A lithium-ion battery

Abstract

The application belongs to the technical field of batteries, and particularly relates to a lithium ion battery, which comprises a manganese-based positive electrode, a phosphorus-carbon negative electrode, an electrolyte and a diaphragm between the manganese-based positive electrode and the phosphorus-carbon negative electrode; the manganese-based positive electrode comprises a positive electrode current collector and a positive electrode active material layer arranged on the surface of the positive electrode current collector; the components of the positive electrode active material layer comprise a positive electrode active substance, a positive electrode conductive agent and a positive electrode binder; the positive electrode active substance is lithium manganate and / or lithium nickel manganate; the components of the electrolyte comprise a lithium salt, a high-voltage-resistant additive and an organic solvent; the high-voltage-resistant additive is one or more of fluorocarbonate, difluoroethylene carbonate, methyl trifluoroethyl carbonate, methyl cyanoacetate and trimethyl phosphate; and the components of the organic solvent comprise propylene carbonate and linear carbonate. The lithium ion battery provided by the application has good cycle performance at high voltage.

Description

Technical Field

[0001] This invention belongs to the field of battery technology, and particularly relates to a lithium-ion battery. Background Technology

[0002] With the large-scale application of lithium-ion batteries, the raw material costs of mainstream lithium-ion batteries based on lithium cobalt oxide and lithium nickel cobalt manganese oxide ternary cathode materials are constantly rising, mainly due to the continuous increase in the price of cobalt resources, with battery costs reaching $50,000 / kWh. Therefore, developing new cobalt-free lithium-ion battery systems is key to further reducing battery costs and increasing the scale of battery applications.

[0003] In recent years, high-voltage manganese-based cathode materials have attracted widespread attention due to their inexpensive raw material prices and high discharge voltage. Lithium-ion batteries based on this cathode material can reduce costs to below $8,000 / kWh, showing excellent application prospects. However, currently commercially available lithium-ion batteries using manganese-based cathode materials generally suffer from poor cycle performance under high-voltage conditions. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a lithium-ion battery that has good cycle performance at high voltage.

[0005] This invention provides a lithium-ion battery, comprising: a manganese-based positive electrode, a phosphorus-carbon negative electrode, an electrolyte, and a separator between the manganese-based positive electrode and the phosphorus-carbon negative electrode;

[0006] The manganese-based positive electrode includes a positive electrode current collector and a positive electrode active material layer disposed on the surface of the positive electrode current collector; the positive electrode active material layer comprises a positive electrode active material, a positive electrode conductive agent, and a positive electrode binder; the positive electrode active material is lithium manganese oxide and / or lithium nickel manganese oxide;

[0007] The electrolyte comprises lithium salt, high-voltage resistant additives, and organic solvents; the high-voltage resistant additives are one or more of fluorocarbonate, difluoroethylene carbonate, methyl trifluoroethyl carbonate, methyl cyanoacetate, and trimethyl phosphate; the organic solvents comprise propylene carbonate and linear carbonate.

[0008] Preferably, the phosphorus-carbon anode includes a negative electrode current collector and a negative electrode active material layer disposed on the surface of the negative electrode current collector; the negative electrode active material layer comprises a negative electrode active substance, a negative electrode conductive agent and a negative electrode binder; the negative electrode active substance is a phosphorus-carbon composite material.

[0009] Preferably, the phosphorus in the phosphorus-carbon composite material is one or more of red phosphorus, black phosphorus, purple phosphorus, yellow phosphorus, orange phosphorus, green phosphorus, and blue phosphorus.

[0010] Preferably, the phosphorus content in the phosphorus-carbon composite material is 10–90 wt%.

[0011] Preferably, the carbon in the phosphorus-carbon composite material is graphite or C. 60 C 70 One or more of carbon nanotubes and conductive carbon black.

[0012] Preferably, the carbon in the phosphorus-carbon composite material is carbon nanotubes and conductive carbon black; the mass ratio of the carbon nanotubes to the conductive carbon black is 1:(2-5).

[0013] Preferably, the content of the high-voltage resistant additive in the electrolyte is 0.1-8 wt%.

[0014] Preferably, the linear carbonate is one or more of diethyl carbonate, dimethyl carbonate, and ethyl methyl carbonate.

[0015] Preferably, the volume ratio of propylene carbonate to linear carbonate is 1:(1-3).

[0016] Preferably, the lithium salt is one or more selected from lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium perchlorate, and lithium bis(trifluoromethanesulfonyl)imide.

[0017] Compared with the prior art, the present invention provides a lithium-ion battery, comprising: a manganese-based positive electrode, a phosphorus-carbon negative electrode, an electrolyte, and a separator between the manganese-based positive electrode and the phosphorus-carbon negative electrode; the manganese-based positive electrode includes a positive electrode current collector and a positive electrode active material layer disposed on the surface of the positive electrode current collector; the positive electrode active material layer comprises a positive electrode active material, a positive electrode conductive agent, and a positive electrode binder; the positive electrode active material is lithium manganese oxide and / or lithium nickel manganese oxide; the electrolyte comprises a lithium salt, a high-voltage resistant additive, and an organic solvent; the high-voltage resistant additive is one or more selected from fluorocarbonate, ethylene difluorocarbonate, methyl trifluoroethyl carbonate, methyl cyanoacetate, and trimethyl phosphate; the organic solvent comprises propylene carbonate and linear carbonate. This invention uses a mixed solvent of propylene carbonate (PC) and linear carbonate as the electrolyte solvent, supplemented with a certain amount of high-voltage resistant additives, to improve the high-voltage resistance of the electrolyte and effectively avoid battery failure caused by solvent decomposition due to high voltage. Furthermore, by selecting manganese-based positive electrode and phosphorus-carbon negative electrode suitable for the PC-based mixed electrolyte, the cycle performance of the lithium-ion battery under high voltage is significantly improved. Experimental results show that the lithium-ion battery provided by this invention can cycle stably within the charge-discharge voltage range of 2.7–4.7V, and the capacity retention rate can reach 80% after 200 cycles. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0019] Figure 1 This is a charge-discharge curve of the lithium-ion battery provided in Embodiment 2 of the present invention at 25°C. Detailed Implementation

[0020] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] The present invention provides a lithium-ion battery, characterized in that it comprises: a manganese-based positive electrode, a phosphorus-carbon negative electrode, an electrolyte, and a separator between the manganese-based positive electrode and the phosphorus-carbon negative electrode.

[0022] In this invention, the manganese-based positive electrode includes a positive electrode current collector and a positive electrode active material layer disposed on the surface of the positive electrode current collector; the positive electrode current collector is preferably a carbon aluminum foil; the positive electrode active material layer comprises a positive electrode active material, a positive electrode conductive agent, and a positive electrode binder; the positive electrode active material is lithium manganese oxide and / or lithium nickel manganese oxide; the positive electrode conductive agent is preferably conductive carbon SP (SuperP carbon); the positive electrode binder is preferably polyvinylidene fluoride; the mass ratio of the positive electrode active material, conductive agent, and binder is preferably 9:(0.2-1):(0.2-1), more preferably 9:0.5:0.5.

[0023] In this invention, the manganese-based positive electrode can be prepared as follows: a positive electrode active material, a positive electrode conductive agent, a positive electrode binder, and a solvent are mixed to obtain a positive electrode active slurry; the positive electrode active slurry is coated onto a positive electrode current collector and dried to obtain a manganese-based positive electrode. The solvent includes, but is not limited to, N-methylpyrrolidone; the drying method is preferably vacuum drying; the drying temperature is preferably 40–80°C, more preferably 60°C; and the drying time is preferably 8–16 hours, more preferably 12 hours.

[0024] In this invention, the phosphorus-carbon negative electrode preferably comprises a negative electrode current collector and a negative electrode active material layer disposed on the surface of the negative electrode current collector; the negative electrode current collector is preferably a carbon-copper foil; the composition of the negative electrode active material layer preferably includes a negative electrode active substance, a negative electrode conductive agent, and a negative electrode binder; the negative electrode active substance is preferably a phosphorus-carbon composite material, the specific components of which include phosphorus and carbon; the phosphorus is preferably one or more of red phosphorus, black phosphorus, purple phosphorus, yellow phosphorus, orange phosphorus, green phosphorus, and blue phosphorus; the carbon is preferably graphite, C 60 C 70 The carbon is selected from one or more of carbon nanotubes and conductive carbon black, wherein the conductive carbon black is preferably Ketjen black; the carbon is more preferably carbon nanotubes and conductive carbon black, and the mass ratio of the carbon nanotubes and conductive carbon black is preferably 1:(2-5), more preferably 1:3; the phosphorus content in the phosphorus-carbon composite material is preferably 10-90 wt%, specifically 10 wt%, 20 wt%, 30 wt%, 40 wt%, 50 wt%, 60 wt%, 70 wt%, 80 wt% or 90 wt%.

[0025] In this invention, the phosphorus-carbon composite material can be prepared by mechanically vibrating phosphorus and carbon under a protective gas atmosphere to obtain the phosphorus-carbon composite material. The protective gas is preferably argon; the mechanical vibration is preferably performed by alternating vibration at a first frequency and a second frequency; the first frequency is preferably 20–40 Hz, more preferably 30 Hz; the second frequency is preferably 0–10 Hz, more preferably 0 Hz; the single vibration time at the first frequency is preferably 15–30 min, more preferably 25 min; the single vibration time at the second frequency is preferably 5–15 min, more preferably 10 min; and the number of alternating vibration cycles is preferably 15–40 times, more preferably 28 times.

[0026] In this invention, in the negative electrode active material layer of the phosphorus-carbon negative electrode, the negative electrode conductive agent is preferably conductive carbon black, more preferably Ketjen black; the negative electrode binder is preferably polyvinylidene fluoride; the mass ratio of the negative electrode active material, the negative electrode conductive agent and the negative electrode binder is preferably 8:(0.5~2):(0.5~2), more preferably 8:1:1.

[0027] In this invention, the phosphorus-carbon anode can be prepared as follows: an anode active material, anode conductive agent, anode binder, and solvent are mixed to obtain an anode active slurry; the anode active slurry is coated onto a cathode current collector and dried to obtain the phosphorus-carbon anode. The solvent includes, but is not limited to, N-methylpyrrolidone; the drying method is preferably vacuum drying; the drying temperature is preferably 40–80°C, more preferably 60°C; and the drying time is preferably 8–16 hours, more preferably 12 hours.

[0028] In this invention, the electrolyte comprises a lithium salt, a high-voltage resistant additive, and an organic solvent. The lithium salt is preferably one or more of lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium perchlorate, and lithium bis(trifluoromethanesulfonyl)imide. The concentration of the lithium salt in the electrolyte is preferably 0.8–1.5 mol / L, specifically 0.8 mol / L, 0.9 mol / L, 1.0 mol / L, 1.1 mol / L, 1.2 mol / L, 1.3 mol / L, 1.4 mol / L, or 1.5 mol / L.

[0029] In this invention, the high-voltage resistant additive in the electrolyte is one or more selected from fluorocarbonate (FEC), ethylene difluorocarbonate (DFEC), methyl trifluoroethyl carbonate (TFEMC), methyl cyanoacetate (MCA), and trimethyl phosphate (TMP). The content of the high-voltage resistant additive in the electrolyte is preferably 0.1–8 wt%, specifically 0.1 wt%, 0.3 wt%, 0.5 wt%, 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, 5 wt%, 5.5 wt%, 6 wt%, 6.5 wt%, 7 wt%, 7.5 wt%, or 8 wt%.

[0030] In this invention, the electrolyte contains an organic solvent comprising propylene carbonate (PC) and linear carbonate; the linear carbonate is preferably one or more of diethyl carbonate (DEC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC), more preferably diethyl carbonate and ethyl methyl carbonate, and the volume ratio of diethyl carbonate to ethyl methyl carbonate is preferably 1:(0.5-2), specifically 1:0.5, 1:0.7, 1:1, 1:1.2, 1:1.5, 1:1.7, or 1:2; the volume ratio of propylene carbonate to linear carbonate is preferably 1:(1-3), specifically 1:1, 1:1.2, 1:1.5, 1:1.7, 1:2, 1:2.3, 1:2.5, 1:2.7, or 1:3.

[0031] In this invention, the membrane is preferably made of polypropylene (PP).

[0032] The technical solution provided by this invention uses a mixed solvent of propylene carbonate (PC) and linear carbonate as the electrolyte solvent, supplemented by a certain amount of high-voltage resistant additives, which improves the high-voltage resistance of the electrolyte and effectively avoids battery failure caused by solvent decomposition due to high voltage. Furthermore, by selecting manganese-based cathodes and phosphorus-carbon anodes suitable for the PC-based mixed electrolyte, the cycle performance of the lithium-ion battery under high voltage is significantly improved. Experimental results show that the lithium-ion battery provided by this invention can reach a charging voltage of 4.7V, a cell energy density of 340Wh / kg, and retains 80% of its capacity after 200 cycles at a 0.1C current density. In addition, this lithium-ion battery also exhibits good low-temperature performance, with a discharge specific capacity at -20℃ and a 0.1C rate reaching 80% of that at room temperature (25℃).

[0033] For clarity, the following examples will be used to provide a detailed description.

[0034] Example 1

[0035] Red phosphorus (CAS:7723-14-0, Aladdin) and carbon nanotubes (CAS:308068-56-6, Aladdin) were pre-ground in an agate mortar and then mixed with Ketjen black (ECP-600JD, Canrd) at a mass ratio of 6:3:1 (phosphorus: Ketjen black: carbon nanotubes) under an argon-filled atmosphere and mechanically vibrated at a frequency of 30Hz / 0Hz for 25min / 10min, for 28 cycles, to obtain a phosphorus-carbon composite material powder sample.

[0036] The powder sample was ground uniformly with conductive carbon black (Ketjen black) and polyvinylidene fluoride (PVDF) at a mass ratio of 8:1:1. Then, N-methylpyrrolidone (NMP) was added as a solvent to form a uniform black paste. The paste was then uniformly coated onto carbon-coated copper foil and dried under vacuum at 60°C for 12 hours to obtain the negative electrode sheet.

[0037] Example 2

[0038] Commercially available lithium nickel manganese oxide (LNMO) powder was ground uniformly with conductive carbon SP (SuperP carbon) and polyvinylidene fluoride (PVDF) at a mass ratio of 9:0.5:0.5. Then, N-methylpyrrolidone (NMP) was added as a solvent to form a uniform black paste. The paste was then uniformly coated onto carbon-coated aluminum foil and vacuum dried at 60°C for 12 hours to obtain the positive electrode sheet.

[0039] The electrode sheet prepared above was used as the positive electrode, and the electrode sheet prepared in Example 1 was used as the negative electrode. The electrolyte composition was: 1 mol / L lithium hexafluorophosphate (LiPF6), 5 wt% DFEC, and the balance organic solvent PC:EMC:DEC = 1:1:1 (volume ratio). PP (polypropylene) was used as the separator. Standard coin cell CR2032 was assembled and tested. The charge / discharge voltage range was 2.7V to 4.7V. Charge / discharge cycles were performed at a discharge current density of 0.1C and at 25℃, -10℃, and -20℃. The charge / discharge curve at 25℃ is shown below. Figure 1 As shown in Tables 1 and 2, the specific test results are as follows.

[0040] Comparative Example 1

[0041] Commercially available lithium cobalt oxide (LCO) powder was ground uniformly with conductive carbon SP (SuperP carbon) and polyvinylidene fluoride (PVDF) at a mass ratio of 9:0.5:0.5. Then, N-methylpyrrolidone (NMP) was added as a solvent to form a uniform black paste. The paste was then uniformly coated onto carbon-coated aluminum foil and dried under vacuum at 60°C for 12 hours to obtain the positive electrode sheet.

[0042] The electrode sheet prepared above was used as the positive electrode, and the electrode sheet prepared in Example 1 was used as the negative electrode. The electrolyte composition was: 1 mol / L lithium hexafluorophosphate (LiPF6), 5 wt% DFEC, and the balance organic solvent PC:EMC:DEC = 1:1:1 (volume ratio). PP (polypropylene) was used as the separator, and a standard coin cell CR2032 was assembled for testing. The charge and discharge voltage range was 2.7V to 4.7V. Charge and discharge cycles were performed at a discharge current density of 0.1C and 25°C. The test results are shown in Table 1.

[0043] Comparative Example 2

[0044] Commercially available nickel-cobalt-manganese ternary material (NCM523) powder was ground uniformly with conductive carbon SP (Super Pcarbon) and polyvinylidene fluoride (PVDF) at a mass ratio of 9:0.5:0.5. Then, N-methylpyrrolidone (NMP) was added as a solvent to form a uniform black paste. The paste was then uniformly coated onto carbon-coated aluminum foil and dried under vacuum at 60°C for 12 hours to obtain the positive electrode sheet.

[0045] The electrode sheet prepared above was used as the positive electrode, and the electrode sheet prepared in Example 1 was used as the negative electrode. The electrolyte composition was: 1 mol / L lithium hexafluorophosphate (LiPF6), 5 wt% DFEC, and the balance organic solvent PC:EMC:DEC = 1:1:1 (volume ratio). PP (polypropylene) was used as the separator, and a standard coin cell CR2032 was assembled for testing. The charge and discharge voltage range was 2.7V to 4.7V. Charge and discharge cycles were performed at a discharge current density of 0.1C and 25°C. The test results are shown in Table 1.

[0046] Comparative Example 3

[0047] Commercially available lithium nickel manganese oxide (LNMO) powder was ground uniformly with conductive carbon SP (Super P carbon) and polyvinylidene fluoride (PVDF) at a mass ratio of 9:0.5:0.5. Then, N-methylpyrrolidone (NMP) was added as a solvent to form a uniform black paste. The paste was then uniformly coated onto carbon-coated aluminum foil and dried under vacuum at 60°C for 12 hours to obtain the positive electrode sheet.

[0048] The electrode sheet prepared above was used as the positive electrode, and the electrode sheet prepared in Example 1 was used as the negative electrode. The electrolyte composition was: 1 mol / L lithium hexafluorophosphate (LiPF6), and the balance organic solvent EC:EMC:DEC = 1:1:1 (volume ratio, EC refers to ethylene carbonate). PP (polypropylene) was used as the separator, and standard coin cell CR2032 was assembled for testing. The charge and discharge voltage range was 2.7V to 4.7V. Charge and discharge cycles were performed at a discharge current density of 0.1C and at 25℃, -10℃, and -20℃. The test results are shown in Table 2.

[0049] Table 1. Electrochemical data test results of the material at room temperature (25℃)

[0050]

[0051] Table 2. Electrochemical data test results of the materials at room temperature (25℃) and low temperatures (-20℃, -10℃).

[0052]

[0053] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A lithium-ion battery, characterized in that, include: Manganese-based positive electrode, phosphorus-carbon negative electrode, electrolyte, and a separator between the manganese-based positive electrode and the phosphorus-carbon negative electrode; The manganese-based positive electrode includes a positive electrode current collector and a positive electrode active material layer disposed on the surface of the positive electrode current collector; the positive electrode active material layer comprises a positive electrode active material, a positive electrode conductive agent, and a positive electrode binder; the positive electrode active material is lithium manganese oxide and / or lithium nickel manganese oxide; The electrolyte comprises lithium salt, high-voltage resistant additives, and organic solvents; the high-voltage resistant additives are one or more of fluorocarbonate, difluoroethylene carbonate, methyl trifluoroethyl carbonate, methyl cyanoacetate, and trimethyl phosphate; the organic solvents comprise propylene carbonate and linear carbonate.

2. The lithium-ion battery according to claim 1, characterized in that, The phosphorus-carbon anode includes an anode current collector and an anode active material layer disposed on the surface of the anode current collector; the anode active material layer comprises an anode active substance, an anode conductive agent, and an anode binder; the anode active substance is a phosphorus-carbon composite material.

3. The lithium-ion battery according to claim 2, characterized in that, The phosphorus in the phosphorus-carbon composite material is one or more of red phosphorus, black phosphorus, purple phosphorus, yellow phosphorus, orange phosphorus, green phosphorus, and blue phosphorus.

4. The lithium-ion battery according to claim 2, characterized in that, The phosphorus content in the phosphorus-carbon composite material is 10–90 wt%.

5. The lithium-ion battery according to claim 2, characterized in that, The carbon in the phosphorus-carbon composite material is graphite and C. 60 C 70 One or more of carbon nanotubes and conductive carbon black.

6. The lithium-ion battery according to claim 5, characterized in that, The carbon in the phosphorus-carbon composite material consists of carbon nanotubes and conductive carbon black; the mass ratio of the carbon nanotubes to the conductive carbon black is 1:(2-5).

7. The lithium-ion battery according to claim 1, characterized in that, The high-voltage resistant additive has a content of 0.1–8 wt% in the electrolyte.

8. The lithium-ion battery according to claim 1, characterized in that, The linear carbonate is one or more of diethyl carbonate, dimethyl carbonate, and methyl ethyl carbonate.

9. The lithium-ion battery according to claim 1, characterized in that, The volume ratio of propylene carbonate to linear carbonate is 1:(1-3).

10. The lithium-ion battery according to claim 1, characterized in that, The lithium salt is one or more of lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium perchlorate, and lithium bis(trifluoromethanesulfonyl)imide.

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