Generally, thermal runaway of lithium batteries is caused by three types of abuse, namely mechanical abuse, electrical abuse, and thermal abuse.Among them, mechanical abuse refers to the battery being subjected to external forces such as collision, extrusion, and puncture;Electrical abuse refers to the battery being subjected to internal and external short circuits, overcharge, and discharge;Thermal abuse refers to the battery being subjected to external heating.In fact, these three types of abuse are not completely independent, but are chain-related. The relationship between the three types of abuse is shown in the figure.As can be seen from the figure, mechanical abuse will first lead to electrical abuse, and then electrical abuse will lead to thermal abuse, and finally trigger thermal runaway.The reason why mechanical abuse leads to electrical abuse is that external force causes the internal diaphragm of the lithium battery to rupture, causing the positive electrode to connect with the negative electrode, thereby causing an internal short circuit, which is a case of electrical abuse.The reason why electrical abuse leads to thermal abuse is that once a short circuit occurs inside the lithium battery, a large amount of heat will be released, and chemical reactions under higher temperature conditions will be triggered, which will further release heat, which is equivalent to the external heat source constantly heating the battery, that is, thermal abuse.Once the heat inside the battery accumulates to a certain extent, thermal runaway will break out.Bosa EnergyBosa Energy with 150GWH capacity and over 400,000 electric bus/utility vehicle application experience we are listing first 5 in China power battery industry. We cooperate with Yutong/Geely/Damiler etc.We are also offering Container ESS systems and delivered 6GWh in 2024(=75,000 Model3 with 80kWh battery). In local market, we are offering OEM service for Changan, CALB, National grid, Ping Gao Electric , Xuji electronics, Ruineng electronics, they are our main Container ESS suppliers in China Market.We are the most professional supplier of marine lithium batteries in China, and our export volume of marine batteries consistently ranks among the top three in China; We are also the top 1 exporter of lithium battery modules in China, specializing in providing various lithium battery module solutions.For excellent quality and performance our products are popular in more than 30 countries in the world. We also have established warehouse in Germany and Netherlands to provide safety stock timely delivery for our customers.l Customized and Flexiblel High Delivery capacityl Wide Applicationsl Rich experience on Lithium battery pack

1. Definition and calculation logic of surface densitySurface density is a core parameter in the design of lithium-ion battery pole piece, which is defined as the mass of active material per unit surface area of the electrode (unit: mg/cm²).The calculation formula is: Surface density = compaction density (g/cm³) * pole piece thickness (μm)/1000The surface density directly determines the content of active materials per unit area of the pole piece and is a regulatory lever for energy density (battery life) and rate performance (charging speed).2. The impact of surface density on battery life: the "amplifier" of energy densityHigh surface density improves battery life. The higher the surface density, the more active materials the positive electrode can accommodate per unit surface area, and the energy density increases accordingly.The cost of battery life: internal resistance and thermal runaway risk. High surface density leads to increased thickness of the pole piece, longer lithium ion diffusion path, increased internal resistance and increased heat generation, which may cause thermal runaway.3. The impact of surface density on charging speed: the "double-edged sword" of fast charging performanceLow surface density optimizes fast charging capability. When the surface density decreases, the pole piece becomes thinner, the lithium ion diffusion path is shortened, the polarization effect is weakened, and the internal resistance is reduced, which is more suitable for fast charging scenarios.Hidden dangers of extreme low surface density: Too low surface density will increase the difficulty of coating process, reduce mechanical strength (easy to break), and require more pole piece layers to be stacked, which will increase costs and safety risks.Theoretically, the smaller the surface density, the more conducive it is to improving rate performance. However, the surface density design also has a lower limit. In addition, the battery has not only rate requirements, but also capacity requirements. Simply reducing the surface density will inevitably increase the number of layers of the pole piece, and the increase in the number of layers also increases the risk.The balance rule of R&D engineers: How to design the optimal surface density?Application scenario priority, material and process coordination, dynamic test verificationBosa EnergyBosa Energy with 150GWH capacity and over 400,000 electric bus/utility vehicle application experience we are listing first 5 in China power battery industry. We cooperate with Yutong/Geely/Damiler etc.We are also offering Container ESS systems and delivered 6GWh in 2024(=75,000 Model3 with 80kWh battery). In local market, we are offering OEM service for Changan, CALB, National grid, Ping Gao Electric , Xuji electronics, Ruineng electronics, they are our main Container ESS suppliers in China Market.We are the most professional supplier of marine lithium batteries in China, and our export volume of marine batteries consistently ranks among the top three in China; We are also the top 1 exporter of lithium battery modules in China, specializing in providing various lithium battery module solutions.For excellent quality and performance our products are popular in more than 30 countries in the world. We also have established warehouse in Germany and Netherlands to provide safety stock timely delivery for our customers.l Customized and Flexiblel High Delivery capacityl Wide Applicationsl Rich experience on Lithium battery pack

On April 19, the world's first humanoid robot half marathon was held in Beijing. On the 21.0975-kilometer track, 20 robot teams from universities, research institutes, and enterprises participated in the first "human-robot co-run".The 180cm tall and 52kg"Tiangong Robot Ultra" won the championship by running at a constant speed of 7 to 8 kilometers in 2 hours and 40 minutes.Batteries are not only the power source of robots, but also directly affect their endurance, performance and application scenarios.This competition not only ignited the public's enthusiasm for smart manufacturing, but also made the application of lithium battery technology in the field of robotics a focus.Core application requirements of batteries in the robotics field①High energy density and lightweightHigh energy density allows the robot to have a longer battery life and continue to drive without slowing down.Lightweight structure can match the structural limitations of humanoid robots or service robots and reduce load②High safety design and environmental adaptabilityStable output, through overcharge and overdischarge protection, thermal runaway protection (such as high temperature resistance of lithium iron phosphate battery), to avoid power outage or overheating during operation.③High power output and fast charging or quick replacement capabilitiesThe battery of "Tiangong Robot Ultra" was replaced 3 times during the whole process, and the robot was not replaced. The first battery replacement took 1 minute and 50 seconds to complete.④Long cycle life and intelligent managementMarathon is not only a race, but also a microcosm of future intelligent manufacturing applications. From automatic food delivery robots, intelligent logistics vehicles, to inspection unmanned vehicles, special service robots... they all rely on the support of high-performance lithium batteries.Bosa EnergyBosa Energy with 150GWH capacity and over 400,000 electric bus/utility vehicle application experience we are listing first 5 in China power battery industry. We cooperate with Yutong/Geely/Damiler etc.We are also offering Container ESS systems and delivered 6GWh in 2024(=75,000 Model3 with 80kWh battery). In local market, we are offering OEM service for Changan, CALB, National grid, Ping Gao Electric , Xuji electronics, Ruineng electronics, they are our main Container ESS suppliers in China Market.We are the most professional supplier of marine lithium batteries in China, and our export volume of marine batteries consistently ranks among the top three in China; We are also the top 1 exporter of lithium battery modules in China, specializing in providing various lithium battery module solutions.For excellent quality and performance our products are popular in more than 30 countries in the world. We also have established warehouse in Germany and Netherlands to provide safety stock timely delivery for our customers.l Customized and Flexiblel High Delivery capacityl Wide Applicationsl Rich experience on Lithium battery pack

An important factor affecting the performance of lithium batteries is internal resistance. As a key indicator of lithium battery performance, internal resistance has a profound impact on the battery's discharge performance, charging performance, self-discharge rate, temperature characteristics and cycle life.The influence of lithium battery internal resistance on battery performance1. Lithium battery dischargeIn terms of discharge performance, the greater the internal resistance of the lithium battery, the more voltage is lost during the discharge process, resulting in a decrease in output voltage. In addition, a larger internal resistance will also limit the size of the output current. The size of the lithium battery internal resistance directly affects the discharge capacity of the battery. In scenarios where high power output is required, lithium batteries with larger internal resistance may not be able to meet the demand, resulting in performance degradation.2. Lithium battery chargingIn terms of charging performance, internal resistance also plays a key role. When the internal resistance is large, the charging current will be limited, resulting in a slower charging speed and affecting the charging efficiency of the battery. Especially with the widespread application of fast charging technology, reducing internal resistance has become the key to improving charging performance.3. Internal resistance also affects the self-discharge rate of lithium batteries. Self-discharge refers to the loss of power caused by internal chemical reactions when the battery is not connected to an external circuit. The larger the internal resistance, the higher the self-discharge rate, which will also cause rapid power loss when the battery is not in use.4. The influence of internal resistance on the temperature characteristics of lithium batteriesLithium batteries generate heat when working, and the larger the internal resistance, the more heat is generated. This may not only cause the battery temperature to rise, but also affect the stability and safety of the battery.Optimization measures to reduce the internal resistance of lithium batteries and improve battery performance1. Optimize battery materials: Select positive and negative electrode materials and electrolytes with high conductivity and low polarization effect, which can effectively reduce the internal resistance of the battery.2. Improve battery structure: By optimizing the battery pole design, diaphragm thickness and electrolyte distribution, the internal resistance and polarization effect of the battery can be reduced, thereby reducing the internal resistance.3. Apply BMS management to reduce internal resistance: BMS can accurately control and monitor the battery to avoid problems such as overcharging and discharging and overheating of the battery, so as to keep the internal resistance of the battery at a low level.4. Reduce the internal resistance of lithium batteries by adopting advanced thermal management technology: By adopting advanced thermal management technology to reduce the internal resistance of lithium batteries, such as liquid cooling, air cooling, etc., the operating temperature of the battery can be effectively controlled to reduce the increase in internal resistance caused by temperature increase.Bosa EnergyBosa Energy with 150GWH capacity and over 400,000 electric bus/utility vehicle application experience we are listing first 5 in China power battery industry. We cooperate with Yutong/Geely/Damiler etc.We are also offering Container ESS systems and delivered 6GWh in 2024(=75,000 Model3 with 80kWh battery). In local market, we are offering OEM service for Changan, CALB, National grid, Ping Gao Electric , Xuji electronics, Ruineng electronics, they are our main Container ESS suppliers in China Market.We are the most professional supplier of marine lithium batteries in China, and our export volume of marine batteries consistently ranks among the top three in China; We are also the top 1 exporter of lithium battery modules in China, specializing in providing various lithium battery module solutions.For excellent quality and performance our products are popular in more than 30 countries in the world. We also have established warehouse in Germany and Netherlands to provide safety stock timely delivery for our customers.l Customized and Flexiblel High Delivery capacityl Wide Applicationsl Rich experience on Lithium battery pack

According to the retail sales data released by relevant institutions, the total sales volume of China's auto market in 2024 will reach 22.892 million units, and the total sales volume of new energy vehicles will reach 10.749 million units, a year-on-year increase of 47.5%. Among them, the sales volume of pure electric models will reach 6.281 million units, accounting for 58.5% of the market.Bosa EnergyBosa Energy with 150GWH capacity and over 400,000 electric bus/utility vehicle application experience we are listing first 5 in China power battery industry. We cooperate with Yutong/Geely/Damiler etc.We are also offering Container ESS systems and delivered 6GWh in 2024(=75,000 Model3 with 80kWh battery). In local market, we are offering OEM service for Changan, CALB, National grid, Ping Gao Electric , Xuji electronics, Ruineng electronics, they are our main Container ESS suppliers in China Market.We are the most professional supplier of marine lithium batteries in China, and our export volume of marine batteries consistently ranks among the top three in China; We are also the top 1 exporter of lithium battery modules in China, specializing in providing various lithium battery module solutions.For excellent quality and performance our products are popular in more than 30 countries in the world. We also have established warehouse in Germany and Netherlands to provide safety stock timely delivery for our customers.l Customized and Flexiblel High Delivery capacityl Wide Applicationsl Rich experience on Lithium battery pack

Overview of lithium battery pack and frameLithium battery pack mainly consists of a load frame (lower frame, upper frame), lithium battery, high-voltage connection components (such as high-voltage connectors), low-voltage connection components (such as low-voltage connectors), etc.①- Upper frame; ②- Lower frame; ③- Lithium battery pack; ④- High voltage components; ⑤- Low voltage components (included)The lithium battery frame not only serves as a carrier for various components, but also acts as a "bridge" connecting the entire vehicle. The lithium battery is assembled on the vehicle through the lithium battery frame mounting structure.NIOIn order to facilitate installation and maintenance, the load-bearing frame is generally divided into an upper frame and a lower frame. The lower frame mainly carries components and bears more weight of the battery system; the upper frame generally plays a protective role and has a smaller load-bearing requirement;Lower frame designAs the main load-bearing component of the battery system, the lower frame is relatively more complex to design. There are many considerations in the design process, mainly mechanical strength, sealing design, corrosion resistance, lightweight, etc. At present, the lower frame processes used in battery systems include sheet metal processing, cold stamping, extrusion molding, die casting, etc.(1) Design based on vehicle envelope and lithium battery processDifferent lithium battery types and processes are suitable for different frame design schemes.Battery arrangement is carried out according to the selected battery type and its process. The arrangement scheme of the battery in the frame is called grouping technology. The pros and cons of the grouping scheme and whether the frame design meets the standards are important indicators. The grouping efficiency is the proportion of effective weight and effective space of the battery. The higher the effective proportion, the higher the grouping efficiency.Battery frame design needs to consider the arrangement, fixing and thermal management of the battery in the frame.prismatic batteries are mainly arranged vertically along the heightprismatic batteries are arranged vertically along the heightThere are two main ways of fixing: bracket fixing, which is the traditional module solution, and bracket-free fixing, such as the CTP (Cell to Pack) solution, in which the battery cell is directly fixed to the frame with glue.(2) Design based on power and energy densityBattery layout is carried out according to the power and voltage platform required by the vehicle. In this process, the size decomposition from envelope to battery can be preliminarily completed. According to the battery type and the decomposed battery size, the battery energy density, volume density, etc. can be estimated, and the selection and layout plan can be checked again to confirm whether this layout plan meets the current battery technology level of the industry.Different battery systems have different battery voltage platforms, and the number of batteries required to be grouped in the system will also be different.Upper frame designThe upper frame mainly cooperates with the lower frame to form a closed space to protect the internal components of the frame. The selection of the upper frame material mainly considers environmental adaptability, such as high temperature resistance and corrosion resistance; and has a certain strength to meet the structural strength requirements of the battery system. Currently, sheet metal materials and composite materials are mainly used.With the promotion and application of the CTC solution, the upper frame will also be integrated into the chassis of the vehicle.Other auxiliary designs(1) Sealing designThe connection between the upper and lower frames needs to be sealed to achieve waterproof and dustproof functions.(2) Air pressure balance designThere is a pressure difference between the inside and outside of the sealed frame, which is affected by temperature, altitude, etc. Excessive pressure difference will cause additional force on the frame, affect the frame structure, and even cause the frame to explode. Devices such as air pressure balance valves or breathable valves are often used to balance the internal and external pressure differences.Another function of the air pressure balance design is to provide timely air release.(3) Thermal management design(4) Safety designThe frame design also needs to consider corresponding safety protection designs, such as electric shock protection design, extrusion protection, collision protection, thermal runaway protection design, etc.(5) High and low pressure connection designBosa EnergyBosa Energy with 150GWH capacity and over 400,000 electric bus/utility vehicle application experience we are listing first 5 in China power battery industry. We cooperate with Yutong/Geely/Damiler etc.We are also offering Container ESS systems and delivered 6GWh in 2024(=75,000 Model3 with 80kWh battery). In local market, we are offering OEM service for Changan, CALB, National grid, Ping Gao Electric , Xuji electronics, Ruineng electronics, they are our main Container ESS suppliers in China Market.We are the most professional supplier of marine lithium batteries in China, and our export volume of marine batteries consistently ranks among the top three in China; We are also the top 1 exporter of lithium battery modules in China, specializing in providing various lithium battery module solutions.For excellent quality and performance our products are popular in more than 30 countries in the world. We also have established warehouse in Germany and Netherlands to provide safety stock timely delivery for our customers.l Customized and Flexiblel High Delivery capacityl Wide Applicationsl Rich experience on Lithium battery pack