阅读说明：本技术 一种降低锂离子电池石墨负极材料比表面积的方法 (Method for reducing specific surface area of graphite negative electrode material of lithium ion battery ) 是由 彭渊敏 韩峰 韩少峰 杨栋梁 于 2019-10-07 设计创作，主要内容包括：本发明公开了一种降低锂离子电池石墨负极材料比表面积的方法,该方法利用带加热和搅拌的高速包覆釜装置,把制得的石墨负极原型料和低温改性石油沥青同时加入高速包覆釜装置,经过加热高速分散,表面形成包覆层等过程,然后将具有包覆层的负极材料再经过高温炭化处理,最终获得具有低比表面积的石墨负极材料,该方法使用的石墨负极原型料是超高功率电极碎料通过超细粉碎、整形制成。该方法降低了材料的比表面积,大大降低了材料加工成本,提升了材料性能,有效减少正极容量以及电解液损耗,延长锂离子电池使用寿命,具有很好经济价值。(The invention discloses a method for reducing the specific surface area of a graphite cathode material of a lithium ion battery, which comprises the steps of utilizing a high-speed coating kettle device with heating and stirring functions, adding a prepared graphite cathode prototype material and low-temperature modified petroleum asphalt into the high-speed coating kettle device at the same time, carrying out heating high-speed dispersion, forming a coating layer on the surface and the like, and then carrying out high-temperature carbonization treatment on the cathode material with the coating layer to finally obtain the graphite cathode material with the low specific surface area. The method reduces the specific surface area of the material, greatly reduces the material processing cost, improves the material performance, effectively reduces the anode capacity and the electrolyte loss, prolongs the service life of the lithium ion battery, and has good economic value.)

1. A method for reducing the specific surface area of a graphite cathode material of a lithium ion battery is characterized by comprising the following steps:

(1) preparing a graphite cathode prototype material: the method comprises the following steps of crushing coarsely crushed ultrahigh-power graphite electrode crushed aggregates by a CR-800 ultramicro impact mill for the first time, collecting the materials by a cyclone collecting device, shaping by a QX-600 type gap shaping machine, wherein the shaping device is provided with a grading device, removing impurities from graphite cathode materials collected by the grading machine by using a 325-mesh rotary vibrating screen to obtain a raw material, wherein the particle size of the raw material is D50=15-19um, the tap density is 0.78-0.85g/cm, and the specific surface area is 6.5-7.0 square meters/g;

(2) coating treatment of graphite negative electrode raw material: adding a graphite negative electrode prototype material and low-temperature modified petroleum asphalt into a high-speed coating kettle according to the weight ratio of 98-99% to 1-2%, and coating the surface of the graphite negative electrode prototype material;

(3) and (3) carbonization treatment: and (3) carrying out high-temperature carbonization treatment on the graphite cathode material coated in the step (2) at the high temperature of 1200-1500 ℃ to obtain the graphite cathode material with the specific surface area of 2.5-3.0 square meters per gram, the granularity D50=16-20um and the tap density of 0.95-0.98 g/cm.

2. The method as claimed in claim 1, wherein the ultrahigh-power graphite electrode scraps are subjected to thin film chemical mechanical polishing, wherein the ultrahigh-power graphite electrode scraps are subjected to resistivity less than or equal to 5.5uΩ -m, graphitization degree is greater than or equal to 96%, ash content is less than or equal to 0.2%, particle size is 1-5mm, and true density is greater than or equal to 2.24 g/cm during thin film chemical mechanical polishing.

3. The method of claim 1, wherein the low-temperature modified petroleum asphalt has a softening point of 120-150 ℃ and a coking value of 30% or more.

4. The method according to claim 1, wherein the reaction conditions of the step (2) are as follows: heating to 150-250 ℃ at a heating rate of 1-10 ℃/min under the condition of a rotating speed of 30-60 r/min, preheating the graphite cathode prototype material for 30-90min, adding low-temperature modified petroleum asphalt, heating to 350-450 ℃ at a heating rate of 1-10 ℃/min under the condition of a rotating speed of 90-110 r/min, and continuously stirring for 60-180 min.

5. The method as claimed in claim 1, wherein the high speed coating kettle is a coating device with high speed stirring and heating functions, and the highest linear speed can reach: 11m/s, and the maximum use temperature can reach 750 ℃.

6. The high-temperature carbonization according to claim 1, wherein the high-temperature carbonization treatment in the step (3) is a tunnel-type high-temperature carbonization furnace, a graphite crucible is charged, and the carbonization is performed intermittently.

Technical Field

The invention relates to a modification method of a graphite negative electrode material of a lithium battery, belonging to the technical field of lithium ion battery materials.

Background

With the development of lithium ion battery technology, a cathode material is used as one of core materials of the lithium ion battery, and the final performance of the lithium ion battery plays a crucial role. The research of high-performance negative electrode materials becomes one of the most active plates of the current lithium ion power battery, and the performance optimization of the lithium ion power battery needs to be based on the innovative breakthrough of the negative electrode material technology.

In addition, the lithium ion battery is easy to be co-embedded with an organic solvent in the electrolyte, so that a graphite layer of the negative electrode is expanded and peeled off, the electrolyte is further consumed, and the cycle stability of the lithium ion battery is reduced. Aiming at the problems, the specific surface area of the negative electrode material can be further reduced in technical process, and the reversible capacity and the cycle performance of the material are improved.

Disclosure of Invention

The invention aims to provide a method for reducing the specific surface area of a graphite cathode material of a lithium ion battery.

(1) Preparing a graphite cathode prototype material: the method comprises the following steps of crushing coarsely crushed ultrahigh-power graphite electrode crushed aggregates by adopting a CR-800 ultramicro impact mill for the first time, collecting the materials by using a cyclone collecting device, shaping by using a QX-600 type clearance shaping machine, wherein the shaping device is provided with a grading device, removing impurities from graphite cathode materials collected by the grading machine by using a 325-mesh rotary vibrating screen to obtain a prototype material, wherein the particle size of the prototype material is D50=15-19um, the tap density is 0.78-0.85g/cm, the specific surface area is 6.5-7.0 square meters/g, the first coulomb efficiency is 86-88%, and the specific capacity is 335-.

(2) Coating treatment of graphite negative electrode raw material: adding the graphite negative electrode raw material and the low-temperature modified petroleum asphalt into a high-speed coating kettle according to the weight ratio of 98-99% to 1-2%, and coating the surface of the graphite negative electrode raw material.

(3) And (3) carbonization treatment: and (3) carrying out high-temperature carbonization treatment on the graphite cathode material coated in the step (2) at the high temperature of 1200-1500 ℃ to obtain the graphite cathode material with the specific surface area of 2.5-3.0 square meters per gram, the granularity D50=16-20um and the tap density of 0.95-0.98 g/cm.

Furthermore, the resistivity of the ultrahigh-power graphite electrode crushed aggregates is less than or equal to 5.5u omega.m, the graphitization degree is more than or equal to 96%, the ash content is less than or equal to 0.2%, the particle size is 1-5mm, and the true density is more than or equal to 2.24 g/cm for carrying out the thin film seed bearing.

Furthermore, the linear speed of the CR-800 ultrafine impact mill is 50-80m/s, the crushed materials are impacted by using hammers, blades, rods and the like on the high-speed rotating revolving body, and the purpose of ultrafine crushing of the materials is realized by virtue of the violent impact between the materials and the revolving body, the high-speed impact between the materials flying at high speed and the shearing and grinding between the revolving body and a stator or a side wall.

Furthermore, the QX-600 type gap type shaping machine has no crushing function on materials, only changes the shape of the hammerhead of the crushing revolving body, the specification of the gear ring of the equipment cavity and the linear speed of the equipment on the basis of the ultramicro impact mill, and the materials collide and rub in the cavity to achieve the shaping purpose, so that the surface appearance of the materials is more regular, and the surface defects are reduced.

Further, the softening point of the low-temperature modified petroleum asphalt is 120-150 ℃, and the coking value is more than or equal to 30%. The modified asphalt is prepared by using petroleum asphalt as a raw material, common low-temperature petroleum asphalt is subjected to heat treatment, and aromatic hydrocarbon molecules in the asphalt generate hydrogen, methane and water in the thermal polycondensation process. Meanwhile, a part of the original beta resin in the asphalt is converted into secondary alpha resin, a part of benzene solution is converted into beta resin, alpha components are increased, the cohesiveness is increased, and the asphalt is modified, and the asphalt is called modified asphalt.

Further, the reaction conditions of the step (2) are as follows: heating to 150-250 ℃ at a heating rate of 1-10 ℃/min under the condition of a rotating speed of 30-60 r/min, preheating the graphite cathode prototype material for 30-90min, adding low-temperature modified petroleum asphalt, heating to 350-450 ℃ at a heating rate of 1-10 ℃/min under the condition of a rotating speed of 90-110 r/min, and continuously stirring for 60-180 min.

Further, the high-speed coating kettle is a coating device with high-speed stirring and heating functions, and the highest linear speed can reach: 11m/s, and the maximum use temperature can reach 750 ℃. The main structure of the high-speed coating kettle consists of a driving and transmission device, an electric furnace heating device, a kettle body, a dispersing and stirring device and an electric control device.

Further, the high-temperature carbonization treatment in the step (3) adopts a tunnel type high-temperature carbonization furnace, a graphite crucible is used for charging, and the batch carbonization is carried out. After the materials are filled into the crucible according to a certain charging weight, the materials are conveyed into the furnace body by the automatic conveying device to be heated and carbonized, the carbonization temperature is 1200 and 1500 ℃, and nitrogen is introduced for protective cooling after carbonization, and then the materials are discharged. The purpose of high-temperature carbonization is to remove light components in the medium-temperature modified petroleum asphalt, because the asphalt is a hydrocarbon, after the carbonization temperature of 1000 ℃ is reached, most of the light components and S, N, O elements are discharged in the form of flue gas, and finally, a layer of carbon elements is formed on the surface of the original cathode material.

The ultrahigh-power graphite electrode is a high-temperature conductive material used for electric furnace steelmaking, in the process of manufacturing the graphite electrode, the graphitized electrode needs to be machined to meet the size requirement of the electrode, the particle crushed aggregates generated by cutting are raw materials used for the graphite cathode prototype material, the material is low in price and wide in source, and the manufactured lithium ion battery cathode material is directly used as the cathode material without graphitization after being coated and carbonized.

The invention has the beneficial effects that: the lithium ion battery cathode material prepared by the invention does not need graphitization processing, has the advantages of low specific surface area, higher specific capacity, excellent cycle performance and the like, overcomes the defects of the lithium ion battery cathode material produced by the traditional graphite electrode, can greatly improve the energy density and the cycle performance, has the specific capacity of not less than 345mAh/g and the cycle life of not less than 800 times.

Drawings

FIG. 1 is a schematic structural diagram of a high-speed coating kettle according to the present invention.

In the figure: 1-main shaft driving motor, 2-gear reducer, 3-chain type coupler, 4-high speed frame, 5-205 type mechanical seal, 6-manhole, 7-main shaft support frame, 8-temperature measuring K type thermocouple, 9-electric furnace junction box, 10-flap paddle type dispersing blade, 11-stirring main shaft, 12, heating wire, 13-refractory brick, 14-electric furnace shell, 15-discharge port, 16-smoke outlet, 17-feed port, 18-nitrogen charging port, 19-exhaust port, 20-kettle top thermocouple mounting port, 21-kettle body mounting lug seat, 22-electric control device, 23-upper sealing head, 24-sealing head flange, 25-straight cylinder part and 26-cone part.

Fig. 2 is an SEM image of a graphite negative electrode prototype in example 1.

Fig. 3 is an SEM image of graphite anode prototype coating carbonized according to example 1.

Fig. 4 is a simulated battery charge-discharge curve of sample a and the negative electrode prototype in example 2.

Fig. 5 is a graph comparing cycle data for sample a and negative electrode prototype in example 2.

Fig. 6 is a comparison of the disassembled pictures after cycling of 18650 lithium ion batteries made from sample a and the negative electrode prototype of example 2.

Detailed Description

The invention is further illustrated with reference to the following figures and examples.

The high-speed coating kettle is a coating device with high-speed stirring and heating functions, and the main structure of the high-speed coating kettle consists of a driving and transmission device, an electric furnace heating device, a kettle body, a dispersing and stirring device and an electric control device, as shown in figure 1.

Wherein the drive and transmission device: the spindle driving motor with the serial number of 1 is a spindle driving motor with the model number as follows: the power of the YB3-280S-4 type explosion-proof motor is 75kw, the motor is connected with a serial number 2 gear reducer, the model of the reducer is RF164-14.43-75kw, the speed ratio of the gear reducer is 14.43, the highest output rotating speed is 104r/min, and the highest linear speed can reach: 10.88m/s, gear reducer output shaft and stirring main shaft "11" use chain type shaft coupling "3" to connect, chain type shaft coupling model: KC-10020. Main shaft driving motor "1" and gear reducer "2" are installed on high-speed frame "4" as a whole, and mechanical seal "5" for the cauldron, the model: 205, which is used to ensure the sealing between the rotating shaft and the machine body, and is a device for preventing fluid leakage, which is formed by at least a pair of devices which are perpendicular to the end surface of the rotating shaft, keep fitting and relatively slide under the action of fluid pressure and the elastic force of the compensation mechanism and the cooperation of auxiliary sealing.

The heating device of the electric furnace comprises a heating wire, refractory bricks and an electric furnace shell, wherein the heating wire is close to the surface of a kettle body, the diameter of the heating wire is 5mm and is spiral, the heating wire is made of Cr15Ni60 alloy, the maximum use temperature of the element is 1150 ℃, the melting point is 1390 ℃, the heating wire is arranged on a refractory high-alumina brick 13, the high-alumina brick is an aluminum silicate refractory material with the Al2O3 content of more than 48 percent, the aluminum silicate refractory material is generally divided into three types, namely I and the like, wherein the Al2O3 content is more than or equal to 75 percent, II and the like, the Al2O3 content is 60 percent, III and the like, the Al2O3 content is 55 percent and ~ percent, the electric furnace is made of three-level high-alumina refractory bricks, the refractoriness is more than 1750 ℃, the refractoriness under load of 0.2MPA is 1420 ℃, the volume density is more than 2.3/cm, high-temperature resistant cement is used for being laid on the upper end of the furnace shell 14, a junction box is arranged at the right side of the heating electric furnace, a 380V power supply required for heating is connected to the electric furnace 9 from the outside, the electric furnace is connected to the upper end of the electric furnace, the lower end of the electric furnace is connected to the temperature of the.

Wherein the cauldron body comprises upper cover "23", cylinder type straight section of thick bamboo portion "25" and cone portion "26", upper cover and straight section of thick bamboo portion are connected by upper cover flange "24", straight section of thick bamboo portion maximum diameter 2.0 meters, whole volume is 4000L, according to the material that loose loading density 0.5 g/cm was taken by the year, 1000kg of disposable throwable material, upper cover and straight section of thick bamboo portion are connected with the flange, manhole "6", exhaust port "16", feed inlet "17", nitrogen filling gas port "18", exhaust hole "19", cauldron top thermocouple installing port "20", manhole "6" has been distributed to the upper cover punishment in the manhole can get into the cauldron through the manhole and carry out clearance maintenance or maintenance to the cauldron, cauldron top thermocouple installing port is used for installing the K type thermocouple, the thermocouple directly inserts in the cauldron material mouth, can measure cauldron atmosphere temperature, the cone bottom is the blow-off "15".

The dispersing and stirring device is composed of a stirring main shaft '11' and a flap paddle type dispersing blade '10', a main shaft supporting frame is arranged at the middle section of the stirring main shaft to ensure the stability of the stirring shaft during high-speed operation, and the stirrer belongs to mixed flow type dispersing and has a good material dispersing effect.

Wherein the electric control device comprises a temperature control instrument, a spindle motor frequency converter, an electric heating silicon controlled rectifier, a PLC and a touch display screen, after the control cabinet is started, operation parameters are edited on the touch screen, 5 sections of operation parameters can be edited, the equipment can automatically operate according to the set parameters under an automatic mode, when the actual temperature does not reach a set value, the temperature control instrument transmits signals to the electric heating silicon controlled rectifier, the silicon controlled rectifier can continuously output current, a heating wire heats until the temperature reaches the set value, when the temperature reaches the set value, the output current of the silicon controlled rectifier is gradually reduced until the output current is zero, during heating, the PLC can transmit signals to the spindle motor frequency converter, the frequency converter can operate according to the set rotating speed, the touch display screen can display the high-speed coating furnace temperature and the rotating speed of the spindle motor in real time, when the furnace temperature exceeds the set safe temperature, the control cabinet automatically alarms and stops heating until, when the set program is completely operated, the equipment stops, the initial rotation state is recovered, meanwhile, the control cabinet has a manual mode, the main shaft motor can be switched to rotate forward and backward in the manual mode, the rotating speed of the main shaft motor can be manually adjusted, the electric furnace can be manually turned on and off for heating, pneumatic ball valves are arranged on the smoke outlet 16, the feed inlet 17 and the exhaust hole 19, and the switch of the valve can be controlled by using a knob on the control cabinet.