What is the current status of power lithium battery development?

At present, domestic new energy vehicles are still using lithium iron phosphate (BYD-based) and ternary lithium batteries. The cruising range of the models can basically reach 300 kilometers, but the average energy density of the battery system is only 115Wh/Kg. In March 2017, the four ministries and commissions of the Ministry of Industry and Information Technology jointly issued the Action Plan for Promoting the Development of Automotive power batteries. It was pointed out that by 2020, the specific energy of the new lithium-ion power pool should be more than 300Wh/Kg; the system should strive for 260Wh. /Kg.

The data shows that the gap between the current energy density of the power battery and the target value in China is 126%. It is too difficult for the lithium iron phosphate battery to reach the target value in 2020, but it is entirely possible for the ternary lithium battery represented by Tesla. The power battery performance is good, and the BMS management system is also efficient; in addition, the solid-state lithium battery can also increase the energy density of the battery system to 260Wh/Kg.

1. Ternary lithium and lithium iron phosphate battery - the current mainstay

At present, the global new energy vehicle market has entered a critical period of vigorous development. Mainstream auto companies have laid out new energy vehicles. The rapid maturity of the lithium battery industry chain will further promote the large-scale application of new energy vehicles. From a global perspective, the typical car-owned models mainly use Japanese and Korean power batteries, mainly ternary lithium, and the cruising range basically reaches or exceeds 350 km.

Table 1 Global mainstream power battery support

Looking at the domestic market, from the first six batches of new energy vehicles in 2017, the energy density of the new models equipped with batteries has also increased to varying degrees. In the first batch of catalogs, the energy density of more than 115Wh/Kg accounted for only 13.11%, and the proportion of the fifth batch of catalogs reached 73%. It can be seen that the increase in the energy density of power batteries is the trend of the times. The power battery of the mainstream electric vehicle enterprises has also gradually transformed into three-element lithium, and the cruising range can basically reach the level of 300 kilometers.

Table 2 Domestic mainstream power battery supporting situation

Looking at the situation of domestic and international power battery companies carrying new energy vehicles, the trend of ternary lithium batteries becoming the mainstream technology route has been irreversible, but there is still room for improvement in the mileage of the entire vehicle. This is probably due to many reasons such as the low energy density of the power battery and the room for improvement in BMS efficiency.

2. Full solid lithium battery - the future direction of development

The research and development goals of high energy density lithium batteries developed by countries all over the world are actively deploying forward-looking technologies such as lithium-sulfur batteries, lithium-air batteries or lithium metal batteries.

On the basis of inheriting the advantages of traditional lithium batteries, solid-state lithium batteries have made great progress in safety and energy density. At present, the energy density of all solid-state lithium battery research and development can reach 300~400Wh/kg, which is expected to become an important development direction of the next generation of high energy density power and energy storage battery technology. This is the consensus of academia and industry.

Figure 1 Stage goals of power battery energy density in countries around the world

Figure 2 World lithium battery technology route

Global power battery affiliates have also accelerated the deployment of all-solid-state lithium batteries to seize opportunities. At present, the industrialization process of various technology paths is different. Among them, polymer solid-state batteries are developing rapidly, and the laboratory has been completed due to its high-temperature work performance. It has been verified that a small number of enterprises have achieved small-scale industrialization.

Development status of solid-state lithium battery (polymer solid battery)

Bollore, France: All-solid-state secondary battery (LMP), lithium metal for negative electrode material, polymer (PEO, etc.) for the electrolyte. It has been applied in France for EV, shared service car "Autolib" and small electric bus "Bluelus". The total application is more than 3,000 vehicles.

US Seeo: All solid secondary batteries use Daiso's dry polymer film to provide a sample battery pack with an energy density of 130-150Wh/kg. In 2017, the energy density can reach 300Wh/kg, which has not been promoted.

CATL: At present, a polymer battery with a capacity of 325 mAh has been designed and manufactured, which exhibits good high-temperature cycle performance and has not been popularized.

Qingdao Institute of Energy, Chinese Academy of Sciences: The large-capacity solid-state polymer lithium battery “Qingneng I” has completed the deep-sea scientific research, its energy density exceeds 250Wh/kg, and the 500-cycle capacity remains above 80%, in multiple times of acupuncture and extrusion, maintains very good safety performance under harsh test conditions. “Qingeng II” has also been successfully developed with an energy density of up to 300Wh/kg, which has not been promoted.

In addition, in solid-state lithium batteries, sulfide solid-state batteries (lithium-sulfur batteries) have great potential for development due to their high energy density and low cost. Toyota, Samsung, CATL, Toyota and other domestic and foreign companies have accelerated their layout. Among them, Toyota Technology is the most advanced. Toyota introduced a sulphide solid-state battery in 2010. In 2014, its experimental prototype energy density reached 400Wh/kg. By the beginning of 2017, Toyota's solid-state battery patents reached 30, far higher than other companies. According to Toyota executives, Toyota will realize the industrialization of sulfide solid-state batteries by 2020. Domestic enterprise CATL is relatively leading in sulfide solid-state batteries and is accelerating the development of sulfide solid-state lithium metal batteries for pure electric vehicles.

Development status of solid lithium battery (sulfide solid-state battery)

Toyota: Solid-state batteries were introduced in 2010. In 2014, the experimental prototype energy density reached 400Wh/kg.

Samsung Japan Research Institute: A 2000mAh, 175Wh/kg laminated all-solid secondary battery was produced using a sulfide-based solid electrolyte.

Sakti3 (USA): In 2015, it received a $15 million investment from British appliance giant Dyson. The solid-state battery developed by the company uses ceramics as the electrolyte, lithium metal or lithium alloy as the negative electrode and the energy density reaches 1000Wh/L. stage.

Qingdao Energy: The company core lies in the development and production of high-solid content all-ceramic separators and inorganic solid electrolytes. At present, the team has cooperated with BAIC to conduct a pilot test, which may be an important component of Beiqi electric vehicles in the future.

CATL: The main research and development direction is sulfide electrolyte. The positive electrode coating method is used to solve the interface reaction problem. The hot pressing method reduces the interface resistance.

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