Lithium ion battery size stability evaluation method

Abstract

The invention discloses a lithium ion battery size stability evaluation method. According to the method, lithium ion battery size is a suspension system consisting of different substances, componentsin the size do not undergo chemical reaction, stable chemical bonds do not exist, sedimentation is caused along with the time expansion under a standing state, the uniformity of the size is destroyed,the weight of the size with the same volume is changed, the size with the minimum weight is subtracted from the size with the maximum weight to obtain a range value of size change, and the value is divided by the minimum size weight and then multiplied by 100% to obtain a change rate which reflects the difference of the whole size. The method is simple to operate and short in test time, and is capable of rapidly obtaining test results and correctly and objectively reflecting the stability and consistency of lithium ion battery size.

Description

technical field [0001] The invention relates to the technical field of lithium-ion power batteries, in particular to a method for evaluating the stability of lithium-ion battery slurry. Background technique [0002] With the continuous increase of the global population base and the continuous consumption of non-renewable resources (natural gas, oil, coal, etc.), it is imminent to develop renewable and environmentally friendly energy. Lithium-ion batteries have many excellent characteristics, such as high working voltage, high specific energy, wide working temperature range, high specific power, long life, no pollution and small memory effect, etc., making them the best choice for renewable and environmentally friendly energy. The preparation of lithium-ion batteries with excellent performance and high safety performance is an inevitable requirement for the survival and development of the industry, which requires the quality of battery production to be controlled from the sou...

AI Technical Summary

Problems solved by technology

[0004] At present, there are many studies on evaluating the stability of slurry. Patent CN 106124363A mentions a method for measuring the stability of battery slurry: take the prepared positive electrode or negative electrode slurry, and test the viscosity change and rotational speed when the rotational speed changes from small to large. Viscosity changes when changing from large to small, and draw two slurry viscosity variation curves with rotational speed respectively; analyze the coincidence of the two slurry viscosity variation curves with rotational speed, when the coincidence of the two curves is good, it shows that the positive electrode Or the stability of the negative electrode slurry is good, when the coincidence of the two curves is poor, it means that the stability of the positive electrode or negative electrode slurry is poor

Although this method is convenient, it also has its limitations. First of all, there is no selection standard for the speed, and a large number of experiments are required to verify it; secondly, the operation is more complicated and requires higher professional knowledge and skills to operate. For battery production personnel Difficult to operate

Patent CN104880384A discloses a method for evaluating the stability of the positive electrode slurry of a lithium ion battery: the positive electrode slurry is filled in an acid burette, and the slurry is measured from the upper and lower ends of the burette after standing vertically for 1-5 hours , Use a rheometer to measure the shear rate-viscosity curve of the slurry. When the shear rate-viscosity curves of the upper and lower parts of the slurry overlap well, it indicates that the slurry has good stability. On the contrary, it indicates that the slurry is stable. Poor stability

Although this method is simple and quick, it cannot reflect the integrity of the slurry, and the slurry will be stirred during the process of taking the slurry from the acid dropper. The accuracy of the test results needs to be considered

[0005] Patent CN201711330594 discloses a method for evaluating the stability of lithium-ion battery slurry: step S1, weigh the weight of several samplers, and record the numbers respectively; step S2, put a certain amount of configured battery slurry in a container, Place n samplers at the upper, middle, and bottom positions of the container, seal the container and let it stand for A minute; step S3, slowly take a sampler from the upper, middle, and bottom of the container, and wipe the outer wall of the sampler clean Weigh after and along the mouth, and record the weighing data W at each height position 1 Step S4, after the container is sealed and left to stand for B hours, repeat step S3, and record the weighing data W of each height position 2 ; Step S5, after the container is sealed and left to stand for C hours, repeat step S3, and record the weighing data W of each height position 3 , until the sampler is taken out; step S6, constantly repeat step S5, and record each weighing data W of each height position 4 , W 5 …W n , until the sampler is taken out; step S7, according to the weighing data, calculate the weight change rate of the upper, middle and lower parts, if the change rate is not more than 1%, it shows that the slurry stability is good, otherwise, it shows that the slurry stability is poor

This patent requires n samplers to be placed in the slurry. Since the slurry is a suspension system, the micron-scale and nano-scale slurry particles in the slurry will easily agglomerate on the wall of the sampler, which accelerates the agglomeration of the slurry. Shen, when the sampler is taken out, the slurry will be stirred and the state of the slurry will be broken. The test results cannot objectively reflect the stability of the slurry; at the same time, the rate of change in the patent is based on the change in the weight of the slurry at the same position at different time points , it is impossible to determine whether the slurry stability at this time point can continue the coating operation, the timeliness is not good, it is not conducive to production guidance, and affects production efficiency

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