Solid-state battery vs. fuel cell—whose technology will dominate the next decade of new-energy vehicles?

　　A piece of news that “charges for 1 minute and has a range of 800 kilometers” has drawn our attention to solid-state batteries. It seems that solid-state batteries have suddenly become a magic weapon for leaps in electric vehicles. Although if you take a closer look, it is not difficult to find that the information disclosed by Fisker still has many questionable points, but at least it shows that solid-state batteries are becoming a new direction for battery development.

　　On the other hand, fuel cell vehicles, which have been said for many years, have become the focus of attention in recent years as Japanese and Korean car companies have successively put into production. What is the future direction for new energy vehicles—solid-state batteries and fuel cells? What difficulties will each face?

　　“Flexible, high-energy-density solid-state battery”—this patent from American electric-car manufacturer Fisk claims to increase the range of electric cars to 804 kilometers and reduce charging time to just 1 minute. The patent describes a solid-state battery.

　　We might as well use the physics knowledge of junior high school to make a simple calculation. According to the current excellent 10kWh / 100km energy consumption level of electric vehicles, 804km requires 80.4kWh of energy. If it is fully charged in one minute, the charging power will reach nearly 5000kW.

　　What is 5000 kW? Almost the power of a medium-sized power station. Therefore, this Fisker patent is only for laboratory data on a single solid-state battery. In reality, considering the integration of the battery pack and the endurance of the power grid, the so-called "recharge for 1 minute and a range of 800 kilometers" can only be a publicity stunt.

　　However, solid-state batteries are indeed an important direction for energy density breakthroughs in current automotive batteries. Fuel cell vehicles, another development direction, are also in full swing in recent years. I don’t see him. When Tesla and Toyota are taunting each other's technical route, it means that there must be a lot to tell here.

　　Solid-state batteries: a breakthrough that can enable large-scale commercialization of pure electric vehicles

　　Every significant improvement in battery performance is essentially a major change in the battery material system. Because each type of battery material system has its upper limit of energy density.

　　From the first-generation nickel-metal hydride batteries and lithium-manganese oxide batteries, through the second-generation lithium iron phosphate batteries, to the third-generation ternary batteries—widely used today and expected to remain dominant until around 2020—the energy density and cost have shown an obvious trend of alternating increases and decreases. Therefore, what kind of battery system the next-generation power battery chooses is very important to achieve the battery target around 2025.

　　The current lithium iron phosphate battery has an energy density of approximately 120-140 Wh/kg. The energy density of a large-scale ternary battery can reach 130-220 Wh/kg, and the ternary battery in the laboratory can reach 300 Wh/kg.

　　However, due to the influence of the existing system architecture and key positive electrode materials, the energy density of the lithium ion battery in the existing system is basically difficult to exceed 300Wh / kg, and it is difficult to meet the needs of future power batteries. In order to reach the energy density of 400 Wh/kg for single cells in 2025 and 500 Wh/kg in 2030, the development and industrialization of emerging battery technologies is imminent, which means that the mileage of electric vehicles will double compared with now.

　　 Currently, the main challenge facing commercial lithium-ion batteries is the use of liquid/gel-like electrolytes, which have limited electrochemical windows and are difficult to be compatible with lithium metal negative electrodes and newly developed high-potential positive electrode materials, thereby creating a bottleneck in further increasing energy density. At the safety level, such a structure will also cause problems such as short-circuit ignition, increase in ion concentration, battery internal resistance, and continuous consumption of electrode materials.

　　The solid-state battery is coming into the spotlight due to its high ionic conductivity and mechanical strength, wide electrochemical stability window, and broad operating temperature range, enabling it to achieve high energy density, high power density, and enhanced safety.

　　The solid electrolyte has a wider electrochemical window than the organic electrolyte, which is beneficial to further widen the voltage range of the battery, and because there is no concentration polarization, it can work in high current conditions, thereby improving the energy density of the battery. At the same time, the solid electrolyte is non-flammable, non-corrosive, non-volatile, does not have the problem of leakage, does not need a separator to separate the positive and negative electrodes, and prevents the growth of lithium dendrites, which fundamentally avoids the short-circuit phenomenon of the battery and can apply more negative electrode materials.

　　In addition, when integrated into electric vehicles, solid-state batteries also have the characteristics of compact structure, adjustable scale, and large design flexibility, which are conducive to vehicle integration.

　　In this way, is the solid-state battery perfect? This is far from the truth. Currently, potential solid electrolyte materials can be categorized into polymers, sulfides, and oxides. However, the chemical properties of these different materials—and their various arrangements—vary significantly. Some offer fast charging speeds, while others boast high energy density; each material has its own unique advantages. At the same time, each also has its own shortcomings, and it is challenging to address all issues with a single material.

　　At the same time, the fact that the chemical properties are not stable enough and the manufacturing process is not perfect also makes solid-state batteries still have a long way to go.

　　The realization of the industrialization of solid-state batteries fundamentally depends on breakthroughs in material technology. At present, patents on solid-state batteries far exceed those for the synthesis of other types of batteries. The industrial application of high-energy-density all-solid-state batteries is expected to take 5-10 years. Some advanced companies will produce solid-state batteries in small batches in 2020, while mass production in large areas is expected to be around 2025.

　　Fuel cells: How to achieve a profitable business model is the key to popularity.

　　Theoretically, hydrogen has a much higher energy density than electricity and oil. Of course, this refers to using hydrogen to generate electricity rather than directly burning hydrogen. Moreover, it only takes a few minutes for a single hydrogenation, and the driving range reaches 500-700km. During the use, only water is discharged without any other exhaust gas, which is completely zero emissions.

　　However, it seems that there are three key issues that need to be solved for fuel cell vehicles to be truly commercialized on a large scale: fuel cell life, fuel cell cost,

　　Currently, if they don't rely on government subsidies, fuel cell vehicles still remain in a "high-price" state. In addition to general R&D investment, the amount of the precious metal platinum in the catalyst is an important factor. Even with the current technological progress, the amount of platinum used still reaches 0.3-0.5g / kW. Therefore, a 100-kW fuel cell system requires about 30–50 grams of platinum. Referring to the market price of platinum jewelry, you can probably get a sense of just how costly this is.

　　On the other hand, domestic R&D and production of some key components—such as bipolar plates, air compressors, and DC boost components—in fuel cell systems largely depend on imports, which also contribute to the high costs of domestically produced fuel cell vehicles.

　　This is the cost of the car, and the cost of hydrogen fuel is also a big problem. There are two main methods of hydrogen production: electrolysis of water to produce hydrogen and industrial by-product hydrogen production. The cost of the former can be more than three times that of the latter. However, because fuel cells have extremely high requirements for hydrogen purity (99.9%), during the demonstration run of small batches, the country still mainly uses electrolytic hydrogen.

　　During the Shanghai World Expo, the cost of hydrogenation of fuel cell vehicles was 70 yuan/kg, and the fuel cost per unit of mileage at this price was even higher than that of traditional fuel vehicles.

　　If renewable sources of hydrogen, such as by-product hydrogen, can be utilized, the price of hydrogen per kilogram will be around 20 to 30 yuan. For cars, one kilogram of hydrogen can enable a range of more than one hundred kilometers. This translates to a fuel consumption of approximately 8 liters of oil, based on the current oil price of about 50 to 60 yuan.

　　At this time, the cost of using a fuel cell vehicle is only about half that of a conventional fuel vehicle. Of course, the separation, purification, and distribution mechanism of industrial by-product hydrogen require in-depth research and continuous improvement.

　　In addition, hydrogen storage is also a key factor in the popularity of fuel cell vehicles. To achieve higher energy density, hydrogen is often cooled to below -253°C and converted into a liquid for storage. This not only demands high thermal insulation performance from the hydrogen storage container but also means that liquefied hydrogen consumes a significant amount of energy—accounting for roughly one-third of the hydrogen’s total energy content—thus greatly reducing the overall efficiency of vehicle hydrogen energy utilization.

　　During the hydrogen filling process, additional cooling measures must be taken to control the temperature rise of the gas cylinder, which is generally as low as -40 °C. It is conceivable how much additional energy is needed to achieve temperature control during this filling process.

　　No matter which hydrogen production method, storage method, or transportation method, the hydrogen energy ecosystem needs to be re-established, involving a large amount of infrastructure investment and construction.

　　Currently, there are only 6 hydrogen refueling stations in operation in China. According to the national "13th Five-Year Plan," China will build 100 hydrogen refueling stations by 2020, but this is only the current level of Germany and Japan. Moreover, the construction cost of a hydrogen refueling station exceeds 10 million yuan, reaching nearly 10 times the charging station, and the complexity of the intermediate links makes the construction and cycle of the hydrogen refueling station much more difficult than the charging station.

　　Solid-state battery or fuel cell: Who can solve the battery material system and hydrogen ecosystem first?

　　Who can represent the future of new energy vehicles? At least for now, there is no clear answer. On the one hand, the battery material system urgently needs to be upgraded in exchange for higher energy density; on the other hand, the hydrogen energy ecosystem is urgently needed to be established so that fuel cell vehicles can get on the right track of the business model.

　　Obviously, the two problems that restrict their respective developments cannot be solved in a short time. This is why there are powerful members in both camps insisting on their technical line.

　　　From the perspective of infrastructure construction, the construction of charging infrastructure in China, especially in first- and second-tier cities, has begun to take shape, and most electric vehicle users are no longer worried about being unable to charge. In contrast, the construction of hydrogen refueling stations is still a huge challenge due to technical and cost constraints.

　　However, it is undeniable that the huge potential of fuel cell vehicles has not been exploited. The current problems in various industrial chains cannot obliterate the superiority of the hydrogen energy ecosystem. This is why the industry generally considers fuel cell vehicles as "communism."

　　But from the current point of view, whether it is technical maturity, consumer acceptance, promotion feasibility, or policy guidance, pure electric vehicles with higher driving mileage will become the common choice of car companies in the next 5-10 years.

— From Net Tong Jiren Automobile Review