Li-ion battery new technology

Li-ion battery new technology: focus on large cylinders, long cores and other innovation opportunities

1. Battery development: ultra-fast charging, safety and other performance is the main direction; focus on large cylinders, long cells and other structural innovation

1.1 Battery performance trends: battery factory layout of high energy ratio, ultra-fast charging and safety and other technical directions

Ningde Time, BYD and other core battery factories are laying out in the direction of high energy ratio, super fast charging and battery safety technologies, and the realization path includes structural innovation, material innovation, etc.

    Ningde Times, the leading battery factory, has laid out six directions such as high energy ratio, super fast charging and true safety, and the types of technologies include structural innovation, material innovation and management innovation. According to the official website of Ningde Times, we can see that Ningde Times has laid out in six directions of structural innovation, material innovation and management innovation, which are high specific energy, long life, ultra-fast charging, true safety, self-control temperature and intelligent management. Take super fast charging as an example, Ningde Time's super fast charging refers to the fastest 5 minutes to 80% charge, in terms of structure, multi-gradient pole piece and multi-ear method are adopted, specifically: ① multi-gradient pole piece: by regulating the gradient distribution of the porous structure of the pole piece, the upper layer of high porosity structure, the lower layer of high pressure solid density structure, perfectly taking into account the dual core of high energy density and super fast charging; ② multi-ear: developing multi-dimensional space (2) Multi-layer: the development of multi-dimensional space lug technology, which greatly improves the current bearing capacity of the pole piece and breaks through the technical bottleneck of high temperature rise of the battery cell during 500A direct charging.

1.2 New type of battery/structure innovation: large cylindrical, long cells, etc. are important layout directions for battery factories

We combed through the battery form, mass production progress, performance index and advantageous characteristics of major battery factories, which are actively laying out new battery forms such as large cylinders and long cells. Take Honeycomb Energy as an example, the second generation of its laminated long thin cell L600 has completed development and is expected to achieve mass production in Q3 2022; in terms of performance index, the capacity of L600 single cell has increased to 196Ah, energy density is more than 185wh/kg and volume energy density is more than 430wh/L, which has advantageous features such as high compatibility, high adaptability, high safety and long life.

(2) Large cylindrical: Tesla, BAK, EVERLIGHT, and other battery factories are laying out large cylindrical batteries. Take Tesla as an example, the 4680 battery adopts high nickel cathode + silicon carbon cathode material and electrodeless lug technology, with an energy density of 300Wh/kg, the battery capacity is 5 times higher than the current 2170 solution, and the output power is 6 times higher. In addition, it has advantages in energy density, power and charging efficiency.

2. Large cylindrical: laser applications are expected to increase; high equipment precision requirements

2.1 Large cylindrical battery: Take Tesla 4680 as an example, technical innovations such as dry electrode and electrodeless lug are worthy of attention

According to the paper, the 4680 cylindrical battery is a further structural innovation of the cylindrical battery from the smaller 1865 to 2170. Compared with the previously used 2170 battery, the 4680 battery significantly reduces heat generation, solves the heat dissipation problem of high energy density cells, and increases the peak power of charging and discharging, ultimately making the 4680 battery 5 times more energy and 6 times more power than the 2170 battery, while reducing the cost by 14% and increasing the range by 16%.

In terms of structural innovation and manufacturing process, the 4680 has three major technological innovations compared to previous batteries - dry electrode process, lugless (all lug), and CTC technology - which have resulted in lower cell production costs and greater performance improvements. Take the lugless technology as an example, the 4680 cell design turns the entire collector into lugs, the conductive path is no longer dependent on the lugs, and the current transmission is changed from transverse transmission along the lugs to the collector plate to longitudinal transmission in the collector, which reduces the resistance to 2mΩ and the internal resistance consumption from 2W to 0.2W.

2.2 Dry electrode process: low cost compared with traditional wet process, core lies in electrode formulation and film extrusion equipment

Maxwell dry electrode technology is suitable for current lithium battery chemistry and advanced new electrode materials, no solvent is used in the manufacturing process, and it can be extended to roll-to-roll production, and 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's dry electrode technology consists of three steps: (i) dry powder mixing, (ii) powder to thin coating molding, (iii) thin coating and fluid collection pressing, all three steps are solvent free. Maxwell's dry electrode process is scalable to current lithium-ion battery chemistries and advanced new battery electrode materials; specifically, Maxwell's proprietary dry process is used to mix the powder to form a final powder blend of active materials, binders and conductive additives, which is extruded and calendered to form The powder mixture is extruded and calendered to form a continuous, self-supporting dry-coated electrode film that can also be wound into rolls. Finally, the thin electrode layer is pressed together with the collector fluid to form the battery electrode.

(2) In terms of advantages, according to the paper "Dry Electrode Coating Technology" by Hieu Duong, Joon Shin & Yudi Yudi, the Maxwell dry electrode process can be applied to classical and advanced battery materials and can be extended to reel-to-reel production compared to traditional wet electrodes. (3) In terms of core technology, according to Battery World Online, the core technology of Maxwell's dry electrode process is the electrode formulation and film-forming extrusion technology and equipment.

In addition, dry electrodes can be realized by various methods such as pulsed laser and sputtering deposition, which require additional film annealing process compared to wet and Maxwell dry electrode processes. According to the paper "Solvent-Free Manufacturing ofElectrodes for Lithium-ion Batteries" by Brandon Ludwig, Zhangfeng Zheng, Wan Shou, Yan Wang & Heng Pan, unlike the wet electrode preparation process, dry electrodes can be fabricated by pulsed laser deposition. The dry electrode process can be achieved by various methods such as pulsed laser and sputtering deposition, which does not require drying, but requires additional thin film annealing 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 ① Paste casting process: Lithium battery electrodes are made by casting a paste (containing active material in solvent, conductive carbon and binder) on a metal collector. The most common binder is PVDF (pre-dissolved in the solvent NMP), and the resulting slurry is mixed and cast on the collector, which must be dried to evaporate the solvent to produce a dry porous electrode. The drying takes a long time, typically 12-24 hours at 120°C. Also, because NMP is costly and contaminating, a recovery system must be installed to recover the evaporated NMP during the drying process (adding significant capital investment).

Solvent-based electrostatic spray deposition: Electrode material is applied to the collector using solvent-based electrostatic spray deposition, i.e., the deposited material is atomized in a nozzle and applied to the collector; electrodes constructed in this way exhibit similar properties to slurry-cast electrodes, with the similar disadvantage of requiring an intensive drying process that also requires time and energy (2 hours at 400°C). Lithium batteries are also produced using the spray technique, where each electrode assembly is sprayed onto the desired surface using an NMP-based coating, which still requires solvent evaporation.

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

The dry electrode process is less expensive than the traditional wet process, mainly in terms of labor cost, equipment investment, and plant space. According to the paper "Solvent-Free Manufacturing of Electrodes for Lithium-ion Batteries" by Brandon Ludwig, Zhangfeng Zheng, Wan Shou, Yan Wang & Heng Pan, for example, Battery Design Scenario 1 For example, the dry electrode production is 21.6%, 14.2%, and 13.1% less in direct labor, equipment cost, and plant area, respectively, than the wet electrode production, assuming that 100,000 cells are produced per year.

2.3 Lugless (all-lug) technology: reduce the internal resistance of the battery, laser welding volume upward, high equipment precision requirements

(all-ear) technology can significantly reduce the resistance and internal resistance consumption of the battery. According to Yulong Zhao's paper "Power Battery 4680 Full Lug Technology Scan": 1) Traditional cylindrical battery: positive and negative copper foil and aluminum foil diaphragm are stacked and wound, and a guide wire (lug) is welded at each end of the copper foil and aluminum foil in order to lead the electrode. (2) 4680 battery: the entire collector is turned into a lug, the conductive path no longer depends on the lug, the current is transferred from the transverse transmission along the lug to the collector to the longitudinal transmission of the collector, the entire conductive length is changed from 800-1000mm of the 1860 or 2170 copper foil length to The entire conductive length is changed from 800-1000mm of 1860 or 2170 copper foil length to 80mm (cell height), which reduces the resistance to 2mΩ and the internal resistance consumption from 2W to 0.2W, an order of magnitude lower.

Structural design features: the contact/conducting area of the lug at one end of the cell is equal to/greater than the collector. According to Tesla's "lugless" patent cited by GaoGong Lithium official WeChat public number, it describes at least one electrode as a lugless battery mount, specifically: 1) The lower level of the core: the end of the collector is left white and not coated with positive/negative materials, where the collector part can be understood as a generalized lug, Tesla The key to the "lugless" design is that the lug conduction area is exactly the same as the collector, or even the lug contact area and conduction area are larger than the collector conduction area through the cover diversified structure design; 2) the upper level of the core: if only one electrode without lug solution is used, the upper end is still the same as the 18650, 21700 core design. According to the patent analysis, only one end of the lugless connection can achieve the effect of reducing the internal resistance by 5 times.

(1) Production process: According to the official WeChat public number of Automotive Materials Network, which is cited in Automotive Home, there are two production processes for induction lugs, i.e., first cutting and then winding, and first winding and then laser die-cutting, specifically: ① First cutting and then winding: Through precise calculation, the material is cut into many parts before winding. When the winding reaches the preset energy, welding is performed. Laser die-cutting after winding: the material is wound directly regardless of width and size, and laser die-cutting is performed on the excess material after reaching the preset energy, which requires high precision.

(2) Equipment requirements: According to the official WeChat public number of Automotive Materials Network, citing the information of Auto House and GaoGong Lithium WeChat public number, from the perspective of production equipment, there are major changes in three aspects under the technology of non-polar lug (all-polar lug), specifically: ① coating process: the certain curved shape of all-polar lug causes higher requirements for equipment precision, and the white space on the outer ring will be more and more than the white space on the inner ring; ② cutting equipment: the requirements for laser die-cutting process are higher. (2) cutting equipment: higher requirements for laser die-cutting process, and gaps in material layer fit due to uneven cutting edges; (3) laser welding: the number of welded joints in laser spot welding of all lugs is increased by more than five times compared to 21700. Specifically, according to the welding process, for example, according to Zhao Yulong's paper "Power Battery 4680 full lug technology scan" content, the full lug and collector plate or shell connection, the laser welding technology requirements are higher, specifically, from the traditional two lug spot welding to full lug surface welding, welding process and welding volume have become more, laser intensity and focal length is not easy to control, easy to weld through burned to the inside of the core or no welding;. In addition, some companies propose to use press-fit rather than welding patents for the current collector.

We take Tesla's CTC technology as an example and analyze it as follows: 1) Unlike the 2170 battery pack which consists of four modules, the 4680 battery pack adopts CTC technology and the battery pack acts as the base plate of the vehicle. According to InsideEVs official website, from the cross-sectional view of the new Model Y structure battery pack shown at the Giga Berlin factory tour in October 2021, the 4680 battery pack directly eliminates the module design and adopts CTC technology, which is densely arranged in the vehicle chassis, i.e. the bottom of the Model Y equipped with the 4680 battery pack is hollowed out and the battery pack acts as the underbody. The battery pack serves as the underbody. In contrast, the 2170 battery in the Model Y has four modules - two short modules and two long modules. And our aerospace lithium company is also based on large cylindrical battery technology mastery is also a distant leader: http://www.optimum-china.com