High-rate and high-capacity lithium ion battery cell

Abstract

The invention relates to the field of battery cells, in particular to a high-rate and high-capacity lithium ion battery cell. The technical problems of insufficient endurance, low production efficiency of a lamination process, complex process and reduction of overall manufacturing performance due to the fact that a high-rate battery cell basically adopts a lamination or winding multi-tab mode and totally adopts graphite as a negative electrode is low in capacity are solved. According to the technical scheme, the high-rate and high-capacity lithium ion battery cell comprises a roll core and electrolyte, wherein the roll core is formed by winding a positive plate, a negative plate and a diaphragm; the electrolyte is filled in the roll core; the anode, the cathode, the pole piece and the tab all adopt a middle structure, the polyacrylate emulsion is matched with the silicon cathode for use, the silicon cathode expansion inhibitor is added into the electrolyte, and the expansion of the silicon cathode is also greatly improved through the cathode binder and the silicon cathode expansion inhibitor added into the electrolyte, so that the performance of the battery cell is improved; and the rate capability of the battery cell is improved by adopting the electrolyte with high lithium salt concentration, so that the battery cell is high in rate and high in capacity.

Description

Technical Field

[0001] The present invention relates to the technical field of battery cells, and in particular to a high-rate and high-capacity lithium-ion battery cell. Background Art

[0002] Lithium-ion cells are the core component of lithium-ion batteries, which mainly rely on the movement of lithium ions between the positive and negative electrodes to work. Lithium-ion batteries are relatively small in weight and volume, but can store more electrical energy, giving them significant advantages in portable devices.

[0003] At present, most of the negative electrode materials of battery cells in the industry are made of artificial graphite, natural graphite and composite (artificial and natural) graphite. For high-rate batteries, stacking or winding multi-pole ears are basically adopted. The capacity of high-rate batteries that use all graphite as the negative electrode is low, resulting in insufficient battery life. In addition, the stacking process has low production efficiency, and the winding multi-pole ears have complex processes, which reduces the overall manufacturing performance.

[0004] Therefore, the above-mentioned existing high-rate batteries basically adopt the stacking or winding multi-pole ear method, and all use graphite as the negative electrode. The capacity of the high-rate batteries is low, which leads to insufficient battery life, and the stacking process has low production efficiency, and the winding multi-pole ear has a complicated process; therefore, we propose a high-rate and high-capacity lithium-ion battery cell. Summary of the invention

[0005] In order to overcome the problem that the existing high-rate battery cells basically adopt the stacking or winding multi-pole ear method, all use graphite as the negative electrode, the capacity of the high-rate battery cells is low, resulting in insufficient battery life, and the stacking process has low production efficiency, and the winding multi-pole ear has a complex process, which reduces the overall manufacturing performance.

[0006] The technical solution of the present invention is: a high-rate and high-capacity lithium-ion battery cell, including a core formed by winding a positive electrode sheet, a negative electrode sheet and a diaphragm, and an electrolyte filled in the core; the positive and negative electrodes, the electrode sheets and the pole ears all adopt a central structure, the positive and negative electrode sheets are respectively composed of positive electrode powder and negative electrode powder, and a pole ear welding position is provided between the positive electrode powder and the negative electrode powder.

[0007] Preferably, the positive and negative electrodes, pole pieces and pole ears all adopt a central structure, polyacrylate emulsion is used in combination with the silicon negative electrode, a silicon negative electrode expansion inhibitor is added to the electrolyte, and the expansion of the silicon negative electrode is greatly improved by adding a negative electrode binder and an inhibitor of silicon negative electrode expansion to the electrolyte, thereby improving the performance of the battery cell. A high lithium salt concentration electrolyte is used to improve the rate performance of the battery cell, so that the battery cell has a high rate and a high capacity.

[0008] Preferably, the electrode sheet comprises a positive electrode active material layer and a positive electrode current collector, wherein the positive electrode active material layer is composed of 94% to 97% positive electrode active material, 0.8% to 1.5% positive electrode binder, and 2.5% to 4.5% positive electrode conductive agent.

[0009] Preferably, the positive electrode active material includes one or more of lithium cobalt oxide and lithium nickel cobalt manganese oxide, and the particle size D50 of the active material is 5 to 10 um.

[0010] Preferably, the positive electrode conductive agent is composed of 0.5% to 3% conductive carbon black, 1% to 2% CNT conductive liquid and 0.5% to 1% graphene conductive agent.

[0011] Preferably, the positive electrode current collector is composed of aluminum foil or composite aluminum foil, and the thickness of the foil is 16 to 20 um.

[0012] Preferably, the negative electrode sheet includes a negative electrode active material layer and a negative electrode current collector, the negative electrode active material layer is composed of 94% to 96% of negative electrode active material, 1% to 3% of negative electrode conductive agent, and 2% to 3% of negative electrode binder, the negative electrode active material is composed of high-end artificial graphite and layered porous silicon negative electrode, the high-end artificial graphite has a gram capacity of 350 to 380 mAh / g, and is compacted to 1.5 to 1.65 g / cm3, the silicon negative electrode has a gram capacity of 1500 to 2200 mAh / g, and the ratio of silicon negative electrode to high-end artificial graphite is 0.4 to 1:1.

[0013] Preferably, the negative electrode binder is one or more of polyacrylate emulsion, polyvinylidene fluoride emulsion, and ethyl cellulose emulsion, and the negative electrode current collector is composed of electrolytic copper foil or composite copper foil, and the foil thickness is 8 to 12 um.

[0014] Preferably, the positive electrode tab is composed of an aluminum strip with a thickness of 0.1 to 0.2 mm, and the negative electrode tab is composed of a nickel strip, a copper strip or a nickel-plated copper strip with a thickness of 0.1 to 0.2 mm.

[0015] Preferably, the electrolyte is a mixed solution of ethylene carbonate, diethyl carbonate, propylene carbonate, ethyl propionate, propyl butyrate and fluorobenzene, to which lithium hexafluorophosphate, lithium bis(oxalatoborate) and an additive for inhibiting the expansion of the silicon negative electrode are added at a concentration of 1.1 to 1.3 mol / L.

[0016] Beneficial effects of the present invention: 1. According to the previous high-rate battery cells, which basically adopt the stacking or winding multi-pole ear method, all use graphite as the negative electrode to make the high-rate battery cell capacity low, resulting in insufficient endurance, and the stacking process has low production efficiency, and the winding multi-pole ear is adopted, the process is complicated, and the overall manufacturing performance is reduced. The difference is that a winding core formed by winding a positive electrode sheet, a negative electrode sheet and a diaphragm and an electrolyte filled in the winding core are arranged; the positive and negative electrodes, the pole sheets and the pole ears all adopt a central structure, a polyacrylate emulsion is used in conjunction with a silicon negative electrode, a silicon negative electrode expansion inhibitor is added to the electrolyte, and the expansion of the silicon negative electrode is greatly improved by adding a negative electrode binder and an inhibitor to the electrolyte to inhibit the expansion of the silicon negative electrode, thereby improving the battery cell performance, and a high lithium salt concentration electrolyte is used to improve the battery cell rate performance, so that the battery cell has a high rate and a high capacity. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a schematic diagram of the positive electrode sheet of the lithium-ion battery cell of the present invention; Figure 2 It is a schematic diagram of the negative electrode sheet of the lithium-ion battery cell of the present invention.

[0018] Explanation of the accompanying reference numerals: 1. positive electrode powder; 2. negative electrode powder; 3. electrode tab welding position. DETAILED DESCRIPTION

[0019] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0020] See also Figure 1-2 A high-rate and high-capacity lithium-ion battery cell, comprising a core formed by winding a positive electrode sheet, a negative electrode sheet and a separator, and an electrolyte filled in the core; the positive and negative electrodes, the electrode sheets and the pole ears all adopt a central structure, the positive and negative electrode sheets are respectively composed of positive electrode powder 1 and negative electrode powder 2, and a pole ear welding position 3 is provided between the positive electrode powder 1 and the negative electrode powder 2.

[0021] Example 1: Please refer to Figure 1-2 In this embodiment, the electrode sheet includes a positive electrode active material layer and a positive electrode current collector. The positive electrode active material layer is composed of 94% positive electrode active material, 0.8% positive electrode binder, and 2.5% positive electrode conductive agent. The positive electrode active material includes lithium cobalt oxide and lithium nickel cobalt manganese oxide, and the active material particle size D50 is 5um.

[0022] In this embodiment, the positive electrode conductive agent is composed of 0.5% conductive carbon black, 1% CNT conductive liquid and 0.5% graphene conductive agent, and the positive electrode current collector is composed of aluminum foil or composite aluminum foil, and the foil thickness is 16um.

[0023] In this embodiment, the negative electrode sheet includes a negative electrode active material layer and a negative electrode current collector. The negative electrode active material layer is composed of 94% negative electrode active material, 1% negative electrode conductive agent, and 2% negative electrode binder. The negative electrode active material is composed of high-end artificial graphite and layered porous silicon negative electrode. The high-end artificial graphite has a gram capacity of 350mAh / g and a compaction of 1.5g / cm3. The gram capacity of the silicon negative electrode is 1500mAh / g. The ratio of the silicon negative electrode to the high-end artificial graphite is 0.4:1. The negative electrode binder is one or more of polyacrylate emulsion, polyvinylidene fluoride emulsion, and ethyl cellulose emulsion. The negative electrode collector is composed of electrolytic copper foil or composite copper foil, and the foil thickness is 8um.

[0024] In this embodiment, the positive electrode tab is composed of an aluminum strip with a thickness of 0.1 mm, the negative electrode tab is composed of a nickel strip, a copper strip or a nickel-plated copper strip with a thickness of 0.1 mm, and the electrolyte is a mixed solution of ethylene carbonate, diethyl carbonate, propylene carbonate, ethyl propionate, propyl butyrate, and fluorobenzene, to which lithium hexafluorophosphate, lithium bis(oxalatoborate) and an additive to inhibit the expansion of the silicon negative electrode are added at a concentration of 1.1 mol / L.

[0025] Example 2: Please refer to Figure 1-2 In this embodiment, the electrode sheet includes a positive electrode active material layer and a positive electrode current collector. The positive electrode active material layer is composed of 97% positive electrode active material, 1.5% positive electrode binder, and 4.5% positive electrode conductive agent. The positive electrode active material includes lithium cobalt oxide and lithium nickel cobalt manganese oxide, and the active material particle size D50 is 10um.

[0026] In this embodiment, the positive electrode conductive agent is composed of 3% conductive carbon black, 2% CNT conductive liquid and 1% graphene conductive agent, and the positive electrode current collector is composed of aluminum foil or composite aluminum foil, and the foil thickness is 20um.

[0027] In this embodiment, the negative electrode sheet includes a negative electrode active material layer and a negative electrode current collector. The negative electrode active material layer is composed of 96% negative electrode active material, 3% negative electrode conductive agent, and 3% negative electrode binder. The negative electrode active material is composed of high-end artificial graphite and layered porous silicon negative electrode. The high-end artificial graphite has a gram capacity of 380mAh / g and a compaction of 1.65g / cm3. The gram capacity of the silicon negative electrode is 2200mAh / g. The ratio of the silicon negative electrode to the high-end artificial graphite is 1:1. The negative electrode binder is one or more of polyacrylate emulsion, polyvinylidene fluoride emulsion, and ethyl cellulose emulsion. The negative electrode collector is composed of electrolytic copper foil or composite copper foil, and the foil thickness is 12um.

[0028] It should be specifically noted that the maximum rate of battery cells produced by the above-mentioned material system can reach 30C to 40C, which is 10% to 30% higher than the capacity of battery cells produced with graphite negative electrodes at the same rate.

[0029] In this embodiment, the positive electrode tab is composed of an aluminum strip with a thickness of 0.2 mm, the negative electrode tab is composed of a nickel strip, a copper strip or a nickel-plated copper strip with a thickness of 0.2 mm, and the electrolyte is a mixed solution of ethylene carbonate, diethyl carbonate, propylene carbonate, ethyl propionate, propyl butyrate, and fluorobenzene, to which lithium hexafluorophosphate, lithium bis(oxalatoborate) and an additive to inhibit the expansion of the silicon negative electrode are added at a concentration of 1.3 mol / L.

[0030] The embodiments of the present invention are described in detail above with reference to the accompanying drawings, but the present invention is not limited to the above embodiments, and various changes can be made within the knowledge scope of those skilled in the art without departing from the spirit of the present invention.

Claims

1. A high-rate and high-capacity lithium-ion battery cell, comprising a positive electrode sheet; characterized in that: It also includes a winding core formed by winding a negative electrode sheet and a separator, and an electrolyte filled in the winding core; the positive and negative electrode sheets and the pole ears all adopt a central structure, the positive and negative electrode sheets are respectively composed of positive electrode powder (1) and negative electrode powder (2), and a pole ear welding position (3) is provided between the positive electrode powder (1) and the negative electrode powder (2).

2. A high rate and high capacity lithium ion battery cell according to claim 1, characterized in that: The electrode sheet includes a positive electrode active material layer and a positive electrode current collector. The positive electrode active material layer is composed of 94% to 97% of positive electrode active material, 0.8% to 1.5% of positive electrode binder, and 2.5% to 4.5% of positive electrode conductive agent.

3. A high rate and high capacity lithium ion battery cell according to claim 2, characterized in that: The positive electrode active material includes one or more of lithium cobalt oxide and lithium nickel cobalt manganese oxide, and the particle size D50 of the active material is 5 to 10 um.

4. A high rate and high capacity lithium ion battery cell according to claim 1, characterized in that: The positive electrode conductive agent is composed of 0.5% to 3% conductive carbon black, 1% to 2% CNT conductive liquid and 0.5% to 1% graphene conductive agent.

5. A high rate and high capacity lithium ion battery cell according to claim 2, characterized in that: The positive electrode current collector is composed of aluminum foil or composite aluminum foil, and the thickness of the foil is 16 to 20 um.

6. A high rate and high capacity lithium ion battery cell according to claim 1, characterized in that: The negative electrode sheet includes a negative electrode active material layer and a negative electrode current collector. The negative electrode active material layer is composed of 94% to 96% negative electrode active material, 1% to 3% negative electrode conductive agent, and 2% to 3% negative electrode binder. The negative electrode active material is composed of high-end artificial graphite and layered porous silicon negative electrode. The high-end artificial graphite has a gram capacity of 350 to 380 mAh / g and a compaction of 1.5 to 1.65 g / cm3. The gram capacity of the silicon negative electrode is 1500 to 2200 mAh / g, and the ratio of silicon negative electrode to high-end artificial graphite is 0.4 to 1:

1.

7. A high rate and high capacity lithium ion battery cell according to claim 6, characterized in that: The negative electrode binder is one or more of polyacrylate emulsion, polyvinylidene fluoride emulsion and ethyl cellulose emulsion. The negative electrode current collector is composed of electrolytic copper foil or composite copper foil, and the foil thickness is 8-12 um.

8. The high-rate and high-capacity lithium-ion battery cell according to claim 1, characterized in that: The positive electrode tab is composed of an aluminum strip with a thickness of 0.1 to 0.2 mm, and the negative electrode tab is composed of a nickel strip, a copper strip or a nickel-plated copper strip with a thickness of 0.1 to 0.2 mm.

9. The high-rate and high-capacity lithium-ion battery cell according to claim 1, characterized in that: The electrolyte is a mixed solution of ethylene carbonate, diethyl carbonate, propylene carbonate, ethyl propionate, propyl butyrate and fluorobenzene, to which lithium hexafluorophosphate, lithium bis(oxalatoborate) and an additive for inhibiting silicon negative electrode expansion at a concentration of 1.1 to 1.3 mol / L are added.

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