CN102332604A - A high-power lithium-ion battery - Google Patents

Abstract

The invention relates to the field of lithium ion batteries, in particular to a high-power lithium ion battery using amorphous carbon as an anode material, which comprises a positive electrode using a transition metal lithium-intercalated oxide, a negative electrode using amorphous carbon as an anode material, a diaphragm, electrolyte and an outer package, wherein the amorphous carbon material is characterized in that: the graphite microcrystal has an interlayer spacing D (002) of 0.340-0.385 nm, a stacking thickness of 1.2-4.8 nm, a D50 of 5-15 μm, and a specific surface area of 0.5-5 m²(iv) g, tap density of 0.7-1.2 g/cm³. The battery has high power density, the power density (50% SOC) of HPPC at normal temperature can reach 4700W/kg, and the battery is suitable for high-power application occasions.

Description

A high-power lithium-ion battery

technical field

The invention relates to the field of lithium-ion batteries, in particular to high-power lithium-ion batteries using amorphous carbon as an anode material.

Background technique

Compared with lead-acid batteries, nickel-metal hydride batteries, and nickel-cadmium batteries, lithium-ion batteries have the advantages of higher energy density, small self-discharge, and long cycle life, and have been widely used in the field of consumer electronics.

Many applications, such as HEV, require a large starting current when the vehicle is started, and energy needs to be recovered in a short time when braking, and the requirements for the battery are high power. From a structural point of view, a lithium-ion battery includes a positive electrode, a negative electrode, a separator, an electrolyte, and an outer packaging. Its working principle is that when charging, electrons flow from the positive electrode material through the external circuit and enter the negative electrode. Lithium ions first diffuse from the inside of the positive electrode material particles to the surface of the particles, and then electromigrate to the surface of the negative electrode material in the liquid electrolyte, passing through the SEI film. Diffusion inside the negative electrode material particles; when discharging, it is a reverse process. The diffusion of lithium ions inside the electrode material particles is the rate-limiting step in this process. Commonly used cathode materials include lithium cobaltate, lithium manganate, lithium iron phosphate, ternary materials, etc. Lithium cobalt oxide has a two-dimensional layered structure, and the cobalt-oxygen layer spacing is about 0.7nm. LiMn ₂ O ₄ has a cubic spinel structure with three-dimensional lithium ion channels. The interlayer spacing of the graphite material most commonly used in lithium-ion batteries is 0.338nm. It can be seen from this that the graphite anode material is the rate-limiting step for lithium ion transport.

Lithium titanate and its composite materials are currently the most researched anode materials for high-power lithium-ion batteries. Chinese patents with application numbers 200610014789.1, 200810230097.X, 201010127600.6, 201010184114.8, 201020135554.X use lithium titanate or lithium titanate/carbon composite material as the negative electrode to make high-power lithium ion batteries. However, the plateau potential of lithium titanate is 1.5V vs. Li ⁺ /Li, the plateau voltage of the full battery is about 2.3V, and the energy density is low. In addition, assembling into Pack groups during application will increase the number of series cells, which will increase the complexity of assembly and the cost of the balancing circuit.

For lithium-ion batteries using amorphous carbon materials as anodes, patents with application numbers 96114275.8 and 96114133.6 use amorphous carbon as anodes to prepare lithium-ion batteries, and the reversible lithium storage capacity of the carbon materials has reached 536mAh/g. The anode potential is very close to the lithium analysis potential. When charging at a higher rate, it is easy to release lithium. There is a huge safety hazard for the application of high-power lithium-ion batteries, so it cannot be used as a high-power lithium-ion battery.

Contents of the invention

The object of the present invention is to provide a high-power lithium-ion battery using amorphous carbon as an anode material to address the deficiencies of the prior art.

In order to achieve the above object, the present invention adopts the following technical solutions:

A high-power lithium-ion battery, which includes a positive electrode of a transition metal lithium intercalation oxide, an amorphous carbon negative electrode as an anode material, a diaphragm, an electrolyte and an outer package, and the graphite sheet of the graphite microcrystal cluster of the amorphous carbon The stack thickness of the layers is 1.2-4.8nm.

Compared with the prior art, the present invention uses amorphous carbon as an anode material to prepare a high-power lithium ion battery. Among them, the characteristic of amorphous carbon material is that the stacking thickness of graphite sheets is 1.2-4.8nm. The size of graphite crystallite clusters of this amorphous carbon material is small, and a large number of transmission channels for lithium ions are provided between the clusters, which is beneficial to lithium ions. Diffusion inside the amorphous carbon, when charged at a higher rate, the polarization is small, and it is not easy to separate lithium, which greatly improves the safety of high-power lithium-ion battery applications, and the interlayer distance of microcrystals is relatively large (0.35 ~ 0.38nm ), which is also conducive to the diffusion of lithium ions inside the amorphous carbon, so that lithium-ion batteries can be applied to high-rate, high-power occasions.

As an improvement of the high-power lithium-ion battery of the present invention, the stacking thickness of the graphite sheets is 2-4.6nm, and the stacking thickness enables the present invention to have good comprehensive performance, especially higher power density.

As an improvement of the high-power lithium-ion battery of the present invention, the stack thickness of the graphite sheets is 3.72nm.

As an improvement of the high-power lithium-ion battery of the present invention, the interlayer spacing d(002) of the graphite crystallites of the amorphous carbon is 0.340 to 0.385nm, and the interlayer spacing of the microcrystals is relatively large, which is beneficial to lithium ions in the amorphous carbon. The internal diffusion, so the factor that has a greater impact on the transmission of lithium ions (the diffusion of lithium ions inside the amorphous carbon particles) is improved, so that lithium-ion batteries can be applied to high-rate, high-power occasions.

As an improvement of the high-power lithium-ion battery of the present invention, the interlayer distance d(002) of the graphite microcrystal is 0.35-0.38 nm.

As an improvement of the high-power lithium-ion battery of the present invention, the D50 of the amorphous carbon is 5-15 μm, if it is greater than 15 μm, it will affect the transmission speed of lithium ions from the electrolyte body to the interior of the amorphous carbon particles, and if it is less than 5 μm, it will be due to The larger the specific surface, the more contact with the electrolyte, and the occurrence of side reactions, making the performance worse. The D50 refers to the corresponding particle size when the cumulative particle size distribution percentage of a sample reaches 50%. Its physical meaning is that the particles with a particle size larger than it account for 50%, and the particles smaller than it also account for 50%. D50 is also called the median diameter or median particle diameter.

As an improvement of the high-power lithium-ion battery of the present invention, the specific surface area of the amorphous carbon is 0.5-5m ² /g, and if it is greater than 5m ² /g, it will have more contact with the electrolyte, and side reactions will occur, making the performance change. Difference. If it is less than 0.5m ² /g, the transfer rate of lithium ions from the body of the electrolyte to the interior of the amorphous carbon particles will be affected.

As an improvement of the high-power lithium-ion battery of the present invention, the specific surface area of the amorphous carbon is 3-4 m ² /g.

As an improvement of the high-power lithium-ion battery of the present invention, the tap density of the amorphous carbon is 0.7-1.2 g/cm ³ , and the size of the graphite crystallite clusters of the amorphous carbon material affects the density of lithium ions between the clusters. The number of transmission channels, using this tap density can reasonably confirm the size of graphite crystallite clusters.

As an improvement of the high-power lithium-ion battery of the present invention, the negative electrode includes a current collector, amorphous carbon attached to the current collector, a conductive agent and a binder, wherein the conductive agent is Super P (conductive carbon) or conductive Carbon black, the binder is PVDF (polyvinylidene fluoride), SBR (styrene-butadiene rubber) or CMC (sodium carboxymethyl cellulose), amorphous carbon: conductive agent: binder is 85-95: 10-2 : 5~3.

Detailed ways

The present invention and its beneficial effects will be further described in detail below in conjunction with examples, but the embodiments of the present invention are not limited thereto.

Example 1:

Coat the anode slurry (amorphous carbon: Super P: PVDF = 92:3:5, solvent is NMP) on the 9 μm copper foil, the coating weight is 4.5mg/cm ² , after passing through the oven of the coating machine to obtain The pole piece after drying, wherein the parameters of the amorphous carbon used are that the interlayer spacing d(002) of graphite crystallites is 0.349nm, the stacking thickness of graphite flakes is 4.54nm, D50 is 12.4μm, and the specific surface area is 3.39m ² /g, the tap density is 0.86g/cm ³ .

Coat cathode slurry (lithium manganate: conductive carbon: PVDF=94:4:2, solvent is NMP) on a 16 μm aluminum foil, the coating weight is 11.0 mg/cm ² , and it is dried after passing through the oven of the coating machine Pole piece after.

Then the pole pieces are cold-pressed respectively, and then the pole pieces are dried twice in a high-temperature oven, and then the pole pieces to be wound are prepared by slitting and cutting in turn. The pole piece is wound, and then a 1Ah lithium-ion battery is prepared through processes such as packaging and liquid injection. The HPPC power density (50% SOC) at room temperature is 4735W/kg, its energy density is 80Wh/kg, and its capacity retention rate is 87% after 3000 cycles of 5C/5C cycle at room temperature.

As a comparative lithium-ion battery, its anode uses graphite, and the HPPC power density (50% SOC) at normal temperature is 2200W/kg. Through this comparison, it can be seen that the lithium-ion battery using amorphous carbon as the anode described in this example has a high power density and is suitable for high-power applications.

Example 2:

Coat the anode slurry (amorphous carbon: Super P: PVDF = 92:3:5, solvent is NMP) on the 9 μm copper foil, the coating weight is 4.5mg/cm ² , after passing through the oven of the coating machine to obtain The pole piece after drying, wherein the parameters of the amorphous carbon used are that the interlayer spacing d(002) of graphite crystallites is 0.354nm, the stacking thickness of graphite flakes is 3.72nm, D50 is 14.1μm, and the specific surface area is 1.65m ² /g, and the tap density is 0.77g/cm ³ .

Coat cathode slurry (lithium manganate: conductive carbon: PVDF=94:4:2, solvent is NMP) on a 16 μm aluminum foil, the coating weight is 11.0 mg/cm ² , after passing through the oven of the coating machine, it is dried Pole piece after.

Then the pole pieces are cold-pressed respectively, and then the pole pieces are dried twice in a high-temperature oven, and then the pole pieces to be wound are prepared by slitting and cutting in turn. The pole piece is wound, and then a 1Ah lithium-ion battery is prepared through processes such as packaging and liquid injection. The HPPC power density (50% SOC) at room temperature is 4018W/kg, its energy density is 80Wh/kg, and its capacity retention rate is 76% after 3000 cycles of 5C/5C cycle at room temperature.

As a comparative lithium-ion battery, its anode uses graphite, and the HPPC power density (50% SOC) at normal temperature is 2200W/kg. Through this comparison, it can be seen that the lithium-ion battery using amorphous carbon as the anode described in this example has a high power density and is suitable for high-power applications.

Example 3:

Coating anode slurry (amorphous carbon: Super P: CMC: SBR = 93: 3: 2: 2, solvent is deionized water) on a 9 μm copper foil, the coating weight is 4.5 mg/cm ² , after coating The dried pole piece is obtained after the oven of the cloth machine. The parameters of the amorphous carbon used are that the interlayer spacing d(002) of graphite crystallites is 0.349nm, the stacking thickness of graphite flakes is 4.54nm, and D50 is 11.4μm , the specific surface area is 4.71m ² /g, and the tap density is 0.89g/cm ³ .

Coat cathode slurry (lithium manganate: conductive carbon: PVDF=94:4:2, solvent is NMP) on a 16 μm aluminum foil, the coating weight is 11.0 mg/cm ² , and it is dried after passing through the oven of the coating machine Pole piece after.

Then the pole pieces are cold-pressed respectively, and then the pole pieces are dried twice in a high-temperature oven, and then the pole pieces to be wound are prepared by slitting and cutting in turn. The pole piece is wound, and then a 1Ah lithium-ion battery is prepared through processes such as packaging and liquid injection. The power density (50% SOC) of HPPC at room temperature is 3516W/kg, its energy density is 78Wh/kg, and its capacity retention rate is 85% after 3000 cycles of 5C/5C cycle at room temperature.

As a comparative lithium-ion battery, its anode uses graphite, and the HPPC power density (50% SOC) at normal temperature is 2200W/kg. Through this comparison, it can be seen that the lithium-ion battery using amorphous carbon as the anode described in this example has a high power density and is suitable for high-power applications.

Example 4:

Coat the anode slurry (amorphous carbon: SuperP: PVDF=94:3:3, the solvent is NMP) on the copper foil of 9 μm, the coating weight is 4.4mg/cm ² , and it is dried after passing through the oven of the coating machine The final pole piece, wherein the parameters of the amorphous carbon used are that the interlayer spacing d(002) of graphite crystallites is 0.379nm, the stacking thickness of graphite sheets is 1.23nm, D50 is 10.1μm, and the specific surface area is 0.74m ² /g, and the tap density is 0.91g/cm ³ .

Coat cathode slurry (lithium manganate: conductive carbon: PVDF=94:4:2, solvent is NMP) on a 16 μm aluminum foil, the coating weight is 11.0 mg/cm ² , after passing through the oven of the coating machine, it is dried Pole piece after.

Then the pole pieces are cold-pressed respectively, and then the pole pieces are dried twice in a high-temperature oven, and then the pole pieces to be wound are prepared by slitting and cutting in turn. The pole piece is wound, and then a 1Ah lithium-ion battery is prepared through processes such as packaging and liquid injection. The power density (50% SOC) of HPPC at room temperature is 3096W/kg, its energy density is 69Wh/kg, and its capacity retention rate is 71% after 3000 cycles of 5C/5C cycle at room temperature.

As a comparative lithium-ion battery, its anode uses graphite, and the HPPC power density (50% SOC) at normal temperature is 2200W/kg. Through this comparison, it can be seen that the lithium-ion battery using amorphous carbon as the anode described in this example has a high power density and is suitable for high-power applications.

Example 5:

Coat the anode slurry (amorphous carbon: SuperP: PVDF = 86:9:5, the solvent is NMP) on the copper foil of 9 μm, the coating weight is 4.8 mg/cm ² , and it is dried after passing through the oven of the coating machine The final pole piece, wherein the parameters of the amorphous carbon used are that the interlayer spacing d(002) of graphite crystallites is 0.356nm, the stacking thickness of graphite sheets is 2.15nm, D50 is 6.5μm, and the specific surface area is 1.84m ² /g, the tap density is 1.13g/cm ³ .

Coat cathode slurry (lithium manganate: conductive carbon: PVDF=94:4:2, solvent is NMP) on a 16 μm aluminum foil, the coating weight is 11.0 mg/cm ² , after passing through the oven of the coating machine, it is dried Pole piece after.

Then the pole pieces are cold-pressed respectively, and then the pole pieces are dried twice in a high-temperature oven, and then the pole pieces to be wound are prepared by slitting and cutting in turn. The pole piece is wound, and then a 1Ah lithium-ion battery is prepared through processes such as packaging and liquid injection. The HPPC power density (50% SOC) at room temperature is 3968W/kg, its energy density is 82Wh/kg, and its capacity retention rate is 72% after 3000 cycles of 5C/5C cycle at room temperature.

As a comparative lithium-ion battery, its anode uses graphite, and the HPPC power density (50% SOC) at normal temperature is 2200W/kg. Through this comparison, it can be seen that the lithium-ion battery using amorphous carbon as the anode described in this example has a high power density and is suitable for high-power applications.

According to the disclosure and teaching of the above-mentioned specification, those skilled in the art to which the present invention belongs can also make changes and modifications to the above-mentioned embodiment. Therefore, the present invention is not limited to the specific embodiments disclosed and described above, and some modifications and changes to the present invention should also fall within the protection scope of the claims of the present invention. In addition, although some specific terms are used in this specification, these terms are only for convenience of description and do not constitute any limitation to the present invention.

Claims (10)

1. A high-power lithium-ion battery, comprising a positive electrode using transition metal lithium intercalation oxides, a negative electrode using amorphous carbon as an anode material, a diaphragm and an electrolyte, characterized in that: the graphite crystallite of the amorphous carbon The stacking thickness of the graphite flakes of the cluster is 1.2-4.8nm. 2. A high-power lithium-ion battery according to claim 1, characterized in that: the stack thickness of the graphite sheets is 2-4.6 nm. 3. A high-power lithium-ion battery according to claim 2, characterized in that: the stack thickness of the graphite sheets is 3.72nm. 4. A high-power lithium-ion battery according to claim 1, characterized in that: the interlayer distance d(002) of the graphite crystallites of amorphous carbon is 0.340-0.385 nm. 5. A high-power lithium-ion battery according to claim 4, characterized in that: the interlayer distance d(002) of the graphite microcrystals is 0.35-0.38 nm. 6. A high-power lithium-ion battery according to claim 1, characterized in that: the D50 of the amorphous carbon is 5-15 μm. 7. A high-power lithium-ion battery according to claim 1, characterized in that: the specific surface area of the amorphous carbon is 0.5-5 m ² /g. 8 . The high-power lithium-ion battery according to claim 1 , wherein the specific surface area of the amorphous carbon is 3-4 m ² /g. 9 . The high-power lithium-ion battery according to claim 1 , wherein the tap density of the amorphous carbon is 0.7-1.2 g/cm ³ . 10. A kind of high-power lithium ion battery according to claim 1, is characterized in that: described negative pole comprises current collector, the amorphous carbon that is attached on the current collector, conducting agent and binding agent; The ratio of amorphous carbon: conductive agent: binder is 85～95:10～2:5～3; Described conductive agent is Super P or conductive carbon black; The binder is PVDF, SBR or CMC; The interlayer distance d(002) of the graphite microcrystal is 0.35-0.38nm; The D50 of the amorphous carbon is 5-15 μm.