On June 18, 2024, the Ministry of Industry and Information Technology revised the "Standard Conditions for the Lithium-ion Battery Industry" and the "Management Measures for the Standard Announcement of the Lithium-ion Battery Industry", which marked the beginning of the road of "new quality productivity" for lithium batteries. Let's first understand what specific content has been revised in the "Normative Conditions".
Production and operation and process level
Enterprises should adopt production processes and equipment with advanced technology, energy conservation and environmental protection, safety and stability, and high degree of intelligence, and meet the following requirements:
1. Single battery enterprises should have the ability to monitor the uniformity of electrode coating, and the control accuracy of electrode coating thickness and length should reach or be better than 2μm and 1mm respectively; It should have the ability to control the water content in the production process and the electrode drying process technology under applicable conditions, and the water content control accuracy should reach or be better than 10ppm.
2. Single battery enterprises should have the ability to control electrode burrs during the shearing process, and the control accuracy should reach or be better than 1μm; It has the ability to control the alignment of electrodes during winding or lamination, and the control accuracy is up to or better than 0.1mm.
3. Single battery enterprises should have the ability to control environmental conditions such as temperature, humidity and cleanliness during liquid injection, and the dew point temperature should be ≤-30°C; It should have the ability to detect the internal short circuit high voltage test (HI-POT) online after the battery is assembled.
4. Battery pack enterprises should have consistent control capabilities such as open-circuit voltage and internal resistance of single batteries, and the control accuracy should reach or be better than 1mV and 1mΩ respectively; It should have the function of battery pack protection device, online detection ability and electrostatic protection ability, and the battery management system should have safety protection functions such as preventing overcharge, overdischarge, and short circuit.
5. Positive and negative electrode material enterprises should have the ability to control harmful impurities, and the control accuracy should reach or be better than 10ppb.
Product performance
(1) Battery
1. Consumer batteries. The energy density of the single battery ≥ 260Wh/kg, the energy density of the battery pack ≥ 200Wh/kg, and the volume energy density of the polymer single battery ≥ 650Wh/L. The cycle life of single cells and batteries is ≥ 800 cycles and the capacity retention rate is ≥ 80%.
2. Power batteries, which are divided into small power batteries and large power batteries. Small power battery. The energy density of the single battery ≥ 140Wh/kg, and the energy density of the battery pack ≥ 110Wh/kg. The cycle life of a single battery is ≥ 1000 times and the capacity retention rate is ≥70%, and the cycle life of the battery pack is ≥ 800 times and the capacity retention rate is ≥70%. High-power batteries are divided into energy type and power type. Among them, the energy density of the energy-type single battery using ternary materials ≥ 230Wh/kg, and the energy density of the battery pack ≥ 165Wh/kg; The energy density of energy-type single batteries using other materials such as lithium iron phosphate ≥ 165Wh/kg, and the energy density of battery packs ≥ 120Wh/kg. The power density of the power single battery is ≥ 1500W/kg, and the power density of the battery pack is ≥ 1200W/kg. The cycle life of a single battery is ≥ 1500 times and the capacity retention rate is ≥ 80%, and the cycle life of the battery pack is ≥ 1000 times and the capacity retention rate is ≥80%.
3. Energy storage batteries. The energy density of the single battery ≥ 155Wh/kg, and the energy density of the battery pack ≥ 110Wh/kg. The cycle life of a single battery is ≥ 6000 times and the capacity retention rate is ≥80%, and the cycle life of the battery pack is ≥ 5000 times and the capacity retention rate is ≥80%.
(2) Cathode materials
The specific capacity of lithium iron phosphate ≥ 155mAh/g, the specific capacity of ternary materials ≥180mAh/g, the specific capacity of lithium cobalt oxide ≥165mAh/g, the specific capacity of lithium manganese oxide ≥115mAh/g, and the performance indicators of other cathode materials can refer to the above requirements.
(3) Anode materials
The specific capacity of carbon (graphite) ≥ 340mAh/g, the specific capacity of amorphous carbon ≥280mAh/g, and the specific capacity of silicon carbon ≥480mAh/g.
(4) Diaphragm
1. 干法单向拉伸：纵向拉伸强度≥120MPa，横向拉伸强度≥10MPa，穿刺强度≥0.133N/μm。
2. 干法双向拉伸：纵向拉伸强度≥110MPa，横向拉伸强度≥25MPa，穿刺强度≥0.133N/μm。
3. 湿法双向拉伸：纵向拉伸强度≥110MPa，横向拉伸强度≥90MPa，穿刺强度≥0.204N/μm。
(5) Electrolyte
水含量≤20ppm，氟化氢含量≤50ppm，金属杂质钠含量≤2ppm，其他金属杂质单项含量≤1ppm，硫酸根离子含量≤10ppm，氯离子含量≤5ppm。
It can be seen from the above excerpt that the state is very eager to improve high-quality production capacity, and has split the specific goals into the production process and the use of raw materials, which can be described as comprehensive.
So high-quality production capacity is inseparable from high-quality production technology, before talking about process innovation, let's first understand some basic steps of lithium battery production.
Figure 1 illustrates the current state-of-the-art battery manufacturing process, which consists of three main components: electrode preparation, battery assembly, and battery electrochemical activation. First, the active material (AM), conductive additives, and binders are mixed with the solvent to form a homogeneous slurry. As a cathode, N-methylpyrolione (NMP) is commonly used to dissolve the binder polyvinylidene fluoride (PVDF), as an anode, and styrene-butadiene rubber (SBR) binder is dissolved in water with carboxymethyl cellulose (CMC). The slurry is then pumped into a groove die, coated on both sides of the current collector (aluminum foil for the cathode and copper foil for the anode), and sent to a drying plant to evaporate the solvent. Organic solvents (NMPs) commonly used in cathode slurries are toxic and have strict emission regulations. Therefore, during the drying process, cathode production requires a solvent recovery process, and the recovered NMP can be reused in battery manufacturing with a loss of 20%-30%. In the case of water-based anode slurries, harmless vapours can be vented directly into the surrounding environment. The calendering process below can help to adjust the physical properties of the electrode (bonding, conductivity, density, porosity, etc.). After all these processes, the finished electrodes are stamped and cut to the desired size to fit the battery design. The electrode is then sent to a vacuum machine to remove excess water. The moisture level of the electrodes will be checked after drying to ensure that side reactions and corrosion in the battery are minimized.
After the electrode is ready, it is sent to the drying room with a dry diaphragm for cell production. The electrodes and separators are wound or stacked layer by layer to form the internal structure of the battery. The aluminum and copper sheets are welded to the cathode and anode current collectors, respectively. The most common welding method is ultrasonic welding, and some manufacturers may opt for resistance welding for their battery design. The honeycomb stack is then transferred into the designed enclosure, and there is currently no consistent standard. Depending on the purpose of the battery, each manufacturer has its own preferences. Before the final sealing, the housing is filled with electrolyte to complete the battery production.
These batteries are subjected to an electrochemical activation step to ensure operational stability before they are delivered to the final product manufacturer. A stable solid electrolyte interface (SEI) layer prevents irreversible depletion of the electrolyte and protects the anode from overpotential during fast charging, resulting in the formation of lithium dendrites. The formation and aging process begins with charging the battery to a relatively low voltage (e.g., 1.5V) to protect the copper current collector from corrosion, followed by a period of rest to allow the electrolyte to moisten. The battery is charged and discharged at a low rate, such as C/20, and then gradually increased to ensure a stable SEI layer on the anode surface. For safety reasons, it is necessary to discharge the gases generated during the formation process. After or during the formation cycle, the battery is stored on an aging rack to complete electrolyte wetting and SEI stabilization. Another degassing step is scheduled before the battery is finally sealed for future use. Depending on the formation protocol and aging temperature, this step usually takes several weeks.
So how to find a new breakthrough point in such a mature production process, improve efficiency and quality at the same time, reduce costs and energy consumption, is a problem that the majority of lithium battery people need to think about. The author will discuss the innovation possibilities of lithium battery production process with you in the next few articles, so stay tuned.
Article source: Xiao Ming called
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