Solid-state electrolyte and lithium-ion battery using the same

Abstract

A solid electrolyte and an applicable lithium-ion battery. The solid electrolyte includes a multi-doped material with the chemical formula LixTiyMm(PO4)3, where 0.8 ≤ x ≤ 1.5, 0 < y ≤ 0.6, M represents at least three different doping elements, 1.2 ≤ m ≤ 1.7, and y / m ≤ 1 / 3. The negative electrode in the lithium-ion battery includes at least a lithium-containing material. The solid electrolyte is located between the positive and negative electrodes of the lithium-ion battery and contacts the lithium-containing material.

Description

Technical Field

[0001] The present invention relates to a solid electrolyte, and more particularly to an oxide-based solid electrolyte for use in a lithium ion battery and a lithium ion battery using the same. Prior Art

[0002] To date, rechargeable lithium ion batteries have evolved into important energy storage devices, which are widely used, such as in wearable electronic devices, consumer electronics products, electric vehicles, etc., and have advantages such as high energy density, long life, and low cost.

[0003] Replacing the liquid electrolyte in a traditional lithium ion battery with a solid electrolyte has the following advantages: high safety, no leakage pollution, no flammable and volatile electrolyte, prevention of short circuit, simple production, small size, convenient storage, etc., and thus has become an important research direction. Solid electrolytes can be initially classified into polymer-based, sulfide-based, and oxide-based. Among them, polymer-based ones such as polyethylene oxide (PEO) or polyacrylonitrile (PAN) have disadvantages such as low ionic conductivity, narrow electrochemical window, and low mechanical strength; sulfide-based ones such as thio-lithium superionic conductor (thio-LISICON), Li-argyrodite, or lithium germanium phosphorus sulfur (LGPS) are sensitive to moisture and easily produce toxic hydrogen sulfide; relatively speaking, oxide-based ones have better advantages in high ionic conductivity and chemical stability. Therefore, for applications in portable terminal products, lithium ion batteries using oxide-based solid electrolytes would be a relatively better choice.

[0004] Sodium superionic conductor (NASICON), which belongs to the oxidized solid electrolyte, has good ionic conductivity and is insensitive to moisture and carbon dioxide in the air. Therefore, the requirements for mass production are relatively low. Here, take the lithium aluminum titanium phosphate (Li1.3Al0.3Ti1.7(PO4)3, LATP) material as an example. As shown in Figure 1, during the discharge process, titanium ions (Ti4+) on the surface of the solid electrolyte (LATP) 13 will undergo a redox reaction with the lithium metal at the negative electrode 11 of the lithium-ion battery (Ti4+ à Ti3+). During the charge and discharge process of the lithium-ion battery, as titanium ions (IV) are gradually consumed, the solid electrolyte 13 gradually deteriorates from the surface, and the lithium dendrites formed after the reduction of lithium ions also penetrate into the structure (Figure 2), damaging the structure or even causing severe fragmentation, affecting the cycle life of the battery. This phenomenon urgently needs to be improved. Summary of the Invention

[0005] The present disclosure provides a solid electrolyte applicable to a lithium-ion battery. One negative electrode of the lithium-ion battery includes at least one lithium-containing material. The solid electrolyte includes a multi-doped material with the chemical formula LixTiyMm(PO4)3, where 0.8 ≤ x ≤ 1.5, 0 < y ≤ 0.6, M represents at least three different doping elements, 1.2 ≤ m ≤ 1.7, and y / m ≤ 0.5.

[0006] In one embodiment, the multi-doped material has a disordered sublattice.

[0007] In one embodiment, M represents at least four different doping elements.

[0008] In one embodiment, the multi-doped material is a high-entropy NASICON-type material.

[0009] In one embodiment, the doping elements are metal elements with ionic valences between +2 and +6, and are further limited to between +3 and +6.

[0010] In one embodiment, the ionic radius of the doping elements is no more than 100 pm, and is further limited to between 53 pm and 90 pm.

[0011] In one embodiment, the doping element system is magnesium, aluminum, calcium, scandium, vanadium, zinc, gallium, germanium, yttrium, zirconium, niobium, molybdenum, indium, tin, antimony, hafnium, tantalum or tungsten.

[0012] In one embodiment, the ionic conductivity of the solid electrolyte is higher than 10 -5Scm -1.

[0013] The present disclosure further provides a lithium ion battery, including a positive electrode, a negative electrode having a lithium-containing material, and the above-mentioned solid electrolyte, wherein the solid electrolyte is located between the positive electrode and the negative electrode and contacts the lithium-containing material.

[0014] In one embodiment, the negative electrode includes lithium metal or lithium titanate.

[0015] In one embodiment, the positive electrode includes lithium iron phosphate, lithium manganate, lithium nickel cobalt manganese oxide or lithium nickel cobalt aluminum oxide.

[0016] In order to have a better understanding of the above and other aspects of the present disclosure, the following specific embodiments are given and described in detail in conjunction with the accompanying drawings as follows: Brief description of the drawings

[0017] Figure 1 is a schematic diagram of the reduction of titanium ions in LATP by lithium metal during the battery discharge process. Figure 2 is a schematic diagram showing the deterioration after the solid electrolyte LATP contacts lithium metal. Figures 3A and 3B are cyclic voltammograms measured for Li 1.3Al 0.4Ti 0.5Zr 0.5Sn 0.5Ta 0.1(PO 4) 3 of the present disclosure and known LATP, respectively. Figures 4A to 4D are cyclic voltammograms of the multi-doped materials of the embodiments of the present disclosure. Figures 5A and 5B are schematic diagrams respectively illustrating the diffusion channels of lithium ions between the ordered and disordered sublattices. Figure 6 is an exploded view of the components of the lithium ion battery according to the embodiment of the present disclosure. Embodiments

[0018] The following selects some specific examples to illustrate the implementation manners of the present disclosure. Those skilled in the art can clearly understand the technical features and effects of the present disclosure from the content disclosed in this specification. However, it should be noted that the structures, proportions, sizes, etc. shown in the drawings attached to this specification are only used to cooperate with the content disclosed in the specification for those skilled in the art to understand and read, and are not used to limit the limiting conditions under which the present disclosure can be implemented.

[0019] The present disclosure provides a solid electrolyte applicable to a lithium-ion battery, which contains a multi-doped material. By doping elements to replace part of the titanium component in the solid electrolyte, the concentration of titanium ions (IV) is reduced, and the redox reaction between titanium ions (IV) and the lithium-containing material of the battery negative electrode is inhibited or prevented, thereby slowing down or eliminating the deterioration process of the solid electrolyte. And this multi-doped material still needs to maintain good ionic conductivity to ensure the charge and discharge efficiency of the lithium-ion battery.

[0020] According to the present disclosure, the chemical formula of the multi-doped material is Li xTi yM m(PO 4) 3, where 0.8 ≤ lithium content x ≤ 1.5, 0 < titanium content y ≤ 0.6, M represents at least three different doping elements in addition to the titanium component, 1.2 ≤ doping element content m ≤ 1.7, the content of the substituted doping element is at least twice the remaining titanium content (y / m ≤ 0.5), or can reach three times or four times or more, and the above contents are all expressed in moles. Under the conditions of maintaining good ionic conductivity and a similar lattice structure, the selection conditions for the doping elements are as follows: select metal elements with an ionic valence similar to that of titanium. In this way, the doped metal elements are more stable in the crystal structure. The ionic valence of titanium (IV) is +4. Therefore, the selected metal elements should have an ionic valence between +2 and +6, or more preferably between +3 and +6; select metal elements with an ionic radius similar to that of titanium. If the ionic radius difference is too large, precipitates of impurity phases are likely to appear during the preparation process. The ionic radius of titanium (IV) is 67 pm. Therefore, metal elements with an ionic radius not greater than 100 pm can be selected, or more preferably between 53 pm and 90 pm. Through the above selection, the position of titanium atoms in the lattice can be more effectively replaced, and the titanium content in the material can be reduced.

[0021] According to the above selection conditions, the selectable doping elements are, for example: magnesium (Mg, +2 ion radius 72 pm), aluminum (Al, +3 ion radius 53 pm), calcium (Ca, +2 ion radius 100 pm), scandium (Sc, +3 ion radius 74.5 pm), vanadium (V, +2 ion radius 64 pm, +4 ion radius 58 pm, +5 ion radius 54 pm), zinc (Zn, +2 ion radius 74 pm), gallium (Ga, +3 ion radius 62 pm), germanium (Ge, +2 ion radius 73 pm, +4 ion radius 53 pm), yttrium (Y, +3 ion radius 90 pm), zirconium (Zr, +4 ion radius 72 pm), niobium (Nb, +3 ion radius 72 pm, +4 ion radius 68 pm, +5 ion radius 64 pm), molybdenum (Mo, +3 ion radius 69 pm, +4 ion radius 65 pm, +5 ion radius 61 pm, +6 ion radius 59 pm), indium (In, +3 ion radius 80 pm), tin (Sn, +4 ion radius 69 pm), antimony (Sb, +3 ion radius 76 pm, +5 ion radius 60 pm), hafnium (Hf, +4 ion radius 71 pm), tantalum (Ta, +3 ion radius 72 pm, +4 ion radius 68 pm, +5 ion radius 64 pm), tungsten (W, +4 ion radius 66 pm, +5 ion radius 62 pm, +6 ion radius 60 pm), etc. When making a selection, metal elements with fewer valence changes can be considered to avoid generating multiphase products that require subsequent complex separation steps, thereby increasing the possibility that the product is a single thermodynamic product and enhancing the purity and yield of a specific single product.

[0022] At least three or more doping elements can be selected from them to prepare poly-doped materials such as Li xTi yM1 m1M2 m2M3 m3(PO 4) 3, Li xTi yM1 m1M2 m2M3 m3M4 m4(PO 4) 3, etc., with even more doping elements to reduce the titanium component. The values of m1, m2, m3, m4... will vary due to charge balance. For example, when doping with elements of high valence and low valence simultaneously, the proportion of the high valence in the material can be appropriately reduced. Finally, the total content m of the doping elements is between 1.2 and 1.7. The synthesis methods used can be known methods such as wet chemical methods (such as sol-gel method, co-precipitation method), melt-quenching method, solid-phase method, etc., but are not limited to this. Several examples are given below to illustrate the properties of the poly-doped materials disclosed in this disclosure.

[0023] In one embodiment, the doping elements selected are aluminum(III), zirconium(IV), tin(IV), and tantalum(V), a total of four. The synthesized multi-doped material is identified by X-ray diffraction (XRD). The comparison of the spectra shows that it has a NASICON crystal phase. Observation and analysis by scanning electron microscope (SEM) and energy-dispersive X-ray spectroscopy (EDS) show that the composition is Li 1.3Al 0.4Ti 0.5Zr 0.5Sn 0.5Ta 0.1(PO 4) 3. The molar ratio of titanium to the doping elements is 0.33 (y / m = 0.5 / 1.5 = 0.33), that is, the content of the doping elements is three times that of titanium. The measured ionic conductivity reaches 1.32×10 -4Scm -1. The redox behavior between it and lithium metal at a set voltage is measured by cyclic voltammetry (scanning rate 1mV / s). The obtained cyclic voltammogram is shown in Figure 3A. Compared with the LATP material in Figure 3B, the LATP material will have an obvious cathodic peak 31 at 2.2V. At this time, titanium(IV) ions are reduced to titanium(III) ions, and the anodic peak 32 is lower than the cathodic peak 31. Therefore, titanium(IV) ions will gradually be lost and the LATP material will deteriorate. On the contrary, the Li 1.3Al 0.4Ti 0.5Zr 0.5Sn 0.5Ta 0.1(PO 4) 3 disclosed in this disclosure does not show an obvious reduction reaction at 2.2V. It can be seen that it can effectively inhibit the reaction between titanium(IV) ions and lithium metal and improve the stability of the solid electrolyte to lithium metal. Therefore, it is applicable to lithium-ion batteries.

[0024] In other embodiments, various other multi-doped materials are prepared using aluminum(III), zirconium(IV), yttrium(III), niobium(III), tantalum(V), tungsten(VI), etc. Through composition analysis, materials such as LiAl 0.4Ti 0.4Y 0.4Zr 0.4W 0.4(PO 4) 3, LiAl 0.4Ti 0.4Zr 0.4Nb 0.4W 0.4(PO 4) 3, Li 1.4Al 0.4Ti 0.4Y 0.4Zr 0.4Ta 0.4(PO 4) 3, Li 1.4Al 0.4Ti 0.4Zr 0.4Nb 0.4Ta 0.4(PO 4) 3, etc. are obtained. The doping element content of these multi-doped materials reaches four times the titanium content (y / m = 0.5 / 1.5 = 0.25). Their XRD patterns show that they have the NASICON crystal phase, and the ionic conductivity is nearly 10 -5Scm -1. Their cyclic voltammograms are respectively shown in Figures 4A to 4D. No obvious reduction reaction is measured at 2.2V, which proves that the reaction between titanium(IV) ions and lithium metal can be effectively inhibited. In addition, the difference between the oxidation-reduction peak pairs of the LATP material is 1.04V (Figure 3B), while in the small amount of oxidation-reduction reactions of the multi-doped materials prepared here, the difference between the oxidation-reduction peak pairs is about between 1.35V and 2.4V. The increase in the difference indicates that the reduction reaction of titanium(IV) ions is delayed, and it also has an inhibitory effect. All show an improvement in the stability of the solid electrolyte against lithium metal, and thus are applicable to lithium-ion batteries.

[0025] This disclosure is not limited to NASICON-type materials. For example, for the multi-doped materials obtained by doping with the above-mentioned appropriate ions, even if they do not show the NASICON crystal phase, but when they have better stability against lithium metal and have suitable ionic conductivity, they are still applicable to lithium-ion batteries.

[0026] The above multi-doped materials can be well adhered to the lithium metal anode, without the need to additionally add a protective layer between the solid electrolyte and the lithium metal, and are also insensitive to moisture and carbon dioxide in the air. Therefore, they have more advantages in terms of production process and cost. Please note that the multi-doped materials according to the concept of this disclosure are not limited to the specific materials listed above.

[0027] According to the concept of the present disclosure, by using the high-entropy doping method, a variety of specific elements are doped into the material to form disorder and tend to form the thermodynamically most stable product, making the product single and stable, and less likely to have intermediate phases, and a relatively pure-phase crystal product can be prepared. Please refer to FIGS. 5A and 5B, which are schematic diagrams showing the transmission channels of lithium ions between ordered and disordered sublattices respectively. In FIG. 5A, in the solid electrolyte 53 between the negative electrode 51 and the positive electrode 52, the oxygen anion sublattice 531 and the titanium cation sublattice 532 are arranged in an ordered manner, and a lithium ion diffusion channel 55 is formed therebetween; in FIG. 5B, because the titanium cation sublattice 532 in the solid electrolyte 53 and the other doped metal cation sublattices 533 have different sizes, the oxygen anion sublattice 531 and the titanium cation sublattice 532 / metal cation sublattices 533 are arranged in a disordered manner, expanding a part of the lithium ion diffusion channel 55, enabling the lithium ions 511 to be transmitted more rapidly, thereby increasing the ionic conductivity.

[0028] The present disclosure also provides a all-solid-state lithium ion battery 60. Please refer to FIG. 6, which is an exploded view of the components of the lithium ion battery according to an embodiment of the present disclosure. The main structure includes a negative electrode 51, a positive electrode 52, and a solid electrolyte 53. The negative electrode 51 includes at least a lithium-containing material. The solid electrolyte 53 is located between the positive electrode 52 and the negative electrode 51 and is in contact with the lithium-containing material. The solid electrolyte 53 pressed into a pellet shape includes a multi-doped material with the chemical formula Li xTi yM m(PO 4) 3, where 0.8 ≤ x ≤ 1.5, 0 < y ≤ 0.6, M represents at least three different doping elements, 1.2 ≤ m ≤ 1.7, and y / m ≤ 0.5. The details are as described above. Any of the aforementioned multi-doped materials can be used and will not be elaborated here. In one embodiment, the negative electrode 51 can use lithium metal or lithium titanate (Li 4Ti 5O 12), and the positive electrode 52 can use lithium iron phosphate (LiFePO 4, LFP), lithium manganate (LiMn 2O 4), lithium nickel cobalt manganese oxide (NCM), or lithium nickel cobalt aluminum oxide (NCA), etc., but not limited thereto.

[0029] The lithium-ion battery 60 of the present disclosure can be applied to different shapes. FIG. 6 shows an example where the combination of the negative electrode 51, the solid electrolyte 53, and the positive electrode 52 is placed in the accommodation space between the top cover 661 and the bottom cover 662, and shrapnel 67 and gaskets 68 are added to fix their relative positions. The obtained lithium-ion battery uses a solid electrolyte that is stable to lithium-containing materials and insensitive to moisture / carbon dioxide, and does not require an additional protective layer, which can improve durability, simplify the process, and reduce production costs. Its good ionic conductivity can also enable the lithium-ion battery to have sufficient charge and discharge efficiency.

[0030] In summary, although the present invention has been disclosed as above with embodiments, it is not intended to limit the present invention. Those of ordinary skill in the technical field to which the present invention pertains can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be subject to that defined by the appended claims for patent.

[0031] 11: Negative electrode (lithium metal) 13: Solid electrolyte (LATP) 31: Reduction peak 32: Oxidation peak 51: Negative electrode 52: Positive electrode 53: Solid electrolyte 55: Diffusion channel 60: Lithium-ion battery 67: Shrapnel 68: Gasket 511: Lithium ion 531: Oxygen anion sublattice 532: Titanium cation sublattice 533: Metal cation sublattice 661: Top cover 662: Bottom cover

Claims

1. A solid electrolyte for use in a lithium-ion battery, wherein a negative electrode of the lithium-ion battery comprises at least a lithium-containing material, characterized in that the solid electrolyte comprises a multi-element doped material with the chemical formula LixTiyMm(PO4)3, wherein 0.8≤x≤1.5, 0<y≤0.6, M represents at least three different doping elements, 1.2≤m≤1.7, and y / m ≤1 / 3.

2. The solid electrolyte as claimed in claim 1, wherein the multi-doped material has a disordered sublattice.

3. The solid electrolyte as described in claim 1, wherein M represents at least four different doping elements.

4. The solid electrolyte as described in claim 3, wherein the multi-component doped material is a high-entropy NASICON type material.

5. The solid electrolyte as claimed in claim 1, wherein each of the doping elements is a metallic element with an ionic valence between +2 and +6.

6. The solid electrolyte as described in claim 5, wherein the ionic valence of the metal element is between +3 and +6.

7. The solid electrolyte as described in claim 1, wherein the ionic radius of each dopant element is not greater than 100 pm.

8. The solid electrolyte as described in claim 7, wherein the ionic radius is between 53 pm and 90 pm.

9. The solid electrolyte as claimed in claim 1, wherein each of the doping elements is selected from magnesium, aluminum, calcium, scandium, vanadium, zinc, gallium, germanium, yttrium, zirconium, niobium, molybdenum, indium, tin, antimony, hafnium, tantalum and tungsten.

10. The solid electrolyte as claimed in claim 1, wherein the ionic conductivity of the solid electrolyte is higher than 10⁻⁵ Scm⁻¹.

11. A lithium-ion battery, characterized in that it comprises: One positive pole; A negative electrode, comprising at least one lithium-containing material; And a solid electrolyte as described in any one of claims 1-10, the solid electrolyte being located between the positive electrode and the negative electrode and in contact with the lithium-containing material.

12. The lithium-ion battery as claimed in claim 11, wherein the negative electrode comprises lithium metal or lithium titanate.

13. The lithium-ion battery as claimed in claim 11, wherein the positive electrode comprises lithium iron phosphate, lithium manganese oxide, lithium nickel cobalt manganese oxide, or lithium nickel cobalt aluminum oxide.

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