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.

Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.

