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.

Due to its advantages of high energy density, long cycle life, low self-discharge rate, and no memory effect, lithium-ion batteries stand out from many energy storage technologies and become the most important part of the electrochemical energy storage field at present. In recent years, the application scenarios of lithium-ion batteries have expanded rapidly, from portable electronic products to electric vehicles, home energy storage, industrial energy storage, etc., lithium-ion batteries have penetrated into all aspects of society, which also puts higher requirements on the safety and energy density of lithium-ion batteries.Traditional lithium-ion batteries mainly rely on organic liquid electrolyte to conduct lithium ions, and the flammable and volatile characteristics of the electrolyte lead to thermal runaway, fire, explosion and other safety risks in the case of overheating, short circuit, overcharge, and mechanical damage. New energy vehicle safety accidents occur from time to time, and ensuring the safe operation of new energy vehicles is the primary task of the current development of the industry. In recent years, through the innovation of battery system structure, the safety of power battery operation has been improved to a certain extent. Facing the future, the development of battery structure innovation to material system innovation is an inevitable trend of power batteries.Therefore, the development of high safety and high energy density energy storage technology to make up for the shortage of liquid lithium-ion batteries is an important development direction of lithium-ion batteries in the future.The use of solid electrolytes to replace liquid electrolytes and the development of all-solid-state lithium batteries can solve the energy density bottleneck and safety risks faced by the current liquid ion batteries, and become the most potential next-generation lithium-ion battery follow-up technology. As shown in Figure 1, the structure and working principle of the all-solid lithium battery is similar to that of the liquid lithium ion battery, but the solid electrolyte has high thermal stability and chemical stability, and will not leak, burn or explode, thereby reducing the risk of thermal runaway and improving the intrinsic safety of the battery. At the same time, the solid electrolyte has a high Young's modulus, which can effectively inhibit the growth of lithium dendrites, and is expected to realize the application of metal lithium anode, which greatly improves the energy density of the battery. In addition, the packaging of all-solid-state batteries is easier. The use of bipolar stacking technology in solid-state batteries can reduce the use of inactive materials such as pole ears and leads, and the battery module does not require a cooling system, which is expected to further improve the volume and mass energy density of the system.

As an important instrument for the measurement of adiabatic thermal runaway of batteries, the core technical index of the battery adiabatic calorimeter is the self-exothermic detection sensitivity of the sample, that is, the ability to identify the weak exothermic heat of the sample. This index directly determines the measurement accuracy of the instrument for the characteristic temperature points such as the initial temperature of the battery self-exothermic heat. In order to achieve high detection sensitivity, the instrument is required to have ideal structural design, accurate temperature measurement technology and efficient temperature control algorithm, so as to achieve excellent adiabatic performance.At present, there is a lack of measurement and calibration specifications for the whole battery adiabatic calorimeter in the industry, so there is no unified, scientific and reasonable method to verify the core indicators of the instrument, which is not conducive to objectively evaluating the performance of the instrument and regulating the instrument standards, and the data measured by the instrument with poor adiabatic performance will directly affect the relevant enterprises to carry out the safety design of the battery system, and have a negative impact on the development of the lithium battery related industries.Some manufacturers and users use lithium batteries with empirical data as standard samples for instrument evaluation. There are some problems in this method: (1) The same batch of batteries may have slight differences in internal structure and materials, and the consistency of thermal runaway experimental data cannot be guaranteed, which will introduce additional uncertainty; (2) The thermal runaway process of some lithium batteries is severe, causing obvious pollution and even damage to instruments and equipment, and at the same time, high requirements for the test site.

Carbon nanotubes (CNTS) are perfect 1D cylinders composed of one (single-walled carbon nanotube, SWCNT) or multiple graphene sheets (multi-walled carbon nanotube, MWCNT) rolled up and have become the focus of research due to their unique geometry and excellent properties. Both experimental and theoretical analyses show that single-walled carbon nanotubes (SWCNT) and multi-walled carbon nanotubes (MWCNT) have high mechanical strength, high aspect ratio (> 1000), high thermal conductivity, high melting point and low density (1.2-2.6 g/cc). In addition, CNT has a larger surface area (approximately 1000 m²/g), showing excellent hydrogen storage capacity, significant biological properties, and higher corrosion resistance. CNTS also have unique electrical conductivity, and depending on their structure (diameter and helicity), they can exhibit the electronic properties of metals or semiconductors. It is precisely because of its excellent physical and chemical properties that carbon nanotubes have initially blossomed in the field of new materials, gradually realizing industrialization, and are also widely used in the lithium battery industry, attracting more and more attention from the industry.Domestic carbon nanotubes as a conductive agent used in power batteries, its market with the rapid growth of the power battery industry, the scale has reached billions of yuan per year, there are a number of domestic and foreign companies and listed companies have been involved in the field of carbon nanotubes conductive, such as Dow Technology, German nano, Cabot and other companies. With the expansion of the application scale of new technologies such as high-nickel positive lithium batteries, silicon-based negative batteries and solid-state batteries, the market for carbon nanotubes will also grow explosively, and it will become an annual market of 10 billion in the field of lithium batteries alone.In addition to excellent electrical conductivity, carbon nanotubes also have a huge potential market for development such as ultra-high mechanical and thermal properties. The 1996 Nobel Prize winner in Chemistry, the Honourable Richard E. Smalley (the discoverer of fullerenes), once said: "Carbon nanotubes are the strongest, toughest and hardest molecules that can be made, and are the best molecular conductors of heat and electricity." It sounds like this is the good prediction and desire of scientists, but this is the original intention of Juyuan Material Technology (Zunyi) Co., Ltd. to intervene in the carbon nanotube industry, and it is also the goal of industrialization. The application of lithium battery conductive agent is only the "tip of the iceberg" of the industrialization of carbon nanotubes, and it is the first step for capital and traditional chemical new material enterprises to understand carbon nanotubes. Carbon nanotubes in the touch screen, transistors, biomedical, solar photovoltaic cells, tires, fuel cells, drug delivery, hydrogen storage, polymer materials, capacitors, composite materials and other fields will have a broader market, will continue to break through more than 10 billion of the market, become a 100 billion market industry.The huge carbon nanotube application market requires sufficient carbon nanotube production capacity to support and a sustainable supply of low-cost high-quality carbon nanotubes in order to open a huge downstream potential application market. The early tonnage production of carbon nanotubes was achieved by fixed bed/moving bed equipment, and the continuous addition of catalysts and hydrocarbon raw materials and the continuous output of carbon nanotube products in a horizontally placed tube furnace through a sophisticated device can realize the production of the first generation of carbon nanotube plants with tons to tens of tons per year in a single device. Up to now, there is still some market space for some special types of carbon nanotubes, or some special raw materials for carbon nanotube production, using fixed bed/moving bed first-generation carbon nanotube factories.In order to achieve larger scale carbon nanotube production, the second-generation carbon nanotube factory with fluidized bed reactor solves the larger scale production problem to a certain extent, and the annual production capacity of a single reactor can reach 100 tons to hundreds of tons. At present, the large-scale production of carbon nanotubes in China, many production companies are basically based on fluidized bed reactors. With the emergence of larger production requirements, fluidized bed reactors have the following characteristics: 1. They cannot be scaled up; 2, easy carbon deposition, coking plugging reactor; 3, the boiler shutdown and cleaning of the reactor is difficult, the time-consuming period is long and other problems, which seriously restricts the expansion of the single production capacity of the fluidized bed reactor. At present, the inner diameter of the fluidized bed reactor in the industry is basically 500mm\600mm\800mm, and it is difficult to further expand.

At present, the need of high-endurance new energy vehicles forces the energy density of batteries to become higher and higher, and the use of thick electrodes with high load density active materials is one of the most practical strategies. However, their long cycle use process is accompanied by serious attenuation of electrochemical performance, power performance is not satisfied, and the capacity retention rate is getting worse and worse. So what exactly is causing the bottleneck of poor performance?Kyu-Young Park et al. explored the key processes that restrict battery decay by designing thick electrodes with different area degrees.1. Experimental designUsing NCM622: carbon black: PVDF 97:1.5:1.5 ratio and NMP mixed into pulp, after coating, drying and roller pressing, two kinds of electrodynamic half cells (2032) with different surface densities (20 and 28mg/cm-2) were prepared, and the pressure was between 2.8 and 2.9, in order to ensure better porosity. The charge and discharge cycle of the multi-channel device was carried out with the charge and discharge interval of 2.8-4.3V and the rate 1C was about 150mA/g. EIS, chemical composition and morphology were analyzed after every 20 cycles.2. Results and discussionThe following is the cross-section diagram of the electrodes of two thickths, respectively 70 and 100μm(standard electrode, thick electrode), the rest of the porosity, 1C current density and other design parameters are basically the same, and then the 1C cycle test is carried out. It is found in Figure c that although the capacity of the thick electrode of 100μm is only 40% higher than that of 70μm, but after 100 battery cycles, The thick electrode has a capacity retention rate of only 36%, while the standard electrode has a capacity retention rate of 76%. Even taking into account the volume specific capacity, the thick electrode after attenuation in Figure c is still much lower than the electrode. Interestingly, in Figure c, even in the initial cycle process, the circulation curves of the thick electrode and the standard electrode are close, and the attenuation degree is similar. Thick electrodes are getting worse.In illustrating the poor electrochemical performance observed, the authors note that thick electrodes may be subject to kinetic limitations caused by how fast or slow charge carriers migrate, which in electrochemical processes is either controlled by lithium-ion transport or by the transport of electrons that accumulate along the electrode. And, in each case, assuming that the main source of supply of electrons and lithium ions to the electrode is carried out from the electrode/collector interface and the electrode/electrolyte interface, in each case there will be a clear spatial distribution of both after the reaction.3. ConclusionBy using batteries designed with different electrode thickness, the authors verify that lithium ion diffusion is the limiting factor of charge transfer, but not electron transfer. This is also the reason why SOC at different locations is uneven, voltage drop IR increases, particle breakage and even battery diving under charge and discharge in batteries designed with thick electrodes. The electrode plate is designed according to the ion transport characteristics to avoid the phenomenon of excessive local current density, so as to improve the battery life

Lithium-ion battery (LIBs) has become one of the widely used electrochemical energy storage systems due to its high energy density, high operating voltage and no memory effect, and its commonly used graphite negative electrode is difficult to fully meet the increasing market demand due to its relatively low capacity (372 mAh g-1). Over the past few decades, researchers have proposed a variety of new anode materials, which generally exhibit the advantages of ideal potential range, higher capacity, excellent magnification performance, and long cycle life, but have the disadvantage of large initial active lithium loss (ALL). Therefore, how to eliminate ALL before full battery assembly is critical to achieving high-performance LIBs. In the course of development in recent years, new anode materials for the next generation of LIBs have gradually begun to be commercialized, so the research of pre-lithium technology, which is crucial to the elimination of ALL, has become an important research direction.Causes of loss of high initial active lithium in negative electrodeThe high initial ALL of the negative electrode occurs in the first few cycles and the coulomb efficiency is low (CE < 100%), which indicates that some Li+ remains in the negative electrode, resulting in a decrease in the amount of Li+ that can be cycled in the LIBs. When matched with the positive electrode, the reduced recyclable Li+ will inevitably lead to a reduction in the energy density of the entire battery. Figure 1 shows the typical intercalation/insertion, conversion and alloying lithium storage mechanisms of negative electrode materials, which mainly exhibit relatively low potential and much higher capacity than commercial graphite and Li4Ti5O12, but the first loop coulomb efficiency of these materials is usually less than 80%, resulting in a low coulomb efficiency mechanism. The causes of initial negative ALL can usually be divided into the formation of SEI, the loss of active material and the appearance of dead lithium.Effect of negative active lithium lossIn practical applications of LIBs, some of the recyclable Li+ is consumed to form SEI on the negative surface, resulting in a lower first turn of CE, which in turn leads to a rapid capacity decay of the battery. As shown in Figure 2, the reversible capacity of the electrode is not reduced during this process, and when additional lithium sources are added to the system, the specific capacity of the battery will be restored to the ideal situation. The introduction of additional lithium sources will offset the specific energy gain brought by the pre-embedded lithium, and the effect of higher initial ALL on the specific capacity loss of the whole battery can be elaborated through theoretical calculation and analysis, and the specific energy based on the total mass of the negative electrode, the positive electrode and the lithium source can be obtainedFigure  shows the effect of different additional lithium sources on contrast energy. The specific capacity function of R with respect to the lithium source (cls) is shown for different negative lithium sources with initial CE of 50%, 70% and 90%, respectively. It can be seen that with the increase of cls, the R factor increases, while the decrease of CE will lead to a lower R factor. It can also be seen that when cls is greater than cc, it is necessary to use lithium sources to effectively improve the energy density. The analysis of these results can add more detailed parameters for different systems.A lithium source is added to the negative electrodeInitial ALL is caused by irreversible electrochemical processes on the negative electrode, so the most direct strategy for eliminating initial ALL is to prepare the pre-embedded lithium negative electrode by electrochemical and/or chemical strategies prior to pairing with the positive electrode. The positive electrode strategies can be divided into three categories: the half cell electrochemical method (HC-EM), the short circuit electrochemical method (SC-EM) and the chemical method (CM) as shown in the figure. After the negative electrode is pre-embedded with lithium, the initial ALL problems can be solved well, and the Coulomb efficiency of the entire battery first circle can be effectively improved.

The side voltage of the lithium battery refers to the voltage of the aluminum layer between the positive ear of the soft-pack battery and the aluminum-plastic film.In theory, the aluminum layer between the positive electrode and the aluminum-plastic film is insulated, that is, their voltage should be 0In fact, during the processing of the aluminum-plastic film, the PP layer of the inner layer will be locally damaged, resulting in local conduction (including electronic channels and ion channels) between them, forming a microbattery, and thus a potential difference (voltage).The side voltage standard varies from manufacturer to manufacturer, but most of the industry is set below 1.0V, and the standard voltage is based on the dissolution potential of aluminum lithium alloy!Why control the side voltage?Because if the inner PP film of the aluminum-plastic film is damaged, the capacity will be corroded.The conditions for corrosion must have two points: 1, the electronic path, the negative electrode and the aluminum layer of the aluminum-plastic film form the electronic path; 2, the ion path, the aluminum layer of the aluminum-plastic film and the electrolyte form an ion path; Without either one, corrosion doesn't work.After the two conditions are established, the lithium ion will react with the aluminum layer of the aluminum-plastic film to generate lithium aluminum alloy; Lithium aluminum alloy is a powdery substance, resulting in aluminum-plastic film penetration; That is, we often see some black spots inside the aluminum-plastic film; These dark spots will become more and more obvious with time and the number of charges and discharges.How to choose?The current statistical detection methods are:1, test the resistance between the aluminum plastic film and the negative ear, greater than 5M ohms is relatively safe, some companies define the relatively low, look at the final PPm of bad products we endure, you can measure some data and then define their own standards can also; This resistance test is mainly to pick out the electronic path;2, test the current between the positive electrode and the aluminum film, you can use the DC source test, it is generally believed that the current is greater than 0.001mA, it is defective, need to be picked out;3. Test the voltage between the positive electrode and the aluminum film, which is generally considered to be greater than 1V for defective products.You can test 1 and 2, or 1 and 3 together.

Relationship between reaction area and internal resistance of batteryWhen considering the resistance of a metal, the resistance formula R=ρ L/S holds, where ρ of the material itself represents the difficulty of transmitting electricity. If the index is certain, it is proportional to the length of the metal. Material, which is inversely proportional to the cross-sectional area.Taking this into account in the same way as the internal resistance of the battery, the internal resistance of the battery is equivalent to R, and the resistance value per unit area determined by the composition of the electrode mixture and the electrode structure is ρ, and the length in the direction of the electrode thickness is L. If the reaction area of the electrode is imagined as S, there is no problem.A similar formula R=ρL/S applies to the internal resistance R of the battery. In other words, the internal resistance of the battery is inversely proportional to the reaction area, and the larger the reaction area, the smaller the internal resistance.The relationship between reaction area and capacity of batteryAgain, let's look at the relationship between the reaction area and the capacity of the battery. Here is how to calculate the battery capacity from the reaction area (the area of the positive and negative coated parts relative to each other) and the coating mass (battery design table). The electrode structure is certain (ρ is a constant), the length of the electrode thickness direction (determined by the coating quality and porosity) is certain (L is a constant), and the capacity of the battery is proportional to the area S.We think it is easy to imagine that the larger the reaction area, the greater the capacity (that is, the reaction electricity). (If the reaction area is made using a laminated element that is also used in a laminated battery, etc., the reaction area will be proportional to the number of electrodes (the number of relative parts) and the number of components.)That is to say, for any battery, the larger the reaction area (the larger the size), the greater the capacity. In the formula, capacitance =KS (K is a constant), when the internal resistance R=ρL/S is connected through S, S= capacitance /K=ρL/R, then the capacitance =K'/R can be. It can be seen that when the parameters other than S are fixed, the capacitance is inversely proportional to the internal resistance.Using this concept, it is possible to predict the internal resistance and output of cells of different sizes (cells with different reaction regions) when using electrodes made of the same material and the same specifications (composition, porosity, etc.).