CN113937291B - Electrode material for sulfide all-solid-state battery and preparation method thereof - Google Patents
Electrode material for sulfide all-solid-state battery and preparation method thereof Download PDFInfo
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Abstract
The invention belongs to the technical field of batteries, and discloses an electrode material for a sulfide all-solid-state battery and a preparation method thereof. After the electrode material and the sulfide solid electrolyte and other materials are combined into the solid-state battery, the ionic liquid can be filled in a nanometer gap in the solid-state battery, so that the gap between the sulfide solid electrolyte and the electrode material is filled, the crystal boundary between the electrolytes is reduced, the internal density of the battery is improved, and the effective contact area between the electrode material and the electrolyte is improved, wherein the lithium ion ionization agent can be absorbed into the gap in the battery by virtue of the ionic liquid, and the conduction contact surface of lithium ions is increased, so that the interface impedance among the materials in the battery is reduced, and the cycle stability and the service life of the battery are improved.
Description
Technical Field
The invention belongs to the technical field of batteries, and particularly relates to an electrode material for a sulfide all-solid-state battery and a preparation method thereof.
Background
Currently, sulfide solid-state electrolytes have received much attention due to their high ionic conductivity. However, sulfide solid electrolytes themselves generate a large number of micropores (the pore diameter is less than 100 nm) in the sintering process, so that the density of the sulfide solid electrolyte directly cold pressed is low (< 98%), and the ionic conductivity of the electrolyte itself is reduced. On the other hand, the traditional oxide positive electrode and other negative electrodes have large elastic modulus and poor deformability, so that the contact between the sulfide solid electrolyte and the electrode material is poor, the effective contact area is less than 95%, the interface impedance is increased, the battery performance is damaged, and particularly under high-rate circulation, the energy density of the battery is reduced.
In addition, each material has different volume changes in the battery cycle process, and the solid electrolyte and the electrode material are both solid and can not flow, so that the microcracks in the battery are easily caused, and the battery is damaged.
In the prior art, the internal density of the battery is improved mainly by hot/cold isostatic pressing. And aiming at the volume change inside the battery, a method of pressurizing (> 50 MPa) in the battery circulation process is mainly adopted. However, the hot/cold isostatic pressing method has the following problems: on the one hand, the equipment is expensive; the treatment process is complex; the processing monomer is small, and the industrial application difficulty is high. On the other hand, even if the method is adopted, the contact area between the electrode materials is difficult to increase, the interface impedance is still large, and the method is not suitable for the development planning of high-performance batteries. The method of pressurizing the battery can ensure the circulation of the battery, but also increases the cost of the rigid body of the battery, most importantly, reduces the energy density of the whole battery, and is not beneficial to the development of the solid-state battery.
Disclosure of Invention
The present invention is directed to solving at least one of the problems of the prior art described above. Therefore, the invention provides an electrode material, which can improve the effective contact area between the electrode material and an electrolyte, reduce the interface impedance between the electrode material and the electrolyte, and improve the cycle stability and the service life of a battery.
The invention provides an electrode material, which comprises an electrode material substrate and a composite ionic liquid layer coated on the surface of the electrode material substrate, wherein the composite ionic liquid layer comprises ionic liquid and lithium ion ionization agent.
The applicant of the invention finds in research that after the surface of an electrode material matrix is coated with ionic liquid and a lithium ion ionization agent, a composite ionic liquid layer is formed on the surface of the electrode material matrix to obtain an electrode material, and the electrode material and sulfide solid electrolyte and other materials are combined into a solid battery, the ionic liquid can be filled in nano gaps in the solid battery to make up gaps between the sulfide solid electrolyte and the electrode material, so that the crystal boundary between the electrolytes is reduced, the density in the battery is improved, and the effective contact area between the electrode material and the sulfide solid electrolyte is increased; meanwhile, the lithium ion agent can provide lithium ions, so that the composite ionic liquid has certain lithium ion conductivity, the lithium ion conductivity between an electrode material and an electrolyte is improved, and the interface impedance of the battery is reduced.
The ionic liquid adopted by the invention is different from a common electrolyte solvent, the common electrolyte solvent has strong polarity and is easy to react with the sulfide solid electrolyte to damage the sulfide solid electrolyte, and meanwhile, the common electrolyte solvent has low boiling point, is easy to burn and has low safety and does not meet the requirement of high safety of a solid battery.
Preferably, the electrode material matrix is a positive electrode material or a negative electrode material, and the positive electrode material comprises sulfur and Li 2 CoO 2 、Li 2 Ni 0.33 Co 0.33 Mn 0.33 O 2 、Li 2 Ni 0.6 Co 0.2 Mn 0.2 O 2 、Li 2 Ni 0.8 Co 0.1 Mn 0.1 O 2 In view of energy density of the battery and cost of the positive electrode material, it is more preferable that the positive electrode material employs Li having higher energy density 2 Ni 0.6 Co 0.2 Mn 0.2 O 2 Or Li 2 Ni 0.8 Co 0.1 Mn 0.1 O 2 As a positive electrode material. The negative electrode material includes at least one of lithium powder, graphite, and lithium titanate, and in consideration of energy density of the battery, it is more preferable that the negative electrode material employs lithium powder or graphite having higher energy density.
Preferably, the ionic liquid comprises a cation and an anion, the cation comprising [ EMIM] + (1-ethyl-3-methylimidazolium ion), [ PMPep] + (N-propyl-N-methylpiperidine amine ion), [ TMPA ]] + (Trimethylpropylammonium ion) and [ TEA] + (tetraethylammonium) and the anion comprises BF 4 - 、(CF 3 SO 2 ) 2 N - And PF 6 - One or more of (a).
Preferably, the ionic liquid is coated on the surface of the cathode material, and the cation of the ionic liquid adopts [ EMIM] + 、[PMPip] + At least one of (1) and (b) as an anion, BF is used 4 - 、PF 6 - At least one of (1). Considering the electrochemical window of the anode material, the electrochemical window space is required to be more than 4.5V, the material viscosity is less, and more preferably, the cation of the ionic liquid adopts [ EMIM] + The anion is BF 4 - 。
Preferably, the ionic liquid coated on the surface of the negative electrode material adopts [ TMPA ] as the cation of the ionic liquid] + 、[TEA] + Wherein the anion is (CF) 3 SO 2 ) 2 N - . Considering the electrochemical window of the anode material, the electrochemical window space is required to be less than 0.1V, the material viscosity is less, and more preferably, the cation of the ionic liquid adopts [ TMPA [ ]] + The anion is (CF) 3 SO 2 ) 2 N - 。
Preferably, the lithium ion ionization agent comprises LiBF 4 、Li(CF 3 SO 2 ) 2 N and LiPF 6 One or more of (a).
Preferably, the surface of the electrode material substrate is further coated with a nano layer, the nano layer is positioned between the electrode material substrate and the composite ionic liquid layer, and the composition of the nano layer comprises Li 2 Zr(PO 4 ) 2 、LiNbO 3 And Li 2 WO 4 One or more of (a). The nano-layer adopts LiNbO as a component in consideration of the ionic conductivity and electrochemical impedance of the nano-layer 3 The thickness of the nanolayer is preferably 5-20nm.
The second aspect of the present invention provides a method for preparing the electrode material, comprising the steps of:
and mixing the ionic liquid and the lithium ion ionization agent to obtain composite ionic liquid, and coating the electrode material substrate by adopting the composite ionic liquid to obtain the electrode material.
Preferably, the concentration of the lithium ion ionization agent in the composite ionic liquid is 0.1 to 1mol/L, and more preferably, the concentration of the lithium ion ionization agent is 0.2 to 0.5mol/L in view of the viscosity and the lithium ion conductivity of the composite ionic liquid.
Preferably, before the coating treatment of the electrode material substrate by using the composite ionic liquid, the method further comprises a pretreatment step, wherein the pretreatment step comprises the following steps: with Li 2 Zr(PO 4 ) 2 、LiNbO 3 And Li 2 WO 4 The electrode material substrate is subjected to coating treatment.
Preferably, the coating treatment includes spray drying, atomic vapor deposition, stirring thermal evaporation, or planetary ball milling, and it is preferable to perform coating using a spray drying method in consideration of the cost of coating and uniformity of coating.
A third aspect of the invention provides the use of the electrode material in a battery, in particular a solid-state battery.
Preferably, a solid-state battery includes an electrolyte and the electrode material of the present invention.
Preferably, the electrolyte is a sulfide solid state electrolyte.
Preferably, the sulfide solid electrolyte is Li 3 PS 4 、Li 4 P 2 S 6 Or Li 7-a PS 6-a Y a Wherein: y is at least one of Cl, br and I, and a is more than or equal to 0.5 and less than or equal to 2.
Preferably, the particle size of the sulfide solid electrolyte is 0.5-5um, so that the solid battery is conveniently pressed and formed, and the density of a battery block is improved.
Preferably, the electrolyte is coated with the composite ionic liquid of the present invention.
Compared with the prior art, the invention has the following beneficial effects:
the electrode material of the invention is characterized in that the surface of the electrode material matrix is coated with a composite ionic liquid layer, the components of the composite ionic liquid layer comprise ionic liquid and lithium ion ionization agent, the compactness of the electrode material is improved (the compactness reaches more than 90%), after the electrode material and sulfide solid electrolyte and other materials are combined into a solid battery, the ionic liquid can be filled in nano gaps in the solid battery, the gaps between the sulfide solid electrolyte and the electrode material are made up, the crystal boundary between the electrolytes is reduced, the effective contact area between the electrode material and the electrolyte is improved (the effective contact area reaches more than 95%), wherein the lithium ion ionization agent can be absorbed into the gaps in the battery by means of the ionic liquid, and the conduction contact surface of lithium ions is increased,thereby reducing the interface impedance between the materials in the battery (the interface impedance reaches 10 omega/cm) 2 Below), the cycle stability and life of the battery are improved. More importantly, the flowing composite ionic liquid can play a role in buffering when the volume of the battery changes, so that the test pressure of the battery can be further reduced, and the energy density of a subsequent sulfide all-solid-state battery pack is increased.
Detailed Description
In order to make the technical solutions of the present invention more apparent to those skilled in the art, the following examples are given for illustration. It should be noted that the following examples are not intended to limit the scope of the claimed invention.
The starting materials, reagents or apparatuses used in the following examples are conventionally commercially available or can be obtained by conventionally known methods, unless otherwise specified. The particle size of the electrolyte may be processed by a ball mill, a sand mill or a jet mill. The constant temperature control can adopt a tubular electric furnace.
Example 1
An electrode material comprises a positive electrode material and a composite ionic liquid layer coated on the surface of the positive electrode material, wherein the composite ionic liquid layer comprises ionic liquid and a lithium ion ionization agent. Wherein the positive electrode material is Li 2 Ni 0.8 Co 0.1 Mn 0.1 O 2 The ionic liquid is [ EMIM]BF 4 The lithium ion ionization agent is LiBF 4 。
The preparation method of the electrode material comprises the following steps:
1) 0.25mol/L LiBF is added 4 And [ EMIM ]]BF 4 Mixing to obtain LiBF 4 -[EMIM]BF 4 Compounding ionic liquid, adding 20 times volume of absolute ethyl alcohol, and diluting LiBF 4 -[EMIM]BF 4 Compounding the ionic liquid to obtain the anode coating agent.
2) Using LiNbO 3 For Li 2 Ni 0.8 Co 0.1 Mn 0.1 O 2 (NCM 811) coating: using a tubular fluidised bed for Li 2 Ni 0.8 Co 0.1 Mn 0.1 O 2 Continuously rolling and suspending on the air flow, and spraying LiNbO 3 Coating the raw material to finally obtain LiNbO 3 -Li 2 Ni 0.8 Co 0.1 Mn 0.1 O 2 The precursor (LNO-NCM 811 precursor) is placed in an oxygen sintering furnace to be sintered for 6h at 350 ℃ to obtain the LiNbO coated surface 3 Nanolayered Li 2 Ni 0.8 Co 0.1 Mn 0.1 O 2 (LNO-NCM811)。
3) Putting the LNO-NCM811 obtained in the step 2) into a tubular fluidized bed to enable the LNO-NCM811 to roll continuously and suspend on the air flow, spraying the anode coating agent obtained in the step 1) into the tubular fluidized bed in a high-pressure spraying mode to enable the surface of the LNO-NCM811 to be coated with a layer of nano liquid drops, meanwhile, directly heating a sleeve on the pipe wall in the spraying coating process to maintain the coating temperature at about 120 ℃, and finally obtaining the LiBF coated coating 4 -[EMIM]BF 4 LiNbO of composite ionic liquid nano-layer 3 -Li 2 Ni 0.8 Co 0.1 Mn 0.1 O 2 Electrode material (LEBF-LNO-NCM 811).
According to the mass ratio of 82:15:3 weighing LEBF-LNO-NCM811 (Experimental group 1) prepared in the example, NCM811 (control group 1) without composite ionic liquid coating, and Li 6 PS 5 And grinding the Cl solid electrolyte and the VGCF conductive carbon for 10min to respectively prepare the composite anode of the experimental group 1 and the composite anode of the control group 1. According to the mass ratio of 70:27:3 weighing LEBF-LNO-NCM811 (experiment group 2) prepared in the example, NCM811 (control group 2) without composite ionic liquid coating, and Li 6 PS 5 And grinding the Cl solid electrolyte and the VGCF conductive carbon for 10min to respectively prepare the composite anode of the experimental group 2 and the composite anode of the control group 2. 30mg of each composite positive electrode and 120mg of sulfide solid electrolyte are respectively pressed into a battery assembly with the diameter of 10mm, 200umLi-In metal foil is used as a negative electrode to assemble a sulfide all-solid battery, and electrochemical performance test is carried out. The test conditions were: the current is 0.3C multiplying power, the voltage range is 2.4-3.7V (3.0-4.3 Vvs. Li +/Li), the battery test pressure is less than 5MPa at 25 ℃, the cycle is 100 weeks, and the test comparison results are shown in Table 1.
TABLE 1
As can be seen from Table 1, the use of the LiBF coating 4 -[EMIM]BF 4 LiNbO of composite ionic liquid nano-layer 3 -Li 2 Ni 0.8 Co 0.1 Mn 0.1 O 2 At conventional mixing ratios (experimental group 2) compared to uncoated LiNbO 3 -Li 2 Ni 0.8 Co 0.1 Mn 0.1 O 2 (control group 2), the interface impedance of the positive electrode is obviously reduced, the first-turn efficiency of the battery is obviously improved, and the capacity retention aspect of one hundred turns is more stable. In order to improve the energy density of the sulfide all-solid-state battery, the proportion of the electrode material in the composite positive electrode is further increased from 70 percent to 82 percent, and the LiBF is coated 4 -[EMIM]BF 4 LiNbO of composite ionic liquid nano-layer 3 -Li 2 Ni 0.8 Co 0.1 Mn 0.1 O 2 The energy density of the positive electrode of the experimental group 2 is increased from 550Wh/Kg to 602Wh/Kg of the experimental group 1, and the energy retention rate of one hundred turns is not obviously reduced; but uncoated LiNbO 3 -Li 2 Ni 0.8 Co 0.1 Mn 0.1 O 2 (control group 1), after the proportion of the electrode material in the composite positive electrode is increased, the interfacial impedance of the positive electrode is obviously increased compared with that of the control group 2, and the normal capacity is difficult to release, so that the energy density of the positive electrode of the control group 1 is not improved, but is reduced. Therefore, the cathode material coated with the composite ionic liquid nano layer has the advantages that the interface impedance of the cathode is obviously reduced, meanwhile, the proportion of the electrode material can be further improved, the energy of the electrode material can be well released, the energy density of the cathode is further improved, the construction of a high-energy-density sulfide all-solid-state battery is facilitated, the capacity retention rate of the battery is high, and the cycle stability and the service life of the battery are favorably improved.
In addition, the density of the positive electrodes respectively prepared by the experimental group 1, the control group 1, the experimental group 2 and the control group 2 is respectively 93%, 85%, 95% and 87% by adopting cyclohexane as calibration liquid through an Archimedes drainage method, and the density of the electrode material can be obviously improved after the composite ionic liquid layer is coated on the surface of the electrode material matrix. According to the test of the BET specific surface area test method, the effective contact areas of the positive electrode and the electrolyte in the sulfide all-solid-state batteries respectively prepared from the experimental group 1, the comparison group 1, the experimental group 2 and the comparison group 2 are respectively 95.6%, 90.1%, 96.2% and 90.8%.
Example 2
An electrode material comprises a negative electrode material and a composite ionic liquid layer coated on the surface of the negative electrode material, wherein the composite ionic liquid layer comprises ionic liquid and a lithium ion ionization agent. Wherein the cathode material is lithium powder, and the ionic liquid is [ TMPA ]](CF 3 SO 2 ) 2 N, li (CF) as lithium ion ionization agent 3 SO 2 ) 2 N。
The preparation method of the electrode material comprises the following steps:
1) 0.3mol/L of Li (CF) 3 SO 2 ) 2 N and [ TMPA ]](CF 3 SO 2 ) 2 N are mixed to obtain Li (CF) 3 SO 2 ) 2 N-[TMPA](CF 3 SO 2 ) 2 N compounding with ionic liquid, adding 20 times volume of anhydrous DMF (N, N-dimethylformamide), and diluting Li (CF) 3 SO 2 ) 2 N-[TMPA](CF 3 SO 2 ) 2 And compounding the N with the ionic liquid to obtain the cathode coating agent.
2) Putting lithium powder into a tubular fluidized bed, enabling the lithium powder to continuously roll and suspend on air flow, spraying the negative coating agent obtained in the step 1) into the tubular fluidized bed in a high-pressure spraying mode, enabling the surface of the lithium powder to be coated with a layer of nano liquid drops, meanwhile, directly heating the pipe wall by using a sleeve in the spraying coating process, keeping the coating temperature at about 80 ℃, and finally obtaining the Li-Coated (CF) material 3 SO 2 ) 2 N-[TMPA](CF 3 SO 2 ) 2 And (3) a lithium powder electrode material (LTCN coated lithium powder) of the N composite ionic liquid nanolayer.
According to the mass ratio of 70:27:3 weighing common NCM811 and Li 6 PS 5 And grinding the Cl solid electrolyte and VGCF conductive carbon for 10min to prepare the composite anode. Simultaneously according to the following steps of 80:18:2 weighing the LTCN coated lithium powder (experimental group 3) or the common lithium powder (control group 3) prepared in the embodiment, and Li 6 PS 5 And mixing the Cl solid electrolyte and VGCF conductive carbon for 10min to prepare the corresponding composite cathode. 30mg of composite positive electrode and 120mg of sulfide solid electrolyte are respectively pressed into a battery component with the diameter of 10mm, 2mg of composite negative electrode is used as a negative electrode to assemble a sulfide all-solid battery, and electrochemical performance test is carried out. The test conditions were: the current is 0.3C multiplying power, the voltage range is 3.0-4.3 Vvs. Li +/Li, the temperature is 25 ℃, the test pressure of the battery is less than 5MPa, the cycle is 100 weeks, and the test comparison results are shown in Table 2.
TABLE 2
As can be seen from Table 2, a coating with Li (CF) is used 3 SO 2 ) 2 N-[TMPA](CF 3 SO 2 ) 2 The lithium powder electrode material (LTCN coated lithium powder) of the N composite ionic liquid nanolayer is used as a negative electrode (experiment group 3), so that the negative electrode interface impedance of the all-solid-state battery can be reduced, the interface side reaction is inhibited, the effective contact area of the electrode is increased, and the normal long circulation of the battery can be ensured. While the direct use of the general lithium powder (control 3) as a negative electrode increased side reactions between metallic lithium and an electrolyte and caused a rapid short circuit of the battery. Thus, it is described that Li (CF) is coated 3 SO 2 ) 2 N-[TMPA](CF 3 SO 2 ) 2 The impedance of the lithium powder electrode material of the N composite ionic liquid nanolayer is obviously reduced, meanwhile, the long circulation of the battery can be ensured, the growth of lithium dendrites is effectively inhibited, the construction of a sulfide all-solid-state battery with high energy density is facilitated, the capacity retention rate of the battery is high, and the lithium powder electrode material is beneficial toThe cycling stability and the service life of the battery are improved.
Example 3
An electrode material comprises a positive electrode material, a negative electrode material and a composite ionic liquid layer coated on the surfaces of the positive electrode material and the negative electrode material, wherein the composite ionic liquid layer comprises ionic liquid and a lithium ion ionization agent. Wherein the cathode material is Li 2 CoO 2 The cathode material is graphite powder, and the ionic liquid is [ EMIM ]]PF 6 And [ TMPA ]](CF 3 SO 2 ) 2 N, li (CF) as lithium ion ionization agent 3 SO 2 ) 2 N。
The preparation method of the electrode material comprises the following steps:
1) 0.2mol/L of Li (CF) 3 SO 2 ) 2 N and [ EMIM]PF 6 Mixing to obtain Li (CF) 3 SO 2 ) 2 N-[EMIM]PF 6 Compounding ionic liquid, adding 20 times volume of anhydrous ethanol, and diluting Li (CF) 3 SO 2 ) 2 N-[EMIM]PF 6 Compounding the ionic liquid to obtain the anode coating agent.
2) 0.2mol/L of Li (CF) 3 SO 2 ) 2 N and [ TMPA ]](CF 3 SO 2 ) 2 N are mixed to obtain Li (CF) 3 SO 2 ) 2 N-[TMPA](CF 3 SO 2 ) 2 N compounding with ionic liquid, adding 20 times volume of anhydrous ethanol, and diluting Li (CF) 3 SO 2 ) 2 N-[TMPA](CF 3 SO 2 ) 2 And compounding the N with the ionic liquid to obtain the cathode coating agent.
3) By means of a tubular fluidized bed with Li 2 Zr(PO 4 ) 2 For Li 2 CoO 2 Coating is carried out to obtain Li 2 Zr(PO 4 ) 2 -Li 2 CoO 2 。
4) Respectively spraying the anode coating agent and the cathode coating agent obtained in the steps 1) and 2) into a fluidized bed in a high-pressure spraying mode, so that Li 2 Zr(PO 4 ) 2 -Li 2 CoO 2 And the surface of the graphite powder is respectively coated with a layer of nano liquid drop, and simultaneouslyIn the spray coating process, the tube wall is directly heated by a sleeve, the coating temperature is maintained at about 120 ℃, and finally the coating with Li (CF) is obtained 3 SO 2 ) 2 N-[EMIM]PF 6 Li of composite ionic liquid nano-layer 2 Zr(PO 4 ) 2 -Li 2 CoO 2 Electrode material (LEP-LZP-LCO) and Li Cladding (CF) 3 SO 2 ) 2 N-[TMPA](CF 3 SO 2 ) 2 N composite ionic liquid nanolaminated graphite powder (LTN-C).
According to the mass ratio of 82:15:3 weighing LEP-LZP-LCO (Experimental group 4) or common Li prepared in this example 2 CoO 2 (control group 4), li 6 PS 5 And grinding the Cl solid electrolyte and VGCF conductive carbon for 10min to prepare the composite anode. Simultaneously according to the following steps of 80:18:2 weighing the LTN-C or common graphite powder and Li prepared in the embodiment 6 PS 5 And mixing the Cl solid electrolyte and VGCF conductive carbon for 10min to obtain the corresponding composite cathode. 30mg of composite positive electrode and 120mg of sulfide solid electrolyte are respectively pressed into a battery component with the diameter of 10mm, a 15mg composite negative electrode is used as a negative electrode to assemble a sulfide all-solid battery, and electrochemical performance test is carried out. The test conditions were: the current is 0.3C multiplying power, the voltage range is 2.9-4.2V (3.0-4.3 Vvs. Li +/Li), the battery test pressure is less than 5MPa at 25 ℃, the cycle is 100 weeks, and the test comparison results are shown in Table 3.
TABLE 3
As can be seen from table 3, the method of coating the positive electrode and the negative electrode in both directions (experimental group 4) can reduce the interface impedance of the sulfide all-solid-state battery, suppress the interface side reaction, increase the effective contact area of the electrode, and ensure the normal long cycle of the battery. While the common electrode material Li 2 CoO 2 And graphite powder (control group 4) directly used as the positive electrode and the negative electrode, side reactions between the lithium metal and the electrolyte are increased, and not only can the whole specific capacity of the positive electrode not be exerted, but also the rapid attenuation of the battery capacity is caused. Therefore, the impedance of the anode material and the cathode material coated with the composite ionic liquid nano layer is obviously reduced, the long circulation of the battery can be ensured, the construction of a high-energy-density sulfide all-solid-state battery is facilitated, the capacity retention rate of the battery is high, and the cycle stability and the service life of the battery are improved.
Example 4 (different from example 1 in that the surface of the positive electrode material is not coated with LiNbO) 3 )
An electrode material comprises a positive electrode material and a composite ionic liquid layer coated on the surface of the positive electrode material, wherein the composite ionic liquid layer comprises ionic liquid and a lithium ion ionization agent. Wherein the positive electrode material is Li 2 Ni 0.8 Co 0.1 Mn 0.1 O 2 The ionic liquid is [ EMIM]BF 4 The lithium ion ionization agent is LiBF 4 。
The preparation method of the electrode material comprises the following steps:
1) 0.25mol/L LiBF is added 4 And [ EMIM ]]BF 4 Mixing to obtain LiBF 4 -[EMIM]BF 4 Compounding ionic liquid, adding 20 times volume of absolute ethyl alcohol, and diluting LiBF 4 -[EMIM]BF 4 Compounding the ionic liquid to obtain the anode coating agent.
2) Mixing Li 2 Ni 0.8 Co 0.1 Mn 0.1 O 2 Placing in a tubular fluidized bed so that Li 2 Ni 0.8 Co 0.1 Mn 0.1 O 2 Continuously rolling and suspending on airflow, and spraying the anode coating agent obtained in the step 1) into a fluidized bed in a high-pressure spraying manner to ensure that Li 2 Ni 0.8 Co 0.1 Mn 0.1 O 2 The surface of the tube is coated with a layer of nano liquid drops, and in the process of spray coating, the tube wall is directly heated by a sleeve, the coating temperature is maintained at about 120 ℃, and finally the tube coated with LiBF is obtained 4 -[EMIM]BF 4 Composite ionic liquid nanolayerLi of (2) 2 Ni 0.8 Co 0.1 Mn 0.1 O 2 Electrode material (LEBF-NCM 811).
Comparative example 1 (different from example 1 in that no lithium ion ionization agent is contained)
An electrode material comprises a positive electrode material and an ionic liquid layer coated on the surface of the positive electrode material, wherein the ionic liquid layer comprises [ EMIM ]]BF 4 The positive electrode material is Li 2 Ni 0.8 Co 0.1 Mn 0.1 O 2 。
The preparation method of the electrode material comprises the following steps:
1) Adding 20 times volume of absolute ethanol, diluting [ EMIM ]]BF 4 And (4) ionic liquid to obtain the positive electrode coating agent.
2) Using LiNbO 3 For Li 2 Ni 0.8 Co 0.1 Mn 0.1 O 2 (NCM 811) coating: using a tubular fluidised bed for Li 2 Ni 0.8 Co 0.1 Mn 0.1 O 2 Continuously rolling and suspending on the air flow, and spraying LiNbO 3 Coating the raw material to finally obtain LiNbO 3 -Li 2 Ni 0.8 Co 0.1 Mn 0.1 O 2 The precursor (LNO-NCM 811 precursor) is placed in an oxygen sintering furnace to be sintered for 6h at 350 ℃ to obtain the LiNbO coated surface 3 Nanolayered Li 2 Ni 0.8 Co 0.1 Mn 0.1 O 2 (LNO-NCM811)。
3) Putting the LNO-NCM811 obtained in the step 2) into a tubular fluidized bed to enable the LNO-NCM811 to roll continuously and suspend on the air flow, spraying the anode coating agent obtained in the step 1) into the tubular fluidized bed in a high-pressure spraying mode to enable the surface of the LNO-NCM811 to be coated with a layer of nano liquid drops, meanwhile, directly heating a sleeve on the pipe wall in the spraying coating process to maintain the coating temperature at about 120 ℃, and finally obtaining the coating [ EMIM ]]BF 4 LiNbO of composite ionic liquid nano-layer 3 -Li 2 Ni 0.8 Co 0.1 Mn 0.1 O 2 Electrode material (EBF-LNO-NCM 811).
Comparative example 2 (different from example 1 in that no ionic liquid is contained)
An electrode material comprises a positive electrode material and a lithium ion ionization agent coated on the surface of the positive electrode material. Wherein the cathode material is Li 2 Ni 0.8 Co 0.1 Mn 0.1 O 2 The lithium ion ionization agent is LiBF 4 。
The preparation method of the electrode material comprises the following steps:
1) Using LiNbO 3 For Li 2 Ni 0.8 Co 0.1 Mn 0.1 O 2 (NCM 811) coating: using a tubular fluidised bed for Li 2 Ni 0.8 Co 0.1 Mn 0.1 O 2 Continuously rolling and suspending on the air flow, and spraying LiNbO 3 Coating the raw material to finally obtain LiNbO 3 -Li 2 Ni 0.8 Co 0.1 Mn 0.1 O 2 The precursor (LNO-NCM 811 precursor) is placed in an oxygen sintering furnace to be sintered for 6h at 350 ℃ to obtain the LiNbO coated surface 3 Nanolayered Li 2 Ni 0.8 Co 0.1 Mn 0.1 O 2 (LNO-NCM811)。
3) Putting the LNO-NCM811 obtained in the step 1) into a tubular fluidized bed, enabling the LNO-NCM811 to continuously roll and suspend on the air flow, and then putting a lithium ion ionization agent LiBF 4 Spraying into tubular fluidized bed in high pressure spray mode to coat a layer of nanometer liquid drop on LNO-NCM811 surface, directly heating with sleeve on tube wall during spray coating process to maintain coating temperature at about 120 deg.C, and finally obtaining LiBF coated product 4 Nanolayered LiNbO 3 -Li 2 Ni 0.8 Co 0.1 Mn 0.1 O 2 Electrode material (LBF-LNO-NCM 811).
Respectively according to the mass ratio of 82:15:3 weighing electrode material and Li 6 PS 5 A Cl solid electrolyte and VGCF conductive carbon were ground for 10min, wherein the electrode materials were those prepared in example 4 and comparative examples 1 to 2, respectively, to prepare a composite positive electrode in example 4 (experimental group 5) and composite positive electrodes in comparative examples 1 to 2 (comparative groups 5 to 6), respectively. Compounding each30mg of positive electrode and 120mg of sulfide solid electrolyte are respectively pressed into a battery component with the diameter of 10mm, 200umLi-In metal foil is used as a negative electrode to assemble a sulfide all-solid battery, and electrochemical performance test is carried out. The test conditions were: the current is 0.3C multiplying power, the voltage range is 2.4-3.7V (3.0-4.3 Vvs. Li +/Li), the battery test pressure is less than 5MPa at 25 ℃, the cycle is 100 weeks, and the test comparison results are shown in Table 4. The electrochemical performance test data of the experimental group 1 in table 1 is also used as a reference.
TABLE 4
As can be seen from table 4, the electrochemical performances of the experimental group 5 and the control groups 5 to 6 were significantly lower than that of the experimental group 1. In experiment group 5 (example 4), the surface of the NCM811 positive electrode was not coated with LiNbO 3 The protective layer increases the interface impedance of the positive electrode of the battery, and the specific reason is that the composite ionic liquid can play a role in increasing a lithium conducting channel in a part of pores between the positive electrode and the electrolyte, but if a coating layer is not formed on the surface of the NCM811 material in advance, a large-area direct contact layer can be formed, so that the direct side reaction between the positive electrode and the electrolyte is increased, and the cycle performance of the battery is damaged. In the control group 5 (comparative example 1), since no lithium ion ionization agent is added and lithium ions are lost, the composite ionic liquid layer is a non-ionic conductive agent and cannot conduct lithium ions, impurities are formed to hinder the transmission of lithium ions, and thus the performance is poor. The control 6 (comparative example 2) did not allow efficient lithium ion transport due to the absence of the ionic liquid, and the transport rate was slow, which similarly decreased the cycle performance of the full cell.
While the preferred embodiments of the present invention have been illustrated and described, it will be understood by those skilled in the art that the present invention is not limited to the details of the embodiments shown and described, but is capable of numerous equivalents and substitutions without departing from the spirit of the invention as set forth in the claims appended hereto.
Claims (7)
1. The electrode material is characterized by comprising an electrode material substrate and a composite ionic liquid layer coated on the surface of the electrode material substrate, wherein the composite ionic liquid layer comprises ionic liquid and a lithium ion ionization agent;
the ionic liquid comprises a cation and an anion, the cation comprising [ EMIM] + 、[PMPip] + 、[TMPA] + And [ TEA] + Wherein the anion comprises BF 4 - 、(CF 3 SO 2 ) 2 N - And PF 6 - One or more of;
the lithium ion ionization agent comprises LiBF 4 、Li(CF 3 SO 2 ) 2 N and LiPF 6 One or more of;
the surface of the electrode material substrate is further coated with a nano layer, the nano layer is positioned between the electrode material substrate and the composite ionic liquid layer, and the components of the nano layer comprise Li 2 Zr(PO 4 ) 2 、LiNbO 3 And Li 2 WO 4 One or more of;
the mass fraction of the electrode material in the composite positive electrode is 82%, and the composite positive electrode comprises the electrode material, a solid electrolyte and conductive carbon.
2. The method for preparing an electrode material according to claim 1, comprising the steps of:
and mixing the ionic liquid and the lithium ion ionization agent to obtain composite ionic liquid, and coating the electrode material substrate by adopting the composite ionic liquid to obtain the electrode material.
3. The preparation method according to claim 2, characterized in that before the coating treatment of the electrode material substrate by the composite ionic liquid, a pretreatment step is further included, and the pretreatment step includes: with Li 2 Zr(PO 4 ) 2 、LiNbO 3 And Li 2 WO 4 The electrode material substrate is subjected to coating treatment.
4. Use of the electrode material of claim 1 in a battery.
5. A battery comprising an electrolyte and the electrode material of claim 1.
6. The battery of claim 5, wherein the electrolyte is Li 3 PS 4 、Li 4 P 2 S 6 Or Li 7-a PS 6- a Y a Wherein: y is at least one of Cl, br and I, and a is more than or equal to 0.5 and less than or equal to 2.
7. The battery of claim 5, wherein the electrolyte has a particle size of 0.5-5um.
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