Shulou(Shulou.com)11/24 Report--

Is it still a qualified investor if you don't pay attention to new energy?

In the past few months, the concept of new energy vehicles has repeatedly swept the capital market. Not only consumers are concerned, but capital is also eager to try. Even Tesla and a number of new car-building forces have become the focus of the market, attracting giants of various industries to enter across the border one after another.

Do you think the throttle of new energy is stepped on to the bottom? No, it's not full yet.

With the proposal of "carbon peak and carbon neutralization", new energy vehicle is not only a new concept of transportation, but also a part of the national top-level design.

According to the New Energy vehicle Industry Development Plan (2021-2035) released by the General Office of the State Council on November 2, 2020, domestic sales of new energy vehicles are expected to reach about 20% of total new car sales by 2025. The current figure is about 4% to 5%-which means that the market has at least three times the room for growth [1] [2].

In fact, the so-called new energy vehicles also include hybrid electric vehicles (HEV), fuel cell electric vehicles (FCEV) and other technological routes. However, in the current context, when the word is mentioned, it generally only refers to the pure electric vehicle route, that is, the familiar Tesla, as well as a number of new car-building forces.

The core component of the pure electric vehicle is the lithium battery.

Everyone knows pure electric cars, but not many people know about lithium batteries.

Lithium battery is a complex product with long upstream and downstream chains and strong professionalism, so it is impossible to explain all the details in one article. This article will focus on the core links, aiming to outline the basic technical map of lithium battery for readers, so that they can understand its core raw materials, key technologies and future trends.

Hundreds of billions of market driven by electric vehicles, as a kind of rechargeable battery, the working principle of Li battery is that lithium ion (lithium ion) moves directionally between positive and negative electrodes to achieve charge and discharge function. It is widely used in electric vehicles, consumer electronics and energy storage. Among them, lithium battery for electric vehicle, usually called power battery, is the application field with rapid growth at present and the most optimistic expectation in the future.

Data source: Dongguan Securities [3] according to Sullivan, the size of China's lithium battery market increased from 64.53 billion yuan in 2014 to 149.47 billion yuan in 2018, with a compound annual growth rate of 23.4%. If this is used as a reference, the output value of the power lithium battery industry is about 69.8 billion.

With the iteration of electronic products, the strong development of new energy vehicles and the government's requirements for energy saving and environmental protection, the market scale of lithium batteries is expected to further expand, and the market size is expected to reach 329.48 billion yuan in 2023. The corresponding power battery will achieve a scale of more than 160 billion [4].

Data source: in terms of the industrial chain, the upstream of lithium battery is raw materials such as lithium, graphite and rare metal minerals; the middle reaches are suppliers of key materials such as battery positive and negative electrodes, electrolytes and diaphragms, and the middle end is battery manufacturers. they make upstream raw materials into products of different specifications; downstream is the product application terminal, which can be roughly divided into three categories: power battery, consumer electronics and energy storage according to the application field.

Source of information: four key materials of lithium battery how does lithium battery generate electricity?

When the lithium battery is working, lithium ion participates in the redox reaction and converts chemical energy into electric energy. The evaluation indexes of a lithium battery product include energy density, cycle life, rate performance (discharge performance under different currents), safety performance and applicable temperature, etc.

From the cost composition of lithium battery, positive electrode, negative electrode, electrolyte and diaphragm are the four key raw materials, which account for a much higher proportion of the cost than other materials such as beam, connector and conductive agent-which is consistent with the basic working principle of lithium battery [4].

Data source: Zhengluo Junze [4] cathode material is the core material of lithium battery and the key factor to determine the performance of lithium battery, which has a direct impact on the final energy density, voltage, service life and safety of the product. it is also the most expensive part of lithium battery. For this reason, lithium batteries are often named after cathode materials, such as ternary batteries, which use ternary materials as positive electrodes.

The energy density of lithium battery refers to the electric energy released by the average unit volume or mass of the battery. the higher the energy density, the higher the mileage of the battery. This index is one of the important bases for whether a lithium battery can enjoy government subsidy.

The gap between different cathode materials is obvious, and the application fields are also different. Common cathode materials can be divided into lithium cobalt oxide (LCO), lithium manganate (LMO), lithium iron phosphate (LFP) and ternary materials (NCM).

Lithium cobalt oxide is the earliest commercialized cathode material, and its energy density is higher than that of Ni-MH and lead-acid rechargeable batteries, which first reflects the development potential of lithium batteries, but it is very expensive and low cycle life, so it is only suitable for 3C electronic products. Although the cost of lithium manganate is low, but its energy density is not good, it has a certain amount in the early slow electric vehicles, such as battery cars, and now it is mainly used in power tools and energy storage, but rarely in power batteries.

The standard cycle life of the battery refers to the number of charging and discharging cycles that the battery can undergo before the battery capacity declines to a specified value under a specific charge and discharge process. According to GB / T 31484-2015 "cycle life requirements and test methods for power batteries for electric vehicles", automobile power batteries are required to have a discharge capacity of not less than 90% of the initial capacity or not less than 80% of the initial capacity after 1000 charges and discharges.

At present, ternary materials and lithium iron phosphate are mainly used in the field of electric vehicles. In 2020, lithium battery cathode materials accounted for the first (46%) and the second (25%) [5], respectively.

(data source: public data collation) the core advantage of ternary materials is their high energy density. Under the same volume and mass, the flight duration is significantly ahead of other technical routes. But its defects are also very obvious: poor safety, impact and high temperature environment, the ignition point is relatively low. In recent safety tests such as acupuncture and overcharging with high heat, large-capacity power ternary batteries are very difficult to pass. It is the defect of safety performance that has been limiting the large-scale assembly and integration application of ternary material technology.

Lithium iron phosphate is just the opposite of ternary materials, the energy density and life span are average, but the safety is very excellent. Its crystal structure is a unique olivine type, and the spatial skeleton structure is not easy to deform, so that it can remain stable in high temperature environment. Ternary materials begin to decompose and release oxygen under the condition of about 150 ℃ ~ 250 ℃, which leads to electrolyte combustion. In comparison, the decomposition temperature of lithium iron phosphate is about 600 ℃. The safety advantage is very obvious.

Based on the above advantages, lithium iron phosphate can pass the safety tests that many ternary batteries cannot pass; on the other hand, the service life of lithium iron phosphate battery also has a great advantage, and its cycle number is far higher than that of other technical routes. this is in response to two key demands of electric vehicle consumers: safety and durability.

At present, the installed capacity of ternary batteries has declined, and the market share of lithium iron phosphate batteries is increasing rapidly. Statistics show that in 2020, the cumulative sales of domestic power batteries reached 65.9GWh, of which ternary lithium battery co-installed 38.9GWh accounted for 61.1%, down 4.1%; lithium iron phosphate battery 24.4GWh, accounting for 38.3%, increased by 20.6%, becoming the only type of power battery whose sales increased year-on-year [7].

In addition to safety advantages, another major factor in the rapid increase in sales of lithium iron phosphate is cheapness. For a long time, the main reason for the high cost of raw materials for ternary batteries (accounting for nearly 90%) is the high demand for cobalt [6]. Cobalt is a rare mineral, which is very expensive and unstable, the price fluctuates violently, and the supply chain is very fragile, which can easily affect the downstream industry.

In the early years, due to the existence of government subsidies, the high cost of ternary batteries is not prominent, but with the continuous decline of subsidies in recent years, the cost pressure is becoming more and more heavy, forcing battery manufacturers to find less alternative materials.

The cost advantage of lithium iron phosphate is concentrated in that it does not contain cobalt, and even if the ton price is high, it is much lower than that of ternary materials.

Data source: Guoxin Securities [8] at the same time, with the rapid increase in the number of charging piles, it can also make up for the battery life problem of lithium iron phosphate. Typical Lithium Iron Phosphate electric car is 300~400km, which is enough to meet the traffic demand in the city. The ternary battery can not reflect the core advantages in this application scenario.

Driven by both cost and infrastructure, it is not surprising that more and more car companies choose lithium iron phosphate technology. Even Ningde Times, a power battery giant that started with ternary batteries, is rapidly increasing its capacity of lithium iron phosphate batteries and supplying lithium iron phosphate batteries for the standard battery life version of domestic Tesla Model 3.

However, the development of ternary batteries has not stagnated. The long-term trend of this technical route is to reduce the cost through the ratio of high nickel and low cobalt, that is, the so-called high nickel ternary materials.

According to the proportion of nickel, cobalt and manganese, ternary materials can be divided into four main types: 111, 523, 622 and 811. From the perspective of market share, the current 5-series (i.e. 523) ternary materials are still the mainstream. The market share of more than 50% of the ternary material market in 2020 is more than 50%. The market share of 8 series (i.e. 811) batteries has increased from 6% in 2018 to 24% in 2020 with great potential [9] [10].

On the one hand, the high-nickel ternary battery reduces the expensive use of cobalt metal, and the cost is more controllable; on the other hand, the battery capacity is greatly increased, which is more in line with the needs of consumers. In recent years, the mileage of domestic electric vehicles has increased rapidly, thanks to the high nickel battery.

But correspondingly, the increase of nickel content means a rapid increase in the difficulty of processing, and the safety of the hidden danger is further reduced. In 2020, when the 811 battery was assembled on a large scale, spontaneous combustion accidents occurred frequently, causing this technical route to be questioned.

Only GAC Aion S, the first model to use 811 battery on a large scale, is also the oldest model of 811 new energy vehicle at present. From May to August in 2020, there were three spontaneous combustion accidents in succession, and this is just the tip of the iceberg where the battery caught fire. The safety defect of high-nickel ternary materials is a problem that battery manufacturers must solve, otherwise it is difficult to persuade passenger car consumers to buy, let alone be used in commercial vehicles with higher safety requirements.

In addition to Ni-Co-mn (NCM) ternary material, there is also a kind of Ni-Co-Al (NCA) alloy as cathode ternary material. Compared with NCM, the energy density of NCA is further improved, but the safety performance is not much improved. At present, Tesla is the most important user of Ni-Co-Al batteries. In April 2020, he applied for a patent for a new production technology that can improve battery life.

However, although favored by the leader, the NCA technology route is very rare in China, accounting for only 4% of shipments in the domestic ternary material market in 2020, and only Panasonic is the main manufacturer in the world at present.

The negative electrode material of lithium battery is made of paste adhesive made of active material, binder and additive, then smeared on both sides of copper foil and pressed by drying and rolling. Its function is to store and release energy and mainly affect the cycle performance of lithium battery.

According to the active materials used, negative materials can be divided into two categories: carbon materials and non-carbon materials.

Carbon series materials include graphite materials (natural graphite, artificial graphite and mesophase carbon potential spheres) and other carbon series (hard carbon, soft carbon and graphene).

Non-carbon materials can be subdivided into titanium-based materials, silicon-based materials, tin-based materials, nitrides and metal lithium.

(source: public data collation) unlike cathode materials, the negative electrode of lithium battery has the same many routes, but the final product is very single, and artificial graphite is the absolute mainstream. Data show that China shipped about 307000 tons of man-made graphite in 2020, accounting for 84% of the total shipments of negative materials, a further 5.5% increase over the 2019 level [3].

Compared with other materials, artificial graphite has good cycling performance, superior safety, mature process, easy access to raw materials and low cost, so it is a very ideal choice.

The core problem of graphite anode is that the theoretical upper limit of energy density of graphite anode material is 372mAh / g, while the products of the leading company in the industry can achieve the energy density of 365mAh / g, which is close to the theoretical limit, and the room for improvement in the future is very limited, so there is an urgent need to find the next generation of alternatives [13].

Among the new generation of negative electrode materials, silicon-based negative electrode is a hot candidate. It has extremely high energy density, and the theoretical capacity ratio can reach 4200mAh / g, which is much higher than that of graphite materials [14]. However, as an anode material, silicon also has serious defects. Lithium ion intercalation will lead to serious volume expansion, damage the battery structure and lead to the rapid decline of battery capacity. At present, one of the popular solutions is to use silicon-carbon composites, silicon particles as active materials to provide lithium storage capacity, while carbon particles are used to cushion the volume change of negative electrodes during charge-discharge and improve the electrical conductivity of materials. At the same time, the agglomeration of silicon particles in the charge-discharge cycle is avoided.

Based on this, silicon-carbon anode material is considered to be the most promising technical route, and gradually gets the attention of enterprises in the industry chain. Tesla's Model 3 has used an artificial graphite negative battery mixed with 10% silicon-based materials, and its energy density has successfully achieved 300wh/kg, which is much higher than that of batteries using traditional technology [14].

However, compared with graphite negative electrode, the higher cost of silicon-carbon negative electrode is also an obstacle in addition to the immature processing technology. At present, the market price of silicon-carbon anode material is more than 150000 yuan / ton, which is twice that of high-end artificial graphite anode material. In the future, battery manufacturers will also face similar cost control problems with cathode materials.

Electrolyte electrolyte is mainly used as the carrier of ion migration in lithium battery to ensure the transport of ions between positive and negative electrodes. It has a certain impact on battery safety, cycle life, charge and discharge rate, high and low temperature performance, energy density and other performance indicators.

The electrolyte is generally composed of high-purity organic solvents, electrolyte lithium salts and additives according to a certain proportion. According to quality, solvent quality accounts for 80%-90%, lithium salt accounts for 10%-15%, additives account for about 5%; by cost, lithium salt accounts for about 40%-50%, solvents account for about 30%, and additives account for about 10%-30% [15].

Compared with the other three materials, lithium battery requires the most complex electrolyte, which requires a variety of characteristics:

The ionic conductivity is good, and the ion migration resistance is low.

High chemical stability, no harmful side reactions with electrode materials, electrolytes, diaphragms, etc.

Low melting point, high boiling point, keeping liquid over a wide temperature range

The utility model has the advantages of good safety, uncomplicated preparation process, low cost, non-toxic and non-pollution.

At present, lithium hexafluorophosphate (LiPF6) is the mainstream lithium salt solute because of its good performance and low cost. It has good solubility and high electrical conductivity in all kinds of non-aqueous solvents, relatively stable chemical properties, good safety and little environmental pollution. But the defect is also obvious: lithium hexafluorophosphate is sensitive to water, and its thermal stability is poor, so it may begin to decompose at a minimum of 60 ℃, and the battery performance will decay rapidly. The cycle effect in low temperature environment is relatively general, and the temperature range is narrow.

In addition, lithium hexafluorophosphate requires very high purity and stability, and the production process involves harsh working conditions such as low temperature, strong corrosion, no water and no dust, so it is difficult to produce.

In the new generation of lithium salts, lithium difluorosulfonimide (LiFSI) is considered to be expected to replace lithium hexafluorophosphate. Compared with traditional lithium salts, LiFSI has higher thermal stability, and has advantages in electrical conductivity, cycle life, low temperature performance and so on.

However, limited by the production process and production capacity, the cost of LiFSI is too high, far exceeding lithium hexafluorophosphate. In order to control the cost, LiFSI is still more used as electrolyte additive than lithium solute in practical commercial use.

Source of information: Changjiang Securities [16] diaphragm lithium battery diaphragm is a thin film between positive and negative electrodes, which can be used to separate positive and negative electrodes to prevent short circuit. The separator is infiltrated in the electrolyte, and there are a large number of micropores on the surface that allow lithium ions to pass through. The material, number and thickness of the micropores will affect the speed of lithium ions passing through the separator, and then affect the discharge rate and cycle life of the battery.

Polyolefin is a commonly used separator material for lithium battery, which can provide good mechanical and chemical stability for lithium battery separator. Polyolefin can be divided into three categories: polyethylene (PE), polypropylene (PP) and composite materials.

The selection of diaphragm materials is related to the cathode materials. at present, polyethylene is mainly used in ternary lithium batteries, while polypropylene is mainly used in lithium iron phosphate batteries.

In addition to the materials, the preparation process also has a certain effect on the properties of the diaphragm.

At present, the production technology of lithium battery separator can be divided into two categories: dry process and wet process.

The dry process, also known as melt stretching (MSCS), can be further subdivided into unidirectional stretching and biaxial stretching. The development time of this technology route is long and more mature, and it is mainly used in the production of PP films. In addition, the biaxial stretching process is no longer the mainstream preparation process because of the poor performance of the finished product, which is only used in medium and low-end batteries.

The dry process has the characteristics of simple, low cost and environment-friendly, but the product performance is poor, so it is more suitable for low-power and low-capacity batteries. As mentioned above, lithium iron phosphate battery happens to have the defect of low energy density, so the diaphragm using dry process is mostly used in this technical route.

The wet method, also known as thermally induced phase separation (TIPS), is different from the dry process which only stretches the base membrane, the wet method will coat the surface of the base membrane to improve the thermal stability of the material. Compared with dry preparation, the diaphragm prepared by wet process has obvious advantages in performance, such as thinner thickness, better tensile strength, higher porosity, more uniform pore size and higher transverse shrinkage. In addition, the wet diaphragm has higher puncture strength, which is more conducive to prolonging battery life, and is more suitable for the development direction of lithium battery with high energy density. At present, it is mainly used in ternary battery.

However, compared with the dry process, the wet process is relatively complex, high cost and easy to pollute the environment.

At present, the main market trend of diaphragm materials is very certain. As it is more in line with the requirements of the high energy density of the power battery, it can prolong the battery cycle life and increase the high-rate discharge capacity of the battery, the wet process is rapidly replacing the dry process. The data show that the market share of wet-process lithium battery diaphragm surpassed that of dry-process diaphragm for the first time in 2017, and in 2018 only a year later, the market share rose further to 65%.

Data source: head Leopard Research Institute [17] in addition to the raw materials, the packaging technology of lithium battery also has a significant impact on the final performance of the battery. Even if the material formula is the same, the finished products produced by different processing processes are different in terms of safety, energy density and cycle life.

Currently, packaging technologies can be divided into three categories:

Square battery, that is, square single battery. The core gap of this type of battery is smaller, the internal material is more compact, the battery is not easy to expand under the limitation of high hardness, and the safety is relatively high. At the same time, the shell uses aluminum-magnesium alloy with lower density, lighter weight and higher strength to further strengthen the internal protection, but the corresponding production process is not complicated. However, the consistency of the square battery is poor, and because it can be customized according to the demand, there are many models on the market and the process is not unified.

Consistency means that in the battery pack, the initial performance indexes of single cells are similar, such as capacity, temperature characteristics, cycling and so on. If the performance of the single cell is too different, the service life of the battery pack will be seriously affected after grouping.

Although the round battery and the square battery belong to the hard shell packaging route, but the size is smaller, the cell consistency is good, the energy density of the single cell is relatively high, the grouping is more flexible, the production process is mature and the cost is low. The defect is that the overall performance is general, the number of cells in the battery package is relatively large, the weight is large, and the utilization rate of the cylinder to the space is not good, resulting in low energy density.

The performance of the soft bag battery is the best of the three routes, with flexible size, high energy density and light weight. However, the mechanical strength is not high, the production process is more complex, the production cost is high, and the ratio of performance to price is average.

From the market share point of view, the current square battery with a higher performance-to-price ratio, substantially ahead of other technological routes. In 2019, the installed capacity of domestic square batteries was 52.73GWh, an increase of 24.8% over the same period last year, accounting for 84.5% of the total installed capacity, which is the only technical route to maintain positive growth over the same period last year.

Data source: Guoyuan Securities [18] in addition to three mature packaging technologies, lithium batteries currently have new CTP technology, and derived two new products: "blade battery" and "CTP battery", both of which are upgraded in the form of square batteries.

CTP (Cell To Pack) technology means that the cells are grouped directly, skipping the intermediate link of the battery module. On the one hand, this technology improves the space utilization in the battery pack and increases the charge; on the other hand, it reduces the weight and greatly increases the energy density of the whole battery pack.

At present, the blade battery represented by BYD chooses to cancel the module completely, while the CTP battery in Ningde era takes the route of integrating small modules into large modules.

These two routes have their own advantages and disadvantages, but they are both in the early stage of commercialization, and the manufacturing process and scale production still need to be improved, which can not replace the traditional technology on a large scale in a short time.

Photo Source: Citic Securities [19] Summary as mentioned at the beginning, the lithium battery industry chain is long and complex, involving many industries, and cannot be clearly described in just a few thousand words. This paper chooses to cover the four core materials and three processing processes, and does not involve the related processes and materials of the whole battery package.

On the whole, the future development direction of lithium battery is clear: either increase the energy density or optimize the cost of existing products. Whether it is the dispute between lithium iron phosphate and ternary materials of cathode materials, or the selection of diaphragm process and solute in electrolyte, it is inherited here.

This is undoubtedly a good time for power batteries: under the rapid growth of consumer demand for electric cars, electric vehicles have become national key projects and have been strongly supported by policies. Driven by both policy and market demand, enterprises in the lithium battery industry chain also have a strong willingness to innovate, continue to optimize the existing production processes, and new technological breakthroughs occur from time to time.

New processes and new materials bring products with better performance, and more mature production technologies bring more large-scale production, thus reducing product prices, which is the basic path for the commercialization of new technologies. Enterprises that can take the lead in breaking through will naturally be able to occupy the market first and occupy a place in the era of new energy. Other companies also have the opportunity to replicate the trillions myth cast with ternary batteries in the Ningde era.

For consumers, things are much simpler. It is better than anything else to be able to drive an electric car that is more powerful, safer and cheaper.

References:

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Http://www.gov.cn/zhengce/content/2020-11/02/content_5556716.htm

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This article comes from the official account of Wechat: fruit Shell hard Technology (ID:guokr233), author: Chen Juanlei, Editor: Yimeng, Common paste

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