Low flammability electrolytes for stable operation of lithium and sodium ion batteries

Patent metadata

Field	Value
Publication number	US-2019123390-A1
Application number	US-201816119641-A
Country	US
Kind code	A1
Filing date	Aug 31, 2018
Priority date	Oct 19, 2017
Publication date	Apr 25, 2019
Grant date	—

Abstract

Low flammability and nonflammable localized superconcentrated electrolytes (LSEs) for stable operation of lithium and sodium ion batteries are disclosed. Electrochemical devices including the low flammability and nonflammable LSEs are also disclosed. The low flammability and nonflammable LSEs include an active salt, a solvent comprising a flame retardant compound, wherein the active salt is soluble in the solvent, and a diluent in which the active salt is insoluble or poorly soluble. The LSE may further include a cosolvent, such as a carbonate, a sulfone, a sulfite, a sulfate, a carboxylate, an ether, a nitrogen-containing solvent, or any combination thereof. In certain embodiments, such as when the solvent and diluent are immiscible, the LSE further includes a bridge solvent.

First claim

We claim:

1 . An electrolyte, comprising:
an active salt; a solvent comprising (i) a flame retardant compound and (ii) a cosolvent comprising a carbonate, a carboxylate, an ether, a sulfone, a sulfite, a sulfate, a nitrile, water, or any combination thereof, wherein the active salt is soluble in the solvent; and a diluent, wherein the active salt has a solubility in the diluent at least 10 times less than a solubility of the active salt in the solvent, wherein the electrolyte comprises at least 5 wt. % of the flame retardant compound, and wherein the electrolyte is capable of forming a solid electrolyte interphase layer comprising inorganic components formed by decomposition of the active salon an anode during operation of a battery including the electrolyte.

2 . The electrolyte of claim 1 , wherein the cosolvent comprises a cyclic carbonate, an ether, a sulfone, a cyclic sulfite, a cyclic sulfate, or any combination thereof.

3 . The electrolyte of claim 1 , wherein the active salt comprises lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(pentafluoroethanesulfonyl)imide (LiBETI), lithium bis(oxalato)borate (LiBOB), LiPF 6 , LiAsF 6 , LiBF 4 , LiCF 3 SO 3 , LiClO 4 , lithium difluoro oxalato borate anion (LiDFOB), LiI, LiBr, LiCl, LiSCN, LiNO 3 , LiNO 2 , Li 2 SO 4 , sodium bis(fluorosulfonyl)imide (NaFSI), sodium bis(trifluoromethylsulfonyl)imide (NaTFSI), sodium bis(pentafluoroethanesulfonyl)imide (NaBETI), NaPF 6 , NaAsF 6 , NaBF 4 , NaCF 3 SO 3 , NaClO 4 , sodium bis(oxalato)borate (NaBOB), sodium difluoro oxalato borate anion (NaDFOB), or any combination thereof.

4 . The electrolyte of claim 1 , wherein the flame retardant compound comprises an organic phosphate, an organic phosphite, an organic phosphonate, an organic phosphoramide, a phosphazene, or any combination thereof.

5 . The electrolyte of claim 4 , wherein the flame retardant compound comprises trimethyl phosphate, triethyl phosphate, tributyl phosphate, triphenyl phosphate, tris(2,2,2-trifluoroethyl) phosphate, bis(2,2,2-trifluoroethyl) methyl phosphate; trimethyl phosphite, triphenyl phosphite, tris(2,2,2-trifluoroethyl) phosphite; dimethyl methylphosphonate, diethyl ethylphosphonate, diethyl phenylphosphonate, bis(2,2,2-trifluoroethyl) methylphosphonate; hexamethylphosphoramide; hexamethoxyphosphazene, hexafluorophosphazene, or any combination thereof.

6 . The electrolyte of claim 1 , wherein the cosolvent comprises ethylene carbonate (EC), dimethyl carbonate (DMC), 1,2-dimethoxyethane (DME), vinylene carbonate (VC), fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), trifluoroethylene carbonate (TFEC), vinyl ethylene carbonate (VEC), 4-methylene ethylene carbonate (MEC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), methyl 2,2,2-trifluoroethyl carbonate (MFEC), 4,5-dimethylene-1,3-dioxolan-2-one, dimethyl sulfoxide (DMSO), dimethyl sulfone (DMS), ethyl methyl sulfone (EMS), tetramethylene sulfone (TMS), ethyl vinyl sulfone (EVS), ethylene sulfite, ethylene sulfate, water, or any combination thereof.

7 . The electrolyte of claim 1 , wherein the cosolvent is present in the electrolyte in an amount of from 0.1-80 wt. %.

8 . The electrolyte of claim 1 , wherein the diluent comprises a hydrofluoroether, an aromatic compound, a hydrocarbon compound, or any combination thereof.

9 . The electrolyte of claim 8 , wherein the diluent comprises 1,1,2,2-tetrafluoroethyl-2,2,2,3-tetrafluoropropyl ether (TTE), bis(2,2,2-trifluoroethyl) ether (BTFE), 1 , 1 , 2 , 2 ,-tetrafluoroethyl-2,2,2-trifluoroethyl ether (TFTFE), methoxynonafluorobutane (MOFB), ethoxynonafluorobutane (EOFB), or any combination thereof.

10 . The electrolyte of claim 1 , wherein:
(i) the active salt has a molar concentration in the electrolyte within a range of from 0.1 M to 3M; or (ii) the active salt has a molar concentration in the electrolyte of greater than 3 moles of active salt per liter of the solvent; or (iii) the molar concentration of the active salt in the electrolyte is at least 20% less than a molar concentration of the active salt in the solvent in the absence of the diluent; or (iv) a molar ratio of the active salt to the solvent is within a range of from 0.1 to 5; or (v) a molar ratio of the solvent to the diluent is within a range of from 0.1 to 5; or (vi) any combination of (i), (ii), (iii), (iv), and (v).

11 . The electrolyte of claim 1 , wherein:
(i) at least 90% of molecules of the solvent are associated with cations of the active salt; or (ii) fewer than 10% of molecules of the diluent are associated with cations of the active salt; or (iii) both (i) and (ii).

12 . The electrolyte of claim 1 , wherein the diluent comprises a fluoroalkyl ether.

13 . The electrolyte of claim 12 , wherein the diluent comprises 1,1,2,2-tetrafluoroethyl-2,2,2,3-tetrafluoropropyl ether (TTE), bis(2,2,2-trifluoroethyl) ether (BTFE), 1,1,2,2,-tetrafluoroethyl-2,2,2-trifluoroethyl ether (TFTFE), methoxynonafluorobutane (MOFB), ethoxynonafluorobutane (EOFB), or any combination thereof.

14 . The electrolyte of claim 1 , wherein the solvent and the diluent are immiscible, the electrolyte further comprising a bridge solvent having a different composition than the solvent and a different composition than the diluent, wherein the bridge solvent is miscible with the solvent and with the diluent.

15 . The electrolyte of claim 14 , wherein the bridge solvent comprises acetonitrile, dimethyl carbonate, diethyl carbonate, propylene carbonate, dimethyl sulfoxide, 1,3-dioxolane, 1,2-dimethoxyethane, diglyme (bis(2-methoxyethyl) ether), triglyme (triethylene glycol dimethyl ether), tetraglyme (tetraethylene glycol dimethyl ether), or any combination thereof.

16 . A battery, comprising:
an electrolyte comprising
an active salt,
a solvent comprising a flame retardant compound, wherein the active salt is soluble in the solvent,
a diluent, wherein the active salt has a solubility in the diluent at least 10 times less than a solubility of the active salt in the solvent, the active salt has a concentration in the electrolyte within a range of 0.1 to 3 M, and the electrolyte comprises at least 5 wt. % of the flame retardant compound;
an anode comprising carbon, silicon, tin, antimony, or any combination thereof; and a cathode, wherein the battery has a coulombic efficiency ≥95%.

17 . The battery of claim 16 , wherein the solvent further comprises a cosolvent comprising a carbonate, a carboxylate, an ether, a sulfone, a sulfite, a sulfate, a nitrile, water, or any combination thereof, and wherein, during operation of the battery, a salt-derived solid electrolyte interphase layer is formed on the anode.

18 . The battery of claim 16 , wherein the flame retardant compound comprises trimethyl phosphate, triethyl phosphate, tributyl phosphate, triphenyl phosphate, tris(2,2,2-trifluoroethyl) phosphate, bis(2,2,2-trifluoroethyl) methyl phosphate; trimethyl phosphite, triphenyl phosphite, tris(2,2,2-trifluoroethyl) phosphite; dimethyl methylphosphonate, diethyl ethylphosphonate, diethyl phenylphosphonate, bis(2,2,2-trifluoroethyl) methylphosphonate; hexamethylphosphoramide; hexamethoxyphosphazene, hexafluorophosphazene, or any combination thereof.

19 . The battery of claim 16 , wherein:
the active salt comprises LiFSI, LiTFSI, LiBETI, LiPF 6 , LiAsF 6 , LiBF 4 , LiCF 3 SO 3 , LiClO 4 , LiBOB, LiDFOB, LiI, LiBr, LiCl, LiSCN, LiNO 3 , LiNO 2 , Li 2 SO 4 , or any combination thereof;

Assignees

• Battelle Memorial Institute

Inventors

• Xu Wu
• Chen Shuru
• Zhang Ji-Guang
• Cao Xia
• Jia Haiping
• Liu Bin
• Ren Xiaodi

Classifications

• H01M10/0568

  characterised by the solutes · CPC title

• H01M10/0569 Primary

  characterised by the solvents · CPC title

• H01M10/052

  Li-accumulators · CPC title

• H01M10/0567 Primary

  characterised by the additives · CPC title

• H01M4/382

  Lithium (H01M4/405 takes precedence) · CPC title