Methods for making a solid electrolyte interface layer on a surface of an electrode

1. A method for making a solid electrolyte interface (SEI) layer on a surface of an electrode, the method comprising:

exposing the electrode to an electrolyte solution in an electrochemical cell, the electrolyte solution including either i) an organo-polysulfide additive having a formula RS n R′ (n≥2), wherein R and R′ are independently selected from a methyl group, an unsaturated chain, a 3-(Trimethoxysilyl)-1-propyl group, or a 4-nitrophenyl group or ii) a fluorinated organo-polysulfide additive having a formula RS n R′ (n≥2), wherein R and R′ can be the same or different, and wherein R and R′ each have a general formula of C x H y F (2x−y+1) , where x is at least 1 and y ranges from 0 to 2x; and

applying a voltage or a load to the electrochemical cell, wherein the applying of the voltage or the load causes the organo-polysulfide additive or the fluorinated organo-polysulfide additive to react to form the SEI layer.

2. The method as defined in claim 1 wherein:

the electrochemical cell is a lithium sulfur battery; and

the applying of the load initiates a discharge cycle of the lithium sulfur battery.

3. The method as defined in claim 2 wherein:

the electrode is a sulfur-carbon composite positive electrode of the lithium sulfur battery;

the lithium sulfur battery further includes a lithium negative electrode; and

a working voltage across the load ranges from greater than 0V to about 3V.

4. The method as defined in claim 3 wherein the electrolyte solution further includes:

a solvent selected from the group consisting of 1,3-dioxolane, dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, 1,2-diethoxyethane, ethoxymethoxyethane, tetraethylene glycol dimethyl ether (TEGDME), polyethylene glycol dimethyl ether (PEGDME), and mixtures thereof; and

a lithium salt selected from the group consisting of lithium bis(trifluoromethylsulfonyl)imide (LiN(CF 3 SO 2 ) 2 or LiTFSI), LiNO 3 , LiPF 6 , LiBF 4 , LiI, LiBr, LiSCN, LiClO 4 , LiAlCl 4 , LiB(C 2 O 4 ) 2 (LiBOB), LiB(C 6 H 5 ) 4 , LiBF 2 (C 2 O 4 ) (LiODFB), LiN(SO 2 F) 2 (LiFSI), LiPF 3 (C 2 F 5 ) 3 (LiFAP), LiPF 4 (CF 3 ) 2 , LiPF 4 (C 2 O 4 ) (LiFOP), LiPF 3 (CF 3 ) 3 , LiSO 3 CF 3 , LiCF 3 SO 3 , LiAsF 6 , and combinations thereof.

5. The method as defined in claim 4 wherein the electrolyte solution further includes a fluorinated ether selected from the group consisting of Bis(2,2,2-trifluoroethyl) ether (F 3 C—CH 2 —O—CH 2 —CF 3 ) and Propyl 1,1,2,2-tetrafluoroethyl ether (H 7 C 3 —O—CF 2 —CHF 2 ).

6. The method as defined in claim 1 wherein:

the electrochemical cell is a lithium ion battery; and

the applying of the voltage initiates a charge cycle of the lithium ion battery.

7. The method as defined in claim 6 wherein:

the electrode is a graphite negative electrode or a silicon negative electrode of the lithium ion battery;

the lithium ion battery further includes a lithium-based positive electrode; and

the applied voltage ranges from greater than 2 V to about 5 V.

8. The method as defined in claim 7 wherein the electrolyte solution further includes:

a solvent selected from the group consisting of ethylene carbonate, dimethyl carbonate, diethyl carbonate, and a mixture of ethylene carbonate, dimethyl carbonate, diethyl carbonate; and

a lithium salt selected from the group consisting of lithium bis(trifluoromethylsulfonyl)imide (LiN(CF 3 SO 2 ) 2 or LiTFSI), LiNO 3 , LiPF 6 , LiBF 4 , LiI, LiBr, LiSCN, LiClO 4 , LiAlCl 4 , LiB(C 2 O 4 ) 2 (LiBOB), LiB(C 6 H 5 ) 4 , LiBF 2 (C 2 O 4 ) (LiODFB), LiN(SO 2 F) 2 (LiFSI), LiPF 3 (C 2 F 5 ) 3 (LiFAP), LiPF 4 (CF 3 ) 2 , LiPF 4 (C 2 O 4 ) (LiFOP), LiPF 3 (CF 3 ) 3 , LiSO 3 CF 3 , LiCF 3 SO 3 , LiAsF 6 , and combinations thereof.

9. The method as defined in claim 1 wherein:

the electrode is a graphite working electrode or a silicon working electrode;

the electrochemical cell is a half cell including a lithium reference/counter electrode; and

the applied voltage ranges from greater than 0 V to about 2 V.

10. The method as defined in claim 9 , further comprising incorporating the electrode having the solid electrolyte interface (SEI) layer thereon into a lithium ion battery.

11. The method as defined in claim 1 wherein the electrolyte solution includes the organo-polysulfide, wherein the R is the unsaturated chain, the 3-(Trimethoxysilyl)-1-propyl group, or the 4-nitrophenyl group, and wherein the applying the voltage or the load occurs for a time of a charge process or discharge process of the electrochemical cell, whereby in situ polymerization of the unsaturated chain, the 3-(Trimethoxysilyl)-1-propyl group, or the 4-nitrophenyl group takes place.

12. The method as defined in claim 1 wherein the electrolyte solution includes the organo-polysulfide or the fluorinated organo-polysulfide additive in an amount ranging from greater than 0 vol % to about 50 vol % of a total vol % of the electrolyte solution.

13. The method as defined in claim 1 wherein:

the electrode is a lithium working electrode;

the electrochemical cell is a half cell including a lithium reference/counter electrode; and

the applied voltage forces a reaction between the lithium working electrode and the organo-polysulfide or the fluorinated organo-polysulfide additive to form the SEI layer.

14. The method as defined in claim 1 wherein the electrolyte solution includes the organo-polysulfide additive and the unsaturated chain is selected from the group consisting of a vinyl group and an allyl group.

15. The method as defined in claim 1 wherein the electrolyte solution includes the fluorinated organo-polysulfide and the R and R′ are independently selected from the group consisting of CF 3 , CF 2 CF 3 , and CH 2 CF 3 .

16. The method as defined in claim 1 wherein the electrolyte solution includes the fluorinated organo-polysulfide and wherein the applying the voltage or the load occurs for a time of a charge process or discharge process of the electrochemical cell, whereby in situ polymerization of any of R or R′ takes place.