Lithium battery key technology
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2023/10/27 15:28:50
Lithium-ion battery development began in the consumer field, and is currently developing rapidly in the field of power and energy storage. What are the key technologies of power lithium battery and energy storage lithium battery? What are the new technological development directions of battery materials?
01
Lithium battery technology route
Lithium-ion battery refers to a secondary battery (rechargeable battery) with lithium as an energy carrier, when charging lithium ions out of the positive electrode, through the electrolyte and diaphragm, embedded in the negative electrode, discharge occurs in the opposite process, also known as rocking chair battery.
Lithium-ion batteries are divided into lithium iron phosphate batteries and ternary lithium batteries according to different positive electrode materials.
Lithium iron phosphate material is rich in production resources, and its cost, cycle life and thermal stability are better than terpolymer materials, which is suitable for commercial vehicles, middle and low-end passenger vehicles, energy storage and other fields. The theoretical specific capacity (energy density) of terpolymer lithium battery is 60% higher than that of lithium iron phosphate, higher charging rate, good low temperature performance, and suitable for middle and high-end passenger cars and other fields.
Comparison of performance of lithium iron phosphate (manganese) and ternary lithium batteries
Lithium battery packaging technology
Lithium-ion batteries are divided into square batteries, soft pack batteries and cylindrical batteries according to different packaging processes.
Lithium-ion batteries are classified according to the packaging process
The advantages of the square battery are high packaging reliability, simple structure, high energy density of the single unit, high efficiency of the system group, relatively good stability, the disadvantage is that there are many models, the process is difficult to unify, the monomer difference is larger, so that the system life is lower than the monomer life.
The soft pack battery uses aluminum-plastic film packaging, the advantages are high energy density, small battery group, long cycle life, the disadvantage is that high-end aluminum-plastic film relies on imports, low production efficiency, and low yield.
Cylindrical battery hard shell package reliability is higher, the advantage is that the battery consistency is higher, the process is mature, the cost is lower, the battery product yield, the heat dissipation performance is better, but the disadvantage is that the group after the heat dissipation design is difficult, the system energy density is low.
Analysis of advantages and disadvantages of three kinds of lithium-ion batteries
02
Power lithium battery technology route
Lithium iron phosphate power battery returned to the dominant position. In the past three years, with the decline of policy subsidies, the advantages of lithium iron phosphate in cost and safety gradually emerged, the market installed capacity rose rapidly, the market proportion increased year by year, and the installed capacity of terpolymer batteries exceeded by 2021, and the share of upper half power batteries increased to 55% in 2022.
Change in the proportion of installed capacity of China's power battery product structure from 2018 to 2022H1
China's power battery installed capacity maintains a rapid growth trend, to 2025 compound annual growth rate of 49%. Driven by the rapid growth of China's new energy vehicles, China's power battery installed capacity reached 110.1GWh in the first half of 2022, an increase of 109.8% year-on-year, and is expected to exceed 280GWh in 2022, and will exceed 750GWh in 2025.
In terms of high specific energy, the energy density of the ternary soft pack battery reaches up to 300Wh/kg. At present, the specific energy of the ternary square shell battery is close to 300Wh/kg, and the system energy density reaches 255Wh/kg. The energy density of the lithium iron phosphate blade (square) battery is close to 170Wh/kg, and the system energy density is more than 140Wh/kg. The specific energy of the ternary soft pack battery has reached 300Wh/kg, and the energy density of the system is close to 220Wh/kg.
Development of energy density of single structure system of power battery
Power lithium main technical direction
In terms of high safety, at this stage, the safety performance of the battery cell is mainly improved through the use of body safety, process safety and fire safety. Body safety mainly relies on non-combustible and non-combustible electrolyte, high melting point diaphragm and cathode material modification and coating to improve the body safety of the battery.
Power battery safety prevention and control technology
In terms of long life, the service life of lithium iron phosphate batteries is generally higher than that of ternary batteries. The service life of lithium iron phosphate blade battery is more than 5000 times, followed by the ternary soft pack battery, the service life is more than 3000 times, and again it is the square battery, the service life is more than 2000 times, and the service life of the cylindrical battery is slightly lower, about 1000 times.
In terms of fast charging performance, the terpolymer battery ratio is developing from the current 2C to 5C ratio, and the charging time is reduced by 60%. Many companies are improving the speed of ternary battery replenishment, and improving the fast charging performance of the battery by improving the charging voltage and the battery's high current tolerance.
Analysis and development trend of power battery technology in China
03
Energy storage lithium battery technology route
Large-scale energy storage is the main application scenario
China's energy storage battery shipments maintain a rapid growth trend, with an average annual growth rate of more than 50% in the next three years. In 2021, China's energy storage battery shipments reached 48GWh, an increase of 167%, and the installed capacity is expected to exceed 90GWh in 2022, an increase of 88%, and will exceed 324GWh in 2025.
China's Lithium Battery Shipments and Forecast (GWh) from 2019 to 2025
Data source: GGII
Domestic energy storage batteries are mainly used in large-scale energy storage (power system energy storage), communication system energy storage, home energy storage and portable energy storage. Large-scale energy storage is the main application scenario of energy storage batteries, mainly used in power generation side, grid side and user side of the energy storage system, the shipment accounted for 61%, followed by communication system energy storage, mainly used for communication base station backup power, accounting for 25%, home energy storage products are mainly exported to foreign countries. Portable energy storage accounted for the least, only 3%.
Shipment structure of domestic energy storage batteries in 2021
Data source: GGII
Many companies have entered the local energy storage battery market with energy storage batteries
Energy storage batteries are in a stage of rapid development, and the market pattern is uncertain. With its strong control capability and scale advantage, Ningde Times has established extensive cooperation with State Grid, five power generation groups, Costar, Xingyun Shares, Sunshine Power Supply and other enterprises, temporarily ranking first; With the help of overseas markets, Penghui Energy rapidly expanded in home energy storage, occupying the second place in domestic shipments; Byd is deeply engaged in European and American markets, with stable customer and channel advantages, temporarily ranking third in China.
Global Energy storage battery Shipments of Chinese Energy storage battery Companies in 2021 (MWh)
Data source: CNESA
The development trend of energy storage cell products is product standardization, large cell, and de-modularization, and various companies are entering the industry and trying to become bigger and stronger. Three years later, there will be a strong situation, and small and medium-sized players who do not have scale advantages and high-performance cell research and development and design capabilities will be accelerated to be eliminated.
Major new energy storage battery projects in China in 2022
Lithium iron phosphate battery has become the mainstream route in China
Lithium battery performance requirements include energy density, power density, cost, life and safety. Energy storage applications have relaxed the requirements for the energy density and power density of the battery, and more emphasis is placed on reducing the cost of storage power, and the energy storage battery needs to have low cost, long life, and ensure the safety of the battery application.
Lithium iron phosphate battery performance and energy storage needs are high fit, has become the mainstream route in China.
Ternary lithium batteries have high energy density and power density, but the cost is high and the safety is relatively weak. In June 2022, the Comprehensive Department of the National Energy Administration "Twenty-five Key Requirements for Preventing Power Production accidents (2022 version) (draft for comment)" proposed that medium and large electrochemical energy storage power stations should not use ternary lithium batteries, sodium-sulfur batteries, and should not use echelon power batteries. Lithium iron phosphate batteries have become the main choice for energy storage batteries because of their excellent safety, long cycle life, abundant metal resources, low cost and environmental protection.
Development direction of large-scale energy storage technology
The scale of large-scale energy storage installations is usually above MWh level, and large cells are expected to become the mainstream.
Large-scale energy storage system is an important facility to promote the large-scale application of renewable energy and the construction of a new power system, which can play the role of peak regulation, frequency modulation, standby capacity, smooth output, and alleviate grid congestion, including power generation side, grid side energy storage, etc., usually in dozens or even hundreds of MWh, and the battery cell used is mainly large-capacity square battery.
In energy storage applications, large capacity cells 280Ah and above can effectively reduce the cost of energy storage system, and reduce the difficulty of integration, and have obvious advantages, and are gradually replacing the original 50Ah and 100Ah cell products in power storage scenarios.
Advantages and challenges of 280Ah and above large cells
The development trend of large power storage cells is obvious. On the demand side, the attention of owners and investors of large power storage facilities to 280Ah large cells is rising rapidly, and Huaneng, China Energy Construction and other owners require that the capacity of a single unit is not less than 280Ah in their latest energy storage battery bidding. On the supply side, since the launch of 280Ah battery cells by Ningde Era in 2019, more than 10 domestic battery companies have launched 280Ah battery products; Haichen, Zhongchuang Xinhang and other cell manufacturers have increased the production of 280Ah cells.
Expansion of domestic 280Ah battery production line since 2020 (Part)
Development direction of household storage technology
The requirements for battery energy density in household scenarios are relatively low, and the main impact on user experience is the overall product design, including battery management and whole-house energy allocation, etc., and the requirements for battery cell performance are relatively relaxed, mainly emphasizing safety and cost reduction.
The scale of household energy storage system is 10kWh level, large cylinder battery (unit capacity 10Ah-50Ah), square (50Ah-300Ah), soft package (30Ah-80Ah) scheme has been selected by the company, and the current battery cell packaging route for household storage and production is not finalized.
Soft bags, cylinders, etc. can be used as household storage cell options
Small batteries may become the mainstream of household storage. At present, the European household storage market is experiencing product iterations of low pressure to high pressure systems. The high voltage platform can reduce the current, thus controlling the system heat generation and improving the discharge efficiency. When the capacity of the energy storage system remains unchanged, the corresponding cell capacity of the high voltage system decreases. For example, the low-voltage platform energy storage cell is mostly 100Ah, and the high-voltage platform gradually transitions to 50Ah. Small capacity batteries below 100Ah still have a long application life cycle in the field of household storage.
04
Key technologies of battery materials
Five battery materials
Positive electrode, negative electrode, electrolyte, lithium copper foil, diaphragm are the main direct materials of lithium batteries.
Changes in the share of China's five key battery materials market from 2015 to 2021
Data source: EVTank
Anode material is the most important material cost, accounting for about 55%. Lithium-ion batteries are mainly divided into lithium iron phosphate batteries and ternary batteries by positive electrode materials, and power batteries have both, and energy storage batteries are almost all lithium iron phosphate batteries in China.
Anode materials account for about 14% of the total cost, including artificial graphite and natural graphite. Artificial graphite can be used in power batteries and energy storage batteries, while natural graphite is mostly used in consumer batteries.
Electrolyte accounts for about 13% of the total cost, and its main components are solutes, solvents and additives. Solutes, including LiPF6 and the new lithium salt LiFSI, are the main source of costs. The solvents are mainly cyclic carbonate and chain carbonate, including PC, EC, DMC, DEC and EMC, etc. The additives are mainly used for film formation, overcharge protection, low temperature resistance, flame retardant, increase magnicity, etc. The common products include VC, FEC, PS, LiBOB, DTD, LiDFOB, etc.
Lithium copper foil is electrolytic copper foil, and the cost accounts for about 8%. Lithium copper foil is used for lithium anode fluid collector.
Diaphragms account for 4% of the total material cost and are divided into wet and dry diaphragms. The main cost of wet diaphragm is PE, and the main component of dry diaphragm is PP.
Estimated market structure of lithium-ion battery materials in 2021
Data source: EVTank
The upstream raw materials of lithium batteries mainly include all kinds of minerals, including lithium ore, nickel ore, cobalt ore, manganese ore, iron ore and other metal resources as well as non-metallic mineral resources such as graphite ore, silicon, phosphate, smelting out of battery raw materials, mainly including positive electrode materials, negative electrode materials, membranes, electrolytes, lithium copper foil and so on.
Battery material industry chain panorama
In the upstream mineral resources of battery materials, cobalt, nickel and lithium rely on overseas imports. The global market share of China's battery materials such as positive/negative electrode/electrolyte/diaphragm is 55%/92%/86%/73%, respectively, but China's key basic materials cobalt, nickel and lithium only account for 1.95%/1.57%/6.31% of global reserves, and cobalt/nickel/lithium is dependent on imports. With the rapid growth of demand for new energy vehicles, the cobalt/nickel/lithium market is relatively prosperous.
Positive electrode material
Lithium iron phosphate supply is tight in 2021-2022, capacity expansion is accelerating, and there is a structural excess risk in 2023-2025. It is expected that domestic lithium iron phosphate shipments in 2022 will be about 950,000 tons, while the production capacity at the beginning of the year is 940,000 tons, and the product supply is tight. With the rapid release of lithium iron phosphate capacity in 2023, there is a risk of structural excess capacity.
Capacity planning and demand forecast of China's lithium iron phosphate material enterprises in 2021-2025
(Tons, incomplete statistics)
The supply of ternary materials from 2022 to 2025 is tight, and the capacity expansion of ternary materials enterprises is cautious. It is expected that the domestic shipments of terpolymer materials in 2022-2025 are predicted to be 62/88/123/1.7 million tons, while the production capacity at the beginning of each year is 62/100/125/1.55 million tons, and the supply of production capacity is relatively tight.
2021-2025 China ternary material capacity planning and demand forecast
(Tons, incomplete statistics)
Lithium iron phosphate develops in the direction of high pressure compaction, low temperature performance and high energy density. The performance of lithium iron phosphate material is close to the theoretical bottleneck, and the performance of the material itself is difficult to be greatly improved. Low-cost long-cycle lithium iron phosphate cathode materials are currently being developed. Materials currently under development include high pressure solid density, fast charge, high energy density materials (such as lithium iron manganese phosphate).
Ternary materials are developing in the direction of high nickel, low cobalt (cobalt-free), single crystal, quaternary, etc., and are also developing in the direction of coating and doping, solid lithium battery materials, lithium-rich manganese cathode materials and other technologies, in order to further improve the energy density and fast charge performance of batteries.
Negative electrode material
The production capacity of graphite anode in 2021-205 is relatively tight. The demand for graphite negatives in 2021-2025 is expected to be 78/109/146/196/2.7 million tons, respectively, while the production capacity at the beginning of the year was 53/81/133/213/2.59 million tons, respectively.
Capacity planning and demand forecast of China's anode material enterprises in 2020-2025
(Tons, incomplete statistics)
Artificial graphite anode is the mainstream anode material, accounting for more than 80% of the overall market market share, and the market share is still increasing.
Negative material subdivision product share
Silicon-based materials combine the advantages of high conductivity and stability of carbon materials and high capacity of silicon materials, and become the best choice for current power battery capacity. In the field of power, 5%-10% of silicon oxide is combined with graphite, and in the field of 3C, nano-silicon is combined with graphite, which can increase the energy density of the battery by 5%-10%.
At present, silicon-based materials are mainly doped with artificial graphite in the form of additives, which are mainly used in cylindrical power batteries, and the products are exported more. Due to the immaturity of silicon based material technology, the problem of silicon volume expansion has not been solved
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