Tesla 4680 battery

Lithium Battery New Technology Topic

Battery development: performance such as ultra-fast charging and safety is the main direction; focus on structural innovations such as large cylinders and long batteries

1.Battery performance trends

Battery factories lay out technical directions such as high energy ratio, ultra-fast charging, and safety. The core battery factories of CATL and BYD are all laying out in the technical direction of high energy ratio, super fast charging, and battery safety, and the realization path includes structural innovation and material innovation.

1) The leading battery factory CATL has laid out its layout in six directions, including high specific energy, ultra-fast charging, and true safety, and realized technological types including structural innovation, material innovation, and management innovation.

According to the information on the official website of CATL, it can be seen that CATL has laid out its layout in six major directions: structural innovation, material innovation, and management innovation, namely high specific energy, long life, ultra-fast charging, true safety, self-controlled temperature, and intelligent management. . Taking ultra-fast charging as an example, the ultra-fast charging of the CATL refers to charging to 80% of the battery in the fastest 5 minutes. In terms of structure, multi-gradient pole pieces and multi-pole ear methods are used. Specifically:

①Multi-gradient pole piece: By regulating the gradient distribution of the porous structure of the pole piece, the upper layer has a high porosity structure and the lower layer has a high compaction density structure, which perfectly takes into account the high energy density and super fast charging dual-core;

②Multi-pole ear: Develop multi-dimensional space pole ear technology, greatly improve the current bearing capacity of the pole piece, and break through the technical bottleneck of excessive temperature rise of the battery cell during 500A direct charging.

2) BYD and other battery factories are also making battery layouts in terms of safety, fast charging, and long battery life. Taking the BYD blade battery as an example, according to BYD’s official website, the “6S” technology concept creates the super advantages of super safety, super strength, super battery life, super low temperature, super life, and superpower;

The single cells with a height of 1.35 cm are arranged together in an array and inserted into the battery pack like a “blade”. When grouped, the modules and beams are skipped, and redundant parts are reduced to form a similar The structure of the honeycomb aluminum plate, etc. – the blade battery has achieved the super strength the battery through a series of structural innovations, while the safety performance of the battery pack has been greatly improved, and the volume utilization rate has also increased by more than 50%. In terms of fast charging, the blade battery can be charged from 10% to 80% in 33 minutes.

2.New-type batteries/structural innovation

Large cylinders and long cells are important layout directions of battery factories We have sorted out the battery form, mass production progress, performance indicators, and advantageous characteristics of the main battery factories. The main battery factories are actively deploying new forms of batteries such as large cylinders and long cells. Specifically:

1) Long battery cells: Honeycomb Energy, BYD, and other battery factories lay out the long battery cells. Taking Honeycomb Energy as an example, the second-generation L600 of its laminated long-thin battery has been developed and is expected to be mass-produced in Q3 2022; from the perspective of performance indicators, the L600 single cell capacity has been increased to 196Ah, and the energy density More than 185wh/kg, the volumetric energy density exceeds 430wh/L and has the advantages of high compatibility, high adaptability, high safety, and long life.

2) Large cylinder: Tesla, BAK, Yiwei Lithium Energy, and other battery factories lay out the layout of large cylinder batteries. Taking Tesla as an example, the 4680 battery adopts high nickel positive electrode + silicon carbon negative electrode material, electrodeless ear technology, the energy density reaches 300Wh/kg, the battery capacity is increased by 5 times and the output power is increased by 6 times compared with the current 2170 solution.

The cruising range of electric vehicles can be increased by 16%, and the cost per kilowatt-hour of the battery can be reduced by 14%; in addition, it has advantages in energy density, power, and charging and discharging efficiency.

Large cylinder: the amount of laser application is expected to increase; equipment precision requirements are high.

3.Large cylindrical battery

long cell byd blade battery

Taking Tesla 4680 as an example, technological innovations such as dry electrodes and electrodeless ears deserve attention.

According to the paper, the 4680 cylindrical battery is a further structural innovation after the cylindrical battery went from the smaller 1865 to 2170. Compared with the 2170 battery previously used, the 4680 battery significantly reduces heat generation, solves the heat dissipation problem of the high-energy-density cell, and increases the peak power of charging and discharging. Finally, the energy of the 4680 battery is 5 times that of the 2170 battery, and the power is the same as that of the 2170 battery. 6 times, while the cost is reduced by 14% and the cruising range is increased by 16%.

In terms of structural innovation and manufacturing process, compared with previous batteries, the main technological innovations of Tesla 4680 include three types-dry electrode process, electrodeless ear (full ear), and CTC technology, which reduces the production cost of battery cells and improves performance. achieve great improvement. Taking the electrodeless tab technology as an example, the 4680 cell design turns the entire current collector into a tab, and the conductive path no longer depends on the tab. To 2mΩ, the internal resistance consumption is reduced from 2W to 0.2W.

4.Dry electrode process

Compared with the traditional wet method, the cost is lower, and the core lies in the electrode formulation and film-forming extrusion equipment.

Maxwell dry electrode technology is suitable for the current lithium battery chemical system and advanced new electrode materials. No solvent is used in the manufacturing process, and it can be extended to roll-to-roll production. The core technology is electrode formulation and film-forming extrusion equipment.

1) According to the paper “Dry Electrode Coating Technology” by Hieu Duong, Joon Shin & Yudi Yudi, Maxwell dry electrode technology consists of three steps: (i) dry powder mixing, (ii) molding from powder to thin coating, (iii) The thin coating is laminated with the current collector, and all three steps are solvent-free;

Maxwell’s dry electrode process is scalable and can be adapted to current lithium-ion battery chemistries as well as advanced new battery electrode materials; See, powder blending using Maxwell’s proprietary dry process to form a final powder blend consisting of active materials, binders and conductive additives, which is extruded and calendered to form a continuous self-supporting dry-coated electrode membrane, The electrode film can also be wound into a roll shape, the processing conditions of the thin-coated electrode film can be adjusted, the material loading and coating thickness can be controlled, and a variety of dry-coated electrode structures can be prepared. Finally, the thin electrode layer and the current collector are pressed together to form the battery pole piece.

2) In terms of advantages, according to the paper “Dry Electrode Coating Technology” by Hieu Duong, Joon Shin & Yudi Yudi, compared with traditional wet electrodes, the Maxwell dry electrode process can be applied to classic and advanced battery materials, and can be Expanding to roll-to-roll production with reduced manufacturing costs, elimination of solvent toxicity, and improved battery performance (dry-coated electrodes deliver more power than wet-coated electrodes).

3) From the perspective of core technology, according to the battery world online WeChat public account, the core technology of Maxwell’s dry electrode process is electrode formulation and film-forming extrusion technology and equipment.

In addition, dry electrode can also be realized by pulsed laser and sputter deposition, which requires an additional thin film annealing process compared to wet and Maxwell dry electrode processes. According to the paper “Solvent-Free Manufacturing of Electrodes for Lithium-ion Batteries” by Brandon Ludwig, Zhangfeng Zheng, Wan Shou, Yan Wang & Heng Pan, different from the wet electrode preparation process, the dry electrode can be deposited by pulsed laser and sputtering, etc. A variety of methods are implemented, which do not require a drying process, but require the addition of a thin film annealing process due to the high temperature caused by pulsed laser deposition. The electrode preparation process proposed in this paper is as follows:

1) Wet electrode preparation process

①Slurry casting process: The lithium battery electrode is casted with slurry (including active material, conductive carbon and binder in the solvent) through the metal current collector. The binder is most commonly PVDF (pre-dissolved in the solvent NMP), and the resulting slurry after mixing is cast on the current collector, and a drying step must be performed to allow the solvent to evaporate to produce a dry porous electrode. Among them, drying takes a long time, generally 12-24 hours at a temperature of 120°C. At the same time, since NMP is high-cost and polluting, a recovery system must be installed to recover evaporated NMP during the drying process (increasing a large capital investment).

② Solvent-based electrostatic spray deposition technology: The electrode material is coated on the current collector by the solvent-based electrostatic spray deposition technology, that is, the deposited material is atomized in the nozzle and coated on the current collector; the electrode constructed by this method exhibits the same performance as the slurry Cast electrodes have similar properties, but also have similar drawbacks, namely, a time- and energy-intensive drying process (drying at 400°C for 2 hours). Lithium batteries are also produced using spray technology, even though NMP-based paint is used to spray each electrode assembly to the desired surface, which still requires solvent evaporation.

2) The dry electrode preparation process is realized by various methods such as pulsed laser and sputter deposition. Pulsed laser deposition is accomplished by focusing the laser on a target containing the material to be deposited, once the laser hits the target, the material vaporizes and deposits on the current collector; although no solvent is used, the deposited film must withstand 650-800 ℃ high temperature, while magnetron sputter deposition can reduce the required annealing temperature to 350℃. This method is representative of dry cell electrode fabrication, but the deposition rate is slow and requires high temperature annealing.

Compared with the traditional wet process, the dry electrode process has a lower cost, which is mainly reflected in the labor cost, equipment investment and plant area. According to the paper “Solvent-Free Manufacturing of Electrodes for Lithium-ion Batteries” by Brandon Ludwig, Zhangfeng Zheng, Wan Shou, Yan Wang & Heng Pan, taking battery design scheme 1 as an example, under the assumption that 100,000 battery packs are produced per year, Compared with the wet electrode preparation, the direct labor, equipment expenditure and plant area are reduced by 21.6%, 14.2% and 13.1% respectively.

5.Electrode ear (full pole lug) technology

Reduce the internal resistance of the battery, increase the amount of laser welding, and require high equipment precision.

The (full tab) technology can greatly reduce the resistance and internal resistance consumption of the battery. According to Zhao Yulong’s paper “Power Battery 4680 Full-Ear Technology Scan”:

1) Traditional cylindrical battery: positive and negative copper foils and aluminum foil separators are stacked and wound. In order to lead out the electrodes, both ends of the copper foil and aluminum foil are welded respectively A guide wire (tab). Take the 2170 battery as an example, the winding length of the 2170 battery is about 1000mm, and the resistance is about 23mΩ;

2) 4680 battery: the entire current collector is turned into a tab, the conduction path no longer depends on the tab, and the current flows from the tab to the current collector. The lateral transmission of the disk becomes the longitudinal transmission of the current collector, and the entire conductive length is changed from 800-1000mm (the height of the battery) to 80mm (the height of the battery) from the length of the 1860 or 2170 copper foil, which reduces the resistance to 2mΩ, and the internal resistance consumption is reduced from 2W to 0.2W. One order of magnitude.

Structural design features: the contact/conduction area of ​​one end of the cell is equal to/larger than the current collector. According to the official WeChat public account of Gaogong Lithium Battery, Tesla’s patent for “electrodeless ear” is quoted, which describes a battery device with at least one electrode being an electrodeless ear. Specifically:

1) The lower end of the winding core: the end of the current collector is left blank The positive/negative electrode material is coated, where the current collector can be understood as a generalized tab. The key to Tesla’s “electrodeless tab” design is that the conductive area of ​​the tab is exactly the same as that of the current collector. The contact area and conduction area are larger than the conduction area of ​​the current collector;

2) Level 1 of the upper end of the winding core: if only one electrode electrodeless ear scheme is used, the upper end is still the same as the 18650 and 21700 winding core design, and is connected to the outside through a conductive electrode ear; press According to the patent analysis, only one end of the electrodeless ear connection can reduce the internal resistance by 5 times.

Production angle: The process is divided into first cutting and then rolling and first rolling and then cutting, and the latter has high requirements on the precision of laser die-cutting.

1) Production process: According to the official WeChat account of Automotive Materials Network, citing Autohome, there are two production processes for electrodeless ears, namely, cutting first and then winding, and first winding and then laser die-cutting.

①Winding: Through precise calculation, the material is cut into many parts before winding, and the position of the cut can be easily aligned during winding, and welding is performed when the winding reaches the preset energy.

②Laser die-cutting after winding first: the material is wound directly regardless of the width or size. After reaching the preset energy, laser die-cutting is performed on the excess material, which requires high precision. If the gap between the two layers of materials is inconsistent, it may be cut. to the material, resulting in inconsistent internal resistance.

2) Equipment requirements: According to the official WeChat public account of Auto Materials Network, citing the information of Autohome and Gaogong Lithium Battery WeChat public account, from the point of view of production equipment, there are three major aspects under the non-pole ear (full pole ear) technology. Changes, in detail:

①Coating process: The certain arc shape of the full pole lugs requires higher precision of the equipment, and the outer ring will have more and more white space than the inner ring;

②Cutting equipment: laser die-cutting The requirements of the process are higher, and the uneven trimming causes gaps in the material layers;

③Laser welding: The number of solder joints of full-pole laser spot welding is more than five times higher than that of 21700. Specifically, taking the welding process as an example, according to the content of Zhao Yulong’s paper “Technical Scanning of 4680 Power Batteries All-pole Tabs”, the connection between the all-pole tabs and the collector plate or the shell requires high requirements for laser welding technology.

From the traditional spot welding of two tabs to the full tab face welding, the welding process and welding volume are increased, the laser intensity and focal length are not easy to control, and it is easy to weld through the inside of the cell or without welding;

In addition, some The company proposes a patent that the collector plate is press-fit instead of welding.

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