Countdown to mass production, is the era of solid-state batteries coming?

To a certain extent, 2022 can be regarded as the first year for the mass production of solid-state batteries.

First, 50 Dongfeng Fengshen E70s equipped with Ganfeng Lithium Battery's first-generation solid-state batteries were launched and delivered in Xinyu, Jiangxi. Then, Guoxuan High-tech announced that its 360Wh/Kg ternary semi-solid-state battery will be mass-produced this year. The solid-state battery released by NIO as early as the beginning of 2021 will also be mass-produced at the end of this year or early next year.

These news prove that the industrial development of solid-state batteries has taken an important step forward.

As the most active research direction in the current power battery field, solid-state batteries are regarded as the highland of the next generation of battery technology. So, what are the advantages of solid-state batteries? What are the main difficulties faced by the industrialization of solid-state batteries? How long will it take to go from semi-solid-state batteries to true all-solid-state batteries?

On June 9, Cheyun and the National New Energy Vehicle Technology Innovation Center jointly held the 24th Cheyun Conference and the 23rd Technical Salon of the National Innovation Center for New Energy Vehicles. Representatives from solid-state battery companies and industry experts gathered together to share and discuss the latest relevant research results, development trends and demonstration applications of solid-state batteries.

The main guests participating are:

Zou Guangcai | Deputy General Manager of National New Energy Vehicle Technology Innovation Center

Wang Jiantao | Deputy General Manager of Guolian Automotive Power Battery Research Institute Co., Ltd.

Wu Fan | Distinguished Researcher and Doctoral Supervisor at the Institute of Physics, Chinese Academy of Sciences

Lin Wanyun丨Head of Market Research Department, ProLogium Technology Co., Ltd.

Li Zheng丨General Manager of Qingtao (Kunshan) Energy Development Co., Ltd.

Lin Jiu丨Deputy General Manager of Zhejiang Fengli New Energy Technology Co., Ltd.

Zhu Xingbao丨Professor and doctoral supervisor at Harbin Institute of Technology

Why are solid-state batteries so popular?

The power battery is the most important component of new energy vehicles, accounting for about one-third of the total vehicle cost. It is known as the heart of new energy vehicles and directly determines the vehicle's endurance, safety and other performance.

Currently, liquid lithium-ion batteries are widely used in power batteries, but this traditional lithium battery is entering a development bottleneck period, its energy density is approaching its limit, and safety issues can never be completely resolved.

Since 1991, the energy density of liquid lithium batteries has increased by 3% per year, currently reaching 240-260Wh/kg, and the process limit is about 300Wh/kg. The driving range is an important indicator pursued by electric vehicles. To improve the driving range, the energy density of the battery must be continuously improved.

Secondly, the electrolyte in liquid lithium-ion batteries is the main cause of battery safety accidents. The frequency of typical safety incidents caused by batteries around the world is on the rise, and electric vehicle fire accidents are emerging in an endless stream. The safety of lithium batteries has become a focus of attention from all walks of life.

Therefore, the new energy industry needs new battery technology breakthroughs to meet the growing market demand. Against this background, solid-state battery technology stands out and becomes an important development route.

As the name implies, the biggest feature of solid-state batteries is that they are solid. Lithium-ion batteries are mainly composed of four parts: positive electrode, negative electrode, electrolyte and diaphragm. Traditional liquid lithium-ion batteries use liquid electrolytes, which are called electrolytes. The difference of solid-state batteries is that solid electrolytes are used instead of liquid electrolytes, and solid electrolytes can also play the role of diaphragms, so diaphragms are also omitted.

Zou Guangcai, deputy general manager of the National New Energy Vehicle Technology Innovation Center, said that solid-state lithium batteries use solid electrolyte materials with stable electrochemical properties and non-flammable properties to replace electrolytes and diaphragms, eliminating the risks of leakage and combustion, and have higher energy density and safety. It is the main direction generally recognized by the next generation of batteries.

"The reason why solid-state batteries are so popular is actually because traditional liquid lithium batteries have encountered difficult-to-solve technical pain points," said Li Zheng, general manager of Qingtao (Kunshan) Energy Development Co., Ltd., and the most core issue is safety.

The second is energy density. He believes that compared with liquid lithium batteries, solid-state lithium batteries are not just a product, but more of a new system. Based on such a system, the current ceiling of lithium battery energy density can be broken through.

Finally, there is the issue of cost. As raw material prices rise, the cost pressure on lithium batteries is increasing. Solid-state batteries can further optimize system integration, reduce the cost of safety protection, and reduce the cost of the entire lithium battery application at the system level.

It is precisely the many advantages in terms of energy density, safety and cost that have attracted the industry's attention and expectations for the development of solid-state battery technology.

What challenges does the industrialization of solid-state batteries face?

Compared with the currently mature liquid lithium-ion battery industry, solid-state batteries, as a new route, still face some technical and industrialization challenges in the process of achieving mass production and installation.

Wang Jiantao, deputy general manager of Guolian Automotive Power Battery Research Institute Co., Ltd., summarized some of the current problems in the field of solid-state batteries:

First, there is the problem of low-cost solid electrolyte materials. Low-cost electrolyte materials with excellent comprehensive properties that meet the needs of large-scale applications are still lacking.

Second, there is the problem of interface matching between the electrolyte and the positive and negative electrode materials. There is a problem of chemical and electrochemical incompatibility between the positive and negative electrode materials and the solid electrolyte interface.

Third, the engineering preparation process and special equipment for large-capacity batteries need to be further developed to meet the needs of large-scale industrial production.

Fourth, there is the problem of interface stability during the cycle. There is mechanical incompatibility between the positive and negative electrode materials and the solid electrolyte, and the solid-solid interface peels off during the cycle.

In short, solid-state batteries are significantly different from existing traditional lithium-ion batteries in terms of material selection, structural design, battery technology and key equipment, and a complete and mature industrial chain has not yet been formed.

Li Zheng believes that the difficulty in industrializing solid-state batteries lies in the lack of reference, as it is a completely new field.

He compared it to liquid batteries. Since commercial mass production in 1991, liquid batteries have been improving their processes and materials, but overall there is a clear path. Solid-state batteries are innovative in terms of material systems, so the biggest difficulty is that there is no reference.

Zou Guangcai pointed out that while solid-state batteries are constantly improving their process technology level and product yield, reducing their development and manufacturing costs, building a complete solid-state battery supply chain system, and improving various performance indicators of solid-state batteries are all problems the industry is currently facing and are also hot topics of concern.

What are the new developments in solid electrolyte materials?

Solid electrolytes are the core technology of solid-state batteries. There are many material routes such as polymers, oxides, sulfides and halides, which have become the focus of technical research and development of major companies and research and development institutions. At this issue of the Car Cloud Conference, experts also brought the latest progress in the research and development of solid-state battery electrolyte material technology.

According to Wu Fan, a distinguished researcher and doctoral supervisor at the Institute of Physics, Chinese Academy of Sciences, his team began to promote the research and development of sulfide all-solid-state batteries and key materials in January 2019 under the leadership of Academician Chen Liquan and Teacher Li Hong of the Institute of Physics, Chinese Academy of Sciences.

In recent years, they have proposed a new strain stabilization theory in the synthesis and preparation of sulfide solid electrolyte materials, the high ionic conductivity mechanism of sulfide solid electrolyte materials, high energy density positive and negative electrode active materials compatible with sulfides, and the stability of sulfides themselves, air stability, thermal stability, and electrochemical stability of sulfides to improve the mechanical stability of sulfide materials, and proposed customized development and design at the energy density level of sulfide all-solid-state batteries.

Wang Jiantao, deputy general manager of Guolian Automotive Power Battery Research Institute Co., Ltd., focused on their work on low-cost, mass-produced electrolyte materials.

In terms of the development of sulfide solid electrolyte materials, which originated in 2015, Guolian's sulfide electrolyte materials have undergone several iterations. By 2021, the ion conductivity has been increased to 6 mS/cm, and a ton-level preparation capacity has been established.