-
25
2026-03
What factors are related to the interface resistance of lithium batteries?
The interface resistance of lithium batteries is a complex problem with multiple scales and factors, which directly affects the rate performance, low-temperature performance, cycle life, and safety of the battery.1. Definition and composition of interface resistanceInterface resistance usually refers to the resistance of two key parts inside the battery:(1) Contact resistance between the current collector and the coating: affects the efficiency of electron transfer from the current collector to the coating.(2) The electronic transmission resistance inside the coating is determined by the electronic channels formed between active material particles through a network of conductive agents and binders.2. Influencing factors and improvement methods(1) Formula design:Reasonable formula design can directly reduce the internal resistance between interfaces, including material selection and dosage. Conductive agents and binders: determine the quantity and quality of electronic transmission channels, directly affecting rate performance, low-temperature internal resistance, and heating behavior. Simply pursuing low resistivity is not always advantageous. Increasing the proportion of active substances or replacing conductive agents may improve the surface, but in reality, it may lead to uneven interface resistance, especially in silicon doped negative electrode systems where silicon has poor electron transfer and frequent expansion and contraction, requiring an appropriate conductive network to be matched.(2) Process control:Roll pressing: Proper compaction can improve particle contact and reduce resistance; However, excessive compaction may lead to particle breakage, which in turn reduces electron and ion channels. Baking: The floating of adhesive (such as SBR) can cause the area near the current collector to loosen, increasing the contact resistance. Other factors such as coating stability, carbon coating quality on the surface of the current collector, and welding tightness also significantly affect the interface resistance.3. Testing method(1) Four probe method: Quickly screen for batch uniformity, but cannot measure the contact resistance between the current collector and the coating.(2) EIS (Electrochemical Impedance Spectroscopy): By separating contact impedance information in the high-frequency region, a reliable equivalent circuit model is required. (3) Symmetric battery or three electrode half battery: used for mechanism research to separate interface resistance from overall impedance, but not suitable for production lines. (4) Combination strategy: First, use four probes for rapid screening, then analyze the frequency response using EIS, and finally observe the cross-section using SEM or focused ion beam to comprehensively evaluate the interface state.4. ConclusionThe control of interface resistance requires comprehensive consideration of formula, process, and testing methods to avoid blindly pursuing low resistivity, and should focus on the actual effectiveness of electronic and ion channels. Through multidimensional testing and process optimization, interface resistance can be effectively reduced and battery performance can be improved.Be Power is committed to providing customers with high-quality and customized solutions；We are the number one Chinese battery supplier delivered to automotive OEM in Brazil.We offered battery for over 800K set HESS systems;We are the best UTV battery supplier and exporter in China, with over 15 years of experience in lithium battery research and development.We are the best battery pack solution provider in China.Our battery systems are warmly welcomed in over 30 countries applied on electric trucks，electric light vehicles，electric UTV, electric sweepers, container energy storage systems, 215Kwh commercial and industrial energy storage systems etc. With top-notch technical team in China we are providing the toughest technical and highest level safety products.
-
10
2026-03
What are the reasons for lithium battery gas production?
The root cause of gas production in lithium batteries is essentially the result of a series of unwanted chemical and electrochemical side reactions inside the battery. These reactions consume the active ingredients in the battery and generate gaseous products, leading to a decrease in battery performance and even causing safety issues. The gas production of lithium batteries mainly comes from the following aspects:1. Electrolyte decompositionWhen used improperly at high temperatures or voltages (such as overcharging), organic solvents in the electrolyte can undergo oxidation or reduction reactions and decompose. The main gases are:Carbon dioxide (CO ₂), carbon monoxide (CO), methane (CH ₄), ethylene (C ₂ H ₄), etc. two SEI film damage and recombination.2. SEI film damage and recombinationIf the SEI protective film on the negative electrode surface ruptures due to overcharging, overdischarging, or high temperature, the electrolyte will directly react with the negative electrode material in an attempt to repair the SEI film, and this process will continuously generate gas.The main gases are:Hydrogen (H ₂), ethylene (C ₂ H ₄), ethane (C ₂ H ₆), etc.3. Excessive moisture contentEven trace amounts of water (ppm level) can react with lithium salts (such as lithium hexafluorophosphate LiPF ₆) in the electrolyte, generating corrosive hydrofluoric acid (HF) and further triggering side reactions to produce gas. The main gases are:Hydrogen (H ₂), hydrogen fluoride (HF), carbon monoxide (CO), carbon dioxide (CO ₂).4. Side reactions of positive electrode materialsUnder overcharging or high temperature, the structure of positive electrode materials (especially high nickel ternary materials) may collapse, releasing oxygen. The released oxygen will oxidize the electrolyte, producing more gas. The main gases are:Oxygen (O ₂), carbon dioxide (CO ₂).5. Negative electrode material side reactionsFor materials such as silicon anodes, significant volume changes during charge and discharge can repeatedly damage the SEI film, leading to sustained side reactions and gas production. Under excessive discharge or high temperature, the graphite negative electrode will also react with the electrolyte. The main gases are:Hydrogen (H ₂), Ethylene (C ₂ H ₄), Ethane (C ₂ H ₆).
-
25
2026-02
The difference between semi-solid, quasi solid, and all solid state batteries
We often see in the media and online that a certain company has made a huge breakthrough in solid-state batteries. Alternatively, a company may announce the mass production of solid-state batteries by 202X. Perhaps they only dare to say that it is a solid-state battery, and dare not say that their battery is an all solid state battery.Solid state batteries can simply include (semi-solid, quasi solid, and all solid state batteries), and in order to appear high-end and attract attention, they directly refer to solid-state batteries.What is the difference between the three?The core difference between semi-solid, quasi solid, and all solid state batteries lies in the physical state of the electrolyte, ion conductivity, interface issues, and industrial maturity.The following comparison chart can clearly summarize the core differences and evolutionary relationships among the three:Detailed explanation of core differences1. All solid state batteryElectrolyte state: 100% solid, without any liquid electrolyte. Solid electrolytes such as oxides, sulfides, or polymers are usually used. Key features:Highest safety: completely eliminate the risks of leakage, combustion, and explosion (especially when using metal lithium negative electrodes).The maximum potential for energy density: compatible with high-voltage positive electrodes and metal lithium negative electrodes, theoretically with an energy density of over 500 Wh/kg. The interface problem is the most severe: solid solid contact leads to high interface impedance, difficult ion transport, and the biggest challenges are rate performance and cycle life. Cost and process are extremely difficult: the preparation process is complex (such as the processing of brittle electrolytes, thin film preparation), the cost is extremely high, and mass production is the most difficult. Current situation: In the research and development and pilot stage, it is widely recognized as the "ultimate solution", but the road to commercialization is the longest. Representative companies: Toyota, QuantumScape。2. Quasi solid state batteriesElectrolyte state: "quasi solid" or "gelled", containing a small amount (usually<5%) of liquid electrolyte or plasticizer, wetting the space between solid electrolyte particles with a very small amount of liquid. Key features:Transitional solution: It can be seen as a preparatory form of all solid state battery. It sacrifices "absolute solid state" in exchange for more feasible interface performance. Interface improvement: Trace amounts of liquid greatly enhance the ion transport capability of the solid solid interface and reduce interface impedance. Performance Balance Point: Seeking a feasible balance between safety, energy density, and electrochemical performance. Its energy density and safety are still significantly higher than liquid state batteries, but slightly inferior to ideal all solid state batteries. The manufacturing process is relatively friendly: closer to existing production lines than all solid state. Current situation: Often overlapping or mixed with the concept of "semi-solid", it is a crucial step for many enterprises to move from semi-solid to all solid state.3. Semi solid state batteriesElectrolyte state: solid-liquid mixture, coexistence of solid electrolyte and liquid electrolyte, with high liquid content (usually>5%, even up to 10-20%). Key features:Compromise and improvement plan: Essentially, it is a "heavy improvement" of existing liquid lithium-ion batteries, rather than a subversion. Solid electrolyte coatings or composites with electrode materials are commonly used. Improved safety: The quality of liquid electrolysis has been reduced, reducing the risk of combustion, but it has not been completely eradicated. Significant improvement in energy density: High capacity positive and negative electrode materials (such as high nickel and silicon carbon) can be partially applied, with an energy density of 300-400 Wh/kg. Compatible with existing production lines: The production process adjustment is relatively small, making it the first route to achieve commercial mass production. There is still a risk of leakage: essentially still belongs to the category of "liquid batteries".Current situation: It has entered the stage of mass production and installation. Representative applications: NIO's 150kWh semi-solid battery pack (Weilan New Energy), Lantu Chasing Light (Ganfeng Lithium), etc.
-
25
2025-11
What are the hazards of poor cell consistency in power batteries?
We know that a car's battery is composed of many battery cells. Generally, modules are composed of battery cells, and the modules form a PACK. For example, the Tesla Model S's battery system is carefully composed of 7104 18650 lithium batteries. The Xiaomi SU7 Max battery pack is composed of 198 battery cells connected in series. With so many battery cells, if one of them is faulty, it's easy to carry the whole into the ditch. As a familiar saying goes, "A piece of mouse dung will kill a pot of porridge". So the consistency of battery cells in power batteries is very important. 1、 The harm caused by poor consistencyPoor consistency of battery cells in power batteries can cause various hazards, directly affecting battery performance, safety, lifespan, and overall vehicle reliability. The following is a specific analysis of hazards and mechanisms:① Capacity degradation and battery life decreaseShortboard effect: In cells with poor consistency, the unit with the lowest capacity will be the first to fully charge or empty, resulting in the overall available capacity of the battery pack being limited by the "weakest cell".Example: If the capacity of a certain battery cell is 10% lower than others, the entire battery pack capacity may be lost by 5% to 8%, significantly reducing the vehicle's range. ② Safety hazards: thermal runaway, fire and explosionRisk of overcharging/overdischarging: When the voltage is inconsistent, some cells may be forcibly charged to overvoltage (>4.3V) or discharged to undervoltage (<2.5V), causing lithium dendrite growth, piercing the diaphragm and causing internal short circuit, ultimately leading to thermal runaway.Uneven heat distribution: Cells with large internal resistance or temperature differences overheat locally during charging and discharging, forming "hotspots" and accelerating heat diffusion. ③ Significantly shortened battery lifeAging acceleration: Cells with poor consistency are subjected to uneven loads during cycling. For example, repeated overdischarging of low capacity cells can accelerate the decay of electrode materials, potentially shortening their lifespan by 30% to 50%.Chain reaction: The failure of a single battery cell (such as a sudden drop in capacity) will force other battery cells to compensate, exacerbating overall aging. ④ Failure of Battery Management System (BMS)SOC/SOH estimation distortion: BMS relies on cell parameter consistency for precise management. If the difference in battery cells is too large, BMS may not be able to accurately estimate the remaining state of charge (SOC) or state of health (SOH), and may misjudge the battery status.Overload of balancing function: BMS needs to frequently balance cells with significant differences, resulting in increased energy consumption and limited effectiveness, ultimately leading to overload or failure of the balancing circuit.2、 How to screen out cells with poor consistencyThe following are the methods and steps for consistency screening of battery cells:① Voltage matching: That is, OCV testing measures the open circuit voltage (OCV) of the battery cell after it has been idle (usually 24-48 hours), and eliminates cells with voltage deviations exceeding the set threshold (such as ± 5mV).② Capacity sorting: Obtain the actual capacity of the battery cells through charge and discharge tests, and divide them into capacity intervals (such as ± 1%) to ensure that the difference in battery cell capacity within the same battery pack is minimized. ③ Internal resistance screening: Measure the DC internal resistance (DCR) or AC internal resistance (ACR), and remove cells with high internal resistance or large dispersion (such as internal resistance deviation>3%). ④ Self discharge rate (K value) test: After fully charging the battery cell, let it stand for 7-14 days, calculate the self discharge rate (K value) based on the voltage drop, and screen for cells with similar K values (such as K value difference<0.5%). The role of K=(OCV1- OCV2)/(t2- t1) K value testing should not be underestimated.⑤ Aging and cycle testingHigh temperature aging screening: Place the battery cells in a high-temperature environment (such as 45 ℃) and monitor the voltage decay rate to screen for cells with consistent aging characteristics. Cycle life pre-test: Perform a small amount of charge and discharge cycles on the battery cell (such as 50 times) to eliminate cells with abnormal capacity decay or sudden internal resistance changes.When selecting power batteries, the quality of the battery cells will greatly affect the performance of the entire battery pack, so it is necessary to conduct strict inspections of product quality and suppliers in the early stage. As a professional lithium battery supplier，Be Power is committed to providing customers with high-quality and customized solutions；We are the number one Chinese battery supplier delivered to automotive OEM in Brazil.We offered battery for over 800K set HESS systems;We are the best UTV battery supplier and exporter in China, with over 15 years of experience in lithium battery research and development.We are the best battery pack solutions provider in China.Our battery systems are warmly welcomed in over 30 countries applied on electric trucks，electric light vehicles，electric UTV, electric sweepers, container energy storage systems, 215Kwh commercial and industrial energy storage systems etc. With top-notch technical team in China we are providing the toughest technical and highest level safety products.
-
24
2025-10
Congratulations to our partner Great Power for being listed as a BNEF Tier1 global first tier energy storage manufacturer for 4 consecutive times!
Great Power has been listed as a BNEF Tier1 global first tier energy storage manufacturer for four consecutive times! Recently, Bloomberg NEF (Bloomberg New Energy Finance, abbreviated as BNEF), a globally renowned research institution, officially released the Global Tier 1 Energy Storage Tier 1 List 2Q 2025 for the second quarter of 2025.BNEF rigorously evaluates project scale, technological innovation, supply chain resilience, financial health, and global market influence from multiple dimensions. Every year, only the top energy storage companies with comprehensive strength are selected to enter the Tier 1 list. Its rating results are regarded as industry benchmarks by global energy giants, investment institutions, and governments.Great Power has made a strong breakthrough among global energy storage companies with its innovative product technology, leading intelligent manufacturing, efficient global delivery system, and full cycle project execution control capabilities. It has been ranked as a BNEF Tier 1 global first level energy storage manufacturer for four consecutive times, marking Great Power's continuous recognition of its comprehensive strength by international authorities！As the overseas partner of Great Power, Be Power is committed to providing customers with high-quality and customized solutions；We are the number one Chinese battery supplier delivered to automotive OEM in Brazil.We offered battery for over 800K set HESS systems;We are the best UTV battery supplier and exporter in China, with over 15 years of experience in lithium battery research and development. Our battery systems are warmly welcomed in over 30 countries applied on electric trucks，electric light vehicles，electric UTV, electric sweepers, container energy storage systems, 215Kwh commercial and industrial energy storage systems etc. With top-notch technical team in China we are providing the toughest technical and highest level safety products!
-
05
2025-09
Lithium battery voltage consistency: importance, impact, and how to improve it
The importance of voltage consistency in lithium batteries.The voltage consistency of lithium batteries refers to the ability of individual lithium batteries in the same batch or system to maintain consistent terminal voltage under the same operating conditions. Voltage consistency has a crucial impact on the performance, lifespan, and safety of lithium battery packs. 1. Voltage consistency is related to the overall performance of lithium battery packs.In a battery pack, if there is a voltage difference between individual cells, some cells may reach their upper or lower voltage limit in advance during the charging and discharging process, resulting in the entire battery pack not being able to fully utilize its capacity, thereby reducing overall energy efficiency.2. Voltage consistency has a direct impact on the safety of lithium batteries.When the voltage of individual cells in the battery pack is inconsistent, some cells may experience thermal runaway due to overcharging or overdischarging, leading to safety accidents such as fires or explosions. 3. Voltage consistency also affects the lifespan of lithium batteries. Due to inconsistent voltage, some individual cells in the battery pack may experience more charge and discharge cycles, leading to a shortened lifespan and ultimately affecting the overall service life of the battery pack.The impact of inconsistent voltage on lithium batteries1. Performance degradation: The voltage difference between individual cells can lead to a decrease in the overall performance of the battery pack. During the discharge process, batteries with lower voltage will limit the discharge voltage and capacity of the entire battery pack, thereby reducing the energy output of the battery pack. 2. Unbalanced charging and discharging: Inconsistent voltage can cause uneven charging and discharging of the battery pack. Some batteries may be fully charged or emptied in advance, while others may not have reached their charging and discharging limits, which can lead to a decrease in the overall capacity utilization of the battery pack. 3. Risk of thermal runaway: Inconsistent voltage may increase the risk of thermal runaway in the battery pack. Overcharged or overdischarged batteries may generate a large amount of heat. If the heat is not dissipated in a timely manner, it may cause thermal runaway of the battery and result in safety accidents. 4. Shortened lifespan: Inconsistent voltage can lead to increased differences in the lifespan of individual cells within the battery pack. Some batteries may fail prematurely due to excessive charging and discharging, thereby affecting the lifespan of the entire battery pack.How to improve the voltage consistency of lithium batteries1. Strengthen battery management system: Battery management system (BMS) is the key to ensuring battery voltage consistency. By monitoring and adjusting the voltage between battery cells in real-time, BMS can ensure that the battery pack maintains voltage consistency during charging and discharging processes. In addition, BMS can also achieve balanced management of battery packs, avoiding overcharging or overdischarging of individual batteries. 2. Implement regular maintenance and calibration: Regular maintenance and calibration of lithium battery packs can maintain voltage consistency between battery cells. For example, regular charging and discharging calibration of battery packs can ensure that each battery cell reaches the same charging and discharging state, thereby improving voltage consistency. 3. Adopting advanced battery balancing technology: Battery balancing technology is an effective means of improving battery voltage consistency. By actively or passively balancing, the voltage difference between battery cells can be reduced to an acceptable range, ensuring that the battery pack maintains voltage consistency during charging and discharging processes. 4. Improve the usage environment: The usage environment also has a certain impact on the voltage consistency of lithium batteries. By improving the usage environment of batteries, such as reducing temperature fluctuations, minimizing vibration and shock, the impact of environmental factors on battery performance can be reduced, thereby maintaining battery voltage consistency.ConclusionThe voltage consistency of lithium batteries has a significant impact on the performance, safety, and lifespan of battery packs. Inconsistent voltage may lead to performance degradation, uneven charging and discharging, increased risk of thermal runaway, and shortened lifespan of the battery pack. Therefore, improving the voltage consistency of lithium batteries is crucial. Choosing products from high-quality and reliable battery manufacturers can effectively ensure the voltage consistency of lithium batteries, thereby ensuring the safe, stable, and efficient operation of battery packs.Be Power is committed to providing customers with high-quality and customized solutions；We are the number one Chinese battery supplier delivered to automotive OEM in Brazil.We offered battery for over 800K set HESS systems;We are the best UTV battery supplier and exporter in China, with over 15 years of experience in lithium battery research and development.We are the best battery pack solution provider in China.Our battery systems are warmly welcomed in over 30 countries applied on electric trucks，electric light vehicles，electric UTV, electric sweepers, container energy storage systems, 215Kwh commercial and industrial energy storage systems etc. With top-notch technical team in China we are providing the toughest technical and highest level safety products.
-
22
2025-08
What is RCH testing and testing methods for lithium batteries
The RCH testing of lithium batteries is an important means of evaluating their performance and safety. Through these tests, we can understand the performance and safety of batteries under different conditions, and provide important reference for the development and improvement of batteries. Lithium battery RCH test1. R test: Test the charging and discharging performance of the battery, evaluate its performance under different charging and discharging states through cyclic charging and discharging processes, such as capacity, charging and discharging efficiency, energy density, and other parameters.2. C test: Test the cycle life of the battery, evaluate the battery's lifespan and capacity loss by simulating the charging and discharging cycles of the battery in actual use. By conducting the C test, we can understand the degree of performance degradation of the battery under different charging and discharging conditions. 3. H testing: Testing the safety of batteries by examining their performance under extreme conditions such as high temperature, overcharging, and overdischarging to evaluate their safety performance. H testing can identify potential safety hazards in batteries and ensure their safety during use.Test purposeThe purpose of RCH testing for lithium batteries is to evaluate their performance under R (reverse), C (charging), and H (high temperature) conditions, in order to ensure their safety and reliability in practical use.Testing equipment and methods1. Equipment: Lithium battery testing cabinet, constant temperature box, charge and discharge tester, data acquisition system, etc. 2. Method: According to the testing standards, place the lithium battery in a constant temperature chamber to simulate a high-temperature environment. Then, the lithium battery is subjected to reverse charging and discharging operations using a charging and discharging tester, and data is recorded in real-time.Problem examples and improvement measures1. Problem: During the charging process, some lithium batteries experience a rapid temperature rise.Improvement measures: Optimize charging strategy, reduce charging current to slow down temperature rise rate.2. Problem: The capacity of some lithium batteries has decreased.Improvement measures: Optimize the manufacturing process of lithium batteries to improve their capacity retention rate in high-temperature environments.ConclusionThrough RCH testing, we can discover the performance of lithium batteries in high-temperature environments, which can be optimized to address existing issues and provide strong guarantees for their safety and reliability in practical applications.
-
14
2025-07
The difference between AC impedance and DC internal resistance of lithium batteries
In the research and application of lithium batteries, internal resistance is an important parameter that reflects the energy loss and electrochemical reaction state inside the battery. Internal resistance is mainly divided into DC resistance and AC impedance. This article will provide a detailed introduction to the difference between AC impedance and DC internal resistance of lithium batteries.1.Definition and measurement methods① DC internal resistance (DCR): DC internal resistance refers to the ratio of the voltage change of a battery to the corresponding discharge current change under working conditions. It is usually expressed in ohms (Ω) and can be measured using a dedicated battery internal resistance tester or multimeter with current and voltage settings. ② AC Impedance: AC impedance is derived by injecting sine wave current signals into the positive and negative terminals of a battery, and detecting the sine wave voltage signals at the other two terminals.2. Characteristics① Characteristics of DC internal resistance measurement: Suitable for large capacity batteries: This method requires applying a large test current (40-80A, 2-3 seconds), which small capacity batteries may not be able to withstand. Short testing time: High current can cause polarization resistance, so the testing time must be short to avoid excessive impact on the battery. There may be losses: High current testing may cause certain losses to the battery.② Characteristics of AC internal resistance measurement: Short testing time: AC internal resistance measurement only requires the application of a fixed frequency and current (currently 1KHz, 50mA), sampling voltage, rectification and filtering processing, and calculation of resistance value through an arithmetic circuit. The entire process only takes 0.1 seconds. Suitable for various battery types: Due to the small testing current, it causes almost no damage to the battery, making it suitable for almost all battery types. Relatively low accuracy: The accuracy of the AC internal resistance testing method is 1% -2%, which is not as accurate as the DC internal resistance testing method.3. Reflected information① DC internal resistance: DC internal resistance more directly reflects the Ohmic impedance inside the battery, including the resistance of electrode materials, electrolyte, separators, and other parts. It can provide information about the internal conductivity of the battery.② AC impedance: In addition to Ohmic impedance, AC impedance can also reflect the electrochemical reaction impedance inside the battery. The semi-circular part is related to the charge transfer at the interface between the electrolyte and electrode material, while the low-frequency part is related to the diffusion of lithium ions in the electrolyte and positive and negative electrode materials. AC impedance can provide more comprehensive information on battery electrochemical reactions4. Application scenarios① DC internal resistance: DC internal resistance is commonly used to evaluate the power performance and performance of batteries in practical use. It is of great significance for the discharge capacity and charging efficiency of batteries. ② AC impedance: AC impedance is widely used in battery research and development, quality control, and electrochemical analysis. It can help study the electrochemical reaction mechanism, interface performance, and aging process of batteries.5. The influence of temperature, state of charge, and charge discharge state① Temperature: Temperature has a significant impact on the internal resistance of lithium batteries. Generally speaking, as the temperature decreases, the internal resistance of the battery will increase. This is because ion transport and electrochemical reaction rates slow down at low temperatures.② State of Charge (SOC): The state of charge of a battery also affects its internal resistance. During the discharge process, as the discharge depth increases, the internal resistance usually increases. This is due to changes in the internal electrochemical reactions of the battery and changes in the electrode structure.③ Charging and discharging status: Charging and discharging status can also affect internal resistance. For example, during the charging process, the internal resistance of the battery may increase, while during the discharging process, the internal resistance may decrease.6. Overall considerationIn practical applications, the measurement results of DC internal resistance and AC impedance are usually considered comprehensively to gain a more comprehensive understanding of battery performance. DC internal resistance can more accurately reflect the superposition of various resistances and capacitances inside the battery, while AC impedance provides more information about electrochemical reactions. Meanwhile, by analyzing factors such as temperature and state of charge, the health status and performance of the battery can be more accurately evaluated.7. SummaryThere are significant differences in the definition, measurement methods, characteristics, and reflected information between the AC impedance and DC internal resistance of lithium batteries. Understanding these differences helps us choose appropriate testing methods and interpret test results correctly, thereby better evaluating the performance and status of lithium batteries. In practical applications, according to specific needs and conditions, one can choose to use DC internal resistance testing or AC impedance testing, or combine the two for a more comprehensive analysis.
-
25
2025-06
Detailed explanation of the basic knowledge of lithium battery voltage: open circuit voltage
The voltage characteristics of lithium batteries are the core indicators for measuring their performance and safety, directly affecting the charging and discharging efficiency, cycle life, and application safety of the battery. This article will systematically introduce four key voltage parameters of lithium batteries - open circuit voltage (OCV), operating voltage (WV), discharge cut-off voltage (DCV), and charge limiting voltage (LCV), to help you comprehensively understand the definition, influencing factors, and practical application points of voltage parameters.This article provides a detailed explanation of the open circuit voltage involved.1. Open circuit voltage (OCV)Open circuit voltage (OCV) refers to the voltage value of a circuit when the power supply or component is disconnected from the load. It reflects the electromotive force of the power supply or the inherent voltage characteristics of the components when no current passes through, for example, the open circuit voltage of a battery is usually close to its nominal voltage, while the open circuit voltage of a capacitor is consistent with its charged voltage.The open circuit voltage is the potential difference between the positive and negative electrodes of a lithium battery in its non working state (with no current flowing), determined by the chemical equilibrium potential difference of the positive and negative electrode materials. OCV is an important basis for evaluating the state of charge (SOC) of a battery, and its value shows a regular curve as the remaining capacity of the battery changes.The OCV of lithium batteries with different material systems shows significant differences:Ternary lithium battery: OCV is about 4.2V when fully charged, and drops to 3.6-3.7V when discharged to 50% SOC;Lithium iron phosphate battery: The OCV at full charge is about 3.65V, and the platform voltage remains stable at around 3.2V; Lithium manganese oxide battery: The OCV range is similar to that of ternary batteries, but the voltage platform is slightly lower. In practical applications, OCV needs to be measured after the battery has been idle for more than 2 hours to avoid numerical deviation caused by polarization effects after charging and discharging. Long term storage of lithium batteries is recommended to maintain a 70% SOC (corresponding to an OCV of approximately 3.8V) to minimize capacity degradation.2. Measurement method and key points of open circuit voltage (OCV) of lithium batteriesRequirements for measuring tools and equipment① Core ToolsWhen using a DC voltmeter (such as a multimeter or specialized battery tester) to directly connect the positive and negative terminals of the battery for measurement, it is necessary to ensure that the instrument resolution is ≥ 0.1mV, the accuracy meets the error requirements under the 10V range, and has temperature compensation function.② Key parameters for selection:Resolution: High resolution (such as 0.1 μ V level) can identify small voltage differences, facilitating early detection of defective cells; Accuracy: Calculated based on "reading error+resolution error", it is recommended to use a 10V range for a 4V battery; Temperature compensation: Every 1 ° C change in ambient temperature may cause OCV to fluctuate by hundreds of μ V, which needs to be converted to the standard temperature value through compensation function.Measurement steps and timing3. Precautions① Polarization effect differentiationOCV1 (Instantaneous Voltage): The initial value measured immediately after charging and discharging, which is greatly affected by polarization;OCV2 (Stable Voltage): The equilibrium value that eliminates polarization after settling, which is closer to the true electrochemical equilibrium potential and is the core basis for evaluating SOC and SOH.② Environmental controlMaintain stable measurement environment temperature or correct readings through device temperature compensation function to avoid measurement errors caused by temperature fluctuations.③ Safe operationConfirm that the battery has no physical damage before measurement to avoid short circuits; High voltage battery packs require the use of insulated tools to prevent the risk of electric shock.4. Application scenariosProduction screening: Remove defective cells with abnormal self discharge through OCV differences to ensure consistency of the battery pack;Performance evaluation: Analyze battery capacity degradation and aging degree by combining OCV-SOC curve (such as discharge platform voltage);BMS optimization: Real time monitoring of OCV to dynamically adjust charging and discharging strategies, extending battery cycle life.5. Special measurement method (patented technology)Rapid testing method: By short-term charging and discharging (<5s) and multiple cycles of depolarization, the settling time is shortened (the total testing time is reduced by more than 50%), which is suitable for mass production rapid testing scenarios.Curve fitting method: Draw an OCV curve by combining the midpoint of the charge discharge voltage curve to improve the accuracy of SOC estimation. Note: In actual operation, the measurement scheme should be selected according to the application scenario (laboratory/production line). For high-precision scenarios, specialized battery testers should be prioritized and environmental variables should be strictly controlled.6. SummaryIn summary, open circuit voltage (OCV), as the core electrochemical characteristic parameter of lithium batteries in non working states, is not only a key basis for evaluating the state of charge (SOC), but its numerical differences also directly reflect the inherent characteristics of different material systems (such as ternary, lithium iron phosphate, lithium manganese oxide). By standardizing the measurement process (static elimination of polarization, high-precision equipment and temperature compensation) and scientific analysis methods (OCV-SOC curve, rapid measurement technology), OCV plays an irreplaceable role in production screening of defective cells, evaluation of battery aging degree, optimization of BMS charging and discharging strategies, and other scenarios. In practical applications, it is necessary to pay attention to the differentiation of polarization effects and environmental control, while following the maintenance principle of long-term storage to maintain 70% SOC (OCV about 3.8V), in order to maximize the performance stability and cycle life of lithium batteries.
-
06
2025-05
What are the main structural components of lithium-ion batteries?
Lithium ion batteries are an important energy storage device widely used in fields such as mobile electronic devices and electric vehicles. This article will provide a detailed introduction to the main structural components of lithium-ion batteries, including positive electrode materials, negative electrode materials, electrolytes, separators, and current collectors. Meanwhile, the influence of different materials on the performance of lithium-ion batteries will also be explored. Through a deep understanding of the structure of lithium-ion batteries, theoretical foundations can be provided for battery design and optimization.1. IntroductionLithium ion battery is a type of battery that converts electrical energy through the migration of lithium ions between the positive and negative electrodes. It has the advantages of high energy density, low self discharge rate, and long cycle life, and is therefore widely used in various electronic devices and transportation vehicles. The performance of lithium-ion batteries mainly depends on their structural composition, so a deep understanding of the structural composition of lithium-ion batteries is of great significance for battery design and optimization.2、 Positive electrode materialThe positive electrode material is an important component of lithium-ion batteries, whose main function is to store and release lithium ions. Common positive electrode materials include lithium manganese oxide, lithium cobalt oxide, ternary materials, etc. Lithium manganese oxide has a high specific capacity and low cost, but a short cycle life; Lithium cobalt oxide has a high specific capacity and good cycle life, but the cost is relatively high; Ternary materials have high specific capacity and good cycle life, but they are expensive. Therefore, in practical applications, it is necessary to select suitable positive electrode materials according to specific needs.3、 Negative electrode materialNegative electrode material is another important component in lithium-ion batteries, whose main function is to store and release lithium ions. Common negative electrode materials include graphite, silicon, etc. Graphite has a high specific capacity and good cycle life, but its capacity is limited; Silicon has a high specific capacity, but the capacity decays rapidly. Therefore, in practical applications, a balance needs to be struck between graphite and silicon to meet the needs of different application scenarios.4、 ElectrolyteThe main function of electrolyte is to provide a transport medium for lithium ions. Common electrolytes include organic electrolytes and solid electrolytes. Organic electrolytes have high conductivity and good lithium ion transport performance, but there are safety hazards such as combustion and volatilization; Solid electrolyte has good safety performance, but low conductivity. Therefore, in practical applications, it is necessary to choose the appropriate electrolyte based on safety and performance requirements.5、 DiaphragmThe main function of the diaphragm is to prevent short circuits between the positive and negative electrodes. Common membranes include polyolefin membranes, ceramic membranes, etc. Polyolefin film has good electrical conductivity and isolation performance, but poor thermal stability; Ceramic membranes have good thermal stability and isolation performance, but low electrical conductivity. Therefore, in practical applications, it is necessary to choose a suitable separator based on the safety and performance requirements of the battery6、 Collector fluidThe main function of a current collector is to collect and distribute electrical current. Common current collectors include copper foil, aluminum foil, etc. Copper foil has good conductivity and mechanical strength, but it is relatively expensive; Aluminum foil has a lower price, but its conductivity is poor. Therefore, in practical applications, it is necessary to choose a suitable current collector based on cost and performance requirements.7. ConclusionThe main structural components of lithium-ion batteries include positive electrode material, negative electrode material, electrolyte, separator and current collector, sealing ring, positive electrode cap, battery case, etc. The selection of different materials has a significant impact on the performance of lithium-ion batteries. By delving into the structural composition of lithium-ion batteries, a theoretical foundation can be provided for battery design and optimization. In the future, with the advancement of technology, the structural composition of lithium-ion batteries may change to meet higher performance and safer requirements.
