(1) Rated capacity: 0.5C discharge, single battery discharge time not less than 2h, battery pack discharge time not less than 108min (95%);
(2) 1C discharge capacity: 1C discharge, the discharge time of the single battery is not less than 57min (95%), and the discharge time of the battery pack is not less than 54min (90%);
(3) Low-temperature discharge capacity: 0.5C discharge at -20℃, the discharge time of a single cell or battery pack is not less than 72min (60%);
(4) High temperature discharge capacity: 0.5C discharge at 55℃, single battery discharge time not less than 104min (95%), battery pack discharge time not less than 108min (90%);
(5) Charge retention and recovery capability: fully charged and left for 28 days at room temperature, the charge retention discharge time is not less than 96min (80%), and the charge recovery discharge time is not less than 108min (90%);
(6) Storage performance: The single cell or battery pack for storage test should be selected from the production date of less than 3 months, charge 50% to 60% of the capacity before storage, at an ambient temperature of 40℃±5℃, and a relative humidity of 45 %~75% environment storage for 90 days. After the expiration of the storage period, take out the battery pack, fully charge it at 0.2C and put it aside for 1 hour, then discharge it to the final voltage at a constant current of 0.5C. The above test can be repeated for 3 times, and the discharge time shall not be less than 72min (60%);
(7) Cycle life: The battery or battery pack is charged at 0.2C and discharged at 0.5C. The test will be stopped when the discharge capacity is less than 72min (60%) for two consecutive times. The cycle life of the single battery is not less than 600 times. The cycle life of the group is not less than 500 times;
(8) High-temperature shelf life: should be selected from the single battery whose production date is less than three months for high-temperature shelf life test. Before shelving, it should be charged with 50%±5% of capacity, and then the ambient temperature is 55℃±2 Leave it under the bar for 7 days at ℃. Take out the battery after 7 days and put it aside for 2～5h at an ambient temperature of 20℃±5℃. First discharge the battery to the final voltage at 0.5C, then charge it at 0.2C after 0.5h, then let it stand for 0.5h, then discharge it to the final voltage at a constant current of 0.5C, and use this capacity as the recovery capacity. The above steps are a one-week cycle, until the discharge time of a certain week is less than 72min (60%), the test is over. Shelf life is not less than 56 days (8-week cycle).
2. Safety performance
(1) Continuous charging: The single battery is charged at a constant current of 0.2ItA. When the single battery terminal voltage reaches the charging limit voltage, it is changed to constant voltage charging and maintained for 28 days. Rupture, no fire, no explosion (equivalent to fully charged floating).
(2) Overcharge: Charge the single battery with a constant current voltage source at 3C constant current. After the voltage reaches 10V, switch to constant voltage charging until the battery explodes or catches fire or the charging time is 90min or the battery surface temperature is stable (within 45min) Stop charging when the temperature difference is less than or equal to 2℃), and the battery should not catch fire or explode (3C10V); charge the battery pack at a constant current of 0.5 ItA with a voltage-stabilizing source, and then turn after the voltage reaches n×5V (n is the number of single cells in series) For constant voltage charging, stop charging until the battery pack explodes or catches fire, or the charging time is 90 minutes or the surface temperature of the battery pack is stable (the temperature difference within 45 minutes is ≤ 2°C), and the battery should not catch fire or explode.
(3) Forced discharge (reverse charge): First discharge the single battery with a constant current of 0.2ItA to the termination voltage, and then reverse charge the battery with a current of 1ItA. The charging time is required to be no less than 90min, and the battery should not catch fire. Do not explode; discharge one of the single cells of the battery pack to the final voltage, and the others are fully charged batteries, and then discharge at a constant current of 1 ItA until the battery pack voltage is 0V, stop the discharge, the battery should not catch fire or explode .
(4) Short circuit test: The single battery is externally short-circuited for 90 minutes, or the battery surface temperature is stable (temperature difference within 45 minutes ≤ 2) to stop the short circuit, the external circuit resistance should be less than 50mΩ, the battery should not fire or explode; The positive and negative poles are connected with copper wires with a resistance of less than 0.1Ω until the battery pack voltage is less than 0.2V or the surface temperature of the battery pack is stable (the temperature difference within 45 minutes is less than or equal to 2°C), and the battery should not catch fire or explode
3. Mechanical properties
(1) Extrusion: Place the single battery in the middle of the two extrusion planes, and gradually increase the pressure to 13kN, the extrusion direction of the cylindrical battery is perpendicular to the longitudinal axis of the cylindrical axis, and the square battery extrudes the wide and narrow sides of the battery . Each battery can only accept one squeeze. The test results should meet the requirements of 4.1.2.1. Put a 15cm diameter steel rod on the battery pack to squeeze the battery pack on the wide and narrow sides of the battery pack, squeeze it to 85% of the original size of the battery pack, and hold it for 5 minutes. Each battery pack only accepts one squeeze.
(2) Acupuncture: Put the single battery in a steel fixture, and use a steel nail of φ3mm～φ8mm to penetrate from the direction perpendicular to the battery plate (the steel needle stays in the battery) for 90min, or the surface of the battery Stop the test when the temperature is stable (temperature difference within 45min≤2℃).
(3) Impact of heavy objects: Place the single battery on a rigid plane, and place a steel rod with a diameter of 15.8mm in the center of the battery. The longitudinal axis of the steel rod is parallel to the plane, so that the weight of 9.1kg is from 610mm. The height freely falls on the steel rod in the center of the battery; when the single battery is cylindrical, the impact direction is perpendicular to the longitudinal axis of the cylindrical surface; when the single battery is square, it must hit the wide and narrow sides of the battery, each battery Can accept an impact.
(4) Mechanical shock; the battery or battery pack shall be rigidly fixed (this method can support all fixed surfaces of the battery or battery pack) to fix the battery or battery pack on the test equipment. Withstand an equivalent impact in each of the three mutually perpendicular directions. At least one direction must be perpendicular to the wide surface of the battery or battery pack, and each impact shall be carried out as follows: in the first 3ms, the minimum average acceleration is 735m/s2, and the peak acceleration should be between 1225 m/s2 and 1715 m/ s2.
(5) Vibration: Mount the battery or battery pack directly or through a fixture on the vibrating table for vibration test. The test conditions are the frequency of 10Hz～55Hz, the acceleration of 29.4 m/s2, the number of frequency sweep cycles in each direction of XYZ is 10 times, and the frequency sweep rate is 1oct/min.
(6) Free fall: Drop the single cell or battery pack from a position with a height of 600mm (the lowest point height) onto a 20mm thick hardwood board on the concrete floor, once in each of the three directions, XYZ. After the free fall is over.
4. Environmental adaptability
(1) High-temperature baking: Put the single battery into a high-temperature explosion-proof box, heat up to 130°C at a heating rate of (5±2°C)/min, and keep it at this temperature for 10 minutes.
(2) High-temperature storage: Place the single cell or battery pack in an oven at 75±2℃ for 48h. The battery should not leak, leak, burst, fire, or explode.
(3) Low air pressure: (UL standard).
The requirements of lithium batteries for each component material are mainly as follows:
1. Requirements for positive and negative materials
• The positive electrode potential is over positive, the negative electrode potential is more negative
• High activity (fast response)
• The active material should be stable in the electrolyte and the autodissolution rate should be low
• The active material should have good conductivity and low resistance
• Easy to produce, rich in resources
2. Selection of conductive agent
• Excellent electrical conductivity
• Stable chemical composition, low water absorption, easy to store
• Easy to use
The best conductive agent on the market is Japan’s Ketjenblack (Ketjen superconducting carbon black) series of super conductive agents, such as Ketjenblack ECP and Ketjenblack ECP600JD. Most Japanese manufacturers use this conductive agent. Ketjen superconducting carbon black is mainly supplied by Shanghai Trico Chemical Technology Co., Ltd.
3. Requirements for electrolyte
• High conductivity, good diffusion efficiency, low viscosity
• Stable chemical composition, low volatility, easy to store
• The positive and negative active materials can remain stable for a long time in the electro-hydraulic
• Easy to use
Current outstanding problems of electrolyte
• Compatibility with positive and negative poles.
• As the voltage rises, the electrolyte solution decomposes to produce gas, which increases the internal pressure, resulting in damage to the battery's air disaster and low oxidation resistance of the solvent when the battery's operating temperature is increased.
4. Requirements for the diaphragm
• Have good stability
• Has a certain degree of mechanical strength and resistance to bending, and has the ability to resist dendrite penetration
• Good water absorption, pore size and porosity meet the requirements
• Easy to use
5. Requirements for the shell
• It has high mechanical strength and can withstand general shocks
• Has the ability to resist process corrosion