Winter endurance anxiety power lithium ion battery low temperature and thermal management potential is huge

　　Author ：Iflowpower – Portable Power Station Supplier

Million new car welcomes winter life test, winter road testing is 24%. In 2018, the country completed the new energy passenger car sales of 108,000, up 89% year-on-year; sales of 143,000 units were completed in January-February, up 134% year-on-year; but winter road experiments showed that the number of uniform and continued navigations of 8 models were 24. %, Lithium cobalt organte containing lithium, three-dimensional lithium and lithium iron phosphate do not have a distinctive anti-low temperature advantage, low temperature and heat management will huge in the future market potential.

High temperature heat management has been attached, low temperature and heat management technology routes more. Due to the summer's 40 battery spontaneous combustion incidents, many manufacturers have begun to pay attention to high temperature and heat management, and low-temperature heat management is still waiting to be developed, only a few manufacturers are equipped with electric heating systems for the battery; winter life is a passenger experience At the core indicator, the low temperature performance of the battery is the core competitiveness of battery manufacturers. Every winter, low-end life will cause manufacturers to accelerate the penetration of low temperature and heat management, and the market potential is huge in the future.

Low temperature, electrochemical reaction is not active is a tight source for battery winter electricity reduction. When the ambient temperature is too low, the viscosity of the electrolyte is even partially solidified, so that the lithium ion deinterlamps are blocked, the conductivity is lowered, and the capacity is reduced. Use a lithium ion battery using a lithium ion battery, which is easy to cause irreversible capacity damage to the battery, and form potential dangers.

Compared with NCA, lithium iron phosphate, China's desired battery development direction NCM811 low temperature performance is relatively strong, high-nickel trend helps slow down the low power of winter. R & D low-temperature battery is the fundamental approach to the decline in winter, high-efficiency thermal management is the current most feasible winter life management method. At present, there is an electrolyte modification and all-weather battery in the lower temperature battery.

The mixed electrolyte can be integrated with various types of electrolyte advantages to strengthen lithium-ion batteries, and all-weather battery technology is recognized by BMW to lead the market. Current liquid cooling management technology penetration is compared to a large improvement in last year, it can make low temperature and heat management by reverse heating coolant, and there are many models in the market to achieve low temperature heating function. First, how much winter electric car endurance is reduced? -24% million new car welcomes winter life test, low temperature and heat management can be.

In 2018, there were 1008,000 units in the whole year of new energy passenger vehicles, up 89% year-on-year; 143,000 sales were completed in January-February, 134% year-on-year. However, the new energy car in the winter, especially in the high-precipitation, the actual life of the electric car, which has already declined, which has caused serious impact on the user. Take a few typical new energy vehicles as an example.

Some winter road experiments show that the uniform and continued navigation miles of these models fell by 24%. The lithium cobalt organte contained, and the three-dimensional lithium and lithium iron phosphate did not have a distinctive anti-low temperature advantage. Due to 40 battery self-ignition events last year, many manufacturers have begun to pay high temperature and heat management, while low-temperature heat management potential is still needed, only a few manufacturers are equipped with electric heating systems for batteries.

Winter life is the core indicator of the passenger experience of the vehicle. The low temperature performance of the battery is the core competitiveness of the battery. We believe that every winter low-end life will cause the manufacturer to accelerate the penetration of low temperature and heat management, and future market potential is huge.

The lower the battery test, the lower the battery available capacity. Take the Panasonic NCR18650A as an example, the battery capacity will drop by about 20% compared to 25 ¡ã C in the battery test, and the uniform voltage is lower than normal temperature, and the battery is differential. The lithium phosphate ion battery is taken as an example, and the internal resistance of the battery is 4-5 times at 15 ¡ã C, and the electrolyte conductivity is severe.

The use of heating equipment in winter cars is increased. At present, the PTC heater is a desirable heat source of electric vehicle heating air conditioners, which has risen from 70% to 98% compared to the electric wire heating energy, but the high-grade power pen is converted into low-grade thermal energy, and energy waste is still huge. It is equipped with 2 PTC heaters such as the first 5.

5kW after ES8. Endurance can only complete half. Theoretical measurement of heating power consumption serious restrictions.

Take the 35KWH battery with the current mainstream as an example to obtain the heating power consumption and the mileage correlation curve. To ensure the 75% endurance retention rate, the internal and uniform heating power consumption is controlled to 1-1.5KW.

However, the electrothermal conversion efficiency is up to 1, and the efficiency of the PTC heater is very close, so it is necessary to find a technique such as transformation efficiency such as heat pump air conditioning. Second, the original price of lithium-ion battery in winter, low temperature electrochemical reaction is not active, low temperature, electrochemical reaction is not active is a tight source for battery winter life. Lithium ion battery is a typical "rocker battery", which is charged, and the lithium ions enter the negative electrode from the positive electrode to enter the negative electrode, so that the negative electrode is a lithium state, the positive pole is positive, and the carbon negative electrode obtains compensation charge through the external circuit.

, Reverse when discharging. When the ambient temperature is too low, the viscosity of the electrolyte is even partially solidified, so that the lithium ion deinterlamps are blocked, the conductivity is lowered, and the capacity is reduced. Using lithium-ion batteries in low temperatures to cause irreversible capacity damage and potential dangers.

The solubility of lithium ions will be significantly reduced at low temperatures, which can be deposited to form a lithium crystal graft. When grown to a certain extent, it may pierce the diaphragm caused battery short circuit to form potential security risks. And at this time, the electrode dynamic conditions of the battery are poor, the solid electrolyte interface (SEI) thickness will increase, will continue to hinder ion flow, resulting in effective capacity attenuation.

The anti-low temperature resistance of all kinds of positive electrode materials is different, and the NCM811 battery is relatively frozen. The capacity retention ratio of the battery at -20 ¡ã C is decreased, and the NCM material is similar to the NCA material, and the NCM811 is slightly higher than NCA, but both are all better than the lithium iron phosphate ion battery. The current domestic battery development trend helps slow down the phenomenon of winter low power, but still low temperature control to make the battery in the best range.

Third, low-temperature continuity, high-efficiency thermal management, low temperature battery research and development is a method of dealing with the decline in winter, and there is a modified electrolyte and all-weather battery in the direction of the direction, but currently in the test stage. Hybrid lithium salt, solvent and additive obtain a high-temperature electrolyte with strong comprehensive performance, is a desire to obtain a low temperature lithium-ion battery. The electrolyte is one of the most important factors in battery resistance, and the current research statement will mix different lithium salts, solvents and additives.

Mix the best results in a particular proportion. For example, in the solvent, the conventional solvent EC dielectric constant is high, the film formability is good, but the PC solvent having a high melting point, large viscosity, and low melting point (-48 ¡ã C) can effectively prevent the electrolyte system from being solidified at low temperatures. Adjusting the ratio of the two, the resistance of the system, obtaining the anti-low temperature solvent of the combined advantage.

All-weather battery is an optional option in the battery. In 2016, the Chinese team of ECPOWER and Pennsylvania State University has developed a lithium-ion battery that can be used under low temperature conditions. It can achieve low temperature automatic heating by the circuit design in the internal addition of electrometrium foil, which can be used within 25 seconds.

Temperature from -20 ¡ã C to 0 ¡ã C and maintain stability. This all-weather battery is square, and the addition cost is less than 1 yuan per kilowatworm. The additional weight does not exceed 1.

5%, and the capacity attenuation at 20 ¡ã C is only half of the general battery. BMW announces the patent agreement with Ecpower in 18 months, which is very likely to use the technology to use the future BMW pure electric vehicle type. We believe that the all-weather battery with self-heating function is one of the future options, but reliability, heating power consumption and circuit control are still handled.

High-efficiency thermal management is the current most feasible winter life management method. Design of battery heating system at low temperature is a complex project. If only from the maximum ending angle, the battery heating system is the optimal solution to keep the battery at a particular temperature, but from the battery safety angle, take a battery heating system below 0 ¡ã C to maximize battery life.

In addition, the battery heating is necessary to fill in the heat insulation material in the battery pack, but this is in the need for high temperature heat management, so the design of the thermal management system should consider various factors. Battery heating system has a variety of methods, and the feasibility of liquid cooling heat system is highest. At present, the battery heating system has PTC heating, electric heat film heating, phase change heating, cooling liquid heating, heat pipe heating, communication heating and other implementations.

At the end of 2017, the battery preheating function was upgraded in the OTA system. The patent showed a variety of heating strategies, which can conduct all-weather battery thermal management at different working conditions, different heating media, and different heat sources. However, from its dismantling map, it is also the use of PTC heating coolant, which is the current most logical choice, which can handle the contradiction of high and low temperature management, while transforming is more convenient, only in high temperature fluid cooling New heat source on the basis of thermal management.

Many models have low temperature and heat management system, battery liquid cold heating system commends. At present, most new energy vehicles have been equipped with battery heating systems, but PTC-based warm air heating system is less efficient. Other than Testra, the model of the equipment liquid cooling system is equipped with a battery coolant heating system, which has become a tight product selling point, which has become a tight product selling point.

Improve, the cooling solution heating function will continue to penetrate. Heat pump air conditioners can be efficient energy efficient in winter. The actual COP when the heat pump is hot, can reach 2-4, that is, the heat of the same energy consumption is 2-4 times the PTC.

At present, there have been Roewe EI5 and MarvelX equipped with a heat pump air conditioning system to ensure high efficiency heat in winter. Typical electric vehicles with 300km charge 35 kW are used as an example to calculate, PTC, heat pump air conditioning, and the combination of two methods formed by using only heat pump air conditioners, only 14% of the use of only PTC heating. Mileage, energy saving effect is very.