# US 11,309,585 B2 · Molten ion conductive salt/silicon interface for decreased interfacial resistance

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- Number: US 11,309,585 B2
- Document ID: US11309585B2
- Status: Granted
- Kind: B2
- Application number: 16/389,069
- Filed: 2019-04-19
- Published: 2020-10-22
- Granted: 2022-04-19
- Earliest claimed: 2019-04-19
- Assignees: International Business Machines Corporation
- Applicants: International Business Machines Corporation
- Inventors: John Collins; Ali Afzali-Ardakani; Teodor K. Todorov; Joel P. de Souza; Devendra K. Sadana
- Web page: https://patentgrep.com/patent/US11309585B2

## CPC

- H01M 10/399: {Cells with molten salts}
- H01M 4/131: Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
- H01M 4/134: Electrodes based on metals, Si or alloys
- H01M 4/137: Electrodes based on electro-active polymers
- H01M 4/1395: of electrodes based on metals, Si or alloys
- H01M 4/1399: of electrodes based on electro-active polymers
- H01M 4/364: {as mixtures}
- H01M 4/382: {Lithium (H01M4/405 takes precedence)}
- H01M 4/386: {Silicon or alloys based on silicon}
- H01M 10/04: Construction or manufacture in general (H01M10/058, H01M10/12, H01M10/28, H01M10/38 take precedence)
- H01M 10/0525: Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
- H01M 10/056: characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
- H01M 10/0562: Solid materials
- H01M 10/0565: Polymeric materials, e.g. gel-type or solid-type
- H01M 50/414: Synthetic resins, e.g. thermoplastics or thermosetting resins
- H01M 50/417: Polyolefins
- H01M 50/42: Acrylic resins
- H01M 50/426: Fluorocarbon polymers
- H01M 50/497: Ionic conductivity
- H01M 2300/0082: Organic polymers
- H01M 2300/0091: in the form of mixtures
- Y02E 60/10: Energy storage using batteries
- H01M: PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION

## Abstract

An interfacial additive layer for decreasing the interfacial resistance/impedance of a silicon based electrode-containing device such as, for example, an energy storage device or a micro-resistor, is disclosed. The interfacial additive layer, which is composed of a molten lithium containing salt, is formed between a silicon based electrode and a solid polymer electrolyte layer of the device. The presence of such an interfacial additive layer increases the ion and electron mobile dependent performances at the silicon based electrode interface due to significant decrease in the resistance/impedance that is observed at the respective interface as well as the impedance observed in the bulk of the device.

## Claims

### Claim 1

A device comprising:
a silicon based electrode;
an interfacial additive layer composed of a molten lithium containing salt, wherein the interfacial additive layer has a first surface forming an interface with a surface of the silicon based electrode; and
a solid polymer electrolyte layer forming an interface with a second surface of the interfacial additive layer that is opposite the first surface of the interfacial additive layer.

### Claim 2 (depends on 1)

The device of claim 1, wherein the silicon based electrode is selected from the group consisting of non-porous silicon, partially porous crystalline silicon, single-crystal non-porous silicon, crystalline silicon, a low resistance doped crystalline silicon, boron doped crystalline silicon and boron doped crystalline porous silicon.

### Claim 3 (depends on 1)

The device of claim 1, wherein the molten lithium containing salt is composed of at least one of lithium hexafluorophosphate, lithium perchlorate, lithium trifluoromethanesulfonate, lithium fluoride, LiBF4, lithium chloride, lithium phosphate compounds, lithium bromide compounds, lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium difluoro(oxalato)borate (LiDFOB), or lithium bis(oxalato)borate (LiBOB).

### Claim 4 (depends on 1)

The device of claim 1, wherein the solid polymer electrolyte layer is composed of a mixture of a polymer structure host material, a Li-conductive/plasticizing material and a lithium containing salt.

### Claim 5 (depends on 4)

The device of claim 4, wherein the polymer structure host material is composed of at least one of poly(ethylene oxide) (PEO), poly(propylene oxide) (PPO), poly(dimethylsiloxane), poly(vinyl chloride), or polycaprolactone.

### Claim 6 (depends on 5)

The device of claim 5, wherein the Li-conductive/plasticizing material comprises at least one of succinonitrile, poly(ethylene glycol) (PEG) or an aprotic organic solvent.

### Claim 7 (depends on 4)

The device of claim 4, wherein the lithium containing salt is composed of at least one of lithium hexafluorophosphate, lithium perchlorate, lithium trifluoromethanesulfonate, lithium fluoride, LiBF4, lithium chloride, lithium phosphate compounds, lithium bromide compounds, lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium difluoro(oxalato)borate (LiDFOB), or lithium bis(oxalato)borate (LiBOB).

### Claim 8 (depends on 1)

The device of claim 1, wherein the solid polymer electrolyte layer comprises a lower region and an upper region, and wherein a separator is present between the lower region and the upper region.

### Claim 9 (depends on 8)

The device of claim 8, wherein the separator is composed of at least one of polyacrylnitrile (PAN), polyethylene oxide (PEO) based copolymer matrices or structural membranes, a quarternized polysulfone membrane, electrospun polyvinylidene fluoride, or a methylmethacrylate (MMA)/polyethylene (PE) composite.

### Claim 10 (depends on 1)

The device of claim 1, wherein the solid polymer electrolyte layer is composed of a garnet/polymer electrolyte composite.

### Claim 11 (depends on 1)

The device of claim 1, further comprising a counter electrode located above the solid polymer electrolyte layer.

### Claim 12 (depends on 11)

The device of claim 11, wherein the counter electrode is a second silicon based electrode, and wherein a second interfacial additive layer composed of another molten lithium containing salt is present directly between the solid polymer electrolyte layer, and the second silicon based electrode.

### Claim 13 (depends on 12)

The device of claim 12, wherein the second silicon based electrode is selected from the group consisting of non-porous silicon, partially porous crystalline silicon, single-crystal non-porous silicon, crystalline silicon, a low resistance doped crystalline silicon, boron doped crystalline silicon and boron doped crystalline porous silicon.

### Claim 14 (depends on 12)

The device of claim 12, wherein the second molten lithium containing salt is composed of at least one of lithium hexafluorophosphate, lithium perchlorate, lithium trifluoromethanesulfonate, lithium fluoride, LiBF4, lithium chloride, lithium phosphate compounds, lithium bromide compounds, lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium difluoro(oxalato)borate (LiDFOB), or lithium bis(oxalato)borate (LiBOB).

### Claim 15 (depends on 1)

The device of claim 1, wherein an interfacial area between the silicon based electrode and the interfacial additive layer has a charge resistance of less 14.5 ohms/cm2, the interfacial area and bulk regions of the solid polymer electrolyte layer has a mass transport resistance of less than 800 ohm/cm2, and wherein a mass transfer/charge transfer resistance ratio is less than, or equal to, 57.

### Claim 16

A device comprising:
a silicon based electrode composed of boron doped crystalline silicon;
an interfacial additive layer composed of molten lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), wherein the interfacial additive layer has a first surface forming an interface with a surface of the silicon based electrode; and
a solid polymer electrolyte layer composed of a mixture of polycaprolactone, succinonitrile and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) forming an interface with a second surface of the interfacial additive layer that is opposite the first surface of the interfacial additive layer.

### Claim 17 (depends on 16)

The device of claim 16, further comprising a second interfacial additive layer composed of molten lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) forming an interface with the solid polymer electrolyte layer, and a second silicon based electrode composed of boron doped crystalline silicon forming an interface with the second interfacial additive layer.

### Claim 18

A method of forming a device, the method comprising:
depositing a layer of a lithium containing salt on a surface of a silicon based electrode;
heating the layer of the lithium containing salt to a temperature that provides a molten lithium containing salt;
cooling the molten lithium containing salt to provide an interfacial additive layer composed of the molten lithium containing salt; and
forming a solid polymer electrolyte layer on the interfacial additive layer.

### Claim 19 (depends on 18)

The method of claim 18, wherein the heating is performed at a temperature of greater than 350° C. and in an inert ambient.

### Claim 20 (depends on 18)

The method of claim 18, further comprising forming a counter electrode above the solid polymer electrolyte layer.