Background:During the charging and discharging process of lithium-ion batteries, electrode material expansion, SEI growth, thermal expansion and gas production may cause battery expansion, resulting in volume changes. Battery expansion is considered to be one of the key indicators to assess battery capacity and structural decline, and is also an early warning of serious safety incidents such as burning and explosion during battery abuse. There are mature methods to characterize the expansion behavior of square and soft pack batteries, but there is no mature and stable expansion characterization method for cylindrical batteries due to the particularity of their structure. At present, there are some methods to characterize the expansion of cylindrical batteries, such as vernier calipers, coordinate testing instrument, pressure film, strain gauge, image analysis method (CT tomography, neutron imaging, X-ray, ultrasonic, etc.), but these methods have low accuracy, can not be in-situ testing and other problems, unable to accurately and completely describe the expansion behavior of cylindrical batteries.In view of the shortcomings of the above test methods, some institutions developed a CCS1300-4 cylindrical battery in-situ expansion test system based on optical battery imaging technology for in-situ expansion characterization of cylindrical batteries. This method can measure the volume change of cylindrical batteries in situ, reconstruct the surface morphology and calculate the expansion amount in real time, and the optical detection accuracy can reach ±1μm. In this paper, two 21700 cylindrical batteries with different negative silicon content were tested using CCS1300-4 cylindrical battery in situ expansion test system to characterize the expansion behavior of the two cells during formation and charging and discharging, analyze the influence of different silicon content on the expansion behavior of the cells, and guide the application of silicon negative electrode and the design of cylindrical batteries.1.1 Experimental equipmentIn this paper, 21700 cylindrical battery expansion was characterized by CCS1300-4 cylindrical battery in situ expansion test system, which includes 4-channel test fixture and special test software. In situ dilatation test of 4 cylindrical batteries can be carried out simultaneously with charge and discharge instrument.1.2 Test PrincipleThe optically based battery volume imaging technology is used to conduct real-time three-dimensional reconstruction of the surface topography during the charging and discharging process of the battery, and calculate the volume and volume change during the charging and discharging process.1.3 Test MethodRemove the outer plastic film of the 21700 cylindrical battery, install it on the fixture of the equipment, open the software, and set the charge and discharge channel, sampling Angle, upper limit of alarm temperature and upper limit of alarm volume. The program starts, the battery rotates and performs a volume test, and the software automatically synchronizes the charge and discharge data with the volume test data.1.4 ConclusionIn this paper, the expansion behavior of two 21700 cylindrical batteries with different silicon content in the negative electrode was tested by using CCS1300-4 cylindrical battery in situ expansion test system. It is found that the content of silica has a significant effect on the volume expansion of the cylindrical battery, and the volume expansion of the battery itself has a large non-uniformity. Through the analysis of volume expansion data and surface topography dynamic change map, it can provide data support for the application of silicon anode materials and the structure design of cylindrical batteries, and help the development and quality control of lithium-ion batteries.

AbstractThere are many factors that affect the safety of lithium-ion power batteries. Among them, the battery safety problems caused by the cracking of the positive electrode plate are easy to produce burrs, abnormal protrections and fractures in the subsequent electrode assembly process, which have attracted much attention in recent years. In this paper, through the experiment of mixing design, the ratio of auxiliary materials in the anode material is optimized to reduce the roll elongation of the electrode sheet. At the same time, adjusting the thickness of the ceramic layer can effectively control the difference of the elongation of the active material coating area and the ceramic layer electrode sheet in the rolling process, reduce the arc rate of the electrode sheet after paving, and explore an effective method to solve the crack of the pole ear during the preparation of the positive electrode sheet of the power battery.1.1 Experimental process1.1.1 Specific experimental methodsThe solid content of ternary NCM811 is set at 95%, and the total solid content of PVDF, SP and KS6 is 5%. The content of solvent NMP in the slurry is fixed at 30%. The verification ratios of PVDF, SP and KS6 were 1%-2%, 1%-2% and 1.2% -2.4%, respectively. PVDF, SP, KS6 ratio optimization method using Minitab software, mix optimization design (DOE), simplex design diagram, extreme vertex design and center point strengthening scheme, 7 groups of experiments. 1.1.2 Slurry preparation of electrode sheetThe specific process is as follows: First, PVDF is dissolved in NMP solvent, PVDF solution with 7% solid content is formed in the agitator, and transferred to the stainless steel bucket for storage; Subsequently, SP, KS6 and NMP were pre-stirred in a blender for 30min; Then add the prepared PVDF solution and stir for 30min; Finally, the NCM811 is divided into two times according to weight and added to the stainless steel drum, each stirring time is 20min; In the above stirring process, the parameters of the agitator are set as the revolution speed of 25 revolutions /min and the rotation speed of 800 revolutions /min, and the total mixing time is 240min.2.1 Conclusion:In this paper, the elongation of the polar plate can be reduced by optimizing the content ratio of PVDF, SP and KS6 under the condition of obtaining the same compaction density. At the same time, the elongation after rolling can be controlled by controlling the thickness of the ceramic layer before rolling and the thickness after cold pressing (the best ratio is 120%±9%). Both effects can effectively reduce the arc rate of the positive electrode sheet after paving, and can solve the problem of the root of the pole ear cracking during the preparation of the positive electrode sheet of the power battery.

Liquid lithium batteries have become the mainstream of the industry, but there are still some problems in the application side that need to be solved. Whittingham first proposed and began research on lithium-ion batteries in the 1970s, and then in the 1990s, SONY invented a commercial liquid lithium battery. At present, liquid lithium batteries have become the mainstream of the industry with their advantages of high energy density, fast charging speed, long life and no pollution. However, at the same time, there are still some problems restricting the future development and application of liquid batteries.1) Safety issues: The electrolyte and diaphragm in the liquid lithium battery structure may cause safety issues. The problem of lithium dendrites: lithium ions are removed between positive and negative electrodes to achieve the charge and discharge of lithium batteries. However, when there are some abnormal conditions that make lithium ions cannot be normally removed, lithium dendrites may be formed. The accumulation of lithium dendrites to a certain extent may puncture the battery diaphragm, short-circuit the positive and negative electrodes, and then cause fire and other safety problems. Electrolyte problem: liquid lithium battery electrolyte commonly used lithium salt dissolved in volatile, combustible organic solvents, the safe operating temperature is generally lower than 80 ° C, so when the battery temperature is too high, combustion and explosion may occur. Problems with diaphragms: The ordinary diaphragms used in batteries have low thermal conductivity, which can reduce the rate of heat dissipation in lithium-ion batteries.2) Energy density problem: the current energy density ceiling of liquid lithium batteries is 300Wh/kg, and solid lithium batteries can reach a higher energy density by updating the material system, which can reach 700Wh/kg or more. In recent years, solid-state battery technology has rapidly improved and is expected to become a new generation of lithium battery technology. As early as 1830s, Faraday first discovered the remarkable conduction properties of heated solid silver sulfide and PbF2. Then in the 1960s, the solid electrolyte ushered in a turning point in development, and began to try to add the solid electrolyte to the battery. Subsequently, POE, sodium superionic conductor, hydride, LiPON, sulfide, antiperovskite and other solid electrolyte systems appeared successively. Along with the development of LiPON, the first thin-film battery was introduced in the 1990s. After entering the 21st century, the related research of solid electrolyte has been further developed. With the advantages of structural design and physical characteristics, solid-state batteries can naturally avoid the safety and energy density problems of liquid lithium batteries. Therefore, solid-state batteries have developed rapidly in recent years and are expected to become the next generation of lithium battery technolog Revolutionizing Energy Storage: The Rise of Solid-State BatteriesSolid-state batteries use solid-state electrolytes to replace the electrolyte and diaphragm in liquid lithium batteries. Solid-state batteries are a new technology that uses solid-state electrolytes to replace the electrolyte and diaphragm in liquid lithium batteries. The main material of the traditional liquid battery is the positive electrode, the negative electrode, the diaphragm and the electrolyte. In the process of charging and discharging, the electrolyte supplies some active lithium ions as conductive ions on the one hand, and provides ion channels so that lithium ions can move freely. The role of the diaphragm is mainly to make the normal passage of electrolyte ions, and to avoid internal short circuit caused by positive and negative electrode contact. In solid state batteries, because the physical form of solid state electrolysis can naturally isolate the positive and negative electrodes, the main material in solid state batteries is positive, negative and solid electrolyte, and the diaphragm is not necessary.Challenges and Potential of Solid-State Batteries: Enhancing Safety and Energy Density.Solid-state batteries can overcome the shortcomings of lithium-liquid batteries and achieve further breakthroughs in safety and energy density. In terms of safety, solid state batteries use non-combustible solid electrolyte, with no corrosion, no volatilization, no leakage, can inhibit the formation of lithium dendrites, natural isolation of positive and negative poles, and so on, with high safety. In terms of energy density, solid-state batteries can use materials such as lithium metal as a negative electrode instead of graphite, thereby increasing the energy density of the battery. However, solid-state batteries still face problems in material performance and cost, and the current large-scale industrialization is still facing certain challenges. The electrolyte material makes fast-charging weaker than liquid batteries. Compared with liquid batteries, solid-state batteries use solid electrolytes, so the ionic conductivity is relatively low, which makes the fast charging ability weaker than liquid batteries. Poor interface contact between solid electrolyte and electrode. In a liquid battery, the contact between the liquid electrolyte and the electrode is good, but in a solid battery, there may be a gap between the solid electrolyte and the electrode, and the solid-solid contact interface leads to poor stability. Solid-state batteries are expensive. According to the analysis of South Korean market research institution SNE, the high cost of solid-state batteries is mainly affected by two factors, one is the high cost of raw materials, including the high cost of lithium sulfur compounds; Second, the manufacturing cost is high, which is due to the high requirements of solid state battery production on raw material purity and synthetic environment, making the manufacturing cost higher.Key Differences Between All-Solid-State, Semi-Solid-State, and Liquid BatteriesThe all-solid-state battery differs greatly from the existing liquid battery system, while the semi-solid-state battery differs little from the liquid battery system. A semi-solid battery is a lithium battery that contains both solid and liquid electrolytes. In contrast, in addition to electrolytes, the main difference between liquid batteries and solid batteries is reflected in the negative electrode of the liquid battery graphite or silicon carbon, while the negative electrode of the solid battery is metal lithium. However, there is little difference between the semi-solid battery and the existing liquid battery system, some materials can be common with liquid batteries, including the need for diaphragms, etc., and the manufacturing process is also mostly overlapping.Evolution of Battery Technology: From Liquid to Solid State There are still difficulties in the current mass production of all-solid-state batteries, and semi-solid-state batteries may become transition products. At present, due to the mass production of all-solid-state batteries is still facing a series of problems, so the development and penetration of solid-state battery technology in the future will take some time. The semi-solid battery due to the small changes in the material system of the battery, the manufacturing process and technology can also follow the technical route of the liquid battery, so it may become a transition product from the liquid battery to the all-solid battery in the short term. It is expected that the technology of lithium batteries in the future will follow the development path of liquid lithium-ion batteries - semi-solid batteries - all-solid batteries. It is expected that the technological iteration path of solid-state batteries is electrolyte-negative-positive. From the perspective of research and development, solid-state batteries have three stages, the first generation is to replace the traditional electrolyte and diaphragm with solid electrolyte; The second generation uses lithium metal as a negative electrode material to increase the energy density; The third generation is based on the second generation, and further replaces the positive electrode material with a higher energy density material to further improve the energy density of the battery. Solid state batteries gradually increase energy density through battery material scheme iteration. Taking Solid power's product iteration route as an example, its first solid-state battery product uses "electrolyte + silicon anode +NCM811", the energy density can reach 390Wh/kg, and the cycle life can reach more than 1000 times; Its second product iterates the negative electrode technology, using "electrolysis + lithium metal negative electrode +NCM811", the energy density can reach 440Wh/kg; The third product is based on the second product to develop the next generation of positive electrode materials, using "electrolyte + lithium metal negative + next generation positive electrode", the energy density can be further increased to 560Wh/kg.

Unlocking the Potential of Solid-State Batteries: A Revolutionary Energy Storage SolutionHigh energy density of more than 300Wh/kg or even 500Wh/kg, solid-state batteries can be described as "hanging" traditional liquid lithium batteries. "There is no increase in energy density from a liquid to a solid electrolyte." Industry insiders pointed out that the solid-state battery system provides higher safety redundancy and better phase for new positive and negative materials, and higher capacity negative or positive materials can be used.As a silicon-based negative electrode material with a theoretical specific capacity of more than 10 times that of graphite, it has now almost become the standard for solid/semi-solid batteries, and is paired with high energy positive electrode materials, making the battery energy density easily break through 300Wh/kg.Maximizing Performance with Silicon Anode Material: The Next Generation of BatteriesIn terms of performance, silicon is indeed an ideal anode material for the next generation. Silicon has an ultra-high theoretical specific capacity of up to 4200mAh/g, more than 10 times higher than the capacity of traditional graphite materials (372mAh/g). Moreover, the silicon base has a lower delithium potential, and because its voltage platform is higher than that of graphite, it is more difficult to cause surface lithium ion precipitation during charging, and the comprehensive safety performance of the battery is better.Overcoming the Bottleneck: Reducing Silicon Expansion for Improved Battery PerformanceIt is worth noting that for a long time, silicon-based materials have not achieved large-scale mass production because of the shortcomings of cyclic expansion. "It's a bottleneck. Because once the silicon expands during the charging and discharging process, it will inevitably lead to the damage of the material structure, and the rapid decay of the cycle will cause the battery to be unable to use." Industry insiders point out. Therefore, a technical core of silicon-based materials is how to make silicon smaller, so as to reduce its expansion during the process of lithium removal.

Background :As a material binder (commonly mixed with something called a binder) for making electrodes for lithium-ion and lithium-polymer batteries. The reason adhesives are used as electrode materials in lithium-ion batteries is to bond the slurry to the fluid collector foil and to prevent the electrode material from peeling off the fluid collector foil after drying (to increase peel strength).In addition, there is now a strong trend towards the use of substances that can reduce environmental impact, from so-called solvent-based electrodes using organic solvents NMP and PVDF as binders, to the trend of using water and binders as solvents for pastes using water-based electrodes using certain rubber-based or acrylic based materials. Here, I will explain what is SBR (styrene butadiene rubber), which is the representative water-based adhesive.The Definination of SBR:SBR is an abbreviation of the scientific name styrene butadiene rubber. SBR is a versatile rubber that accounts for about 80% of synthetic rubber production. The physical properties of SBR include the following, but basically it is a material with an excellent balance between strength, chemical resistance, etc. In many cases, it is used as a water-based adhesive for lithium-ion batteries.The general physical characteristics of SBR:SBR Features (Advantages)(1) High strength, elasticity, wear resistance, heat resistance, acid resistance, alkali resistance, insulation;(2) The proportion of impurities in the manufacturing process is low and the purity is high;(3) easy to vulcanize;(4) Price stability.SBR Features (Disadvantages)(1) The tolerance to gas phosphorus and other oils, benzene, toluene and other organic solvents, organic acids is relatively low. However, when used as an electrode for lithium-ion batteries, the material is strongly compressed after formation, so it is unlikely to react with organic solvents as electrolytes, so there is no particular problem. The specific use of SBR in lithium-ion batteriesSBR (Styrene-butadiene rubber) is used as a representative water-based adhesive in lithium-ion batteries. In water-based electrodes, when SBR is used as a binder, CMC (carboxymethyl cellulose) is basically used as a thickener. Taking the positive electrode as an example, the composition of the water electrode is mainly active substances: conductive additives: binders: thickeners (CMC), and the solid content ratio is 80~90% : 0~10% : 0~10% : 0~ 0~ usually accounts for about 10%.If it is a negative electrode, the composition of the water-based electrode is mainly the active substance: binder: thickener (CMC), and the solid content ratio is 80~90% : 0~10% : 0~10%. The basic manufacturing process for electrodes using water-based adhesives (SBR) is as follows:Solvent-based systems primarily use PVdF as a binder and NMP as a viscosity regulator (diluent), while water-based systems, as the name suggests, use water and CMC (carboxylic acid) as a viscosity regulator. Each battery manufacturer optimizes the electrode material composition, mixing procedure, mixing time, coating conditions, etc., but in most cases the process flow is basically as follows.

Enhancing Battery Performance through Ethanol-Induced Phase Inversion StrategyRecently, The team of Prof. Fokko M. Mulder of Delft University of Technology in the Netherlands published A paper entitled "A phase inversion strategy for low-tortuosity and Low-Tortuosity" in Cell Reports Physical Science ultrahigh-mass-loading nickel-rich layered oxide electrodes ". This paper reports a strategy of phase conversion induced by ethanol, which is an effective method for the preparation of high quality supported nickel-rich layered oxide (LiNi0.8Mn0.1Co0.1O2 [NMC811]) electrodes. The ethanol-induced phase change electrode is obviously superior to the conventional NMC cells at 1 C discharge. The non-solvent-induced binder structure improves pore connectivity, reduces the bending coefficient, and rapid solvent removal reduces adhesive migration during drying, enabling ultra-high active mass loads of up to 60 mg/cm2 (12 mAh/cm2). In addition, the high compatibility of this phase conversion process with the roll-to-roll coating devices currently used in industry makes it highly industrial feasible, which has important implications for the development of high energy density batteries. EPI Technology: A Game-Changing Strategy for High-Performance ElectrodesThis work develops a new strategy based on EPI technology for manufacturing high-performance nickel-rich layered oxide electrodes with high-quality loads. Using EPI technology, NMCC811 electrodes with a high active mass load (35 mg/cm2) were designed to perform better than conventional NMC811 electrodes during fast charging, with an improvement of 50% at 0.5C and 120% at 1C. Unlike conventional electrodes, EPI electrodes can be made into ultra-thick electrodes (60 mg/cm2, 12 mAh/cm2) without delamination or cracking problems. The EPI electrode showed a higher weight capacity and a similar capacity retention rate over long cycles than conventional electrodes, indicating that the processing does not affect the positive active material and can significantly improve magnification performance. Most importantly, the introduction of EPI technology only requires the addition of a phase conversion treatment step to the conventional battery manufacturing process, in line with existing industrial production lines, which provides an important technical basis for the preparation of future batteries with high energy and power density.

There are three main routes for solid-state battery electrolyte materials, which are polymers, oxides and sulfides. Each of the three products has advantages and disadvantages, and different companies choose different paths, but at present, no one can fully achieve the balance of technology and mass production costs.1: European and American companies mainly use polymer routesThe advantage of the polymer is that its conductivity is similar to that of a liquid electrolyte. However, the shortcomings are also obvious, the mechanical strength is insufficient, and there is still the problem of lithium dendrite piercing. In other words, the internal conduction problem of polymer solid-state batteries still exists, and safety cannot be effectively guaranteed. At present, European and American companies mainly use the polymer route.2: Japanese and Korean enterprises adopt the sulfide routeThe sulfide has high conductivity, close to the liquid electrolyte, and the interface is relatively stable, with both strength and processing properties, and high interface compatibility. However, the air stability of sulfur is poor, and when it is exposed to the air, it is easy to react with water and oxygen in the air to produce hydrogen sulfide toxic gas. Therefore, the synthesis, storage, transportation and post-treatment of sulphide electrolytes need to rely heavily on inert gases or drying chambers. As a result, the preparation process is extremely complicated and the cost is high. In addition, the sulfide electrolyte itself is also expensive. At present, mainly Japanese and South Korean companies adopt the sulfide route.3: Chinese enterprises are more likely to adopt the oxide routeIts advantages are high density, high mechanical strength, and it is not easy to puncture, so it can effectively improve safety. However, it is also its high density that causes the internal impedance to be too large, resulting in poor conductivity. "Its internal impedance is very large, and even affects the actual performance of internal charging and discharging, which is not as good as liquid products."In all the current solid electrolyte technology routes, the polymer is not so prominent, short board, while the industry maturity is higher.Long board, due to the high flexibility of polymer electrolyte material, easy processing, the price is only slightly higher than the liquid; The production is compatible with the existing battery process, the equipment cost is not different, and the mass production cost is low. In terms of performance, the polymer material has good contact with the positive and negative electrode material interface, which is conducive to the extension of battery cycle life.

Safety and high energy density, solid state battery advantagesThe rapid development of the new energy vehicle industry, but frequent safety accidents, energy density bottleneck, is the core problem to be solved. Solid state batteries replace flammable electrolyte with solid state electrolyte, which can realize the intrinsic safety of the battery, while compatible with better performance of positive and negative electrode materials, which can greatly improve the energy density of lithium batteries, with high safety and high energy density, and become the inevitable choice to comprehensively improve the performance of lithium batteries.Under the guidance of many forces, the industrialization process has acceleratedAll-solid-state batteries have comprehensive performance, but there are problems such as high cost and poor solid-solid interface conductivity, which limit their large-scale commercial application. Semi-solid state battery as a transition technology, has been in the NiO, Dongfeng Lantu, SAIC Zhiji and other brands on the batch. In addition, the rapid development of the eVTOL industry, its battery energy density, safety, rate performance and other higher requirements, the existing battery technology can not meet its requirements, solid state batteries are expected to meet the batch application in eVTOL, industrial development is expected to benefit. Major countries in the world have actively laid out the solid-state battery industry, and major overseas companies such as Solid Power, Toyota, Samsung SDI, etc., have chosen the sulfide route as the direction of solid-state battery technology, and mainly develop all-solid-state batteries. Domestic enterprises such as Weilan, Qingtao, etc., have chosen the oxide route, and first developed and produced semi-solid batteries. Under the joint promotion of car enterprises and battery factories at home and abroad, the industrialization process is expected to continue to accelerate.Material system upgrade, create new opportunities for industryThe transformation process of lithium battery technology to solid state battery will drive the upgrading of the material system, mainly including: 1) solid electrolyte: solid state battery replaces the electrolyte and diaphragm with solid electrolyte; Zirconium, lanthanum and other materials in the oxide system are expected to benefit; Under the sulfide system, germanium may welcome new opportunities; 2) Positive and negative electrode materials: the positive electrode will be more widely used in high-nickel ternary, and gradually change to lithium-rich manganese base; The negative electrode will evolve to the silicon base negative electrode and the lithium gold negative electrode. 3) Porous copper foil: Compared with traditional electrolytic copper foil, porous copper foil can improve the lithium-ion transmission efficiency of solid-state batteries, improve the cycle, further enhance the safety of solid-state batteries, and more suitable for solid-state batteries; 4) aluminum-plastic film: Soft laminated film can improve the flexibility of solid-state batteries, or the most suitable assembly method for solid-state batteries, is expected to drive the demand for aluminum-plastic film.

Slurry preparation process challenges(1) Water-based positive slurry. NMP is the only solvent for positive PVDF adhesives. NMP is toxic and carcinogenic, consumes more energy than water by evaporation, and requires solvent recovery systems in industrial applications. Therefore, it is urgent to develop the positive slurry of water system.(2) Continuously stir. Coating is a continuous process, but the traditional mixing process is an intermittent process. The continuous mixing process reduces process time and energy consumption and improves process control, resulting in a more consistent slurry.(3) Increase solid content. The solid content of the negative slurry is usually ~ 50%, and the positive NMP slurry is generally ~ 70%. If solid content can be increased while maintaining the processing properties of the coating process, material and energy costs will be reduced. The ultimate limit is the solvent-free coating process.(4) Thicker electrodes. Thick electrodes reduce the amount of metal foil and diaphragm in the battery and increase the energy density. However, due to the longer electron and ion conduction pathways in the electrodes, thick electrodes will reduce the magnification performance of the battery. In addition, it is also difficult to produce thick coatings with good mechanical properties in industry.(5) Synchronous double-sided coating. The coating drying oven is usually horizontal, and the wet coating is generally on the upper part of the metal foil. Current double-sided coating is done by drying one side before recoating the other side, which adds additional manufacturing time and passes the A-side coating through the oven twice. At the same time, double-sided coating requires a drying oven with a pole sheet floating.(6) porosity gradient electrode. The two-layer electrode model calculated an optimal porosity of 10% near the fluid collector and 50% on the coated surface instead of a uniform 30%. In production, this requires a continuous double-layer coating or formwork technique.Rheological challenge of electrode pasteThe use of rheology as a predictive tool in the manufacturing process has three main challenges that need to be addressed:(1) The differences between laboratory scale and industrial processes can be large, and the relationship between these amplification process changes and key properties (such as rheology) is unclear, it is necessary to use industry-relevant formulations, weight percentages and equipment (mixers and coators) in the study, and to characterize the rheology of the electrode paste. Rheology can detect subtle but important changes within a slurry batch during mixing and coating. For example, poor mixing can result in an uneven distribution of free carbon black in the slurry, resulting in changes in viscosity and viscoelasticity throughout the batch.(2) Reveal the interactions between the components in the electrode slurry, what is their relationship to the formulation and mixing process? How do they affect flow characteristics?(3) Quantitative understanding of optimal rheology in manufacturing and process control. Hydrodynamic modeling is a means of understanding coating flows and potential problems, such as unstable flows, stock buildup in dead zones, and defects such as pinholes, blisters, cracking, and delamination.Electrode coating challenges(1) Many of the limitations of current coating techniques are related to the use of liquid pastes. Usually in these slurries, 30%-60% of the mass is solvent, which needs to be removed from the electrode and leaves too much porosity in the dry electrode layer, so it needs to be calendered to be dense. In addition, higher water surface tension results in higher capillary forces during drying and poor collector wetting, resulting in cracking and delamination of the coating, especially for thick (>100 μm) electrodes. Dry or low-solvent electrode processes can avoid these problems, but also have their own challenges: ensuring adequate mixing of the dry powder, preparation of the dry powder mixture into a film of a specified width and thickness, and ensuring that the electrode film can adhere to the fluid collector.(2) The electrode of the wet process has a spatially-uniform distribution of components and pore structure, and the optimal composition, thickness and porosity of the current electrode are obtained through repeated tests under the constraints of the slurry coating process. Relaxing these restrictions and providing greater flexibility could enable the design of higher performance electrodes.(3) Optimization and control of electrode structure parameters. Electrode thickness is one of the key structural parameters that affect the energy density of lithium-ion batteries. Thicker slurry coated electrodes lead to slow transmission of lithium ions due to longer transmission path. Thick electrodes are also prone to cracking and delamination. Therefore, to increase electrode thickness, there are many challenges to overcome. Porosity is another key parameter that can have both positive and negative effects on lithium-ion battery performance. Currently, electrode porosity is mainly controlled through the calendering process, and thicker electrodes require additional processes to control the necessary porosity to ensure good performance. Tortuosity, that is, the ratio of the actual length of the lithium ion transport path to the linear distance between the starting point and the end point, is a structural parameter describing the difficulty of lithium ion transport within the electrode. For electrodes with higher mass loads, the challenge is the need to develop new electrode structure strategies to achieve low electrode tortuosity by controlling the shape, size, and distribution of the electrode holes without sacrificing other electrode properties.(4) The main challenge of the dry electrode process is to reduce the content of inactive materials to a level comparable to that of wet coating, while some processes involve degreasing steps and high temperature sintering, making the process more expensive and potentially difficult to scale up.Electrode drying process challenges(1) Create an efficient drying model that correlates dynamic measurements of drying conditions with the final characteristics of the electrode to enable a more controlled drying process. Examples include computational fluid dynamics models at the continuous level, convection heat and mass transfer models at the air-porous material interface, theoretical models of drying of two-component colloidal suspensions, and one-dimensional models of particle coatings including Brownian diffusion, sedimentation and evaporation.(2) The drying kinetics of the wet electrode film is particularly complex, and in order to better control the electrode structure and its corresponding electron and ion transport characteristics, we need to understand the process of electrode structure formation. Drying is the basis for forming the electrode structure, so it is necessary to develop advanced metrological tools to understand the physical processes that occur during drying, to measure and analyze the effect of solvent evaporation on defects, such as crack formation. The adhesive distribution can be characterized by energy spectrum EDX, Raman spectrum, Fourier transform infrared spectroscopy (FTIR) and multispot diffusion wave spectroscopy (MSDWS). Solvent evaporation can be measured by thermogravimetric analysis and quartz crystal microbalances (QCM). The surface temperature and drying stress during solvent evaporation can be measured by infrared (IR) thermography. Active materials can be characterized by SEM, X-ray CT, and fluorescent-based imaging/microscopy.Electrode calender process challengesDuring the calendering process, the particle structure of the active material (AM) and the carbon colloidal phase (CBD) are compressed and rearranged, and the intergranular porosity is reduced. The compaction of the pore structure of the electrode particles will in turn affect the electron ion transport performance and the battery performance.(1) In the manufacturing process, the mechanical properties of the electrode are affected by the material composition, process parameters (such as roller temperature, speed) and electrode thickness. Due to the complex effects of these characteristics and parameters on the electrode rolling deformation, it is necessary to characterize the mechanical properties of the electrode, such as hardness, elastic deformation, and adhesion between the electrode and the collector. In order to obtain further understanding of the mechanism, a large number of systematic studies between parameters and material properties are needed, such as numerical simulation and experimental studies to obtain the dynamic mechanical response of calender to porous carbon gel phase.(2) Capturing particle plastic deformation and fracture at high calendering levels is challenging, and a deeper understanding of interparticle forces is still needed to establish nonlinear constitutive behavior and study microstructure evolution within the electrode in high fidelity.