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As a power battery, iron phosphate lithium battery and lithium-ion battery, who is your first choice?

2019-07-11

Battery technology is a great invention with a wonderful and long history, and battery English "Battery" first appeared in 1749, it was first used by American inventor Benjamin Franklin, when he used a set of series of capacitors for electrical experiments.

In 1786, the Italian anatomist Gavani in the frog anatomy, found biological electricity, and published in academia, in 1800, voges were inspired by the Gavani frog experiment, using copper, tin, salt water for the material successfully manufactured voodoo batteries, in 1836, the British Daniel to the "volt reactor" to improve.

He solved the battery polarization problem by using dilute sulfuric acid as an electrolyte, creating the first zinc-copper battery, also known as the "Daniel battery", that was not polarized and maintained a balanced current

In 1860, France's Plante invented a battery that uses lead as an electrode, a precursor to the battery, while France's Reclans invented carbon-zinc batteries, bringing battery technology to dry-battery.

The commercial use of battery technology began with dry batteries, which were invented by the British Helleson in 1887 and mass produced in the United States in 1896, while Thomas Edison invented rechargeable iron-nickel batteries in 1890 and commercialized mass production in 1910.

Since then, with commercial driving, battery technology has ushered in an era of rapid advances, with Thomas Edison inventing alkaline batteries in 1914, Schlecht and Akermann inventing nickel-cadmium battery sintering plates in 1934. Neumann developed sealed nickel-cadmium batteries in 1947, and Lew Urry (Energizer) ushered in the era of alkaline batteries in 1949.

After entering the 1970s, battery technology by the impact of the energy crisis, gradually to the direction of physical power direction, in addition to the solar cell technology in 1954 has been the continuous progress, lithium batteries and nickel hydride batteries have been gradually invented and commercial applications.

Second, the battery capacity is different

In the case of new batteries, the battery capacity is tested with a discharge meter, the capacity of the general power battery is about 1000-1500mAh, at this stage, the capacity of the power battery can reach more than 200Ahwhile the capacity of ordinary batteries is more than 2000mAh, some can reach 3400mAh.

A 4200mAh power battery can light up in just a few minutes, but a normal battery simply can't do it, so the discharge capacity of a normal battery can't be compared to a power battery. The biggest difference between a power battery and a normal battery is that it discharges with more power than energy. Because the main use of power batteries for automotive energy supply, it has higher discharge power than ordinary batteries

Fourth, the application is different

Batteries that power electric vehicles are called power batteries, including conventional lead-acid batteries, nickel-hydrogen batteries, and emerging lithium-ion-powered lithium batteries, divided into power-powered batteries (hybrid vehicles) and energy-powered batteries (pure electric vehicles); Lithium batteries used in consumer electronics such as laptops are commonly referred to as lithium batteries, and are distinguished from power batteries used in electric vehicles.

The main types of power batteries

At present, mainstream technologies on the market still focus on lead-acid battery technology, nickel-hydrogen battery technology, fuel cell technology, and lithium-ion battery technology.

Lead-acid batteries

Lead-acid batteries have the longest history of application, the most mature technology, is the cost, the lowest price of the battery, has achieved mass production. One of the valve-controlled sealed lead-acid battery (VRLA) has once become an important automotive power battery, used in many European and American car companies developed EV and HEV, such as GM in the 1980s and 1990s, respectively, developed The Saturn and EVI electric vehicles.

However, lead-acid batteries have lower energy, short battery life, high self-discharge rate and low cycle life, and their main raw materials are large in weight, and may produce and recycle heavy metals in the process of environmental pollution. Therefore, the current lead-acid batteries are mainly used in the ignition when the car starts, as well as electric bicycles and other small equipment.

NiMH batteries

Ni-mh battery has good resistance, over-release capacity, there is no heavy metal pollution problem, and in the course of work will not appear electrolyte increase or decrease phenomenon, can achieve seal design, maintenance-free. Compared with lead-acid batteries and nickel-cadmium batteries, nickel-hydrogen batteries have higher energy, power and cycle life.

The disadvantage is that the memory effect of the battery is poor, and with the charging and discharge cycle, the hydrogen storage alloy gradually loses the catalytic ability, the internal pressure of the battery will gradually increase, affecting the use of the battery. In addition, the high price of nickel also leads to higher costs.

On the key materials, nickel-metal hydride batteries are mainly composed of a positive electrode, a negative electrode, a separator and an electrolyte. The positive electrode is a nickel electrode (Ni(OH) 2 ); the negative electrode is generally a metal hydride (MH); the electrolyte is mainly a liquid, and the main component is hydrogen. Potassium oxide (KOH). At present, the research focus of nickel-hydrogen battery is mainly on the positive and negative materials, and its technology research and development is relatively mature.

The nickel hydride battery for automobile has been mass produced and used, and it is the most widely used type of car battery in the development of hybrid vehicle. The most typical representative is the Toyota Prius, which is currently the largest producer of hybrid vehicles. PEVE, a joint venture between Toyota and Panasonic, is the world's largest manufacturer of nickel-hydrogen powered batteries. Now that nickel-hydrogen batteries are out of the mainstream, why would Toyota stick to the nickel-hydrogen battery camp?

This has to say the biggest advantage of NiMH batteries: superior durability!

Consumer Reports, once america's leading automotive media, compared a first-generation Prius after a decade of use. Test results show that the first-generation Prius models with NiMH batteries, after 10 years of driving 330,000 kilometers, compared them with the data of new vehicles, both in terms of fuel consumption and power performance, indicating that the mixing system and the nickel hydride battery pack are still working correctly.

Moreover, even after a decade of running 330,000 kilometers, the first-generation Prius's nickel-hydrogen battery pack never had a problem, and the question a decade ago that the decay of battery capacity would significantly affect fuel consumption and power performance did not occur. From this point of view, the traditionally strict conservative Japanese love of nickel hydride batteries does have its own unique reasons.

The fuel cell

A fuel cell is a power generation device that converts the chemical energy present in fuel and oxidants directly into electrical energy. Fuel and air are sent to fuel cells, and electricity is produced. It looks like a battery from the outside, like a battery, but in essence it can't "store electricity" but a "power plant".

Compared to conventional chemical batteries, fuel cells can be used to replenish fuel, usually hydrogen. Some fuel cells can use methane and gasoline as fuel, but are usually limited to industrial sectors such as power plants and forklifts. The basic principle of hydrogen fuel cell is the inverse reaction of electrolytic water, which supplies hydrogen and oxygen to the anode and cathode respectively, and the hydrogen emits electrons to reach the cathode through an external load after the anode diffuses outwardand and reacts with the electrolyte.

Hydrogen fuel cells work: Hydrogen is sent to the anode plate (negative pole) of the fuel cell, and by a catalyst (platinum), an electron in the hydrogen atom is separated, and the hydrogen ions (protons) of the missing electrons pass through the proton exchange membrane to the fuel cell cathode plate (positive), and the electrons cannot pass through the proton exchange membrane, which can only be through an external circuit, Reach the fuel cell cathode plate to generate current in the outer circuit.

Once the electrons reach the cathode plate, they are recombined with oxygen atoms and hydrogen ions into water. Because the oxygen supplied to the cathode plate can be obtained from the air, so as long as the anode plate is constantly supplied with hydrogen, the cathode plate supply air, and timely removal of water vapor, can continue to provide electricity.

Fuel cell emitted electricity, by inverter, controller and other devices, to power the electric motor, and then through the transmission system, drive bridge and other driving wheels, can make the vehicle on the road. Compared with conventional cars, fuel cell vehicles have an energy conversion efficiency of 60 to 80%, which is 2 to 3 times that of internal combustion engines.

Fuel cells are fueled by hydrogen and oxygen, and the generating material is clean water, which itself does not produce carbon monoxide and carbon dioxide, nor does it emit sulfur and particulates. Therefore, hydrogen fuel cell car is the true meaning of zero emissions, zero pollution car, hydrogen fuel is the perfect car energy!

Features of hydrogen fuel cells:

1.     No pollution: Fuel cells are non-polluting to the environment. It is through electrochemical reactions, rather than combustion (steam, diesel) or energy storage (battery) -- the most typical traditional backup power solution. Burning releases pollutants such as COx, NOx, SOx gas and dust. As mentioned above, fuel cells produce only water and heat. If hydrogen is produced from renewable sources, the entire cycle is a complete process of not producing harmful emissions.

2.     No noise: The fuel cell runs quietly, with noise of about 55dB, which is equivalent to the level of normal conversation. This makes the fuel cell suitable for indoor installation or where noise is limited outdoors.

3.     High efficiency: Fuel cells can generate more than 50% of their power efficiency, which is determined by the conversion nature of the fuel cell, which converts chemical energy directly into electrical energy without the need for intermediate transformation of thermal and mechanical energy (generators).

4.     The advantages of hydrogen fuel cell vehicles are unquestionable, and the disadvantages are obvious. With the progress of science and technology, such as safety and hydrogen fuel storage technology, which have plagued the development of hydrogen fuel cells, have been gradually overcome and continuously improved, but the cost problem is still the biggest bottleneck hindering the development of hydrogen fuel cell vehicles.

Hydrogen fuel cells cost 100 times as much as regular gasoline engines, a price the market can't afford. Behind the hydrogenation station is a set of hydrogen energy production and transportation networks as support, and the vast majority of countries in the world do not have the will and space to vigorously develop a systematization of an infrequently used energy source.

In particular, hydrogen energy has a low conversion rate and can cause pollution in energy production. On the other hand, the construction requirements and costs of hydrogenation station itself are very high, and special low-temperature equipment is needed to meet the energy storage needs. At present, only Japan, South Korea and California have more hydrogenation stations, and this more is actually dozens or so.

Entering 2017, the already quiet fuel cell car market seems to have suddenly picked up.

On the one hand, the electric vehicle battery technology upgrade, which has been high hopes, has encountered a bottleneck continuously. And the driving mileage is too short and charging time is too long these two factors still restrict the prospects of new energy vehicles.

On the other hand, fuel cell vehicles are increasingly cost-effective in many areas.

The cost of producing fuel cell vehicles, which were already high, is falling rapidly. Five-minute fuel-filled experiences and more than 500km of mileage are certainly more tempting than competing mid- to high-end electric cars.

Lithium Ion Battery

Lithium-ion power battery for automotive is developed on the basis of disposable lithium battery, which is the main direction of battery research and development for pure electric vehicles. Lithium-ion battery has many advantages such as memoryless, low self-discharge rate, environmental protection, high ratio energy, high ratio power, etc., and is the most popular potential in-vehicle battery after nickel hydride battery.

Lithium-ion battery characteristics

1.     Voltage platform

Lithium-ion batteries have a working voltage range of 3 due to the different positive and negative materials used. 7 to 4v, in which the large-scale LiFePO4 monomer battery operating voltage is 3. 2v, 3 times that of nickel hydride batteries and 2 times that of lead-acid batteries

2.     Greater than the energy

The current energy density of passenger car lithium-ion battery is close to 200 wh/kg, and it is expected to reach 300 wh/kg in 2020.

3.     Short battery life

Due to the restriction of electrochemical material characteristics, the number of lithium-ion battery cycle steam did not make a breakthrough, to lithium phosphate as an example, the number of single battery cycle can reach more than 2000 times, after group only 1000 times.

4.     The impact on the environment is greater

Lithium-ion batteries use light metal lithium, although it contains no mercury, lead, harmful heavy metals, is considered a green battery, less environmental pollution.

In fact, because of its positive and negative materials, electrolytes containing nickel, metal, the United States has classified lithium-ion batteries as a containing flammable, manganese, reactive, leaching toxic, corrosive, toxic and harmful batteries, is currently the most toxic batteries of all types of batteries, And because its recycling process is more complex, resulting in higher costs, so the current recycling utilization rate is not high, waste batteries have a greater environmental impact on the environment

5.     The cost is still high

The initial purchase cost of lithium-ion batteries is high. For example, the current price of LiFePO4 batteries for automotive power batteries is about RMB2,500 / kwh. With the popularity of electric vehicles, it is expected to be reduced to less than RMB1,000 / kwh in 2020.

Current mainstream electric vehicle representatives and their comparison of lithium-ion battery

Tesla and Panasonic - lithium cobalt oxide battery

As a global leader in all-electric vehicles, Tesla Motors, born in Silicon Valley, has made a disruptive change in its view of electric vehicles with its sharp shape, 3.2 seconds of acceleration, and more than 400 kilometers of battery life, and is fast becoming a major vehicle that challenges conventional fuel vehicles. In addition to its powerful electric motors and excellent power management technology, Tesla's ability to make a shot at the top of the company has nothing to do with its lithium cobalt battery.

Early Tesla MODEL S models used Japan's Panasonic 18650 lithium cobalt battery, which was slightly larger in size than our usual 5 dry battery, but it was the seemingly unsightly battery that, after thousands of them, was also able to unleash amazing energy.

This kind of battery we are no stranger, such as laptops and other electronic digital devices are used in this type of battery, compared to other battery types, panasonic 18650 battery as the representative of the advantages of lithium cobalt acid battery is that the technology is quite mature, higher than energy, in addition, this kind of battery discharge current, charging speed, Ideal for high-performance electric cars like Tesla.

To maximize the battery's energy density, Tesla combines these single 3,100mAh 18650 lithium batteries into a small "battery box" unit, which is then further stitched together to form a whole power battery pack. The ultimate total of 8,142 18650 batteries combined with a battery pack of more than 85 kWh, ensuring the Tesla MODEL S's range of more than 400 km.

Tesla's high-density battery combination brings considerable total battery capacity, but the poor thermal stability of lithium cobalt batteries, combined with the placement of integrated panels in the vehicle's chassis position, places higher demands on battery cooling and safety. To do this, Tesla had to design sophisticated battery protection procedures and a unique liquid-cooled cooling system to keep the battery pack working properly.

This aspect not only increases the body quality, the vehicle's range has a certain impact, of course, the most obvious is to invisibly push up the cost of manufacturing the vehicle, so Tesla sold such a price is also a reason.

• BYD and LiFePO4 battery

About LiFePO4 batteries, we must say that by THE domestic largest new energy vehicle company BYD. Starting with lithium cell phone batteries, the company has grown into a large integrated enterprise that covers battery manufacturing, traditional and new energy vehicle manufacturing. Iron phosphate is the core product and is equipped with most of BYD's models.

LiFePO4 battery belongs to the lithium-ion secondary battery (using lithium phosphate (LiFePO4) material as the positive battery, it discharges more efficient, the price is more advantageous than other lithium batteries. In the early years, the E6 electric vehicle with BYD's "iron battery" successfully opened up the domestic electric vehicle market for BYD, and its investment in the Shenzhen taxi market by BYD E6 electric vehicles was also a great success.

As one of the world's first companies to realize the industrialization of LiFePO4 batteries, BYD used this kind of LiFePO4 compared to the early lithium manganese acid lithium battery, although the energy density is not much different, but its thermal stability is currently the best of the power lithium battery.

When the battery temperature is at a high temperature of 500-600 degrees C, its internal chemical composition begins to decompose, and punctures, short circuits, high temperatures do not burn or explode, and compared to the above-mentioned Panasonic lithium cobalt acid lithium battery (180-250 degrees C when the internal chemical composition is already unstable), obviously, Iron phosphate lithium batteries are more secure.

In addition to higher safety, the life of LiFePO4 batteries also has certain advantages. From the Shenzhen taxi market into operation of by dying BYD E6 use effect, these since 2010 began to operate 850 E6 electric taxi cumulative total mileage has exceeded 300 million kilometers, of which the maximum mileage of the bicycle more than 670,000 kilometers, these vehicles are still running well, which also shows the reliability of LiFePO4 battery. This result also makes BYD E6 the largest model in China's electric taxi market.

However, in addition to the outstanding advantages of thermal stability, iron phosphate lithium battery energy density than the triple lithium battery and lithium cobalt acid battery still has a small gap, the same battery capacity, iron phosphate lithium battery weight is heavier, the volume is also larger, which also led to the use of the battery type of vehicle range performance in general.

Of course, the biggest pain point of LiFePO4 battery is the charging problem at low temperature. When the temperature is lower than -5 °C, the charging efficiency is low, which is not suitable for the charging demand of northern new energy vehicle owners in winter, which has become the latest BYD. The important reasons for the hybrid models Tang 100 and Qin 100 to temporarily use the ternary lithium battery.

• The most widely used ternary lithium battery

NCM Battery as the name implies that the battery refers to the positive material, in addition to lithium, there are nickel cobalt manganese, or nickel cobalt aluminum three metals. Compared with LiFePO4 and lithium cobalt acid lithium battery, the comprehensive performance of the NCM Battery is more average, the energy density is not low, the volume is higher than the energy, and the price is relatively reasonable and therefore adopted by more and more new energy vehicle manufacturers.

As a new product that has emerged in the last two years, the advantage of the NCM Battery is that it has the advantages of high energy density, long cycle life, and the advantages of vehicle light weight to improve the vehicle range is very helpful. In addition, the more important reason is that with the increase in production capacity, the price of three-way lithium batteries has also been further reduced, precisely because of these reasons led to domestic car companies passenger cars have turned to the use of three-way lithium batteries.

To say the disadvantage of the teratosis lithium battery, that is, the deoxygenation temperature of the teratosis material is 200 degrees C, the heating energy is more than 800J/g, and can not pass the needle test. This shows that the three- battery in the internal short circuit, battery casing damage, it is easy to cause combustion, explosion and other safety accidents.

It is for safety reasons that the state has suspended the use of three-way lithium batteries on commercial models. However, with the progress of technology, especially after the application of ceramic diaphragm, the safety of the NCM Battery has been improved and solved. As far as the current market situation, because the comprehensive advantages of the NCM Battery is still relatively obvious, the car manufacturers' concern for the NCM Battery is also increasing.

New Battery Technology Preview - Physical Battery

The physical battery is a general term for batteries that rely on physical changes to provide and store electrical energy. For example, "supercapacitors with instant full charge" and "flywheel batteries with a power of 5000-10000 W/kg" are members of the physical battery family.

•        Super capacitor

Supercapacitor is a power supply between a conventional capacitor and a battery with a power density of 300-500W/kg, 5-10 times that of a normal battery. It mainly relies on the double electron layer and redox false capacitive charge to store electrical energy, during which there is no chemical reaction, so it is classified as a physical battery.

Compared to chemical batteries, supercapacitors have three distinct advantages:

1. Repeated charging and discharging times of 100,000 times (traditional chemical batteries are only a few hundred to several thousand times), and the life expectancy is much higher than that of chemical batteries;

2. The super capacitor has a very high power density during charging and discharging, and can release a large amount of electric energy in an instant, which can meet the broader power demand of the vehicle;

3, the working environment adaptability is better, usually when the outdoor temperature is between -40 ° C ~ 65 ° C, it can work normally (the traditional battery is generally -20 ° C ~ 60 ° C).

• Flywheel battery

Flywheel batteries are a new concept battery introduced in the 1990s, which is charged and discharged using a principle similar to the energy generated when the flywheel rotates.

The famous Porsche 911 GT3 Hybrid And the Porsche 918 Spyder, named one of today's four god cars, are fitted with flywheel batteries on both front wheels, which convert the kinetic energy collected by braking into electricity and store energy in a flywheel. During acceleration, this energy is transferred to the front wheels, increasing acceleration while reducing the fuel consumption of the combustion engine.

Due to technology and material price constraints, the price of flywheel batteries is relatively high, in small occasions can not reflect its advantages. But in space, mass transportation, and military-wide situations where large-scale energy storage devices are needed, flywheel batteries have been gradually used.

With the development of new energy vehicles, batteries as one of the important components, energy density is increasing.

The key to the battery revolution is the material, the teratoum material will become the mainstream positive material system, graphite and soft carbon, hard carbon and other negative material shove material mixing application with different characteristics will also become the mainstream system of negative materials.

In addition, graphene in China has begun to enter the mid-term test stage, the amount of post-partum will greatly improve the energy density level and life of the battery.

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