DETAILED ACTION
Notice of Pre-AIA or AIA Status
The present application, filed on or after March 16, 2013, is being examined under the first inventor to file provisions of the AIA .
Priority
Receipt is acknowledged of certified copies of papers required by 37 CFR 1.55.
Claim Rejections - 35 USC § 103
The following is a quotation of 35 U.S.C. 103 which forms the basis for all obviousness rejections set forth in this Office action:
A patent for a claimed invention may not be obtained, notwithstanding that the claimed invention is not identically disclosed as set forth in section 102, if the differences between the claimed invention and the prior art are such that the claimed invention as a whole would have been obvious before the effective filing date of the claimed invention to a person having ordinary skill in the art to which the claimed invention pertains. Patentability shall not be negated by the manner in which the invention was made.
The factual inquiries for establishing a background for determining obviousness under 35 U.S.C. 103 are summarized as follows:
1. Determining the scope and contents of the prior art.
2. Ascertaining the differences between the prior art and the claims at issue.
3. Resolving the level of ordinary skill in the pertinent art.
4. Considering objective evidence present in the application indicating obviousness or nonobviousness.
Claims 1-19 are rejected under 35 U.S.C. 103 as being unpatentable over Kim et al. (US 20180309161 A1) and further in view of Uematsu (EP 3038201 A1), Kato et al. (JP 6738721 B2) and Liang et al. (US 20220149437 A1)
Claim 1: Kim teaches a lithium secondary battery exhibiting high capacity and improved cycle characteristics [0020], including high capacity retention ratio (See example 2 in the figure),
wherein the secondary battery comprises a positive electrode, a negative electrode and an electrolyte [0026],
wherein the positive electrode includes a positive electrode current collector and the negative electrode includes a negative electrode current collector [0033],
wherein the lithium ion conductivity of the electrolyte is controlled to be in the range 11-20 mS/cm to ensure good ion diffusion and uniform electrode reaction [0031], and in turn, good cycle characteristics of the battery [0025],
wherein the electrolyte may have a viscosity of 1.0-4.0 cP (i.e., mPa.s), but preferably 1.0-3.0 cP at room temperature (25° C) [0043].
wherein the ion conductivity is controlled by adjusting the salt and the solvent in the electrolyte [0031],
wherein the electrolyte comprises a lithium salt such as LiPF6 [0044],
solvent preferably comprising a cyclic carbonate (i.e., cyclic ester) such as ethylene carbonate (EC), in combination with an chain carbonate, such as dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), or ethyl acetate (EA) or methyl propionate (MP) [0045],
wherein the cyclic ester may be 10-40 vol% but preferably 20-30 vol% of the total volume of the solvent [0045], such that the mass ratio of the cyclic ester to the chain ester is (i.e., β ) is 0.16-0.97.
Kim specifically teaches examples 1 and 2 comprising an electrolyte that comprises a mixture of three solvents electrolyte containing 1 M LiPF6 dissolved in ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) or ethyl acetate, mixed at a volume ratio of 3:4:3 (the calculated mass ratio of cyclic carbonate to chain carbonate when density is considered are 0.54 and 0.57, respectivlely), in combination with additives including 3 wt % of vinylene carbonate (VC), 0.5 wt % of 1,3-propane sultone (PS) and 1 wt % of ethylene sulfate (ESA),
a negative electrode comprising 1 wt % of carbon black, 96 wt % of natural graphite as a negative electrode active material, 2 wt% of styrene butadiene rubber (SBR) binder and 1 wt % of carboxymethyl cellulose (CMC) [0048],
and a positive electrode comprising 3wt % of carbon black, 95 wt % of positive electrode active material (LiNi1/3Mn1/3Co1/3O2) and 2 wt% of polyvinylidene fluoride (PVdF) as a binder [0048]. Kim further teaches the positive electrode material may contain compounds represented by the formular LixFePO4 wherein (0.5<x<1.3) [0036] which includes LiFePO4.
As described above, Kim teaches the optimum ranges of viscosity and ion conductivity to ensure high capacity retention. Kim further teaches the additives may affect ion conductivity and viscosity [0043]. While Kim teaches controlling the ionic conductivity by adjusting the electrolyte salt and the solvent to optimize capacity retention ratio, Kim does not teach how to control the viscosity to optimize the battery cycle characteristics.
Uematsu teaches a lithium-ion secondary battery [0197] compositionally similar to Kim’s battery, comprising graphite negative electrode active material [0183], and lithium iron phosphate (LiFePO4) positive electrode material [0156, 0176, 0207], a combination cyclic carbonate and a linear carbonate solvents [0134-0139], and additives [0149], wherein the cycle characteristics of the battery are optimized by addition of a silyl-group containing compound to the electrolyte while the viscosity of the silyl-group containing compound is lowered by other additives [0133].
Uematsu specifically teaches an electrolytic solution comprising small amounts (e.g., 1%) of a high viscosity silyl group-containing compound (A) additive [0008, table 1-table 3] [0133], such as tris(trimethylsilyl) phosphate [0222, table 1] that is conventionally added to an electrolytic solution to improve the cycle characteristics, input-output characteristics, and the lifetime of a lithium-ion secondary battery [0014, 0005], mixed with a silicon compound capable of decreasing viscosity [0012]. The decreased viscosity of the additive may consequently decrease the viscosity of the electrolyte while maintaining the improving effect of cycle characteristics of the battery [0124, 0126] (See table 5).
In addition to the additive described above, Uematsu also teaches additional additives for the electrolytic solution including, lithium difluorophosphate [0148-0149]. Uematsu further teaches that the additives improve the cycle property of the battery and lithium difluorophosphate is a preferred additive [0150]. The additive is preferably 0.001% to 3% by mass [0151]. Uematsu teaches when the content of the additive is less than 3%, ion conductivity of the battery tends to be enhanced [0151].
Therefore, in view of the benefits of electrolyte additives tris(trimethylsilyl) phosphate and lithium difluorophosphate discussed above, and their compatibility with electrolytic solutions similar to Kim’s electrolyte, it would have been obvious to one of ordinary skill in the art to have added a lithium difluorophosphate and tris(trimethylsilyl) phosphate to the electrolyte in Kim’s battery improve the battery’s cycle properties.
While Uematsu teaches that low temperatures affect the solubility of the lithium salt in the electrolyte [0145], Uematsu does not address how temperature affects other parameters such as viscosity. However, Kato teaches a non-aqueous electrolyte solution for a secondary battery that significantly improves low-temperature characteristics (page 2 para 4). Similar to Uematsu and Kim’s electrolytes, Kato’s electrolyte comprises a mixture of a cyclic carbonate and linear carbonate (page 4 para 8). Kato’s electrolytic composition also includes additives such as cyclic siloxane compounds (i.e., silyl-group containing compounds) including tris(trimethylsilyl) phosphate (page 6 para 5-6), and additives such as lithium difluorophosphate (page 7 para 3) and other compounds (page 8 para 3).
Kato further teaches the electrolyte is preferably used for high-capacity secondary batteries having a rated discharge capacitance of 3 ampere-hours (Ah) or more and less than 20 Ah (page 14 para 2). Kato further teaches the positive electrode plate is preferably designed to have a discharge capacity of 3 ampere-hours (Ah) or more and less than 20 Ah (i.e., theoretical capacity). Kato teaches if the capacity is less than the 3 Ah, the voltage drop due to the electrode reaction resistance becomes large when a large current is taken out, and the power efficiency may deteriorate, and the low-temperature discharge characteristics may also deteriorate (page 14 para 2).
Therefore, it would have been obvious to one of ordinary skill in the art to have designed Kim’s battery with a theoretical capacity of 3 Ah to improve the battery’s low-temperature discharge characteristics.
Similar to Kim and Uematsu, Kato also teaches the positive electrode may comprise LiFePO4 [0069] and the negative electrode comprises graphite [0130]. Kato further teaches the concentration of the active material present on the current collector (i.e., packing density) is between 1.0 g/cm3 and 2.0 g/cm3, preferably between 1.3 g/cm3 and 1.7 g/cm3 (Page 19 para 9). Kato teaches if this range is exceeded, the active material particles may be destroyed, leading to an increase in the initial irreversible capacity and deterioration in the high current density charge-discharge characteristics due to decrease in the permeability of the electrolyte solution to the vicinity of the current collector or active material interface (Page 19 para 9).
Therefore, it would have been obvious to one of ordinary skill in the art to have used an electrode with an electrode density between 1.3 g/cm3 and 1.7 g/cm3 in Kim’s battery improve the battery’s charge-discharge characteristics.
Kim does not teach the mass of the electrolyte. However, Liang teaches a lithium-ion battery with high safety performance, long cycle life, and good high-temperature storage performance [0016], wherein the mass of the battery and other parameters are optimized to improve the safety characteristics of the battery [0038] by minimizing gas formation as a result of high concentration of fluorine-containing salt [0047], such as LiPF6 salt [0045]. Liang specifically teaches an electrolyte comprising cyclic and chain carbonate solvents, LiPF6 salt [0045], and additives, such as lithium difluorophosphate [0049]. Liang specifically teaches an embodiment where the mass of the electrolyte is 14 g [0084].Liang further teaches when a high concentration of a fluorine containing lithium salt is included in the electrolyte, if a cyclic carbonate solvent is present, side reactions of the electrolyte may occur at the cathode to increase and an obvious increase of gas production, leading to the safety problem and the gas production problem during cycling of the lithium-ion battery [0050].
Therefore, it would have been obvious to one of ordinary skill in the art to have used 14 g of the electrolyte in Kim’s battery improve the battery’s safety properties at high temperatures.
Kim’s modified battery and electrolyte described above is characteristically and compositionally similar to the battery described in specification. Furthermore, the ranges of values provided above (i.e., Mel = 14; σ = 11-20; Cap = 3-20; PD = 1-2; η = 1-4, β = 0.16-0.97) and the calculated range of formula (1) ( 0.99 to 583.)) overlap with the ranges provided in the specification. Therefore, Kim’s battery meets the requirements of claim 1.
Claim 2: Kim teaches the electrical viscosity is 1.0-3.0 cP. Kim does not identically teach the range 2 to 5. However, overlapping ranges have been held in a case of obviousness (see MPEP 2144.05.I).
Claim 3: As described in claim 1, Kim teaches the mass ratio of the cyclic ester is 0.54.
Claim 4: Kim teaches the conductivity of the electrolyte is in the range 11-20 mS/cm.
Claim 5: Kim teaches the viscosity of the electrolyte is 1.0-3.0 cP [0043].
Claim 6: Kim teaches the proportional content of Kim does not teach the weight of the electrolyte has a value between 13 g and 15 g. However, Liang teaches the mass of the battery is 14 g [0084]. Therefore, it would have been obvious to one of ordinary skill in the art at the time of filing the instant invention to have used 14 g of the electrolyte in Kim’s battery improve the battery’s safety properties at high temperatures.
Claim 7 and 16-19: Kato teaches the electrode density (i.e., PD), preferably between 1.3 g/cm3 and 1.7 g/cm3 (page 19 para 9).
Claim 8: Kim teaches the chain ester solvent comprises ethyl methyl carbonate [0050].
Claim 9: Kim teaches the cyclic ester solvent comprises ethylene carbonate [0050].
Claim 10: Kim teaches the electrolyte comprises ethylene sulfate [0050].
Claim 11: Kim teaches the additives comprise 0.5 wt % of 1,3-propane sultone (PS) [0050].
Claim 12: Kim further teaches the ethylene sulfate is present at a 1% of ethylene sulfate. Kim does not teach a silicon-containing additive. However, Kato teaches a cyclic siloxane additive (i.e., silicon-containing additive), present at 0.001% to 5% (page 7 para 4-5) mass ratio in the electrolyte. Kato teaches if the concentration of the specific compound is too low, it may be difficult to obtain the effect of improving the low temperature characteristics, while if the concentration is too high, the charge / discharge efficiency may decrease (page 7 para 4-5). Kato further teaches an additional other compound added to the electrolyte including sulfur-containing compound ethylene sulfate (page 8 para 2-3) with a mass content between 0.01% and 5%. Kato teaches by adding these compounds, it is possible to improve the capacity maintenance characteristics and cycle characteristics after high temperature storage (page 8 para 8).
Therefore, it would have been obvious to one of ordinary skill in the art at the time of filling the instant invention to have added 1% of a sulfur-containing additive and 1% of a silicon-containing additive to Kim’s electrolyte, such that the total mass content of the silicon containing additive and the sulfur-containing additive (i.e., Wsi + Ws) is 2%, and the ratio of the mass content of the silicon-containing compound to the mass content of the sulfur containing compound (i.e., Wsi / Ws) is 1, to further improve the cycle property of the battery.
Claim 13: Kim further teaches the ethylene sulfate is present at a 1% of ethylene sulfate. Kim does not teach lithium difluorophosphate as an additive. However, Uematsu teaches lithium difluorophosphate additive present at 0.1% mass ratio in the electrolyte (example 51, Table 5) [0289, 0148-0149]. Uematsu teaches the additive further enhances the cycle property of the battery [0150].
Therefore, it would have been obvious to one of ordinary skill in the art at the time of filling the instant invention to have added 0.1% of lithium difluorophosphate additive to Kim’s electrolyte to further improve the cycle property of the battery.
Claim 14: Kim teaches a lithium secondary battery comprising a positive electrode, a negative electrode and an electrolyte [0026],
wherein the positive electrode includes a positive electrode current collector and a positive electrode layer formed on at least one surface of the positive electrode current collector. The negative electrode includes a negative electrode current collector and a negative electrode layer formed on at least one surface of the negative electrode current collector [0033],
wherein positive electrode material may contain compounds represented by the formular LixFePO4 wherein (0.5<x<1.3) [0036], which includes LiFePO4.
Claim 15: Kim teaches a vehicle comprising lithium secondary batteries [0006].
Claim 20 is rejected under 35 U.S.C. 103 as being unpatentable over Kim et al. (US 20180309161 A1), Uematsu (EP 3038201 A1), Kato et al. (JP 6738721 B2) and Liang et al. (US 20220149437 A1), and further in view of Barron et al. (TSP-07 Issue 3, 2005)
Claim 20: Kim teaches the viscosity is measured at room temperature (25 ̊C) [0043]. Kim does not explicitly teach the ion conductivity was measured at 25 ̊C. However, Kim teaches that the ionic conductivity can be measured using conventional methods [0032].
Barron teaches that in order to allow comparison of conductivity measurements, most conductivity measurements are referenced to 25 ̊C (page 1 para 6), and the refence temperature in commonly used procedures is 25 ̊C ( see table 2). Therefore, it would have been obvious to one of ordinary skill in the art at the time of filing the instant invention to have measure the ion conductivity of Kim’s electrolyte at 25 ̊C for more accurate comparison to other ion conductivity measurements because it is the conventional reference temperature.
Conclusion
The prior art made of record and not relied upon is considered pertinent to applicant's disclosure. Zhamu et al. (US 20180342737 A1) teaches an electrolyte comprising ethylene carbonate and methyl ethyl carbonate [0155-0156] with ion conductivity of 10.4 S/cm [0010], and a graphite negative electrode [0163] with a packing density of 1.2 g/cm3 [0081].
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/L.N.R./Examiner, Art Unit 1712
/MICHAEL B CLEVELAND/Supervisory Patent Examiner, Art Unit 1712
