EP4627654A1 - Fast cycling of lithium metal solid state battery at high loading - Google Patents

Abstract

An electrochemical cell (e.g., rechargeable solid state battery) includes a cathode, an anode, and a solid state electrolyte disposed between the cathode and the anode. The anode includes an anode material having a plurality of voids. In some embodiments, the cathode includes lithium, and the anode is formulated to cause lithium metal to be deposited in the plurality of voids during charging of the electrochemical cell. In some embodiments, the anode includes a constriction-susceptible surface that controls the interplay between lithiation and lithium plating. The electrochemical cells disclosed herein are advantageous as they provide improved battery cycling performance combined with excellent power and energy density.

Description

FAST CYCLING OF LITHIUM METAL SOLID STATE BATTERY AT HIGH LOADING

TECHNICAL FIELD

Embodiments described herein are related to electrochemical cells (e.g., solid state rechargeable batteries) including anode materials having a plurality of voids, methods of using thereof and making the same.

BACKGROUND

Lithium (Li) metal anodes hold significant importance in the development of next-generation high-energy density batteries due to their high specific capacity (about ten times larger than the capacity of commercial graphite anodes) and low electrochemical potential. However, because of the intrinsic properties of lithium metal, lithium anode has many problems in the process of charging/discharging, limiting the commercialization of rechargeable Li-metal batteries. To meet the demands of fast cycling for thick cathodes in commercial applications, maintaining the stability of a thick layer of Li metal at the anode is desirable but difficult. Harsh cycling conditions, such as high currents and low temperatures, naturally promote non-uniform lithium plating and stripping, ultimately leading to the formation of lithium dendrites. These dendrites can breach the battery separator, causing short circuits and compromising safety. Additionally, isolated Li metal forms during discharge, diminishing the overall cycling performance of the Li anode. These problems can lead to severe capacity loss and even explosion of lithium metal batteries after long operation.

SUMMARY

Embodiments described herein relate to rechargeable solid state batteries with anode materials including a plurality of voids into which Li can deposit as Li metal during charging. The voids can be, e.g., in particles or from the stacking of particles with voids among them. That is, anode materials may include particles having a plurality of voids and/or there might be a plurality of voids between the particles of anode material. Lithium can plate on the surface of the particle and grow into the voids. The lithium metal can also plate under the anode film and form a layer.

In some embodiments, an electrochemical cell (e.g., rechargeable solid state battery) includes: a cathode, an anode, and a solid state electrolyte disposed between the cathode and the anode. The anode includes an anode material having a plurality of voids. In some embodiments, the cathode includes lithium, and the anode is formulated to cause lithium metal to be deposited in the plurality of voids during charging of the electrochemical cell.

In some embodiments, an electrochemical cell includes: a cathode including lithium, an anode including an anode material and a solid state electrolyte disposed between the cathode and the anode. In some embodiments, the anode material has a local effective modulus of at least about 0.3 GPa causing the anode to be under mechanical constriction. In some embodiments, the anode is formulated to cause lithium metal to be deposited on the anode material during charging of the electrochemical cell.

In some embodiments, an electrochemical cell includes a cathode including lithium, an anode including an anode material that includes a plurality of particles, and a solid state electrolyte disposed between the cathode and the anode. In some embodiments, the anode is formulated such that initial charging of the electrochemical cell causes lithium metal to be deposited on the anode. In some embodiments, the lithium metal deposition causes a volume of the plurality of particles to change by less than 300% of an original volume of the plurality of particles.

In some embodiments, provided herein is a method of storing and releasing electrical energy. The method includes providing a battery including a cathode including Li, an anode including an anode material having a plurality of voids, and a solid state electrolyte disposed between the anode and the cathode. The method further includes providing electrical energy to the battery to cause Li⁺ ions to migrate from the cathode to the anode and deposit in the plurality voids as Li metal during charging.

In some embodiments, the method further includes electrically connecting a load between the anode and cathode to allow the Li metal in the voids to oxidize and migrate to the cathode and deposit therein as Li⁺ ions.

In some embodiments, a portion of the Li⁺ ions react with a surface of the anode material to form a surface layer with the anode material, e.g., wherein the electrochemical cell further includes a surface layer on the anode, the surface layer being formed from a reaction between the anode material and lithium ions. In some embodiments, the anode material includes nano-scale and/or micron-scale particles, and the surface layer is less than 500 nm in thickness, e.g., less than 100 nm. In some embodiments, a volume of the particles after a first charging is <300%, e.g., <150%, of an original particle volume. In some embodiments, the anode material does not crack or swell (e.g., as observable by SEM) during charging or discharging. In some embodiments, an average particle diameter after 10 charge and discharge cycles is >70% of an original particle diameter. In some embodiments, a volume of the voids changes by less than 100%, e.g., the anode material is formulated such that a volume of the plurality of voids changes by less than 100%, e.g., less than 50%, during charging and discharging. In some embodiments, the particles swell by less than 300%. In some embodiments, the surface layer is less than 500 nm in thickness, e.g., less than 100 nm. In some embodiments, a portion of the anode material under the surface layer does not undergo lithiation.

In some embodiments, the battery is under mechanical constriction, e.g., where the anode material has constriction susceptibility. In some embodiments, the mechanical constriction is provided by an external pressure of 0.05-50 MPa. In some embodiments, the mechanical constriction is provided by a local effective modulus (Ketf) of the anode material of at least 0.3 GPa.

In some embodiments, the anode material includes Si. In some embodiments, the anode material includes a Si-graphite composite formed of nano-scale and/or micron-scale Si and graphite particles. In some embodiments, the anode material includes at least one of Si, Si alloy, a Si-carbon composite, a Si alloy-carbon composite, Mg metal, a binary Mg Alloy, a ternary Mg alloy, a binary Mg alloy-carbon composite optionally including a solid electrolyte and/or a polymer binder, or a ternary Mg alloy carbon-composite optionally including a solid electrolyte and/or a polymer binder. In some embodiments, at least 10% of the stored electrical energy is stored as lithium metal.

In some embodiments, a solid state battery includes a cathode including Li, an anode including an anode material having a plurality of voids, and a solid state electrolyte disposed between the anode and the cathode. The anode material is under mechanical constriction and, during charging of the battery, Li from the cathode deposits in the plurality of voids as Li metal. In some embodiments, the mechanical constriction limits lithiation of the anode material to a surface layer of less than 500 nm, e.g., less than 100 nm. In some embodiments, the anode material includes nano-scale and/or micron-scale particles, and the surface layer is less than 500 nm in thickness, e.g., less than 100 nm. In some embodiments, a volume of the particles after a first charging is <300%, e.g., <150%, of an original particle volume. In some embodiments, the anode material does not crack or swell (e.g., as observable by SEM) during charging or discharging. In some embodiments, an average particle diameter after 10 charge and discharge cycles is >70% of an original particle diameter. In some embodiments, a volume of the voids changes by less than 100%, e.g., the anode material is formulated such that a volume of the plurality of voids changes by less than 100%, e.g., less than 50%, during charging and discharging of the electrochemical cell. In some embodiments, the particles swell by less than 300%. In some embodiments, the mechanical constriction is provided by an external pressure ranging from about 0.05 MPa to about 50 MPa. In some embodiments, the mechanical constriction is provided by a local effective modulus (K_etf) of the anode of at least 0.3 GPa.

In some embodiments, the anode material includes a material having a capacity over K_Crit (denoted COK) of > 500 mAh/g/GPa and COK*V of > 600 mWh/g/GPa. In some embodiments, the anode material includes Mg metal or a binary or ternary alloy of Mg. In some embodiments, the anode material includes at least one of Si, Si alloy, a Si-carbon composite, a Si alloy-carbon composite, Mg metal, a binary Mg Alloy, a ternary Mg alloy, a binary Mg alloy-carbon composite optionally including a solid electrolyte and/or a polymer binder, or a ternary Mg alloy carbon-composite optionally including a solid electrolyte and/or a polymer binder. In some embodiments, the anode material includes at least one of LiMgs, Mg?Ali , Mgi49Lii , MgugBai , MgugCai, Mgi4gSi , Mgi49Agi , Mg?Bi , NaiMgi4Bi , or MgPb2~s, MgTei~2, MgHgs-s, MgAli~2, MgHi~3, Mglns, MgGe2~s, MgSii~3, MgSbo.5~3, MgS -s, or MgGai~s, e.g., LiMgs, MgyAli , Mgi49Lii , MgugBai, MgugCai, MgugSi, Mgi49Agi , Mg?Bi , or NaiMgi4Bi .

In some embodiments, the anode material includes a material having a capacity over K_Crit (COK) of > 500 mAh/g/GPa and COK*V of e [500, 600] mWh/g/GPa. In some embodiments, the anode material includes: an alloy of Mg of formula Mg_xSii-_x, MgsAI, Li_xMgi-_x, Mg4AliSi4, or Li_xMg_ySii-_x-y where 1 >= x >= 0 and 0 < y < 1 , metal-doped Mg of formula Mg_xM’yM”i-_x-y (where x > 0.8 and y < 0.2 and where M' and M” are metal elements) (e.g., Mgi4Ali Fei), doped MgO of formula (MgO)_xAyB_zOi-_x-y-z (where x > 0.9 and y<0.1 and z<0.1 and where A and B are elements other than Mg or O)), or binary Mg compounds (e.g., Mg2P, LiMgs, MgyAli , MgugLh , MgugBai , MgugCai , MgugSi, MgugAgi, Mg?Bi , etc.).

In some embodiments, the anode material includes a material having a capacity over K_Crit (COK) of > 500 mAh/g/GPa and COK*V e [300, 500] mWh/g/GPa. In some embodiments, the anode material comprises: doped MgO of formula (MgO)_xAyB_zOi-_x-y-z (where x > 0.7, y < 0.3, z < 0.3, and where A and B are elements other than Mg and O) (e.g., Mg3AliO4, LhMgeBiO? and KiMguThO ), compounds of formula Mg_xSii-_x, compounds of formula Mg_xSiyOi-_x-y, or Mg metal alloys of formula Mg_xM’yM”i-_x.y, where x > 0.8 and y < 0.2 and where M' and M” are metals (e.g., MguAhFei, e.g., Mg_xAli-_x, e.g., Mgi?Ali2 and its doped compounds such as Mgi6Ali2l_ii , (e.g., Mg_xAli-_x, e.g., MguAhFei, Mgi?Ali2 and its doped compounds such as MgieAligLii). In some embodiments, the anode material includes Si. In some embodiments, the anode material includes a Si-graphite composite formed of nano-scale and/or micron-scale Si and graphite particles. In some embodiments, the anode material is coated onto Li foil on a current collector (e.g., a stainless-steel current collector). In some embodiments, the anode material undergoes a self-limiting reaction with lithium under mechanical constriction to form a surface layer. In some embodiments, the anode material includes nanoscale and/or micron-scale particles, and the surface layer is less than 500 nm in thickness, e.g., less than 100 nm. In some embodiments, the anode material does not crack or swell during charging or discharging (e.g., as observable by SEM). In some embodiments, the voids may be between about 1 nm and about 1 ,000 pm (e.g., 5 nm to 1 pm, 1 -10 pm, 10 to 100 pm, etc.).

In some embodiments, the surface layer is less than 500 nm in thickness, e.g., less than 100 nm. In some embodiments, the anode material includes particles of 1 nm to100 pm in diameter. In some embodiments, the anode material includes a surface layer or coating that inhibits lithiation. In some embodiments, the battery has a current density ranging from about 0.01 to about 200 mA/cm² without short circuit. In some embodiments, the battery has a cathode loading of from about 0.1 to about 200 mg/cm² with normal charge and discharge. In some embodiments, the battery has an area capacity between about 1 mAh/cm² and about 20 mAh/cm² . In some embodiments, the battery can be cycled for from 1 ,000 to 20,000 cycles at 1 -60 minutes or 0.1 -30 C- rates of charge and discharge.

In some embodiments, the battery has a pouch, prismatic, or cylindrical cell format. In some embodiments, the battery further includes a protection layer and/or a multilayer of solid state electrolytes. In certain embodiments, the protection layer and/or the multilayer of solid state electrolytes is deposited, cast, or transferred onto the cathode, the anode, or a substrate in a layer-by-layer process. In some embodiments, the multilayer comprises n layers of solid state electrolyte, wherein n = >2 (e.g., 2, 3, 4, 5, 6, 7, 8, 9, or 10 or more).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of an electrochemical cell including a cathode, an anode, and a solid state electrolyte disposed between the cathode and the anode, according to an embodiment.

FIG. 2 is a cross-sectional illustration of an electrochemical cell including a cathode, an anode including an anode material having a plurality of voids, and a solid state electrolyte disposed between the cathode and the anode, according to an embodiment.

FIG. 3 is a cross-sectional illustration of an electrochemical cell including a cathode, an anode an anode including anode material having a plurality of voids, and a multilayer solid state electrolyte disposed between the cathode and the anode, according to an embodiment.

FIG. 4 is a cross-sectional illustration of an electrochemical cell including a cathode, an anode including anode material having a plurality of voids, and a solid state electrolyte disposed between the cathode and the anode, according to an embodiment.

FIG. 5 is a schematic flow chart of a method for manufacturing an electrochemical cell including a cathode, an anode, and a solid state electrolyte disposed between the cathode and the anode, according to an embodiment. FIGS. 6(a)-6(e2): FIG. 6(a) shows Li discharge profile in the battery of Li/G- Li5.5PS4.5C11.5 (LPSCI1.5)- Li GeP2Si2 (LGPS) -LPSCIi.s-SiG at the current density of 0.2 mA/cm² at room temperature. FIGS. 6(b1 )- 6(b3) show the FIB-SEM (focused ion beam-scanning electron microscopy) images of Si-graphite anode at each discharge states (FIG. 6(b1 ) to FIG. 6(b3)) corresponding to the points 1 -3 in FIG. 6(a). FIGS. 6(c1 )-6(c3) show SEM-EDS mapping FIGS. 6(c1 )-6(c3) corresponding to the SEM images in FIGS. 6(b1 )-6(b3), where carbon signal C was from graphite, oxygen O and nitrogen N signals are from lithium metal reaction with air, and fluorine F was from PTFE binder. FIG. 6(d) shows discharge profile of the battery with the cell construction of Li-1 M LiPFe in EC/DMC-SiG. FIGS. 6(e1 )-6(e2) show an FIB-SEM image of SiG anode after discharged in a liquid electrolyte battery shown in FIG. 6(d).

FIGS. 7(a)-7(f): FIG. 7(a) shows TEM image of the 500^th charged battery, where the SiG anode was cut by FIB. The structure of the battery was Li-Sig-SEs-NMC83 with a nominal NP ratio of 1 .5, the battery was cycled at 2C at 55 °C. FIG. 7(b) shows EELS line scan across the line in FIG. 7(a). FIG. 7(c) shows STEM-EDS mapping in the squared region in FIG. 7(a). FIGS. 7(d1 )-7(d2) show high resolution TEM of Si particle after FIB. FIGS. 7(e1 )-7(e3) show SEM images, including FIB-SEM images (FIG. 7(e1 )) and EDS mapping (FIG. 7(e2-e3)) of Si-graphite anode at the 1 ^st discharge state (2.5V, 0.5C at room temperature) in the solid electrolyte with the structure of Sig-SEs-NMC83 with a nominal NP ratio of 1 .5. No lithium was underneath SiG anode. FIG. 7(f) shows XPS of the SiG anode after the battery was fully discharged in FIG. 6(a), Li/G-SE- SiG was discharged at the current density of 0.2 mA/cm² at room temperature. Argon milling was conducted with the energy of 0.5 keV for 500s and 1000s.

FIGS. 8(a)-8(d): FIG. 8(a) shows capacity retention comparison between single-SE-layer batteries and multi- SE-layer batteries with a SiG/Li anode, all at 25 mg/cm² cathode loading, 7.4 mA/cm² current density or 2 C- rate, and the same total thickness of electrolyte layer(s). The area capacity of the 2000-cycle battery was from 2.8 mAh/cm² to 2.2 mAh/cm². FIG. 8(b) shows the specific capacity of three batteries at different C-rates showing that multilayer offers higher capacity than single layer of electrolytes, all at 25 mg/cm² cathode loading. FIG. 8(c) shows charge and discharge curves of multilayer batteries with Si of various particle sizes of 1 pm and 44 pm. FIG. 8(d) shows charge and discharge curves of multilayer batteries with different cathode mass loading at 0.5 C. The nominal NP ratio was kept at 1 .5 for all batteries. Electrolyte chemical formulas in the figure legend are Li SnP2Si2 (LSnPS), Li GeP2S12 (LGPS), Li5.5PS4.5Cli.5 (LSPCI1.5 or Cl 1.5) or LiePSsCh .0 (LPSCI1.0 or CI1.0). All batteries are tested at 55 °C.

FIG. 9(a)-9(f): FIG. 9(a) shows charge and discharge curves solid state batteries at 5-10 C-rates and a NMC83 cathode loading of 22mg/cm² at 55 °C, where 1 C = 3.2 mA/cm². FIG. 9(b) shows low temperature voltage profiles of solid state batteries with Li-SiG as anode and cathode loading of 22mg/cm². FIGS. 9(c) and 9(d) show capacity retention and Coulombic efficiency of battery running at 6C-6C and 10C (charge) -2C (discharge) at 55 °C. FIG. 9(e) shows capacity and Coulombic efficiency of battery (NMC83 cathode loading = 15 mg/cm²) running at 5C-5C at 35 °C (80% after 1400 cycles). FIG. 9(f) shows simulated voltage-capacity dependence of Si at different levels of mechanical constriction, where Kerr is the effective modulus ranges from 0-5 GPa.

FIGS. 10(a1 )-10(c2) show the FIB-SEM and EDS mapping of Silicon/graphite (Si/G) anode. In FIGS. 10(a1 ) and 10(a2), the Si/G film was without lithium metal foil and did not undergo a formation pressure. In FIGS. 10(b1 ) and 10(b2), the Si/G film was without lithium metal foil and underwent a formation pressure. In FIGS. 10(c1 ) and 10(c2), the Si/G film was with lithium metal foil and underwent a formation pressure. F was from the PTFE binder and Ga was from FIB ion source.

FIGS. 1 1 (a)-1 1 (f) show FIB-SEM images and cycling performance of liquid and solid electrolyte batteries with SiG anodes. FIGS. 1 1 (a)-1 1 (b) show FIB-SEM images of Si/G anode after the battery of Si/G-liqu id electrolyte- NMC83 (cathode loading = 25 mg/cm²) running for 5 cycles. FIG. 1 1 (c) shows the charge and discharge curves for the battery of SiG-EC/DMC/1 M LiPFe-NMC83, where Si was micron-scale. FIGS. 1 1 (d)-1 1 (e) show FIB- SEM images of an Si/G anode in a battery with the structure: Li/SiG-LPSCI-LGPS-LPSCI-NMC83 (cathode loading = 25 mg/cm²), and an NP ratio of 1 .5, after the 500^th cycling. FIG. 1 1 (f) shows the charge and discharge profile of the battery at 55 °C at 2C, which was also the battery used for STEM-EELS in FIG. 7(a).

FIGS. 12(a)-12(f) show the FIB-SEM images and EDS mapping of Si/G anode after 1 ^st (FIGS. 12(a)-12(c)) and 5^th (FIGS. 12(d)-12(f)) discharge. The battery had the structure of SiG-LPSCI-LGPS-LPSCI-NMC83 (loading = 25 mg/cm²) with an NP ratio of 1 .5. The battery was cycled at room temperature at 0.5C.

FIGS. 13(a)-13(f) show XPS, XRD, FIB-SEM images, and EDS mapping of a battery of structure of Si/G- LPSCI-LGPS-LPSCI-NMC83 (loading = 25 mg/cm²). FIG. 13(a) shows the XPS measurement (Li 1 s signal) of Si/G with NP ratio = 1 .5 after the 1 ^st charge. FIG. 13(b) shows the XRD measurement of Si/G with NP ratio = 1 .5 after the 1 ^st charge. FIGS. 13(c)-13(f) shows the FIB-SEM images and EDS mapping of Si/G anode after charge. The battery had an NP ratio of 0.3. The battery was cycled at room temperature at 0.5C.

FIGS. 14(a)-14(g) show the FIB-SEM image (FIG. 14(a)) and EDS mapping (FIGS. 14(b)-14(g)) of pure Si anode after charge. FIG. 14(b) shows all elements measured (C, N, O, F, and Si). FIG. 14(c) shows F mapping. FIG. 14(d) shows C mapping. FIG. 14(e) shows Si mapping. FIG. 14(f) shows O mapping. FIG. 14(g) shows N mapping. The battery was made with the structure: Si-LPSCI-LGPS-LPSCI-NMC83 (loading = 25 mg/cm²). The NP ratio was 2.5 based on the theoretical capacity of Si and NMC83. The battery was cycled at room temperature at 0.5C. The C and F signals are from the binder PTFE.

FIG. 15(a) shows rate capabilities of batteries with different anodes (Si, 75 wt% Si-25 wt% G, and 50 wt%Si- 50 wt% G). FIG. 15(b) shows cycling performance of Li/Si-SEs-NMC83 (22 mg/cm² loading) at 6C-6C. FIGS. 15(c)-15(d) show charge and discharge curve for Li/SiG-SEs-NMC83 (22 mg/cm² loading) running at 15(c) 6C-6C and 15(d) 10C-2C.

FIGS. 16(a)-16(c) show the FIB-SEM (FIGS. 16(a)-16(b)) and EDS mapping (FIG. 16(c)) of SiG anode after discharging at low operation pressure of 5 MPa. The battery had structure: Si/G-LPSCI-LGPS-LPSCI-NMC83 (loading = 25 mg/cm²) with an NP ratio of 1 .5 and was cycled at room temperature at 0.5C.

FIG. 17 shows the cycling performance of a Li-NMC81 1 solid state pouch cell (shown right of graph) with Si- G anode protection layer on Li metal. Capacity (mAh/g) (y-axis, left) and coulombic efficiency (%) (y-axis, right) are plotted against cycle number over 2000 cycles (x-axis).

FIG. 18(a) shows the high-throughput calculation results of voltage (y-axis) and capacity over K_CTit (COK) (x- axis) for anodic reaction versus Li metal anode, within the plotted axes range, with bandgap smaller than 1 .5 eV. The two dotted lines corresponds to y = 300/x and y = 600/x. FIG. 18(b) shows the high-throughput calculation results of capacity and capacity over Kent for anodic reaction versus Li metal anode, within the plotted axes range, with bandgap smaller than 1 ,5eV.

FIG. 19(a) shows the occurrence of elements in the range of COK > 500 mAh/g/GPa and COK*V > 600 mWh/g/GPa. FIG. 19(b) shows the coappearance of two elements in the range of COK > 500 mAh/g/GPa and COK*V > 600 mWh/g/GPa. FIG. 19(c) shows the coappearance of three elements in the range of COK > 500 mAh/g/GPa and COK*V > 600 mWh/g/GPa.

FIG. 20(a) shows the occurrence of elements in the range of COK > 500 mAh/g/GPa and COK*V e [500, 600] mWh/g/GPa. FIG. 20(b) shows the coappearance of two elements in the range of COK > 500 mAh/g/GPa and COK*V e [500, 600] mWh/g/GPa. FIG. 20(c) shows the coappearance of three elements in the range of COK

> 500 mAh/g/GPa and COK*V e [500, 600] mWh/g/GPa.

FIG. 21 (a) shows the occurrence of elements in the range of COK > 500 mAh/g/GPa and COK*V e [400, 500] mWh/g/GPa. FIG. 21 (b) shows the coappearance of two elements in the range of COK > 500 mAh/g/GPa and COK*V e [400, 500] mWh/g/GPa. FIG. 21 (c) shows the coappearance of three elements in the range of COK

> 500 mAh/g/GPa and COK*V e [400, 500] mWh/g/GPa.

FIG. 22(a) shows the occurrence of elements in the range of COK > 500 mAh/g/GPa and COK*V e [300, 400] mWh/g/GPa. FIG. 22(b) shows the coappearance of two elements in the range of COK > 500 mAh/g/GPa and COK*V e [300, 400] mWh/g/GPa. FIG. 22(c) shows the coappearance of three elements in the range of COK

> 500 mAh/g/GPa and COK*V e [300, 400] mWh/g/GPa. FIG. 22(d) shows the high-throughput calculation results of voltage (y-axis) and lithiation composition over K_Crit (x-axis) for anodic reaction versus Li metal anode for 59,524 material entries within the plotted axes range.

Reference is made to the accompanying drawings throughout the following detailed description. In the drawings, similar symbols typically identify similar components, unless context dictates otherwise. The illustrative implementations described in the detailed description, drawings, and claims are not meant to be limiting. Other implementations may be utilized, and other changes may be made, without departing from the spirit or scope of the subject matter presented here. It will be readily understood that the aspects of the present disclosure, as generally described herein, and illustrated in the figures, can be arranged, substituted, combined, and designed in a wide variety of different configurations, all of which are explicitly contemplated and made part of this disclosure.

DETAILED DESCRIPTION

Embodiments described herein relate to electrochemical cells (e.g., rechargeable solid state batteries) including a cathode, an anode, and a solid state electrolyte disposed between the cathode and the anode. In some embodiments, the anode includes an anode material having a plurality of voids. In some embodiments, the anode is formulated to cause lithium metal to be deposited in the plurality of voids during charging of the electrochemical cell. In some embodiments, the anode material has a local effective modulus of at least about 0.3 GPa causing the anode to be under mechanical constriction. In some embodiments, the anode is formulated to cause lithium metal to be deposited on the anode material during charging of the electrochemical cell. In some embodiments, the anode includes a plurality of particles. In some embodiments, the anode is formulated such that initial charging of the electrochemical cell causes lithium metal to be deposited on the anode. In some embodiments, the lithium metal deposition causes a volume of the plurality of particles to change by less than 300% of an original volume of the plurality of particles. In some embodiments, the cathode includes lithium.

Specifically, the embodiments presented herein provide a solid state battery design that demonstrates a counterintuitive interaction between two important next-generation anode materials of Li metal and silicon (Si). Instead of behaving as a Si anode with strong Li-Si alloying or lithiation reactions, the solid state battery of the present embodiments can significantly modulate Li-Si interaction by constricting the lithiation of Si, and other materials, and converting it to serve as a Li metal anode instead, where the Si matrix can host fast plating and stripping of Li metal homogeneously. Other anode materials that can demonstrate this phenomenon are also proposed herein. The electrochemical cells of the present disclosure may demonstrate an ultra-high current density of from about 0.01 to about 200 mA/cm² (e.g.,19 ~ 32 mA/cm²) without short circuit and a commerciallevel cathode loading of 0.1 -200 mg/cm² (e.g., 15 - 25 mg/cm²) with normal charge and discharge, or 1 -20 mAh/cm² (e.g., 1 - 3 mAh/cm²) area capacity. According to some embodiments, the electrochemical cells or batteries presented herein can be cycled for 1 ,000 - 20,000 cycles (e.g., from 1 ,000 to 2,000 cycles) at 1 -7 minutes (e.g., 3 - 7 minutes), or 5-30 C (e.g., 5 -10 C) rates of charge and discharge.

Lithium metal and silicon are two important battery anode materials with high specific capacities. Specifically, lithium (Li) anodes hold significant importance in the development of advanced rechargeable batteries due to their high specific capacity and low electrochemical potential. However, both lithium metal and silicon anodes face problems electrochemically. The most important issues of Li are related to stripping and dendrite formation. Stripping can occur at a rate that outpaces Li replenishment, resulting in voids forming at the Li- solid electrolyte interface. This accumulation of voids increases local current density and ultimately leads to dendrite growth on the anode's surface. Dendrites, microscopic spiny projections, pose safety concerns as they can breach the battery separator, touch the cathode, and cause short circuits, potentially leading to fires. On the other hand, a 300% volume change after lithiation limits the practical implementation of many types of silicon as anode in liquid electrolyte batteries. For example, micron-scale silicon particles in liquid electrolyte can form a thick solid electrolyte interface (SEI). After the swelling due to the lithiation process, which results in an aggressive volume change, the particle breaks into smaller particles that can further form subsequent fresh SEI layers. This process leads to the formation of isolated smaller silicon particles and the decomposition of electrolyte, causing capacity fading and even safety issues.

Embodiments described herein enable addressing these challenges to fully unlock the potential of Si and Li metal anodes in rechargeable batteries while ensuring their safety and performance. The electrochemical cells of the various embodiments offer a solution that facilitates the use of both lithium and silicon anodes in electrochemical cells delivering desired attributes such as power, energy, cycle life, and low-temperature performance.

Embodiments of electrochemical cells described herein including solid state electrolytes may provide one or more benefits, for example: (1 ) enabling silicon to act as a support structure for lithium plating, which can lead to improved battery cycling performance; (2) allowing fast charging as lithium metal plating dominates the electrochemical process at the anode; (3) showing high robustness even when the loading is increased, with high area capacity; (4) having improved energy density, which is beneficial for various applications (e.g., aerospace applications, electrical vehicles, etc.); (5) preventing or diminishing lithium dendrite formation, especially at high current densities (e.g., through a multilayer electrolyte design and dynamic stability); (6) cycling well at lower temperatures (e.g., 35°C), which is advantageous in certain environments; and (7) improving safety of the electrochemical cell(s) and reducing the risk of short circuit due to formation of dendrites during operation.

Herein, it is discovered that the behavior of silicon can be drastically different in solid state batteries. For example, Si and other materials that would normally be expected to undergo lithiation during charging when used as anode materials can instead act as a support structure for lithium plating.

It was unexpected that Si can serve as a scaffold, with little lithiation, for lithium metal anode applications, since in previous studies of liquid or solid state battery designs, Si was deeply lithiated and behaved as a classic silicon anode (see, e.g., Tan, Darren HS, et al. "Carbon-free high-loading silicon anodes enabled by sulfide solid electrolytes." Science 373.6562 (2021 ): 1494-1499.). This drastic difference between the electrochemical cells of the embodiments presented herein and prior batteries is also reflected in the much superior rate performance of the present cells described herein according to multiple embodiments.

Without wishing to be bound by theory, the environment of the solid state electrochemical cells described herein first creates a thermodynamic metastability for Li plating at the Si surface, as the solid state batteries described herein are mechanically constricted systems, which is not the case with liquid electrolyte batteries. Here the constriction can be from the mechanical strength of each individual particle itself, or be applied to a Si particle from neighboring Si particles in a dense solid layer, or a combination thereof. The constriction can add a strain energy barrier for any volume expansion reaction of Si (or similar materials). In addition, unlike mechanically soft Ag without a Li alloying nucleation barrier, Si has a small nucleation barrier to alloy with Li and a large bulk modulus around 100 GPa to naturally resist expansion reaction in a mechanically constricted solid environment. These factors together may cause a thermodynamic metastability and kinetic stability which creates an energy barrier to prevent deep lithiation of Si, and leads lithium metal plating to dominate. A shallow surface layer of Li-Si alloying, without pulverization, may seed and help fast and homogeneous Li metal deposition. Lithium metal has a yield modulus of only a few MPa; thus, plated lithium can creep in voids and pores between Si particles.

All definitions, as defined and used herein, should be understood to control over dictionary definitions, definitions in documents incorporated by reference, and/or ordinary meanings of the defined terms.

As used herein, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, the term “a member” is intended to mean a single member or a combination of members, “a material” is intended to mean one or more materials, or a combination thereof.

As used herein, in particular embodiments, the terms “about” or “approximately” when preceding a numerical value indicates the value plus or minus a range of 10%. Where a range of values is provided, it is understood that each intervening value, to the tenth of the unit of the lower limit unless the context clearly dictates otherwise, between the upper and lower limit of that range and any other stated or intervening value in that stated range is encompassed within the disclosure. That the upper and lower limits of these smaller ranges can independently be included in the smaller ranges is also encompassed within the disclosure, subject to any specifically excluded limit in the stated range. Where the stated range includes one or both of the limits, ranges excluding either or both of those included limits are also included in the disclosure.

The phrase “and/or,” as used herein in the specification and in the embodiments, should be understood to mean “either or both” of the elements so conjoined, i.e., elements that are conjunctively present in some cases and disjunctively present in other cases. Multiple elements listed with “and/or” should be construed in the same fashion, i.e., “one or more” of the elements so conjoined. Other elements may optionally be present other than the elements specifically identified by the “and/or” clause, whether related or unrelated to those elements specifically identified. Thus, as a non-limiting example, a reference to “A and/or B”, when used in conjunction with open-ended language such as “comprising” can refer, in one embodiment, to A only (optionally including elements other than B); in another embodiment, to B only (optionally including elements other than A); in yet another embodiment, to both A and B (optionally including other elements); etc.

As used herein in the specification and in the embodiments, “or” should be understood to have the same meaning as “and/or” as defined above. For example, when separating items in a list, “or” or “and/or” shall be interpreted as being inclusive, i.e., the inclusion of at least one, but also including more than one of a number or list of elements, and, optionally, additional unlisted items. Only terms clearly indicated to the contrary, such as “only one of” or “exactly one of,” or, when used in the embodiments, “consisting of,” will refer to the inclusion of exactly one element of a number or list of elements. In general, the term “or” as used herein shall only be interpreted as indicating exclusive alternatives (i.e., “one or the other but not both”) when preceded by terms of exclusivity, such as “either,” “one of,” “only one of,” or “exactly one of.” “Consisting essentially of,” when used in the embodiments, shall have its ordinary meaning as used in the field of patent law.

As used herein in the specification and in the embodiments, the phrase “at least one,” in reference to a list of one or more elements, should be understood to mean at least one element selected from any one or more of the elements in the list of elements, but not necessarily including at least one of each and every element specifically listed within the list of elements and not excluding any combinations of elements in the list of elements. This definition also allows that elements may optionally be present other than the elements specifically identified within the list of elements to which the phrase “at least one” refers, whether related or unrelated to those elements specifically identified. Thus, as a non-limiting example, “at least one of A and B” (or, equivalently, “at least one of A or B,” or, equivalently “at least one of A and/or B”) can refer, in one embodiment, to at least one, optionally including more than one, A, with no B present (and optionally including elements other than B); in another embodiment, to at least one, optionally including more than one, B, with no A present (and optionally including elements other than A); in yet another embodiment, to at least one, optionally including more than one, A, and at least one, optionally including more than one, B (and optionally including other elements); etc.

In the embodiments, as well as in the specification above, all transitional phrases such as “comprising,” “including,” “carrying,” “having,” “containing,” “involving,” “holding,” “composed of,” and the like are to be understood to be open-ended, i.e., to mean including but not limited to. Only the transitional phrases “consisting of” and “consisting essentially of” shall be closed or semi-closed transitional phrases, respectively, as set forth in the United States Patent Office Manual of Patent Examining Procedures, Section 21 1 1 .03. As used herein in the specification and in the embodiments, the term “stability,” with respect to solid state electrolytes, refers to the stability of the material to decomposition via reaction with a metal in the anode, e.g., lithium. Stability of solid electrolytes can be determined experimentally.

As used herein in the specification and in the embodiments, the term “Kcrit (COK)” refers to lithiation capacity divided by Kcrit.

As used herein in the specification and in the embodiments the term “lithiation,” with respect to anode materials, refers to the penetration of a material by lithium atoms or ions (e.g., by intercalation, insertion, chemical reaction, etc.), in contrast to plating as lithium metal into the voids (e.g., nano-scale and/or micron- scale voids) of a material (e.g., within or between particles of the material).

As used herein in the specification and in the embodiments, the term “micron-scale,” with respect to anode materials, refers to a material having at least one cross-sectional dimension in the range of 1 -1 ,000 microns.

As used herein in the specification and in the embodiments, the term “nano-scale,” as used herein with respect to anode materials, refers to a material having at least one cross-sectional dimension in the range of 1 nm - 1 ,000 nm.

FIG. 1 is a schematic illustration of an electrochemical cell 100 including a cathode 120 (e.g., LCO, LMO, NCA, NMC, LFP, LMNO, and LATP-coated LMNO, NMC83, NMC81 1 , NMC1 1 1 , NMC532, NMC622, NMC955, etc.), an anode 140 (e.g., particulate Si, SiG composite, etc.), and a solid state electrolyte 130 disposed between the cathode 120 and the anode 140, according to an embodiment. The electrochemical cell 100 includes the cathode 120 disposed on a cathode current collector 1 10. The electrochemical cell 100 includes the anode 140 disposed on an anode current collector 150. In some embodiments, electrochemical cell 100 can be disposed in a housing 160.

In some embodiments, the electrochemical cell 100 demonstrates improved current density of, e.g., about 0.01 -200 mA/cm² (e.g., about 19-32 mA/cm²) with commercially relevant cathode loadings of about 0.1 -200 mg/cm² (e.g., about 15-25 mg/cm²). In addition, the electrochemical cell 100 may have about 1 -20 mAh/cm² (e.g., about 1 -3 mAh/cm²) area capacity and can be cycled for 1 ,000 ~ 20,000 cycles (e.g., 1 ,000-2,000 cycles) at, e.g., 1 -7 minutes (e.g., 3-7 minutes) or 5-30 C (e.g., 5-10 C)-rates of charge and discharge. In some embodiments, the electrochemical cell 100 may include materials (e.g., the solid state electrolyte 130, the anode 140, etc.) which are under mechanical constriction. For example, the anode 140 may be under mechanical constriction which limits lithiation of the anode material to a surface layer of less than about 65 nm. The mechanical constriction may be provided by an external pressure, e.g., compression, e.g., of 5-500 MPa (e.g., 5-10, 10-15, 10-20, 20-30, 25-45, 30-40, 25-50, 35-55, 40-60, 50-75, 50-100, 60-80, 55-70, 65-85, 75-100, 80-90, 80-100, 90-1 10, 105-120, 100-150, 125-175, 150-200, 175-225, 200-250, 225-275, 250-300, 275-350, 325-375, 350-400, 375-425, 400-450, 425-475, or 450-500 MPa, e.g., about 5, 7, 10, 12, 15, 22, 25, 28 ,30, 40, 45, 50, 100, 200, 250, 300, 400, or 500 MPa. The mechanical constriction may be provided by a local effective modulus (K_etf), e.g., due to a combination of volumetric constraint and the modulus of the material(s) of at least 0.3 GPa (e.g., at least 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1 , 2, 3, 4, 5, 6, 7, 8, 9, or 10 GPa). The electrochemical cell 100, in some embodiments, may have both external pressure and contain materials in a design which induces a local effective modulus on the materials. In some embodiments, the anode 140, cathode 120, and solid state electrolytes 130 can use bipolar or parallel stacking to form a battery module. In some embodiments, the area of each layer can be 0.1 cm² - 1 m². In some embodiments, the mechanical construction may cause a surface layer on the anode 140 to have a thickness of less than 500 nm. In some embodiments, the lithium metal can be deposited as a surface layer on the anode 140, and the mechanical construction can cause the surface layer to have a thickness of less than 500 nm.

In some embodiments, the housing 150 can be a pouch, for example, an aluminum pouch, a mica pouch, a polymer pouch, etc. In some embodiments, the housing 150 can be a prismatic cell. The housing 150 can be formed from a strong, rigid and heat-resistant material. In some embodiments, the housing 150 includes iron, iron alloys, aluminum, aluminum alloys, titanium alloys, stainless steel, carbon steel, galvanized steel, carbon compounds and their alloys, plastics, carbon or glass fiber filled plastic, polymers, any other suitable material, or a combination thereof. In some embodiments, the housing 150 may be coated with corrosion or flame resistance material (e.g., TEFLON®, Nylon, aluminum oxide, titanium oxide, corrosion and/or flame resistance paint, etc.). In some embodiments, the housing 150 is configured to be lightweight and occupy minimal volume with respect to the volume of the electrochemical cell 100 in order to maintain power/volume efficiency.

In some embodiments, the anode 140 includes an anode material (not shown). In some embodiments, the anode materials are materials onto which Li can plate during charging without, under the conditions induced by the cell design, lithiating the bulk of the material. Such materials may otherwise be considered to act as anode materials by lithiation, e.g., by insertion or intercalation, when used in anodes of other batteries.

In some embodiments, the anode material may have a plurality of voids (not shown in FIG. 1 ). The voids may be due to gaps between particles, e.g., micron-scale or nano-scale particles. Alternatively, or in addition, the voids may be, e.g., pores or other gaps in a particle that forms the anode material. For example, in some embodiments, the anode material may include porous particles. In some embodiments, the anode material may further include a plurality of voids between the porous particles. In some embodiments, the anode material may include non-porous particles, but the anode material may include a plurality of voids due to spacing between non-porous particles. The voids, in some embodiments, are able to accept Li during charging in the form of Li⁺ ions plating into the voids as Li metal. The voids may have cross-sectional dimensions from a few nm (e.g., 5-10 nm) to 10s of microns (e.g., 10, 20, 30, 40, or 50 pm), e.g., from 5 nm to 50 pm, e.g., from 5 nm to 100 nm (e.g., 5-50, 25-60, 45-80, or 75-100 nm), e.g., from 100 nm to 1 pm (e.g., 100-200, 150-450, 200- 300, 250-600, 400-500, 500-750, 600-800, 700-900, or 900-1 ,000 nm), or e.g., from 1 pm to 50 pm (e.g., 1 - 10, 5-10, 7-15, 12-20, 15-20, 15-30, 20-30, 25-50, 30-40, 35-45, or 40-50 pm). In some embodiments, each of the plurality of voids has a cross-sectional dimension in a range of about 5 nm to about 50 nm.

In some embodiments, the anode material has a high surface area, e.g., a high ratio of surface area to volume and/or mass. The anode material may be in various forms, such as a powder, particle, clay, or solid sheet. An exemplary form may be a powder. In some embodiments, the anode material includes a plurality of particles having a diameter in a range of about 1 pm to about 100 pm.

After providing the formation pressure (i.e., a mechanical pressure during initial charging and discharging of the electrochemical cell 100), in some embodiments, the plurality of voids of the anode 140 may have a volume of from about 0% to about 99%, e.g., 10-15%, 10-20%, 15-30%, 25-50%, 30-40%, 35-50%, or 40-50%, 50- 75%, 40-60%, 55-80%, 65-90%, 60-80%, 75-90%, 80-90%, 85-95%, or 90-99% of the volume of the anode 140.

In some embodiments, the anode material is under mechanical constriction. In some embodiments, the mechanical constriction is caused by at least one of the anode material having a local effective modulus of at least about 0.3 GPa or an external pressure in a range of about 0.05MPa to about 50 MPa exerted on the electrochemical cell. That is, in some embodiments, the anode material having a local effective modulus of at least about 0.3 GPa causes the anode 140 to be under mechanical constriction or an external pressure in a range of about 0.05MPa to about 50 MPa exerted on the electrochemical cell 100 causes the anode 140 to be under mechanical constriction. In some embodiments, the anode material includes at least one of a Si or a Si- graphite composite.

In some embodiments, the anode material can be Si (e.g., pristine silicon, or silicon mixed with another material, e.g., graphite (as a composite, e.g., a Si-graphite composite formed of micron-scale and/or nanoscale Si and graphite particles, i.e. , SiG). Other suitable anode materials have been investigated in the present disclosure (see FIGS. 12(a)-16(c)). In some embodiments, suitable anode materials may include those having a capacity over Kcrit (COK) of > 500 mAh/g/GPa and (Kent x V) (COK*V) of > 600 mWh/g/GPa, such as Mg metal or a binary or ternary alloys of Mg (e.g., LiMgs, MgyAli , Mgi49Lit, Mgi4gBai , Mgi4gCai , MgugSi , Mgi4gAgi , Mg?Bi , or NaiMgi4Bi). Where capacity is from the theoretical lithiation composition of the material, V is the average lithiation voltage of the anode 140 versus Li⁺/Li, and Kcrit is the critical modulus at which chemical reaction between Li metal and the material can be suppressed. Capacity over Kcrit describes how sensitive the lithiation capacity of a material is to being suppressed by mechanical constriction and converted to the lithium plating capacity of interest. Other suitable materials are those having a capacity over Kcrit (COK) of > 500 mAh/g/GPa and (Kcrit x V) (COK*V) of e [500, 600] mWh/g/GPa, such as alloys of Mg of formula MgxSh x, MgsAI, LixMgi-x, Mg4AliSi4, or Li_xMg_ySii x-_y, metal-doped Mg of formula Mg_xM’_yM”i-x-_y (where x > 0.8 y < 0.2) (e.g., Mgi4Ali Fei), doped MgO of formula (MgO)xA_yB_zOi x-_y-z (x > 0.9), or binary Mg compounds (e.g., MggP). Other suitable materials are those having a capacity over Kcrit (COK) of > 500 mAh/g/GPa and COK*V e [300, 500] mWh/g/GPa such as doped MgO of formula (MgO)xA_yB_zOi x-_y-z (x > 0.7) (e.g., Mg3AliO4, LhMgeBiO? and KiMg TiiO ), compounds of formula MgxSh x, compounds of formula Mg_xSi_yOi x-_y, or Mg metal alloys of formula MgxM’_yM”i-_x-y (e.g., Mg_xAli-x, e.g., Mgi?Ali2 and its doped compounds such as MgieAhaLii). Suitable materials may be those that undergo a self-limiting reaction with lithium under mechanical constriction to form a surface layer (e.g., of 65 nm or thinner, e.g., about 60, 55, 50, 45, 40, 35, 30, 25, 20, 15, 10, or 5 nm, e.g., 5-10 nm, 8-15 nm, 10-20 nm, 15-25 nm, 20-40 nm, 30-60 nm, 45-55 nm, 50-60 nm, or 55-65 nm). In some embodiments, the anode materials may be formed of particles, and the particles may be of 1 -100 pm in diameter.

In some embodiments, the anode materials included in the anode 140 may also include a coating (e.g., a coating on the particles which form the material) or surface layer or coating that inhibits bulk lithiation. This may be a surface layer as described herein, e.g., caused by lithiation. Alternatively, a surface layer may be separately included, e.g., by coating, e.g., by self-assembly onto/from the anode material (e.g., using solution or vapor techniques, e.g., atomic layer deposition, chemical vapor deposition, electroless plating, polymer grafting, etc.). In some embodiments, anode materials may display no, or minimal, change in volume or form as a result of the electrochemical cell 100 operation. For example, the anode materials may show no cracking or swelling during charging or discharging (e.g., as observable by SEM). A volume of the anode materials (e.g., particles) after a first charging may be <300% of an original particle volume. For example, the volume of the particles after the first charging may be 100-300% (e.g., 100-1 10%, 100-120%, 100-125%, 1 10-140%, 1 15-135%, 125- 135%, 125-150%, 140-150%, 150-200%, 150-250%, 150-300%, 200-250%, 200-300%, 250-300%, etc., e.g., about 100%, 105%, 1 10%, 1 15%, 120%, 125%, 130%, 135%, 140%, 145%, 150%, 165%, 170%, 175%, 180%, 185%, 190%, 195%, 200%, 205%, 210%, 215%, 220%, 225%, 230%, 235%, 240%, 245%, 250%, 255%, 260%, 265%, 270%, 275%, 280%, 285%, 290%, 295%, or 299% ) of the original volume.

In some embodiments, the volume of the particles after the first charging may be at least about 100%, at least about 105%, at least about 1 10%, at least about 1 15%, at least about 120%, at least about 125%, at least about 130%, at least about 135%, at least about 140%, at least about 145%, at least about 150%, at least about 165%, at least about 170%, at least about 175%, at least about 180%, at least about 185%, at least about 190%, at least about 195%, at least about 200%, at least about 205%, at least about 210%, at least about 215%, at least about 220%, at least about 225%, at least about 230%, at least about 235%, at least about 240%, at least about 245%, or at least about 250% of the original volume. In some embodiments, the volume of the particles after the first charging may be no more than about 300%, no more than about 295%, no more than about 290%, no more than about 285%, no more than about 280%, no more than about 275%, no more than about 270%, no more than about 265%, no more than about 260%, no more than about 255%, no more than about 250%, no more than about 240%, no more than about 230%, no more than about 220%, no more than about 210%, or no more than about 200% of the original volume. Combinations of the abovereferenced volume percentages are also possible (e.g., at least about 150% and no more than about 300% by volume or at least about 150% and no more than about 200% by volume), inclusive of all values and ranges therebetween.

Alternatively, or in addition, an average particle diameter of the anode materials after 10 charge and discharge cycles may be >70% of an original particle diameter (e.g., 70-1 15% of an original particle diameter, e.g., 70- 75%, 70-80%, 80-100%, 75-85%, 80-90%, 85-95%, 85-100%, 90-100%, 90-1 10%, 95-1 10%, 95-105%, 100- 1 10%, or 105-1 15%, e.g., of an original particle diameter, e.g., about 70%, 75%, 80%, 85%, 90%, 95%, 100%, 105%, 1 10%, or 1 15% of the original particle diameter). In some embodiments, a volume of the plurality of voids may change by less than 100% (e.g., from 1 -100%, 1 -50%, 1 -10%, 5-15%, 1 -25%, 20-40%, 30-40%, 25-50%, 40-50%, or 50-100% or less than 1 %) during charging and/or discharging of the battery. In some embodiments, the particles swell by less than 300% (e.g., from 1 -50%, 1 -10%, 5-15%, 1 -25%, 20-40%, 30- 40%, 25-50%, 40-50%, 50-100%, 50-150%, 50-200%, 50-250%, or 50-300% or less than 1 %) during charging and/or discharging of the electrochemical cell 100.

In some embodiments, the anode 140 may be deposited on an appropriate substrate, e.g., a fluoropolymer or carbon. For example, liquefied polytetrafluoroethylene (PTFE) can be used as the binder when making solutions of electrode materials for deposition onto a substrate. Other binders known in the art may be used as well in some embodiments. The anode materials described herein can be used without any additives. Alternatively, the anode material may have additives to enhance its physical and/or ion conducting properties. For example, the anode materials may have an additive that modifies the surface area exposed to the solid electrolyte, such as carbon. Other additives known in the art may be used in some embodiments. The mixture of Li and other metal or metals can form a 2D parallel layer or a 3D structure. In some embodiments, the loading of the Li in the anode 140 can be 0-50 mg/cm².

In some embodiments, the cathode 120 includes cathode materials (e.g., materials including lithium). Cathode materials can be chosen to have optimum properties for ion transport. For example, the cathode 120 may be LiNi0.8Mn0.1Co0.1O2 (NMC81 1 ) due to its high capacity, energy density, and also cost effectiveness due to the decreased composition of the expensive Co element. Other suitable cathode materials known in the art for use as electrodes in solid state electrolyte batteries can also be used in some embodiments to construct the electrochemical cell 100.

In some embodiments, the cathode 120 can include, e.g., LiNi0.sMn0.1Co0.1O2 (NMC81 1 ), LiNi0.33Mn0.33Co0.33O2 (NMC1 1 1 ), LiNi0.5Mn0.3Co0.2O2 (NMC532), LiNi0.6Mn0.2Co0.2O2 (NMC622), LiNi0.9Mn0.05Co0.05O2 (NMC955), LiNixMn_yCo(i-x-y)O2 (0<x,y<1 ), LiNixCo_yAI(i-x-_y)C>2 (0<x,y<1 ), LiMn2O4, LiMnO2, LiNiC>2, Lii_+zNixMn_yCo(i-x-_y-z)O2 (0<x,y,z<1 ), Lii_+zNixMn_yCowAI(i-x-_y-z-s)O2 (0<x,y,z,s<1 ), Lii_+zNixMn_yCo_sW(i-x-_y-z-s)O2 (0<x,y,z,w<1 ), V2O5, selenium, sulfur, selenium-sulfur compound, LiCoO2 (LCO), LiFePO4, LiNio.5Mn1.5O4, Li2CoPO4F, LiNiPO4, Li2Ni(PO4)F, LiMnF4, LiFeF4, or LiCo0.5Mn1.5O4. The cathode can be coated with LiNbOs, LiTaOs Li2ZrOs, LiNbxTai-xOs (0<x<1 ), yLi2ZrO3-(1 -y)LiNbxTai-xO3 (0<x, y<1 ), AI2O3, TiO2, ZrO2, AIF3, MgF2, SiO2, ZnS, ZnO, Li₄SiO₄ U3PO4. LisInCle, Lii_+xAlxTi2-x(PO4)3(0<x<2), LiMn2O4, LilnO2-Lil, LiePSsCI, Li AIO2, a polymer, or carbon. In some embodiments, the cathode 120 may include a polymer and/or carbon black. In some embodiments, the cathode 120 may include a first electrolyte and/or a second solid electrolyte including a polymer.

In some embodiments, the cathode 120 may be a solid piece of the material, or alternatively, may be deposited on an appropriate substrate, e.g., a fluoropolymer or carbon. For example, liquefied polytetrafluoroethylene (PTFE) can be used as the binder when making solutions of cathode materials for deposition onto a substrate. Other binders are known in the art. In some embodiments, the cathode material can be used without any additives. Alternatively, the cathode material may have additives to enhance its physical and/or ion conducting properties. For example, the cathode materials may have an additive that modifies the surface area exposed to the solid electrolyte, such as carbon. In some embodiments, other additives known in the art may be applied as well.

In some embodiments, the cathode 120 can be mixed with polymer and/or carbon. Examples of polymers may include polyethylene oxide, polyvinylidene fluoride, poly(vinylidene fluoride-co-hexafluoropropylene), poly(ethy I methacrylate), or poly(vinylidene fluoride-co-trifluoroethylene). The particle size of cathode materials can be between about 1 nm to about 30 pm. In some embodiments, the loading of the cathode 120 can be between about 0.1 mg/cm² and about 100 mg/cm². In some embodiments, the thickness of the cathode 120 can be from about 5 pm to about 2,000 pm. The cathode 120 may be mixed with solid state electrolyte materials, described herein, to provide increased cathode capacity. Other cathode materials such as selenium or sulfur that exhibit promising high capacity and energy density also show much better cycling performance in our multilayer design than the single layer design.

In some embodiments, the cathode 120 can be mixed with polymer and carbon black, and the solid electrolyte 130 can be mixed with polymer. Examples of polymers may include, but are not limited to polyethylene oxide, polyvinylidene fluoride, poly(vinylidene fluoride-co-hexafluoropropylene), poly(ethyl methacrylate), or poly(vinylidene fluoride-co-trifluoroethylene), any other suitable polymer, or any suitable combination thereof. In some embodiments, the thickness of the solid electrolyte 130 is between about 5 and about 1 ,000 pm. In some embodiments, the thickness of the cathode 120 can be between about 5 pm and about 2,000 pm.

In some embodiments, the solid state electrolyte (SSE) 130 may include inorganic solid electrolytes, e.g., crystalline or glassy inorganic lattices with high ionic conductivity, in which ions (e.g., Li⁺ ions) can diffuse through the lattice. The SSE 130 may include, for example, oxides, phosphates, or sulfides of lithium (e.g., LGPS, LiSiPS, LiPS, Li5.5PS4.5CI1.5 (LSPCI1.5), LiePSsCh.o (LPSCI1.0), any other suitable electrolyte material or combination thereof). Exemplary solid state electrolyte materials are listed below.

Other solid state electrolyte materials that may be suitable include sulfide solid electrolytes, e.g., SixPySz, SiP2Si2, or p/y-PS4. Other solid state electrolytes include, but are not limited to, germanium solid electrolytes, e.g., Ge_aPbS_c, or GeP2Si2, tin solid electrolytes, e.g., SndPeSt, or SnP2Si2, iodine solid electrolytes, e.g., P2S8I crystals, glass electrolytes, e.g., alkali metal-sulfide-P2Ss electrolytes or alkali metal-sulfide-P2S5- alkali metal- halide electrolytes, or glass-ceramic electrolytes, e.g., alkali metal-PgSh-i electrolytes. Other solid state electrolyte materials are known in the art. The solid state electrolyte 130 may be in various forms, such as a powder, particle, clay, or solid sheet. In some embodiments, the solid state electrolyte is a powder.

In some embodiments, the solid state electrolyte 130 may be deposited or cast on an appropriate substrate, e.g., a Polyester (PET) film, a cathode, an anode, or other layers of solid electrolytes. For example, Nitrile rubber (NBR), Acrylate rubber (ABR), Polyisobutene (PIB) have been used as the binder when making solutions of electrolyte materials for deposition onto a substrate. Other binders are known in the art. The solid state electrolyte 130 may be mixed with solvents (e.g., p-xylene, isobutyl isobutyrate or a mixture thereof, e.g., anhydrous p-xylene and isobutyl isobutyrate (1 :1 vol/vol)) and binders (e.g., a polymer, e.g., an arylate polymer, e.g., from 0.5% to 5 wt%) to prepare a slurry for layer formation. In some embodiments, the solid state electrolyte 130 may include multiple layers of electrolytes that can be deposited or cast or transferred to a substrate layer-by-layer. The multilayer may contain ‘n’ layers of solid state electrolytes (where n = e.g., 1 , 2, 3, 4, 5, 6, 7, 8, 9, 10, etc.).

In some embodiments, the solid state electrolyte 130 may include a core-shell particles, e.g., core-shell LPSCI- X (where X is a halide) or LGPS (Li GeP2Si2), examples of which are described in PCT Publication No. WO 2019/104181 , PCT Publication No. WO 2020/1 12843, and PCT Publication No. WO2022/094412, each of which are incorporated by referenced herein in their entirety. LGPS (LiioGeP2Si2) may also adopt a core-shell particle structure. Solid state electrolyte particles, e.g., core-shell particles, may have a cross sectional dimension, e.g., diameter, of between about 1 nm and about 30 pm, e.g., about 1 -100 nm (e.g., about 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, or 100 nm), e.g., about 100-1 ,000 nm (e.g., about 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, or 1 ,000 nm), e.g., about 1 -10 gm (e.g., about 1 gm, 2 gm, 3 gm, 4 gm, 5 gm, 6 gm, 7 gm, 8 gm, 9 gm, or 10 gm), or, e.g., about 10-30 gm (e.g., about 10 gm, 12 gm, 13 gm, 14 gm, 15 gm, 16 gm, 17 gm, 18 gm, 19 gm, 20 gm, 21 gm, 22 gm, 23 gm, 24 gm, 25 gm, 26 gm, 27 gm, 28 gm, 29 gm, or 30 gm). In core-shell particles, the shell may make up from about 0.1 % to about 99.9 % of the particle, e.g., about 1 -10 %, about 10-20 %, about 20-30 %, about 25-50 %, about 40-60%, about 50-75%, about 60-80 %, about 75-90 %, or about 80-99 % of the particle, by, e.g., volume or mass. Stability may be determined experimentally.

In some embodiments, the solid state electrolyte 130 in the electrochemical cell 100 may include solid state electrolyte (SSE) multilayers, e.g., including two, three or more layers and two or more solid state electrolytes with different stabilities. The solid state electrolytes may be arranged such that the less stable electrolyte is sandwiched between more stable electrolyte(s). Localized decomposition of the less stable electrolyte in SSE multilayers can block the formation or progression of cracks in the multilayer and arrest dendrite progress.

In some embodiments, the solid state electrolyte 130 (e.g., the solid state electrolyte multilayer) may be under mechanical constriction. Mechanical constriction of the solid state electrolyte 130 can limit the extent of chemical or electrochemical decomposition of solid state electrolyte materials by volumetric constraint. Local stress on the order of a few GPa up to the mechanical modulus of the solid state electrolyte 130, may be generated from mechanical constriction. The mechanical constriction can be implemented by an external pressure applied to the electrochemical cell 100 of at least 0.1 MPa up to several hundred MPa. The level of external pressure for a battery is determined by the battery material, material processing, and battery assembly methods. Mechanical constriction may be provided by a formation pressure from cold and/or hot and/or warm isotropic and/or anisotropic press and/or rolling with the external pressure on the order of 0.1 MPa to 1 ,000 MPa and temperature at 25 °C-500 °C. Examples of suitable assembly methods include, but are not limited to, warm isotropic pressing (WIP), cold isotropic pressing (CIP), and hydraulic cold pressing of the electrochemical cell 100 or housing 160 (e.g., a pouch). The mechanical constriction may result from an applied pressure of at least 0.05 MPa, e.g., at least 0.1 MPa, 0.5 MPa, 1 MPa, 5 MPa, 10 MPa, 15 MPa or 20 MPa, e.g., about 0.05 MPa to about 50 MPa, e.g., about 0.05 MPa to about 0.1 MPa, about 0.075 MPa to about 0.15 MPa, about 0.1 MPa to about 1 MPa, about 0.1 MPa to about 10 MPa, about 1 MPa to about 30 MPa, about 20 MPa to about 40 MPa, about 30 MPa to about 50 MPa, about 40 MPa to about 60 MPa, about 50 MPa to about 70 MPa, about 60 MPa to about 80 MPa, about 70 MPa to about 90 MPa, or about 80 MPa to about 100 MPa, about 100 MPa to about 200 MPa, about 200 MPa to about 400 MPa, about 300 MPa to about 500 MPa, about 400 MPa to about 600 MPa, about 500 MPa to about 700 MPa, about 600 MPa to about 800 MPa, about 700 MPa to about 900 MPa, or about 800 MPa to about 1 ,000 MPa, e.g., about 70 MPa, about 75 MPa, about 80 MPa, about 85 MPa, about 90 MPa, about 95 MPa, about 100 MPa, about 150 MPa, about 200 MPa, about 250 MPa, about 300 MPa, about 350 MPa, about 400 MPa, about 450 MPa, about 500 MPa, about 550 MPa, about 600 MPa, about 650 MPa, about 700 MPa, about 750 MPa, about 800 MPa about 850 MPa, about 900 MPa, about 950 MPa, or about 1 ,000 MPa. Greater mechanical constriction may be applied during battery fabrication. After providing the formation pressure, the cathode 120 and/or the solid state electrolyte 130 (e.g., the solid state electrolyte multilayer) may have a porosity of from about 0% to about 50%, from about 5% to about 50%, from about 10% to about 50%, from about 20% to about 50%, from about 30% to about 50%, by volume. In some embodiments, the mechanical constriction is sufficient to raise the local effective modulus above Kent, thereby preventing decomposition, or such that a local stress field caused by decomposition of the solid state electrolyte raises K_etf above Kent, thereby arresting decomposition.

In some embodiments, when the electrochemical cell 100 is operating, the local stress can be maintained by applying an operational stack pressure on the order of between 0 MPa and 1 ,000 MPa (e.g., in a range of about 1 MPa to about 50 MPa, inclusive). The operational stack pressure can be applied by the mechanical stress from the housing 160 (e.g., battery case or pouch cell made of steel, aluminum, plastic, polymer, as well as their 3D structures), and/or from a hydraulic press made by gel or any liquid sealed in an environment surrounding the pouch cell. The external pressure may also change periodically during battery cycling, e.g., through a passive response system, e.g., springs, or, e.g., an active response system, e.g., controlled by pressure sensors and programmed electronic devices. Alternatively, the local stress may be maintained without applying an operational stack pressure.

In some embodiments, the anode current collector 150 may be a thin metal sheet, for example, a conductive metal sheet (e.g., aluminum, copper, stainless steel). In some embodiments, there may be layers of other materials between the anode current collector 150 and the anode 140. In addition to the anode material described herein, the anodes 140 may include Li metal. In some embodiments, the anode current collector 150 may further include a lithium metal foil disposed on the anode current collector 150. In some embodiments, the lithium metal can also mix or alloy with Na, Mg, Al, Si, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Zn, Ga, Ge, As, Rb, Sr, Y, Zr, Nb, Mo, Ag, Cd, In, Sn, Sb, Bi, Cs, Te, or a combination thereof to form one single layer. In some embodiments, the anode current collector 150 may include copper, aluminum, nickel, titanium, or any combination thereof.

In some embodiments, the cathode current collector 1 10 may be a thin metal sheet (e.g., aluminum, copper, a carbon based foil). In some embodiments, the cathode current collector 1 10 can include aluminum, stainless steel or any other suitable current collector material.

FIG. 2 is a cross-sectional illustration of an electrochemical cell 200 including an anode 240 disposed on an anode current collector 250 a cathode 220 disposed on a cathode current collector 210 and a solid state electrolyte 230 disposed between the cathode 220 and the anode 240, according to an embodiment. In some embodiments, the electrochemical cell 200 can be the same or substantially similar to the electrochemical cell 100 as described above with reference to FIG. 1 . In some embodiments, the anode 240 including an anode material and disposed on the anode current collector 250, the cathode 220 disposed on the cathode current collector 210, and the solid state electrolyte 230 disposed between the cathode 220 and the anode 240 may be the same or substantially similar to the anode 140, the anode current collector 150, the cathode 120, the cathode current collector 1 10, and the solid state electrolyte 130, respectively, described with respect to FIG. 1 . In some embodiments, the electrochemical cell 200 can be under a mechanical constriction (P) as described above with respect to FIG. 1 .

In some embodiments, the anode 240 includes particles 242 (e.g., porous or non-porous). In some embodiments, anode 240 may include a plurality of voids 244 present between the particles 242. In some embodiments, the particles 242 may have a particles size of about 1 pm to about 100 pm, inclusive, e.g., about 1 -10 pm (e.g., about 1 -2 pm, 1 -5 nm, 2-3 pm, 3-4 pm, 4-5 pm, 5-10 pm, 5-6 pm, 6-7 pm, 7-8 pm, 8-9 pm, or 9-10 gm, e.g., about 1 gm, 2 gm, 3 gm, 4 gm, 5 gm, 6 gm, 7 gm, 8 gm, 9 gm, or 10 gm), or, e.g., about I Q- 100 gm (e.g., about 10-20 gm, 10-25 gm, 10-50 gm, 20-30 gm, 25-50 gm, 30-40 gm, 40-50 gm, 50-60 gm, 50-75 gm, 60-70 gm, 75-100 gm, 70-80 gm, 80-90 gm, or 90-100 gm, e.g., about 10 gm, 12 gm, 13 gm, 14 gm, 15 gm, 16 gm, 17 gm, 18 gm, 19 gm, 20 gm, 21 gm, 22 gm, 23 gm, 24 gm, 25 gm, 26 gm, 27 gm, 28 gm, 29 gm, 30 gm, 40 gm, 50 gm, 60 gm, 70 gm, 80 gm, 90 gm, or 100 gm).

In some embodiments, the particles 242 may have a particles size of 1 nm to 1 ,000 nm, inclusive, e.g., about 1 -100 nm (e.g., about 1 -10 nm, 1 -25 nm, 10-20 nm, 20-30 nm, 25-50 nm, 30-40 nm, 40-50 nm, 50-60 nm, SO- 75 nm, 60-70 nm, 70-80 nm, 75-100 nm, 80-90 nm, or 90-100 nm, e.g., about 1 nm, 5 nm, 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, or 100 nm), e.g., about 100-1 ,000 nm (e.g., about 100-1 10 nm, 100-125 nm, 100-200 nm, 200-300 nm, 250-500 nm, 300-400 nm, 400-500 nm, 500-600 nm, 500-750 nm, 600-700 nm, 700-800 nm, 750-1000 nm, 800-900 nm, or 900-1 ,000 nm, e.g., about 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, or 1 ,000 nm).

In some embodiments, the plurality of voids 244 may be formed between the particles 242. In some embodiments, the voids 244 may be formed due to gaps between particles 242, e.g., micron-scale or nanoscale particles. Alternatively, or in addition, the voids 244 may be, e.g., pores or other gaps in a particle 242 that forms the anode material. In some embodiments, the particles 242 may be porous and/or the plurality of voids 244 may be formed between the particles 242. In some embodiments, the anode material may further include a plurality of voids between the porous particles. In some embodiments, the anode material may include non-porous particles, but the anode material may include the plurality of voids 244 due to spacing between non-porous particles. The voids 244, in some embodiments, are able to accept Li during charging in the form of Li⁺ ions plating into the voids as Li metal. The voids 244 may have cross-sectional dimensions from a few nm (e.g., 5-10 nm) to 10s of microns (e.g., 10, 20, 30, 40, or 50 pm), e.g., from 5 nm to 50 gm, e.g., from 5 nm to 100 nm (e.g., 5-50, 25-60, 45-80, or 75-100 nm), e.g., from 100 nm to 1 gm (e.g., 100-200, 150-450, 200-300, 250-600, 400-500, 500-750, 600-800, 700-900, or 900-1 ,000 nm), or e.g., from 1 gm to 50 pm (e.g., 1 -10, 5-10, 7-15, 12-20, 15-20, 15-30, 20-30, 25-50, 30-40, 35-45, or 40-50 gm). In some embodiments, each of the plurality of voids 244 has a cross-sectional dimension in a range of about 5 nm to about 50 nm.

After providing the formation pressure, in some embodiments, the voids 244 of the anode 240 may be 0% - 99%, e.g., 10-15%, 10-20%, 15-30%, 25-50%, 30-40%, 35-50%, or 40-50%, 50-75%, 40-60%, 55-80%, 65- 90%, 60-80%, 75-90%, 80-90%, 85-95%, or 90-99% by the volume of the anode 140. In some embodiments, the voids 244 of the anode 240 may have a volume of at least about 3%, at least about 5%, at least about 7%, at least about 10%, at least about 15%, at least about 20%, at least about 25% , at least about 30% , at least about 35%, at least about 40%, at least about 45% , at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, or at least about 95% of the volume of the anode 140.

FIG. 3 is a cross-sectional illustration of an electrochemical cell 300 including an anode 340 disposed on an anode current collector 350 a cathode 320 disposed on a cathode current collector 310 and a solid state electrolyte 330 disposed between the cathode 320 and the anode 340, according to an embodiment. In some embodiments, the solid state electrolyte 330 may include solid state electrolyte (SSE) multilayers (i.e., at least two of the layers 332, 334 and 336 as described herein) with different stabilities. The solid state electrolytes layers may be arranged such that the less stable electrolyte layer may be sandwiched between more stable electrolyte layer(s). Localized decomposition of the less stable electrolyte in SSE multilayers can block the formation or progression of cracks in the multilayer and arrest dendrite progress.

In some embodiments, the electrochemical cell 300 can be the same or substantially similar to the electrochemical cell 100 as described above with reference to FIG. 1 . In some embodiments, the anode 340 including an anode material and disposed on the anode current collector 350, the cathode 320 disposed on the cathode current collector 310, and the solid state electrolyte 330 disposed between the cathode 320 and the anode 340 may be the same or substantially similar to the anode 140, 240, the anode current collector 150, 250, the cathode 120, 220, the cathode current collector 1 10, 210 and the solid state electrolyte 130, 230 respectively, described with respect to FIG. 1 and FIG. 2. In some embodiments, the electrochemical cell 300 can be under a mechanical constriction (P) as described above with respect to FIG. 1 .

In some embodiments, the solid state multilayer 330 may include a first solid state electrolyte 332 (e.g., LPSCI), a second solid state electrolyte 334 (e.g., LGPS, LSnPS, etc.), and optionally a third solid state electrolyte 336 (e.g., LPSCI). In some embodiments, the first solid state electrolyte 332 is more stable with lithium metal than a second solid state electrolyte 334. The second solid state electrolyte 334 may be separated from the anode 340 by the first solid state electrolyte 332. The multilayer 330, in some embodiments, may contain ‘n’ layers of the second solid state electrolyte 334 and ‘n’ layers of the one or more first solid state electrolytes 332 (where n = e.g., 2, 3, 4, 5, 6, 7, 8, 9, 10, etc.).

The solid state multilayer 330 may alternatively be arranged in, e.g., a “sandwich” structure, e.g., with one layer of the second solid state electrolyte 334 between two layers of the one or more first solid state electrolytes 332 (e.g., LPSCI-LGPS or LPSCI-LGPS-LPSCI). Alternatively, the multilayer may contain ‘n’ layers of the second solid state electrolyte 334 and ‘n’ or ‘n+1 ’ layers of the one or more first solid state electrolytes 332 (where n = e.g., 1 , 2, 3, 4, 5, 6, 7, 8, 9, 10, etc.).

In some embodiments, the second solid state electrolyte 334 may be less stable with lithium metal than one or more first solid state electrolyte layers 332 and 336. Such an arrangement can allow the first solid state electrolyte layer 332 to protect the second solid state electrolyte layer 334 from, e.g., large-scale decomposition, while confined localized decomposition of the second solid state electrolyte 334 arrests the progression of metal dendrites. The multilayer 330, in some embodiments, may include multiple different first solid state electrolytes 332; for example, at least two different first solid state electrolytes 332, e.g., a solid state electrolyte multilayer, may include two different solid state electrolytes selected from suitable solid state electrolytes listed below.

The multilayer design is not limited to any specific materials, and many electrolytes can work in the central layer, as long as the second solid state electrolyte 334 and/or the third solid state electrolyte 336 can show such well-constrained decomposition with Li dendrite under mechanical constriction. Such solid state electrolytes include, but are not limited to LGPS, LSPS, LSP(Sb)S, which show similarly stable cycling.

Following this design principle, a broad range of solid state electrolytes can be included as the one or more first solid state electrolytes 332 or the second electrolyte 334, as long as they are appropriately placed relative to each other in the multilayer electrolyte 330 according to their relative stabilities, e.g., polymers, gels, or sulfides, halides, oxides, phosphates and nitrates, as listed below.

The stability of the multilayer structure solid state electrolyte 330 takes advantage of relative chemical and/or electrochemical stabilities, which are not sensitive to the thickness or the micron crack density of the electrolyte layers. This strategy of incorporating instability by design is different from the conventional wisdom in the field to improve electrochemical cell stability using solid state electrolytes to mechanically block the Li dendrite penetration, which is generally performed using a thick and crack-free electrolyte layer. The flexibility and versality inherent in the multilayer solid state electrolyte 330 included in the electrochemical cell 300 described herein make them readily compatible with mass production procedures in battery industry, where the thickness and mechanical flexibility of the electrolyte 330 layer can be further optimized in the future without sacrificing the safety and performance.

To quantify the electrochemical stability of solid state electrolytes and their interfaces in such a solid state battery (SSB), a constrained ensemble description has been developed, where decompositions with a positive reaction strain can in principle be suppressed through a metastability if the local effective modulus (e.g., from being made into solid state batteries), K_en, is sufficient. K_en in the unit of GPa reflects the complicated coupling of microstructures, the mechanical strength of materials, and the stack pressure of battery devices.

Multiple electrolyte layers 330 can be directly cast onto the anode 340 and/or cathode 320 layer-by-layer. Alternatively, the electrolyte 330 can also be cast onto another subtract layer-by-layer, then transferred to the anode 340 and/or cathode 320 with a press, e.g., using calendar press, hydraulic press, or isostatic press.

In certain embodiments, the solid state electrolyte (i.e., the first solid state electrolyte 332 and/or the second solid state electrolyte 334 and/or the third solid state electrolyte 336) can be selected from any suitable Li containing solid state electrolyte. For example, in some embodiments, the first solid state electrolyte 332 can be selected from the group consisting of LiePSsCI, Li6±yPS5±_yCli±_y, Li5.5PS4.5CI1.5, Li5.5±yPS4.5±yCh.5±y, Li6±yPS5±yBn±y, Li 6±y PSs±_y 11 ±y , Li6±yPSs±yFl±y, LiePSsCIl-xFx (0SX<C), Li6±yPSs±y(Cll-xFx)l±y (0SX<C), Li6±yPSs±y(Cll- xBrx)l±y (0<X<C), Li 6±y PSs±_y (C 11 -x lx) 1 ±y (O^X^C), Li6±yPS5±y(BrulvFwCll-u-v-w)l±y (0^U,V,W^C), LixPySz(BrulvFwCll-u-v- v)e, or any material from this group with one or more elements replaced by a homogeneous element, wherein 0< a, b, d, p, q, w, x, y, z, u, v, and w<1 unless otherwise specified, wherein C is the critical doping content, above which the electrolyte become less stable, and wherein C can be varied for u, v, and w; 0<C<1 .

In some embodiments, the second solid state electrolyte 334 can be selected from the group consisting of Li GeP2Sl2, LilO±xGei±yP2±pSl2±q, LilO±xGei±y(PpSb2-p)Sl2±q, Li SiP2Sl2, LilO±xSil±yP₂±pSl2±q, Li SnP2Sl2, LilO±xSm±yP2±pSl2±q, LilO±xSni±y(PpSb2-p)Sl2±q, Li6±yP(1-x)SbxS5±y(Br_ulvFwCll-u-v-w)l±y (x>c, 0<U,V,W<1), Li6±yP(1- x)SbxS5±_y(Br_ulvFwCll-u-v-w)l±y (U,V,W>C, 0<X<1 ), Li3±xPl±yS4±z, Li9.54Sil .74P1.44S11.7CI0.3, Lil0±xSil±yP2±pSl2±qOw,

Lig.54Sil ,74(PxSbl -x)l .44S11.7CI0.3, LilO±xSil±y(PxSbl-x)2±pSl2±qClw, LilO±xSil±y(PxSbl-x)2±pSl2±q(FuBr_vlwCll-u-v-w)z, La, In), nLiCI-LiOH-GaFs ( n = 2, 3, 4), and nLiX-GaFs (X = Cl, Br, n = 2, 3, 4), or any material from this group with one or more elements replaced by a homogeneous element, wherein 0< a, b, d, p, q, w, x, y, z, u, v, and w<1 unless otherwise specified, wherein C is the critical doping content, above which the electrolyte become less stable, and wherein C can be varied for u, v, and w; 0<C<1 .

In some embodiments, the first solid state electrolyte layer 332 and/or second solid state electrolyte layer 334 may have a core-shell particle structure. In certain embodiments, the core-shell particles may have a core conductivity and a shell conductivity that are different. In some embodiments, the core conductivity may be higher than the shell conductivity. In some embodiments, the core-shell particles may have a core composition and a shell composition, and the core composition may be different from the shell composition, e.g., having different non-stoichiometric weightings of Li. A different core and shell compositions can provide different properties, e.g., Kent, Ehuii, conductivity, etc., e.g., the shell composition may have a smaller Kent or a more negative Ehuii than the core, or, e.g., the core conductivity may be higher than the shell conductivity, or any combination thereof.

In some embodiments, the first solid state electrolyte 332 and/or the second solid state electrolyte 334 may be selected from the group consisting of Li _{0.3} Cl _{0.6} Er _{0.1 }, Li _{0.3} Cl _{0.6} Y _{0.1 }, Li _{0.3} Cl _{0.6} Sc _{0.1 }, Li J0.291 } O _{0.5} Zr J0.083} La _{0.125}, Li J0.271 } O J0.508} Ga J0.008} Zr J0.084} La _{0.127}, Li J0.265} O _{0.510} Al _{0.010} Zr J0.085} La _{0.127}, Li J0.276} O _{0.510} Zr J0.063} Nb J0.021 } La _{0.127}, Li _{0.270} O JO.515} Zr J0.070} La _{0.128} W J0.015}, Li _{0.400-x} B _{0.000-y} O _{0.000-z} Al _{3.503+w} Si J0.133-I} S _{0.465-m}, Li _{0.3+x} Cl _{0.6-y} Sc _{0.1 -z}, Li _{0.3+x} Cl _{0.6- y} In _{0.1 -z}, Li _{0.3+x} Cl _{0.6-y} Er _{0.1 -z}, Li _{0.3+x} Cl _{0.6-y} Y _{0.1 -z}, Li _{0.444+x} S _{0.444-y} Sn _{0.1 1 1 -z}, Li _{0.44+x} P _{0.08-y} S _{0.36-z} Cl _{0.12-w}, Li _{0.270+x} O _{0.515-y} Zr _{0.070-z} La _{0.128+w} W _{0.015-1}, Li _{0.265+x} O _{0.510-y} Al _{0.010-z} Zr _{0.085+w} La _{0.127+1}, Li _{0.291 +x} 0 _{0.5-y} Zr _{0.083-z} La _{0.125-w}, Li _{0.276+x} O _{0.510-y} Zr _{0.063+z} Nb _{0.021 -w} La _{0.127+1} and Li _{0.166+x} B _{0.166-y} O _{0.5-z} Al _{0.125+w} Cl _{0.041 +1}, or any material from this group with one or more elements replaced with an element of equal group number, wherein '_{#}’ and ‘_{# ± x, y, z, w, I, or m }’ represent non-stoichiometric weightings of an element immediately to the left of '_{#}’ or ‘_{# ± x, y, z, w, I, or m }’ in a chemical formula of the material, wherein # can be in the range of # ± n, wherein 0 < n < 0.5, wherein 0 < x, y, z, w, I, and m < #, and wherein # can be ±n, 0 < n < 0.5.

In some embodiments, the second solid state electrolyte 334 may selected from the group consisting of Li J0.307} Cl J0.076}, Li J0.400} B JO.OOO} O JO.OOO} Al J3.503} Si J0.133} S J0.465}, Li J0.461 } P JO.076} S J0.384} I J0.076}, Li {0.44} P _{0.08} S J0.36} Cl J0.108} Br J0.012}, Li {0.44} P _{0.08} S _{0.36} Cl JO.108} I JO.012}, Li {0.44} P _{0.08} S _{0.36} Cl J0.12}, Li J0.388} P J0.1 1 1 } S J0.444} I JO.055}, Li _{0.6+x} O J0.2+y} Br _{0.2-z} , Li _{0.6-x} O _{0.2-y} Cl _{0.2+z}, Li J0.3+x} Br _{0.6-y} In _{0.1 - z}, Li _{0.3+x} Br _{0.6-y} Y _{0.1 -z}, Li J0.3+x} Br _{0.6-y} Er J0.1 -z}, Li _{0.416+x} Si _{0.106+y} S J0.363- z} I _{0.1 13-w}, Li _{0.3+x} Sc _{0.1 -y} Br J0.6-Z}, Li J0.166+x} B _{0.166-y} O _{0.5-z} Al _{0.125+w} Cl J0.041 +1 }, Li _{0.375+x} O _{0.5-y} P J0.125-z}, Li _{0.485+x} P _{0.029-y} S _{0.367-z} Ge _{0.044+w} I JO.073-1 }, Li _{0.5+x} P J0.071 -y} S J0.428-Z}, Li J0.461 +x} P _{0.076-y} S _{0.384-z} I _{0.076-w}, Li _{0.433+x} S J0.452-y} As _{0.018-z} Sn _{0.094-w}, Li J0.481 +x} P _{0 ,074-y} S _{0.407-z} Cl _{0.037-w}, Li J0.461 +x} O _{0.076+y} P _{0.076-z} S _{0.307-w} Cl J0.076-1 }, Li _{0.475+x} Si _{0 ,026+y} P _{0.048-z} S J0.374-W} Br J0.074-1 }, Li J0.461 +x} P _{0.076-y} S _{0.384-z} Br _{0.076+w}, Li J0.461 +x} P JO.076- y} S _{0.384-z} Cl _{0.076-w}, Li _{0.44+x} P _{0.08-y} S _{0.36-z} Cl _{0.108-w} Br J0.012+1 }, Li _{0.44+x} P _{0.08-y} S _{0.36-z} Cl _{0.108-w} I JO.012+1 }, Li _{0.428+x} P _{0.142-y} S J0.428-Z}, Li _{0.423+x} Al J0.038+y} P _{0.076-z} S _{0.461 -w}, Li J0.4+X} Si J0.04+y} P _{0.08-z} S _{0.48-w}, Li J0.4+X} Si J0.04+y} P J0.08-Z} S J0.48-W}, Li _{0.44+x} F _{0.032-y} P _{0.08-z} S _{0.36-w} Cl J0.088-1 }, Li J0.4+x} P _{0.08-y} S _{0.48-z} Sn _{0.04+w}, Li J0.4+x} P _{0.08-y} S _{0.48-z} Sn _{0.04+w}, Li J0.385+X} Si J0.070+y} P _{0.058-z} S _{0.473-w} Cl J0.012-1 }, Li _{0.388+x} P _{0.1 1 1 +y} S _{0.444-z} I _{0.055+w}, Li _{0.385+x} Si J0.070+y} P _{0.052-z} S _{0.473-w} Cl J0.012-1 } Sb _{0.005-m}, Li _{0.310+x} P J0.152+y} S J0.537-Z}, Li _{0.375+x} P _{0.125+y} S _{0.5-z}, Li J0.308+X} P J0.153+y} S _{0.536-z} I _{0.001 -w}, Li _{0.333+x} P _{0.142+y} S J0.523-Z}, Li _{0.333+x} P _{0.142+y} S _{0.523-z}, Li _{0.333+x} P _{0.142+y} S _{0.523-z}, Li _{0.333+x} P J0.138+y} S _{0.509-z} Mn _{0.004-w} I _{0.014+I}, Li _{0.260+x} P _{0.173+y} S _{0.565-z}, Li J0.390+X} P J0.121 +y} S J0.487-Z}, Li _{0.337+x} P _{0.139+y} S _{0.522-z} Mo _{0.000+w}, Li _{0.390+x} P J0.097+y} S_{0.487-z} Sn _{0.024+w}, Li _{0.004+x} Li _{0.373+y} B {0.001 -z} P_{0.124+w} S JO.496-1 }, Li _{0.393+x} P _{0.090+y} S _{0.484-z} Ge _{0.030+w}, Li _{0.4+x} P _{0.08+y} S _{0.48-z} Ge _{0.04+w}, Li _{0.304+x} P _{0.043+y} S J0.521 -z} Ge _{0.130+w}, Li _{0.325-x} B _{0.181 +y} S _{0.377+z} I J0.1 15-w} and Li JO.081 +x} O _{0.648-y} Al _{0.027+z} P _{0.162-w} Ti JO.081 -1 }, or any material from this group with one or more elements replaced with an element of equal group number, wherein J#}’ and J# ± x, y, z, w, I, or m }’ represent non-stoichiometric weightings of an element immediately to the left of J#}’ or J# ± x, y, z, w, I, or m }’ in a chemical formula of the material, wherein # can be in the range of # ± n, wherein 0 < n < 0.5, wherein 0 < x, y, z, w, I, and m < #, and wherein # can be ±n, 0 < n < 0.5.

In some embodiments, the cathode 320 may be mixed with the solid state electrolyte 330 including a material J0.139} S JO.522} Mo J0.000}, Li J0.333} P J0.138} S J0.509} Mn J0.004} I J0.014}, Li J0.375} P J0.125} S _{0.5}, H J0.004} Li J0.373} B J0.001 } P J0.124} S J0.496}, Li J0.390} P J0.121 } S J0.487}, Li {0.385} Si JO.070} P J0.052} S J0.473} Cl J0.012} Sb J0.005}, Li J0.390} P J0.097} S J0.487} Sn JO.024}, Li {0.385} Si J0.070} P J0.058} S J0.473} Cl J0.012}, Li J0.393} P J0.090} S J0.484} Ge JO.030}, Li _{0.4} Si _{0.04} P _{0.08} S _{0.48} , Li _{0.4} Si _{0.04} P _{0.08} S _{0.48} , Li _{0.4} P _{0.08} S _{0.48} Ge JO.04}, Li J0.388} P J0.1 1 1 } S J0.444} I J0.055}, Li J0.400} B J0.000} O J0.000} Al J3.503} Si JO.133} S J0.465}, Li _{0.4} P _{0.08} S _{0.48} Sn J0.04}, Li _{0.4} P _{0.08} S _{0.48} Sn _{0.04}, Li {0.423} Al J0.038} P J0.076} S J0.461 }, Li J0.433} S J0.452} As J0.018} Sn J0.094}, Li J0.444} S J0.444} Sn J0.1 1 1 }, Li {0.44} P _{0.08} S _{0.36} CI J0.108} I J0.012}, Li J0.428} P J0.142} S JO.428}, Li {0.44} P _{0.08} S _{0.36} Cl _{0.12}, Li {0.44} F J0.032} P _{0.08} S _{0.36} Cl J0.088}, Li J0.44} P J0.08} S J0.36} CI J0.108} Br J0.012}, Li J0.461 } O J0.076} P J0.076} S J0.307} Cl J0.076}, Li JO.416} Si _{0.106} S J0.363} I J0.1 13}, Li _{0.6} O _{0.2} Cl _{0.2}, Li J0.461 } P J0.076} S J0.384} I JO.076}, Li JO.461 } P JO.076} S J0.384} Cl J0.076}, Li J0.461 } P J0.076} S J0.384} Br J0.076}, Li J0.481 } P J0.074} S J0.407} Cl J0.037}, Li J0.475} Si J0.026} P J0.048} S J0.374} Br J0.074}, Li J0.6} O _{0.2} Br _{ 0.2} , Li J0.485} P J0.029} S J0.367} Ge J0.044} I J0.073}, Li _{0.5} P J0.071 } S J0.428}, Li _{0.3+x} Cl _{0.6-y} Er _{0.1 -z}, Li _{0 ,3+x} Cl _{0.6-y} Y _{0.1 -z}, Li J0.081 +x} O _{0.648-y} Al _{0.027+z} P _{0.162-w} Ti J0.081 -I}, Li J0.3+x} Cl _{0.6-y} Sc J0.1 -z}, Li _{0.3+x} Br _{0.6-y} Er J0.1 -Z}, Li _{0.265+x} O _{0.510-y} Al _{0.010-z} Zr _{0.085+w} La J0.127+I}, Li J0.271 +X} O J0.508-y} Ga _{0.008-z} Zr {0.084+w} La JO.127+1}, Li _{0.276+x} OJO.510-y} Zr_{0.063+z} Nb_{0.021 -w} La_{0.127+1}, Li _{0.166+x} B _{0.166-y} 0 _{0.5-z} AI _{0.125+w} Cl J0.041 +I}, Li J0.291 +X} O _{0.5-y} Zr _{0.083-z} La _{0.125-w}, Li _{0.270+x} O JO.515-y} Zr J0.070-Z} La J0.128+W} W J0.015-I}, Li J0.400-X} B J0.000-y} O JO.OOO-z} Al J3.503+W} Si JO.133-1} S J0.465-m}, Li J0.3+x} Cl J0.6-y} In J0.1 -Z}, Li J0.3+x} Sc J0.1 -y} Br J0.6-Z}, Li J0.3+X} Br J0.6-y} Y J0.1 -z}, Li J0.3+x} Br J0.6-y} In J0.1 -z}, Li J0.325-X} B J0.181 +y} S J0.377+Z} I J0.115-W}, Li J0.260+X} P J0.173+y} S J0.565-Z}, Li J0.375+X} P J0.125+y} S J0.5-Z}, Li J0.304+X} P J0.043+y} S J0.521 -Z} Ge J0.130+W}, Li J0.310+x} P J0.152+y} S J0.537-Z}, Li J0.333+X} P J0.142+y} S J0.523-Z}, Li J0.333+X} P J0.142+y} S J0.523-Z}, Li J0.333+X} P J0.142+y} S J0.523-Z}, Li J0.375+X} O J0.5-y} P J0.125-Z}, Li J0.308+X} P J0.153+y} S J0.536-Z} I J0.001 -W}, Li J0.333+X} P J0.138+y} S J0.509-Z} Mn J0.004-W} I J0.014+I}, Li J0.337+X} P J0.139+y} S J0.522-Z} Mo JO.OOO+w}, Li J0.6-X} O J0.2-y} Cl J0.2+Z}, Li J0.388+X} P J0.1 1 1 +y} S J0.444-Z} I J0.055+W}, H J0.004+X} Li J0.373+y} B JO.001 -z} P J0.124+W} S J0.496-I}, Li J0.461 +x} O J0.076+y} P J0.076-Z} S J0.307-W} Cl J0.076-I}, Li J0.390+X} P J0.097+y} S J0.487-Z} Sn J0.024+W}, Li J0.393+X} P J0.090+y} S J0.484-Z} Ge J0.030+W}, Li J0.6+X} O J0.2+y} Br J0.2-z}, Li J0.390+X} P J0.121 +y} S J0.487-Z}, Li J0.4+x} P J0.08+y} S J0.48- z} Ge J0.04+W}, Li J0.385+X} Si J0.070+y} P J0.052-Z} S J0.473-W} Cl J0.012-I} Sb J0.005-m}, Li J0.385+X} Si J0.070+y} P J0.058-Z} S J0.473-W} Cl J0.012-I}, Li J0.416+X} Si J0.106+y} S J0.363-Z} I J0.1 13-W}, Li J0.461 +X} P J0.076-y} S J0.384-Z} Br J0.076+W}, Li J0.4+x} Si J0.04+y} P J0.08-Z} S J0.48-W}, Li J0.4+X} Si J0.04+y} P J0.08-Z} S J0.48-W}, Li J0.4+x} P J0.08-y} S J0.48-Z} Sn J0.04+W}, Li J0.4+X} P J0.08-y} S J0.48-Z} Sn J0.04+W}, Li J0.428+X} P J0.142-y} S J0.428-Z}, Li J0.423+X} Al J0.038+y} P J0.076-Z} S J0.461 -W}, Li J0.444+X} S J0.444-y} Sn J0.1 1 1 -z}, Li J0.433+X} S J0.452-y} As J0.018-z} Sn J0.094-W}, Li J0.485+X} P J0.029-y} S J0.367-Z} Ge J0.044+W} I J0.073-I}, Li J0.44+X} P J0.08-y} S J0.36-Z} Cl J0.108-W} I J0.012+I}, Li J0.44+X} P J0.08-y} S J0.36-Z} Cl J0.108-W} Br one or more elements replaced with an element of equal group number, wherein '_{#}’ and ‘_{# ± x, y, z, w, I, or m }’ represent non-stoichiometric weightings of an element immediately to the left of '_{#}’ or ‘_{# ± x, y, z, w, I, or m }’ in a chemical formula of the material, where # can be in the range of # ± n, where 0 < n < 0.5, where 0 < x, y, z, w, I, and m < #, and where # can be ±n, 0 < n < 0.5.

In some embodiments, the cathode 320 may be mixed with the solid state electrolyte 330 including a material _{0.04}, or any material from this group with one or more elements replaced with an element of equal group number, wherein '_{#}’ and ‘_{# ± x, y, z, w, I, or m }’ represent non-stoichiometric weightings of an element immediately to the left of '_{#}’ or ‘_{# ± x, y, z, w, I, or m }’ in a chemical formula of the material, where # can be in the range of # ± n, where 0 < n < 0.5, where 0 < x, y, z, w, I, and m < #, and where # can be ±n, 0 < n < 0.5.

In some embodiments, the cathode 320 may be mixed with the solid state electrolyte 330 including a material selected from Li _{0.4+x} P _{0.08+y} S _{0.48-z} Ge _{0.04+w}, Li _{0.385+x} Si _{0.070+y} P _{0.052-z} S _{0.473-w} Cl J0.012-I} Sb _{0.005-m}, Li _{0.385+x} Si _{0.070+y} P _{0.058-z} S _{0.473-w} Cl J0.012-I}, Li _{0.416+x} Si _{0.106+y} S J0.363-Z} l _{0.1 13-w}, Li J0.461 +x} P _{0.076-y} S _{0.384-z} Br _{0.076+w}, Li _{0.4+x} Si _{0.04+y} P _{0.08-z} S _{0.48-w}, Li _{0.4+x} Si _{0.04+y} P _{0 ,08-z} S _{0.48-w}, Li _{0.4+x} P _{0.08-y} S _{0.48-z} Sn _{0.04+w}, Li _{0.4+x} P _{0.08-y} S _{0.48-z} Sn _{0.04+w}, or any material from this group with one or more elements replaced with an element of equal group number, wherein '_{#}’ and ± x, y, z, w, I, or m }’ represent non-stoichiometric weightings of an element immediately to the left of '_{#}’ or ‘_{# ± x, y, z, w, I, or m }’ in a chemical formula of the material, where # can be in the range of # ± n, where 0 < n < 0.5, where 0 < x, y, z, w, I, and m < #, and where # can be ±n, 0 < n < 0.5.

In some embodiments, a solid state electrolyte 330 can be mixed with the cathode 320 and/or may have a core-shell particle structure.

FIG. 4 is a cross-sectional illustration of an electrochemical cell 400 including an anode 440 disposed on an anode current collector 450, a cathode 420 disposed on a cathode current collector 410, and a solid state electrolyte 430 disposed between the cathode 420 and the anode 440, according to an embodiment. In some embodiments, the solid state electrolyte 430 may include solid state electrolyte (SSE) multilayers (e.g., as described with respect to the solid state electrolyte 330). In some embodiments, the solid state electrolyte 430 may have a first side and a second side opposite the first side. In some embodiments, the first side of the solid state electrolyte 430 may be coated with a first coating 422 (e.g., protection materials) and/or the second side of the solid state electrolyte 430 may be coated with a second coating 446. In some embodiments, the first coating 422 may be disposed between the cathode 420 and the solid state electrolyte 430, and/or the second coating 446 may be disposed between the anode 440 and the solid state electrolyte 430. In some embodiments, the electrochemical cell 400 may further include a third coating 448 disposed between the anode 440 and the anode current collector 450.

In some embodiments, the electrochemical cell 400 can be the same or substantially similar to the electrochemical cell 100, 200, 300 as described above with reference to FIG. 1 , 2 or 3. In some embodiments, the anode 440 including an anode material and disposed on the anode current collector 450, the cathode 420 disposed on the cathode current collector 410, and the solid state electrolyte 430 disposed between the cathode 420 and the anode 440 may be the same or substantially similar to the anode 140, 240, 340, the anode current collector 150, 250, 350, the cathode 120, 220, 320, the cathode current collector 1 10, 210, 310, and the solid state electrolyte 130, 230, 330, respectively, described with respect to FIG. 1 , FIG. 2 or FIG. 3. In some embodiments, the electrochemical cell 400 can be under a mechanical constriction (P) as described above with respect to FIG. 1 .

In some embodiments, the coatings 422 and/or 446 can act as an interfacial layer between the base electrode material and the solid state electrolyte 430. In particular, the coatings 422 and 446 can be configured to improve the interface stability between the electrode, e.g., the cathode 420, and the solid electrolyte 430 for superior cycling performance. For example, the coating 422 or the cathode 420 may include, but is not limited LiNbOs, LiTaOs Li2ZrOs, LiNbxTai-xOs (0<x<1 ), yLi2ZrO3-(1 -y)LiNbxTai-xO3 (0<x, y<1 ), AI2O3, TiO2, ZrO2, AIF3, MgF2, SiO₂, ZnS, ZnO, Li4SiO4 IJ3PO4. LisInCle, Lii+xAlxTi2-x(PO4)3(0<x<2), LiMn2O4, LilnO2-Lil, LiePSsCI, IJAIO2, and carbon. In some embodiments, the coating 422 includes LiNbOs.

In some embodiments, the solid state electrolyte 430 may be separated from the anode material and/or the cathode material by the coating 446 and 422, respectively, including Li4TisOi 2, IJ3V2O5, silicon dioxide, carbon (e.g., amorphous carbon, carbon nanotube, graphene, carbon nanofiber, fullerene (e.g., Ceo), hard carbon, or graphite, e.g., as a graphite coating on the electrodes), Au, Ag, Sn, SnO2 or a combination thereof.

In some embodiments, the coatings 422, 446, and/or 448 may include particles. In some embodiments, the particle size of the coatings can be from about 1 nm to about 100 pm, e.g., about 1 -100 nm (e.g., about 1 -10 nm, 1 -25 nm, 10-20 nm, 20-30 nm, 25-50 nm, 30-40 nm, 40-50 nm, 50-60 nm, 50-75 nm, 60-70 nm, 70-80 nm, 75-100 nm, 80-90 nm, or 90-100 nm, e.g., about 1 nm, 5 nm, 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, or 100 nm), e.g., about 100-1 ,000 nm (e.g., about 100-1 10 nm, 100-125 nm, 100- 200 nm, 200-300 nm, 250-500 nm, 300-400 nm, 400-500 nm, 500-600 nm, 500-750 nm, 600-700 nm, 700- 800 nm, 750-1 ,000 nm, 800-900 nm, or 900-1 ,000 nm, e.g., about 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, or 1 ,000 nm), e.g., about 1 -10 pm (e.g., about 1 -2 pm, 1 -5 nm, 2-3 pm, 3- 4 pm, 4-5 pm, 5-10 pm, 5-6 pm, 6-7 pm, 7-8 pm, 8-9 pm, or 9-10 pm, e.g., about 1 pm, 2 pm, 3 pm, 4 pm, 5 pm, 6 pm, 7 pm, 8 pm, 9 pm, or 10 pm), or, e.g., about 10-100 pm (e.g., about 10-20 pm, 10-25 pm, 10-50 pm, 20-30 pm, 25-50 pm, 30-40 pm, 40-50 pm, 50-60 pm, 50-75 pm, 60-70 pm, 75-100 pm, 70-80 pm, 80-90 pm, or 90-100 pm, e.g., about 10 pm, 12 pm, 13 pm, 14 pm, 15 pm, 16 pm, 17 pm, 18 pm, 19 pm, 20 pm, 21 pm, 22 pm, 23 pm, 24 pm, 25 pm, 26 pm, 27 pm, 28 pm, 29 pm, 30 pm, 40 pm, 50 pm, 60 pm, 70 pm, 80 pm, 90 pm, or 100 pm). In some embodiments, the coatings 422, 446, and/or 448 may include indium. In some embodiments, the coatings 422, 446, and/or 448 may include polyethylene oxide, polyvinylidene fluoride, poly(vinylidene fluoride- co-hexafluoropropylene), poly(ethyl methacrylate), or poly(vinylidene fluoride-co-trifluoroethylene).

In some embodiments, the coatings 422, 446, and/or 448 (e.g., a protection layer) can be mixed with the Li metal and/or polymer with a thickness of about from 0 pm to about 500 pm, inclusive. In some embodiments, the lithium metal layer can be protected by a layer formed by one or more elements of Na, Mg, Al, Si, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Zn, Ga, Ge, As, Rb, Sr, Y, Zr, Nb, Mo, Ag, Cd, In, Sn, Sb, Bi, Cs, or Te. In some embodiments, the lithium metal layer can be alloyed with one or more elements of Na, Mg, Al, Si, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Zn, Ga, Ge, As, Rb, Sr, Y, Zr, Nb, Mo, Ag, Cd, In, Sn, Sb, Bi, Cs, or Te. In some embodiments, the lithium metal layer can be protected by the compound of H, Li, B, C, N, O, F, Na, Mg, Al, Si, P, S, Cl, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Zn, Ga, Ge, As, Se, Br, Rb, Sr, Y, Zr, Nb, Mo, Ag, Cd, In, Sn, Sb, Te, I, Cs, Ba, Pt, Au, Hg, TI, Pb, Bi Po, At, La, Ce, Pr, Nd, Pm, Sum, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, or Lu. In some embodiments, the third coating 448 may include a lithium layer disposed on the anode current collector 450, that may configured to provide additional lithium metal for lithiation in the anode 440.

FIG. 5 is a schematic flow chart of a method 10 for manufacturing an electrochemical cell including a cathode, an anode, and a solid state electrolyte disposed between the cathode and the anode, according to an embodiment. While described with respect to the electrochemical cell 100 and the components included therein, the method 10 is equally applicable to any electrochemical cell including any of the implementations described herein. All such embodiments are envisioned and should be considered to be within the scope of the present disclosure.

The method 10 includes disposing the cathode 1 10 on the cathode current collector 1 10, at step 12. In some embodiments, the cathode material included in the cathode 1 10 includes lithium. The method 10 may optionally include, at step 14, disposing a first coating on the cathode 1 10. In some embodiments, the coating may be the same or substantially similar to the coating 422 described with respect to FIG. 4. The method 10 further includes disposing the anode 140 on the anode current collector 150, at step 16. In some embodiments, the anode material forming the anode 140 includes a plurality of voids defined therein. The voids, in some embodiments, can be the same or substantially similar to the voids 244 described with respect to FIG. 2. The method 10 may optionally include, at step 18, disposing a second coating (e.g., similar to the coating 446 described above) on the anode 140. In some embodiments, the method 10 includes disposing the solid-state electrolyte 130 between the cathode 1 10 and the anode 140 to form the electrochemical cell 100. In some embodiments, the electrochemical cell formed may be same or substantially similar to the electrochemical cells 100, 200, 300 or 400 described above with respect to FIGS. 1 -4. In some embodiments, the method 10 may further include compressing the electrochemical cell 100 at a predetermined pressure, at step 24. The pressure may cause a mechanical constriction on the electrochemical cell same or substantially similar to the mechanical constriction described above with respect to FIGS. 1 and 2. The method 10 may further include charging the electrochemical cell 100, at step 26. In some embodiments, the charging can cause Li metal to be deposited in the voids of the anode 140. The method 10 may further includes discharging the electrochemical cell 100, at step 28. In some embodiments, discharging can cause Li metal deposited in the voids to be oxidized. In some embodiments, a methods of storing (e.g., step 26) and releasing (e.g., step 24) electrical energy includes using electrical energy to charge a solid state electrochemical cell or battery, described herein according to some embodiments, by applying a voltage across the battery that causes Li to migrate as Li⁺ ions from a cathode to an anode, where the Li deposited (e.g., plated) in the voids as Li metal, thereby storing the electrical energy as chemical energy. In discharge, the Li metal is oxidized to Li⁺ and migrates back to the cathode.

To release (discharge) the stored chemical energy as electrical energy, a load is electrically connected between the anode and cathode in a circuit to allow the Li⁺ ions to migrate from the anode via the solid state electrolyte to the cathode. In some embodiments, a bulk (e.g., a material below about 500 nm (e.g., below 400 nm, 300 nm, 200 nm, 100 nm, or 65 nm) from the surface) does not accept Li (e.g., does not undergo lithiation).

Methods described herein may involve repeating the above cycle multiple times, e.g., greater than 1 ,000 times, e.g., 1000-20,000 times (e.g., 1 ,000-1 ,500 times, 1 ,250-1 ,750 times, 1 ,500-2,000 times, 1 ,500-2,500 times, 2,000-3,000 times, 2,500-5,000 times, 5,000-10,000 times, 5,000-15,000 times, 10,000-20,000 times, or 15,000-20,000 times).

The methods of storing and releasing electrical energy may include first allowing a portion of the Li⁺ ions to react to form a surface layer on the anode material, e.g., in an initial charge-discharge cycle. Alternatively, the anode material may already have a surface layer.

Methods described herein may include actively applying external pressure during cycling (e.g., with a press). In some embodiments, at least 10% (e.g., at least 15%, 20%, 25%, 30%, 40%, 50%, 60%, 70%, 75%, 80%, 85%, or 90%, e.g., about 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 91 %, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99%, e.g., 10-15%, 10-20%, 15-30%, 25-50%, 40-60%, 50-75%, 65-80%, 75-99%, 70- 90%, 80-90%, 90-95%, 93-97%, or 95-99.99%, e.g., greater than 99%, e.g., 99.01 %-99.99%) of the stored electrical energy is stored as lithium metal (e.g., in the voids). That is, at least 10% of the stored electrical energy is not stored as lithiated anode material, i.e., is stored as plated lithium in the voids.

EXAMPLES

Methods - The below methods apply to Examples 1-5

Materials and Batteries

Li5.5PS4.5CI1.5 (LPSCI) was prepared by high energy ball milling and a subsequent annealing process. Stoichiometric amounts of U2S (99.9% purity, Alfa Aesar), P2S5 (99% purity, Sigma Aldrich) and LiCI (99% purity, Alfa Aesar) were milled for 16 h in a planetary mill PM200 (Retsch GmbH, Germany) under a protective Ar atmosphere followed by sintering at 550 °C in a quartz tube.

A 0.63-cm-diameter Li foil with a thickness of 25 pm was covered by a 0.79-cm-diameter silicon-graphite composite film (SiG) with a weight ratio of silicon (1 -pm-sized, Skyspring Nanomaterials, Inc.), graphite (BTR, China) and PTFE as 47.6%:47.6%:4.8%. The cathode layer was made by mixing 30 wt% solid electrolyte, 70 wt% single-crystal LiNbOs coated LiNi0.83Mn0.1Co0.07O2 (1-5-pm particle size, MSE Supplies) and an additional 3 wt% PTFE with an active material loading of 10-60 mg/cm². For the single layer design, 120 mg LPSCI1.0 or LPSCI1.5 was employed as the electrolyte; for the multilayer design, 20 mg LPSCI1.5 and 100 mg LGPS (or LSnPS) were used. The full battery, with a structure of Li-SiG- LPSCI1.5-LGPS-LPSCI1.5-NMC83, was pressed together in a homemade pressurized cell at 400 MPa and kept at 50 MPa during testing. Nominal NP ratio was controlled at 0.3-1 .5 and was calculated based the theoretical capacity of Si (3,000 mAh/g) and NMC83 (200mAh/g). All batteries were assembled in an argon atmosphere glovebox, and the humidity of the battery testing environment was controlled inside a Memmert hpp1 10. Battery testing was conducted using an Arbin instrument at 0 °C, 35 °C, or 55 °C. The cutting-off voltages are set between 2.5 V-4.1 V and 2.0 V-4.35 V for high-rate cycling. The liquid electrolyte cells were made using Li or SiG as the anode and 1 M LiPFe in EC/DMC (v:v = 1 :1 ) as the electrolyte.

An anode protection layer and three solid electrolyte layers were cast sequentially onto the (5 pm) lithium coated copper foil. To prepare a slurry for the anode protection layer, 50 wt% silicon powder (1 pm), 50 wt% graphite powder, and an additional 2.5 wt% acrylate-based polymer binder were mixed with anhydrous p- xylene and isobutyl isobutyrate (1 :1 vol/vol) using a planetary centrifugal mixer (Thinky Corporation). Milling balls were added into the mixture to obtain a homogenous slurry, which then was cast using a doctor blade and dried at room temperature. The next one, two, or three solid electrolyte layers were composed of LiePSsCI , Li SnP2Si2, LiePSsCI, respectively, and their slurries were prepared in a similar manner, with additional solvents to adjust the viscosity. The polymer binder amount varied from 0.5% to 5 wt%. Each new layer was cast onto the previous layer after the latter was dried for approximately 2 minutes at room temperature. After coating the fourth layer, the film was then transferred to a dynamic vacuum oven to dry thoroughly at 60 °C for 12 hours. Dried multi-layer film was cut using a pneumatic punch machine into a specific size of 35 mm by 28 mm for pouch cell fabrication. The same casting method with one, two, or more solid electrolytes was used to cast onto cathodes or a Polyester (PET) films. In some experiments, after the electrolytes were cast onto PET, the electrolyte layers were transferred to the cathode or anode by applying calendar pressure or isostatic pressure. The pouch cell batteries were composed of an anode, a cathode and a multi-layer film. These sheets were stacked and packed into a laminate bag. The cells were densified at 350 MPa and 70 °C with a press.

XPS

XPS was conducted with a Thermo Scientific K-Alpha⁺ with the spot size of 400 pm. A vacuum transfer module was used to transfer samples from the glovebox to the XPS chamber. The samples were not exposed to air during the XPS sample transfer or measurement. An argon ion milling was applied with the energy of 0.5keV and the current of ~0.6 pA for 500-1 ,000 seconds.

FIB-SEMS

FEI Helios 660 was used for the cross-section focused ion beam scanning electron microscopy (FIB-SEM) imaging. The pristine material and cycled pellets were transferred from an argon-f il led glovebox using a sealed plastic bag. The sample is exposed to air for 1 -2 minutes during transfer. Pt pre-deposition and Ga⁺ milling procedures were conducted to create a cleaned cross-section region at different currents. SEM-EDX imaging was conducted using the inner EDAX tools and detector of the instrument. The batteries for FIB-SEM imaging were tested at room temperature. EELS

The lithiated layer of the anode material was milled by FIB to reach a desirable thickness for electron energy loss spectroscopy (EELS). The thickness, as confirmed by both FIB-SEM and TEM, is 65 nm. In TEM, the thickness is calculated based on the convergence angle = 30 mrad, collection angle = 43 mrad, and ln(lt/lo) = -0.54, where /_f and Io are the total spectrum integral and the zero-loss integral, respectively. Such a thickness can provide a sufficient signal for the detection of Li. (Scanning-)TEM, HRTEM, and EELS are conducted on ARM 200 with the voltage of 200 kV.

Example 1 - Initial Investigations

FIG. 6(a) shows the specific capacity at room temperature of a solid state asymmetric battery with a configuration of Li/graphite(G)-solid electrolytes (Ses)-SiG, where SiG is the composite layer formed by micron-sized Si and graphite particles. The discharge capacity, i.e. , moving Li⁺ from Li/G to SiG, is over 5,600 mAh/g if calculated based on the mass loading of Si, which is much higher than its theoretical capacity of 3,000 mAh/g. At around 5,000 mAh/g discharge, there was a signal of short circuit, indicating the lithium penetration. The discharge curve shows a quick dip when Li was depleted in the Li/G side at the end of discharge. At three different discharged states, focused ion beam-scanning electron microscopy (FIB-SEM) images and energy dispersive spectrum (EDS) mapping were taken (FIG. 6(b1 )) to reveal the anode morphology and chemistry. Before discharge, pristine anode shows pores between Si particles (FIG. 6(b1 )). Upon discharge toward 0 V, the Si particle shows no cracks nor any obvious Si swelling (FIGS. 6(b2) and 6(b3)). A notable lithium deposition was already observed between Si particles at -0.2 V (FIG. 6(b3)), where the existence of lithium metal was identified by its morphology and the oxygen signal (FIG. 6(c1 )- 6(c3)), as Li metal is the most reactive component in the composite to oxygen and nitrogen in the atmosphere. To further confirm that the oxygen EDS signal is mainly contributed by lithium metal, the cross-sections of pristine SiG composites with and without a lithium metal anode foil being directly added beneath the SiG layer are displayed in FIGS. 10(a1 )- 10(c2) for a comparison, where major oxygen and nitrogen signals are only from the added lithium metal foil. Also considering that most capacity is below 0 V at such a very low discharge current density of 0.2 mA/cm² with little polarization, the above results suggest that there might be significant lithium plating at SiG, and the composite served as a lithium metal anode instead of silicon anode.

In contrast to the surprising behavior in the above solid state batteries, in the liquid electrolyte battery, Si micrometer (pm)-particles exhibit normal plateaus at 0.5 V and 0.3V (V.S. Li/Li⁺), corresponding to two lithium alloy reactions (FIG. 6(d)) with a total capacity around 1 ,800 mAh/g. SEM further shows completely different morphology from Si pulverization that is common in liquid electrolyte batteries for a Si anode (FIG. 6(e1 )- 6(e2)). Furthermore, when LiNi0.83Mn0.06Co0.11O2 (NMC83) cathode is paired with SiG anode in a liquid electrolyte battery, pulverization of Si particles can again be observed only after 5 cycles (FIGS. 1 1 (a) and 1 1 (b)), indicating the damage caused by the volumetric swelling of the lithiation. This phenomenon is accompanied by the poor cycling performance (FIG. 1 1 (c)), where only 30% capacity was left after 5 cycles. Different from the Si particles in the liquid electrolyte battery, they stay in an intact state in solid state batteries. The solid state full battery was made with SiG covering a thin layer of Li metal (25 pm) as anode and NMC83 at 25mg/cm² loading as cathode with a nominal negative to positive (NP) ratio of 1 .5, hypothetically calculated based on the Si (3000 mAh/g) and NMC83 (200 mAh/g) capacities. The lithium metal layer under the SiG composite layer provides extra lithium source, which improves the battery cycling performance, and the multilayer electrolyte configuration provides the cycling stability against Li dendrite. No cracks, pulverization, or irregular edges were found in the FIB-SEM images of Si particles after 500 cycles (FIGS. 1 1 (d)-1 1 (f)). Without pulverization being observed in solid state batteries (FIG. 6(b) and FIGS. 1 1 (d)-1 1 (f)), lithiation of Si may be largely limited and the capacity can be mainly provided by lithium metal plating and stripping. To test this hypothesis, the lithium distribution in the anode was observed more directly as described herein.

Example 2 - Spectroscopic Analysis of Anodes

Although Li, as a light element, cannot be detected by EDS, electron energy loss spectroscopy (EELS) and X- ray photoelectron spectroscopy (XPS) can capture it. First, EELS line scan was combined with EDS mapping in a scanning transmission electron microscope (STEM) to unveil the lithium distribution in the SiG composite anode (FIGS. 7(a)-7(c)). FIG. 7(a) shows the dark field STEM image of a SiG anode from a full battery after 500 cycles and stopped at a charged state of 4.1 V (FIG. 1 1 (f)). The SiG anode part was milled to 65 nm depth by FIB. Scanning from outer region to the bulk of the Si particle (FIG. 7(a)), the Li-K edge in EELS (FIG. 7(b)) shows that only the region outside the Si particle shows the existence of Li. The absence of Li inside the Si particle indicates that major part of Si was not lithiated in the battery cycling. Thus, even if the Li-Si alloying occurs, it should be limited to a skin surface layer less than 65 nm thickness as indicated by the region with coexisting Si-L and Li-K EELS signals in FIG. 7(b).

STEM-EDS mapping was conducted on the same sample (FIG. 7€), where the oxygen and nitrogen signals show consistent distribution as the Li element from EELS, all outside Si particles. The high-resolution TEM image (FIGS. 7(d1 )- 7(d2)) shows the lattice fringe of (1 1 1 ) plane with a measured dspacing of 3.1 A, agreeing well with the pristine Si crystalline phase (Kim, FL, Seo, M., Park, M. H. & Cho, J. A critical size of silicon nanoanodes for lithium rechargeable batteries. Angew. Chemie - Int. Ed. 49, 2146-2149 (2010)). Furthermore, the micron-scale Si particles maintain an intact morphology with no cracks, either after cycling at the charged state (FIG. 7(c), STEM) or at discharge (see, FIG. 7(c) and FIGS. 12(a)-12(f), SEM). They also show the well- separated distribution of EDS signals from oxygen (representing Li), carbon (from graphite), and Si from these full batteries (FIGS. 7(c), 7(e2)-7(e3), and FIGS. 12(c)-12(f)), consistent with the asymmetric battery result (see FIG. 6(c1 )- 6(c3)). These results further support the finding of lithium plating on the surface of Si, rather than the lithiation of Si, as the main source of electrochemical capacity in the various configurations of solid state batteries tested. It is thus actually a lithium metal anode rather than a silicon anode. It should be noted that since no lithium is beneath the SiG layer in the initial assembly of batteries in FIGS. 6(a)-6(e2), FIGS. 7(e1 )- 7(e3) and FIGS. 12(a)-12(f), all the observed lithium metal is plated from the other electrode side (either Li/G or NMC83). Especially at the nominal NP ratio of 1 .5 calculated based on the Si and NMC capacities, the Si-Li alloying capacity in principle is sufficient to accommodate all lithium from the cathode, rather than the surprising result observed here with little Si capacity.

XPS further shows the signal of lithium metal from the SiG anode side after the 1 ^st charge of an NMC-SES- SiG solid state battery (FIG. 13(a)). Since no Li layer was assembled on the anode side initially, this further confirms the plating of Li metal from charging the cathode. XRD was taken for the same anode, clearly showing the pristine Si phase rather than the lithiated alloying phase (FIG. 9(b)). FIG. 7(f) shows the XPS measurement around the Si peak energy after all lithium was stripped from the Li anode and plated to the SiG side in a Li- Ses-SiG solid state battery with a discharge capacity of over 5,000 mAh/g. It appears that Li-Si-0 does exist on the Si surface. However, after milling by argon ions for 500s at low energy (0.5 keV and 0.6 pA, etch rate ~ 0.52 A/s for SiC>2)( Chang, H. Y. et al. X-ray Photoelectron Spectroscopy Equipped with Gas Cluster Ion Beams for Evaluation of the Sputtering Behavior of Various Nanomaterials. ACS Appl. Nano Mater. 5, 4260- 4268 (2022); Kyoung, Y. K. et al. Electronic structures of SiO2 thin films via Ar gas cluster ion beam sputtering. Surf. Interface Anal. 46, 58-61 (2014)), the signal of Li-Si-0 reduces and Si, Li-Si, and Si-0 signals emerge. After 1 ,500s milling, the Li-Si-0 and Li-Si signals disappear with only Si and Si-0 peaks remaining. This indicates that only a skin surface of Si particles of less than 60 nm thickness is present, while the inner part is still pristine Si phase, consistent with our STEM-EELS and XRD results.

In addition, it was observed that compared with the nominal NP ratio of 1 .5 (FIGS. 9(c) and 13(d)), at a reduced nominal NP ratio of 0.3, lithium is more obviously observed to deposit underneath the entire SiG layer (FIGS. 13(e) and 13(f)). This is because the porosity region between Si particles in the SiG anode layer at NP = 0.3 is not large enough for lithium deposition. The lithium plating is also observed on the pure Si anode without graphite, although Si should in principle have enough capacity to be lithiated through alloying (FIGS. 14(a)- 14(g)). Therefore, it was confirmed that the solid state batteries described herein convert the behavior of silicon from what is expected for a silicon anode into that of a lithium metal anode, where the Si only serve as a scaffold to host Li metal plating and stripping in the voids between the Si particles as the main capacity source, instead of lithiating Si through conventional alloying and pulverization.

Example 3 - Battery Performance

Since lithium plating and stripping dominate the anode capacity here, Li dendrites could be an issue, especially at high current densities. In addition to the multilayer electrolyte design to prevent the Li dendrite penetration through dynamic stability (Ye, L. & Li, X. A dynamic stability design strategy for lithium metal solid state batteries. Nature 593, 218-222 (2021 )), the dynamic stability in computation (Wang, Y., Ye, L., Chen, X. & Li, X. A Two-Parameter Space to Tune Solid Electrolytes for Lithium Dendrite Constriction. J. Am. Chem. Soc. 2, 886-897 (2022); Fitzhugh, W., Chen, X., Wang, Y., Ye, L. & Li, X. Solid-electrolyte-interphase design in constrained ensemble for solid state batteries. Energy Environ. Sci. 14, 4574-4583 (2021 )) was further quantified and designed to facilitate the selection, design, and synthesis of advanced electrolyte materials in experiment. These efforts led to a stable cycling at high current density of 8.6 ~ 43 mA/cm², corresponding to an extremely high rate of 20 C ~ 80 C, all at a low cathode loading of 2 mg/cm². There was thus an important question regarding whether the high C-rate at low cathode loading for a given high current density can be exchanged for a reduced C-rate (but still high enough for fast charging, e.g., 2 C ~ 10 C) at commercially relevant cathode loadings (> 15 mg/cm²).

FIG. 8(a) shows the cycling performance of the Li metal anode solid state batteries described herein with a configuration of Li-Sig-SEs-NMC83 at a cathode loading of 25 mg/cm², where a well-designed multilayer electrolyte configuration combined with the anodes of Li-SiG according to the embodiments described herein shows an 80% capacity retention after either 1 ,000 or 2,000 cycles at a high current density of 7.4 mA/cm² or 2 C-rate. In comparison, the single electrolyte layer configurations at the same total thickness of electrolyte layer show much worse cycling of less than 500 cycles at the same cathode loading and rate. FIG. 8(b) further shows that multilayer design can show much higher capacity than the single layer one at 1 C to 2 C-rate, giving an area capacity around 2-3 mAh/cm² with good cycling performance (see, FIGS. 8(a), 8(b)). Since here Si functions as a 3D scaffold for lithium metal anode rather than a typical silicon anode, it is understandable that the particle size of Si (from 1 to 44 pm) has limited influence on the capacity of the full battery (FIG. 8(c)). Furthermore, the battery shows a high robustness even when the loading is increased to 60 mg/cm² with high area capacity up to 7 mAh/cm² (see, FIG. 8(d)).

Fast charging in alkaline metal-based batteries will rely on two preconditions, one is fast electrochemical kinetics and second is the prevention of lithium dendrite formation. The Li-Si alloying reaction is relatively slow, which usually comes with the pulverization of Si, making fast charging difficult for a conventional Si based battery. Here, however, lithium metal plating dominates the electrochemical process at the anode in the solid state batteries described herein according to multiple embodiments. The mechanism thus not only circumvents problems caused by the swelling of Si, but also provides a faster reaction pathway for fast cycling, since Li stripping and plating is faster than Li-Si alloying. Given that the lithium stripping and plating are faster than Li- Si alloying, and the ability of the multilayer solid electrolytes described herein in inhibiting dendrite formation, fast charging can be demonstrated. FIG. 9(a) shows the fast-charging capability of SiG composite anode with high loading of NMC83 as the cathode. It can deliver over 157 mAh/g at 5C fast charge and 1 C normal discharge. The fast 6C charge and discharge also show a capacity over 1 10 mAh/g. The discharge capacity of the solid state battery at 0 °C is 154 mAh/g (FIG. 9(b)).

In FIG. 15(a), the comparison of rate capabilities for different anodes is presented, where 50 wt% Si-50 wt% G shows the highest low-rate capacity while pure Si seems to show a slight advantage at high rate. However, the SiG composite shows a better cycling performance (80% capacity retention after 1 ,500 cycles in FIG. 9(c)) than pure Si (80% after 1000 cycles, see FIG. 15(b)), both at a commercial-level loading of 22 mg/cm² with high area capacity delivered from 1 -2.3 mAh/cm² and 6C-6C fast charge and discharge. The battery with Li- SiG anode further shows a 75% retention after over 2,000 cycles at 6C charge and 6C discharge, and 75% retention after 1 ,200 cycles at 10C charge and 2C discharge (FIG. 9(d)). The charge and discharge profiles are shown in FIG. 15(c) and 15(d). The current densities for 6 C and 10 C here are extremely high at 19.5 and 32.7 mA/cm², respectively. Note that at lowered temperatures of 35 °C, the electrochemical cells described herein can also cycle well at fast rates (see, FIG. (9e)).

Example 4 - Effect of Pressure

In order to investigate the role of mechanical constriction in the effects discovered herein, Si anode properties under different levels of mechanical constriction were computed. FIG. 9(f) shows the dependence of voltage and capacity for Si anode under different levels of mechanical constriction (K_etf) from 0 to 5 GPa, predicted by our constrained ensemble thermodynamic calculations (Fitzhugh et al., Energy Environ. Sci. 14, 4574-4583 (2021 ), Fitzhugh, W., Ye, L. & Li, X. The effects of mechanical constriction on the operation of sulfide based solid state batteries. J. Mater. Chem. A 7, 23604-23627 (2019), and Wu, F., Fitzhugh, W., Ye, L., Ning, J. & Li, X. Advanced sulfide solid electrolyte by core-shell structural design. Nat. Common. 9, 1-1 1 (2018)), (Wang, Y., Ye, L., Chen, X. & Li, X. A Two-Parameter Space to Tune Solid Electrolytes for Lithium Dendrite Constriction. J. Am. Chem. Soc. 2, 886-897 (2022)). In short, Si undergoes a volumetric swelling when alloyed with lithium under zero or low mechanical constrictions, while the strain energy associated with the swelling can resist the alloying reaction at high mechanical constrictions. The simulated capacity of Si at K_etf = 5 GPa is already as small as 164 mAh/g above 0 V, very close to the measured capacity above 0 V in FIG. 6(a). Note that here the 5 GPa is not the external pressure. This means that the Li-Si alloying reaction and associated pulverization at the surface of Si particle will experience a local effective modulus larger than 5 GPa. As a result of this high local effective modulus, lithium plating is preferred and can also appear in the SiG anode working at low external pressures of 5 MPa for a solid state battery (see, FIGS. 16(a)-(c)). These results all together suggest broad application of the understanding to the future design of both solid and liquid electrolyte batteries with superior rate performance, where constricting Si and other more proper materials for Li metal anode application can happen at various scales upon an advanced design.

Example 5 - Solid state pouch cells

FIG. 17 shows the cycling performance of the pouch cell with Si-G anode protection layer on Li metal. The electrolytes were made using a slurry casting method. Solid electrolytes were mixed with solvents and binders to prepare a slurry, where the anhydrous p-xylene and isobutyl isobutyrate (1 :1 vol/vol) was used as solvent and an arylate type polymer was used as binder. The solid state electrolytes were LiePSsCI, Li SnP2Si2, LiePSsCI. The solid state pouch cell was cycled at a high rate of 5C, the initial capacity was around 125 mAh/g and the capacity retention was around 90% after 2000 cycles.

Example 6 - Computational investigations into other suitable materials

In order to investigate which other material types could be applied as anodes according to multiple embodiments presented herein, the theoretical Li-ion lithiation capacity of a material is divided by the critical modulus of the material with Li metal. The metric describes how sensitive the lithiation capacity of a material can be suppressed by mechanical constriction and converted to lithium plating capacity of interest. The results of these computations are captured in FIGS. 18(a)-18(b). FIG. 18(a) shows the high-throughput calculation results of voltage (y-axis) and capacity over K_CTit (COK) (x-axis) for anodic reaction versus Li metal anode and FIG. 18(b) shows the high-throughput calculation results of capacity and capacity over K_Crit for anodic reaction versus Li metal anode. FIGS. 19(a), 20(a), 21 (a), and 22(a) shows the occurrence of elements in the range of COK > 500 mAh/g/GPa and COK*V > 600 mWh/g/GPa. FIGS. 19(b), 20(b), 21 (b), and 22(b) show the coappearance of two elements in the corresponding COK and COK*V ranges. FIGS. 19(c), 20(c), 21 (c), and 22(c) show the coappearance of three elements in the corresponding COK and COK*V ranges. FIG. 22(d) illustrates the high-throughput calculation results of voltage (y-axis) and lithiation composition over Kent (x-axis) for anodic reaction versus Li metal anode for 59,524 material entries within the plotted axes range. The voltage is the average lithiation voltage of a material versus Li⁺/Li, and Kent is the critical modulus at which lithiation reaction between Li metal and the material can be suppressed. Inset is the elemental distribution of 1 1 ,568 material entries in the region between the dashed lines and the boundary of the highest lithiation energy per lithium per unit constriction in FIG. 22(d).

Various concepts may be embodied as one or more methods, of which at least one example has been provided. The acts performed as part of the method may be ordered in any suitable way. Accordingly, embodiments may be constructed in which acts are performed in an order different than illustrated, which may include performing some acts simultaneously, even though shown as sequential acts in illustrative embodiments. Put differently, it is to be understood that such features may not necessarily be limited to a particular order of execution, but rather, any number of threads, processes, services, servers, and/or the like that may execute serially, asynchronously, concurrently, in parallel, simultaneously, synchronously, and/or the like in a manner consistent with the disclosure. As such, some of these features may be mutually contradictory, in that they cannot be simultaneously present in a single embodiment. Similarly, some features are applicable to one aspect of the innovations, and inapplicable to others.

In addition, the disclosure may include other innovations not presently described. Applicant reserves all rights in such innovations, including the right to embodiment such innovations, file additional applications, continuations, continuations-in-part, divisionals, and/or the like thereof. As such, it should be understood that advantages, embodiments, examples, functional, features, logical, operational, organizational, structural, topological, and/or other aspects of the disclosure are not to be considered limitations on the disclosure as defined by the embodiments or limitations on equivalents to the embodiments. Depending on the particular desires and/or characteristics of an individual and/or enterprise user, database configuration and/or relational model, data type, data transmission and/or network framework, syntax structure, and/or the like, various embodiments of the technology disclosed herein may be implemented in a manner that enables a great deal of flexibility and customization as described herein.

While specific embodiments of the present disclosure have been outlined above, many alternatives, modifications, and variations will be apparent to those skilled in the art. Accordingly, the embodiments set forth herein are intended to be illustrative, not limiting. Various changes may be made without departing from the spirit and scope of the disclosure. Where methods and steps described above indicate certain events occurring in a certain order, those of ordinary skill in the art having the benefit of this disclosure would recognize that the ordering of certain steps may be modified, and such modification are in accordance with the variations of the disclosure. Additionally, certain of the steps may be performed concurrently in a parallel process, when possible, as well as performed sequentially as described above. The embodiments have been particularly shown and described, but it will be understood that various changes in form and details may be made.

Claims

CLAIMS What is claimed is:

1 . An electrochemical cell, comprising: a cathode comprising lithium; an anode comprising an anode material having a plurality of voids; and a solid state electrolyte disposed between the cathode and the anode, wherein the anode is formulated to cause lithium metal to be deposited in the plurality of voids during charging of the electrochemical cell.

2. The electrochemical cell of claim 1 , wherein each of the plurality of voids has a cross-sectional dimension in a range of about 5 nm to about 100 pm.

3. The electrochemical cell of claim 1 or 2, wherein the anode material includes a plurality of particles, each of the plurality of particles having a diameter in a range of about 1 pm to about 100 pm.

4. The electrochemical cell of any of the preceding claims, wherein the anode material is formulated such that a volume of the plurality of voids changes by less than 100% during charging and discharging of the electrochemical cell.

5. The electrochemical cell of any of the preceding claims, wherein the anode material comprises at least one of Si, Si alloy, a Si-carbon composite, a Si alloy-carbon composite, Mg metal, a binary Mg Alloy, a ternary Mg alloy, a binary Mg alloy-carbon composite optionally including a solid electrolyte and/or a polymer binder, or a ternary Mg alloy carbon-composite optionally including a solid electrolyte and/or a polymer binder.

6. The electrochemical cell of any of the preceding claims, wherein the anode material is under mechanical constriction, the anode material having constriction susceptibility.

7. The electrochemical cell of claim 6, further comprising: a surface layer on the anode, the surface layer being formed from a reaction between the anode material and lithium ions; and the mechanical constriction causes the surface layer to have a thickness of less than 500 nm.

8. The electrochemical cell of claim 6 or 7, wherein the mechanical constriction is caused by at least one of: the anode material having a local effective modulus of at least about 0.3 GPa, or an external pressure in a range of about 0.05MPa to about 50 MPa exerted on the electrochemical cell.

9. An electrochemical cell, comprising: a cathode comprising lithium; an anode comprising an anode material, the anode material having a local effective modulus of at least about 0.3 GPa causing the anode to be under mechanical constriction; and a solid state electrolyte disposed between the cathode and the anode, wherein the anode is formulated to cause lithium metal to be deposited on the anode material during charging of the electrochemical cell.

10. The electrochemical cell of claim 9, wherein the anode material comprises at least one of Si, a Si- carbon composite, Mg metal, a binary Mg alloy, or a ternary Mg alloy.

11 . The electrochemical cell of claim 9 or 10, wherein the anode material comprises a material having a capacity over Kcrit (COK) of > 500 mAh/g/GPa and (Kent x V) (COK*V) of > 600 mWh/g/GPa.

12. The electrochemical cell of claim 11 , wherein the anode material comprises at least one of Si, Si alloy, a Si-carbon composite, a Si alloy-carbon composite, Mg metal, a binary Mg Alloy, a ternary Mg alloy, a binary Mg alloy-carbon composite optionally including a solid electrolyte and/or a polymer binder, or a ternary Mg alloy carbon-composite optionally including a solid electrolyte and/or a polymer binder.

13. The electrochemical cell of claim 12, wherein the anode material comprises at least one of LiMgs, MgyAh, Mgi49Lii, Mgi4gBai, Mgi4gCai, Mgi4gSi, Mgi4gAgi, Mg?Bi , MgPb2~s, MgTei~2, MgHgs-s, MgAh~2, MgHi~3, Mglns, MgGe2~s, MgSh~3, MgSbo.5~3, MgS -s, MgGai~s, or NaiMgi4Bi.

14. The electrochemical of claim 9, wherein the anode material comprises a material having a capacity over Kcrit (COK) of > 500 mAh/g/GPa and (Kcrit x V) (COK*V) of e [500, 600] mWh/g/GPa.

15. The electrochemical cell of claim 9, wherein the anode material comprises a material having a capacity over Kcrit (COK) of > 500 mAh/g/GPa and COK*V e [300, 500] mWh/g/GPa.

16. An electrochemical cell, comprising a cathode including lithium; an anode comprising an anode material, the anode material including a plurality of particles; and a solid state electrolyte disposed between the cathode and the anode, wherein the anode is formulated such that initial charging of the electrochemical cell causes lithium metal to be deposited on the anode, the lithium metal deposition causing a volume of the plurality of particles by less than 300% of an original volume of the plurality of particles.

17. The electrochemical cell of claim 16, wherein the anode material comprises at least one of Si, Si alloy, a Si-carbon composite, a Si alloy-carbon composite, Mg metal, a binary Mg Alloy, a ternary Mg alloy, a binary Mg alloy-carbon composite optionally including a solid electrolyte and/or a polymer binder, or a ternary Mg alloy carbon-composite optionally including a solid electrolyte and/or a polymer binder.

18. The electrochemical cell of claim 16 or 17, wherein each of the plurality of particles has a diameter in a range of about 1 pm to about 100 pm.

19. The electrochemical cell of any of the preceding claims, wherein: the anode material includes a plurality of voids; and the anode material is formulated such that a volume of the plurality of voids changes by less than 50% during charging and discharging of the electrochemical cell.

20. The electrochemical cell of any of the preceding claims, wherein the anode material is under mechanical constriction, the mechanical constriction causing the lithium metal to be deposited as a surface layer on the anode, the surface layer having a thickness of less than 500 nm.

21 . A method of releasing electrical energy comprising: a) providing a battery comprising: i) a cathode comprising Li; ii) an anode comprising an anode material having a plurality of voids; and iii) a solid state electrolyte disposed between the anode and the cathode; and b) providing electrical energy to the battery to cause Li⁺ ions to migrate from the cathode to the anode and deposit in the plurality of voids as Li metal during charging.

22. The method of claim 21 , further comprising electrically connecting a load between the anode and cathode to allow the Li metal in the plurality of voids to oxidize and migrate to the cathode and deposit therein as Li⁺ ions during discharge.

23. The method of claim 21 , wherein a portion of the Li⁺ ions react with a surface of the anode material to form a surface layer with the anode material.

24. The method of claim 23, wherein the surface layer is less than 500 nm in thickness.

25. The method of claim 23, wherein the anode material comprises micron-scale and/or nano-scale particles and the surface layer is less than 500 nm in thickness.

26. The method of claim 21 , wherein a volume of the particles after a first charging is <300% of an original particle volume.

27. The method of claim 21 , wherein an average particle diameter after 10 charge and discharge cycles is >70% of an original particle diameter.

28. The method of claim 21 , wherein the anode material does not crack or swell during charging or discharging.

29. The method of claim 23, wherein a portion of the anode material under the surface layer does not undergo lithiation.

30. The method of claim 21 , wherein the battery is under mechanical constriction.

31 . The method of claim 30, wherein the mechanical constriction is provided by an external pressure of 0.05-50 MPa.

32. The method of claim 30, wherein the mechanical constriction is provided by a local effective modulus (Ketf) of the anode material of at least 0.3 GPa.

33. The method of claim 21 , wherein the anode material comprises Si.

34. The method of claim 33, wherein the anode material comprises a Si-graphite composite formed of nano-scale and/or micron-scale Si and graphite particles.

35. The method of claim 21 , wherein at least 10% of the stored electrical energy is stored as lithium metal.

36. A solid state battery comprising: a) a cathode comprising Li; b) an anode comprising an anode material having a plurality of voids; and c) a solid state electrolyte disposed between the anode and the cathode; wherein the anode material is under mechanical constriction, and wherein Li⁺ ions from the cathode deposit in the plurality of voids as Li metal during charging of the battery.

37. The battery of claim 36, wherein the mechanical constriction limits lithiation of the anode material to a surface layer of less than 500 nm.

38. The battery of claim 36, wherein the mechanical constriction is provided by an external pressure of 0.05-50 MPa.

39. The battery of claim 36, wherein the mechanical constriction is provided by a local effective modulus (Ketf) of the anode of at least 0.3 GPa.

40. The battery of claim 16, wherein the anode material comprises a material having a capacity over K_Crit (COK) of > 500 mAh/g/GPa and (K_crit x V) (COK*V) of > 600 mWh/g/GPa.

41 . The battery of claim 36, wherein the anode material comprises Mg metal or a binary or ternary alloy of Mg.

42. The battery of claim 41 , wherein the anode material comprises at least one of LiMgs, MgyAh , Mgi49Lh , Mgi4gBai , Mgi4 MgAh~2, MgHi~3, Mglns,

43. The battery of claim 36, wherein the anode material comprises a material having a capacity over Kent (COK) of > 500 mAh/g/GPa and (K_crit x V) (COK*V) of e [500, 600] mWh/g/GPa.

44. The battery of claim 36, wherein the anode material comprises: an alloy of Mg of formula MgxSh x, MgsAI, Li_xMgi-x, Mg4AhSi4, or LixMg_ySii-x-_y, wherein 1 >= x >= 0 and 0 < y < 1 ; or metal-doped Mg of formula MgxM’_yM”i-_x-y, wherein x > 0.8 and y < 0.2 and wherein M' and M” are metals; or doped MgO of formula (MgO)xA_yB_zOi x-_y-z, wherein x > 0.9 and y<0.1 and z<0.1 and wherein A and B are elements other than Mg and O; or a binary Mg compound.

45. The battery of claim 36, wherein the anode material comprises a material having a capacity over Kcrit (COK) of > 500 mAh/g/GPa and COK*V e [300, 500] mWh/g/GPa.

46. The battery of claim 36, wherein the anode material comprises: doped MgO of formula (MgO)xA_yB_zOi x-_y-z, wherein x > 0.7 y < 0.3 and z < 0.3 and wherein A and B are elements other than Mg or O; compounds of formula Mg_xSii x; compounds of formula Mg_xSi_yOi-x-_y; or

Mg metal alloys of formula Mg_xM’_yM”i-x-_y, wherein x > 0.8 and y < 0.2 and wherein M' and M” are metals.

47. The battery of claim 36, wherein the anode material comprises Si.

48. The battery of claim 47, wherein the anode material comprises a Si-graphite composite formed of nano-scale and/or micron-scale Si and graphite particles.

49. The battery of claim 36, wherein the anode material is coated onto Li foil on a current collector.

50. The battery of claim 36, wherein the anode material undergoes a self-limiting reaction with lithium under mechanical constriction to form a surface layer.

51. The battery of claim 50, wherein the surface layer is less than 500 nm in thickness.

52. The battery of claim 50, wherein the anode material comprises micron-scale and/or nano-scale particles and the surface layer is less than 500 nm in thickness.

53. The battery of claim 36, wherein a volume of the particles after a first charging is <300% of an original particle volume.

54. The battery of claim 36, wherein an average particle diameter after 10 charge and discharge cycles is >70% of an original particle diameter.

55. The battery of claim 36, wherein the anode material does not crack or swell during charging or discharging.

56. The battery of claim 36, wherein the voids of the plurality of voids have a cross-sectional dimension of between 1 nm and 1000 pm.

57. The battery of claim 36, wherein the anode material comprises particles of 1 nm to 100 pm in diameter.

58. The battery of claim 36, wherein the anode material comprises a surface layer or coating that inhibits lithiation.

59. The battery of claim 36, wherein the battery has a current density of 0.01 - 200 mA/cm².

60. The battery of claim 36, wherein the battery has a cathode loading of 0.1 - 200 mg/cm².

61 . The battery of claim 36, wherein the battery has a 1 -20 mAh/cm² area capacity.

62. The battery of claim 36, wherein the battery can be cycled for 1 ,000-20,000 cycles at 1 -60 minutes or

0.1 -30 C-rates of charge and discharge.

63. The battery of claim 36, wherein the battery has a pouch, prismatic, or cylindrical cell format.

64. The battery of claim 36, further comprising a protection layer and/or a multilayer of solid state electrolytes.

65. The battery of claim 64, wherein the protection layer and/or the multilayer of solid state electrolytes is deposited, cast, or transferred onto the cathode, the anode, or a substrate in a layer-by-layer process.

66. The battery of claim 64, wherein the multilayer comprises n layers of solid state electrolyte, wherein n = >2.