United States Patent (19) 11 Patent Number: 5,993,767 Willmann Et Al
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USOO5993767A United States Patent (19) 11 Patent Number: 5,993,767 Willmann et al. (45) Date of Patent: Nov.30, 1999 54). SOLVATE OF LITHIUM 5,378,445 1/1995 Salmon et al. .......................... 423/301 HEXAFLUOROPHOSPHATE AND PYRIDINE, 5,616,636 4/1997 Avar et al. ................................ 546/22 ITS PREPARATION AND PREPARATION FOREIGN PATENT DOCUMENTS PROCESS FOR LITHIUM HEXAFLUOROPHOSPHATE USING SAD 20 26 110 12/1970 Germany. SOLVATE OTHER PUBLICATIONS 75 Inventors: Patrick Willmann, Montgiscard; Chemical Abstracts, vol. 100, No. 21, 21 Mai 1984, Colum Régine Naejus, Tours; Robert bus, Ohio, US; abstract no 174608c, Mohamed, K. er at..: Coudert, Notre Dame D'Oe; Daniel “pyridinium poly (hydrogen fluoride)—a reagent for the Lemordant, Orsay, all of France preparation of hexafluorophosphates' XP002024671. 73 Assignee: Centre National D’Etudes Spatiales, Primary Examiner Wayne Langel France Attorney, Agent, or Firm-Burns, Doane, Swecker & Mathis, L.L.P. 21 Appl. No.: 09/000,232 57 ABSTRACT 22 PCT Filed: Jun. 18, 1997 The invention relates to a lithium hexafluorophosphate Sol 86 PCT No.: PCT/FR97/01097 Vate usable for the preparation of high purity lithium S371 Date: Jan. 23, 1998 hexafluorophosphate. S 102(e) Date: Jan. 23, 1998 This solvate of lithium hexafluorophosphate and pyridine 87 PCT Pub. No.: WO97/48709 complies with the formula: PCT Pub. Date: Dec. 24, 1997 30 Foreign Application Priority Data and is prepared by a proceSS comprising the following Stages: Jun. 19, 1996 FR France ................................... 96 O7623 a) preparation of pyridinium hexafluorophosphate of for 511 Int. Cl.CI. ......................... C01B 25/105/10; CO7D 213/20; mula CH-NHPF by the neutralization of hexafluoro CO7F 9/28 phosphoric acid HPF with pyridine and 52 U.S. Cl. ............................. 423/301; 546/22; 546/347 b) conversion of the pyridinium hexafluorophosphate into 58 Field of Search ............................... 423/301; 546/22, Solvate LiPF, CHN by exchange with a lithium 546/347 compound chosen from among lithium hydroxide, lithium alkoxides and alkyl-lithiums. 56) References Cited The LiPF can be regenerated from the Solvate by vacuum U.S. PATENT DOCUMENTS decomposition. 3,654,330 4/1972 Wiesboeck. 4,996,320 2/1991 Omemoto et al. ........................ 546/22 14 Claims, 7 Drawing Sheets % TRANSMISSION A 4.0 1633 U.S. Patent Nov.30, 1999 Sheet 1 of 7 5,993,767 U.S. Patent Nov.30, 1999 Sheet 2 of 7 5,993,767 % TRANSMSSION 25 15 10 5 673.09 557.71 O (cm1) 2OOO 16OO 1200 8OO 400 U.S. Patent Nov.30, 1999 Sheet 3 of 7 5,993,767 000€ 009Z 000Z 000|| 009 G/|0 09||'0 OGO’0 000’0 U.S. Patent Nov.30, 1999 Sheet 4 of 7 5,993,767 9 SN U.S. Patent Nov.30, 1999 Sheet 5 of 7 5,993,767 9 SN U.S. Patent Nov.30, 1999 Sheet 6 of 7 5,993,767 area 8 C w 007 99°888 008 OOZ| OOOZ G’S 0"| U.S. Patent Nov.30, 1999 Sheet 7 of 7 5,993,767 als - S O Ye' 007 89°199 009 86°188 Z| 0|| 5,993,767 1 2 SOLVATE OF LITHIUM Thus, none of the presently known processes makes it HEXAFLUOROPHOSPHATE AND PYRIDINE, possible to prepare high purity lithium hexafluorophosphate ITS PREPARATION AND PREPARATION LiPF under easily implementable conditions and without PROCESS FOR LITHIUM using onerous reagents. HEXAFLUOROPHOSPHATE USING SAD DESCRIPTION OF THE INVENTION SOLVATE The present invention relates to the preparation of high DESCRIPTION purity LiPF by a simple, uncomplicated process using inexpensive, commercial products, with as the intermediate 1. Technical Field a Solvate of lithium hexafluorophosphate and pyridine. It The invention relates to a novel compound constituted by also relates to the Solvate and its preparation process. a Solvate of lithium hexafluorophosphate and pyridine uSable for the preparation of lithium hexafluorophosphate. The Solvate complies with the formula: It more particularly applies to the preparation of lithium Li(CHN)PF hexafluorophosphate used as an electrolyte in lithium 15 and has the advantage of being much easier to handle than carbon batteries. LiPF, because it is stable in air at ambient temperature, At present lithium batteries are being extensively devel whereas LiPF decomposes into PFs and LiF and must be oped for various applications, particularly in electric manipulated in a glove box. It also makes it possible to vehicles, portable equipments Such as portable telephones generate LiPF with a high purity level of 99.8% using and cameScopes, as well as in Space. These batteries use an Simple processes. electrolyte constituted by one or more organic Solvents According to the invention, this Solvate can be prepared containing in Solution a lithium Salt. Among the uSable by a process comprising the following Stages: lithium salts, lithium hexafluorophosphate (LiPF) is at a) preparation of pyridinium hexafluorophosphate of for present the most widely used, due to its high Solubility in mula CH-NHPF by neutralization of hexafluorophos organic Solvents, its conductivity and its Safety. 25 phoric acid HPF with pyridine using the stoichiomet 2. Prior Art ric quantity permitting the neutralization of only the The conventional method for the preparation of LiPF HPF and not the other acid impurities present in the consists of reacting PFs with LiF in anhydrous hydrofluoric Starting acid and acid, but the purity of LiPF prepared in this way is only 90 b) conversion of pyridinium hexafluorophosphate into to 95%, whereas purities of at least 99% are required for use Solvate LiPF, CHN by exchange with a lithium in a lithium battery in order to satisfy the LiPF storage compound chosen from among lithium hydroxide, Stability and Solubility requirements. lithium alkoxides and alkyl-lithiums. In this process, the first stage a) is easy to perform, In order to overcome this difficulty, it is still possible to because it can be carried out in an aqueous medium at obtain LiPF of higher purity by the process described in 35 ambient temperature from an inexpensive, commercial prod U.S. Pat. No. 3,654,330. According to this process, lithium uct (HPF in aqueous Solution). Moreover, through using the fluoride, anhydrous hydrofluoric acid and phosphorus pen precise Stoichiometric quantity corresponding to the neu tafluoride PFs are reacted to obtain impure LiPF, which is tralization of HPF and excluding other acid impurities then purified by reaction with acetonitrile. Thus, tetraaceto present in the Starting product, it is possible to obtain high nitrilolithium hexafluorophosphate Li(CHCN), PF is 40 purity pyridinium hexafluorophosphate, which will then lead produced, which then regenerates lithium hexafluorophoS to a high purity solvate Li(CHN)PF. phate by heating in a partial vacuum. It is also possible to This Stoichiometric quantity can be easily determined by directly produce Li(CHCN), PF by reacting PF in a carrying out before hand a neutralization test on the com Suspension of LiF in acetonitrile. mercial acid HPF used as the Starting product and moni This process makes it possible to obtain high purity 45 toring the neutralization by conductometry. lithium hexafluorophosphate, but it suffers from the disad It has in fact been found that HPF is stronger than the vantage of requiring the use of PF which is a very difficult other acids present as impurities in commercial Solutions product. and is neutralized first giving rise to a rapid conductivity Another way for obtaining alkali metal hexafluorophoS drop of the solution. The end of this drop corresponds to the phates has been investigated by Syed Mohamed et al in J. 50 complete neutralization of HPF and it is thus possible to Fluorine Chem., 23, 1983, pp 509-514. According to this determine the basic Stoichiometric quantity necessary for document, the Starting product is pyridinium hexafluoro this neutralization. phosphate CH-NHPF, which is then treated with an This method for preparing CH-NHPF is much easier to ammonium or alkali metal hydroxide in an aqueous implement than that described by Syed Mohamed in J. medium, but this process has not made it possible to isolate 55 Fluorine Chem., 23, 1983, pp 509-514, where said pyri solid LiPF from said medium. Moreover, the preparation of dinium hexafluorophosphate is obtained by a two-stage the starting product CH-NHPF involves a low temperature reaction, firstly preparing a poly(hydrogen fluoride)- reaction (-80 C.) between the pyridine and the anhydrous pyridinium reagent at a temperature of -80 C., followed by hydrofluoric acid, followed by the reaction of the product the reaction of Said reagent with dropwise added phosphoryl obtained with phosphoryl chloride. This involves difficult 60 chloride. performance using expensive reagents (POCL), which is The first stage of the proceSS according to the invention is difficult to carry out on an industrial Scale. easier to perform, because it is carried out in an aqueous Lange et al in BER. 63B, 1058–70, 1930 describe the Solution at ambient temperature. It also makes use of uncom preparation of CH3NHPF by reacting pyridine in acetic plicated reagents, which are commercially available, Such as acid with ammonium hexafluorophosphate. However, they 65 HPF solutions in water. did not envisage using this pyridinium hexafluorophosphate In the Second stage b) of the process according to the for preparing lithium hexafluorophosphate. invention, the pyridinium hexafluorophosphate is converted 5,993,767 3 4 into Solvate Li(C5H5N)PF by exchange with a lithium illustrative and non-limitative manner, with reference to the compound. This Solvate has the major advantage of being, attached drawings. unlike LiPF, Stable at ambient temperature, permitting easier handling and Storage. BRIEF DESCRIPTION OF THE DRAWINGS According to a first embodiment of Said Stage, the lithium compound used is hydrated or unhydrated lithium FIG. 1 is a graph illustrating the conductometric dosage hydroxide, in an alcoholic medium, e.g.