NL2030649B1

NL2030649B1 - Preparation of modified ammonium oxofluorotitanate for lithium-ion battery and use thereof

Info

Publication number: NL2030649B1
Application number: NL2030649A
Authority: NL
Inventors: Zheng Runguo; Sun Hongyu; Wang Zhiyuan; Jiang Nan; Liu Yanguo
Original assignee: Univ Northeastern Qinhuangdao
Priority date: 2022-01-21
Filing date: 2022-01-21
Publication date: 2023-08-01

Abstract

Preparation of modified ammonium oxofluorotitanate for lithium—ion battery and use thereof is provided. The preparation method specifically comprises two steps, preparation of NH4TiOF3 negative electrode material and modification of NH4TiOF3 negative electrode material. The T102 precursor,NH4TiOF3, prepared by the method of the present disclosure has a uniform pill—like morphology with a secondary particle diameter of 10 pm and a thickness of 1 pm. The lithium—ion battery using the modified NH4TiOF3 prepared by the method of the present disclosure is subjected to charging and discharging tests at a voltage ranging from 1 to 3V, showing a maximum capacity of 182 mAh g’l. Meanwhile, it exhibits excellent cycle stability which can maintain a reversible capacity of 128.6 mAh g il after 2000 cycles at a current density of 1 A gil, and a reversible capacity of 89.6 mAh (jl at a high current density of 20 Ag?

Description

P1020/NLpd

PREPARATION OF MODIFIED AMMONIUM OXOFLUOROTITANATE FOR LITHIUM-ION

BATTERY AND USE THEREOF

TECHNICAL FIELD

The present disclosure belongs to the technical field of new energy material manufacture, and specifically relates to the prep- aration of a TiO, precursor, NH, TiOF;, as the negative electrode ma- terial for lithium-ion battery, method of modification and use thereof.

BACKGROUND ART

TiO,-based materials have low electronic conductivity, low ion diffusion coefficient, and increased electrolyte/electrode inter- face resistance at high current densities, which limit the appli- cation of Ti0;-based materials.

In order to address the above shortcomings of Ti0;-based nega- tive electrode materials, researchers have found that multi-scale construction of nanomaterial structures can prevent the agglomera- tion of nanomaterial during cycling, improve the material’s elec- tronic conductivity and increase its ion diffusion coefficient. In addition, the design of surface/interface structure is also one of the effective ways to improve the material’s properties. In the present disclosure, NH,4TiOF3 is used as the negative electrode ma- terial, and there are nano-sized particles inside the material, which can increase the contact area between the NH,TiOF3 electrode material and the electrolyte, accelerating the transmission of electrons and ions. The secondary structure can effectively reduce the agglomeration ofNH,TiOF; during charging and discharging pro- cesses due to its micron-size. Then, after annealing and modify- ing, the formed interface structure can produce built-in electric field, accelerating the lithium ion diffusion and improving its rate capability. Subjected to charging and discharging tests at a voltage ranging from 1 to 3V, the electrode maintains a reversible capacity of 89.6 mAh g* at a high current density of 20 Agt and exhibits excellent cycle performance and good capacity retention.

SUMMARY

In view of the problems existing in the prior art, the pre- sent disclosure provides a method of preparation of a TiO, precur- sor, NH,TiOF;, as the negative electrode material for lithium-ion battery, a method of modification and use therecf. The lithium-ion battery using modified NH,TIOF; as the negative electrode material can achieve excellent cycle performance and rate capability. More importantly, the preparation and modification conditions are mild, green, and environmentally friendly.

A method for preparing modified ammonium oxofluorotitanate (NH,TiOF3) for lithium-ion battery is provided in the present dis- closure, comprising the following steps:

Step 1 Preparation of NH,TIOF;: (1) A certain amount of ammonium fluoride is added to the corresponding volume of deionized water; after completely dissolv- ing of the ammonium fluoride, ethylene glycol and titanium oxysul- fate-sulfuric acid hydrate are added; the obtained mixture is stirred to form a uniform solution; {2) The uniform solution is transferred to an autoclave and reacts at 180- 220°C for 50-90 min; (3) After cooling to room temperature, the product is washed three times with deionized water; then, the product is dried in an oven at 60°C for 12 h and sieved through a 300-mesh sieve to ob- tain NH,TIiOF3;

Step 2 Preparation of modified NH,TiOF;:

The obtained NH,TiOF; is annealed in argon at 150 to 450°C for 1 to 4 h, and then taken out after cooling to room temperature to obtain modified ammonium oxofluorotitanate for lithium-ion bat- tery, wherein the flow rate of argon is 50 mL/min.

The above method for preparing modified ammonium oxofluo- rotitanate for lithium-ion battery, wherein:

In step 1(1), the mass to volume ratio of ammonium fluoride and deionized water is (1~1.5):10, preferably 1.3:10; the volume ratio of ethylene glycol to deionized water is 1:10.

In step 1(1), the ratio of the addition amount of titanium oxysulfate-sulfuric acid hydrate to the mass of ammonium fluoride is (2.5 to 3.1):1, preferably 2.5:1.

In step 1(2), the preferred temperature and time for the re- action are 200°C and 70 min, respectively.

In step 2, the preferred temperature and time for annealing treatment are 250°C and 2 h, respectively.

The modified ammonium oxofluorotitanate prepared by the meth- od of the present disclosure, acetylene black, and polyvinylidene fluoride are mixed in 8:1:1 mass ratio to obtain a slurry, and then the slurry is coated on a copper foil and dried to obtain a negative electrode material for lithium-ion battery. Subsequently, materials including the gasket, lithium foil, electrolyte, separa- tor, electrolyte, and the prepared negative electrode are assem- bled into a lithium-ion coin battery according te methods known in the art. Finally, the assembled coin battery is charged and dis- charged at a voltage ranging from 1 to 3V.

The present disclosure has the following beneficial effects: (1) The TiO, precursor, NH,TiOF; is prepared in the present disclosure by adjusting the reaction temperature and time of the hydrothermal reaction. SEM shows that the precursor has a uniform pill-like morphology with a secondary particle diameter of 10 um and a thickness of 1 um. (2) The lithium-ion battery using the modified NH,TIOF; pre- pared by the method of the present disclosure is subjected to charging and discharging tests at a voltage ranging from 1 to 3V, showing a maximum capacity of 182 mAh g *. In addition, it exhibits excellent cycle stability which can maintain a reversible capacity of 128.6 mAh g* after 2000 cycles at a current density of 1 A g™* and a reversible capacity of 89.6 mAh g' at a high current density of 20 A gt. (3) The TiO, precursor, NH,TiOFz is directly used as the nega- tive electrode material for lithium-ion batteries for the first time in the present disclosure. The method for preparing the nega- tive electrode material is simple. A thin layer of TiO, can be ob- tained by adjusting the process parameters. The built-in electric field at the interface structures accelerates the migration rate of lithium ions, leading to \ excellent cycle stability and rate performance. Therefore, it is very beneficial for large-scale pro- duction, development, and application. A new type of negative electrode material is provided for lithium-ion batteries.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the XRD pattern of NH,TiOF3 obtained in Example 1 of the present disclosure.

FIG. 2 shows the SEM image of NH,TiOF; obtained in Example 1 of the present disclosure.

FIG. 3 shows the XRD pattern of modified NH,TiOF3 obtained in

Example 1 of the present disclosure.

FIG. 4 shows the SEM image of modified NH,TiOF3 obtained in

Example 1 of the present disclosure.

FIG. 5 shows the XRD pattern of modified NH,TiOF; obtained in

Example 2 of the present disclosure.

FIG. 6 shows the SEM image of modified NH,TIOF; obtained in

Example 2 of the present disclosure.

FIG. 7 shows the XRD pattern of modified NH,TiOF; obtained in

Example 3 of the present disclosure.

FIG. 8 shows the SEM image of modified NH,TiOF3 obtained in

Example 3 of the present disclosure.

FIG. 9 shows the XRD pattern of Ti0, obtained in Example 4 of the present disclosure.

FIG. 10 shows the SEM image of TiO, obtained in Example 4 of the present disclosure.

FIG. 11 shows the cycle performance of lithium-ion batteries using the products in Examples 1-4 of the present disclosure.

FIG. 12 shows the rate performance of lithium-ion batteries using the products in Examples 1-4 of the present disclosure.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Example 1

A method for preparing modified ammonium oxofluorotitanate for lithium-ion battery specifically comprises the following steps:

Step 1 Preparation of NH,TIiOF;: (1) 1.3 g of ammonium fluoride is added to 10 mL of deionized water; after completely dissolving of the ammonium fluoride, 100 5 mL of ethylene glycol and 3.25 g of titanium oxysulfate-sulfuric acid hydrate are added; the mixture is stirred to form a uniform solution; (2) The uniform solution is transferred to a 200 mL stainless steel autoclave, and reacts at 200°C for 70 min; (3) After cooling to room temperature, the product is washed three times with deionized water; then, the product is dried in an oven at 60°C for 12 h and sieved through a 300-mesh sieve to ob- tain NH,TiOF; (referred to as NTF-AP);

Step 2 Preparation of modified NH,Ti0F3:

The obtained NTF-AP is annealed in a tube furnace in argon at 150°C for 2 h, and then taken out after cooling to room tempera- ture to obtain modified ammonium oxofluorotitanate (referred to as

NTF-150 in Example 1) for lithium-ion battery, wherein the flow rate of argon is 50 mL/min.

The XRD pattern and SEM image of the obtained NTF-AP are shown in FIGs. 1 and 2, respectively, and the XRD pattern and SEM image of NTF-150 are shown in FIGs. 3 and 4, respectively. FIG. 1 shows that NTF-AP is composed of single-phase NH,TiOF3; FIGs. 2 and 4 show that the surfaces of NTF-AP and NTF-150 are smooth; FIG. 3 shows that NTF-AP is partially decomposed into (NH;),TiFs and TiO, during the process of annealing NTF-AP at 150°C to obtain NTF-150, so the obtained NTF-150 product consists of the three phases of

NH,TiOF;, (NH) -TiFs and TiO ;.

Example 2

Step 1 Preparation of NH,TiOF;: (1) 1.3 g of ammonium fluoride is added to 10 mL of deionized water; after the ammonium fluoride is completely dissolved, 100 mL of ethylene glycol and 3.25 g of titanium oxysulfate-sulfuric acid hydrate are added; the mixture is stirred to form a uniform solu- tion; (2) The uniform solution is transferred to a 200 mL stainless steel autoclave and reacts at 200°C for 70 min; (3) After cooling to room temperature, the product is washed three times with deionized water; then, the product is dried in an oven at 60°C for 12 h and sieved through a 300-mesh sieve to ob- tain NH,TiOF; (referred to as NTF-AP);

Step 2 Preparation of modified NH,TiOF3:

The obtained NTF-AP is annealed in a tube furnace in argon at 250°C for 2 h, and then taken out after cooling to room tempera- ture to obtain modified ammonium oxofluorotitanate (referred to as

NTF-250 in Example 2) for lithium-ion battery, wherein the flow rate of argon is 50 mL/min.

The XRD pattern and SEM image of the obtained NTF-250 are shown in FIGs. 5 and 6, respectively. FIG. 5 shows that the prod- uct consists of two phases ofNH,TiOF; and TiO, when it is annealed at 250°C. FIG. 6 shows that the surface of the obtained NTF-250 is smooth.

Example 3

Step 1 Preparation of NH,TiOF;: (1) 1.3 g of ammonium fluoride is added to 10 mL of deionized water; after completely dissolving of the ammonium fluoride, 100 mL of ethylene glycol and 3.25 g of titanium oxysulfate-sulfuric acid hydrate are added; the mixture is stirred to form a uniform solution; (2) The uniform solution is transferred to a 200 mL stainless steel autoclave, and reacts at 200°C for 70 min; (3) After cooling to room temperature, the product is washed with deionized water three times; then, the product is dried in an oven at 60°C for 12 h and sieved through a 300-mesh sieve to ob- tain NH,TiOF; (referred to as NTF-AP);

Step 2 Preparation of modified NH,TiOF3:

The obtained NTF-AP is annealed in a tube furnace in argon at 350°C for 2 h, and then taken out after cooling to room tempera- ture to obtain modified ammonium oxofluorotitanate (referred to as

NTF-350 in Example 3) for lithium-ion battery, wherein the flow rate of argon is 50 mL/min.

The XRD pattern and SEM image of the obtained NTF-350 are shown in FIGs. 7 and 8, respectively. FIG. 7 shows that the prod- uct still consists of the two phases of NH,TiOF; and TiO, when it is annealed at 350°C. FIG. 8 shows that the surface of the product is rough when the obtained NTF-350 is annealed at a temperature up to 350°C.

Example 4

Step 1 Preparation of NH,TIiOF;: (1) 1.3 g of ammonium fluoride is added to 10 mL of deionized water; after completely dissolving of the ammonium fluoride, 100 mL of ethylene glycol and 3.25 g of titanium oxysulfate-sulfuric acid hydrate are added; the mixture is stirred to form a uniform solution; (2) The uniform solution is transferred to a 200 mL stainless steel autoclave, and reacts at 200°C for 70 min; (3) After cooling to room temperature, the product is washed three times with deionized water; then, the product is dried in an oven at 60°C for 12 h and sieved through a 300-mesh sieve to ob- tain NH,TiOF; (referred to as NTF-AP);

Step 2 Preparation of modified NH,TiOF,:

The obtained NTF-AP is annealed in a tube furnace in argon at 450°C for 2 h, and then taken out after cooling to room tempera- ture to obtain modified ammonium oxofluorotitanate (referred to as

NTF-450 in Example 4) for lithium-ion battery, wherein the flow rate of argon is 50 mL/min.

The XRD pattern and SEM image of the obtained NTF-450 are shown in FIGs. 9 and 10, respectively. FIG. 9 shows that the prod- uct is completely composed of single-phase TiO; when it is annealed at 450°C. FIG. 10 shows that the shell of product particles falls off and cracks when the annealing temperature is up to 450°C.

As can be seen from the above results of Examples 1 to 4, during the process of preparing modified NH, TiOF;, the modified

NH,TiOF; is partially decomposed into (NH;).TiF. and TiO, when the annealing temperature is 150°C, whereby the product consists of the three phases of NH,TiOF;, (NH;)-TifF,s and TiO,. And when the an- nealing temperature rises to 250°C and 350°C, the product only contains the two phases of NH, TiOF; and TiO,. When the annealing temperature continues to rise to 450°C, the product only contains single-phase TiO,. The above results show that with the increase of annealing temperature, the content of TiO, in the product gradually increases until the product is completely composed of single-phase

Ti0,. In addition, it can be seen from the SEM images of FIG. 4,

FIG. 6, FIG. 8 and FIG. 10 that when the annealing temperatures are 150°C and 250°C, the surfaces of the products are smooth; when the temperature reaches 350°C, the surface of the product becomes rougher; and when the annealing temperature reaches 450°C, the shell of product particles falls off or cracks.

The NTF-X (X stands for 150, 250, 350 or 450) and NTF-AP pre- pared by the methods of the present disclosure are respectively mixed with acetylene black and polyvinylidene fluoride in 8:1:1 mass ratio to obtain a slurry, and then the slurry is coated on a copper foil and dried to obtain a negative electrode material for lithium-ion battery. Subsequently, materials including the gasket, lithium foil, electrolyte, separator, electrolyte, and the pre- pared negative electrode are assembled into a lithium-ion battery according to methods known in the art. Finally, the assembled coin battery is charged and discharged at a voltage ranging from 1 to 3V. The charging and discharging tests of the lithium-ion battery is tested. The cycle performance is tested at a current density of 0.2 Ag}. The rate capacity is tested by at a maximum current den- sity of 20 Ag’. Their electrochemical performances are shown in

Table 1, FIG. 11 and FIG. 12.

Table 1 Test results of electrochemical performance of lithi- um-ion batteries

Reversible ca- Rate capacity le

TT ere fer

As can be seen from Table 1, the cycle performance and rate performance of the lithium-ion battery in Example 2 are signifi- cantly improved than those in other examples. As shown in FIG. 11, the product in Example 2 possesses the best cycle performance with a reversible capacity of 159.5 mAh g} after 200 cycles at a cur- rent density of 0.2 A g. As shown in FIG. 12, its reversible ca- pacity reaches 89.6 mAh g at a current density of 20 A gt.

The modified TiO, precursor, NH,TIOF; mesocrystal, is directly used as the negative electrode material for lithium-ion batteries for the first time in the present disclosure. In the present dis- closure, a thin layer of TiO, is obtained during the annealing pro- cess of NH,TiOF; in argon, thereby leading to an interface struc- ture of NH,TiOF;-Ti0,. The built-in electric field between the in- terface structures acting on the surface can provide external cou- lombic force to promote lithium ion diffusion dynamics, accelerat- ing the migration of Li ions and improving the rate capability of lithium-ion batteries. The results show that the direct modifica- tion of NH,TiOF; mesocrystals is simple and effective, which can effectively improve the electrochemical performance of lithium-ion batteries and provide a new idea for the preparation of negative electrode materials for lithium-ion batteries.

Claims

CONCLUSIONS

A process for preparing modified ammonium oxzofluoro titanate for lithium-ion batteries comprising the following steps: Step 1 Preparation of NH,TiOF:3: (1) adding a certain amount of ammonium fluoride to the corresponding volume of deionized water; after complete dissolution of the ammonium fluoride, ethylene glycol and titanium oxysulfate sulfuric acid hydrate are added; the mixture is stirred to form a uniform solution; wherein the mass-to-volume ratio of ammonium fluoride and deionized water is (1 - 1.5) : 10, preferably 1.3 : 10; the volume ratio of ethylene glycol to deionized water is 1:10; the mass ratio of titanium oxysulfate sulfuric acid hydrate to ammonium fluoride is (2.5 ~ 3.1) : 1; (2) transferring the uniform solution to an autoclave and reacting for 50 to 90 minutes at 180 to 220°C; (3) after cooling to room temperature, the product is washed three times with deionized water; then the product is dried in an oven at 60°C for 12 hours and sieved through a 300 mesh sieve to obtain NH 3 TiOF 3 ; wherein the resulting NH 1 TiOF 3 has a uniform pill-like morphology with a secondary particle diameter of 10 µm and a thickness of 1 µm; Step 2 Preparation of modified NH,TiOOF3: Annealing of the resulting NH,TIOF; is carried out for 1 — 4 hours in argon at 150 + 450 °C and then, after cooling to room temperature, removed from the oven to obtain modified ammonium oxofluorotitanate for lithium-ion batteries; wherein the flow rate of argon is 50 ml/min; the obtained modified ammonium oxofluorotitanate is used as a negative electrode material for lithium-ion batteries, in particular, the modified ammonium oxofluorotitanate, acetylene black and polyvinylidene fluoride are mixed in a 8:1:1 mass ratio to obtain a suspension, and then the suspension is applied by coating on a copper foil and dried to obtain a negative electrode material for lithium-ion batteries.

Use of the negative electrode material prepared by the method of claim 1 in a lithium-ion battery, wherein the charge and discharge tests are performed at a voltage ranging from 1 to 3V, the electrode materials having a maximum capacity of 182 mAh g*' and maintain a reversible capacity of 128.6 mAh g+: after 2000 cycles at a current density of 1 A gt, and a reversible capacity of 89.6 mAh g™* at a high current density of 20 Ag}.