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Battery charging and discharging once is called a cycle, cycle life is an important indicator of the battery life performance. Factors affecting the cycle life of lithium-ion batteries inherent in the root cause, is to participate in the energy transfer of lithium ions in the number of decreasing. The total amount of lithium in the battery does not decrease, but the "activated" lithium ions are less, they are confined in certain places or the transmission channel is blocked, and can not freely participate in the charging and discharging process. Specifically: (1) Precipitation of lithium metal (2) Decomposition of cathode material (3) SEI film on the electrode surface: carbon anode material, during the initial cycle, the electrolyte will form a solid electrolyte (SEI) film on the electrode surface, and the formation process of SEI film will consume lithium ions. (4) Loss of electrolyte (5) Diaphragm blockage or damage (6) Dislodging of cathode and anode electrode materials  Email : tob.amy@tobmachine.com  Skype : amywangbest86  Whatsapp/Phone number : +86 181 2071 5609

Common Problems and Solutions for Binder  (PVDF, SBR, CMC, PAA, etc.) What about slurry settlement? Reason: l  The selected CMC type is not applicable, and the degree of substitution and molecular weight of CMC will affect the stability of the slurry to a certain extent, such as poor hydrophilicity of CMC with low substitution, good wettability to graphite, but poor suspension capacity of slurry; l  The amount of CMC is small, and the slurry cannot be effectively suspended; l  Too much CMC is involved in the kneading process, resulting in insufficient CMC free between particles and in suspension, which often leads to poor slurry stability; l  High mechanical forces and fluctuations in the acidity or alkalinity of the slurry can lead to breakage of the SBR, which can cause the slurry to settle; Solutions: l  Change or match CMC with high substitution degree and high molecular weight, for example, match WSC with CMC2200 in mass production formula, WSC itself has low molecular weight and low substitution degree, good wetting of graphite and weak suspending ability, after matching with CMC2200, the stability of the slurry has been greatly improved; l  Increasing the amount of CMC is one of the most effective means of improving paste stability, but it is important to find a balance between process capability and the low temperature performance of the cell; l  Reducing the amount of CMC used in kneading and increasing the amount of free CMC can improve the stability of the paste to a certain extent; l  After SBR is added to the slurry system, the stirring speed of the rotation should be reduced; What should I do if the hole is blocked during filtration and cannot be filtered? Reason: l  poor wetting of the active substance, no dispersion; l  Failure to filter due to SBR emulsion breakage; Solution: l  Using kneading process; l  After SBR is added to the slurry system, the stirring speed of the rotation should be reduced to prevent the occurrence of demulsification; What should I do if there is gel in the slurry? Reason: Gel production is mainly divided into two types, one is a physical gel and the other is a chemical gel. l  Physical gel: Cathode active materials, SP, solvent NMP have absorbed water, or the water content in the environment exceeds the standard, which is easy to form physical gels.This is because the polymer chain of PVDF is wrapped around the particles, and when the content of the slurry exceeds the standard, the polymer chain movement is blocked, and the polymer chains are entangled with each other, which reduces the fluidity of the slurry and the gel phenomenon occurs. l  Chemical gels: Chemical gels are prone to occur in the process of preparing high nickel or highly basic active materials or in stationary processes.This is because PVDF in the high pH environment of the base (as shown in the figure below), the polymer backbone is easy to de-HF to form double ...

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In lithium-ion batteries, the binder is one of the important factors affecting the stability of the electrode structure. According to the nature of the dispersing medium, lithium-ion battery binder can be divided into oil-based binder with organic solvent as dispersant and water-based binder with water as dispersant. Liu Xin et al [3] reviewed the research progress of binder for high-capacity negative electrode. Thinking about the application of polyvinylidene fluoride (PVDF)-modified binders and water-based binders, Can improve the performance of high-capacity negative electrode electrochemistry. However, there is no discussion or comparison for binders for silicon-based negative electrodes. In this paper, the authors provide an overview of the research progress on binders for silicon-based anode materials and compare the advantages and disadvantages of different types of binders. 1.     Oil-based binder Among the oil-based binders, homopolymers and copolymers of PVDF are the most widely used. 1.1  PVDF Homopolymer Binder In the large-scale production of lithium-ion batteries, PVDF is commonly used as a binder, and organic solvents such as N-methyl pyrrolidone (NMP) are used as dispersants. PVDF has good viscosity and electrochemical stability, but poor electronic and ionic conductivity, Organic solvents are volatile, flammable, explosive and highly toxic; Moreover, PVDF is only bonded to the Si-based anode material by weak van der Waals forces and cannot accommodate the dramatic volume change of Si. Conventional type PVDF is not suitable for silicon-based anode materials [3 -5]. 1.2  PVDF modified binder In order to get the improved electrochemical performance of PVDF applied to silicon-based anode materials, Some scholars have proposed modification methods such as copolymerisation and heat treatment [4-5]. Z. H. Chen and other scholars [4] found that: The terpolymer polyvinylidene fluoride-tetrafluoroethylene-ethylene copolymer [P(VDF- TFE-P)] enhances the mechanical properties and viscoelasticity of PVDF. J. Li and other scholars [5] found that. Heat treatment at 300°C and under argon protection improves the dispersion and viscoelasticity of PVDF. The modified PVDF/Si electrode was cycled 50 times at 150 mA/g at 0.17 ~ 0_ 90 V with a specific capacity of 600 mAh/g. By modifying and treating the PVDF/Si electrode, the cycling performance was improved, but the cycling stability was still unsatisfactory. 2.     Water-based binder Compared to oil-based binders, water-based binders are environmentally friendly, inexpensive and safer to use, and are gradually gaining popularity. Currently, the more researched silicon-based anode material binders are water-based binders such as sodium carboxymethyl cellulose (CMC) and polyacrylic acid (PAA). 2.1 Styrene-Butadiene Rubber (SBR)/Sodium Carboxymethyl Cellulose Abatement (CMC) Binder SBR/CMC has good viscoelasticity and dispersibility, and has been widely...

Power battery thermal management is an important technology in the field of new energy vehicles, its role is to ensure that the temperature of the power battery can be within a safe range during the use of the vehicle, and improve the battery life and service life, thermal management materials are the technical support to achieve this goal. The following is an introduction to you: what thermal management materials are specifically needed for new energy vehicle power batteries. A  Thermally conductive materials Heat conductive materials play a key role in the thermal management of power batteries, at present, power batteries are often used: heat conduction paste, heat conduction sheet two types of heat conduction materials. The thermal conductivity of heat conduction paste is generally in the range of 1-8 W/mK, which is a thermal conductive material that transfers heat from the high temperature area to the low temperature area, and is usually used for the contact surface of the battery and the heat sink. The preparation of heat conduction paste can use diamond particles, silicon nitride and other thermal conductive particles as a carrier, and the theat conduction paste can fill fine voids and cracks, because this advantage is widely used in the thermal management of power batteries. The heat conduction sheet is usually made of copper or aluminum, and the thermal conductivity is often about 200 W/mK, which can not only evenly transfer heat from the surface of the battery to the nearby radiator, but also evenly cool the heat of the radiator and the surface of the battery, and at the same time improve the adsorption of the radiator to the battery and avoid the radiator falling off in the vibration state. B  Thermal barrier materials Thermal barrier material is a material that can slow down the flow of heat, and the thermal conductivity is often in the range of 0.2-0.35 W/mK, which has the characteristics of easy processing and molding.It is often used inside the battery module and installed between the battery cell and the radiator to reduce the temperature gradient, so as to reduce the surface temperature of the battery and ensure the safety of the battery. Thermal barrier materials include: insulating thermal insulation materials and composite thermal insulation materials.The main raw materials of insulation materials are glass fiber, ceramics, etc., which are often installed between the battery cell and the radiator to reduce the surface temperature of the battery.Composite thermal insulation materials are usually composed of a variety of performance materials, such as nano-silica and polymers, its role is to block the conduction between heat flow and current, the material has high strength and durability, so it is widely used. C  Phase change materials Phase change material is a kind of material that can absorb and release a large amount of heat energy, the melting point is usually very stable, when the charge reaches a certain tem...

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The concept of grading: In a fixed requirement environment, When the lithium battery is fully charged, Release of electricity under certain conditions, The amount of power released from the battery at this point is the capacity of the lithium-ion battery. Differentiation of lithium-ion batteries according to capacity, It's grading. Purpose of grading: 1.   Distinguish between capacity-qualified products and capacity-unqualified products. If the capacity meets the requirements, it is a qualified product. If the capacity is lower than the specification, it is a unqualified product. 2.   One of the means of classifying and grouping lithium-ion batteries. Selection of monomers with the same capacity and internal resistance, Such monomers with the same performance form a battery pack. Inconsistency in battery capacity can cause inconsistency in the depth of discharge of each individual cell in the battery pack. Batteries with smaller capacity and poorer performance will reach the full state of charge earlier, causing batteries with large capacity and good performance to fail to reach the full state of charge. Vantage: simple and convenient Disadvantage: The method is a static measurement method, which does not reflect the differences in the actual application of changes and has limitations. Method of grading 1.  Discharge capacity method Lithium-ion batteries are fully charged under certain conditions and then fully discharged at a certain current, Discharge current * time, is the discharge capacity of lithium-ion battery. Advantage: Capable of accurately and comprehensively reflecting the performance of lithium-ion battery discharge capacity, etc. Disadvantage: Longer time, affecting productivity 2.  Charge capacity method Lithium-ion batteries are charged to SOC1 under certain conditions, Then follow a charging method to reach SOC2,Calculate charging capacity between SOC1-SOC2, Compare the above relationship between charging capacity and final capacity of lithium-ion batteries, Estimate the actual discharge capacity of a lithium-ion battery. Advantage: Short time and high productivity Disadvantage: Existence of bias and misjudgement. 3.  Open circuit voltage method Li-ion batteries are charged at constant current to a certain SOC，determine the relationship between open circuit voltage and discharge capacity, discharge capacity deduced from open circuit voltage. Advantage: Short time and high productivity Disadvantage: Low accuracy of judgement, Not suitable for high-precision grading. TOB NEW ENERGY provide Formation And Grading Machine for cylindrical batteries, polymer batteries, and button cell.  Email : tob.amy@tobmachine.com  Skype :amywangbest86  Whatsapp/Phone number :+86 181 2071 5609