CN110212240A - Lithium ion solid electrolyte and preparation method thereof - Google Patents

Abstract

The invention relates to a lithium ion solid electrolyte and a preparation method thereof, belonging to the field of solid lithium batteries. The present invention prepares a novel Li superionic conductor Li _1+x Zr ₂ P _{3‑x Six} O ₁₂ (0≤x≤3), which can be applied to the solid electrolyte of solid-state batteries, and the ionic conductivity is greater than 10 ^‑3 S/cm, good electrochemical stability, no side reactions, good stability in the air environment, good processing performance during the preparation of solid-state batteries, and good mechanical and chemical compatibility with electrode materials.

Description

Lithium-ion solid electrolyte and preparation method thereof

technical field

The invention relates to a lithium ion solid electrolyte and a preparation method thereof, belonging to the technical field of lithium ion solid electrolytes.

Background technique

Lithium-ion batteries are currently the energy storage devices with the highest energy density, but the energy density gradually reaches the upper limit, and the increase in energy density makes the safety of lithium-ion batteries increasingly prominent. Solid-state batteries are expected to become higher specific energy density and safer energy storage devices than lithium-ion batteries. The performance of solid-state electrolyte is the most critical factor determining the performance of solid-state batteries.

In the prior art, although the electronic conductivity of solid electrolytes with chalcogenide and antiperovskite structures can reach 10 ^{- 2} S/cm, there are the following problems:

1. Poor chemical stability;

2. Poor electrochemical stability;

3. Poor processing performance.

Contents of the invention

The technical solution problem of the present invention is: overcome the deficiency of prior art, propose a kind of lithium ion solid electrolyte and preparation method thereof, this lithium ion solid electrolyte has good chemical stability, electrochemical stability and operability, and ion conductivity is high (greater than 10 ^-3 S/cm).

Technical solution of the present invention is:

A lithium ion solid electrolyte, the solid electrolyte is a Li superionic conductor, chemical formula Li _{1+x Zr 2} P _{3- x} Six O ₁₂ , 0≤x≤3, preferably Li ₃ Si ₂ Zr ₂ PO ₁₂ .

A preparation method of a lithium ion solid state electrolyte, the steps of the method comprising:

(1) Put the Na superionic conductor powder into a solution containing Li ions, heat and stir, and an exchange reaction of Na ions and Li ions occurs during the heating and stirring process to obtain a mixture;

(2) filter the mixture obtained in step (1), then clean the filter cake to obtain Li superionic conductor powder, and repeatedly wash the Li superionic conductor powder with alcohol or distilled water to obtain pure Li superionic Conductor powder;

(3) heat-treating the pure Li superionic conductor powder obtained in step (2) to obtain a lithium-ion solid electrolyte.

In the step (1), the chemical formula of the Na superionic conductor powder is Na _1+x Zr ₂ P _{3-x Six} O ₁₂ , 0≤x≤3, preferably Na ₃ Si ₂ Zr ₂ PO ₁₂ , Na ₄ Zr ₂ (SiO ₄ ) ₃ , NaZr ₂ (PO ₄ ) ₃ , Na ₃ Hf ₂ Si ₂ PO ₁₂ , Na ₃ La(PO ₄ ) ₂ , Na _1.3 Ti _1.7 Al _0.3 (PO ₄ ) ₃ , Na ₃ V ₂ (PO ₄ ) ₃ , Na _2.96 Nb _0.04 Zr _1.96 Si ₂ PO ₁₂ ;

In the step (1), in the Li ion solution, the solvent is an ionic liquid, and the ionic liquid is C ₆ H ₁₁ BF ₄ N ₂ , C ₈ H ₂₀ BF ₄ NO, C ₇ H ₁₆ BF ₄ N, C ₈ H ₁₁ F ₆ N ₃ O ₄ S ₂ , C ₈ H ₁₆ F ₆ N ₂ O ₄ S ₂ , C ₆ H ₁₁ F ₂ N ₃ O ₄ S ₂ or C ₉ H ₂₀ F ₂ N ₂ O ₄ S ₂ ; The lithium salt that produces li ions is LiClO ₄ , LiPF ₆ , LiNO ₃ , LiCl, LiBF4, LiTFSI, LiBOB, LiDFOB or LiFSI;

In the step (1), the heating temperature is 50-400°C, and the stirring time is 2-100h;

In the described step (2), when cleaning, use methanol, ethanol or deionized water to clean;

In the step (3), the heat treatment temperature is 300-900°C, preferably 300-700°C, and the heat treatment time is 2-10h.

A preparation method of a lithium ion solid state electrolyte, the steps of the method comprising:

(1) Na superionic conductor and Li salt are mixed, then heated and stirred until the Li salt is in a molten state, Na ion and Li ion exchange reaction occurs in the heating and stirring process, down to room temperature, Li superionic conductor/ Lithium molten salt mixture;

(2) Mix the Li superionic conductor/lithium molten salt mixture obtained in step (1) with distilled water/alcohol to dissolve the lithium molten salt in distilled water/alcohol, then filter, and clean the filter cake to obtain Li superion conductor powder, and the Li superionic conductor powder is washed repeatedly with alcohol or distilled water to obtain pure Li superionic conductor powder;

(3) heat-treating the pure Li superionic conductor powder obtained in step (2) to obtain a lithium-ion solid electrolyte.

In the step (1), the chemical formula of the Na superionic conductor powder is Na _1+x Zr ₂ P _{3-x Six} O ₁₂ , 0≤x≤3, preferably Na ₃ Si ₂ Zr ₂ PO ₁₂ , Na ₄ Zr ₂ (SiO ₄ ) ₃ , NaZr ₂ (PO ₄ ) ₃ , Na ₃ Hf ₂ Si ₂ PO ₁₂ , Na ₃ La(PO ₄ ) ₂ , Na _1.3 Ti _1.7 Al _0.3 (PO ₄ ) ₃ , Na ₃ V ₂ (PO ₄ ) ₃ , Na _2.96 Nb _0.04 Zr _1.96 Si ₂ PO ₁₂ ;

In the described step (1), the lithium salt is an inorganic lithium salt such as lithium chloride, lithium nitrate, lithium sulfate, lithium hydroxide or a mixture of these salts, as long as the lithium salt that can melt at a certain high temperature can be selected;

In the described step (1), the heating temperature is determined according to the melting point of the lithium salt selected, generally in the range of 50-150 degrees above the melting point, and the stirring time is determined according to the degree of Li/Na exchange, generally no more than 100h, Preferably 2-100h;

In the described step (2), when cleaning, use methanol, ethanol or deionized water to clean;

In the step (3), the heat treatment temperature is 300-900°C, preferably 300-700°C, and the heat treatment time is 2-10h.

Beneficial effect

(1) The ionic conductivity of the solid electrolyte of the present invention is greater than 10 ^-3 S/cm, the electrochemical stability is better, there is no side reaction, and at the same time, the processability is good in the preparation process of the solid state battery, and it is mechanically and chemically compatible with the electrode material Good sex.

(2) The present invention proposes the use of a sodium superionic conductor (NASICON) structure to synthesize a lithium superionic conductor, by putting NASICON into a solvent or molten salt containing lithium ions, allowing it to undergo an exchange reaction of sodium and lithium ions, LISICON lithium-ion conductors that form a NASICON-like structure;

(3) In the present invention, a solid sodium ion conductor (NASICON) is first synthesized, and then an ion exchange reaction of sodium/lithium ions is carried out in a lithium ion solvent or molten salt to synthesize a lithium ion conductor (LISICON). The obtained lithium ion conductor inherits the structure of the sodium ion conductor, and shows an ionic conductivity equal to or higher than that of the sodium ion conductor. The lithium ion conductor shows good stability to lithium metal, and is an excellent lithium ion solid state electrolyte.

Description of drawings

Figure 1 is the XRD patterns of Na ₃ Si ₂ Zr ₂ PO ₁₂ and ionic liquid exchanged Li ₃ Si ₂ Zr ₂ PO ₁₂ .

Fig. 2 is the XRD patterns of Na ₃ Si ₂ Zr ₂ PO ₁₂ and molten salt exchanged Li ₃ Si ₂ Zr ₂ PO ₁₂ .

Detailed ways

The present invention will be further described below in conjunction with drawings and embodiments.

Example 1

A lithium ion solid electrolyte, the solid electrolyte is Li ₃ Si ₂ Zr ₂ PO ₁₂ .

A preparation method of a lithium ion solid state electrolyte, the steps of the method comprising:

(1) Put 0.71g Na ₃ Si ₂ Zr ₂ PO ₁₂ into 5.74g of ionic liquid C ₈ H ₁₁ F ₆ N ₃ O ₄ S ₂ , where the ionic liquid is the solvent, then heat to 100°C and stir 10h, the exchange reaction of Na ion and Li ion takes place in heating and stirring process, obtains mixture;

(2) the mixture obtained in step (1) is filtered, and then the filter cake is cleaned with deionized water to obtain a Li superionic conductor;

(3) heat-treating the Li superionic conductor obtained in step (2) at 300° C. for 5 hours to obtain a lithium-ion solid electrolyte Li ₃ Si ₂ Zr ₂ PO ₁₂ .

The XRD spectrum of the obtained lithium-ion solid electrolyte Li ₃ Si ₂ Zr ₂ PO ₁₂ and the general spectrum of Na ₃ Si ₂ Zr ₂ PO ₁₂ are shown in Figure 1;

The ion conductivity of the obtained lithium ion solid electrolyte Li ₃ Si ₂ Zr ₂ PO ₁₂ was 6.7×10 ⁻³ S/cm.

Example 2

A lithium ion solid electrolyte, the solid electrolyte is Li ₃ Si ₂ Zr ₂ PO ₁₂ .

A preparation method of a lithium ion solid state electrolyte, the steps of the method comprising:

(1) Add 1g Na ₃ Si ₂ Zr ₂ PO ₁₂ into 10g LiNO ₃ , grind and mix thoroughly to form a homogeneous mixture;

(2) Heating the mixture of step (1) to 350° C., keeping it warm for 20 hours, and cooling to room temperature;

(3) Add deionized water to the mixture obtained in step (2), wait for LiNO ₃ to fully dissolve, and then filter. The obtained filter cake was cleaned 3 times with distilled water, and the Li superionic conductor obtained in 100 degree drying step (3) was obtained for 10 hours to obtain Li solid state electrolyte;

(4) heat-treating the Li solid electrolyte obtained in step (3) at 300° C. for 5 h to obtain a recrystallized lithium ion solid electrolyte Li ₃ Si ₂ Zr ₂ PO ₁₂ .

The XRD spectrum of the obtained lithium-ion solid electrolyte Li ₃ Si ₂ Zr ₂ PO ₁₂ and the general spectrum of Na ₃ Si ₂ Zr ₂ PO ₁₂ are shown in Figure 2;

The ion conductivity of the obtained lithium ion solid electrolyte Li ₃ Si ₂ Zr ₂ PO ₁₂ was 7× ^{10 −3} S/cm.

Claims (10)

1. a kind of lithium ion solid electrolyte, it is characterised in that: the solid electrolyte is Li superionic conductors, chemical formula Li_{1+ x}Zr₂P_3-xSi_xO₁₂, 0≤x≤3.

2. a kind of lithium ion solid electrolyte according to claim 1, it is characterised in that: solid electrolyte is Li₃Si₂Zr₂PO₁₂。

3. a kind of preparation method of lithium ion solid electrolyte, it is characterised in that the step of this method includes:

(1) Na superionic conductors powder and Li salt are mixed, then carrying out heating stirring to Li salt is molten condition, then It is down to room temperature, obtains Li superionic conductors/lithium molten salt mixture；

(2) Li superionic conductors/lithium molten salt mixture that step (1) obtains is mixed with distilled water or alcohol, makes to distill Water/alcohol dissolves lithium fused salt, then filters, and filter cake is cleaned, and obtains Li superionic conductors powder, and by Li surpass from Sub- conductor powder alcohol or distilled water clean repeatedly, obtain pure Li superionic conductors powder；

(3) the pure Li superionic conductors powder that step (2) obtains is heat-treated, obtains lithium ion solid electrolyte.

4. a kind of preparation method of lithium ion solid electrolyte according to claim 3, it is characterised in that: the step (1) in, the chemical formula of Na superionic conductors powder is Na_1+xZr₂P_3-xSi_xO₁₂, 0≤x≤3.

5. a kind of preparation method of lithium ion solid electrolyte according to claim 4, it is characterised in that: Na super-ionic is led Body powder is Na₃Si₂Zr₂PO₁₂、Na₄Zr₂(SiO₄)₃、NaZr₂(PO₄)₃、Na₃Hf₂Si₂PO₁₂、Na₃La(PO₄)₂、 Na_1.3Ti_1.7Al_0.3(PO₄)₃、Na₃V₂(PO₄)₃Or Na_2.96Nb_0.04Zr_1.96Si₂PO₁₂。

6. a kind of preparation method of lithium ion solid electrolyte according to claim 3, it is characterised in that: the step (1) in, lithium salts is the mixture of one or more of lithium chloride, lithium nitrate, lithium sulfate, lithium hydroxide.

7. a kind of preparation method of lithium ion solid electrolyte according to claim 3, it is characterised in that: the step (1) in, heating temperature is within the scope of the above 50-150 degree of lithium salts fusing point.

8. a kind of preparation method of lithium ion solid electrolyte according to claim 3, it is characterised in that: the step (1) in, heating time 2-100h.

9. a kind of preparation method of lithium ion solid electrolyte according to claim 3, it is characterised in that: the step (2) it in, when being cleaned, is cleaned using methanol, ethyl alcohol or deionized water.

10. a kind of preparation method of lithium ion solid electrolyte according to claim 3, it is characterised in that: the step Suddenly in (3), heat treatment temperature be 300-900 DEG C, preferably 300-700 DEG C, heat treatment time 2-10h.