The contrast of hydrogen fuel battery and lithium-ion battery

The analysis of the hydrogen fuel battery and the lithium battery

While countries are vigorously promoting electric vehicles in recent decades, but the proportion is still very low, less than 1%, the core is the energy density of electric cars are in violation of the ascending the energy change of logic. Even the latest generation of lithium battery car, the extreme value of its energy density is only 1/40 of the gasoline. The industry has been slow to appear 10 times the speed of improvement. But the emergence of the fuel cell has changed all that. It is based on hydrogen as raw material, the energy density is 3 times of gasoline, and the work efficiency of motor is 2 times that of the internal combustion engine, the actual density is 6 times that of the gasoline, obvious advantages. And energy from the past one hundred years of human evolution, its essence is the history of hydrocarbon ratio adjustment, the higher the hydrogen content, the higher energy density. In the future, it is an inevitable trend to change from carbon energy to hydrogen energy. Therefore, fuel cells using hydrogen energy can undoubtedly represent the direction of historical development and most likely become the next generation of basic energy.

Vehicle performance mainly includes endurance, charging/hydrogen charging time, output power and safety, etc. Fuel cell energy density is much higher than that of lithium batteries, battery capacity, quick charge capacity and range have a natural advantage, even with the top luxury cars of lithium-ion batteries is also a big lead than Tesla. But its power density is not high, the maximum output power depends on the auxiliary power battery system, and the corresponding highest and best kilometers per hour speed index and lithium battery. For comparison, we selected below the current mainstream 2 l from gasoline vehicles, corresponding to 45 degrees of lithium battery and the output power of 100kw fuel cell vehicles as the benchmark.

Energy density comparison

As a kind of storage battery, lithium-ion batteries is a closed system, the battery is the carrier of energy, to charge in advance to run, the energy density depends on the energy density of the electrode materials. Due to the energy density of the cathode material is greater than the positive, so to improve the energy density is escalating the anode materials, such as from lead acid, nickel, and then to lithium battery. But lithium is atomic weight minimum metal elements, theoretically better than lithium ion battery anode materials is only pure lithium electrode, but the fact is that the energy density is only 1/4 of gasoline, and commercialization of technical difficulty is great, a few decades is no breakthrough. Therefore subject to the lithium battery energy density ascension theory bottlenecks, space is very limited, at most, that is, from the current 160wh/KG to 300wh/KG, even at only 1/120 of the fuel cell, is lose in the starting line.

Volume energy density comparison

The main disadvantage of raw hydrogen in fuel cells is its low volume and energy density. According to the current pressurization model of 700 atmospheres, its volume energy density is 1/3 that of gasoline. The fuel cell hydrogen storage tank is 100L in volume and 30KG in weight, corresponding to 30L in gasoline car fuel tank. However, the motor is 80L smaller than the internal combustion engine, and the overall volume difference is not significant. Lithium battery vehicles are divided into two main technical routes: ternary and lithium iron phosphate. Representative companies are Tesla and BYD. Ternary energy density is higher, but the safety is poor, which requires auxiliary safety protection equipment. The two types of batteries required for 300km are 140L and 220L in volume and 0.4t and 0.6t in weight, both much higher than fuel cells. Looking ahead, if hydrogen storage alloys and cryogenic liquid hydrogen storage technologies can be breakthrough, fuel cell volume and energy density will increase by 1.5 times and 2 times respectively, and the advantages will be more obvious.

Power density comparison

The fuel cell can be understood as a chemical power generation system using hydrogen as a raw material, so the output power is relatively stable. In order to maximize the discharge power, a power battery system must be added. For example, Toyota Mirai is a supporting nickel-hydrogen battery. However, as an open power system, its energy comes from external input. The additional Ni-MH battery does not need to consider the problem of energy storage. As long as it is 5-8 degrees, it can meet the demand and the battery life is not high. There are few restrictions on use. Although the theoretical discharge efficiency of lithium batteries is very high, in order not to damage the battery life, there are many restrictions on use. In the case of full charge, it cannot be discharged at a large rate, and the rapid discharge is only applicable to the interval of 0-80%. Even so, with a 5C rate discharge, the battery cycle life in the laboratory will be shortened to only 600 times, and will be further reduced to 400 times under real conditions. For example, even Telsa has a maximum power of 310 kW, but the actual discharge rate is only 4C. Moreover, lithium batteries are used as closed energy storage systems with low energy density, and high power discharge and high cruising range are basically difficult to be compatible unless the battery weight is greatly increased. Even though Tesla uses the current best-density ternary battery, its battery components weigh nearly half a ton.

Security comparison

In addition to the above indexes, no doubt is critical for motor vehicle safety. Lithium battery as a closed system of energy, in principle it is difficult to compatible with high energy density and safety, otherwise it is equal to the bomb. Therefore, in the mainstream process route, the lithium iron phosphate with low energy density is safer, and the decomposition begins when the battery temperature reaches 500-600 degrees, and basically does not require too much protection auxiliary equipment. Tesla using ternary battery energy density is high, but not high temperature resistant, 250-350 degrees will decompose, poor safety. The energy density of the ternary battery used by Telsa is high, but it is not resistant to high temperatures. It will decompose at 250-350 degrees and has poor safety. The solution is to connect more than 7000 batteries in parallel, which greatly reduces the risk of leakage from a single battery, and even the combination of a complex battery protection device. And previous accidents happened several times, although the benefit from the Tesla's security design and there are no casualties, but in terms of accident itself, actually is very slight collision, the body also didn't receive any damage, but the battery is on fire, and also reflects its security on the natural side of disadvantages.

Fuel cells due to the raw material of hydrogen flammable and explosive, the market generally worry about their safety. But as we have the following table data, steam and gas of the two common than gasoline vehicle combustible gas, the security of the hydrogen is not bad, and even slightly better. Vehicle hydrogen storage devices are now using carbon fiber material, in 80 km/h speed multi-angle collision tests can do unscathed. Even if the accident cause leakage due to high concentration hydrogen explosion requirements, before the explosion generally had begun to burn, but it is difficult to explode. Hydrogen and light weight, the overflow system of the hydrogen will rapidly rises after fire, instead of a certain extent, to protect the car body and passengers. Gasoline for liquid lithium battery for solid, it is difficult to rise in the atmosphere, burning in the bottom of the tank car, the vehicle will quickly scrapped on fire. Hydrogen storage and transportation links and LNG actually very similar, only the required pressure is bigger, with commercialization, its overall security is manageable.

Battery car cost is mainly divided into whole vehicle cost, raw material costs and costs. For fuel cell most reviled now is cost is too high, but with the development of the eye, as the technology progress and commercialization degree increase, it is a big space to cost down. And lithium battery if considering the cost of the expansion and the grid side, in fact, the comprehensive cost is higher than that of fuel cells, specific measure is as follows:

The vehicle cost comparison

Lithium battery, fuel cell and the traditional gasoline vehicles, vehicle cost differences mainly embodied in the engine costs, these other components.2 l gasoline engine car costs around 30000 Yuan, the future is difficult to have the too big change. Existing lithium-ion batteries kWh cost is 1200 Yuan/kWh, the future is expected to be down to 1000 Yuan/kWh, 45 degrees of electric vehicles, battery costs 45000 Yuan. Fuel cell costs primarily and high pressure hydrogen storage battery, now 100 KW battery pack cost is 100 Yuan, predicting annual output of 500000, the cost per unit will drop to $30 / KW, which is 20000 Yuan. Existing hydrogen storage cost is 60000 Yuan, the future is expected to drop to 35000 Yuan, the total cost is 55000 Yuan. Long term three power system cost difference is not big, visible vehicle cost is not the core problem.

Raw material cost comparison

The fuel consumption of a 2L petrol car is 10 liters per 100 kilometers, and the price of gasoline is 5.8 Yuan/L. The cost is 58 Yuan. Lithium battery car hundreds of kilometers of power consumption for 17 degrees, 0.65 Yuan/KWH cost, costs 11 Yuan. Fuel cell hundred kilometers consume hydrogen 9 square, hydrogen production methods mainly divided into the electrolysis of water or chemical reaction, such as coal and hydrogen production, hydrogen production from natural gas, etc. Electrolysis of water cost is mainly electricity, the average 5 KWH 1 hydrogen, cost about 3.8 Yuan/square, but can be directly electrolytic hydrogen station, save transportation cost. If large-scale centralized production of fossil energy is used, the lowest domestic cost is coal-to-hydrogen, which is about 1.4 Yuan/square, while North America can use cheap natural gas at a cost of 0.9 Yuan/square. If we take the cost of coal gas as the standard, the cost of raw materials per 100 kilometers is 12.6Yuan, which is not much different from lithium batteries.

Matching cost comparison

Filling stations, gas stations, charging station cost is mainly divided into land costs, equipment costs, construction costs, the difference mainly reflects in the equipment cost. Gas station basic in 3 million Yuan, charging station is 4.3 million Yuan, filling stations to Japan's current standard is expected to be 15 million Yuan, the overall cost of filling stations is higher than 10 million Yuan. According to the 15 years of depreciation, annual sales volume of 10 million square, the depreciation cost is 0.1 Yuan/square. When small hydrogen generally transported in tank trucks, freight is 0.44 Yuan/square, is expected to scale enlarged can use of pipeline transportation, the cost will be dropped to 0.23 Yuan/square.

Although lithium batteries on ready-made grid system at present, and form a complete set of cost is very low. But if a promotion, the capacity of the existing grid redundancy will be exhausted and basic must be large-scale expansion in the future. Matching cost externalization so charging station is essentially to the grid, so to calculate the cost of the whole industry chain will add the cost of power grid. General commercial operation of charging station for at least 1 hour to achieve quick charge standard, corresponding to the power of the charging station consisting of 10 charging pile will reach 600 kilowatts, the equivalent of hundreds of families of power load, the impact on the power grid load greatly. Corresponding grid needs new investment 1.2 million Yuan to increase the load, but an annual increase of quantity sold only 930000 degrees, according to the electricity purchasing cost 0.65 Yuan/degree, the grid side back 15 years investment in calculation, the price should be based on costs increased by 0.18 Yuan/degree.

Sales side cost estimates

The gas station's sales network is very mature, the level of profits can be used as a filling station an hour the measure benchmark for reasonable return. The corresponding filling stations each side spread is 0.51 Yuan, 4.9 Yuan per kilowatt-hour lithium-ion batteries. The electricity situation, basic can't promote lithium battery car. The current regulations of the state, charging station service charge limit to 0.4 Yuan/degree, but its background is given a large amount of subsidies. But there is no industry can rely on subsidies to develop for a long time, in the future if the lithium battery charging efficiency was not significant, this link at the filling station, enterprise profitability will be significantly lower than the gas station and filling station. There is no reasonable return, exiguous in the big cities. Investors don't have any incentive to promote charging stations, nor natural development of the industry. But lithium battery low energy density is too low, if forced to realize high charging efficiency, engineering challenge for the battery cycle life will be very large. And even can realize quick charge 3 minutes, but corresponding to a single charging pile to be as high as 1200 kilowatts of power to each charging station to form a complete set of a 110KV substation. The investment up to 50 million Yuan, covers an area of 5000 square meters, and around 300 meters cannot have a residential building, has a very big challenge for coastal cities in the operating level now.

Total cost

Integrated all of the above costs, petrol car, lithium battery, at the present stage, and fully commercialize fuel-cell cars after hundred kilometers cost for 58, 83, 23, and is 20 Yuan. Lithium batteries cost proportion because of the sales price is very high, we consider the charging pile is the 1/3 of filling station equipment investment, the hours profits fell to 1.4 Yuan, comprehensive cost there are 37 Yuan, fuel-cell cars cost advantage for a long time is still very obvious. In fact, this also is the root of all fuel cell energy density is highest, the same commercial cases, the cost of nature has the advantage.

An important logic for the development of new energy vehicles is energy conservation and environmental protection, which is undoubtedly more important to China. At present, China is not only seriously polluted by air, but also has a dependence on oil imports of up to 60%, 85% of which is subject to the US-controlled Straits of Malacca. Energy security has become the biggest weakness of our national security. Therefore, an important reason for the state to give huge subsidies to new energy vehicles is to ease the dependence on oil imports. So below we compare the two from the aspects of energy conservation, environmental protection and resource constraints, as follows:

Energy saving and environmental protection comparison

Hydrogen fuel cell materials in our country at present coal is the most economical means of hydrogen production, the lithium battery power of raw materials, in our country are mainly comes from the coal to produce electricity. Therefore, both of these energy sources are derived from coal. Carbon emissions are simply transferred to the upstream. Therefore, whether energy is saved or not depends on energy conversion efficiency. The lithium battery car consumes every hundred kilometers 17 degrees, corresponding to 6.8 kg of coal; Fuel cells per hundred 9 square kilometers consume hydrogen, storage and transportation link loss 20%, corresponding to the coal was 7.3 kg; Gasoline vehicles every 10L of hundreds of kilometers of fuel coal carbon equivalent to 10 kilograms. In fact, new energy vehicles energy-saving effect is not obvious, its core value lies in the primary energy consumption from oil into China's rich reserves of coal, relieves the problem of energy security. From the perspective of environmental protection, there is almost no exhaust emissions from fuel cells, and only a small amount of lithium batteries are emitted. The pollution of the whole industry is mainly concentrated in the upstream. However, compared with the treatment of dispersed gasoline vehicle exhaust emissions, the upstream centralized pollution control is undoubtedly much less difficult. In summary, the fuel cell industry chain has the lowest pollution and can be considered as the best green vehicle energy.

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