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 Li2CoO2、Li2Ni0.33Co0.33Mn0.33O2、Li2Ni0.6Co0.2Mn0.2O2、Li2Ni0.8Co0.1Mn0.1O2In 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 density2Ni0.6Co0.2Mn0.2O2Or Li2Ni0.8Co0.1Mn0.1O2As a positive electrode material. The negative electrode material includes at least one of lithium powder, graphite, and lithium titanate, and more preferably, in view of energy density of the batteryAnd the negative electrode material adopts lithium powder or graphite with 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 BF4 -、(CF3SO2)2N-And PF6 -One or more of (a).
Preferably, the ionic liquid coated on the surface of the cathode material adopts [ EMIM ] as the cation of the ionic liquid]+、[PMPip]+At least one of (1) and (b) as an anion, BF is used4 -、PF6 -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 BF4 -。
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)3SO2)2N-. 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)3SO2)2N-。
Preferably, the lithium ion ionization agent comprises LiBF4、Li(CF3SO2)2N and LiPF6One 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 Li2Zr(PO4)2、LiNbO3And Li2WO4One or more of (a). The nano-layer adopts LiNbO as a component in consideration of the ionic conductivity and electrochemical impedance of the nano-layer3The thickness of the nanolayer is preferably 5-20 nm.
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 0.1-1mol/L, and more preferably, the concentration of the lithium ion ionization agent is 0.2-0.5mol/L in view of the viscosity and 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 Li2Zr(PO4)2、LiNbO3And Li2WO4The 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 the coating is preferably performed using a spray drying method in consideration of the cost of coating and the 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 Li3PS4、Li4P2S6Or Li7-aPS6-aYaWherein: 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 improves the compactness (the compactness reaches more than 90 percent) of the electrode material by coating the composite ionic liquid layer on the surface of the electrode material matrix, wherein the components of the composite ionic liquid layer comprise ionic liquid and lithium ion ionization agent, and after the electrode material and sulfide solid electrolyte and other materials are combined into a solid battery, the ionic liquid can be filled in the nanometer gap in the solid battery to make up the gap between the sulfide solid electrolyte and the electrode material, reduce the crystal boundary between the electrolytes, improve the effective contact area (the effective contact area reaches more than 95%) between the electrode material and the electrolyte, wherein the lithium ion ionization agent can be absorbed into the gap inside the battery by means of the ionic liquid to increase the conduction contact surface of the lithium ions, thereby reducing the interface impedance between the materials inside the battery (the interface impedance reaches 10 omega/cm).2Below), 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 Li2Ni0.8Co0.1Mn0.1O2The ionic liquid is [ EMIM]BF4The lithium ion ionization agent is LiBF4。
The preparation method of the electrode material comprises the following steps:
1) 0.25mol/L LiBF is added4And [ EMIM ]]BF4Mixing to obtain LiBF4-[EMIM]BF4Compounding ionic liquid, adding 20 times volume of absolute ethyl alcohol, and diluting LiBF4-[EMIM]BF4Compounding the ionic liquid to obtain the anode coating agent.
2) Using LiNbO3For Li2Ni0.8Co0.1Mn0.1O2(NCM811) coating: using a tubular fluidised bed for Li2Ni0.8Co0.1Mn0.1O2Continuously rolling and suspending on the air flow, and spraying LiNbO3Coating the raw material to finally obtain LiNbO3-Li2Ni0.8Co0.1Mn0.1O2The precursor (LNO-NCM811 precursor) is placed in an oxygen sintering furnace and sintered for 6h at 350 ℃ to obtain the LiNbO coated surface3Nanolayered Li2Ni0.8Co0.1Mn0.1O2(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 coating4-[EMIM]BF4LiNbO of composite ionic liquid nano-layer3-Li2Ni0.8Co0.1Mn0.1O2Electrode 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 Li6PS5And 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 Li6PS5And 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 coating4-[EMIM]BF4LiNbO of composite ionic liquid nano-layer3-Li2Ni0.8Co0.1Mn0.1O2At conventional mixing ratios (experimental group 2) compared to uncoated LiNbO3-Li2Ni0.8Co0.1Mn0.1O2(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 coated4-[EMIM]BF4LiNbO of composite ionic liquid nano-layer3-Li2Ni0.8Co0.1Mn0.1O2The 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 LiNbO3-Li2Ni0.8Co0.1Mn0.1O2(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 positive electrode material coated with the composite ionic liquid nano layer has the advantages that the interface impedance of the positive electrode is obviously reduced, meanwhile, the proportion of the electrode material is further improved, the energy of the electrode material can be well released, the energy density of the positive electrode is further improved, 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 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 ]](CF3SO2)2N, Li (CF) as lithium ion ionization agent3SO2)2N。
The preparation method of the electrode material comprises the following steps:
1) 0.3mol/L of Li (CF)3SO2)2N and [ TMPA ]](CF3SO2)2N are mixed to obtain Li (CF)3SO2)2N-[TMPA](CF3SO2)2N compounding with ionic liquid, adding anhydrous DMF (N, N-dimethylformamide) with 20 times volume, and diluting Li (CF)3SO2)2N-[TMPA](CF3SO2)2And 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) material3SO2)2N-[TMPA](CF3SO2)2And (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 Li6PS5And 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 Li6PS5And 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 used3SO2)2N-[TMPA](CF3SO2)2The 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 was stated that Li (CF) was coated3SO2)2N-[TMPA](CF3SO2)2The 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 improvement of the cycle stability and the service life of the battery are facilitated.
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 positive electrode material is Li2CoO2The cathode material is graphite powder, and the ionic liquid is [ EMIM ]]PF6And [ TMPA ]](CF3SO2)2N, Li (CF) as lithium ion ionization agent3SO2)2N。
The preparation method of the electrode material comprises the following steps:
1) 0.2mol/L of Li (CF)3SO2)2N and [ EMIM]PF6Mixing to obtain Li (CF)3SO2)2N-[EMIM]PF6Compounding ionic liquid, adding 20 times volume of anhydrous ethanol, and diluting Li (CF)3SO2)2N-[EMIM]PF6Composite ionAnd (5) sub-liquid to obtain the positive electrode coating agent.
2) 0.2mol/L of Li (CF)3SO2)2N and [ TMPA ]](CF3SO2)2N are mixed to obtain Li (CF)3SO2)2N-[TMPA](CF3SO2)2N compounding with ionic liquid, adding 20 times volume of anhydrous ethanol, and diluting Li (CF)3SO2)2N-[TMPA](CF3SO2)2And compounding the N with the ionic liquid to obtain the cathode coating agent.
3) By means of a tubular fluidized bed with Li2Zr(PO4)2For Li2CoO2Coating is carried out to obtain Li2Zr(PO4)2-Li2CoO2。
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 Li2Zr(PO4)2-Li2CoO2And respectively coating a layer of nano liquid drops on the surface of the graphite powder, and simultaneously directly heating the pipe wall by using a sleeve in the spray coating process to maintain the coating temperature at about 120 ℃ to finally obtain the coating material coated with Li (CF)3SO2)2N-[EMIM]PF6Li of composite ionic liquid nano-layer2Zr(PO4)2-Li2CoO2Electrode material (LEP-LZP-LCO) and Li (CF) cladding3SO2)2N-[TMPA](CF3SO2)2N 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 example2CoO2(control group 4), Li6PS5And 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 embodiment6PS5And mixing the Cl solid electrolyte and VGCF conductive carbon for 10min to obtain the corresponding composite cathode. 30mg of composite positive electrode is respectively pressed with 120mg of sulfide solid electrolyte to form a straight electrodeAnd assembling a battery assembly with the diameter of 10mm into a sulfide all-solid-state battery by taking a 15mg composite negative electrode as a negative electrode, and carrying out electrochemical performance test. 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 Li2CoO2And 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, meanwhile, the long circulation of the battery can be ensured, 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 circulation stability and the service life of the battery are facilitated to be 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 Li2Ni0.8Co0.1Mn0.1O2The ionic liquid is [ EMIM]BF4The lithium ion ionization agent is LiBF4。
The preparation method of the electrode material comprises the following steps:
1) 0.25mol/L LiBF is added4And [ EMIM ]]BF4Mixing to obtain LiBF4-[EMIM]BF4Compounding ionic liquid, adding 20 times volume of absolute ethyl alcohol, and diluting LiBF4-[EMIM]BF4Compounding the ionic liquid to obtain the anode coating agent.
2) Mixing Li2Ni0.8Co0.1Mn0.1O2Placing in a tubular fluidized bed so that Li2Ni0.8Co0.1Mn0.1O2Continuously rolling and suspending on the airflow, and spraying the anode coating agent obtained in the step 1) into a fluidized bed in a high-pressure spraying manner, so that Li2Ni0.8Co0.1Mn0.1O2The 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 obtained4-[EMIM]BF4Li of composite ionic liquid nano-layer2Ni0.8Co0.1Mn0.1O2Electrode 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 ]]BF4The positive electrode material is Li2Ni0.8Co0.1Mn0.1O2。
The preparation method of the electrode material comprises the following steps:
1) adding 20 times volume of absolute ethanol, diluting [ EMIM ]]BF4And (5) obtaining the positive electrode coating agent by using the ionic liquid.
2) Using LiNbO3For Li2Ni0.8Co0.1Mn0.1O2(NCM811) coating: using a tubular fluidised bed for Li2Ni0.8Co0.1Mn0.1O2Continuously tumbling and suspending in the air flowSpraying LiNbO3Coating the raw material to finally obtain LiNbO3-Li2Ni0.8Co0.1Mn0.1O2The precursor (LNO-NCM811 precursor) is placed in an oxygen sintering furnace and sintered for 6h at 350 ℃ to obtain the LiNbO coated surface3Nanolayered Li2Ni0.8Co0.1Mn0.1O2(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 ]]BF4LiNbO of composite ionic liquid nano-layer3-Li2Ni0.8Co0.1Mn0.1O2Electrode 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 positive electrode material is Li2Ni0.8Co0.1Mn0.1O2The lithium ion ionization agent is LiBF4。
The preparation method of the electrode material comprises the following steps:
1) using LiNbO3For Li2Ni0.8Co0.1Mn0.1O2(NCM811) coating: using a tubular fluidised bed for Li2Ni0.8Co0.1Mn0.1O2Continuously rolling and suspending on the air flow, and spraying LiNbO3Coating the raw material to finally obtain LiNbO3-Li2Ni0.8Co0.1Mn0.1O2The precursor (LNO-NCM811 precursor) is placed in an oxygen sintering furnace and sintered for 6h at 350 ℃ to obtain the LiNbO coated surface3Nanolayered Li2Ni0.8Co0.1Mn0.1O2(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 LiBF4Spraying 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 product4Nanolayered LiNbO3-Li2Ni0.8Co0.1Mn0.1O2Electrode material (LBF-LNO-NCM 811).
Respectively according to the mass ratio of 82: 15: 3 weighing electrode material and Li6PS5A Cl solid electrolyte and VGCF conductive carbon were ground for 10min, wherein the electrode materials were the electrode materials prepared in example 4 and comparative examples 1 to 2, respectively, to prepare a composite positive electrode of example 4 (experimental group 5) and a composite positive electrode of comparative examples 1 to 2 (comparative groups 5 to 6), respectively. 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 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 LiNbO3The protective layer can increase the interface impedance of the positive electrode of the battery, particularly because the composite ionic liquid can be arranged on the positive electrodePart of the pores between the NCM811 material and the electrolyte play a role in increasing the lithium conducting channel, but if a coating layer is not formed on the surface in advance, a large-area direct contact layer is formed on the NCM811 material, so that the direct side reaction of 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.