CN115441046A - Lithium-containing cyanamide compound solid electrolyte, preparation method and application thereof, and solid lithium battery - Google Patents

Lithium-containing cyanamide compound solid electrolyte, preparation method and application thereof, and solid lithium battery Download PDF

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CN115441046A
CN115441046A CN202110616399.6A CN202110616399A CN115441046A CN 115441046 A CN115441046 A CN 115441046A CN 202110616399 A CN202110616399 A CN 202110616399A CN 115441046 A CN115441046 A CN 115441046A
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lithium
solid electrolyte
solid
electrolyte
cyanamide compound
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黄富强
孔舒仪
董武杰
叶斌
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Shanghai Institute of Ceramics of CAS
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
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Abstract

The invention relates to a lithium-containing cyanamide compound solid electrolyte, a preparation method and application thereof, and a solid lithium battery 2 M(CN 2 ) 3 (ii) a Wherein M is at least one of positive quadrivalent elements of Ti, sn, ge, mn, si and Zr; preferably, M is Zr.

Description

Lithium-containing cyanamide compound solid electrolyte, preparation method and application thereof, and solid lithium battery
Technical Field
The invention relates to a lithium-containing cyanamide compound solid electrolyte, a preparation method and application thereof, and a solid lithium battery, belonging to the technical field of new energy.
Background
The growing demand for safe power transport places higher demands on the battery systems, in particular with regard to stability, safety and power/energy density. Over the past 30 years, conventional Lithium Ion Batteries (LIBs) using organic liquids as electrolytes have been developed and used in almost all energy storage technologies. However, further improvements to lithium ion batteries are limited by the inherent disadvantages of organic Liquid Electrolytes (LEs). The thermal instability and flammability of the LEs threatens battery safety. Dissolution of metal ions in the positive active material into the LEs triggers "chemical cross-talk" between the electrodes, thereby affecting the long-term stability of the LIBs. In addition, dendrite formation and the resulting consumption of LEs reduce the likelihood of lithium metal acting as a negative electrode. These drawbacks have prompted the development of rechargeable all-solid-state batteries (ASSBs) in which the safety of the batteries is improved by using a thermally stable Solid Electrolyte (SE). If lithium metal is used as the negative electrode material, ASSBs hold great promise for achieving high energy and high power density, provided that the interfacial resistance can be kept low.
Solid State Electrolytes (SSEs) have the advantages of flame retardancy, broad electrochemical windows, etc. that avoid potential safety hazards. SSEs offer a possibility to use high voltage anodes with outstanding mechanical strength to some extent to resist lithium dendrite growth. Over the last two decades, a wide variety of SSEs have been studied, including NASICON, perovskite and anti-perovskite types, sulfide-based glasses or ceramics, garnet types, and the like. A successful solid-state battery needs to address not only the problem of increased ionic conductivity, but more importantly the large impedance of the grain boundaries and the electrolyte/electrode interface. It is generally believed that the thermal stability of crystalline electrolytes is superior to that of glass-type materials. However, glass is excellent in reducing grain boundaries, and the lithium ion conductivity of SSEs is continuously improved due to a large decrease in grain boundary resistance and ultra-high-speed transmission of lithium ions, such as Li 10 GeP 2 S 12 (LGPS) ion conductivity 10 - 2 S/cm。Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 The lithium ion conductivity of (2) is 25mS/cm, even higher than that of the corresponding liquid electrolyte. However, the narrow electrochemical window and poor interfacial stability for lithium limit the application of LGPS. Oxygen nitride type solid electrolytes, such as lithium phosphorus oxygen nitride (LiPON) vs. metallic LiElectrochemical stability, but the relatively low ionic conductivity limits its use to thin film batteries only. Calculations based on Density Functional Theory (DFT) indicate that almost all SSEs are thermodynamically unstable to Li. While garnet-type solid electrolyte Li 7 La 3 Zr 2 O 12 (LLZO) has the lowest reduction potential for Li, forming the most stable Li/SSEs interface. The garnet-type solid electrolyte also has the advantages of wide electrochemical window, stability in air exposure and high ionic conductivity at room temperature. Since the first discovery of cubic phase LLZO, research on lowering the electrolyte/electrode interface resistance has been receiving extensive attention in recent years. From the negative electrode viewpoint, li is inevitably formed 2 CO 3 So that the fused lithium has poor wettability on the garnet surface. Insufficient surface contact of the Li/garnet-type electrolyte results in considerable impedance. To solve this problem, one typically uses soft polymers and metal/metal oxides (e.g., si, mg, al) 2 O 3 And ZnO, etc.), or compounding the Li negative electrode with carbon black or other metals.
The existing solid electrolytes include three types of inorganic solid electrolytes, polymer solid electrolytes and composite solid electrolytes. Among them, the inorganic solid electrolyte is mainly of two types, an oxide solid electrolyte and a sulfide solid electrolyte. The oxide solid electrolyte has good stability, but has the problem of lower ionic conductivity. Sulfide solid electrolytes have high ionic conductivity but poor stability. At present, an inorganic solid electrolyte with good electrochemical stability and high ionic conductivity is not found, and a new solid electrolyte needs to be searched and explored continuously. Lithium-containing cyanamide compounds have never been applied to solid electrolytes. Due to the unique structure of cyanamide compounds similar to oxides, the analogy to LLZO has great potential as a new solid electrolyte.
Disclosure of Invention
The invention aims to provide a solid electrolyte which can solve the technical problems of low ionic conductivity and poor stability of the existing solid electrolyte.
In a first aspect,the invention provides a novel lithium-containing cyanamide compound solid electrolyte. The lithium-containing cyanamide compound solid electrolyte contains lithium ions and cyanamide anions and has a structural general formula of Li 2 M(CN 2 ) 3 (ii) a Wherein M is at least one of positive quadrivalent elements such as Ti, sn, ge, mn, si, zr and the like; preferably, M is Zr.
Preferably, the lithium cyanamide compound-containing solid electrolyte has an ionic conductivity ρ ≧ 1 × 10 -6 mS cm -1 The electrochemical stability window is more than or equal to 4V; the lithium cyanamide compound-containing solid electrolyte does not chemically react with metallic lithium directly.
Preferably, the cyanamide anion [ CN 2 ] 2- Is [ N = C = N ]] 2- Or [ N-C ≡ N ]] 2- Any one of anions. By selecting, as a novel solid electrolyte, a cyanamide compound having properties similar to those of an oxide or sulfide, the cyanamide compound is effective for Li in terms of ion conductivity as compared with an oxide + Is less in binding capacity, is favorable for the conductivity of solid electrolyte and Li + The transference number is increased; in terms of electrochemical stability, cyanamide compounds have a wider voltage window than sulfides and are not easily decomposed during the charge and discharge of a battery.
Preferably, M In the lithium-containing cyanamide compound solid electrolyte is further doped with In 3+ 、La 3+ 、Al 3+ 、B 3+ 、Sb 3+ 、Ga 3+ 、Y 3+ 、La 3+ 、V 3+ 、Ta 5+ 、Nb 5+ At least one of the cations, preferably La 3+ (ii) a The ratio of the amount of the cation-doped substance to the amount of the M substance is 0.01 to 1.
In a second aspect, the present invention provides a method for preparing the above solid electrolyte containing a lithium cyanamide compound, comprising: evenly mixing melamine and lithium nitride, and reacting to obtain Li 2 CN 2 (ii) a The obtained Li 2 CN 2 Mixing with M halide, sealing in quartz tube, and maintaining at 400-900 deg.c for 1 hr-3 days to obtain polymetallic cyanamide compound; the polymetallic cyanamide compound is subjected to cold pressing or pressure sintering or is polymerized withThe compound is compounded to prepare the solid electrolyte of the lithium-containing cyanamide compound.
In a third aspect, the invention provides the use of the above solid electrolyte containing a lithium cyanamide compound in the preparation of a solid lithium battery.
In a fourth aspect, the present invention provides a solid lithium battery comprising a positive electrode sheet, a negative electrode sheet, and an electrolyte layer containing the above-described inorganic solid electrolyte.
Preferably, the specific discharge capacity of the solid-state lithium battery can reach 156mAh/g; the specific capacity of the solid lithium battery can be kept at 90% after the solid lithium battery is stably cycled for 100 circles.
Has the advantages that:
1. the material is applied to the solid-state battery for the first time, the range of the solid-state electrolyte material is widened, the discharge specific capacity of the solid-state lithium battery can at least reach 120mAh/g, and the specific capacity can at least keep 70% after 100 cycles of stable circulation.
2. The material has excellent solid-state battery performance, and is expected to provide help for the development of solid-state electrolytes in the future.
3. The new material is applied to the solid-state battery, and the exploration on the mechanism of the solid-state battery can be deepened.
Drawings
FIG. 1 is the inorganic solid electrolyte Li of example 1 2 Zr(CN 2 ) 3 XRD pattern of (a).
FIG. 2 is the inorganic solid electrolyte Li of example 1 2 Zr(CN 2 ) 3 EIS diagram of (a).
FIG. 3 is the inorganic solid electrolyte Li of example 1 2 Zr(CN 2 ) 3 CV diagram of (a).
Fig. 4 is a graph of the charge and discharge cycle performance of the quasi-solid lithium battery of example 1.
Detailed Description
The present invention is further described below in conjunction with the following embodiments, which are intended to illustrate and not to limit the present invention.
The invention provides a novel lithium-containing cyanamide compound solid electrolyte, which containsHas lithium ion and cyanamide anion and has the capability of lithium ion conduction, and the structural general formula is Li 2 M(CN 2 ) 3 。
The following is a specific embodiment to exemplify a method for producing a lithium-containing cyanamide compound solid electrolyte according to the present invention:
preparation of Li 2 CN 2 . Evenly mixing melamine and lithium nitride according to a certain proportion (2:1), and reacting at 300 ℃ under the protective gas Ar atmosphere to obtain Li 2 CN 2 。
Preparing the polymetallic cyanamide compound material. The obtained Li 2 CN 2 Mixing with M halide, sealing in quartz tube, keeping temperature at 400-900 deg.C for 1 hr-3 days, and filtering to obtain the inorganic solid electrolyte. Need to ensure Li 2 CN 2 The purity is at least 99 percent, and when the purity is lower, a certain amount of melamine needs to be added for re-burning. M is one or more of tetravalent elements such as Ti, sn, ge, mn and Si, and Zr is preferred. The halide of M may be doped with a halide of at least one of In, la, al, B, sb, ga, Y, la, V, ta and Nb.
Obtaining the lithium-containing cyanamide compound solid electrolyte. And (2) carrying out cold pressing or pressure sintering on the polymetallic cyanamide compound or compounding the polymetallic cyanamide compound with a polymer to prepare the lithium-containing cyanamide compound solid electrolyte. As a specific embodiment, the cold pressing is to place the material into the die and press it on the tablet press to 80% of the maximum pressure that the die can withstand. As a specific embodiment, the pressure sintering is sintering by using an SPS machine. As a specific embodiment, the polymer composite can be prepared by a melt-hot-pressing method or a solution casting method.
The invention also provides a solid-state battery which comprises a positive plate, a negative plate and an electrolyte layer, wherein the electrolyte layer contains the inorganic solid-state electrolyte.
The following is an exemplary description of the method of manufacturing a solid state lithium battery according to the present invention.
And (4) preparing the positive plate. The material of the positive plate can be lithium iron phosphate,At least one of lithium cobaltate and lithium titanate. As a specific embodiment, the positive electrode sheet may contain the above-described inorganic solid electrolyte, positive electrode active material, and conductive agent, and the preparation method includes: and adding the inorganic solid electrolyte into the positive electrode material, the solvent and the conductive agent, stirring, and uniformly coating the slurry on the aluminum foil to obtain the positive electrode plate. The method can ensure that the current is uniformly distributed on the surface of the positive plate. The positive electrode active material may be of a kind well known to those skilled in the art, and for example, the positive electrode active material may be selected from LiM 1 PO 4 、Li 2 M 2 SiO 4 、LiAl 1-w Co w O 2 And LiNi x Co y Mn z O 2 At least one of (a); wherein M is 1 And M 2 Each independently selected from at least one of Fe, co, ni and Mn; w is more than 0 and less than or equal to 1; x is more than or equal to 0 and less than or equal to 1,0 and less than or equal to 1,0 and less than or equal to 1. The contents of the inorganic solid electrolyte, the positive electrode active material and the conductive agent can be changed within a wide range, and preferably, the weight ratio of the composite solid electrolyte, the positive electrode active material and the conductive agent can be 1: (0.01-99): (0.01 to 99), preferably 1: (0.01-40): (0.01 to 40), more preferably 1: (0.1-20): (0.1-10). The addition of the inorganic solid electrolyte into the positive plate is beneficial to improving the capacity and the charge-discharge efficiency of the positive plate.
And (4) preparing a negative plate. The negative electrode sheet may contain lithium metal, and the negative electrode sheet may further contain an alloy of lithium and at least one other metal. The at least one other metal in the alloy may be tin, but the kind of alloy is not limited thereto, and an arbitrary metal capable of forming an alloy with lithium metal and a lithium-forming alloy sheet may be used as the negative electrode sheet. In another embodiment of the present invention, the negative electrode sheet may be a sheet composed of a negative electrode material, a conductive agent, and the above-described inorganic solid electrolyte. The preparation method comprises the following steps: and adding the inorganic solid electrolyte into the negative electrode material, the solvent and the conductive agent, stirring, and uniformly coating the slurry on the copper foil to obtain the negative electrode plate. The relative contents of the inorganic solid electrolyte, the negative electrode material and the conductive agent can be changed in a wide range, and preferably, the weight ratio of the inorganic solid electrolyte, the negative electrode material and the conductive agent can be 1: (0.01-99): (0.01 to 99), preferably 1: (0.01-20): (0.01 to 20), more preferably 1: (0.1-10): (0.1-10). The negative plate consisting of the inorganic solid electrolyte, the negative electrode material and the conductive agent in the content range is beneficial to improving the capacity of the solid battery.
A solid state lithium battery is assembled. In the solid-state battery, the inorganic solid electrolyte can be arranged in the electrolyte layer, and the positive plate and the negative plate are in contact with the electrolyte plate after interface treatment, or are in direct contact with the electrolyte plate dropwise added with a trace amount of liquid electrolyte. The methods improve the stability of the contact interface, and enable the current in the solid-state battery to be uniformly distributed, thereby improving the cyclic charge and discharge performance of the solid-state battery. Wherein the assembled battery can be in H environmental condition 2 The content of O is less than 0.5ppm 2 The content is less than 0.5ppm.
And placing the solid electrolyte sheet dropwise added with the trace liquid electrolyte between the positive plate and the negative plate, or assembling the positive plate provided with the inorganic solid electrolyte and the negative plate, or assembling the negative plate provided with the inorganic solid electrolyte and the positive plate to obtain the solid battery.
The present invention will be described in further detail with reference to examples. It is also to be understood that the following examples are illustrative of the present invention and are not to be construed as limiting the scope of the invention, and that insubstantial modifications and adaptations of the invention by those skilled in the art based on the foregoing description are intended to be included within the scope of the invention.
Example 1
(1)Li 2 Zr(CN 2 ) 3 The preparation of (1):
placing 1400g of melamine and 700g of lithium nitride into a mortar in a glove box for grinding, uniformly mixing, placing a boat, slowly heating to 300 ℃ in a CVD furnace, keeping the temperature for 10min, quickly heating to 600 ℃, and naturally cooling to obtain Li 2 CN 2 。
The obtained Li was put into a glove box 2 CN 2 And ZrCl 4 Weighing 0.53g and 2.3g respectively according to stoichiometric ratiog, grinding uniformly, sealing in a quartz tube, keeping the temperature of 500 ℃ in a muffle furnace for 20h, and naturally cooling to obtain Li 2 Zr(CN 2 ) 3 . Carrying out XRD phase test on the sample, analyzing the test result and the standard map, the results are shown in FIG. 1, which illustrates the successful preparation of phase-pure Li 2 Zr(CN 2 ) 3 。
(2) Preparation of solid electrolyte sheet:
0.2g of Li 2 Zr(CN 2 ) 3 The pressure was maintained at low pressure for 1 minute to produce a solid electrolyte sheet (phi 18mm, thickness of about 1 mm).
As shown in FIG. 2, the solid electrolyte of the present example had an ionic conductivity of 2.25X 10 at 28 deg.C -4 S/cm。
Li 2 Zr(CN 2 ) 3 The linear sweep voltammogram of the solid electrolyte is shown in fig. 3, and the electrochemical stability window reaches 4V, which indicates that the electrochemical stability of the electrolyte is good.
(3) Assembling and testing the quasi-solid battery:
assembling the solid electrolyte into a quasi-solid lithium battery: using lithium metal as negative electrode, li 2 Zr(CN 2 ) And (3) assembling the solid electrolyte and 20 mu L of lithium-containing liquid electrolyte into the CR2025 button cell by adding the lithium iron phosphate positive plate.
The constant-current charge and discharge performance test is carried out on a blue battery test system, the charge and discharge multiplying power is 0.05C, the charge and discharge cutoff voltage is 2.8-4.0V (vs. Li/Li +), the test temperature is 28 ℃, the charge and discharge cycle performance of the all-solid-state lithium battery is shown in figure 4, the upper curve represents the coulombic efficiency, the lower curve represents the charge and discharge specific capacity, the first-circle discharge specific capacity reaches 140mAh/g, the specific capacity is kept 86% after 100 circles of stable cycle, and the description shows that Li is used 2 Zr(CN 2 ) 3 The quasi-solid battery with the solid electrolyte as the electrolyte has better specific capacity and cycling stability.
Example 2
(1)Li 2 Zr(CN 2 ) 3 The preparation of (1):
1400g of melamine and 700g of lithium nitride are put into a mortar and ground in a glove box, and after being uniformly mixed, the mixture is put into porcelainThe boat is slowly heated to 300 ℃ in a CVD furnace and is kept warm for 10min, the temperature is rapidly raised to 600 ℃, and the temperature is naturally reduced, thus obtaining the Li 2 CN 2 . The obtained Li was put into a glove box 2 CN 2 And ZrCl 4 Weighing 0.53g and 2.3g according to stoichiometric ratio, grinding uniformly, sealing in a quartz tube, keeping the temperature in a muffle furnace at 500 ℃ for 20h, and naturally cooling to obtain Li 2 Zr(CN 2 ) 3 。
(2) Composite solid electrolyte:
the composite solid electrolyte is prepared by adopting a melting hot pressing method. Polyethylene oxide PEO, li in a glove box 2 Zr(CN 2 ) And LiTFSI according to the mass ratio of 5:4:8, placing the mixture in a vacuum drying oven for 5 hours after fully mixing, then transferring the mixture into a polytetrafluoroethylene mold, and maintaining the pressure for 15min at 80 ℃ and 5MPa to obtain the composite solid polymer electrolyte with the thickness of 70 mu m. The ionic conductivity of the composite solid polymer electrolyte is 5 multiplied by 10 -5 S/cm, the electrochemical stability window reaches 4.5V, which indicates that the electrochemical stability of the electrolyte is good.
(3) Assembling the composite solid-state battery:
assembling the solid electrolyte into a composite solid lithium battery: and the CR2025 button cell is assembled by taking lithium metal as a negative electrode, lithium iron phosphate as a positive electrode and the composite solid electrolyte as an electrolyte. The same constant current charge and discharge performance test as in example 1 was performed, and the test results were: the specific discharge capacity of the first circle reaches 150mAh/g, and the specific capacity is kept 90 percent after 100 circles of stable circulation, which indicates that Li is used 2 Zr(CN 2 ) 3 The quasi-solid battery using the solid electrolyte as the electrolyte has better specific capacity and cycling stability.
Example 3
(1)Li 2 Zr(CN 2 ) 3 The preparation of (1):
placing 1400g of melamine and 700g of lithium nitride into a mortar in a glove box for grinding, uniformly mixing, placing into a porcelain boat, slowly heating to 300 ℃ in a CVD furnace, keeping the temperature for 10min, rapidly heating to 600 ℃, and naturally cooling to obtain Li 2 CN 2 . The obtained Li was put into a glove box 2 CN 2 With ZrCl 4 According to the chemical scaleWeighing according to the weight ratio, grinding uniformly, sealing in a quartz tube, keeping the temperature of 500 ℃ in a muffle furnace for 20h, and naturally cooling to obtain Li 2 Zr(CN 2 ) 3 。
(2) Composite solid electrolyte:
the composite solid polymer electrolyte is prepared by adopting a solution casting method. Polyethylene oxide PEO, li in a glove box 2 Zr(CN 2 )、LiClO 4 According to the mass ratio of 5:4:8 is fully dissolved in acetonitrile, is stirred for 48 hours to obtain uniform viscous solution, is then cast into a polytetrafluoroethylene mold, is dried for 24h, and is dried in vacuum at 25 ℃ for 72 hours to remove residual solvent, so as to obtain the composite solid polymer electrolyte with the thickness of 40 mu m. The ionic conductivity of the composite solid polymer electrolyte is 6 x 10 -5 S/cm, the electrochemical stability window reaches 4.5V, which shows that the electrochemical stability of the electrolyte is good.
(3) Assembling the quasi-solid battery:
assembling the solid electrolyte into a quasi-solid lithium battery: the CR2025 button cell is assembled by taking lithium metal as a negative electrode, lithium iron phosphate as a positive electrode and the composite solid electrolyte and 20 mu L of lithium-containing liquid electrolyte as electrolytes. The same constant current charge and discharge performance test as in example 1 was performed, and the test results were: the specific discharge capacity of the first circle reaches 150mAh/g, and the specific capacity is kept 80% after 100 circles of stable circulation, which indicates that Li is used 2 Zr(CN 2 ) 3 The quasi-solid battery using the solid electrolyte as the electrolyte has better specific capacity and cycling stability.
Example 4
(1)Li 2 Zr(CN 2 ) 3 The preparation of (1):
placing 1400g of melamine and 700g of lithium nitride into a mortar in a glove box for grinding, uniformly mixing, placing into a porcelain boat, slowly heating to 300 ℃ in a CVD furnace, keeping the temperature for 10min, rapidly heating to 600 ℃, and naturally cooling to obtain Li 2 CN 2 . The obtained Li was put into a glove box 2 CN 2 And ZrCl 4 Weighing according to stoichiometric ratio, grinding uniformly, sealing in a quartz tube, keeping the temperature of 500 ℃ in a muffle furnace for 20h, and naturally cooling to obtain Li 2 Zr(CN 2 ) 3 。
(2) Assembling the solid-state battery:
preparation of solid electrolyte sheet:
0.2g of Li 2 Zr(CN 2 ) 3 Cold pressing into a solid electrolyte sheet (phi 18mm, thickness 1 mm). The ion conductivity of the solid electrolyte sheet was 2.25X 10 -4 S/cm, the electrochemical stability window reaches 4.5V, which shows that the electrochemical stability of the electrolyte is good.
Preparing a positive plate:
take 3g of Li 2 Zr(CN 2 ) 3 And 10mL acetonitrile, then stirred for 2h. Then, 6.5g of lithium iron phosphate and 0.5g of acetylene black were added thereto and stirred uniformly to obtain a slurry. Finally, the slurry was uniformly coated on a solid electrolyte sheet. The thickness applied was about 50 μm.
Preparing a negative plate:
and (3) heating the lithium sheet to 250 ℃ in a glove box filled with argon, adding a small amount of carbon powder, placing the prepared solid electrolyte sheet coated with the positive electrode material, and cooling.
Assembling the all-solid-state battery:
and assembling the electrolyte sheet combined with the cathode into the CR2025 button cell. The same constant current charge and discharge performance test as in example 1 was performed, and the test results were: the specific discharge capacity of the first circle reaches 156mAh/g, the specific capacity is kept 88% after stable circulation for 100 circles, which indicates that Li is used 2 Zr(CN 2 ) 3 The quasi-solid battery with the solid electrolyte as the electrolyte has better specific capacity and cycling stability.
Example 5
(1) La-doped Li 2 Zr(CN 2 ) 3 The preparation of (1):
placing 1400g of melamine and 700g of lithium nitride into a mortar in a glove box for grinding, uniformly mixing, placing into a porcelain boat, slowly heating to 300 ℃ in a CVD furnace, keeping the temperature for 10min, rapidly heating to 600 ℃, and naturally cooling to obtain Li 2 CN 2 。
The obtained Li was put into a glove box 2 CN 2 With LaCl 4 ，ZrCl 4 In stoichiometric ratio (7:1.5:3), grinding, sealing in quartz tube, maintaining at 500 deg.C for 20 hr in muffle furnace, and naturally cooling to obtain La-doped Li 2 Zr(CN2) 3 。
(2) Preparation of solid electrolyte sheet:
0.2g of La-doped Li 2 Zr(CN2) 3 Cold pressing into a solid electrolyte sheet (phi 18mm, thickness 1 mm). The solid electrolyte sheet has an ionic conductivity of 7 x 10 -5 S/cm, the electrochemical stability window reaches 4.8V, which shows that the electrochemical stability of the electrolyte is good.
(3) Assembling the quasi-solid battery:
assembling the solid electrolyte into a quasi-solid lithium battery: li doped with La with lithium metal as negative electrode 2 Zr(CN 2 ) And (3) assembling the solid electrolyte and 20 mu L of lithium-containing liquid electrolyte into the CR2025 button cell by adding the lithium iron phosphate positive plate. The same constant current charge and discharge performance test as in example 1 was performed, and the test results were: the specific discharge capacity of the first circle reaches 139mAh/g, and the specific capacity is kept at 70% after 100 circles of stable circulation, which indicates that Li is used 2 Zr(CN 2 ) 3 The quasi-solid battery with the solid electrolyte as the electrolyte has better specific capacity and cycling stability.
Example 6
(1) La-doped Li 2 Zr(CN2) 3 The preparation of (1):
placing 1400g of melamine and 700g of lithium nitride into a mortar in a glove box for grinding, uniformly mixing, placing into a porcelain boat, slowly heating to 300 ℃ in a CVD furnace, keeping the temperature for 10min, rapidly heating to 600 ℃, and naturally cooling to obtain Li 2 CN 2 . The obtained Li was put into a glove box 2 CN 2 With LaCl 4 ，ZrCl 4 Weighing according to a stoichiometric ratio (7 2 Zr(CN 2 ) 3 。
(2) Composite solid electrolyte:
the composite solid electrolyte is prepared by adopting a melting hot pressing method. Polyethylene oxide PEO, la-doped Li in a glove box 2 Zr(CN 2 )、LiClO 4 According to the mass ratio of 5:4:8, placing the mixture in a vacuum drying oven for 5 hours after fully mixing, then transferring the mixture into a polytetrafluoroethylene mold, and maintaining the pressure for 15min at 80 ℃ and 5MPa to obtain the composite solid polymer electrolyte with the thickness of 70 mu m. The ionic conductivity of the composite solid polymer electrolyte is 4 to 10 -5 S/cm, the electrochemical stability window reaches 4.6V, which shows that the electrochemical stability of the electrolyte is good.
(3) Assembling the quasi-solid battery:
assembling the solid electrolyte into a quasi-solid lithium battery: the CR2025 button cell is assembled by taking lithium metal as a negative electrode, lithium iron phosphate as a positive electrode and the composite solid electrolyte and 20 mu L of lithium-containing liquid electrolyte as electrolytes. The same constant current charge and discharge performance test as in example 1 was performed, and the test results were: the specific discharge capacity of the first circle reaches 144mAh/g, and the specific capacity is kept at 70% after 100 circles of stable circulation, which indicates that Li is used 2 Zr(CN 2 ) 3 The quasi-solid battery with the solid electrolyte as the electrolyte has better specific capacity and cycling stability.
Example 7
(1) La-doped Li 2 Zr(CN 2 ) 3 The preparation of (1):
placing 1400g of melamine and 700g of lithium nitride in a glove box to be ground in a mortar, uniformly mixing, placing in a porcelain boat, slowly heating to 300 ℃ in a CVD furnace, preserving heat for 10min, rapidly heating to 600 ℃, and naturally cooling to obtain Li2CN2. The obtained Li was put into a glove box 2 CN 2 With LaCl 4 ，ZrCl 4 Weighing according to a stoichiometric ratio (7 2 Zr(CN 2 ) 3 。
(2) Composite solid electrolyte:
the composite solid polymer electrolyte is prepared by adopting a solution casting method. Polyethylene oxide PEO, la-doped Li in a glove box 2 Zr(CN 2 )、LiClO 4 According to the mass ratio of 5:4:8 is fully dissolved in acetonitrile, stirred for 48 hours to obtain uniform viscous solution, then the uniform viscous solution is cast into a polytetrafluoroethylene mold and dried for 24h, and vacuum drying is carried out for 72 hours at the temperature of 25 DEG CThe residual solvent was removed to obtain a composite solid polymer electrolyte having a thickness of 40 μm. The ionic conductivity of the composite solid polymer electrolyte is 7 x 10 -5 S/cm, the electrochemical stability window reaches 4.8V, which shows that the electrochemical stability of the electrolyte is good.
(3) Assembling the quasi-solid battery:
assembling the solid electrolyte into a quasi-solid lithium battery: the CR2025 button cell is assembled by taking lithium metal as a negative electrode, lithium iron phosphate as a positive electrode and the composite solid electrolyte and 20 mu L of lithium-containing liquid electrolyte as electrolytes. The same constant current charge and discharge performance test as in example 1 was performed, and the test results were: the specific discharge capacity of the first circle reaches 150mAh/g, and the specific capacity is maintained by 78 percent after 100 circles of stable circulation, which indicates that Li is used 2 Zr(CN 2 ) 3 The quasi-solid battery with the solid electrolyte as the electrolyte has better specific capacity and cycling stability.
Example 8
(1) La-doped Li 2 Zr(CN 2 ) 3 The preparation of (1):
placing 1400g of melamine and 700g of lithium nitride into a mortar in a glove box for grinding, uniformly mixing, placing into a porcelain boat, slowly heating to 300 ℃ in a CVD furnace, keeping the temperature for 10min, rapidly heating to 600 ℃, and naturally cooling to obtain Li 2 CN 2 . The obtained Li was put into a glove box 2 CN 2 With LaCl 4 ，ZrCl 4 Weighing according to a stoichiometric ratio (7 2 Zr(CN 2 ) 3 。
(2) Preparing an all-solid-state battery:
preparation of solid electrolyte sheet:
0.2g of La-doped Li 2 Zr(CN 2 ) 3 Cold pressing into a solid electrolyte sheet (phi 18mm, thickness 1 mm). The solid electrolyte sheet has an ionic conductivity of 5 x 10 -6 S/cm, the electrochemical stability window reaches 4.6V, which shows that the electrochemical stability of the electrolyte is good.
Preparing a positive plate:
taking 3g of La-doped Li 2 Zr(CN 2 ) 3 And 10mL acetonitrile, then stirred for 2h. Then, 6.5g of lithium iron phosphate and 0.5g of acetylene black were added thereto and stirred uniformly. Finally, the slurry was uniformly coated on a solid electrolyte sheet. The thickness applied was about 50 μm.
Preparing a negative plate:
and (3) heating the lithium sheet to 250 ℃ in a glove box filled with argon, adding a small amount of carbon powder, placing the prepared solid electrolyte sheet coated with the positive electrode material, and cooling.
Assembling the all-solid-state battery:
and assembling the electrolyte sheet combined with the cathode into the CR2025 button cell. The same constant current charge and discharge performance test as in example 1 was performed, and the test results were: the specific discharge capacity of the first circle reaches 140mAh/g, and the specific capacity is kept 86% after 100 circles of stable circulation, which indicates that Li is used 2 Zr(CN 2 ) 3 The quasi-solid battery with the solid electrolyte as the electrolyte has better specific capacity and cycling stability.
Example 9
(1)Li 2 Sn(CN 2 ) 3 The preparation of (1):
placing 1400g of melamine and 700g of lithium nitride into a mortar in a glove box for grinding, uniformly mixing, placing a boat, slowly heating to 300 ℃ in a CVD furnace, keeping the temperature for 10min, quickly heating to 600 ℃, and naturally cooling to obtain Li 2 CN 2 。
The obtained Li was put into a glove box 2 CN 2 With SnCl 4 Weighing 0.53g and 2.3g according to stoichiometric ratio, grinding uniformly, sealing in a quartz tube, keeping the temperature of 500 ℃ in a muffle furnace for 20h, and naturally cooling to obtain Li 2 Sn(CN 2 ) 3 . Carrying out XRD phase test on the sample, analyzing the test result and the standard map, the results are shown in FIG. 1, which illustrates the successful preparation of phase-pure Li 2 Sn(CN 2 ) 3 。
(2) Preparation of solid electrolyte sheet:
0.2g of Li 2 Sn(CN 2 ) 3 The low pressure maintaining pressure being one-half Zhong Zhicheng (phi 18mm, thickness about 1 mm)A solid electrolyte sheet.
The solid electrolyte of this example had an ionic conductivity of 8X 10 at 28 deg.C -6 S/cm。
Li 2 Sn(CN 2 ) 3 The electrochemical stability window of the solid electrolyte reaches 4V, which indicates that the electrochemical stability of the electrolyte is good.
(3) Assembling and testing the quasi-solid battery:
assembling the solid electrolyte into a quasi-solid lithium battery: using lithium metal as the negative electrode, li 2 Sn(CN 2 ) And (3) assembling the solid electrolyte and 20 mu L of lithium-containing liquid electrolyte into the CR2025 button cell by adding the lithium iron phosphate positive plate.
The constant-current charge and discharge performance test is carried out on a blue battery test system, the charge and discharge multiplying power is 0.05C, the charge and discharge cutoff voltage is 2.8-4.0V (vs. Li/Li +), the test temperature is 28 ℃, the first-circle discharge specific capacity reaches 120mAh/g, the specific capacity is kept at 70% after 100 circles of stable circulation, and the result shows that the Li is used for testing the constant-current charge and discharge performance of the blue battery 2 Sn(CN 2 ) 3 The quasi-solid battery with the solid electrolyte as the electrolyte has better specific capacity and cycling stability.
Example 10
(1) Al-doped Li 2 Zr(CN 2 ) 3 The preparation of (1):
placing 1400g of melamine and 700g of lithium nitride into a mortar in a glove box for grinding, uniformly mixing, placing into a porcelain boat, slowly heating to 300 ℃ in a CVD furnace, keeping the temperature for 10min, rapidly heating to 600 ℃, and naturally cooling to obtain Li 2 CN 2 。
The obtained Li was put into a glove box 2 CN 2 With AlCl 3 ，ZrCl 4 Weighing according to a stoichiometric ratio (7 2 Zr(CN2) 3 。
(2) Preparation of solid electrolyte sheet:
0.2g of Al-doped Li 2 Zr(CN2) 3 Cold pressing into a solid electrolyte sheet (phi 18mm, thickness 1 mm). The solid electrolyte sheet has an ionic conductivity of 8.2 x 10 -5 S/cm, the electrochemical stability window reaches 4.5V, which shows that the electrochemical stability of the electrolyte is good.
(3) Assembling the quasi-solid battery:
assembling the solid electrolyte into a quasi-solid lithium battery: li doped with La and using lithium metal as negative electrode 2 Zr(CN 2 ) And (3) assembling the solid electrolyte and 20 mu L of lithium-containing liquid electrolyte into the CR2025 button cell by adding the lithium iron phosphate positive plate. The same constant current charge and discharge performance test as in example 1 was performed, and the test results were: the specific discharge capacity of the first circle reaches 130mAh/g, and the specific capacity is kept at 70% after 100 circles of stable circulation, which indicates that Li is used 2 Zr(CN 2 ) 3 The quasi-solid battery with the solid electrolyte as the electrolyte has better specific capacity and cycling stability.

Claims (8)

1. The solid electrolyte of the lithium-containing cyanamide compound is characterized by containing lithium ions and cyanamide anions and having a structural general formula of Li 2 M(CN 2 ) 3 (ii) a Wherein M is at least one of positive quadrivalent elements of Ti, sn, ge, mn, si and Zr; preferably, M is Zr.
2. The solid electrolyte containing a lithium cyanamide compound according to claim 1, wherein the solid electrolyte containing a lithium cyanamide compound has an ionic conductivity ρ ≧ 1 x 10 -6 mS cm -1 The electrochemical stability window is more than or equal to 4V, and the lithium-containing cyanamide compound solid electrolyte does not directly undergo chemical reaction with metallic lithium.
3. The lithium-containing cyanamide compound solid electrolyte according to claim 1 or 2, characterized in that the cyanamide anion [ CN 2 ] 2- Is [ N = C = N ]] 2- Or [ N-C ≡ N] 2- Any one of anions.
4. The solid electrolyte containing a lithium cyanamide compound according to any one of claims 1 to 3, wherein M In the solid electrolyte is further doped with In 3+ 、La 3+ 、Al 3+ 、B 3+ 、Sb 3+ 、Ga 3+ 、Y 3+ 、La 3+ 、V 3+ 、Ta 5+ 、Nb 5+ At least one of the cations, preferably La 3+ (ii) a The ratio of the amount of the cation-doped substance to the amount of the M substance is 0.01 to 1.
5. The method for producing the lithium-containing cyanamide compound solid electrolyte according to any one of claims 1 to 4, comprising: evenly mixing melamine and lithium nitride, and reacting to obtain Li 2 CN 2 (ii) a The obtained Li 2 CN 2 Mixing with M halide, sealing in quartz tube, and maintaining at 400-900 deg.c for 1 hr-3 days to obtain polymetallic cyanamide compound; and (2) carrying out cold pressing or pressure sintering on the polymetallic cyanamide compound or compounding the polymetallic cyanamide compound with a polymer to prepare the lithium-containing cyanamide compound solid electrolyte.
6. Use of the solid electrolyte containing a lithium cyanamide compound according to any one of claims 1-4 for the preparation of a solid lithium battery.
7. A solid lithium battery comprising a positive electrode sheet, a negative electrode sheet, and an electrolyte layer containing the inorganic solid electrolyte according to any one of claims 1 to 4.
8. The lithium solid state battery of claim 7, wherein the lithium solid state battery has a specific discharge capacity of up to 156mAh/g; the specific capacity of the solid lithium battery can be kept at 90% after the solid lithium battery is stably cycled for 100 circles.
CN202110616399.6A 2021-06-02 2021-06-02 Lithium-containing cyanamide compound solid electrolyte, preparation method and application thereof, and solid lithium battery Pending CN115441046A (en)

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