Lithium ion battery with high capacity retention rate, and preparation method and charging and discharging methods therefor

Abstract

The invention relates to a lithium ion battery with a high capacity retention rate, and a preparation method and charging and discharging methods thereof. The lithium ion battery comprises a positive electrode plate, a negative electrode plate, separators arranged between the positive electrode plate and the negative electrode plate at intervals, and an electrolyte, and further comprises a third electrode and a fourth electrode, which are independent of each other and provided between the positive electrode plate and the negative electrode plate, wherein the third electrode and the fourth electrode are separated by means of a single-layer separator, a metal lithium electrode being used as the third electrode, and an activated carbon electrode being used as the fourth electrode. The third electrode and the fourth electrode cooperate with each other to realize supplementation of active lithium of a lithium ion battery at different stages by means of controlled use at different stages, thereby achieving repair and regeneration of the lithium ion battery, and finally, comprehensively increasing the long-cycle capacity retention rate of the current lithium ion battery, especially a solid-liquid lithium ion battery, and increasing the cruising ability retention rate of an electric vehicle.

Claims

1. A lithium ion battery with a high capacity retention rate, comprising a positive electrode plate, a negative electrode plate, separators arranged between the positive electrode plate and the negative electrode plate, and an electrolyte, characterized in that: the lithium ion battery further comprises a third electrode and a fourth electrode, which are independent of each other and provided between the positive electrode plate and the negative electrode plate, wherein the third electrode and the fourth electrode are separated by means of a single-layer separator, a metal lithium electrode being used as the third electrode, and an activated carbon electrode being used as the fourth electrode.

2. The lithium ion battery with a high capacity retention rate according to claim 1, characterized in that: the third electrode is preferably a lithium foil or a lithium alloy foil with a thickness of 100-500 μm.

3. The lithium ion battery with a high capacity retention rate according to claim 2, characterized in that: the lithium foil or lithium alloy foil is roughened by means of pre-rolling, and the pre-rolling is preformed by using a stainless steel roller with grid raised points, wherein the rolling pressure is 0.1-10 MPa.

4. The Ihe lithium ion battery with a high capacity retention rate according to claim 1, characterized in that: the fourth electrode comprises the following components in percentage by weight: 35-55% of activated carbon, 40-55% of hard carbon, 5% of a binder, 4% of a conductive agent, 1% of a pore former, combined with a porous current collector.

5. The lithium ion battery with a high capacity retention rate according to claim 1, characterized in that: the number of layers of the third electrode and the fourth electrode is 1-4.

6. The lithium ion battery with a high capacity retention rate according to claim 5, characterized in that the lithium ion battery is prepared by the following steps: (1) the positive electrode plate, the negative electrode plate, and the separator are wound or laminated according to a conventional process to form a battery cell structure; (2) the third electrode and the fourth electrode are wound or laminated inside or outside the above-mentioned battery cell structure, and the third electrode and the fourth electrode are separated by means of a single-layer separator; and (3) the electrolyte is injected according to conventional subsequent steps, and sealed to form the lithium ion battery.

7. The charging and discharging method of the lithium ion battery with a high capacity retention rate according to claim 6, characterized in that: in the step (1), the third electrode and the fourth electrode are discharged, preferably at a discharge current of 0.05 A-2 A, the preferred discharge cut-off condition is discharge voltage or discharge time, wherein the preferred discharge cut-off voltage is 2.3-2.9 V and the discharge cut-off time is 1 min-30 min.

8. The charging and discharging method of the lithium ion battery with a high capacity retention rate according to claim 6, characterized in that: in the step (2), the fourth electrode is connected in parallel with the negative electrode of the lithium ion battery to perform the discharge with the positive electrode of the lithium-ion battery, wherein the discharge cut-off voltage is 2.3-2.9 V.

9. A charging and discharging method of the lithium ion battery with a high capacity retention rate according to claim 1, characterized in that: the method comprise the following steps: (1) when the number of turns is n, the negative and positive electrodes of the lithium ion battery are only charged; after the charging is finished, the third electrode and the fourth electrode are discharged with controlled current; (2) after standing for 1 hour, the fourth electrode is connected in parallel with the negative electrode of the lithium ion battery to perform the discharge with the positive electrode of the lithium-ion battery; (3) the normal charge and discharge between the positive and negative electrodes of the lithium ion battery occur at the (n+1) th and subsequent turns; (4) the normal charge and discharge are continued until the next fixed number of turns or conditional number of turns, and steps (1) to (4) are repeated; and (5) when the number of cycles reaches the specified number of turns, the charging and discharging methods are finished; wherein the number of turns n may be a fixed number of turns or a conditional number of turns, and the fixed number of turns is preferably 300, 500, 700, 1000, 1300, 1500, 1800, 2000, 2500, 3000, 3500, 4000, 4500, or 5000.

10. The charging and discharging method of the lithium ion battery with a high capacity retention rate according to claim 9, characterized in that: in the step (1), the third electrode and the fourth electrode are discharged, preferably at a discharge current of 0.05 A-2 A, the preferred discharge cut-off condition is discharge voltage or discharge time, wherein the preferred discharge cut-off voltage is 2.3-2.9 V and the discharge cut-off time is 1 min-30 min.

11. The charging and discharging method of the lithium ion battery with a high capacity retention rate according to claim 9, characterized in that: in the step (2), the fourth electrode is connected in parallel with the negative electrode of the lithium ion battery to perform the discharge with the positive electrode of the lithium-ion battery, wherein the discharge cut-off voltage is 2.3-2.9 V.

12. A charging and discharging method of the lithium ion battery with a high capacity retention rate according to claim 2, characterized in that: the method comprise the following steps: (1) when the number of turns is n, the negative and positive electrodes of the lithium ion battery are only charged; after the charging is finished, the third electrode and the fourth electrode are discharged with controlled current; (2) after standing for 1 hour, the fourth electrode is connected in parallel with the negative electrode of the lithium ion battery to perform the discharge with the positive electrode of the lithium-ion battery; (3) the normal charge and discharge between the positive and negative electrodes of the lithium ion battery occur at the (n+1) th and subsequent turns; (4) the normal charge and discharge are continued until the next fixed number of turns or conditional number of turns, and steps (1) to (4) are repeated; and (5) when the number of cycles reaches the specified number of turns, the charging and discharging methods are finished; wherein the number of turns n may be a fixed number of turns or a conditional number of turns, and the fixed number of turns is preferably 300, 500, 700, 1000, 1300, 1500, 1800, 2000, 2500, 3000, 3500, 4000, 4500, or 5000.

13. The charging and discharging method of the lithium ion battery with a high capacity retention rate according to claim 12, characterized in that: in the step (1), the third electrode and the fourth electrode are discharged, preferably at a discharge current of 0.05 A-2 A, the preferred discharge cut-off condition is discharge voltage or discharge time, wherein the preferred discharge cut-off voltage is 2.3-2.9 V and the discharge cut-off time is 1 min-30 min.

14. The charging and discharging method of the lithium ion battery with a high capacity retention rate according to claim 12, characterized in that: in the step (2), the fourth electrode is connected in parallel with the negative electrode of the lithium ion battery to perform the discharge with the positive electrode of the lithium-ion battery, wherein the discharge cut-off voltage is 2.3-2.9 V.

Description

DETAILED DESCRIPTION OF EMBODIMENTS

[0049] The present invention is further described in detail below in combination with examples.

Example I

[0050] A lithium ion battery with a high capacity retention rate, the preparation method and charging and discharging methods thereof comprise the following steps:

[0051] (1) Providing a graphite negative electrode, a NCM111 positive electrode, and a separator of the lithium ion battery, and laminating them according to a conventional process.

[0052] (2) Providing a lithium foil with a thickness of 100 μm, which is roughened by using a stainless steel roller with a roughness of 100 meshes at a rolling pressure of 10 MPa as a third electrode; wet mixing 50% of activated carbon, 40% of hard carbon, 5% of P VDF, 4% of acetylene black, 1% of Li.sub.2SO.sub.4 and foam nickel, rolling and drying same to obtain a fourth electrode, laminating one layer of the third electrode and one layer of the fourth electrode on both sides of the above battery cell, respectively, with a separator therebetween for separation. The negative electrode tabs of the lithium ion battery are ultrasonically spot-welded together and led out from the outer tab, the positive electrode tabs of the lithium ion battery are ultrasonically spot-welded together and led out from the outer tab, two lithium metal electrodes on both sides are calendered and bonded, and led out from the outer tab, and two fourth electrodes are ultrasonically spot-welded together and led out from the outer tab to form a lithium ion battery battery cell with four electrodes. After electrolyte injection, and pre-sealing, top sealing, side sealing and secondary sealing with aluminum plastic films, a lithium ion battery battery cell 10 Ah is formed.

[0053] (3) After the conventional formation, 10 charge and discharge cycle test is started on the battery with a voltage from 4.2 V-3 V, when the number of turns is 300, the lithium ion battery is charged between the negative and positive electrodes only and discharged at 0.05 A for 10 min between the third and fourth electrodes at the end of charging.

[0054] (4) Next, standing for 1 hour, the fourth electrode is connected in parallel with the negative electrode of the lithium ion battery to perform the 10 discharge with the positive electrode of the lithium-ion battery, wherein the discharge cut-off voltage is 2.9 V.

[0055] (5) The normal charge and discharge between the positive and negative electrodes of the lithium ion battery occur at the 301th-499th turns.

[0056] (6) When the number of turns is 500, the negative and positive electrodes of the lithium ion battery are only charged; after the charging is finished, the third electrode and the fourth electrode are discharged at 0.05 A for 20 min.

[0057] (7) Next, standing for 1 hour, the fourth electrode is connected in parallel with the negative electrode of the lithium ion battery to perform the discharge with the positive electrode of the lithium-ion battery, wherein the discharge cut-off voltage is 2.8 V.

[0058] (8) The normal charge and discharge between the positive and negative electrodes of the lithium ion battery occur at the 501th-699th turns.

[0059] (9) When the number of turns is 700, the negative and positive electrodes of the lithium ion battery are only charged; after the charging is finished, the third electrode and the fourth electrode are discharged at 0.05 A for 30 min.

[0060] (10) Next, standing for 1 hour, the fourth electrode is connected in parallel with the negative electrode of the lithium ion battery to perform the discharge with the positive electrode of the lithium-ion battery, wherein the discharge cut-off voltage is 2.7 V.

[0061] (11) The normal charge and discharge between the positive and negative electrodes of the lithium ion battery occur at the 701th-999th turns.

[0062] (12) When the number of turns is 1000, the negative and positive electrodes of the lithium ion battery are only charged; after the charging is finished, the third electrode and the fourth electrode are discharged at 0.1 A for 20 min.

[0063] (13) Next, standing for 1 hour, the fourth electrode is connected in parallel with the negative electrode of the lithium ion battery to perform the discharge with the positive electrode of the lithium-ion battery, wherein the discharge cut-off voltage is 2.6 V.

[0064] (14) The normal charge and discharge between the positive and negative electrodes of the lithium ion battery occur at the 1001th-1299th turns.

[0065] (15) When the number of turns is 1000, the negative and positive electrodes of the lithium ion battery are only charged; after the charging is finished, the third electrode and the fourth electrode are discharged at 1 A to 2.6 V.

[0066] (16) Next, standing for 1 hour, the fourth electrode is connected in parallel with the negative electrode of the lithium ion battery to perform the discharge with the positive electrode of the lithium-ion battery, wherein the discharge cut-off voltage is 2.5 V.

[0067] (17) The normal charge and discharge between the positive and negative electrodes of the lithium ion battery occur at the 1301th-1499th turns.

[0068] (18) When the number of turns is 1500, the negative and positive electrodes of the lithium ion battery are only charged; after the charging is finished, the third electrode and the fourth electrode are discharged at 2 A to 2.5 V.

[0069] (19) Next, standing for 1 hour, the fourth electrode is connected in parallel with the negative electrode of the lithium ion battery to perform the discharge with the positive electrode of the lithium-ion battery, wherein the discharge cut-off voltage is 2.5 V.

[0070] (20) The normal charge and discharge between the positive and negative electrodes of the lithium ion battery occur at the 1501th-2000th turns.

[0071] (21) When the 2000th turn is reached, the discharge is over, and the discharge capacity retention rate is calculated.

Example II

[0072] A lithium ion battery with a high capacity retention rate, the preparation method and charging and discharging methods therefor comprise the following steps:

[0073] (1) Providing a graphite negative electrode, a NC A positive electrode, and a separator of the lithium ion battery, and laminating them according to a conventional process.

[0074] (2) Providing a lithium foil with a thickness of 100 μm, which is roughened by using a stainless steel roller with a roughness of 500 meshes at a rolling pressure of 0.1 MPa as a third electrode; wet mixing 50% of activated carbon, 40% of hard carbon, 5% of P VDF, 4% of acetylene black, 1% of Li.sub.2SO.sub.4 and foam nickel, rolling and drying same to obtain a fourth electrode, laminating one layer of the third electrode and one layer of the fourth electrode on both sides of the above battery cell, respectively, with a separator therebetween for separation; the negative electrode tabs of the lithium ion battery are ultrasonically spot-welded together and led out from the outer tab, the positive electrode tabs of the lithium ion battery are ultrasonically spot-welded together and led out from the outer tab, two lithium metal electrodes on both sides are calendered and bonded, and led out from the outer tab, and two fourth electrodes are ultrasonically spot-welded together and led out from the outer tab to form a lithium ion battery battery cell with four electrodes. After electrolyte injection, and pre-sealing, top sealing, side sealing and secondary sealing with aluminum plastic films, a lithium ion battery battery cell 10 Ah is formed.

[0075] (3) After the conventional formation, 10 charge and discharge cycle test is started on the battery with a voltage from 4.2 V-3 V, when the number of turns is 300, the lithium ion battery is charged between the negative and positive electrodes only and discharged at 0.05 A for 10 min between the third and fourth electrodes at the end of charging.

[0076] (4) Next, standing for 1 hour, the fourth electrode is connected in parallel with the negative electrode of the lithium ion battery to perform the discharge with the positive electrode of the lithium-ion battery, wherein the discharge cut-off voltage is 2.9 V.

[0077] (5) The normal charge and discharge between the positive and negative electrodes of the lithium ion battery occur at the 301th-499th turns.

[0078] (6) When the number of turns is 500, the negative and positive electrodes of the lithium ion battery are only charged; after the charging is finished, the third electrode and the fourth electrode are discharged at 0.05 A for 20 min.

[0079] (7) Next, standing for 1 hour, the fourth electrode is connected in parallel with the negative electrode of the lithium ion battery to perform the discharge with the positive electrode of the lithium-ion battery, wherein the discharge cut-off voltage is 2.8 V.

[0080] (8) The normal charge and discharge between the positive and negative electrodes of the lithium ion battery occur at the 501th-699th turns.

[0081] (9) When the number of turns is 700, the negative and positive electrodes of the lithium ion battery are only charged; after the charging is finished, the third electrode and the fourth electrode are discharged at 0.05 A for 30 min.

[0082] (10) Next, standing for 1 hour, the fourth electrode is connected in parallel with the negative electrode of the lithium ion battery to perform the discharge with the positive electrode of the lithium-ion battery, wherein the discharge cut-off voltage is 2.7 V.

[0083] (11) The normal charge and discharge between the positive and negative electrodes of the lithium ion battery occur at the 701th-999th turns.

[0084] (12) When the number of turns is 1000, the negative and positive electrodes of the lithium ion battery are only charged; after the charging is finished, the third electrode and the fourth electrode are discharged at 0.1 A for 20 min.

[0085] (13) Next, standing for 1 hour, the fourth electrode is connected in parallel with the negative electrode of the lithium ion battery to perform the discharge with the positive electrode of the lithium-ion battery, wherein the discharge cut-off voltage is 2.6 V.

[0086] (14) The normal charge and discharge between the positive and negative electrodes of the lithium ion battery occur at the 1001th-1299th turns.

[0087] (15) When the number of turns is 1000, the negative and positive electrodes of the lithium ion battery are only charged; after the charging is finished, the third electrode and the fourth electrode are discharged at 1 A to 2.6 V.

[0088] (16) Next, standing for 1 hour, the fourth electrode is connected in parallel with the negative electrode of the lithium ion battery to perform the discharge with the positive electrode of the lithium-ion battery, wherein the discharge cut-off voltage is 2.5 V.

[0089] (17) The normal charge and discharge between the positive and negative electrodes of the lithium ion battery occur at the 1301th-1499th turns.

[0090] (18) When the number of turns is 1500, the negative and positive electrodes of the lithium ion battery are only charged; after the charging is finished, the third electrode and the fourth electrode are discharged at 2 A to 2.5 V.

[0091] (19) Next, standing for 1 hour, the fourth electrode is connected in parallel with the negative electrode of the lithium ion battery to perform the discharge with the positive electrode of the lithium-ion battery, wherein the discharge cut-off voltage is 2.5 V.

[0092] (20) The normal charge and discharge between the positive and negative electrodes of the lithium ion battery occur at the 1501th-2000th turns.

[0093] (21) When the 2000th turn is reached, the discharge is over, and the discharge capacity retention rate is calculated.

Example III

[0094] A lithium ion battery with a high capacity retention rate, the preparation method and charging and discharging methods therefor comprise the following steps:

[0095] (1) Providing a silicon carbon negative electrode, a NCM523 positive electrode, and a separator of the lithium ion battery, and laminating them according to a conventional process.

[0096] (2) Providing a lithium foil with a thickness of 200 μm, which is roughened by using a stainless steel roller with a roughness of 300 meshes at a rolling pressure of 1 MPa as a third electrode; wet mixing 35% of activated carbon, 55% of hard carbon, 5% of P VDF, 4% of acetylene black, 1% of Li.sub.2SO.sub.4 and foam nickel, rolling and drying same to obtain a fourth electrode, laminating two layers of the lithium foil and two layers of the activated carbon electrode at the center of the above battery cell, respectively, with a separator therebetween for separation; the negative electrode tabs of the lithium ion battery are ultrasonically spot-welded together and led out from the outer tab, the positive electrode tabs of the lithium ion battery are ultrasonically spot-welded together and led out from the outer tab, two lithium metal electrodes on both sides are calendered and bonded and led out from the outer tab, and two fourth electrodes are ultrasonically spot-welded together and led out from the outer tab to form a lithium ion battery battery cell with four electrodes. After electrolyte injection, and pre-sealing, top sealing, side sealing and secondary sealing with aluminum plastic films, a lithium ion battery battery cell 40 Ah is formed.

[0097] (3) After the conventional formation, 10 charge and discharge cycle test is started on the battery with a voltage from 4.2 V-3 V, when the number of turns is 300, the lithium ion battery is charged between the negative and positive electrodes only and discharged at 2 A to 2.9 V between the third and fourth electrodes at the end of charging.

[0098] (4) Next, standing for 1 hour, the fourth electrode is connected in parallel with the negative electrode of the lithium ion battery to perform the discharge with the positive electrode of the lithium-ion battery, wherein the discharge cut-off voltage is 2.8 V.

[0099] (5) The normal charge and discharge between the positive and negative electrodes of the lithium ion battery occur at the 301th-499th turns.

[0100] (6) When the number of turns is 500, the negative and positive electrodes of the lithium ion battery are only charged; after the charging is finished, the third electrode and the fourth electrode are discharged at 2 A to 2.8 V.

[0101] (7) Next, standing for 1 hour, the fourth electrode is connected in parallel with the negative electrode of the lithium ion battery to perform the discharge with the positive electrode of the lithium-ion battery, wherein the discharge cut-off voltage is 2.7 V.

[0102] (8) The normal charge and discharge between the positive and negative electrodes of the lithium ion battery occur at the 501th-699th turns.

[0103] (9) When the number of turns is 700, the negative and positive electrodes of the lithium ion battery are only charged; after the charging is finished, the third electrode and the fourth electrode are discharged at 2 A to 2.7 V.

[0104] (10) Next, standing for 1 hour, the fourth electrode is connected in parallel with the negative electrode of the lithium ion battery to perform the discharge with the positive electrode of the lithium-ion battery, wherein the discharge cut-off voltage is 2.6 V.

[0105] (11) The normal charge and discharge between the positive and negative electrodes of the lithium ion battery occur at the 701th-999th turns.

[0106] (12) When the number of turns is 1000, the negative and positive electrodes of the lithium ion battery are only charged; after the charging is finished, the third electrode and the fourth electrode are discharged at 2 A to 2.6 V.

[0107] (13) Next, standing for 1 hour, the fourth electrode is connected in parallel with the negative electrode of the lithium ion battery to perform the discharge with the positive electrode of the lithium-ion battery, wherein the discharge cut-off voltage is 2.55 V.

[0108] (14) The normal charge and discharge between the positive and negative electrodes of the lithium ion battery occur at the 1001th-1449th turns.

[0109] (15) When the number of turns is 1500, the negative and positive electrodes of the lithium ion battery are only charged; after the charging is finished, the third electrode and the fourth electrode are discharged at 2 A to 2.6 V.

[0110] (16) Next, standing for 1 hour, the fourth electrode is connected in parallel with the negative electrode of the lithium ion battery to perform the discharge with the positive electrode of the lithium-ion battery, wherein the discharge cut-off voltage is 2.5 V.

[0111] (17) The normal charge and discharge between the positive and negative electrodes of the lithium ion battery occur at the 1501th-1799th turns.

[0112] (18) When the number of turns is 1800, the negative and positive electrodes of the lithium ion battery are only charged; after the charging is finished, the third electrode and the fourth electrode are discharged at 2 A to 2.5 V.

[0113] (19) Next, standing for 1 hour, the fourth electrode is connected in parallel with the negative electrode of the lithium ion battery to perform the discharge with the positive electrode of the lithium-ion battery, wherein the discharge cut-off voltage is 2.5 V.

[0114] (20) The 1801th-2000th turns are the normal charge and discharge between the positive and negative electrodes of the lithium ion battery, and when the 2000th turn is reached, the discharge is over, and the discharge capacity retention rate is calculated.

Example IV

[0115] A lithium ion battery with a high capacity retention rate, the preparation method and charging and discharging methods therefor comprise the following steps:

[0116] (1) Providing a graphite negative electrode, a LiFePO.sub.4 positive electrode, and a separator of the lithium ion battery, and winding them according to a conventional process.

[0117] (2) Providing a lithium foil with a thickness of 200 μm, which is roughened by using a stainless steel roller with a roughness of 200 meshes as a third electrode; wet mixing 50% of activated carbon, 40% of hard carbon, 5% of P VDF, 4% of acetylene black, 1% of Li.sub.2SO.sub.4 and stainless steel mesh, rolling and drying same to obtain a fourth electrode, winding one layer of the lithium foil and one layer of the activated carbon electrode outside the above battery cell, with a separator therebetween for separation; the negative electrode tabs of the lithium ion battery are ultrasonically spot-welded and led out from the outer tab, the positive electrode tabs of the lithium ion battery are ultrasonically spot-welded and led out from the outer tab, a single layer of lithium metal electrode is calendered and bonded, and led out from the outer tab, and a single layer of the fourth electrode is ultrasonically spot-welded and led out from the outer tab to form a lithium ion battery battery cell with four electrodes. Placing the lithium ion battery into an aluminum shell, injecting an electrolyte, and sealing same to form a lithium ion battery battery cell 20 Ah.

[0118] (3) After the conventional formation, 10 charge and discharge cycle test is started on the battery with a voltage from 3.9 V to 2.5 V, when the number of turns is 500, the lithium ion battery is charged between the negative and positive electrodes only and discharged at 0.5 A for 1 min between the third and fourth electrodes at the end of charging.

[0119] (4) Next, standing for 1 hour, the fourth electrode is connected in parallel with the negative electrode of the lithium ion battery to perform the discharge with the positive electrode of the lithium-ion battery, wherein the discharge cut-off voltage is 2.9 V.

[0120] (5) The normal charge and discharge between the positive and negative electrodes of the lithium ion battery occur at the 501th-999th turns.

[0121] (6) When the number of turns is 1000, the negative and positive electrodes of the lithium ion battery are only charged; after the charging is finished, the third electrode and the fourth electrode are discharged at 0.5 A for 5 min.

[0122] (7) Next, standing for 1 hour, the fourth electrode is connected in parallel with the negative electrode of the lithium ion battery to perform the discharge with the positive electrode of the lithium-ion battery, wherein the discharge cut-off voltage is 2.85 V.

[0123] (8) The normal charge and discharge between the positive and negative electrodes of the lithium ion battery occur at the 1001th-1499th turns.

[0124] (9) When the number of turns is 1500, the negative and positive electrodes of the lithium ion battery are only charged; after the charging is finished, the third electrode and the fourth electrode are discharged at 0.05 A for 10 min.

[0125] (10) Next, standing for 1 hour, the fourth electrode is connected in parallel with the negative electrode of the lithium ion battery to perform the discharge with the positive electrode of the lithium-ion battery, wherein the discharge cut-off voltage is 2.8 V.

[0126] (11) The normal charge and discharge between the positive and negative electrodes of the lithium ion battery occur at the 1501th-1999th turns.

[0127] (12) When the number of turns is 2000, the negative and positive electrodes of the lithium ion battery are only charged; after the charging is finished, the third electrode and the fourth electrode are discharged at 0.5 A for 15 min.

[0128] (13) Next, standing for 1 hour, the fourth electrode is connected in parallel with the negative electrode of the lithium ion battery to perform the discharge with the positive electrode of the lithium-ion battery, wherein the discharge cut-off voltage is 2.75 V.

[0129] (14) The normal charge and discharge between the positive and negative electrodes of the lithium ion battery occur at the 2001th-2499th turns.

[0130] (15) When the number of turns is 2500, the negative and positive electrodes of the lithium ion battery are only charged; after the charging is finished, the third electrode and the fourth electrode are discharged at 0.5 A for 20 min.

[0131] (16) Next, standing for 1 hour, the fourth electrode is connected in parallel with the negative electrode of the lithium ion battery to perform the discharge with the positive electrode of the lithium-ion battery, wherein the discharge cut-off voltage is 2.7 V.

[0132] (17) The normal charge and discharge between the positive and negative electrodes of the lithium ion battery occur at the 2501th-2999th turns.

[0133] (18) When the number of turns is 3000, the negative and positive electrodes of the lithium ion battery are only charged; after the charging is finished, the third electrode and the fourth electrode are discharged at 0.5 A for 25 min.

[0134] (19) Next, standing for 1 hour, the fourth electrode is connected in parallel with the negative electrode of the lithium ion battery to perform the discharge with the positive electrode of the lithium-ion battery, wherein the discharge cut-off voltage is 2.65 V.

[0135] (20) the normal charge and discharge between the positive and negative electrodes of the lithium ion battery occur at the 3001th-3499th turns.

[0136] (21) When the 3500th turn is reached, the discharge is over, and the discharge capacity retention rate is calculated.

Example V

[0137] A lithium ion battery with a high capacity retention rate, the preparation method and charging and discharging methods therefor comprise the following steps:

[0138] (1) Providing a silicon carbon negative electrode, a LiMnO.sub.2 positive electrode, and a separator of the lithium ion battery, and winding them according to a conventional process.

[0139] (2) Providing a lithium foil with a thickness of 500 μm, which is roughened by using a stainless steel roller with a roughness of 300 meshes at a rolling pressure of 10 MPa as a third electrode; wet mixing 35% of activated carbon, 55% of hard carbon, 5% of P VDF, 4% of acetylene black, 1% of Li.sub.2SO.sub.4 and foam nickel, rolling and drying same to obtain a fourth electrode. Before winding the silicon carbon negative electrode and LiMnO.sub.2 positive electrode, the lithium metal negative electrode and the activated carbon electrode are wound at the center for two turns, with a separator therebetween for separation; the negative electrode tabs of the lithium ion battery are ultrasonically spot-welded and led out from the outer tab, the positive electrode tabs of the lithium ion battery are ultrasonically spot-welded and led out from the outer tab, a single layer of lithium metal electrode is calendered and bonded, and led out from the outer tab, and a single layer of the fourth electrode is ultrasonically spot-welded and led out from the outer tab to form a lithium ion battery battery cell with four electrodes. Placing the lithium ion battery into an aluminum shell, injecting an electrolyte, and sealing same to form a lithium ion battery battery cell 30 Ah.

[0140] (3) After the conventional formation, 10 charge and discharge cycle test is started on the battery with a voltage from 4.2 V-3 V, when the number of turns is 500, the lithium ion battery is charged between the negative and positive electrodes only and discharged at 0.5 A to a voltage of 3.0 V between the third and fourth electrodes at the end of charging.

[0141] (4) Next, standing for 1 hour, the fourth electrode is connected in parallel with the negative electrode of the lithium ion battery to perform the discharge with the positive electrode of the lithium-ion battery, wherein the discharge cut-off voltage is 2.9 V.

[0142] (5) The normal charge and discharge between the positive and negative electrodes of the lithium ion battery occur at the 501th-999th turns.

[0143] (6) When the number of turns is 1000, the negative and positive electrodes of the lithium ion battery are only charged; after the charging is finished, the third electrode and the fourth electrode are discharged at 0.5 A to 2.9 V of the cut-off voltage.

[0144] (7) Next, standing for 1 hour, the fourth electrode is connected in parallel with the negative electrode of the lithium ion battery to perform the discharge with the positive electrode of the lithium-ion battery, wherein the discharge cut-off voltage is 2.8 V.

[0145] (8) The normal charge and discharge between the positive and negative electrodes of the lithium ion battery occur at the 1001th-1299th turns.

[0146] (9) When the number of turns is 1300, the negative and positive electrodes of the lithium ion battery are only charged; after the charging is finished, the third electrode and the fourth electrode are discharged at 0.5 A to 2.8 V of the cut-off voltage.

[0147] (10) Next, standing for 1 hour, the fourth electrode is connected in parallel with the negative electrode of the lithium ion battery to perform the discharge with the positive electrode of the lithium-ion battery, wherein the discharge cut-off voltage is 2.7 V.

[0148] (11) The normal charge and discharge between the positive and negative electrodes of the lithium ion battery occur at the 1301th-1499th turns.

[0149] (12) When the number of turns is 1500, the negative and positive electrodes of the lithium ion battery are only charged; after the charging is finished, the third electrode and the fourth electrode are discharged at 0.5 A to 2.7 V of the cut-off voltage.

[0150] (13) Next, standing for 1 hour, the fourth electrode is connected in parallel with the negative electrode of the lithium ion battery to perform the discharge with the positive electrode of the lithium-ion battery, wherein the discharge cut-off voltage is 2.6 V.

[0151] (14) The normal charge and discharge between the positive and negative electrodes of the lithium ion battery occur at the 1501th-1799th turns.

[0152] (15) When the number of turns is 1800, the negative and positive electrodes of the lithium ion battery are only charged; after the charging is finished, the third electrode and the fourth electrode are discharged at 1 A to 2.6 V.

[0153] (16) Next, standing for 1 hour, the fourth electrode is connected in parallel with the negative electrode of the lithium ion battery to perform the discharge with the positive electrode of the lithium-ion battery, wherein the discharge cut-off voltage is 2.5 V.

[0154] (17) The normal charge and discharge between the positive and negative electrodes of the lithium ion battery occur at the 1801th-1999th turns.

[0155] (18) When the number of turns is 2000, the negative and positive electrodes of the lithium ion battery are only charged; after the charging is finished, the third electrode and the fourth electrode are discharged at 2 A to 2.5 V.

[0156] (19) Next, standing for 1 hour, the fourth electrode is connected in parallel with the negative electrode of the lithium ion battery to perform the discharge with the positive electrode of the lithium-ion battery, wherein the discharge cut-off voltage is 2.45 V.

[0157] (20) The normal charge and discharge between the positive and negative electrodes of the lithium ion battery occur at the 2001th-2499th turns.

[0158] (21) When the number of turns is 2500, the negative and positive electrodes of the lithium ion battery are only charged; after the charging is finished, the third electrode and the fourth electrode are discharged at 2 A to 2.4 V.

[0159] (22) Next, standing for 1 hour, the fourth electrode is connected in parallel with the negative electrode of the lithium ion battery to perform the discharge with the positive electrode of the lithium-ion battery, wherein the discharge cut-off voltage is 2.3 V.

[0160] (23) The 2501th-3000th turns are the normal charge and discharge between the positive and negative electrodes of the lithium ion battery, and when the 3000th turn is reached, the discharge is over, and the discharge capacity retention rate is calculated.

Comparative Example I

[0161] A lithium ion battery, the preparation method and charging and discharging methods therefor are as follows:

[0162] (1) Providing a graphite negative electrode, a NCM111 positive electrode, and a separator of the lithium ion battery, and laminating them according to a conventional process.

[0163] (2) After electrolyte injection, and pre-sealing, top sealing, side sealing and secondary sealing with aluminum plastic films, a lithium ion battery battery cell 10 Ah is formed.

[0164] (3) After the conventional formation, 1C charge and discharge cycle test is started on the battery with a voltage from 4.2 V-3 V. After 2000 cycles, the capacity retention rate of the lithium ion battery is calculated.

Comparative Example II

[0165] A lithium ion battery, the preparation method and charging and discharging methods therefor are as follows:

[0166] (1) Providing a graphite negative electrode, a NC A positive electrode, and a separator of the lithium ion battery, and laminating them according to a conventional process.

[0167] (2) After electrolyte injection, and pre-sealing, top sealing, side sealing and secondary sealing with aluminum plastic films, a lithium ion battery battery cell 10 Ah is formed.

[0168] (3) After the conventional formation, 10 charge and discharge cycle test is started on the battery with a voltage from 4.2 V-3 V. After 2000 cycles, the capacity retention rate of the lithium ion battery is calculated.

Comparative Example III

[0169] A lithium ion battery, the preparation method and charging and discharging methods therefor are as follows:

[0170] (1) Providing a silicon carbon negative electrode, a NCM523 positive electrode, and a separator of the lithium ion battery, and laminating them according to a conventional process.

[0171] (2) After electrolyte injection, and pre-sealing, top sealing, side sealing and secondary sealing with aluminum plastic films, a lithium ion battery battery cell 40 Ah is formed.

[0172] (3) After the conventional formation, 10 charge and discharge cycle test is started on the battery with a voltage from 4.2 V-3 V. After 2000 cycles, the capacity retention rate of the lithium ion battery is calculated.

Comparative Example IV

[0173] A lithium ion battery, the preparation method and charging and discharging methods therefor are as follows:

[0174] (1) Providing a graphite negative electrode, a LiFePO.sub.4 positive electrode, and a separator of the lithium ion battery, and winding them according to a conventional process.

[0175] (2) Placing the lithium ion battery into an aluminum shell, injecting an electrolyte, and sealing same to form a lithium ion battery battery cell 20 Ah.

[0176] (3) After the conventional formation, 10 charge and discharge cycle test is started on the battery with a voltage from 3.9 V-2.5 V. After 3500 cycles, the capacity retention rate of the lithium ion battery is calculated.

Comparative Example V

[0177] A lithium ion battery, the preparation method and charging and discharging methods therefor are as follows:

[0178] (1) Providing a silicon carbon negative electrode, a LiMnO.sub.2 positive electrode, and a separator of the lithium ion battery, and winding them according to a conventional process.

[0179] (2) Placing the lithium ion battery into an aluminum shell, injecting an electrolyte, and sealing same to form a lithium ion battery battery cell 30 Ah.

[0180] (3) After the conventional formation, 10 charge and discharge cycle test is started on the battery with a voltage from 4.2 V-3 V. After 3000 cycles, the capacity retention rate of the lithium ion battery is calculated.

[0181] Test method: the discharge capacity at the 3000th turn is divided by the discharge capacity of the first turn, and the instrument adopts the MEWARE charging and discharging cabinet.

[0182] Test Results:

TABLE-US-00001 Sample Capacity retention rate (%) Example I 94 Example II 92 Example III 93 Example IV 97 Example V 93 Comparative example I 80 Comparative example II 75 Comparative example III 65 Comparative example IV 85 Comparative example V 70

[0183] It can be seen from the above table that the capacity retention rates of the lithium ion batteries of the present application after a long cycle are all more than 90%, which is greater than that of the samples of the comparative examples, thus solving the problem of irreversible attenuation in the prior art.

[0184] The examples in the specific implementations are preferred examples of the present invention, and are not intended to limit the scope of protection of the present invention, and thus: equivalent changes made according to the structure, shape and principle of the present invention shall be contained within the scope of protection of the present invention.