A high energy density cylindrical lithium battery testing method

Abstract

The present invention discloses a high-energy-density cylindrical lithium battery testing method. The cylindrical lithium battery is tested through seven steps: constant-current and constant-voltage charging → switching to rest → constant-current discharge → rest → 1-4 range-duration cycle → rest → 1-6 range-duration cycle. The intermittent cycle test of cycle testing for one month and then resting for one week satisfies the high-energy-density performance requirements of the cylindrical lithium battery, effectively reduces the attenuation of the cylindrical lithium battery capacity, ensures the cruising range requirements of electric vehicles, and improves the cycle life of the cylindrical lithium battery.

Description

Technical Field

[0001] The invention relates to a testing method for a high-energy-density cylindrical lithium battery. Background Art

[0002] With the increasing severity of environmental pollution and the energy crisis, there is an urgent need to develop energy-saving and environmentally friendly electric vehicles. However, battery technology is the bottleneck hindering the further development of electric vehicles. Lithium-ion batteries have become the preferred power source for electric vehicles due to their high energy density, high power density, long cycle life, and excellent safety.

[0003] Lithium-ion batteries have the characteristics of high energy density, high voltage, no pollution, long cycle life, no memory effect, and fast charging speed. They are not only widely used in portable electronic devices such as mobile phones, digital cameras and laptops, but also widely used in large electric equipment such as electric vehicles, electric bicycles and power tools. Therefore, the quality requirements for lithium-ion batteries are becoming increasingly higher.

[0004] Currently, in order to detect the actual discharge capacity of lithium-ion batteries under specified conditions, it is necessary to first fully charge the battery according to the specified conditions, then discharge it for a long time until the battery is discharged to the discharge cut-off voltage, and then calculate the actual discharge capacity of the lithium-ion battery under specified conditions based on the discharge time and discharge current. The specific steps are as follows:

[0005] 1. Constant current and constant voltage charging

[0006] Place the cylindrical lithium battery on a charge and discharge test cabinet (range 5V / 10V), start the charging mode, and charge the cylindrical lithium battery at a 1C constant current and constant voltage rate (1 hour rate) until the cylindrical lithium battery voltage reaches 4.2V;

[0007] 2. Transfer and put on hold

[0008] Place the cylindrical lithium battery in a charge and discharge test cabinet (range 5V / 10V) for 30 minutes, or

[0009] Remove it from the electrical test cabinet (range 5V / 10V) and place it at room temperature for 30 minutes;

[0010] 3. Constant current discharge

[0011] Place the cylindrical lithium battery on the charge and discharge test cabinet (range 5V / 10V), start the discharge mode, and

[0012] The cylindrical lithium battery is discharged at a constant current rate of 1C (1 hour rate) to reduce the voltage of the cylindrical lithium battery to 2.75V;

[0013] 4. Shelf

[0014] Place the cylindrical lithium battery on a charge and discharge test cabinet (range 5V / 10V) for 60 minutes, or

[0015] Remove it from the electrical test cabinet (range 5V / 10V) and place it at room temperature for 60 minutes;

[0016] 5.1-4 range industrial cycle

[0017] Repeat the above four test steps for the cylindrical lithium battery that has completed the above four steps. After cycling until the capacity retention rate is below 80%, terminate the test.

[0018] The lithium battery after passing the above test has the following defects: First, the precipitated metallic lithium does not have time to be reactivated, resulting in capacity loss, and the electrochemical characterization during the cycle generally requires a long static equilibrium time; second, the electrolyte will be squeezed out to both ends of the core due to the expansion of the high-energy density battery cell after charging. If the storage time is not long enough, it will cause high impedance, and the battery liquid depletion will cause capacity loss. High impedance will cause the internal temperature of the battery to be relatively high, and it will also cause the capacity to decay faster. Summary of the Invention

[0019] The purpose of the present invention is to provide a high energy density cylindrical lithium battery testing method to overcome the shortcomings of the existing technology, effectively reduce the capacity attenuation of cylindrical lithium batteries, and extend the service life of cylindrical lithium batteries.

[0020] To achieve the above objectives, the high energy density cylindrical lithium battery testing method of the present invention completes the test of the cylindrical lithium battery through the seven steps of constant current and constant voltage charging → transfer to standby → constant current discharge → standby → 1-4 working unit cycles → standby → 1-6 working unit cycles. The specific steps are as follows:

[0021] 1. Constant current and constant voltage charging: Place the cylindrical lithium battery on the charge and discharge test cabinet (range 5V / 10V), start the charging mode, and charge the cylindrical lithium battery at 1C (1 hour rate) until the cylindrical lithium battery voltage reaches

[0022] 4.2V;

[0023] 2. Place the battery on a charge and discharge test cabinet (range 5V / 10V) for 30 minutes, or remove it from the charge and discharge test cabinet (range 5V / 10V) and place it at room temperature for another 30 minutes.

[0024] 3. Constant current discharge: Place the cylindrical lithium battery on a charge and discharge test cabinet (range 5V / 10V), start the discharge mode, and perform 1C constant current discharge (1 hour rate) on the cylindrical lithium battery to reduce the voltage of the cylindrical lithium battery to 2.75V;

[0025] 4. Place the cylindrical lithium battery on a charge and discharge test cabinet (range 5V / 10V) for 60 minutes, or remove it from the charge and discharge test cabinet (range 5V / 10V) and place it at room temperature for another 60 minutes;

[0026] 5. 1-4 range cycle: Repeat the above 4 test steps for the cylindrical lithium battery that has completed the above 4 steps, cycle the test for one month, and then stop the test;

[0027] 6. Shelf: Shelf the cylindrical lithium battery for one week, remove it from the charge and discharge test cabinet (range 5V / 10V), and shelf it at room temperature for one week;

[0028] 7. 1-6 range cycle: Repeat the above 6 test steps for the cylindrical lithium battery that has completed the above 6 steps. Stop the test after the capacity retention rate of the cylindrical lithium battery is below 80%.

[0029] The high energy density cylindrical lithium battery testing method of the present invention has the following excellent effects compared with the prior art.

[0030] The high-energy-density cylindrical lithium battery testing method of the present invention is adopted, through intermittent cycle testing of cycle testing for one month and then resting for one week, which not only meets the requirements of high-energy-density performance of cylindrical lithium batteries, but also effectively reduces the attenuation of the capacity of cylindrical lithium batteries, ensures the range requirements of electric vehicles, and improves the cycle life of cylindrical lithium batteries; because of the long period of rest for a week, some of the analyzed metallic lithium can be reactivated and contribute to the capacity of the cylindrical lithium battery, and the electrolyte will be squeezed out to the two ends of the winding core due to the expansion of the high-energy-density cylindrical lithium battery cell after charging, and will flow back to the surface of the electrode diaphragm after standing for a period of time, thereby reducing the impedance of the cell and improving the electrochemical capacity retention rate of the cell; at the same time, the testing equipment can also be regularly repaired and maintained, saving energy consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 Schematic diagram of the cycle test number and the capacity retention rate of the cylindrical lithium battery in the high energy density cylindrical lithium battery testing method of the present invention.

[0032] Wherein: the horizontal axis represents the number of cycle tests, the vertical axis represents the capacity retention rate of the cylindrical lithium battery, the red line represents the comparative example, and the blue line represents the embodiment. DETAILED DESCRIPTION

[0033] The high energy density cylindrical lithium battery testing method of the present invention is further described in detail below.

[0034] The high energy density cylindrical lithium battery testing method of the present invention completes the test of the cylindrical lithium battery through the seven steps of constant current and constant voltage charging → transfer to standby → constant current discharge → standby → 1-4 working unit cycles → standby → 1-6 working unit cycles. The specific steps are as follows:

[0035] 1. Constant current and constant voltage charging: Place the cylindrical lithium battery on the charge and discharge test cabinet (range 5V / 10V), start the charging mode, and charge the cylindrical lithium battery with a 1C rate constant current and constant voltage (1 hour rate) until the cylindrical lithium battery voltage reaches 4.2V;

[0036] 2. Place the battery on a charge and discharge test cabinet (range 5V / 10V) for 30 minutes, or remove it from the charge and discharge test cabinet (range 5V / 10V) and place it at room temperature for another 30 minutes.

[0037] 3. Constant current discharge: Place the cylindrical lithium battery on a charge and discharge test cabinet (range 5V / 10V), start the discharge mode, and perform 1C constant current discharge (1 hour rate) on the cylindrical lithium battery to reduce the voltage of the cylindrical lithium battery to 2.75V;

[0038] 4. Place the cylindrical lithium battery on a charge and discharge test cabinet (range 5V / 10V) for 60 minutes, or remove it from the charge and discharge test cabinet (range 5V / 10V) and place it at room temperature for another 60 minutes;

[0039] 5. 1-4 range cycle: Repeat the above 4 test steps for the cylindrical lithium battery that has completed the above 4 steps, cycle the test for one month, and then stop the test;

[0040] 6. Shelf: Shelf the cylindrical lithium battery for one week, remove it from the charge and discharge test cabinet (range 5V / 10V), and shelf it at room temperature for one week;

[0041] 7. 1-6 range cycle: Repeat the above 6 test steps for the cylindrical lithium battery that has completed the above 6 steps. Stop the test after the capacity retention rate of the cylindrical lithium battery is below 80%.

[0042] Figure 1 The cycle tests shown were performed under IC / IC room temperature conditions with a voltage range of 2.75V to 4.2V.

[0043] After the 6th step of shelving for one week and then recycling the test, some of the analyzed metallic lithium can be reactivated and contribute to the capacity of the cylindrical lithium battery. The electrolyte will be squeezed out to both ends of the coil due to the expansion of the high-energy-density cylindrical lithium battery cell after charging. After standing for a period of time, it will flow back to the surface of the electrode diaphragm, reducing the cell impedance and improving the electrochemical capacity retention rate of the cell. Steps 6 and 7 are outstanding results obtained after long-term testing, which have better guiding significance for the practical application of cylindrical lithium batteries, effectively reducing the capacity attenuation of cylindrical lithium batteries, improving the energy density of cylindrical lithium batteries, extending the service life of cylindrical lithium batteries, ensuring the safety performance of cylindrical lithium batteries with high energy density, and greatly reducing the use cost of cylindrical lithium batteries.

Claims

1. A high energy density cylindrical lithium battery testing method, the specific steps are as follows: (1) constant current and constant voltage charging: place the cylindrical lithium battery on a charge and discharge test cabinet with a range of 5V / 10V, start the charging mode, and perform 1C constant current and constant voltage charging on the cylindrical lithium battery for 1 hour, so that the voltage of the cylindrical lithium battery reaches 4.2V; (2) transfer and storage: place the cylindrical lithium battery on a charge and discharge test cabinet with a range of 5V / 10V for 30 minutes, or remove it from the charge and discharge test cabinet with a range of 5V / 10V and place it at room temperature for another 30 minutes; (3) constant current discharge: place the cylindrical lithium battery The battery is placed on a charge and discharge test cabinet with a range of 5V / 10V, the discharge mode is started, and the cylindrical lithium battery is discharged at a constant current rate of 1C for 1 hour, so that the voltage of the cylindrical lithium battery drops to 2.75V; (4) Shelving: the cylindrical lithium battery is placed on a charge and discharge test cabinet with a range of 5V / 10V for 60 minutes, or removed from the charge and discharge test cabinet with a range of 5V / 10V and placed at room temperature for another 60 minutes; (5) 1-4 range cycle: the cylindrical lithium battery that has completed the above 4 steps is repeated with the above 4 test steps, the cycle test is carried out for one month, and the test is stopped; it is characterized in that (6) Shelf: Remove the cylindrical lithium battery from the 5V / 10V charge and discharge test cabinet and place it at room temperature for one week; (7) 1-6 range cycle: Repeat the above 6 test steps on the cylindrical lithium battery that has completed the above 6 steps. Stop the test after the capacity retention rate of the cylindrical lithium battery is below 80%.

Images