web|url=https://offgridham.com/2016/03/about-lifepo4-batteries/|title=What You Need To Know About LiFePO4 Batteries.|first=Chris|last=Warren|date=March 12, 2016}}</ref>

BAE has announced that their HybriDrive Orion 7 hybrid bus uses about 180&nbsp;kW LFP battery cells.  [[AES Corporation|AES]] has developed multi-trillion watt battery systems that are capable of subsidiary services of the power network, including spare capacity and frequency adjustment.  In China, BAK and Tianjin Lishen are active in the area.

The safety is a crucial property for certain applications. For example, in 2016 an LFP-based energy storage system was installed in [[Paiyun Lodge]] on [[Yu Shan|Mt.Jade (Yushan)]] (the highest alpine lodge in [[Taiwan]]). As of 2024, the system is still operating safely.{{r|Batteries10(2024)202}}

=== Comparison ===
Although LFP has 25% less specific energy (Wh/g) than lithium batteries with [[oxide]] (e.g. nickel-cobalt-manganese, NCM)  cathode materials, primarily due to its operational voltage (3.2 volts vs 3.7 for NCM-type cathode chemistries), it has 70% more than [[Nickel–hydrogen battery|nickel-hydrogen batteries]].

The major differences between LFP batteries and other lithium-ion battery types is that LFP batteries contain no [[cobalt]] (removing ethical and economic questions about cobalt's availability) and have a flat discharge curve.

LFP batteries have drawbacks, originating from a high electronic [[resistivity]] of LFP, as well as the lower maximum charge/discharge voltage. The [[energy density]] is significantly lower than {{chem|LiCoO|2}} (although higher than the [[nickel–metal hydride battery]]).

Lithium cobalt oxide based battery chemistries are more prone to thermal runaway if overcharged and cobalt is both expensive and not widely geographically available. Other chemistries such as nickel-manganese-cobalt (NMC) have supplanted LiCo chemistry cells in most applications. The original ratio of Ni to Mn to Co was 3:3:3, whereas today, cells are being made with ratios of 8:1:1 or 6:2:2, whereby the Co content has been drastically reduced.

LiFePO<sub>4</sub> batteries are comparable to [[sealed lead acid batteries]] and are often being touted as a drop-in replacement for lead acid applications. The most notable difference between lithium iron phosphate and lead acid is the fact that the lithium battery capacity shows only a small dependence on the discharge rate. With very high discharge rates, for instance 0.8C, the capacity of the lead acid battery is only 60% of the rated capacity. Therefore, in cyclic applications where the discharge rate is often greater than 0.1C, a lower rated lithium battery will often have a higher actual capacity than the comparable lead acid battery. This means that at the same capacity rating, the lithium will cost more, but a lower capacity lithium battery can be used for the same application at a lower price. The cost of ownership when considering the lifecycle further increases the value of the lithium battery when compared to a lead acid battery.<ref>{{Cite web|title = Lead Acid Vs LiFePO4 Batteries|url = https://www.power-sonic.com/blog/lithium-vs-lead-acid-batteries/|website = Power Sonic - Trusted Battery Solutions|date = 25 February 2020}}</ref><ref>{{Cite web |last=Mongird |first=Kendall |last2=Viswanathan |first2=Vilayanur |last3=Baxter |first3=Josh |last4=Alam |first4=Md Sakib |date=2022-12-01 |title=2022 Grid Energy Storage Technology Cost and Performance Assessment |url=https://www.energy.gov/sites/default/files/2022-12/2022%20Grid%20Energy%20Storage%20Technology%20Cost%20and%20Performance%20Assessment.pdf |url-status=live |access-date=2025-05-31 |website=U.S. Department of Energy |quote=Li-ion batteries continue to dominate grid-scale energy storage deployment due to their high efficiency, long cycle life, and decreasing cost; lifetime cost of ownership is typically lower than that of lead-acid batteries.}}</ref>, but they have much poorer performance at lower temperatures, as covered in the section on [[Lithium iron phosphate#Effects of temperature|effects of temperature]].

==Intellectual property==
{{More citations needed|section|small=y|find=LiFePO4 patent lawsuits|date=September 2024}}
There are 4 groups of patents on LFP battery materials:

# The [[University of Texas at Austin]] (UT) patented the materials with the crystalline structure of LiFePo4 and their use in batteries.
# [[Hydro-Québec]], [[Université de Montréal]] and the [[French National Center for Scientific Research]] (CNRS) own patents, that claim improvements of the original LiFePo4 by  carbon coating that enhance its conductivity.<ref>{{Cite web|url=https://www.clariant.com/pt/Corporate|title=Especialidades químicas da Clariant|first=Clariant Ltd|last=Basel|website=Clariant Ltd.}}</ref>
# The key feature of {{chem|Li|1−''x''|MFePO|4}} from [[A123 Systems]] is the nano-LFP, which modifies its physical properties and adds noble metals in the anode, as well as the use of special graphite as the cathode.
# The main feature of {{chem|LiMPO|4}} from Phostech is increased capacitance and conductivity by an appropriate carbon coating. The special feature of {{chem|LiFePO|4}} • zM from Aleees a high capacitance and low impedance obtained by the stable control of the ferrites and crystal growth. This improved control is realized by applying strong mechanical stirring forces to the precursors in high oversaturation states, which induces crystallization of the metal oxides and LFP.

These patents underlie mature mass production technologies. The largest production capacity is up to 250 tons per month. 

In patent lawsuits in the US in 2005 and 2006, UT and Hydro-Québec claimed that {{chem|LiFePO|4}} as the cathode infringed their patents, {{patent|US|5910382}} and {{patent|US|6514640}}. The patent claims involved a unique crystal structure and a chemical formula of the battery cathode material.

On April 7, 2006, A123 filed an action seeking a declaration of non-infringement and invalidity UT's patents. A123 separately filed two [[ex parte]] Reexamination Proceedings before the [[United States Patent and Trademark Office]] (USPTO), in which they sought to invalidate the patents based upon prior art.

In a parallel court proceeding, UT sued [[Valence Technology]], a company that commercializes LFP products that alleged infringement.

The USPTO issued a Reexamination Certificate for the '382 patent on April 15, 2008, and for the '640 patent on May 12, 2009, by which the claims of these patents were amended. This allowed the current patent infringement suits filed by Hydro-Quebec against Valence and A123 to proceed. After a Markman hearing, on April 27, 2011, the Western [[District Court of Texas]] held that the claims of the reexamined patents had a narrower scope than as originally granted. The key question was whether the earlier [[John B. Goodenough|Goodenough]]'s patents from the UT (licensed to Hydro-Quebec) were infringed by A123, that had its own improved versions of LiFePO4 patents, that contained [[cobalt]] dopant. The end results was licensing of Goodenough's patents by A123 under undisclosed terms.<ref>{{cite journal |last1=Taylor |first1=E. Jennings |last2=Inman |first2=Maria |title=Looking at Patent Law: Patenting a Unitized Regenerative Fuel Cell System for Space Energy Storage Applications--A Case Study |journal=The Electrochemical Society Interface |date=1 March 2020 |volume=29 |issue=1 |pages=37–42 |url=https://iopscience.iop.org/article/10.1149/2.F04201IF/pdf |doi=10.1149/2.F04201IF|doi-access=free }}</ref>

On December 9, 2008, the [[European Patent Office]] revoked Dr. Goodenough’s patent numbered 0904607. This decision basically reduced the patent risk of using LFP in European automobile applications. The decision is believed to be based on the lack of novelty.<ref>{{Cite web | url=http://www.greencarcongress.com/2008/12/epo-revokes-uni.html | title=EPO Revokes Univ. Of Texas European Patent on Lithium Metal Phosphates; Boon for Valence}}</ref>

The first major settlement was the lawsuit between [[Nippon Telegraph and Telephone|NTT]] and the UT. In October 2008,<ref>{{Cite web | url=http://techon.nikkeibp.co.jp/english/NEWS_EN/20081007/159256/ |title = NTT Settles Lawsuit over Li-ion Battery Patents}}</ref> NTT announced that they would settle the case in the Japan Supreme Civil Court for $30 million. As part of the agreement, UT agreed that NTT did not steal the information and that NTT would share its LFP patents with UT. NTT’s patent is also for an olivine LFP, with the general chemical formula of {{chem|A|''y''|MPO|4}} (A is for alkali metal and M for the combination of Co and Fe), now used by [[BYD Company]]. Although chemically the materials are nearly the same, from the viewpoint of patents, {{chem|A|''y''|MPO|4}} of NTT is different from the materials covered by UT. {{chem|A|''y''|MPO|4}} has higher capacity than {{chem|LiMPO|4}}.  At the heart of the case was that NTT engineer Okada Shigeto, who had worked in the UT labs developing the material, was accused of stealing UT’s [[intellectual property]].

As of 2020, an organization named [https://www.lifepo4ag.com LifePO+C] claims to own the key IP and offers licenses. It is a consortium between Johnson Matthey, the CNRS, University of Montreal, and Hydro Quebec.

==Research==

=== Power density ===
LFP has two shortcomings: low conductivity (high overpotential) and low lithium diffusion constant, both of which limit the charge/discharge rate. Adding conducting particles in delithiated {{chem|FePO|4}} raises its electron conductivity. For example, adding conducting particles with good diffusion capability like graphite and carbon<ref name="Cramer-2004">{{cite journal |last1=Deb |first1=Aniruddha |last2=Bergmann |first2=Uwe |last3=Cairns |first3=Elton J. |last4=Cramer |first4=Stephen P. |title=Structural Investigations of LiFePO 4 Electrodes by Fe X-ray Absorption Spectroscopy |journal=The Journal of Physical Chemistry B |date=June 2004 |volume=108 |issue=22 |pages=7046–7051 |doi=10.1021/jp036361t}}</ref> to {{chem|LiMPO|4}} powders significantly improves conductivity between particles, increases the efficiency of {{chem|LiMPO|4}} and raises its reversible capacity up to 95% of the theoretical values. However, addition of conductive additives also increases the "dead mass" present in the cell that does not contribute to energy storage. {{chem|LiMPO|4}} shows good cycling performance even under charge/discharge current as large as 5C.<ref name="Wokaun-2005">{{cite journal |last1=Haas |first1=O. |last2=Deb |first2=A. |last3=Cairns |first3=E. J. |last4=Wokaun |first4=A. |title=Synchrotron X-Ray Absorption Study of LiFePO[sub 4] Electrodes |journal=Journal of the Electrochemical Society |date=2005 |volume=152 |issue=1 |pages=A191 |doi=10.1149/1.1833316}}</ref>

=== Stability ===
Coating LFP with inorganic oxides can make LFP’s structure more stable and increase conductivity. Traditional {{chem|LiCoO|2}} with oxide coating shows improved cycling performance. This coating also inhibits dissolution of Co and slows the decay of {{chem|LiCoO|2}} capacity. Similarly, {{chem|LiMPO|4}} with an inorganic coating such as [[ZnO]]<ref name="Lee-2004">{{cite journal |last1=Kwon |first1=Sang Jun |last2=Kim |first2=Cheol Woo |last3=Jeong |first3=Woon Tae |last4=Lee |first4=Kyung Sub |title=Synthesis and electrochemical properties of olivine LiFePO4 as a cathode material prepared by mechanical alloying |journal=Journal of Power Sources |date=October 2004 |volume=137 |issue=1 |pages=93–99 |doi=10.1016/j.jpowsour.2004.05.048|bibcode=2004JPS...137...93K }}</ref> and [[ZrO2|{{chem|ZrO|2}}]],<ref name="Jamnik-2006">{{cite journal |last1=Dominko |first1=R. |last2=Bele |first2=M. |last3=Gaberscek |first3=M. |last4=Remskar |first4=M. |last5=Hanzel |first5=D. |last6=Goupil |first6=J.M. |last7=Pejovnik |first7=S. |last8=Jamnik |first8=J. |title=Porous olivine composites synthesized by sol–gel technique |journal=Journal of Power Sources |date=February 2006 |volume=153 |issue=2 |pages=274–280 |doi=10.1016/j.jpowsour.2005.05.033|bibcode=2006JPS...153..274D }}</ref> has a better cycling lifetime, larger capacity and better characteristics under rapid discharge. The addition of a conductive carbon increases efficiency. [[Mitsui]] Zosen and Aleees reported that addition of conducting metal particles such as copper and silver increased efficiency.<ref name="Tessier-2008">{{cite journal |last1=León |first1=B. |last2=Vicente |first2=C. Pérez |last3=Tirado |first3=J. L. |last4=Biensan |first4=Ph. |last5=Tessier |first5=C. |title=Optimized Chemical Stability and Electrochemical Performance of LiFePO[sub 4] Composite Materials Obtained by ZnO Coating |journal=Journal of the Electrochemical Society |date=2008 |volume=155 |issue=3 |pages=A211–A216 |doi=10.1149/1.2828039}}</ref> {{chem|LiMPO|4}} with 1 wt% of metal additives has a reversible capacity up to 140 mAh/g and better efficiency under high discharge current.

===Metal substitution===
Substituting other materials for the iron or lithium in {{chem|LiMPO|4}} can also raise efficiency. Substituting zinc for iron increases crystallinity of {{chem|LiMPO|4}} because zinc and iron have similar ionic radii.<ref name="Liu-2008">{{cite journal |last1=Liu |first1=H. |last2=Wang |first2=G.X. |last3=Wexler |first3=D. |last4=Wang |first4=J.Z. |last5=Liu |first5=H.K. |title=Electrochemical performance of LiFePO4 cathode material coated with ZrO2 nanolayer |journal=Electrochemistry Communications |date=January 2008 |volume=10 |issue=1 |pages=165–169 |doi=10.1016/j.elecom.2007.11.016}}</ref> [[Cyclic voltammetry]] confirms that {{chem|LiFe|1−''x''|M|''x''|PO|4}}, after metal substitution, has higher reversibility of lithium ion insertion and extraction. During lithium extraction, Fe (II) is oxidized to Fe (III) and the lattice volume shrinks. The shrinking volume changes lithium’s returning paths.

===Synthesis processes===
Mass production with stability and high quality still faces many challenges.

Similar to lithium oxides, {{chem|LiMPO|4}} may be synthesized by a variety of methods, including: [[solid-phase synthesis]], emulsion drying, [[sol-gel process]], solution coprecipitation, [[Thin-film deposition|vapor-phase deposition]], electrochemical synthesis, [[electron beam]] irradiation, Microwave-assisted synthesis(Applies microwave energy to accelerate chemical reactions, resulting in reduced synthesis time and energy consumption.)<ref>{{Cite web |last=Jugović |first=Dragana |last2=Uskoković |first2=Dragan |date=2009-04-20 |title=A review of recent developments in the synthesis procedures of lithium iron phosphate powders |url=https://web.mit.edu/~elsao/www/Articles/2009Jugovic%20A%20review%20of%20recent%20developments%20in%20the%20synthesis%20procedures%20of%20lithium%20iron%20phosphate%20powders.pdf |url-status=live |access-date=2025-05-30 |website=Journal of Power Sources |quote=Most recent researches see microwave-assisted synthesis as a promising approach to mass LiFePO4 production at low-energy cost for HEV application, starting from a solid mixture of Li3PO4, Fe3(PO4)2·8H2O, carbon, and glucose.}}</ref>, hydrothermal synthesis, ultrasonic [[pyrolysis]] and [[spray pyrolysis]].

In the emulsion drying process, the emulsifier is first mixed with kerosene. Next, the solutions of lithium salts and iron salts are added to this mixture. This process produces nanocarbon particles.<ref name="Scrosati-2002">{{cite journal |last1=Croce |first1=F. |last2=D' Epifanio |first2=A. |last3=Hassoun |first3=J. |last4=Deptula |first4=A. |last5=Olczac |first5=T. |last6=Scrosati |first6=B. |title=A Novel Concept for the Synthesis of an Improved LiFePO[sub 4] Lithium Battery Cathode |journal=Electrochemical and Solid-State Letters |date=2002 |volume=5 |issue=3 |pages=A47–A50 |doi=10.1149/1.1449302|doi-access=free }}</ref> Hydrothermal synthesis produces {{chem|LiMPO|4}} with good crystallinity. Conductive carbon is obtained by adding [[polyethylene glycol]] to the solution followed by thermal processing.<ref name="Zhang-2005">{{cite journal |last1=Ni |first1=J.F. |last2=Zhou |first2=H.H. |last3=Chen |first3=J.T. |last4=Zhang |first4=X.X. |title=LiFePO4 doped with ions prepared by co-precipitation method |journal=Materials Letters |date=August 2005 |volume=59 |issue=18 |pages=2361–2365 |doi=10.1016/j.matlet.2005.02.080}}</ref> Vapor phase deposition produces a thin film {{chem|LiMPO|4}}.<ref name="Chung-2004">{{cite journal |last1=Cho |first1=Tae-Hyung |last2=Chung |first2=Hoon-Taek |title=Synthesis of olivine-type LiFePO4 by emulsion-drying method |journal=Journal of Power Sources |date=June 2004 |volume=133 |issue=2 |pages=272–276 |doi=10.1016/j.jpowsour.2004.02.015|bibcode=2004JPS...133..272C }}</ref> In flame spray pyrolysis FePO<sub>4</sub> is mixed with [[lithium carbonate]] and [[glucose]] and charged with [[electrolytes]]. The mixture is then injected inside a flame and filtered to collect the synthesized {{chem|LiFePO|4}}.<ref name="Wiggers-2012">{{cite journal |last1=Hamid |first1=N.A. |last2=Wennig |first2=S. |last3=Hardt |first3=S. |last4=Heinzel |first4=A. |last5=Schulz |first5=C. |last6=Wiggers |first6=H. |title=High-capacity cathodes for lithium-ion batteries from nanostructured LiFePO4 synthesized by highly-flexible and scalable flame spray pyrolysis |journal=Journal of Power Sources |date=October 2012 |volume=216 |pages=76–83 |doi=10.1016/j.jpowsour.2012.05.047|bibcode=2012JPS...216...76H }}</ref>

===Effects of temperature===
The effects of temperature on lithium iron phosphate batteries can be divided into the effects of high temperature and low temperature.

Generally, LFP chemistry batteries are less susceptible to thermal runaway reactions like those that occur in lithium cobalt batteries; LFP batteries exhibit better performance at an elevated temperature. Research has shown that at room temperature (23&nbsp;°C), the initial capacity loss approximates 40-50&nbsp;mAh/g. However, at 40&nbsp;°C and 60&nbsp;°C, the capacity losses approximate 25 and 15&nbsp;mAh/g respectively, but these capacity losses were spread over 20 cycles instead of a bulk loss like that in the case of room temperature capacity loss.<ref>{{cite journal |title=Thermal Stability of LiFePO4 -Based Cathodes |journal=Electrochemical and Solid-State Letters |year=2000 |last1=Andersson |first1=Anna S |last2=Thomas |first2=John O |last3=Kalska |first3=Beata |last4=Häggström |first4=Lennart |volume=3 |issue=2 |pages=66–68 |doi=10.1149/1.1390960 |url=https://iopscience.iop.org/article/10.1149/1.1390960 |accessdate=2021-11-18 |url-access=subscription }}</ref>

However, this is only true for a short cycling timeframe. Later yearlong study has shown that despite LFP batteries having double the equivalent full cycle, the capacity fade rate increased with increasing temperature for LFP cells but the increasing temperature does not impact NCA cells or have a negligible impact on the aging of NMC cells.<ref>{{cite journal |title=Degradation of Commercial Lithium-Ion Cells as a Function of Chemistry and Cycling Conditions |journal=Journal of the Electrochemical Society |year=2020 |last1=Preger |first1=Yulia |last2=Barkholtz |first2=Heather M. |last3=Fresquez |first3=Armado |last4=Campbell |first4=Danel L. |last5=Juba |first5=Benjamin W. |volume=167 |issue=12 |page=120532 |doi=10.1149/1945-7111/abae37 |bibcode=2020JElS..167l0532P |s2cid=225506214 |doi-access=free |osti=1650174 |url=https://www.osti.gov/biblio/1650174 }}</ref> This capacity fade is primarily due to the [[Lithium–silicon battery#Solid electrolyte interphase layer|solid electrolyte interface]] (SEI) formation reaction being accelerated by increasing temperature.

LFP batteries are especially affected by decreasing temperature which possibly hamper their application in high-latitude areas. The initial discharge capacities for LFP/C samples at temperatures of 23, 0, -10, and -20&nbsp;°C are 141.8, 92.7, 57.9 and 46.7&nbsp;mAh/g with [[coulombic efficiency]] 91.2%, 74.5%, 63.6% and 61.3%. These losses are accounted for by the slow diffusion of lithium ions within electrodes and the formation of SEI that come with lower temperatures which subsequently increase the charge-transfer resistance on the electrolyte-electrode interfaces.<ref>{{cite journal |title=A comparative study on the low-temperature performance of LiFePO4/C and Li3V2(PO4)3/C cathodes for lithium-ion batteries |journal=Journal of Power Sources |date=February 2011 |last1=Rui |first1=X.H. |last2=Jin |first2=Y. |last3=Feng |first3=X.Y. |last4=Zhang |first4=L.C. |last5=Chen |first5=C.H. |volume=196 |issue=4 |pages=2109–2114 |issn=0378-7753 |doi=10.1016/j.jpowsour.2010.10.063 |url=https://linkinghub.elsevier.com/retrieve/pii/S037877531001863X |accessdate=2021-11-18 |url-access=subscription }}</ref> Another possible cause of the lowered capacity formation is lithium plating. As mentioned above, low temperature lowers the diffusion rate of lithium ions within the electrodes, allowing for the lithium plating rate to compete with that of intercalation rate. The colder condition leads to higher growth rates and shifts the initial point to lower state of charge which means that the plating process starts earlier.<ref>{{cite journal |title=Nondestructive detection, characterization, and quantification of lithium plating in commercial lithium-ion batteries |journal=Journal of Power Sources |date=May 2014 |last1=Petzl |first1=Mathias |last2=Danzer |first2=Michael A. |volume=254 |pages=80–87 |issn=0378-7753 |doi=10.1016/j.jpowsour.2013.12.060 |bibcode=2014JPS...254...80P |url=https://linkinghub.elsevier.com/retrieve/pii/S0378775313020387 |accessdate=2021-11-18 |url-access=subscription }}</ref> Lithium plating uses up lithium which then compete with the intercalation of lithium into graphite, decreasing the capacity of the batteries. The aggregated lithium ions are deposited on the surface of electrodes in the form of “plates” or even dendrites which may penetrate the separators, short-circuiting the battery completely.<ref>{{cite journal |title=Thermal issues about Li-ion batteries and recent progress in battery thermal management systems: A review |journal=Energy Conversion and Management |date=October 2017 |last1=Liu |first1=Huaqiang |last2=Wei |first2=Zhongbao |last3=He |first3=Weidong |last4=Zhao |first4=Jiyun |volume=150 |pages=304–330 |issn=0196-8904 |doi=10.1016/j.enconman.2017.08.016 |bibcode=2017ECM...150..304L |url=https://linkinghub.elsevier.com/retrieve/pii/S0196890417307288 |accessdate=2021-11-18 |url-access=subscription }}</ref>

==See also==
*[[Lithium iron phosphate battery]]
*[[A123 Systems]]
*[[Valence Technology]]

==References==
{{Reflist|30em}}

{{lithium compounds}}
{{iron compounds}}
{{Phosphates}}

{{DEFAULTSORT:Lithium Iron Phosphate}}
[[Category:Lithium compounds]]
[[Category:Iron(II) compounds]]
[[Category:Phosphates]]
[[Category:Rechargeable batteries]]