Application of Solid State Batteries in Low Altitude Economy

Foreword
      At present, the mainstream low altitude aircraft in the market usually use lithium-ion batteries with an energy density of 280~320Wh/kg. The positive electrode of such batteries is usually made of lithium cobalt oxide or ternary materials, and the negative electrode is usually made of artificial graphite or silicon carbon negative electrode materials. This type of battery has a high energy density and can meet the short-term use requirements of low altitude aircraft in terms of high rate discharge performance. However, in the long run, the energy density of this type of battery still cannot cover all application scenarios of low altitude aircraft, such as electric vertical takeoff and landing (eVTOL) or other large electric aircraft that need to fly over long distances (>250km) across urban areas. Therefore, eVTOL requires batteries with high safety, high energy density, and high power density. Solid/semi-solid state batteries may be the mainstream route for the future.

Analysis of Solid State Battery Technology

According to the content of liquid electrolyte, batteries can be divided into four categories: liquid (electrolyte mass ratio of 10% to 25%, expressed in wt%, i.e. 10wt% to 25wt%), semi-solid (5wt% to 10wt%), quasi solid (0-5wt%), and all solid (0wt%). Among them, semi-solid, quasi solid, and all solid states are collectively referred to as solid-state batteries. All solid state batteries are composed entirely of solid materials, and have significantly improved safety, energy density, service life, temperature adaptability, mechanical strength, and other aspects compared to liquid and semi-solid state batteries.

2.1 Higher Security

All solid state batteries do not have flammable liquid electrolytes, fundamentally eliminating the risk of fire and explosion caused by electrolyte leakage, expansion, or overheating. The thermal stability of sulfide solid electrolytes can reach 300 ℃, which is more than 200 ℃ higher than that of liquid electrolytes.

2.2 Higher energy density and service life

The upper limit of the energy density of liquid battery cells is 300Wh/kg, and the non decay life is 3 years; The energy density of an all solid state battery can easily reach 400Wh/kg, with a theoretical energy density of up to 700Wh/kg, and a lifespan of up to 10 years without decay. In an ideal state, the number of cycles can reach 45000.

2.3 Lighter and smaller batteries

In liquid batteries, the separator and electrolyte account for 40% of the volume and 25% of the weight of the battery. When replaced by solid electrolytes, the thickness of the battery can be significantly reduced; In addition, the temperature control components inside the battery are eliminated, and the volume is further reduced.

2.4 Wider temperature adaptability

Compared to the working temperature range of liquid batteries from -10 ℃ to 45 ℃, all solid state batteries are resistant to both low and high temperatures, and their working range can be extended to -30 ℃ to 100 ℃. After being equipped with all solid state batteries, the problems of reduced range and decreased performance of new energy vehicles in winter will be effectively solved.

2.5 Wide material selectivity

The halide of all solid state batteries has good oxidation resistance and can adapt to high voltage, while sulfides can adapt to low voltage. By combining the two, a battery with a wide electrochemical window can be made, and the voltage range can be further expanded.

2.6 Higher mechanical strength

The biggest difference between all solid state batteries and traditional liquid state batteries is that all electrolytes are upgraded to solid electrolytes, which have higher mechanical strength.

Major measures for low altitude economy

In December 2023, the low altitude economy was established as a strategic emerging industry in China at the Central Economic Work Conference, and pilot projects were launched in various regions to promote the expansion of application scenarios such as drones and eVTOL, outlining the development blueprint of the low altitude economy. In 2024, the central and local governments will issue a series of major measures for the low altitude economy, leading the rapid development of the low altitude economy.

On January 1st, the Provisional Regulations on the Flight Management of Unmanned Aerial Vehicles were officially implemented.

On March 5th, the concept of "low altitude economy" was first included in the government work report of the State Council.

On May 21st, the Action Plan for Promoting High Quality Development of Low altitude Economy in Guangdong Province (2024-2026) was released.

On July 1st, the Leading Group for Promoting Low altitude Economic Development of the Civil Aviation Administration of China was established.

On July 21st, the development of general aviation and low altitude economy was first included in the Decision of the Third Plenary Session of the 20th Central Committee of the Communist Party of China.

On August 3rd, the China Low altitude Economic Alliance was launched and established in Beijing.

On November 5th, the Leading Group for Low altitude Industry Development of the Ministry of Industry and Information Technology was established.

On November 27th, the "Action Plan for Effectively Reducing Logistics Costs in the Whole Society" was released, encouraging the development of new logistics models that combine low altitude economy and other factors.

On December 10th, the China Meteorological Administration released the "Low altitude Economic Meteorological Technology Innovation Work Plan (2024-2030)".

On December 12th, the Central Economic Work Conference emphasized the need to accelerate the development of new quality productive forces and cultivate future industries such as low altitude economy.

On December 23rd, the "Opinions on Accelerating the Construction of a Unified and Open Transportation Market" were released, which clearly stated the continuous promotion of air traffic control reform and the development of low altitude economy.

On December 25th, the Low altitude Economic Development Department of the National Development and Reform Commission was officially established.

The relevant person in charge of the China Low altitude Economy Alliance stated that in 2024, the country attaches great importance to the low altitude economy, local governments take active actions, and all sectors of society actively participate, laying a solid foundation for the comprehensive and in-depth promotion of China's low altitude economy. In 2025, the national top-level design of low altitude economy, low altitude economy roadmap, and related air traffic standards and rules, policies and regulations will be successively introduced. Local governments at all levels will accelerate the construction of air traffic networks and ground flight service support facilities. By 2030, major cities in China will fully enter the era of low altitude economy.

The application prospects and challenges of solid-state batteries in low altitude economy

Low altitude economy is centered around low altitude (below 1000 meters) flight activities, using flying cars eVTOL、 The new quality productivity composed of technologies such as low altitude intelligent networking, through interaction with factors such as airspace and market, drives the development of related infrastructure, aircraft manufacturing, operation services, and flight support in a comprehensive economic form.

4.1 Application prospects
As the core of the future low altitude economy, eVTOL's energy system is mainly composed of batteries. The energy density, safety, and fast charging performance of batteries are key indicators of eVTOL energy system. Therefore, how to efficiently store electricity has become a major challenge restricting the development of low altitude economy.

To ensure the performance and market acceptance of eVTOL aircraft, eVTOL has high requirements for battery energy density, battery rate performance, and safety. Currently, the vast majority of eVTOL aircraft tend to use lithium batteries with mature technology and high power density as power sources. This choice is due to the fact that lithium batteries can provide a relatively balanced solution considering various factors such as existing technology, safety standards, flight distance, airworthiness certification progress, and cost control.

The "Outline for the Development of Green Aviation Manufacturing Industry (2023-2035)" issued by the Ministry of Industry and Information Technology and four other departments proposes to achieve mass production of 400Wh/kg lithium battery products and small-scale verification of 500Wh/kg products by 2025 as the research direction. From this objective requirement alone, it can be seen that low altitude aircraft have rigid requirements for their endurance capability. Due to the fact that eVTOL requires 10 to 15 times more power for vertical takeoff than ground travel, this places higher demands on the energy density of the battery. In general, eVTOL consumes about 65kWh of electricity per 100 kilometers, while electric vehicles only need 12-18kWh, and the driving capacity under the same battery pack is only 1/4 of that of a car. Therefore, eVTOL naturally has higher requirements for battery energy density.

In terms of energy density, the power required for eVTOL vertical takeoff is 10-15 times that of ground travel, with a commercial threshold of up to 400Wh/kg, while the energy density of solid-state batteries can reach 500Wh/kg, with a target of 1000Wh/kg by 2040; In terms of charging and discharging rates, the flight of eVTOL requires stages such as takeoff, cruise, and landing. During the takeoff and landing stage, the instantaneous charging and discharging rate of the battery is required to be above 5C, while the charging speed of solid-state batteries is about 5-6 times faster than traditional lithium-ion batteries, ≥ 1000 times; In terms of safety, low altitude economy requires high safety, and the use of solid electrolytes effectively reduces the risk of battery self ignition. Therefore, the requirements of eVTOL for battery energy density, power, safety, and other aspects provide development space for solid-state batteries.

4.2 Enterprise Layout

In November 2024, the successful global first eVTOL solid-state battery flight test of Yihang Intelligent EH216-S marked a significant breakthrough in the application of solid-state batteries in the low altitude economy field. On the stage of the 2025 CCTV Spring Festival Gala, Yihang Intelligent EH216-S unmanned manned aerial vehicle made a stunning appearance, with seven aircraft flying together, fully demonstrating the unique advantages and value of Yihang Intelligent in unmanned driving, cluster scheduling, safe flight, and efficient control, which have been widely recognized.

Funeng Technology stated that the company's eVTOL semi-solid state battery has entered the industrialization stage. The product uses a high nickel ternary positive electrode combined with a silicon doped negative electrode, with an energy density of 330Wh/kg and a cycle life of over 4000 cycles. The design verification and PV product verification testing have been completed, and samples have been sent to top customers in the low altitude economy field. In addition, Guangzhou Industrial Control Group plans to promote the integration of Funeng Technology into the low altitude economic development layout of Guangzhou, strengthen cooperation with Guangzhou Xiaopeng Automotive Technology Co., Ltd., Yihang Intelligence and other enterprises, and seize the opportunity for industrial development. At present, Funeng Technology has connected with the above-mentioned enterprises to meet their relevant needs.

The high specific energy battery products developed by Lishen Battery have been successfully applied in the field of flying cars, opening a new chapter in the field of low altitude transportation. It is reported that the product has mature technology, excellent comprehensive performance, high energy density, high power performance, and high safety. The energy density reaches 325Wh/kg, and it has the ability to sustain 3C discharge and 6C pulse. The working environment temperature is -30~55 ° C, and it has passed safety tests such as GB38031-2020 and 150 ° C hot box, supporting the usage needs of tonnage eVTOL under various working conditions. At present, Lishen Power Battery has completed the development of high specific energy semi-solid iteration products, which can provide customers with better battery cell lightweight design solutions and cruising capabilities.

CATL has signed a strategic investment and cooperation agreement with Shanghai Fengfei Aviation Technology Co., Ltd. to jointly focus on the development of eVTOL aviation batteries.

Shanghai Xiba Technology, the Joint Innovation Laboratory of Advanced Materials for Solid State Batteries of the Chinese Academy of Sciences Shanghai Silicate Research Institute and Shanghai Keyuan Solid Energy have completed the joint design of flexible lithium batteries for high specific energy solid state batteries. At present, they have entered the stage of small batch production. It is reported that this product will theoretically be the first to be applied in eVTOL scenarios.

The new high-capacity all solid state battery developed by Enli Power performs excellently in a stress free environment, achieving hundreds of stable charge and discharge cycles with a capacity retention rate of over 85%. Its lithium metal solid state battery has been successfully tested with HAPS.

The 46 large cylindrical batteries launched by Guoxuan High tech perfectly match the power requirements of unmanned eVTOLs and have met the conditions for industrialization, and have reached a strategic cooperation with Yihang Intelligent.

4.3 Challenge

Although solid-state batteries have broad application prospects in the low altitude economy, they still face many challenges. Firstly, the current production cost of solid-state batteries is relatively high, making it difficult to meet the large-scale commercial demand. Secondly, the mass production process of solid-state batteries is not yet mature and needs further optimization. In addition, the performance stability of solid-state batteries in extreme temperature environments still needs to be improved. To overcome these challenges, it is necessary for the government, enterprises, and research institutions to work together, increase research and development investment, improve industrial chain support, and formulate relevant standards and regulations.

summarize

Solid state batteries, as an emerging energy technology, have shown great potential for application in the field of low altitude economy. Its high energy density, excellent safety performance, and fast charging capability provide an ideal energy solution for low altitude economic equipment such as drones and electric vertical takeoff and landing vehicles. Although the commercialization of solid-state batteries still faces challenges such as high costs and complex production processes, with the continuous advancement of technology and the improvement of the industrial chain, solid-state batteries are expected to become the core energy system of low altitude economy in the future, promoting the development of low altitude economy towards higher efficiency, safety, and environmental protection. The government, enterprises, and research institutions should strengthen cooperation, increase investment, and jointly promote the research and application of solid-state battery technology, injecting new momentum into the development of the low altitude economy.