Research on low temperature in winter -- exploration on low temperature resistance of power battery

Takeaway: low temperature is an obstacle to promote electric car in north cold area in our country, and is also a trial for power battery enterprise. Conquering power battery problem of low temperature resistance has been one of the important efforts in the direction of the industry.

In winter, the people of self-mockery "freeze dog" wrapped tight coat, trying to keep the wind moves a temperature. The most embarrassing thing is, when you want to drive cars like the ancient imperial time travel with the wind, the electric car "strike"! In winter, power battery desire for the warm, as people surround furnace heating in the snow.

Low temperature is the electric car, north cold area in our country and so on to promote an obstacle, is a trial to power battery enterprise, good low temperature resistance of conquering power battery problem, has been one of the important efforts in the direction of the industry.

The influence of microscopic look at low temperature of power battery

Why a lot of power battery to the winter is not it? In low temperature environment, its internal what exactly happened?

The most used in electric buses lithium iron phosphate batteries as an example, the battery safety, monomer life longer, but the low temperature performance of battery slightly less than that of the other technical system. Low temperature of the lithium iron phosphate anode, electrolyte and adhesive is exist. For example, the lithium iron phosphate anode itself with poor electronic conductivity, low temperature environment prone to polarization, to reduce the battery capacity; Affected by low temperature, graphite intercalated-li reduced speed, easy to precipitate in the cathode surface metal lithium, if suspended in lack of time and put into use after charging, lithium metal couldn't embedded inside the graphite again, all part of the cathode surface, the persistence of metallic lithium dendrite formation, likely affect battery safety; Low temperature environment, electrolyte viscosity increases, lithium ion migration resistance will also increase; In addition, in the production process of lithium iron phosphate, bonding agent is a very key factor, low temperature also can produce great influence on the performance of the adhesive.

Another of the problems of low temperature, reflected in the client's charging time extended. Under the low temperature charging, lithium battery easy to analyse, so before charging, typically slow heating, the battery and battery temperature to normal temperature before charging.

Multidimensional attack resistance to low temperature problem

For solving the problem of low temperature of the battery, usually from batteries, batteries, design and PACK to create three aspects, to improve lithium ion batteries charge and discharge performance at low temperature and cycle life. Thornton, new energy research and development department MiaoLi filial piety to the battery, general manager of China power battery resistance to low temperature solution are introduced.

At present, the auto power battery common cathode material is given priority to with three yuan and the lithium iron phosphate, can by reducing particle size, using nanometer technology makes a nano particles of material, so as to shorten the lithium ion migration path; lithium iron phosphate by doping La element symbol of lanthanum (La), and Mg, increased C axis, change the layer spacing, increase the lithium ion transport channel; Sliding surface coated in three yuan LBO - S fast ion conductor (also known as super ionic conductor, sometimes also called solid electrolyte, it is different from general basic characteristics of ionic conductors, which in a certain temperature range can have compared to liquid electrolyte of ionic conductivity), in order to reduce the formation of SEI, lithium ion transmission can be directly through the fast ion conductor in and out of the material ontology.

For anode materials, existing graphite anode materials can be coated, surface oxidation, doping or any other element cladding, to increase the graphite layer spacing, accelerate the desolvation of lithium ions in the cathode surface speed, improve lithium ion embedded the speed of the graphite anode. MiaoLi filial piety, said the development of new type anode materials such as lithium alloy, tin base, can greatly improve the low temperature performance of lithium-ion batteries.

Electrolyte consists of lithium salts, solvents and additives, three parts. About MiaoLi filial piety, lithium, boric acid salt may be added, helps to form a stable SEI film in the material surface, and is advantageous to the lithium ion diffusion; About the solvent, can through the allocation of a reasonable proportion, improve the low temperature performance of electrolyte solvent; About additives, by adding different additives, the low temperature properties of the battery has a different effect. Learned, new energy has a dedicated team of Thornton, focus on electrolyte formula research and development, in order to solve the problem of low temperature of power battery. At present, Thornton, new energy development ternary lithium battery, its low temperature resistance has greatly improved, batteries can be 20 ℃ below zero to devolve electricity environment, can meet the demand of the electric car run in a cold environment.

In addition, great energy power battery can be - 20 ~ 60 ℃ environment, and do not need heating and cooling systems. Shandong power is one specialized is engaged in military low temperature lithium iron phosphate battery research and development, production of high-tech enterprises, with the Chinese academy of sciences (htma cooperative research and development, the production of lithium iron phosphate batteries achieve breakthrough performance under low temperature and at low temperatures to 40 ℃ to emit more than 90% of the rated capacity.

Promotion of new energy vehicles is low temperature challenges but also opportunities

As one kind of lithium-ion batteries, titanium acid lithium battery low temperature resistant performance is more outstanding. Spinel structure of anode materials for lithium titanate intercalated-li potential 1.5 V, not lithium dendrite formation, in the process of charging and discharging volume strain is less than 1%.Nano titanium acid lithium batteries can be large current charge and discharge, realize the low temperature quick charge at the same time guarantee the durability and safety of the battery.

Cells created in the latest news, November 28, 2017, in this cold season, silver long new energy production of pure electric bus in the northern city of Tianjin was put into operation, this once again highlights the silver long new energy titanate excellent resistance to low temperature performance of lithium-ion batteries. Main new energy of lithium titanate battery of silver, its products have in - 50 ~ 60 ℃ temperature range of the normal charge and discharge capacity, the company production of bus has been in Harbin, Yinchuan, Tianjin, Shijiazhuang, Baoding, Handan and so on more than 40 cities across the country implements the commercialized operation, low temperature resistant effect is good. Lithium titanate battery because of its excellent resistance to low temperature performance, in the cold region in China become the vanguard of the promotion of new energy vehicles, silver long new energy is lithium titanate battery to spark a wider market.

On July 31, 2017, at the launch in Beijing Yanqing district electric bus operation, 50 vehicles carrying micro macro power quick charge battery system of pure electric bus delivery Beijing bus group and put into operation. The delivery of the 50 pure electric bus with micro macro power production quick charge battery, high energy density, long range. At this point, the micro macro power market in Beijing has more than 10 vehicles of all kinds of public transport vehicles. On September 19, 2017, 70 vehicles with micro macro MpCO lithium battery of 12 meters gas-electric hybrid bus officially launched in Inner Mongolia baotou. The region's lowest temperature below 30 ℃, the highest temperature can reach 39 ℃, baotou choose micro macro quick charge battery system, it is considering micro macro quick charge battery good environmental adaptability. Micro macro power bus market in cold areas develop in full swing, it is also the industry to explore power battery is a typical representative of the resistance to low temperature technology.

Solve the problem of low temperature resistant still needs technical drivers

Power battery problem in low temperature, and there are many solutions, for example, the so-called "battery" climate, across the electrodes in the join between the heating pills, through the switch control circuit, implement for heating of the battery. Within the heating efficiency is much higher than that of external heating, and use less energy. All batteries in the battery life, charging time and climate has significantly improved the service life.

From micro level for solving the problem of low temperature of power battery, such as from the battery materials, low temperature resistant problems still need to rely on the technology-driven, seize the battery "afraid of" low temperature, suit the remedy to the case, this solution is more thorough.

At present, a lot of ternary lithium battery also has the characteristics of the low temperature resistant, titanate is more resistant to low temperature performance of lithium-ion batteries, electric cars, promotion of bottleneck will be gradually solved in low temperature.

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