) ( (51) International Patent Classification: (US). HUDSON, Will; c/o QuantumScape Corporation, C08F 220/18 (2006.01) C08L 33/20 (2006.01) 1730 Technology Drive, San Jose, California 95 110 (US). C08F 220/42 (2006.01) D01F 9/22 (2006.01) YAMAGO, Shigeru; c/o QuantumScape Corporation, C08F 220/44 (2006.01) H01G 11/56 (2013.01) 1730 Technology Drive, San Jose, California 951 10 (US). (21) International Application Number: (74) Agent: OSTOMEL, Todd etal.; Squire Patton Boggs (US) PCT/US20 19/03003 8 LLP, 275 Battery Street, Suite 2600, San Francisco, Cali¬ fornia 941 11 (US). (22) International Filing Date: 30 April 2019 (30.04.2019) (81) Designated States (unless otherwise indicated, for every kind of national protection av ailable) . AE, AG, AL, AM, (25) Filing Language: English AO, AT, AU, AZ, BA, BB, BG, BH, BN, BR, BW, BY, BZ, (26) Publication Language: English CA, CH, CL, CN, CO, CR, CU, CZ, DE, DJ, DK, DM, DO, DZ, EC, EE, EG, ES, FI, GB, GD, GE, GH, GM, GT, HN, (30) Priority Data: HR, HU, ID, IL, IN, IR, IS, JO, JP, KE, KG, KH, KN, KP, 62/665,414 0 1 May 2018 (01.05.2018) US KR, KW, KZ, LA, LC, LK, LR, LS, LU, LY, MA, MD, ME, (71) Applicants: QUANTUMSCAPE CORPORATION MG, MK, MN, MW, MX, MY, MZ, NA, NG, NI, NO, NZ, [US/US]; 1730 Technology Drive, San Jose, Califor¬ OM, PA, PE, PG, PH, PL, PT, QA, RO, RS, RU, RW, SA, nia 95 110 (US). KYOTO UNIVERSITY [JP/JP]; 36-1, SC, SD, SE, SG, SK, SL, SM, ST, SV, SY, TH, TJ, TM, TN, Yoshida-Honmachi, Sakyo-Ku, Kyoto-Shi, Kyoto, kyoto TR, TT, TZ, UA, UG, US, UZ, VC, VN, ZA, ZM, ZW. 606-8501 (JP). (84) Designated States (unless otherwise indicated, for every (72) Inventors: SINGH, Mohit; c/o QuantumScape Corpora¬ kind of regional protection available) . ARIPO (BW, GH, tion, 1730 Technology Drive, San Jose, California 95 110 GM, KE, LR, LS, MW, MZ, NA, RW, SD, SL, ST, SZ, TZ, (54) Title: POLYACRYLONITRILE GELS FOR ENERGY STORAGE FIG. 2a (57) Abstract: Provided herein are rechargeable battery (e.g., Li-ion and Li-metal anode) catholytes and electrolyte separators that include a chemically cross-linked polymer and a solvent selected from the group consisting of a nitrile, a dinitrile, or a combination thereof; processes for making and using the same; and rechargeable batteries and electrochemical cells that include high voltage stable catholytes and/or electrolyte separators. [Continued on next page] W O 2019/213159 A 1 UG, ZM, ZW), Eurasian (AM, AZ, BY, KG, KZ, RU, TJ, TM), European (AL, AT, BE, BG, CH, CY, CZ, DE, DK, EE, ES, FI, FR, GB, GR, HR, HU, IE, IS, IT, LT, LU, LV, MC, MK, MT, NL, NO, PL, PT, RO, RS, SE, SI, SK, SM, TR), OAPI (BF, BJ, CF, CG, Cl, CM, GA, GN, GQ, GW, KM, ML, MR, NE, SN, TD, TG). Declarations under Rule 4.17: as to the identity of the inventor (Rule 4.17 (i)) as to applicant's entitlement to apply for and be granted a patent (Rule 4.17(H)) as to the applicant's entitlement to claim the priority of the earlier application (Rule 4.17(iii)) Published: with international search report (Art. 21(3)) before the expiration of the time limit for amending the claims and to be republished in the event of receipt of amendments (Rule 48.2(h)) POLYACRYLONITRILE GELS FOR ENERGY STORAGE CROSS-REFERENCE TO RELATED APPLICATIONS [1] This applications claims the benefit of priority to US Provisional Patent Application No. 62/665,414, filed May 1, 2018, the entire contents of which are herein incorporated by reference in its entirety for all purposes. FIELD [2] The present disclosure sets forth compositions comprising chemically cross-linked polymers. These chemically cross-linked polymers may include cyano (-CN) functional groups and are formulated with a nitrile solvent, a dinitrile solvent, or both. These chemically cross-linked polymers may tolerate high voltage conditions without reacting in a detrimental manner. The chemically cross-linked polymers set forth herein may be characterized as having a wide electrochemical stability window (ESW) and may be useful as rechargeable battery electrolyte separators. Also set forth herein are methods of making and using these electrolyte separators in electrochemical cells and energy storage devices. BACKGROUND [3] Previous researchers have prepared high voltage electrochemical batteries that include poly(acrylonitrile) (PAN) polymer electrolyte separators. However, these electrolyte separators were made by physical cross-linking reactions (see, e.g.. Sekhon, S. S.; Arora, N.; Agnihotry, S. A. Solid State Ionics 2000, 136- 137, 2101). Physical cross-linking can be defined as physical entanglement of separate polymer strands but without forming chemical bonds between the entangled polymer strands. For example, physical cross-linking may include spraying a solution of polymers onto a substrate and then drying the solution to form an entangled mat. Physical cross-linking reactions result in non-uniform polymers with stochastic properties, e.g., inhomogeneous structures, which vary with respect to molecular weight, amount, type, length, and uniformity of cross-linking. [4] Accordingly, there exists a need for improved polymer electrolyte separators for electrochemical batteries. Set forth herein are such improved polymers as well as other solutions to problems in the relevant field. SUMMARY [5] In one embodiment, set forth herein is a composition including a chemically cross-linked aprotic polymer comprising cyano (-CN) functional groups and a solvent selected from the group consisting of a nitrile, a dinitrile, and a combination thereof. In some embodiments, set forth herein is a composition including a chemically cross-linked polymer comprising at least one cyano (-CN) functional group and a solvent selected from the group consisting of a nitrile, a dinitrile, and a combination thereof. [6] In a second embodiment, set forth herein is a process for making a composition, including: step 1 : copolymerizing an acrylonitrile (AN) monomer and a methacrylamide monomer to form a polymer, wherein the methacrylamide monomer comprises amide functional groups; and step 2 : chemically cross-linking the polymer using a bifunctional cross-linker to form a cross-linked polymer. [7] In a third embodiment, set forth herein is a composition made by any one of the processes disclosed herein. [8] In a fourth embodiment, set forth herein is an electrochemical cell including a lithium metal negative electrode, a solid separator, and a positive electrode; wherein the positive electrode comprises an active material and a catholyte; wherein the catholyte comprises a chemically cross-linked polymer set forth herein; and a lithium salt. [9] In a fifth embodiment, set forth herein is an electrochemical cell including a lithium metal negative electrode, a solid separator, a positive electrode, and a bonding layer disposed between the solid separator and the positive electrode; wherein the positive electrode comprises an active material and a catholyte; and wherein the bonding layer comprises a chemically cross-linked polymer set forth herein; and a lithium salt. [10] In a sixth embodiment, set forth herein is a method of using an electrochemical cell set forth herein. [11] In a seventh embodiment, set forth herein is a method of storing an electrochemical cell, including: providing an electrochemical cell of any one of those set forth herein; wherein the electrochemical cell has greater than 20% state-of-charge (SOC); and storing the battery for at least one day. [12] In an eighth embodiment, set forth herein is a method of storing an electrochemical cell, including: providing an electrochemical cell of any one of those set forth herein; wherein the electrochemical cell has a voltage v. Li greater than 4.2 V; and storing the battery for at least one day. BRIEF DESCRIPTIONS OF THE DRAWINGS [13] FIGs. la-lc show the effect of time on the monomer conversion for the polymerization shown in Table 1, run 1. FIG. l a shows molecular weight as a function of percent conversion. FIG. l b shows Mn and D vs. the monomer conversion. FIG. l c shows SEC traces at different times. [14] FIGs. 2a-2b show fabrication of PAN-based gel swollen in adiponitrile. FIG. 2a shows SEC traces at different times and FIG. 2b shows photographs of polymer gels. [15] FIGs. 3a, 3b, and 3c show frequency dependence of storage modulus (FIG. 3a), loss modulus (FIG. 3b), and phase angle (FIG. 3c). [16] FIG. 4 shows ¾ NMR spectrum of 6F. DETAILED DESCRIPTION A. DEFINITIONS [17] As used herein, the term “about,” when qualifying a number, e.g., about 15 % w/w, refers to the number qualified and optionally the numbers included in a range about that qualified number that includes ± 10% of the number. For example, about 15 % w/w includes 15 % w/w as well as 13.5 % w/w, 14 % w/w, 14.5 % w/w, 15.5 % w/w, 16 % w/w, or 16.5 % w/w. For example, “about 75 °C,” includes 75 °C as well 68 °C, 69 °C, 70 °C, 7 1 °C, 72 °C, 73 °C, 74 °C, 75 °C, 76 °C, 77 °C, 78 °C, 79 °C, 80 °C, 8 1 °C, 82 °C, or 83 °C. [18] As used herein, “selected from the group consisting of’ refers to a single member from the group, more than one member from the group, or a combination of members from the group. A member selected from the group consisting of A, B, and C includes, for example, A only, B only, or C only, as well as A and B, A and C, B and C, as well as A, B, and C.