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A method for improving cycle life of lithium iron phosphate battery

A lithium iron phosphate battery and lithium iron phosphate technology, applied in battery electrodes, secondary batteries, circuits, etc., can solve the problems of unfavorable lithium battery cycle life, poor battery structure stability, and weakened oxidation capacity, etc., to achieve Effects of improving shelf performance and cycle stability, improving alkaline environment and capacity, and improving cycle life

Active Publication Date: 2016-03-16
LUOYANG YUEXING NEW ENERGY TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

Or improve the cycle life of lithium batteries by adding weakly acidic or weakly alkaline substances in the slurry, such as patent CN101841028A discloses a method for improving the cycle life of batteries, mainly by adding lithium carbonate to lithium iron phosphate slurry Weakly alkaline substances are used to improve the cycle life of the battery, but lithium carbonate is unstable in the slurry and causes the stability of the lithium battery to deteriorate during the later cycle, and at the same time due to the Fe in lithium iron phosphate 2 The redox ability is different under different alkaline conditions, resulting in different chemical stability of lithium iron phosphate. If the pH value is too high, that is, if the alkalinity is too high, it will cause Fe 2+ If the oxidizing ability is too strong, it is easy to cause the decomposition of the electrolyte or the micro-corrosion of the aluminum foil, and thus cause the stability of the battery structure to deteriorate and the internal resistance to increase; the pH value is too low, that is, the alkalinity is too low, and its Fe 2+ The oxidation ability of Fe is significantly weakened, resulting in Fe 2+ In the process of charging and discharging, the oxidation-reduction ability becomes weak, which is not conducive to the intercalation of lithium ions, and is not conducive to improving the cycle life of lithium batteries.
[0005] Selecting a weakly acidic or weakly alkaline substance with strong chemical stability and adding it to lithium iron phosphate slurry to prepare a slurry with a certain pH value is one of the methods to improve the cycle life of lithium iron phosphate batteries, but currently The technology does not meet the requirements

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  • A method for improving cycle life of lithium iron phosphate battery

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0027] (1) Weigh 1666 grams of LA132 water-based binder with a mass concentration of 15% and add it to 500 grams of double-distilled water, stir at 25r / min for 1 hour, then add 250 grams of carbon black and mix it at 45~5000r / min Stir at a rotating speed for 2 hours, then add 1,500 grams of lithium iron phosphate and 500 grams of twice distilled water in three batches, and stir for 4 hours in each batch at a rotating speed of 45~5000r / min to obtain lithium iron phosphate slurry. In order to improve the purity, the water that has been distilled twice is called double distilled water, without further explanation.

[0028] (2) Add 450 grams of LiOH solution with a mass concentration of 10% to the lithium iron phosphate slurry and stir for 1 hour to obtain a lithium iron phosphate positive electrode slurry, and the pH value of the lithium iron phosphate positive electrode slurry is controlled in the range of 8.5 to 9 .

[0029] (3) At a coating temperature of 100°C and a coating...

Embodiment 2

[0031] The first step is the same as (1) in Example 1.

[0032] (2) In the lithium iron phosphate slurry, adding 450 grams of Li with a mass concentration of 10% 2 CO 3 The solution was stirred for 1 hour to obtain a lithium iron phosphate positive electrode slurry, and the pH value of the lithium iron phosphate positive electrode slurry was controlled in the range of 8.5-9.

[0033] (3) At a coating temperature of 90°C and a coating speed of 3m / s, uniformly coat the lithium iron phosphate cathode slurry with a pH value of 8.5-9 on the aluminum foil, and then dry it at 75-85°C 12 to 24 hours, after drying, roll pressing under a pressure of 5 to 10 MPa to obtain a positive electrode sheet for a lithium iron phosphate battery.

Embodiment 3

[0035] The first step is the same as (1) in Example 1.

[0036] (2) Adding 450 grams of mass concentration in the lithium iron phosphate slurry is 5% C 2 h 5 COOH solution and stirred for 1 hour to obtain lithium iron phosphate positive electrode slurry, the pH value of the lithium iron phosphate positive electrode slurry is controlled in the range of 8.5-9.

[0037] (3) At a coating temperature of 110°C and a coating speed of 1.5m / s, evenly coat the lithium iron phosphate positive electrode slurry with a pH value of 8.5-9 on the aluminum foil, and then coat it under the condition of 75-85°C Dry for 12 to 24 hours, and then perform rolling under a pressure of 5 to 10 MPa after drying to obtain a positive electrode sheet for a lithium iron phosphate battery.

[0038] The positive electrode sheet obtained in the above-mentioned Examples 1 to 3 is used as the positive electrode material, artificial graphite is used as the negative electrode material, and the volume ratio of 1:1...

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PUM

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Abstract

A method for improving the cycle life of a lithium iron phosphate battery, comprising the preparation of lithium iron phosphate slurry, the preparation of lithium iron phosphate positive electrode slurry and the preparation of positive electrode sheet, the lithium iron phosphate positive electrode slurry has a pH value of 8.5 Under the alkaline condition of ~9, Fe2+ has a relatively stable redox ability, which significantly improves the stability and cycle life of the interlayer structure of lithium iron phosphate batteries, and plays a positive role in the consistency of lithium iron phosphate batteries. The coating temperature and coating speed can ensure that the water in the lithium iron phosphate positive electrode slurry is fully evaporated, preventing the positive electrode from being corroded in the high-temperature and high-alkaline aqueous solution, and the prepared positive electrode has good chemical stability. It can improve the cycle life of the lithium iron phosphate battery, especially improve the alkaline environment and capacity of the lithium iron phosphate positive electrode slurry, thereby improving the shelf performance and cycle stability of the lithium iron phosphate battery. The process is simple, the cost is low, and the effect is remarkable. It is suitable for Mass production.

Description

technical field [0001] The invention belongs to the technical field of lithium ion batteries, and in particular relates to a method for improving the cycle life of a lithium iron phosphate battery. Background technique [0002] Lithium iron phosphate LiFePO 4 The material has the advantages of low cost, good environmental compatibility, high specific capacity, good stability, etc., and is a cathode material for lithium-ion batteries with great application potential. However, the production cost of lithium iron phosphate battery is relatively high, which limits its wide application in the field of electric vehicles and their energy storage. [0003] At present, the method of reducing the production cost of lithium iron phosphate battery is to reduce the price of lithium iron phosphate through process improvement, or indirectly reduce the production cost of the battery by improving the cycle life of lithium iron phosphate battery. [0004] In most cases, the cycle life of li...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H01M4/1397H01M4/58
CPCH01M4/1397H01M4/5825H01M10/0525Y02E60/10
Inventor 徐军红王进军
Owner LUOYANG YUEXING NEW ENERGY TECH