Method for fabricating a silicate material having an olivine structure

Patent metadata

Field	Value
Publication number	US-2018097220-A1
Application number	US-201715701948-A
Country	US
Kind code	A1
Filing date	Sep 12, 2017
Priority date	Sep 12, 2016
Publication date	Apr 5, 2018
Grant date	—

Abstract

The present invention relates to a method for manufacturing a material of olivine crystallographic structure of formula (I) A a Z z M m SiO 4 in which A is chosen from Li, Na, K and mixtures thereof, Z is chosen from Be, Mg, Ca, Sr, Ba, and mixtures thereof, M is chosen from Fe, Ni, Co, Mn, Cr, and mixtures thereof, a, z and m are the stoichiometric coefficients, respectively, of A, Z and M, and satisfy the following conditions: z>0, m>0, a>0, a+z+m≦2, and 2≦(4−a−2z)/m<4, said method comprising at least the steps consisting in i. having a material of olivine crystallographic structure of formula (II) Z z M m SiO 4 , obtained by oxidation of a material of olivine crystallographic structure of formula (III) Z z′ M m SiO 4 , in which Z, M, z and m are as defined above and the stoichiometric index z′ is such that z′>z, and ii. electrochemically reducing said material of formula (II) in the presence of a source electrode made of element A under conditions that are suitable for forming the material of formula (I).

First claim

1 : A method for manufacturing a material of olivine crystallographic structure of formula (I):
A a Z z M m SiO 4 in which:
A is chosen from lithium (Li), sodium (Na), potassium (K), and mixtures thereof,
Z is chosen from beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and mixtures thereof,
M is chosen from iron (Fe), nickel (Ni), cobalt (Co), manganese (Mn), chromium (Cr), and mixtures thereof,
a, z and m are the stoichiometric coefficients, respectively, of A, Z and M, and which satisfy the following conditions:
z>0, m>0, a>0,
a+z+m≦2, and
2≦(4−a−2z)/m<4
said method comprising at least the steps consisting in:
i. having a material of olivine crystallographic structure of formula (II):
Z z M m SiO 4 ,

obtained by oxidation of a material of olivine crystallographic structure of formula (III):
Z z′ M m SiO 4 ,

in which Z, M, z and in are as defined above and the stoichiometric index z′ is such that z′>z, and
ii. electrochemically reducing said material of formula (II) in the presence of a source electrode made of element A under conditions that are suitable for forming the material of formula (I).

2 : The method according to claim 1 , in which a+z+m=2.

3 : The method according to claim 1 , in which z=1−a and/or m=1.

4 : The method according to claim 1 , in which z<0.5, preferably z<0.1, or even preferably z<0.05, better still z<0.01.

5 : The method according to claim 1 , in which Z is magnesium and/or M is manganese.

6 : The method according to claim 1 , in which A is lithium.

7 : The method according to claim 1 , wherein the material of formula (II) forms all or part of an electrode.

8 : The method according to claim 1 , wherein the electrochemical reduction is performed using an electrolytic medium comprising a source of element A.

9 : The method according to claim 8 , in which A is lithium and said electrolytic medium comprises a source of lithium, in particular in the form of a compound chosen from lithium hexafluorophosphate (LiPF 6 ), lithium perchlorate (LiClO 4 ), lithium arsenate (LiAsO 4 ), lithium tetrafluoroborate (LiBF 4 ), lithium bis(trifluoromethanesulfonimide) (LiTFSI), lithium bis(oxalato)borate (LiBOB), lithium bis(fluorosulfonyl)imide (LiFSI), lithium hexafluoroarsenate (LiAsF 6 ), lithium triflate (LiSO 3 CF 3 ), lithium trifluoroacetate (LiCF 3 CO 2 ), lithium hexafluoroantimonate (LiSbF 6 ), LiN(CF 3 SO 2 ) 3 , LiN(C 2 F 5 SO 2 ), and mixtures thereof.

10 : The method according to claim 1 , in which the material of formula (II) is, prior to its reduction, generated by electrochemical oxidation of the constituent element M of said material of formula (III).

11 : The method according to claim 1 , in which said material of formula (III) is oxidized as working electrode opposite a counterelectrode.

12 : The method according to claim 10 , in which said material of formula (III) is used in the form of an electrode Z z′ M m SiO 4 , in which Z, M, z′ and m are as defined in claims 1 to 4 , and preferably MgMnSiO 4 .

13 : The method according to claim 10 , in which the oxidation of the material of formula (III) to the material of formula (II) and the reduction of the material of formula (II) to the material of formula (I) are performed in one and the same electrochemical cell.

14 : The method according to claim 10 , in which the oxidation of the material of formula (III) to the material of formula (II) and the reduction of the material of formula (II) to the material of formula (I) are performed at a single electrode of which said materials of formulae (III) and (II) are consecutively a component.

15 : The method according to claim 10 , using at least one charging/discharging cycle.

16 : The method according to claim 1 , each cycle being constituted by the succession of electrochemical oxidation and electrochemical reduction steps.

17 : The method according to claim 1 , in which said material of formula (II) is generated beforehand by chemical oxidation of the material of formula (III).

18 : The method according to claim 17 , in which said chemical oxidation uses at least one oxidizing compound whose redox potential is greater than the redox potential of the M 2+ /M 3+ couple and/or of the M 3+ /M 4+ couple of the constituent element M of said material of formula (III).

19 : The method according to claim 18 , in which the oxidizing compound is chosen from nitronium tetrafluoroborate (NO 2 BF 4 ), potassium persulfate (K 2 S 2 O 8 ), nitrosonium hexafluorophosphate (NO 2 PF 6 ), nitrosonium tetrafluoroborate (NOBF 4 ), hydrogen peroxide (H 2 O 2 ), and mixtures thereof.

20 : The method according to claim 17 , in which said chemical oxidation is performed in a liquid bath containing at least said material of formula (III) and said oxidizing compound under conditions suitable for extracting the element Z from said material of formula (III) to form said expected material of formula (I).

21 : An electrode material obtained via the method according to claim 1 .

Assignees

• Commissariat Energie Atomique

Inventors

• Lefevre Guillaume
• Ducros Jean-Baptiste
• Martinet Sebastien

Classifications

• C01P2002/30

  Three-dimensional structures · CPC title

• C01P2006/40

  Electric properties · CPC title

• H01M4/5825

  Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines · CPC title

• H01M4/485

  of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy (H01M4/505, H01M4/525 take precedence) · CPC title

• C01B33/32

  Alkali metal silicates ({C01B33/24} , C01B33/26 take precedence) · CPC title