DETAILED ACTION
Response to Amendment
In the amendment dated 6/15/2021, the following has occurred: Claim 1 has been amended.
Claims 1, 3-6, and 8-12 are pending. This communication is a Final Rejection in response to the "Amendment" and "Remarks" filed on 6/15/2021.
The text of those sections of Title 35, U.S. Code not included in this action can be found in a prior Office action.
Claim Rejections - 35 USC § 103
Claims 1, 3-6, and 8 are rejected under 35 U.S.C. 103 as being unpatentable over CN 109167096 A (CN'096) in view of WO 2012/108270 A1 (WO'270).
As to Claim 1:
CN'096 discloses an electrolyte for a lithium-sulfur battery (CN'096, Pgs. 1–2, Title, Abstract, Technical Field; Pg. 4, Claims 1, 8), comprising: a base electrolyte comprising a lithium salt and an organic solvent (CN'096, Pg. 2, "summary of the invention", "Specific implementation methods"; Pg. 3, Example 1 disclosing
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dissolved in a 1:1 volume ratio of 1,3-dioxolane and dimethoxyethane; Pg. 4, Claims 1, 4–6); and an electrolyte additive, wherein the electrolyte additive comprises an isocyanate functional group
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However, CN'096 does not explicitly disclose wherein the electrolyte additive further comprises one or more of hexamethylene diisocyanate, isophorone diisocyanate, methylene diisocyanate, toluene diisocyanate, 4,4-diisocyanato dicyclohexylmethane, 1,5-naphthalene diisocyanate, tetramethyl xylene diisocyanate, para-phenylene diisocyanate, 1,4-cyclohexane diisocyanate, 1,8-diisocyanatooctane, or 2,4,4-trimethylhexamethylene diisocyanate (CN'096 discloses
p
-toluenesulfonyl isocyanate, which is a monoisocyanate).
WO'270 discloses nonaqueous secondary battery electrolytes containing isocyanate-functional additives, and explicitly teaches that the electrolyte additive comprises a compound having at least two isocyanate groups in the molecule, specifically naming hexamethylene diisocyanate, toluene diisocyanate, isophorone diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, and 2,4,4-trimethylhexamethylene diisocyanate (WO'270, Pgs. 2–3, Section 1-1; Pg. 63, Claim 4; Pg. 64, Claim 13; Pg. 65, Claims 18, 21). WO'270 further teaches that the polyfunctional isocyanate compound is included in an amount of usually 0.001% to 10% by mass, preferably 5% by mass or less, and more preferably 3% by mass or less (WO'270, Pg. 3, Section 1-1), and specifically illustrates an electrolyte containing 1% by mass of hexamethylene diisocyanate (WO'270, Pg. 27, Comparative Example 1-4) to form a protective interface film on the electrode surface that suppresses side reactions and solvent decomposition (WO'270, Pgs. 2–3, 27).
CN'096 and WO'270 are analogous arts because both references belong to the same field of endeavor, namely nonaqueous electrolytes for secondary batteries comprising lithium salts, organic solvents, and isocyanate additives. Furthermore, both references are reasonably pertinent to the particular problem of stabilizing the electrode/electrolyte interface, mitigating parasitic electrode reactions, and preventing battery capacity degradation by incorporating isocyanate additives that react to form protective solid electrolyte interface (SEI) films on electrode surfaces.
It would have been obvious to a person skilled in the art before the effective filing date of the instant application to replace or supplement the monoisocyanate additive (
p
-toluenesulfonyl isocyanate) of CN'096 with one or more of the diisocyanate compounds taught by WO'270, such as hexamethylene diisocyanate or toluene diisocyanate, in an amount of 1 to 5 parts by weight based on 100 parts by weight of the electrolyte. A person of ordinary skill in the art would have been motivated to make this substitution because WO'270 explicitly teaches that diisocyanates react at the electrode interface to form durable, cross-linked protective films that suppress unwanted interfacial decomposition reactions and improve cycle retention, thereby predictably enhancing electrode stability and cycle performance in the lithium-sulfur battery of CN'096.
As to Claim 3:
CN'096 discloses the electrolyte of claim 1 (see the rejection of claim 1); and wherein the lithium salt comprises at least one of
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(CN'096, Pg. 2, "summary of the invention", "Specific implementation methods"; Pg. 3, Example 1; Pg. 4, Claim 4).
As to Claim 4:
CN'096 discloses the electrolyte of claim 1 (see the rejection of claim 1); and wherein the lithium salt is included at a molar concentration of 0.1 M to 5 M (CN'096, Pg. 2, "summary of the invention", "Specific implementation methods"; Pg. 3, Examples 1–3 disclosing lithium salt concentrations of 1 mol/L, 0.5 mol/L, and 5 mol/L, respectively; Pg. 4, Claim 2 disclosing a lithium salt concentration of 0.5 to 5 mol/L, which falls within the claimed range of 0.1 M to 5 M).
As to Claim 5:
CN'096 discloses the electrolyte of claim 1 (see the rejection of claim 1); wherein the organic solvent is a non-aqueous organic solvent (CN'096, Pg. 1, "background technology"; Pg. 2, "summary of the invention", "Specific implementation methods"; Pg. 4, Claims 1, 5); and the non-aqueous organic solvent comprises at least one of an ether-based material, 1,2-dimethoxyethane, 1,3-dioxolane, or dimethyl sulfoxide (CN'096, Pg. 2, "summary of the invention", "Specific implementation methods", disclosing that the organic solvent is an ether organic solvent comprising at least one of dioxolane, dimethoxyethane, diglyme, or tetraethylene glycol dimethyl ether; Pg. 3, Example 1, explicitly preparing the electrolyte using a 1:1 volume ratio mixture of 1,3-dioxolane and dimethoxyethane; Pg. 4, Claims 5, 6).
As to Claim 6:
CN'096 discloses the electrolyte of claim 5 (see the rejection of claim 5); and wherein the ether-based material comprises at least one of diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, or tetraethylene glycol dimethyl ether (CN'096, Pg. 2, "summary of the invention", "Specific implementation methods", disclosing that the ether organic solvent comprises at least one of diglyme [diethylene glycol dimethyl ether] or tetraethylene glycol dimethyl ether; Pg. 4, Claim 6).
As to Claim 8:
CN'096 discloses a lithium-sulfur battery (CN'096, Pgs. 1–2, Title, Abstract, Technical Field; Pg. 2, "summary of the invention"; Pg. 4, Claim 8), comprising: the electrolyte for the lithium-sulfur battery according to claim 1 (see the rejection of claim 1); a cathode comprising a sulfur compound (CN'096, Pg. 2, "summary of the invention", "Specific implementation methods", disclosing a positive electrode material of elemental sulfur, lithium sulfide, sulfenyl composite material, organic sulfide, or sulfur-carbon polymer; Pg. 3, "Experimental Test", step 1, preparing an S/C positive plate containing sulfur-carbon composite material; Pg. 4, Claim 9); an anode comprising lithium (CN'096, Pg. 3, "Experimental Test", step 2, disclosing a lithium metal negative electrode; Pg. 4, Claim 9); and a separator interposed between the cathode and the anode (CN'096, Pg. 2, "summary of the invention", "Specific implementation methods", disclosing a positive electrode, a negative electrode, and a membrane/diaphragm; Pg. 3, "Experimental Test", step 2, disclosing assembling a button cell with a Celgard 2400 membrane interposed between the S/C positive plate and lithium metal negative electrode; Pg. 4, Claims 8, 9).
Response to Arguments
Applicant's arguments filed 8/23/26 have been fully considered but they are not persuasive.
First, applicant argues that the additive in CN'096 operates through a decomposition-based film-forming mechanism, whereas the claimed invention relies on a spontaneous room-temperature nucleophilic addition reaction between isocyanate groups and dissolved lithium polysulfide intermediates.
Claim 1 is directed to an "electrolyte for a lithium-sulfur battery, comprising: a base electrolyte comprising a lithium salt and an organic solvent; and an electrolyte additive...". Claim 1 does not recite lithium polysulfide, does not recite any chemical reaction, and does not recite any resulting polymer product. Under MPEP § 2114, a composition of matter claim is defined by its recited physical and chemical components, not by downstream reaction pathways, non-recited properties, or intended uses. The unreacted liquid electrolyte defined in Claim 1 is structurally complete as a mixture of a lithium salt, an organic solvent, and a diisocyanate additive. An unrecited mechanism cannot distinguish the claimed electrolyte composition from the obvious combination of known electrolyte components taught by CN'096 and WO'270.
Second, applicant contends that WO'270 is directed to conventional secondary batteries (Li-ion) devoid of lithium polysulfide intermediates, and therefore a person of ordinary skill in the art (POSITA) would not have been motivated to combine WO'270 with CN'096.
The primary reference, CN'096, is expressly directed to lithium-sulfur secondary batteries (CN'096, Title, Abstract, Claims 1, 8). CN'096 explicitly identifies the problem of soluble polysulfides dissolving into the ether electrolyte and diffusing to the negative electrode during discharge, and teaches solving this problem by adding an isocyanate functional additive to form a protective interface film (CN'096, Pgs. 1–2).
Both CN'096 and WO'270 belong to the same field of endeavor (non-aqueous secondary battery electrolytes) and address the common problem of stabilizing electrode interfaces to suppress parasitic electrolyte decomposition and capacity fading. WO'270 explicitly teaches that multi-functional isocyanates—specifically naming hexamethylene diisocyanate, toluene diisocyanate, and isophorone diisocyanate—react at electrode interfaces in non-aqueous electrolytes to form durable, cross-linked protective films that suppress unwanted decomposition and gas generation (WO'270, Pgs. 2–3, Section 1-1; Pg. 63, Claim 4).
A person skilled in the art seeking to enhance the durability of the isocyanate-derived interface film in the lithium-sulfur battery of CN'096 would have found it obvious to substitute the monofunctional isocyanate of CN'096 with the multi-functional diisocyanates taught by WO'270. The motivation is provided by WO'270's express teaching that diisocyanates form superior cross-linked protective networks at electrode surfaces, thereby predictably mitigating interfacial side reactions and improving cycle durability in the lithium-sulfur battery of CN'096.
Third, applicant argues that the range of 1 to 5 parts by weight is critical and tied to the stoichiometry of polysulfide consumption.
The claimed range falls squarely within overlapping prior art disclosures. CN'096 explicitly discloses an additive content range of 0.1% to 5% by weight, and specifically exemplifies 1%, 2%, 3%, and 5% by weight in a lithium-sulfur battery (CN'096, Pg. 2; Pg. 3, Example 1; Pg. 4, Claim 2). WO'270 similarly teaches that the diisocyanate additive is preferably present in an amount up to 5% by mass (more preferably 3% by mass or less), and specifically evaluates 1% by mass of hexamethylene diisocyanate (WO'270, Pg. 3, Section 1-1; Pg. 27, Comparative Example 1-4). Under MPEP § 2144.05, where a claimed range overlaps ranges disclosed in the prior art, a prima facie case of obviousness is established (In re Peterson, 315 F.3d 1325). WO'270 also teaches that inadequate additive amounts fail to form a stable film, while excessive amounts increase resistance (WO'270, Pgs. 3–4). Selecting 1 to 5 parts by weight represents routine optimization within overlapping ranges disclosed in the cited art.
Fourth, applicant asserts that Table 1, FIGS. 2A–2B, and FIGS. 8–11 of the specification demonstrate unexpected results.
Under MPEP § 716.02(e), evidence of unexpected results must compare the claimed invention with the closest prior art. In Table 1 and FIG. 2, Applicant compares hexamethylene diisocyanate to tetraethylene glycol diacrylate (TEGDA). An acrylate cross-linker is not the closest prior art; the closest prior art is the isocyanate additive of CN'096 (
p
-toluenesulfonyl isocyanate). Comparing an isocyanate to an acrylate does not demonstrate unexpected results over known isocyanate additives. In FIGS. 8–11 and Table 4, Applicant compares 3 wt% HDI against a control containing 0 wt% additive. Showing that an additive outperforms no additive at all does not demonstrate unexpected results over prior art (CN'096 and WO'270) that already teaches adding isocyanates at 1 to 5 wt% to passivate electrodes and improve cycling.
Applicant provides no comparative data establishing that the claimed diisocyanates achieve unexpected results compared to the closest prior art isocyanate additive of CN'096. Thus, the prima facie case of obviousness is not rebutted.
For the reasons above, applicant's arguments have been fully considered but they are not persuasive.
Allowable Subject Matter
Claims 9-12 are objected to as being dependent upon a rejected base claim, but would be allowable if rewritten in independent form including all of the limitations of the base claim and any intervening claims.
Conclusion
Applicant's amendment necessitated the new ground(s) of rejection presented in this Office action. Accordingly, THIS ACTION IS MADE FINAL. See MPEP § 706.07(a). Applicant is reminded of the extension of time policy as set forth in 37 CFR 1.136(a).
A shortened statutory period for reply to this final action is set to expire THREE MONTHS from the mailing date of this action. In the event a first reply is filed within TWO MONTHS of the mailing date of this final action and the advisory action is not mailed until after the end of the THREE-MONTH shortened statutory period, then the shortened statutory period will expire on the date the advisory action is mailed, and any nonprovisional extension fee (37 CFR 1.17(a)) pursuant to 37 CFR 1.136(a) will be calculated from the mailing date of the advisory action. In no event, however, will the statutory period for reply expire later than SIX MONTHS from the mailing date of this final action.
Any inquiry concerning this communication or earlier communications from the examiner should be directed to JIMMY K VO whose telephone number is (571)272-3242. The examiner can normally be reached Monday - Friday, 8 am to 6 pm EST.
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If attempts to reach the examiner by telephone are unsuccessful, the examiner’s supervisor, Barbara Gilliam can be reached at (571) 272-1330. The fax phone number for the organization where this application or proceeding is assigned is 571-273-8300.
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/JIMMY VO/
Primary Examiner
Art Unit 1723
/JIMMY VO/Primary Examiner, Art Unit 1723
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