Lithium iron phosphate battery gradient concentration difference injection process

Abstract

The application discloses a lithium iron phosphate battery gradient concentration difference liquid injection process, simulates and analyzes to determine the consumption of lithium ions in each part during formation, divides the lithium battery into L1-Ln areas from bottom to top, calculates the consumption of lithium ions Q1-Qn corresponding to each area, then calculates the concentration S1-Sn of electrolyte corresponding to each area, respectively configures the electrolyte with the concentration corresponding to each area, each area is configured with first electrolyte and second electrolyte, the second electrolyte increases thickener compared with the first electrolyte, and the first electrolyte is added first and then the second electrolyte is added in each area in turn until the electrolyte injection is completed. The application improves the cycle life of the lithium battery by more than 20%, greatly delays the fusion speed of the electrolyte in the upper and lower areas through the difference in the consistency of the electrolyte, and increases the physical barrier formed between the upper and lower electrolyte by the silicon dioxide powder layer, so that the effect of gradient concentration injection is ensured.

Description

TECHNICAL FIELD

[0001] The application relates to a lithium battery liquid injection process, in particular to a lithium iron phosphate battery gradient concentration difference liquid injection process and belongs to the technical field of lithium batteries. BACKGROUND

[0002] When lithium batteries are produced, the anode and the cathode are wound into a roll and a shell is completed and sleeved, and then electrolyte needs to be injected into the lithium battery shell, in the prior art, the electrolyte injected into the lithium battery has a unique concentration, the electrolyte is configured according to the consumption of lithium ions in the whole lithium battery through theoretical calculation, and the electrolyte with the configured concentration is directly injected into the shell through a liquid injection device of the lithium battery. However, it is found in research that the consumption of lithium ions in each region in the lithium battery is not equal when the lithium battery is formed, and the electrolyte with the unique concentration causes lithium ions to be in excess in some regions and insufficient in some regions, so that the cycle life of the lithium battery after formation is reduced. SUMMARY

[0003] The application aims to solve the technical problem of providing a lithium iron phosphate battery gradient concentration difference liquid injection process and improving the cycle life of the lithium battery.

[0004] To solve the above technical problem, the technical scheme adopted by the application is as follows:

[0005] A lithium iron phosphate battery gradient concentration difference liquid injection process, characterized by comprising the following steps:

[0006] S1, sampling products, and simulating and analyzing the consumption of lithium ions in each part of the lithium battery during formation of the products, to determine the consumption of lithium ions in each part during formation;

[0007] S2, dividing the lithium battery into L1-Ln regions from bottom to top, and calculating the consumption Q1-Qn of lithium ions in each region in the L1-Ln regions according to the consumption of lithium ions in each part in the simulation result;

[0008] S3, calculating the concentration S1-Sn of electrolyte corresponding to each region in the L1-Ln regions according to the consumption Q1-Qn of lithium ions in the L1-Ln regions;

[0009] S4, configuring electrolyte with the S1-Sn concentration corresponding to each region, and configuring first electrolyte and second electrolyte in each region, the second electrolyte being increased in thickener compared with the first electrolyte;

[0010] S5, first injecting the first electrolyte corresponding to the L1 region into the L1 region, then injecting the second electrolyte corresponding to the L1 region until the L1 region is filled, then first injecting the first electrolyte corresponding to the L2 region into the L2 region, then injecting the third electrolyte corresponding to the L2 region until the L2 region is filled, and using the same way to inject the first electrolyte and the second electrolyte corresponding to each region in L3-Ln region in turn, to complete the lithium battery gradient concentration injection.

[0011] Further, in the step S3, the concentration S1-Sn of the electrolyte corresponding to each region in L1-Ln region is calculated as follows: Sm=Qm / (Hm*A), wherein A is the bottom area of the lithium ion battery, Hm is the height of the mth region Lm, 1≤m≤n, and Qm is the consumption amount of lithium ions corresponding to the region Lm.

[0012] Further, in the step S3, the first electrolyte contains organic solvent, lithium salt, vinylene carbonate, succinic anhydride and triallyl isocyanurate, and the second electrolyte contains organic solvent, lithium salt, vinylene carbonate, succinic anhydride, triallyl isocyanurate and thickening agent.

[0013] Further, the organic solvent uses one or a combination of several of dimethyl carbonate, ethyl acetate, ethyl propionate and propylene carbonate.

[0014] Further, the lithium salt uses lithium hexafluorophosphate and / or lithium bisfluorosulfonylimide.

[0015] Further, the thickening agent uses one or a combination of several of polyvinyl alcohol, polyacrylamide and polyethylene glycol.

[0016] Further, in the step S5, the first electrolyte and the second electrolyte are injected into the lithium battery shell by a needle tube injection, the needle tube outlet is located 1-3mm above the injection liquid level, and the lithium battery is installed on a rotating clamp and rotates synchronously when the needle tube is injected.

[0017] Further, a silica powder spray pipe is provided beside the needle tube, and a layer of silica powder is sprayed between the first electrolyte and the second electrolyte.

[0018] Compared with the prior art, the present application has the following advantages and effects: the present application obtains lithium ion consumption of each part of the lithium battery through simulation, then divides the regions and allocates electrolyte with different concentrations in different regions, so that the lithium ion consumption of each region can match the lithium battery formation, and the cycle life of the lithium battery is improved by more than 20%; the present application configures two kinds of electrolyte in each region, the consistency of the second electrolyte is higher than that of the first electrolyte, thereby forming physical stratification, which can greatly delay the fusion speed of the electrolyte in the upper and lower regions; the present application increases the silicon dioxide powder layer to form a physical barrier between the upper and lower electrolyte layers, since the consistency of the organic solvent of the electrolyte itself is relatively high, and the surface tension is relatively large, after adding the silicon dioxide powder, the powder adheres to the surface between the two electrolyte layers, and the physical separation effect is formed through the tension of the two electrolyte layers. DETAILED DESCRIPTION

[0019] In order to clearly and completely describe the technical solutions adopted by the present application to achieve the predetermined technical purposes, the technical solutions in the embodiments of the present application are described below. Obviously, the described embodiments are only part of the embodiments of the present application, not all embodiments, and the technical means or technical features in the embodiments of the present application can be replaced without creative labor. The present application will be described in detail below with reference to the embodiments.

[0020] The lithium iron phosphate battery gradient concentration difference injection process of the present application comprises the following steps:

[0021] S1, sample the product, and simulate and analyze the lithium ion consumption of each part inside the lithium battery during formation, to determine the lithium ion consumption of each part during formation. Through specific test data and combined with software simulation, the theoretical consumption of lithium ions in each part of the lithium battery is obtained.

[0022] S2, divide the lithium battery into L1-Ln regions from bottom to top, and calculate the lithium ion consumption Q1-Qn of each region in L1-Ln region according to the simulation results. Since the software simulation result is a small region value, we consider that the lithium battery is divided into L1-Ln regions, and the lithium ion consumption of each region can be obtained by adding the same region value in each region.

[0023] S3, calculate the concentration S1-Sn of the electrolyte corresponding to each region in L1-Ln region according to the lithium ion consumption Q1-Qn of L1-Ln region.

[0024] The concentration S1-Sn of the electrolyte corresponding to each of the L1-Ln regions is calculated as follows: Sm=Qm / (Hm*A), wherein A is the bottom area of the lithium ion battery, Hm is the height of the mth region Lm, 1<=m<=n, and Qm is the consumption amount of lithium ions corresponding to the region Lm.

[0025] The first electrolyte comprises an organic solvent, a lithium salt, vinylene carbonate, succinic anhydride and triallyl isocyanurate, and the second electrolyte comprises an organic solvent, a lithium salt, vinylene carbonate, succinic anhydride, triallyl isocyanurate and a thickening agent. The total concentration of the lithium salt in the first electrolyte is 1.05-1.35 mol / L, the addition amount of the vinylene carbonate accounts for 1-3% of the total mass of the electrolyte, the addition amount of the succinic anhydride accounts for 0.8-1.6% of the total mass of the electrolyte, the addition amount of the triallyl isocyanurate accounts for 1-1.5% of the total mass of the electrolyte, and the addition amount of the thickening agent accounts for 1.5-4% of the total mass of the electrolyte.

[0026] The organic solvent is one or a combination of several of dimethyl carbonate, ethyl acetate, ethyl propionate and propylene carbonate. The lithium salt is lithium hexafluorophosphate and / or lithium bisfluorosulfonylimide. The thickening agent is one or a combination of several of polyvinyl alcohol, polyacrylamide and polyethylene glycol.

[0027] S4, respectively configure the electrolyte with the S1-Sn concentration corresponding to the L1-Ln regions, and each region is configured with the first electrolyte and the second electrolyte, and the second electrolyte has a thickening agent added compared with the first electrolyte.

[0028] S5, first inject the first electrolyte corresponding to the L1 region into the L1 region, then inject the second electrolyte corresponding to the L1 region until the L1 region is filled, then inject the first electrolyte corresponding to the L2 region into the L2 region, then inject the third electrolyte corresponding to the L2 region until the L2 region is filled, and in the same way, inject the first electrolyte and the second electrolyte corresponding to each region into the L3-Ln region in sequence, to complete the gradient concentration injection of the lithium battery.

[0029] The first electrolyte and the second electrolyte are injected into the lithium battery shell through a needle tube injection, the needle tube outlet is located 1-3 mm above the injection liquid level, and the lithium battery is mounted on a rotating clamp and rotated synchronously when the needle tube is injected. A silica powder nozzle is arranged beside the needle tube, and a layer of silica powder is sprayed between the first electrolyte and the second electrolyte.

[0030] The present application can match the lithium ion consumption of each area with the lithium battery formation, and improve the cycle life of the lithium battery by more than 20%. Two kinds of electrolyte are configured in each area, and the consistency of the second electrolyte is higher than that of the first electrolyte, so as to form physical stratification, which can greatly delay the fusion speed of the electrolyte in the upper and lower areas. The present application increases the silicon dioxide powder layer to form a physical barrier between the upper and lower electrolyte layers. Since the consistency of the organic solvent of the electrolyte itself is relatively high, and the external surface tension is relatively large, after the addition of the silicon dioxide powder, the powder adheres to the surface between the two electrolyte layers, and the tension of the two electrolyte layers forms a physical separation effect.

[0031] The above is only a preferred embodiment of the present application, and does not limit the present application in any form. Although the present application has been disclosed as above, it is not intended to limit the present application. Any person skilled in the art can make some changes or modifications to the above disclosed technical content without departing from the technical solution of the present application, and the equivalent embodiments with equivalent changes are equivalent. Any simple modification, equivalent replacement and improvement of the above embodiments, as long as it does not deviate from the technical solution of the present application, is within the scope of protection of the present application.

Claims

1. A tiered concentration differential electrolyte injection process for lithium iron phosphate batteries, characterized in that... Includes the following steps: S1. Sample the product and perform simulation analysis on the consumption of lithium ions in each part of the lithium battery during the formation of the product to determine the amount of lithium ions consumed in each part during the formation. S2. Divide the lithium battery into regions L1-Ln from bottom to top, and calculate the lithium ion consumption Q1-Qn of each region in L1-Ln based on the lithium ion consumption of each part in the simulation results. S3. Calculate the electrolyte concentration S1-Sn for each region in the L1-Ln region based on the lithium ion consumption Q1-Qn in the L1-Ln region. S4. Prepare electrolytes with concentrations of S1-Sn corresponding to the L1-Ln regions respectively. Prepare a first electrolyte and a second electrolyte for each region. The second electrolyte contains a thickener compared to the first electrolyte. S5. First, inject the first electrolyte corresponding to region L1 into region L1, then inject the second electrolyte corresponding to region L1 until region L1 is full. Then, first inject the first electrolyte corresponding to region L2 into region L2, then inject the third electrolyte corresponding to region L2 until region L2 is full. In the same way, inject the first electrolyte and the second electrolyte corresponding to each region into regions L3-Ln in sequence to complete the stepwise concentration injection of lithium battery.

2. The lithium iron phosphate battery cascade concentration differential electrolyte injection process according to claim 1, characterized in that: In step S3, the concentration of electrolyte S1-Sn corresponding to each region in the L1-Ln region is calculated as follows: Sm=Qm / (Hm*A), where A is the bottom area of ​​the lithium-ion battery, Hm is the height of the m-th region Lm, 1≤m≤n, and Qm is the amount of lithium ions consumed corresponding to region Lm.

3. The lithium iron phosphate battery cascade concentration differential electrolyte injection process according to claim 1, characterized in that: In step S3, the first electrolyte contains an organic solvent, a lithium salt, vinylene carbonate, succinic anhydride, and triallyl isocyanurate, and the second electrolyte contains an organic solvent, a lithium salt, vinylene carbonate, succinic anhydride, triallyl isocyanurate, and a thickener.

4. The lithium iron phosphate battery cascade concentration differential electrolyte injection process according to claim 3, characterized in that: The organic solvent is one or a combination of several of dimethyl carbonate, ethyl acetate, ethyl propionate, and propylene carbonate.

5. The lithium iron phosphate battery cascade concentration differential electrolyte injection process according to claim 3, characterized in that: The lithium salt is lithium hexafluorophosphate and / or lithium bisfluorosulfonylimide.

6. The lithium iron phosphate battery cascade concentration differential electrolyte injection process according to claim 3, characterized in that: The thickener is one or a combination of polyvinyl alcohol, polyacrylamide and polyethylene glycol.

7. The lithium iron phosphate battery cascade concentration differential electrolyte injection process according to claim 1, characterized in that: In step S5, the first electrolyte and the second electrolyte are injected into the lithium battery casing using a syringe. The syringe outlet is located 1-3 mm above the liquid surface. The lithium battery is mounted on a rotating fixture and rotates synchronously during the injection.

8. The lithium iron phosphate battery cascade concentration differential electrolyte injection process according to claim 7, characterized in that: A silica powder spray nozzle is provided next to the needle, and a layer of silica powder is sprayed between the first electrolyte and the second electrolyte.