Deep analysis of the selection and technical research of positive/negative materials for power batteries

"Higher, faster, stronger" is a well-known Olympic sports spirit. This Olympic campaign's motto is proposed by the founder of the modern Olympic movement, Coubertin, expounding the spirit of the Olympic Movement's progressive and never satisfied struggle.

Switching to the electric vehicle industry, as the heart of the power battery, in the battery material selection and technical research, research and development of new technologies, to provide higher energy density, to achieve longer range, is a challenge facing the industry Research hotspots.

According to Fang Kaizheng, an expert in the Power Battery Research Office of the Beijing Research Department of the China Automotive Research Center, the growth of new energy vehicle production has led to the growth of power battery supporting batteries. In the first three quarters, the total power battery supporting capacity exceeded 121 billion watt-hours, of which pure supporting the amount of electric vehicle type is 110 gigawatts (GW), plug-in hybrid models supporting the amount of 11 billion watts Yes. Taking advantage of the development of the power battery industry, industrial researchers are constantly researching and improving the energy density of power batteries to realize the technology research and development path of “higher energy density, stronger power and longer battery life”.

Diversified technical routes

Tan Xinxin, deputy dean of Hunan Shanshan Energy Technology Co., Ltd., said that as an important raw material supplier in the battery field, Shanshan will consider continuously increasing the discharge specific capacity of the battery material, as well as the charge and discharge voltage, and considering its power. Density and calendar life, including cycles, side reactions, and more.

Shanshan Energy is a subsidiary of Shanshan. It was established in 2003 and has two subsidiaries, Hunan Shanshan New Energy and Ningxia Shanshan New Energy. Under the challenge of electric vehicle mileage of 400-500 kilometers and battery life of 10 years or even longer, Hunan Shanshan Research Institute will continue to carry out technical research and development on high-performance power ternary materials to meet the needs. Demand for downstream power battery plants.

In terms of material selection, high-nickel ternary materials have become the hottest choice in the industry. Because it has a greater advantage in specific energy than lithium iron phosphate and low-nickel ternary materials. The company's related technology research and development investment has also followed suit.

If you want to increase the energy density of the battery, when selecting materials, the director of Hunan Shanshan Research Institute Tan Xinxin pointed out: "A high-performance power ternary material is not simply highlighting one of the series or two series. If there is a series that can't be done, I don't think it is a good cathode material."

He also mentioned the four possible technology development routes. The first one is the most well-known and most popular nickel-enhancement route; the second is the medium-nickel high-voltage development route; the third is the high-nickel high-voltage development route; and the fourth is the high-voltage LCO development route. From the perspective of energy density, as the nickel content increases, the overall energy density of the battery will become higher and higher, and the increase in power will also bring about an increase. At the same time, the high-voltage lithium cobaltate has a voltage platform and a high capacity, and the overall energy density. It will be higher.

However, when everyone is talking about high nickel capacity of 300Wh/kg or even 400Wh/kg, Tan Xinxin also mentioned that, in the current situation, high-nickel materials, especially 80% nickel content, are in the domestic market this year. The proportion of high energy density cathode materials in the domestic promotion and use may take a certain time, and the entire industry needs to avoid excessive speculation and partial overheating.

High nickel content of cathode material

On November 22nd, the Equipment Industry Department of the Ministry of Industry and Information Technology announced the "Regulations for Automotive Power Battery Industry (2017)" (Draft for Comment), and the "Regulations for Automotive Power Battery Industry" (hereinafter referred to as "Standard Conditions" ") to amend. This is the basis for the power vehicle battery manufacturers to be better and stronger, establish product specifications and quality assurance systems, strengthen technology and management innovation, improve product development and manufacturing levels, and improve product performance and quality.

According to Wu Hui, general manager of CCID Consulting's investment department, in the first ten months of 2016, the total shipments of the top ten domestic power battery shipments reached about 11390.5MWh. With the rapid development of the pure electric drive automobile industry and the increasingly hot power battery industry, the energy density of power batteries is developing toward higher and higher, which puts higher requirements on the materials of positive and negative batteries.

As far as the development trend of power batteries is concerned, there are basically three types of cathode materials, and the anode materials are mainly carbon materials. Silicon carbon materials and hot materials are also being studied. Among them, oxides are lithium titanate as the main material.

“The positive electrode material will gradually transition to ternary materials,” said Chen Yanbin, general manager of Shengsheng Technology. In the research and development of high energy density ternary materials, Dangsheng Technology has always been at the forefront of the industry. Increasing the energy density of the battery by increasing the nickel content is a feasible technical route. But what specific technical route to take, such as high nickel or high voltage, may vary from company to company.

Chen Yanbin explained: "From the perspective of the overall international trend, the route taken is to first increase power consumption and then to make high voltage."

Nowadays, high-energy-density cathode materials are increasingly becoming the mainstream of the battery industry. It is reported that domestic cathode products manufacturers with leading product technology have begun to research and produce high-nickel ternary materials, some types of high-nickel ternary materials. For example, Type 622 and Type 811 have also started small-scale production, and some enterprises have already tested and applied in downstream enterprises. Moreover, the capacity ratios of Types 622 and 811 can reach 160 mAh/g and 180 mAh/g, respectively, which is a certain degree of improvement over the current Types 532 and 111.

Chen Yanbin also mentioned that high nickel is the preferred direction for high voltage. The ultimate goal of high-nickel materials is the 811 model, and the 811 material is also more promising. When the high energy density of the technology is high nickel, it also does some high voltage of medium and high nickel, and it also improves the life and safety of the battery from the aspects of precursor, sintering, doping and surface treatment.

To do high-nickel materials, it is necessary to solve the problems of life, storage safety, etc., and it is necessary to optimize from the front body, deliquescence, doping, and surface. Regarding whether there is a problem with the life of high nickel, Chen Yanbin also said that the technology of Rising Technology can ensure that the life will not be affected on the basis of 20 mA.

Negative electrode materials increase research and development

By 2025, how can a power battery achieve high energy density and fast charge? In the field of fast charge anode materials, Betray has been developing a composite high energy density anode material. Through the close cooperation between the battery factory and the OEM, the battery energy ratio is 300Wh/kg and the vehicle cruising range is 500 kilometers. Yan Huiqing, technical director of Beitray, answered this question.

Yan Huiqing also said that Betray has developed technology in four kinds of negative electrode materials, namely fast charge graphite anode material, fast charge soft carbon/hard carbon material, fast charge silicon series material, and fast charge lithium carbonate anode material.

At present, the batteries developed by domestic battery companies are basically based on lithium iron phosphate batteries , which are commonly used in passenger cars, special vehicles, and buses. Yan Hui Qing said: "Improving the energy density of lithium iron phosphate cathode first to do, we have been in the continued development of anode materials, doing high energy density lithium iron phosphate batteries, the powder itself from the Processing of view, positive, negative Or the ternary material has the same technology in terms of the compaction density increase and capacity improvement of the battery as a whole, so we are also developing a high-energy density lithium iron phosphate battery, and strive to put the battery capacity up and put the compaction density up. In particular, the compaction density, therefore, we made a spherical lithium iron phosphate. At the same time, we applied high-end anode materials to improve the energy density of the entire lithium iron phosphate battery."

In contrast, Lv Xuelong, a senior researcher at the Materials Research Department of the Taiwan Industrial Technology Research Institute, said: "In fact, last year, battery manufacturers began to mention the use of ternary materials for mixing, and the second is to use lithium iron phosphate directly. A positive electrode material solution that increases energy density. Other academic research units, such as Harbin Institute of Technology, also have a technology that includes lithium vanadium phosphate. The difference is that it seems that for cathode material manufacturers, the solution for lithium vanadium phosphate is not available at this stage. effective method."

Nowadays, the requirements for the mileage of electric vehicles are getting higher and higher. For power batteries, if the energy density of the electric vehicle is required to be doubled, its technical difficulties exist in many aspects.

Su Jinran, deputy chief engineer of Tianjin Lishen Battery Co., Ltd. (referred to as “Lishen”), analyzed that it is still necessary to achieve 350 watt-hours/kg under the lithium-ion system. Nowadays, some aspects of NCA, nickel material, silicon carbon anode material need to be discussed, but the silicon carbon anode material needs to overcome some technical problems, such as its cycle characteristics and expansion characteristics.

It is estimated that by 2020, the domestic lithium-ion power battery energy density will reach 350 watt-hours / kg. In this regard, Su Jinran believes that this will have very high technical requirements. If you simply use the current lithium-ion battery system, it may be difficult to achieve this energy density value.

Therefore, some new power battery cathode materials, anode materials and even membrane materials should be studied in depth. If there is no breakthrough in these aspects, the technical level will be limited or will be limited. Lishen also has a dedicated team to do this work.

From the perspective of the battery material system, Director Xiao Chengwei of the 18th China Electronics Technology Group Corporation said that the battery anode material is basically carbon-based, and the cathode material will also have large changes, including lithium manganate, lithium cobalt oxide and other materials. .

From the perspective of the entire development industry trend, it is hoped that through the selection of different material systems, the hybrid energy battery with higher industrial energy density will be developed to realize the large-scale application in the field of new energy vehicles.

However, Xiao Chengwei analyzed that from the current state-of-the-art technology development roadmap and the next subsidy policy, the state is still guiding the direction of high-energy batteries. While each battery company is trying to increase the energy density of lithium iron phosphate batteries as much as possible, the next step will be to increase efforts to develop and promote some products of ternary batteries.

Power battery research and development technology is an important factor affecting the promotion and application of electric vehicles. As one of the important indicators of power battery performance, improving energy density is only one of the methods. The entire power battery industry needs to reduce the cost and improve the overall performance of the power battery by improving power density, service life, and research and development of new material technologies.

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