CN108183191B - A kind of porous geolith-coated non-woven lithium-ion battery separator and preparation method thereof - Google Patents

Abstract

The invention relates to a porous stone-coated non-woven lithium-ion battery diaphragm and a preparation method thereof, belonging to the field of diaphragm materials. The method firstly prepares a porous ground stone powder with a through hole and a pore size in the range of 0.1-1 μm, and then uses the powder as a coating material, and mixes it with a binder, a modifier and water to form a coating slurry Body, and then coated on the surface of PET non-woven fabric by dipping method to make a composite separator for lithium-ion batteries. This method uses the unique pore structure characteristics of porous dickite to construct a uniform macroporous structure on the surface of the PET non-woven fabric to increase the porosity of the separator; utilizes the good affinity between the functional groups on the surface of dickite and the electrolyte to improve the composite separator. Wettability to the electrolyte, and reduce the internal resistance of the battery, thereby improving the charge-discharge cycle stability of the lithium-ion battery. The preparation method described in the invention is simple, has low equipment requirements, low raw material cost, and has strong market competitiveness.

Description

A kind of porous geolith-coated non-woven lithium-ion battery separator and preparation method thereof

Technical field:

The invention belongs to the technical field of lithium-ion battery diaphragms, and relates to a high-temperature-resistant, power-type lithium-ion battery diaphragm suitable for high-current charging and discharging and a preparation method thereof.

Background technique:

With the rapid development of power vehicles, batteries will become the core of future development, and the diaphragm as a core component of batteries is ushering in a new round of development peak. The diaphragm used in the power lithium-ion battery is obviously different from the ordinary lithium-ion battery diaphragm. The former provides power for vehicles such as vehicles and needs to provide higher voltage, greater power and more electricity. Therefore, the diaphragm is proposed higher requirements. For example, the power battery separator should have higher heat resistance, greater air permeability, and better safety performance. At present, commercial lithium battery separator materials are mainly porous polyolefins such as polyethylene (PE), polypropylene/polyethylene (PP/PE) films, etc. Although polyolefin separators have many advantages for lithium-ion batteries, polyolefins The high-temperature shrinkage of the film and the poor wettability of the electrolyte are only barely used in power lithium-ion batteries. Therefore, the development of new diaphragm products suitable for power lithium-ion batteries has become an urgent task for the development of electric vehicles.

Due to its good high temperature resistance, PET non-woven fabric has become one of the lithium-ion battery separator materials that are currently being researched and developed. However, the large pore structure size of PET non-woven fabric is not conducive to the insulation of positive and negative electrodes and the retention of electrolyte. Therefore, before using it as a lithium-ion battery separator, compound modification is required to control the pore size of the non-woven separator. Commonly used methods include nanoparticle modified non-woven diaphragm, microporous coating coated modified non-woven diaphragm, and electrospinning diaphragm. The nanoparticle-filled non-woven separator can effectively improve the pore structure characteristics of the non-woven separator and improve the safety performance of the battery. The most typical of this type of diaphragm is Degussa's Separion ceramic membrane. Degussa Company pointed out in the patent US20050255769A1 that using orthosilicate or titanium tetraisopropoxide as a silicon source or a titanium source, a SiO ₂ or TiO ₂ gel was generated through a sol-gel process, and mixed with nano-Al ₂ O ₃ The mixture is made into a slurry, coated on the surface of a PET non-woven fabric substrate, and after curing, hot rolling, and drying, a new type of lithium-ion battery separator with improved cycleability and temperature resistance can be prepared. US Patent US6447958BI also reported a method for preparing a composite diaphragm. Aramid fiber solution and nano Al ₂ O ₃ particles are mixed and pulped and coated on PET non-woven fabric, and then polyethylene wax is coated on the surface of the above film to prepare a composite battery with shutdown performance and good thermal stability diaphragm. In Chinese patent CN206401415U, Zhou Yiping reported a power lithium-ion battery diaphragm, using PET non-woven fabric as the base material, inorganic oxide as the coating, and PVDF as the covering layer, which realizes the control of the diaphragm pore size between several hundred nanometers , and has a certain moisturizing function.

The coating of inorganic nanoparticles can effectively modify the pore structure of PET non-woven fabric, reduce the pore size of the diaphragm, improve the insulation of the positive and negative electrodes of the diaphragm, and improve the thermal stability of the non-woven diaphragm. But at the same time, the micropore size of the nanoparticle coating structure is too small, the porosity is low, and the liquid absorption capacity is insufficient, which limits the further improvement of the lithium ion mobility, which is not conducive to the reduction of the internal resistance of the battery and the high current charge and discharge of the battery. At the same time, the use of nano fillers also increases the cost of the product. Therefore, it has become a solution to use PET non-woven fabric as a matrix to find new inorganic fillers and prepare composite non-woven lithium-ion battery separators with larger pore size, higher porosity, higher liquid retention rate, and higher thermal stability. A key issue in battery safety.

The chemical formula of dickite is Al ₄ [Si ₄ O ₁₀ ](OH) ₈ , which is a 1:1 layered aluminosilicate mineral, that is, the structural unit layer consists of a layer of silicon-oxygen tetrahedron and a layer of aluminum-oxygen tetrahedron. Octahedral layers. Due to the relatively weak force between the structural unit layers, the dickite flakes can be peeled off after organic small molecule intercalation-removal treatment. Under the action of a specific oxidant (such as potassium chlorate), small organic molecules (such as urea ) removal can lead to the formation of dickite pore structure, that is, the formation of a through-hole porous structure with a pore size of 0.1-1 μm. If dickite with a porous structure can be used as a coating material for PET non-woven fabrics, it is expected to utilize the unique porous penetration of dickite to construct large pores and well-developed channels in the interior and surface of the non-woven fabric matrix. , Li-ion diffusion channels with high porosity. In addition, the surface of the dickite unit layer is rich in functional groups, which has good adaptability to both aqueous electrolytes and organic electrolytes, and can improve the wettability of the separator to different electrolytes, thereby reducing the battery impedance and improving the rate performance of the battery. cycle performance. At the same time, the non-combustible properties of dickite will further improve the thermal stability of PET non-woven fabrics and improve the safety of the separator.

The unique structural characteristics of matrix porous dikeite and its application prospects in the field of lithium-ion battery separators. The invention proposes a method for preparing a novel lithium-ion battery diaphragm by using porous ground stone as a filler to coat the surface of a PET non-woven fabric substrate. Cycling stability during charge and discharge.

Invention content:

The purpose of the present invention is to solve the problems such as too small pore size, low porosity, and insufficient liquid absorption of the current coated lithium-ion battery diaphragm, using dickite as raw material, using urea and potassium chlorate to treat dickite , so that the dickite obtains the porous structure characteristics, and the porous dickite is used as a coating material, coated on the surface of the PET non-woven substrate, and the preparation can improve the porosity and wettability of the separator, reduce the internal resistance of the battery, and improve the battery charge. Composite separator for lithium-ion batteries with discharge cycle stability.

The present invention is achieved through the following technical solutions:

The preparation of porous ground calcite-coated PET non-woven lithium-ion battery diaphragm comprises the following steps:

a. Preparation of porous dickite

Dickite and a certain proportion of urea are pulverized in a pulverizer for 5 to 20 minutes, so that the particle size is less than 270 mesh, and the mass of urea is 10 to 25 wt% of the dickite mass. The mixture is placed in an open glass container and placed in a microwave oven. Heat it on medium-high heat for 10-20 minutes, and then put it in an oven at 70°C for 50 hours. Then mix and grind the mixture with potassium chlorate for 40 minutes, the consumption of potassium chlorate is 4% of dickite mass. Finally, the mixture mixed with potassium chlorate was put into an electric furnace at 550° C. for 15 seconds and calcined to obtain a porous stone powder.

b. Preparation of Porous Dictite/PET Separator

After uniformly mixing porous ground stone with binder, water, and modifier in a mass ratio of 60-80:33-13:5:2, the coating slurry is obtained by stirring in a homogenizer for 1-2 hours , and then immerse the PET non-woven fabric in the coating slurry for 30 minutes, and then take it out and dry it in a vacuum oven at 40° C. to obtain a porous stone-coated PET non-woven membrane.

The above-mentioned dickite is dickite produced in Changbai County, Jilin Province, the content of other siliceous impurities is less than 5%, and the dickite crystallization index Hinckley index value is greater than 1; the binder is LA132 (LA type water-based electrode binder) or a mixture of LA132 and SBR (styrene-butadiene rubber); the modifier is a silane coupling agent DL171.

Beneficial effects: the present invention uses dickite with a porous structure as the coating raw material and PET non-woven fabric as the base film to prepare a porous dickite/PET diaphragm, which is composited with a large number of reported nano-ceramic particles coated non-woven fabrics The pore-forming mechanism of the membrane is different. The latter uses the gaps formed by stacking a large number of nanoparticles on the surface of the non-woven fabric as the pores for the diaphragm to transmit lithium ions. The rapid passage of ions has a high resistance. The former utilizes the macroporous structure of the porous ground stone (pore size 0.1-1 μm) as a channel for the diaphragm to transmit lithium ions, which can effectively improve the conductivity of lithium ions and reduce the resistance. At the same time, using the rich functional groups on the surface of dickite and the stability of the structure at high temperatures, the wettability, liquid absorption rate and thermal stability of the separator to the electrolyte can be significantly improved after coating the non-woven fabric, thereby improving the performance of the battery at high current. Cycling stability during charge and discharge. The porosity of the porous geolith/PET separator can reach 68%, the liquid absorption rate can reach 198%, and the ion conductivity can reach 11.4mS·cm ^-1 . Using the separator in the LiMn ₂ O ₄ /graphite battery system, after 200 charge-discharge cycles, the battery capacity retention rate reaches 83%, which is obviously better than the commercial PE separator (72%).

Description of drawings

Figure 1. Scanning electron micrograph of porous dickite

Figure 2. The relationship between capacity retention and cycle number of LiMn ₂ O ₄ /graphite battery using porous ground stone/PET separator (1C)

Detailed ways:

The present invention is described in further detail in conjunction with embodiment:

a. Preparation of porous dickite

Dickite and a certain proportion of urea are pulverized in a pulverizer for 5 to 20 minutes, so that the particle size is less than 270 mesh, and the mass of urea is 10 to 25 wt% of the dickite mass. The mixture is placed in an open glass container and placed in a microwave oven. Heat it on medium-high heat for 10-20 minutes, and then put it in an oven at 70°C for 50 hours. Then mix and grind the mixture with potassium chlorate for 40 minutes, the consumption of potassium chlorate is 4% of dickite mass. Finally, the mixture mixed with potassium chlorate was put into an electric furnace at 550° C. for 15 seconds and calcined to obtain a porous stone powder.

b. Preparation of Porous Dictite/PET Separator

After uniformly mixing porous ground stone with binder, water, and modifier in a mass ratio of 60-80:33-13:5:2, the coating slurry is obtained by stirring in a homogenizer for 1-2 hours , and then immerse the PET non-woven fabric in the coating slurry for 30 minutes, and then take it out and dry it in a vacuum oven at 40° C. to obtain a porous stone-coated PET non-woven membrane.

Example 1

a. dickite and a certain proportion of urea are pulverized in a pulverizer for 10 minutes, so that the particle size is less than 270 mesh, and the quality of urea is 10wt% of the dickite quality;

b. Put the mixture in an open glass container, heat it in a microwave oven for 17 minutes, and then put it in an oven at 70°C for 50 hours;

c. the mixture was mixed with potassium chlorate and ground for 40 minutes, and the consumption of potassium chlorate was 4% of dickite quality;

d. Put the mixture mixed with potassium chlorate into an electric furnace at 550°C for 15 seconds and calcinate to obtain porous ground stone powder;

e. After uniformly mixing porous ground stone with binder, water, and modifier in a mass ratio of 80:13:5:2, stir in a homogenizer for 1 hour to obtain a coating slurry;

f. Immerse the PET non-woven fabric in the coating slurry for 30 minutes, then take it out and dry it in a vacuum oven at 40° C. to obtain a porous stone-coated PET non-woven composite separator.

The diaphragm is used in the LiMn ₂ O ₄ /graphite battery system, and the ion conductivity is 11.9 mS·cm ^-1 . After 200 charge-discharge cycles, the battery capacity retention rate reaches 87%.

Example 2

a. dickite and a certain proportion of urea were pulverized in a pulverizer for 15 minutes, so that the particle size was less than 270 mesh, and the quality of urea was 15wt% of the dickite quality;

b. Put the mixture in an open glass container, heat it in a microwave oven for 15 minutes, and then put it in an oven at 70°C for 50 hours;

c. the mixture was mixed with potassium chlorate and ground for 40 minutes, and the consumption of potassium chlorate was 4% of dickite quality;

d. Put the mixture mixed with potassium chlorate into an electric furnace at 550°C for 15 seconds and calcinate to obtain porous ground stone powder;

e. After uniformly mixing porous ground stone with binder, water, and modifier in a mass ratio of 70:23:5:2, stir in a homogenizer for 2 hours to obtain a coating slurry;

f. Immerse the PET non-woven fabric in the coating slurry for 30 minutes, then take it out and dry it in a vacuum oven at 40° C. to obtain a porous stone-coated PET non-woven composite separator.

The diaphragm is used in the LiMn ₂ O ₄ /graphite battery system, and the ion conductivity is 12.2 mS·cm ^-1 . After 200 charge-discharge cycles, the battery capacity retention rate reaches 88%.

Example 3

a. dickite and a certain proportion of urea are pulverized in a pulverizer for 5 minutes, so that the particle size is less than 270 mesh, and the quality of urea is 20wt% of the dickite quality;

b. Put the mixture in an open glass container, heat it in a microwave oven for 20 minutes, and then put it in an oven at 70°C for 50 hours;

c. the mixture was mixed with potassium chlorate and ground for 40 minutes, and the consumption of potassium chlorate was 4% of dickite quality;

d. Put the mixture mixed with potassium chlorate into an electric furnace at 550°C for 15 seconds and calcinate to obtain porous ground stone powder;

e. After uniformly mixing porous ground stone with binder, water, and modifier in a mass ratio of 60:33:5:2, stir in a homogenizer for 1 hour to obtain a coating slurry;

f. Immerse the PET non-woven fabric in the coating slurry for 30 minutes, then take it out and dry it in a vacuum oven at 40° C. to obtain a porous stone-coated PET non-woven composite separator.

The separator is used in the LiMn ₂ O ₄ /graphite battery system, and the ion conductivity is 11.4mS·cm ^-1 . After 200 charge-discharge cycles, the battery capacity retention rate reaches 84%.

Example 4

a. dickite and a certain proportion of urea were pulverized in a pulverizer for 20 minutes, so that the particle size was less than 270 mesh, and the quality of urea was 25wt% of the dickite quality;

b. Put the mixture in an open glass container, heat it in a microwave oven for 10 minutes, and then put it in an oven at 70°C for 50 hours;

c. the mixture was mixed with potassium chlorate and ground for 40 minutes, and the consumption of potassium chlorate was 4% of dickite quality;

d. Put the mixture mixed with potassium chlorate into an electric furnace at 550°C for 15 seconds and calcinate to obtain porous ground stone powder;

e. After uniformly mixing porous ground stone with binder, water, and modifier in a mass ratio of 75:18:5:2, stir in a homogenizer for 2 hours to obtain a coating slurry;

f. Immerse the PET non-woven fabric in the coating slurry for 30 minutes, then take it out and dry it in a vacuum oven at 40° C. to obtain a porous stone-coated PET non-woven composite separator.

The diaphragm is used in the LiMn ₂ O ₄ /graphite battery system, and the ion conductivity is 11.6 mS·cm ^-1 . After 200 charge-discharge cycles, the battery capacity retention rate reaches 85%.

Claims (3)

1. a kind of preparation method of porous dickite coating non-woven fabrics lithium ion battery separator, which is characterized in that including following step It is rapid:

A. dickite and a certain proportion of urea crush 5~20 minutes in pulverizer, make granularity less than 270 mesh, the matter of urea Amount is 10~25wt% of dickite quality, and mixture is placed in open glass container, is put into micro-wave oven high fire heating 10 It~20 minutes, is put into 70 DEG C of baking ovens later and keeps the temperature 50 hours；Again by mixture and potassium chlorate mixed grinding 40 minutes, potassium chlorate Dosage be the 4% of dickite quality；Finally the mixture for mixing potassium chlorate is put into 550 DEG C of electric furnace and is calcined 15 seconds, obtained To porous dickite powder；

B. after evenly mixing by porous dickite and binder, water, modifying agent 60-80:33-13:5:2 in mass ratio, it is being homogenized It is stirred in machine and obtains within 1-2 hours coating slurry, then PET non-woven fabrics is immersed in coating slurry 30 minutes, then taken out 40 DEG C vacuum oven in it is dry after obtain the PET nonwoven cloth diaphragm of porous dickite coating.

2. a kind of preparation method of porous dickite coating non-woven fabrics lithium ion battery separator described in accordance with the claim 1, It is characterized in that, the dickite is the dickite for originating from the white county of Jilin governor, and siliceous miscellaneous phase content is less than 5%, dickite Crystallization index Hinckley index value is greater than 1；The binder is LA132 or LA132 and SBR mixture；The modifying agent For silane coupling agent DL171.

3. a kind of porous dickite coats non-woven fabrics lithium ion battery separator, it is characterised in that: any according to claim 1-2 Method is made.