Methods of making sulfide-impregnated solid-state battery

A method of making the sulfide-impregnated solid-state battery is provided. The method comprises providing a cell core that is constructed by cell unit. The cell core is partially sealed into the packaging such as the Al laminated film and metal can. The method further comprises introducing a sulfide solid-state electrolyte (S-SSE) precursor solution in the cell core, the S-SSE precursor solution comprises a sulfide solid electrolyte and a solvent. The method further comprises evaporating the solvent from the cell core to dry the cell core to solidify the sulfide-based solid-state electrolyte within the cell core and pressurizing the cell core to densify the solid sulfide-base electrolyte within the cell core. The cell core is then fully sealed.

INTRODUCTION

The present disclosure relates to rechargeable solid-state batteries and, more particularly, methods of making sulfide-impregnated solid-state batteries.

With the rapid popularization of information-related devices, communication devices, and so on, the importance of developing batteries that can be used as power supplies for these devices has grown. Moreover, in the automobile industry, the development of high-power-output, large-energy-density batteries that can be used in electric automobiles or hybrid automobiles is progressing. Among the various types of batteries that currently exist, lithium-ion batteries are one focus of attention due to a favorable power density (fast charging/discharging performance), a high energy density, a long cycle life, and an ability to be formed into a wide variety of shapes and sizes so as to efficiently fill available space in electric vehicles, cellular phones, and other electronic devices. However, those commercialized lithium-ion batteries are generally employing flammable organic liquid electrolyte which may result in undesirable risks.

Driven by enhancing the battery safety, organic liquid electrolytes have been considered to be replaced by nonflammable solid-state electrolyte (SSE), which can also endow lithium-ion batteries with wide working temperature range, high energy density, simple cell packaging and so on. Among various SSEs, sulfide-based solid-state electrolyte (S-SSE) has attracted increasing attention due to its high conductivity, soft mechanical strength and great potential to be an enabling material for high-power-type solid-state battery (SSB). Although many advances have been achieved in sulfide-based solid-state battery (S-SSB), challenges in S-SSB fundamental science, manufacturing and large-scale production still exist. For example, a critical issue in current S-SSB manufacturing (e.g., wet-coating process) is related to high sensitivity of S-SSE to moisture, where S-SSE may react with H2O molecules which may be undesirable. In this regard, ambient atmosphere is tightly controlled in each step of manufacturing, which may increase the manufacturing cost. In addition, for current methods of S-SSB manufacturing, the distribution of active materials and S-SSEs within the electrode is relatively inhomogeneous with improvable electrode-electrolyte interface, and the selections of solvent, binder and their combination are relatively limited.

SUMMARY

According to several aspects, a method of making a sulfide-impregnated solid-state battery is provided. For typical sulfide-based solid-state battery (S-SSB) manufacturing, sulfide-based solid-state electrolyte (S-SSE) will be mixed with active material in solvent to form the slurry, which is followed by slurry coating, electrode drying, electrode stacking and cell sealing. If the moisture control is not good, S-SSE will react with H2O, and generate toxic H2S. Hence, the moisture content in environment must be tightly controlled in each step of the manufacturing. In the method of making a sulfide-impregnated solid-state battery, S-SSE will be involved from being dissolved into solvent to form the precursor solution, followed by its impregnation into as-formed cell core. This method will maximally rely on conventional lithium-ion battery manufacturing, and the moisture content in environment do not need to tightly control because the S-SSE dissolved in solvent could not directly contact with the moister in environmental. As a result, the method of making a sulfide-impregnated solid-state battery is low-cost and toxic-free. The method comprises providing a cell core, which is fabricated based on conventional lithium-ion battery manufacturing system and process. The cell core is constructed by basic cell units. Each cell unit has a positive electrode including a cathode layer and a positive current collector. The cell unit further has a negative electrode including an anode layer and a negative current collector. The cell unit further has a separator layer disposed between the positive electrode and the negative electrode. For example, the separator being a permeable oxide-based film. Such basic cell unit may be repeated/connected in parallel or in series (namely, bipolar stacking) to form a cell core to achieve a desired battery voltage, power and energy. The cell core is further partially sealed into the packaging such as the Al laminated film and metal can.

The method further comprises introducing a sulfide-based solid-state electrolyte (S-SSE) precursor solution into the above cell core. During this step, the precursor solution will be absorbed into the pore structures of the electrodes and separator layers due to capillary force. The S-SSE precursor solution comprises a sulfide-based solid-state electrolyte and a solvent. The method further includes evaporating the solvent from the cell core to dry the cell core to in-situ solidify the sulfide-based solid-state electrolyte within the cell core. During the solvent evaporation, the S-SSE will be precipitated out and directly grown onto the surface of electrode particles. Hence, an intimate solid-solid electrode-electrolyte interface will be built up, which will be beneficial to effectively improve the cell performance. The method further comprises pressurizing the cell core to densify the solid sulfide-base electrolyte within the cell core and fully sealing the cell core.

In this aspect, the cell core may be comprised of a plurality of cell units that connected in series, that is bipolar-stacked battery cell core. In bipolar-stacked battery cell core, only the outermost current collectors in the cell core have tabs extending from their top sides. The outermost current collectors are indicated as either positively charged or negatively charged. The other current collectors in the cell core are shared by both cathode and anode layers. In another aspect, the cell core may be comprised of a plurality of cell units that connected in parallel. In parallel-stacked battery cell core, all the current collectors have tabs extending from their top sides. The first and third current collectors (staring from left) are electrically connected and indicated as positively charged as they would be during discharge of solid-state battery cell module. The second and fourth current collectors are electrically connected and indicated as negatively charged. Moreover, the introducing step may comprise one of injecting the sulfide solid-state electrolyte precursor solution in the cell core or dipping the cell core into the S-SSE precursor solution. In this aspect, the S-SSE precursor solution comprises a concentration of about 0.001 g/mL to about 20 g/mL of the sulfide-based solid-state electrolyte.

In another aspect, the sulfide solid electrolyte precursor solution may comprise at least one of a pseudobinary sulfide with solvent, a pseudoternary sulfide with solvent, and a pseudoquaternary sulfide with solvent. The pseudobinary sulfide with solvent may comprise one of Li3PS4, and Li7P3S11, Li4SnS4, and 80Li2S.20P2S5with solvent of tetrahydrofuran, ethylacetate, acetonitrile, water or N-methyl formamide. Moreover, the pseudoternary sulfide with solvent may comprise one of Li3.25Ge0.25P0.75S4, Li6PS5Br, Li6PS5Cl, Li7P2S8I, Li4PS4I, and LiI—Li4SnS4with solvent of hydrazine, ethanol, tetrahydrofuran, acetonitrile, 1,2-dimethoxyethane or methanol. Additionally, the pseudoquaternary sulfide with solvent may comprise one of Li9.54Si1.74P1.44S11.7O10.3and Li10.35[Sn0.27Si1.08]P1.65S12with solvent of ethanol, tetrahydrofuran, acetonitrile or methanol. In another example, the S-SSE precursor solution comprises Li10GeP2S12, a polyethylene oxide and an acetonitrile solvent. In some examples, to improve the S-SSE dispersibility, some dispersant (such as Triton X-100) are further added into S-SSE precursor solution.

In accordance with another example, the step of evaporating solvent comprises heating the cell core between about 60 degC and about 600 degC under vacuum for about 30 minutes to about 120 hrs.

In another aspect, the step of pressurizing comprises pressurizing the cell core between about 2 MPa and about 800 MPa at about 100 to about 300 C for about 2 min to about 12 hrs.

In yet another example, after the step of evaporating, the method further comprises introducing the sulfide solid-state electrolyte (S-SSE) precursor solution to the cell core and evaporating the solvent from the cell core to dry the cell core to solidify the sulfide-based solid-state electrolyte within the cell core.

In yet another aspect, after the step of pressurizing, the method further comprises introducing the sulfide solid-state electrolyte (S-SSE) precursor solution to the cell core, evaporating the solvent from the cell core to dry the cell core to solidify the sulfide-based solid-state electrolyte within the cell core, and pressurizing the cell core to densify the cell core to densify the solid sulfide-base electrolyte within the cell core.

In accordance with several other aspects, a sulfide-impregnated solid-state battery is provided. The battery comprises a cell core that is constructed by basic cell units. The cell unit has a positive electrode including a cathode layer and a positive current collector. The cell unit further has a negative electrode including an anode layer and a negative current collector. The cell unit further has a separator layer disposed between the positive electrode and the negative electrode. For example, the separator being a permeable oxide-based film. Such basic cell unit may be repeated/connected in parallel or in series (namely, bipolar stacking) to form a cell core to achieve a desired battery voltage, power and energy. Furthermore, the battery further comprises a densified sulfide-based solid-state electrolyte dispersed in pore structure of the cathode layer, the anode layer, and the separator layer.

In one aspect, the cell core may be comprised of a plurality of cell units that connected/repeated in series, that is, bipolar-stacked battery cell core. In bipolar-stacked battery cell core, only the outermost current collectors in the cell core have tabs extending from their top sides. The outermost current collectors are indicated as either positively charged or negatively charged. The other current collectors in the cell core are shared by both cathode and anode layers. In another aspect, the cell core may be comprised of a plurality of cell units that connected in parallel. In parallel-stacked battery cell core, all the current collectors have tabs extending from their top sides. The first and third current collectors (staring from left) are electrically connected and indicated as positively charged as they would be during discharge of solid-state battery cell module. The second and fourth current collectors are electrically connected and indicated as negatively charged. The electrode current collector has a thickness of between about 4 micrometers and about 100 micrometers.

In another example, the cathode layer comprises between about 30 wt % and about 98 wt % cathode active material, between about 0 wt % and about 50 wt % solid electrolyte, between about 0 wt % and about 30 wt % conductive additive, and between about 0 wt % and about 20 wt % binder. Moreover, the anode layer comprises between about 30 wt % and about 98 wt % anode active material, between about 0 wt % and about 50 wt % solid electrolyte, between about 0 wt % and about 30 wt % conductive additive, and between about 0 wt % and about 20 wt % binder. Each of the cathode layer and the anode layer may have a thickness of between about 1 micrometer and about 1000 micrometers.

In another aspect, the cathode active material comprises at least one of LiNi0.5Mn1.5O4, LiNbO3-coated LiNi0.5Mn1.5O4, LiCoO2, LiNixMnyCo1-x-yO2, LiNixMn1-xO2, Li1+xMO2, LiMn2O4, LiV2(PO4)3, or mixtures thereof. Moreover, the anode active material may comprise at least one of carbonaceous material, silicon, silicon mixed with graphite, Li4Ti5O12, transition-metal, metal oxide/sulfide, or mixtures thereof.

In another example, the sulfide solid electrolyte comprises at least one of a pseudobinary sulfide, a pseudoternary sulfide, and a pseudoquaternary sulfide. The pseudobinary sulfide may include one of Li3PS4, Li7P3S11, Li4SnS4, and 80Li2S.20P2S5. The pseudoternary sulfide may include one of Li3.25Ge0.25P0.75S4, Li6PS5Br, Li6PS5Cl, Li7P2S8I, Li4PS4I, and LiI—Li4SnS4. The pseudoquaternary sulfide may include one of Li9.54Si1.74P1.44S11.7O10.3and Li10.35[Sn0.27Si1.08]P1.65S12.

In accordance with yet another aspect, a method of making a sulfide-impregnated solid-state battery is provided. The method comprises providing a cell core that constructed by basic cell units. The cell unit has a positive electrode having a cathode layer and a positive current collector. The cathode layer comprises between about 30 wt % and about 98 wt % cathode active material, between about 0 wt % and about 50 wt % solid electrolyte between about 0 wt % and about 30 wt % conductive additive, and between about 0 wt % and about 20 wt % binder.

In this aspect, the cell unit having a negative electrode comprising anode layer and a negative current collector. The anode layer comprises between about 30 wt % and about 98 wt % anode active material, between about 0 wt % and about 50 wt % solid electrolyte, between about 0 wt % and about 30 wt % conductive additive, and between about 0 wt % and about 20 wt % binder. The cell core further comprises a separator layer disposed between the positive electrode and the negative electrode. The separator may be comprised of a permeable oxide-based film; Such basic cell unit may be repeated/connected in parallel or in series (namely, bipolar stacking) to form a cell core to achieve a desired battery voltage, power and energy. The cell core is further partially sealed into the packaging such as the Al laminated film and metal can.

Further to this aspect, the method further comprises introducing a sulfide-based solid-state electrolyte (S-SSE) precursor solution in the cell core. The S-SSE precursor solution comprises a sulfide solid electrolyte and a solvent. In some embodiments, a solvent may comprise at least one of a tetrahydrofuran, ethyl propionate, ethylacetate, acetonitrile, water, N-methyl formamide, methanol, ethanol, and 1,2-dimethoxyethane. In some embodiment, a co-solvent may be used, such as ethanol and tetrahydrofuran. In this example, the sulfide solid electrolyte comprises at least one of a pseudobinary sulfide, a pseudoternary sulfide, and a pseudoquaternary sulfide. The pseudobinary sulfide may comprise one of Li3PS4, Li7P3S11, Li4SnS4, and 80Li2S.20P2S5. The pseudoternary sulfide may comprise one of Li3.25Ge0.25P0.75S4, Li6PS5Br, Li6PS5Cl, Li7P2S8I, Li4PS4I, and LiI—Li4SnS4. Moreover, the pseudoquaternary sulfide may comprise one of Li9.54Si1.74P1.44S11.7Cl0.3and Li10.35[Sn0.27Si1.08]P1.65S12.

In this aspect, the method further comprises evaporating the solvent from the cell core between about 60 degC and about 600 degC under vacuum for about 30 minutes to about 120 hours to dry the cell core and solidify the sulfide-based solid-state electrolyte within the cell core. It is understood that evaporating the solvent from the cell core may occur under no vacuum. The method further comprises pressurizing the cell core between about 2 MPa and about 800 MPa at about 100 to about 300 C for about 2 minutes to about 12 hours to densify the solid sulfide-base electrolyte within the cell core and fully sealing the cell core.

DETAILED DESCRIPTION

Referring toFIGS. 1-2A, a method10of making a sulfide-impregnated solid-state battery is provided. As shown, method10comprises a step12of providing a cell core14. In this example, the cell core14in a bipolar stacking design is provided, as shown inFIG. 2A.

As provided inFIGS. 1-2A, the cell core14is constructed by basic cell units. Such basic cell unit may be repeated/connected in parallel or in series (namely, bipolar stacking) to form a cell core to achieve a desired battery voltage, power and energy. The cell core is further partially sealed into the packaging such as the Al laminated film and metal can.

In this embodiment, the cell core14(FIG. 2A) includes at least one positive electrode16having a cathode layer18and a positive current collector20. Preferably, cathode layer18comprises between about 30 wt % and about 98 wt % cathode active material, between about 0 wt % and about 30 wt % conductive additive, and between about 0 wt % and about 20 wt % binder. In this embodiment, the cathode active material may comprise any suitable material such as a high-voltage oxide, a surface-coated high-voltage cathode material, a doped high-voltage cathode material, a rock salt layered oxide, a spinel, a polyanion cathode, a lithium transition-metal oxide, or mixtures thereof. In one embodiment, the cathode active material comprises LiNi0.5Mn1.5O4, LiNbO3-coated LiNi0.5Mn1.5O4, LiCoO2, LiNixMnyCo1-x-yO2, LiNixMn1-xO2, Li1+xMO2, LiMn2O4, or LiV2(PO4)3, or mixtures thereof.

In one embodiment, the conductive additive of the cathode layer may comprise any suitable material such as carbon black, graphite, graphene, graphene oxide, Super P, acetylene black, carbon nanofibers, carbon nanotubes and other electronically conductive additives. Moreover, the binder of the cathode layer may comprise poly(tetrafluoroethylene) (PTFE), sodium carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), poly(vinylidene fluoride) (PVDF), nitrile butadiene rubber (NBR), styrene ethylene butylene styrene copolymer (SEBS), styrene butadiene styrene copolymer (SBS).

Moreover, cathode layer18may have a thickness of between about 1 micrometer and about 1000 micrometers. In this embodiment, the positive current collector comprises a conductive material and has a thickness of between about 4 micrometers and about 100 micrometers. The conductive material may comprise aluminum, nickel, iron, titanium, copper, tin, and alloys thereof.

As shown inFIG. 2A, each cell core14further includes at least one negative electrode22comprising an anode layer24and a negative current collector26. In this embodiment, anode layer24preferably comprises between about 30 wt % and about 98 wt % anode active material, between about 0 wt % and about 30 wt % conductive additive, and between about 0 wt % and about 20 wt % binder. Moreover, anode layer24may have a thickness of between about 1 micrometer and about 1000 micrometers.

In one embodiment, the conductive additive of the anode layer may comprise any suitable material such as carbon black, graphite, graphene, graphene oxide, Super P, acetylene black, carbon nanofibers, carbon nanotubes and other electronically conductive additives. Moreover, the binder of the anode layer may comprise poly(tetrafluoroethylene) (PTFE), sodium carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), poly(vinylidene fluoride) (PVDF), nitrile butadiene rubber (NBR), styrene ethylene butylene styrene copolymer (SEBS), styrene butadiene styrene copolymer (SBS).

Preferably, the negative current collector has a thickness of between about 4 micrometers and about 100 micrometers.

The cell core14further has a separator layer25disposed between the positive electrode16and the negative electrode22. The separator layer25is preferably a oxide-based or polymer-based film with porosity of 0-90%. In one embodiment, separator layers25may comprise an oxide ceramic powder, e.g., SiO2, CeO2, Al2O3, ZrO2.

In this example, it is understood that the outermost current collectors in the cell core14(FIG. 2) have tabs extending from their top sides. As shown, the current collector20is indicated as positively charged as would be during discharge of a battery cell module. As shown inFIG. 2, the current collector26is indicated as negatively charged. In this example, the other current collectors are shared by both the cathode and anode layers as shown inFIG. 2. It is further understood that prior to the introducing step27, a step of pre-pressing the cell core14may occur. Such pre-pressing step may be achieved by any suitable manner. For example, the step of pre-pressing comprises pressing the cell core between about 2 MPa and about for about 2 min to about 12 hrs.

It is understood that the cell cores may be arranged in any other suitable manner such as a parallel-connected stacking design as illustrated inFIG. 2B. As shown, each cell core may be comprised of a plurality of cell units that are connected in a parallel-stacked battery cell core. The current collectors have tabs extending therefrom. As shown inFIG. 2B, tab211along with current collectors213,215are electrically connected and indicated as positively charged as during discharge of the solid-state battery cell module. Tab221along with current collectors223,225are electrically connected and indicated as negatively charged.

As shown inFIGS. 1 and 3, the method10further comprises a step27of introducing a sulfide solid-state electrolyte (S-SSE) precursor solution30in the cell core14. As depicted inFIG. 4, precursor solution is dispersed within the porous structures of cathode layer18, anode layer24, and separator layer25.

In this embodiment, the S-SSE precursor solution30comprises a sulfide-based solid electrolyte32and a solvent34. Step27of introducing the S-SSE precursor solution in the cell core may be achieved in any suitable manner. For example, the S-SSE precursor solution may be injected in the cell core. Alternatively, the cell core may be dipped in S-SSE precursor solution to introduce the S-SSE precursor solution in the cell core.

In one example, the S-SSE precursor solution comprises a Li6PS5Cl-ethanol solution. In another example, the S-SSE precursor solution comprises at least one of a pseudobinary sulfide, a pseudoternary sulfide, and a pseudoquaternarysulfide dissolved in solvent. In this aspect, the pseudobinary sulfide comprises one of Li3PS4, Li7P3S11, Li4SnS4, and 80Li2S.20P2S5. The pseudoternary sulfide may comprise one of Li3.25Ge0.25P0.75S4, Li6PS5Br, Li6PS5Cl, Li7P2S8I, Li4PS4I, and LiI—Li4SnS4.

Further, the pseudoquaternary sulfide may comprise one of Li9.54Si1.74P1.44Si1.7Cl0.3and Li10.35[Sn0.27Si1.08]P1.65S12. The solvent may comprise at least one of a tetrahydrofuran, ethyl propionate, ethylacetate, acetonitrile, water, N-methyl formamide, methanol, ethanol, and 1,2-dimethoxyethane. In some examples, to improve the S-SSE dispersibility, some dispersants (such as Triton X-100) are further added into S-SSE precursor solution.

As depicted inFIGS. 1 and 5, method10further comprises a step36of evaporating solvent34from the cell core14to dry the cell core and solidify the sulfide-based solid-state electrolyte32within the cell core14. In this example, cell core14is heated between about 60 degC and about 600 degC under vacuum for about 30 minutes to about 120 hours. Preferably, the drying temperature should be higher than the boiling point of solvents. During heating, solvent34is evaporated from cell core14as shown inFIG. 5. Preferably, cell core14is heated at about 180 degC under vacuum for about 6 hours, thereby evaporating solvent34from the cell core14, when using ethanol as solvent. Thus, during step36, cell core14is dried and the sulfide-based solid-state electrolyte is precipitated out and solidified within the pores of the cell core. It is understood that the step36of evaporating may occur under no vacuum. It is further understood that prior to the evaporating step36, a step of vibrating the cell core may occur to improve the wettability of the S-SSE precursor solution30. The vibrating step may be achieved by any suitable manner.

FIGS. 6a-6bdepict cell core14after the step of evaporating the solvent therefrom as discussed above. As shown inFIG. 6a, cell core14comprises solidified sulfide-based solid-state electrolyte32dispersed within the pore structures of cell core.FIG. 6billustrates magnified cross-sectional view of the anode layer24, where sulfide-based solid-state electrolyte32has grown or dispersed onto the surface of anode active material particles and pore33still exists.

As depicted inFIG. 1, method10further comprises a step38of pressurizing cell core14to densify the cell core thereby densifying the solid sulfide-base electrolyte within the cell core14and eliminating the pore33. In this example, step38comprises pressurizing cell core14between about 2 MPa and about 800 MPa at about 10 C to about 300 C for about 2 minutes to about 12 hours to densify the solid sulfide-base electrolyte within the cell core. In another example, the cell core is pressurized at greater than about 360 MPa.

Furthermore, method10further comprises a step40of fully sealing the cell core. In this example, cell core14may be sealed in any suitable manner. For example, the cell core may be fully sealed by way of vacuum seal thereby preventing exposure to air. Thus, the cell core may be placed in an aluminum laminated bag, can or container, and followed by fully vacuum sealing.

FIG. 8depicts a method110of making a sulfide-impregnated solid-state battery in accordance with another example. Method110comprises the steps of method10inFIG. 1. For example, method110comprises a step112of providing a cell core and partially sealing into the packaging such as the Al laminated film and metal can, a step120of introducing a sulfide solid-state electrolyte precursor solution, a step136of evaporating the solvent from the cell core, a step144of pressurizing the cell core, and a step150of fully sealing the cell core. As shown, after step136of evaporating, the method further comprises a step138of introducing additional S-SSE precursor solution to the cell core and a step140of evaporating the solvent from the cell core to dry the cell core to solidify the sulfide-based solid-state electrolyte within the cell core. In some embodiments, steps138and140may be repeated.

FIG. 9illustrates a method210of making a sulfide-impregnated solid-state battery in accordance with another example. Method210comprises the steps of method10inFIG. 1. For example, method210comprises a step212of providing a cell core and partially sealing into the packaging such as the Al laminated film and metal can, a step220of introducing a sulfide solid-state electrolyte precursor solution, a step236of evaporating the solvent from the cell core, a step244of pressurizing the cell core, and a step250of sealing the cell core. As shown, after step244of pressurizing, the method210further comprises a step246of introducing a sulfide solid-state electrolyte precursor solution, a step248of evaporating the solvent from the cell core, and a step249of pressurizing the cell core. In some embodiments, steps246,248, and249may be repeated. In a preferred example, the step246of introducing a sulfide solid-state electrolyte precursor solution, the step248of evaporating the solvent from the cell core, and the step249of pressurizing the cell core may be repeated at least twice.

FIG. 10illustrates a method310of making a sulfide-impregnated solid-state battery in accordance with another example. As shown method310comprises a step312of providing a cell core and partially sealing into the packaging such as the Al laminated film and metal can, a step320of introducing a sulfide solid-state electrolyte precursor solution and a step350of sealing the cell core. Additionally, after step320of introducing, method310further comprises a step325of simultaneously evaporating the solvent from the cell core and pressurizing the cell core to densify the solid sulfide-base electrolyte.