What are the differences between lithium batteries and hydrogen fuel-powered batteries?

As a kind of battery, the lithium battery is a closed system. The battery is only a carrier of energy and must be charged in advance to operate. Its energy density depends on the energy density of the electrode material. Since the energy density of the current negative electrode material is much greater than that of the positive electrode, increasing the energy density requires continuous upgrading of the positive electrode material, such as from lead-acid, to nickel-based, and then to lithium batteries. However, lithium is already the metal element with the smallest atomic weight. The cathode material that is better than lithium ion is theoretically pure lithium electrode, but the energy density is actually only 1/4 of gasoline, and the technical difficulty of commercialization is extremely difficult. There is no hope of breakthrough. Therefore, the increase in the energy density of lithium batteries is subject to theoretical bottlenecks, and the space is very limited. The maximum is to increase from the current 160Wh/KG to 300Wh/KG, even if it reaches only 1/120 of the fuel-powered battery, it can be described as losing on the starting line. Compared with the volumetric energy density, the important disadvantage of the raw material hydrogen of fuel-powered batteries is that the volumetric energy density is not high. Nowadays, pressurization is basically used to solve this problem. According to the current pressurization mode of 700 atmospheres, its volumetric energy density is 1/3 of gasoline. For the same running for 300 kilometers, the fuel-power battery hydrogen storage tank has a volume of 100L and a weight of 30KG. The corresponding gasoline vehicle fuel tank is 30L, but the volume of the electric motor is 80L smaller than that of the internal combustion engine, and the total volume is not much different. Lithium battery vehicles are divided into two mainstream technology routes: ternary and lithium iron phosphate. The representative companies are Tesla and BYD. The ternary energy density is higher, but the safety is poor. It requires auxiliary safety protection equipment. The two types of batteries required to run 300 kilometers are 140L and 220L, and weigh 0.4 tons and 0.6 tons, which are much higher than fuel-powered batteries. Looking forward to the future, if hydrogen storage alloys and low-temperature liquid hydrogen storage technologies can break through, the volumetric energy density of fuel-powered batteries will increase by 1.5 times and 2 times, respectively, and the advantages will be more obvious. Power density comparison Fuel power battery can essentially be understood as a chemical power generation system using hydrogen as raw material, so the output power is relatively stable. In order to maximize the discharge power, a power lithium-ion battery system must be added. For example, Toyota Mirai is matched with nickel-hydrogen battery. But as an open power system, its energy comes from external input. The additional nickel-metal hydride battery does not need to consider the problem of energy storage, as long as 5-8 degrees can meet the demand, the requirements for battery life are not high, and in real working conditions There are few restrictions on use under. Although the theoretical discharge efficiency of lithium batteries is very high, in order not to harm the battery life, there are many restrictions on use. It cannot be discharged at a large rate when fully charged, and fast discharge is only applicable to the range of 0-80%. Even so, discharging at a rate of 5C will shorten the cycle life of the battery in the laboratory to only 600 times, and will further reduce to 400 times under real working conditions. For example, even if the maximum power of Telsa can reach 310KW, the actual discharge rate is only 4C. . Moreover, as a closed energy storage system with low energy density, lithium batteries are basically difficult to be compatible with high-power discharge and high cruising range, unless the weight of the battery is greatly increased. Even if Tesla uses the ternary battery with the best energy density at present, the weight of its battery package is close to half a ton. Safety comparison In addition to the above indicators, safety is undoubtedly also very important for motor vehicles. As a closed energy system, the lithium battery is difficult to be compatible with high energy density and safety in principle, otherwise it is equivalent to a bomb. Therefore, in the current mainstream process route, lithium iron phosphate with low energy density is safer, and the battery starts to decompose when the temperature reaches 500-600 degrees, so there is basically no need to protect the auxiliary equipment too much. Although the ternary battery used by Telsa has a high energy density, it is not resistant to high temperatures and will decompose at 250-350 degrees Celsius, resulting in poor safety. The solution is to connect more than 7000 batteries in parallel, which greatly reduces the risk of leakage and explosion caused by a single battery. Even so, a set of complex battery protection equipment must be combined. In addition, in the early accidents, although there were no casualties due to Telsa's safety design, the accidents themselves were actually very minor collisions, and the body did not receive any damage, but the battery caught fire. , Also reflects its natural disadvantages in safety. Disclaimer: Some pictures and content of articles published on this site are from the Internet. If there is any infringement, please contact to delete. Previous: What are the important advantages of lithium batteries?