Disclosure of Invention
The purpose of the invention is as follows: aiming at the problems in the prior art, the invention provides a solid electrolyte modified lithium titanate negative electrode material and a preparation method thereof, wherein the tap density of the lithium titanate negative electrode material reaches 1.3 g/cm3Above, the pH value is 8-10, the discharge capacity of 5C reaches 135mAh g-1Above, 95% of the capacity at 0.1C; the raw materials in the production and preparation process are wide in source, the waste utilization can be realized, the preparation method is simple, the cost is low, the engineering amplification can be realized, and the continuous production can be realized.
The technical scheme is as follows: the invention provides a solid electrolyte modified lithium titanate negative electrode material, which has the following microscopic morphology: the secondary particles are spherical, the particle size is 5-20 μm, and the secondary particles are composed of primary particles with the grain size of 20-200 nm; the lithium ion solid electrolyte composed of fluorine-containing oxide and fluoride is attached to the surface of lithium titanate particles in the lithium titanate negative electrode material, and the mass fraction of the lithium ion solid electrolyte is 0.1-3%
The invention also provides a preparation method of the solid electrolyte modified lithium titanate negative electrode material, which comprises the following steps: s1: mixing titanium dioxide powder, lithium salt and deionized water, and performing primary sanding on the mixture to prepare a suspension A; s2: preparing the suspension A into a precursor B; s3: carrying out primary calcination on the precursor B to prepare primary calcined powder C; s4: uniformly mixing and stirring the primary calcined powder C and deionized water, and dropwise adding fluorine-containing lithium battery electrolyte into the mixture, wherein the temperature is not more than 25 ℃ in the dropwise adding process; then, carrying out secondary sanding to prepare a suspension D; s5: preparing the suspension D into a precursor E; s6: and carrying out secondary calcination on the precursor E to prepare secondary calcined powder F, wherein the secondary calcined powder F is the solid electrolyte modified lithium titanate negative electrode material.
Preferably, the fluorine-containing lithium battery electrolyte is expired or waste lithium battery electrolyte, electrolyte in a recycled lithium battery, defective lithium battery electrolyte or invalid lithium battery electrolyte with high water content.
Preferably, the solid content in the suspension A is 5% -25%; and/or the solid content of the suspension D is 5-25%.
Preferably, in S2, the suspension a is prepared into the precursor B by a spray granulation method; and/or preparing the suspension D into the precursor E by adopting a spray granulation method in the S5.
Preferably, in the S3, the environment of the primary calcination is: calcining in flowing air at 500-800 deg.c for 8-15 hr; and/or, in the S6, the environment of the secondary calcination is: calcining in flowing air at 500-800 deg.c for 8-15 hr.
Preferably, in S4, the lithium content in the dropwise added lithium battery electrolyte containing fluorine is 0.1-3% of the lithium content in the lithium salt, calculated according to the lithium content.
Preferably, the lithium salt is lithium carbonate, lithium hydroxide or lithium oxalate.
Preferably, the micro-morphology of the lithium titanate negative electrode material is as follows: the secondary particles are spherical and have a particle diameter of 5 to 20 μm, and the secondary particles are composed of primary particles having a crystal grain size of 20 to 200 nm.
Preferably, the titanium dioxide powder is anatase type industrial grade titanium dioxide.
Has the advantages that: the solid electrolyte modified lithium titanate negative electrode material and the preparation method thereof have the following advantages:
(1) the tap density of the solid electrolyte modified lithium titanate negative electrode material reaches 1.3 g/cm3The method has the advantages of good rate capability; the pH value of slurry prepared by using the solid electrolyte modified lithium titanate negative electrode material powder is 8-10, and the slurry is low in alkalinity; the 5C discharge capacity reaches 135mAh g-1The above content was 95% of the capacity at 0.1C.
(2) In the method for preparing the solid electrolyte modified lithium titanate cathode material, the fluorine-containing lithium battery electrolyte is dropwise added into the mixed solution of the primary calcined powder C and the deionized water, so that the fluorine-containing lithium battery electrolyte is hydrolyzed to generate fluoride products (such as LiF and PF)5、HPO2F2,H2PO3F、LiBF(OH)3、LiBF2(OH)2HF and the like), the surface alkalinity of the primary calcined powder C can be reduced in the hydrolysis process, heat can be generated in the hydrolysis process, and in order to ensure the normal operation of the reaction and ensure the uniformity of the finally formed suspension D, the mixed solution needs to be cooled and protected, so that the temperature of the mixed solution is not higher than 25 ℃; after forming a suspension D, preparing the suspension D into a precursor E by adopting a spray granulation method, then carrying out secondary calcination on the precursor E to prepare a secondary calcined powder F, and modifying the surface of fluorine-containing oxide and fluoride formed by calcining the hydrolysate of the electrolyte on the secondary calcined powder F, namely modifying the surface of the secondary calcined powder F modified with the fluorine-containing oxide and the fluoride to obtain the solid electrolyte modified lithium titanate negative electrode material; due to the fact that the surface of the material is modified by the fluorine-containing oxide and the fluoride, the solid electrolyte modified lithium titanate negative electrode material has the excellent performance of the point (1).
(3) The method adopts the technology of twice sanding and twice calcining to ensure that the lithium titanate generates a spinel pure phase, and ensures that the grain size and the secondary particle size of the lithium titanate are more controllable, thereby ensuring excellent electrochemical performance and excellent processing performance.
(4) The invention adopts the fluorine-containing lithium battery electrolyte, which can timely supplement lithium for lithium loss during calcination, and the hydrolysis product of the fluorine-containing lithium battery electrolyte can neutralize the surface alkalinity of the precursor so as to reduce the surface alkalinity of the product, and the pH value of the powder is 8-10; meanwhile, fluoride and phosphide generated by hydrolysis can form a solid electrolyte after calcination, and the solid electrolyte is similar to an artificial SEI film structure, so that the cycle and rate performance of the lithium titanate material are further improved.
(5) The fluorine-containing lithium battery electrolyte adopted by the invention is overdue or waste lithium battery electrolyte, electrolyte in recycled lithium batteries, defective lithium battery electrolyte or invalid lithium battery electrolyte with higher water content, and has wide raw material sources and low cost.
(6) The solid electrolyte is obtained by calcining a hydrolysate of fluorine-containing lithium battery electrolyte, is uniformly coated on the surface of lithium titanate particles, contains fluorine-containing oxide and fluoride, has high lithium ion conductivity, and improves the rate capability of the material.
(7) The lithium titanate material prepared by the invention has the advantages of high crystalline phase purity, small surface alkalinity, optimized sizes of crystal grains and powder, good processability, and good multiplying power and cycle performance.
(8) The lithium titanate material has the advantages of wide raw material source in the preparation process, simple preparation method, low cost, capability of realizing waste utilization, engineered amplification and capability of realizing continuous industrial production.
Detailed Description
The technical scheme of the invention is further explained by combining the specific embodiment as follows:
embodiment 1:
the embodiment provides a solid electrolyte modified lithium titanate negative electrode material, which has the following microscopic morphology: the secondary particles are spherical, the particle size is 5-20 μm, and the secondary particles are composed of primary particles with the grain size of 20-200 nm; the lithium ion solid electrolyte composed of fluorine-containing oxide and fluoride is attached to the surface of lithium titanate particles in the lithium titanate negative electrode material, and the mass fraction of the lithium ion solid electrolyte is 1%.
The preparation method of the solid electrolyte modified lithium titanate negative electrode material comprises the following steps (the process flow is shown in figure 1):
mixing industrial anatase titanium dioxide with lithium carbonate and deionized water, grinding and fully mixing in a sand mill to prepare suspension A with the solid content of 10%. And preparing the suspension A into a precursor B by adopting a spray granulation method. Calcining the precursor B in flowing air at 800 ℃ for 12 hours to prepare primary calcined powder C, mixing and stirring the primary calcined powder C and deionized water uniformly, and dropwise adding and recovering LiPF in the lithium battery under the protection of cooling6And (3) electrolyte, wherein the temperature of the mixed solution is not higher than 25 ℃ in the dropwise adding process, and the content of lithium in the electrolyte is 1% of that in the lithium carbonate. And (5) performing secondary sanding to prepare suspension D with the solid content of 10%. And preparing the suspension D into a precursor E by adopting a spray granulation method, calcining the precursor E in flowing air at 800 ℃ for 12 hours to prepare secondary calcined powder F, and obtaining the final product, namely the solid electrolyte modified lithium titanate negative electrode material. The tap density of the lithium titanate negative electrode material reaches 1.45 g/cm3The pH value is 8.5, the button half cell taking the metallic lithium as the counter electrode is manufactured, and the 1C discharge capacity reaches 156 mAh g-1And 5C discharge capacity reaches 138 mAh g-1As shown in fig. 2; the capacity retention rate was 87.5% at 5C for 500 cycles, as shown in fig. 3.
Embodiment 2:
the embodiment provides a solid electrolyte modified lithium titanate negative electrode material, which has the following microscopic morphology: the secondary particles are spherical, the particle size is 5-20 μm, and the secondary particles are composed of primary particles with the grain size of 20-200 nm; the lithium ion solid electrolyte composed of fluorine-containing oxide and fluoride is attached to the surface of lithium titanate particles in the lithium titanate negative electrode material, and the mass fraction of the lithium ion solid electrolyte is 2%.
The preparation method of the solid electrolyte modified lithium titanate negative electrode material comprises the following steps (the process flow is shown in figure 1):
mixing industrial anatase titanium dioxide with lithium hydroxide and deionized water, grinding in a sand mill, and fully mixing to prepare suspension A with the solid content of 12%. And preparing the suspension A into a precursor B by adopting a spray granulation method. Calcining the precursor B in flowing air at 800 ℃ for 10 hours to prepare primary calcined powder C, mixing and stirring the primary calcined powder C and deionized water uniformly, and dropwise adding LiBF of a lithium battery electrolyte manufacturer under the protection of cooling4And (3) adding the defective electrolyte, wherein the temperature of the mixed solution is not higher than 25 ℃ in the dropwise adding process, and the lithium content in the electrolyte is 2% of the lithium content in the lithium carbonate. And D, performing secondary sanding to prepare a suspension with the solid content of 12%. And preparing the suspension D into a precursor E by adopting a spray granulation method, calcining the precursor E in flowing air at 800 ℃ for 10 hours to prepare secondary calcined powder F, and obtaining the final product, namely the solid electrolyte modified lithium titanate negative electrode material. The tap density of the lithium titanate negative electrode material reaches 1.35 g/cm3pH value is 9.5, the button half cell taking metallic lithium as a counter electrode is manufactured, and 1C discharge capacity reaches 152 mAh g-1And 5C discharge capacity reaches 135mAh g-1And the capacity retention rate of 500 cycles at 5 ℃ is 94.2%.
Embodiment 3:
the embodiment provides a solid electrolyte modified lithium titanate negative electrode material, which has the following microscopic morphology: the secondary particles are spherical, the particle size is 5-20 μm, and the secondary particles are composed of primary particles with the grain size of 20-200 nm; the lithium ion solid electrolyte composed of fluorine-containing oxide and fluoride is attached to the surface of lithium titanate particles in the lithium titanate negative electrode material, and the mass fraction of the lithium ion solid electrolyte is 1.5%.
The preparation method of the solid electrolyte modified lithium titanate negative electrode material comprises the following steps (the process flow is shown in figure 1):
mixing industrial anatase titanium dioxide with oxalic acidLithium and deionized water were mixed, milled in a sand mill and mixed thoroughly to prepare suspension a with 8% solids. And preparing the suspension A into a precursor B by adopting a spray granulation method. Calcining the precursor B in flowing air at 750 ℃ for 14 hours to prepare primary calcined powder C, mixing and stirring the primary calcined powder C and deionized water uniformly, and dropwise adding LiPF of a lithium battery electrolyte manufacturer under cooling protection6And (3) adding the defective electrolyte, wherein the temperature of the mixed solution is not higher than 25 ℃ in the dropwise adding process, and the lithium content in the electrolyte is 1.5% of the lithium content in the lithium carbonate. And (5) performing secondary sanding to prepare suspension D with the solid content of 8%. And preparing the suspension D into a precursor E by adopting a spray granulation method, calcining the precursor E in flowing air at 750 ℃ for 14 hours to prepare secondary calcined powder F, and obtaining the final product, namely the solid electrolyte modified lithium titanate negative electrode material. The tap density of the lithium titanate negative electrode material reaches 1.3 g/cm3The pH value is 8, the button half cell taking the metallic lithium as the counter electrode is manufactured, and the 1C discharge capacity reaches 158 mAh g-1And 5C discharge capacity of 137mAh g-1The capacity retention rate of 500 cycles at 5C is 85.2 percent, and the capacity retention rate of 500 cycles at 5C is 500 percent.
The above embodiments are merely illustrative of the technical concepts and features of the present invention, and the purpose of the embodiments is to enable those skilled in the art to understand the contents of the present invention and implement the present invention, and not to limit the protection scope of the present invention. All equivalent changes and modifications made according to the spirit of the present invention should be covered within the protection scope of the present invention.