Secondary battery composite electrolyte, secondary battery, and battery pack
The present invention is provided to reduce the influence of expansion and contraction of an active material, form a favorable interface between a solid electrolyte and an active material, and improve the high temperature durability and cycle lifespan of a battery. A secondary battery composite electrolyte includes an inorganic compound having an Li ion conductivity at 25° C. that is less than 1×10 −10 S/cm and an organic electrolyte. The weight ratio between the organic electrolyte and the inorganic compound is 0.1% or more and 20% or less.
1. A secondary battery comprising:
a positive electrode;
a negative electrode comprising negative electrode active material particles that insert and extract Li ions; and
an electrolyte layer arranged between the positive electrode and the negative electrode,
wherein the electrolyte layer is formed of a secondary battery composite electrolyte that comprises inorganic solid particles comprising an inorganic compound having an Li ion conductivity at 25° C. that is less than 10 −10 S/cm and an organic electrolyte,
wherein the secondary battery composite electrolyte is a gel-like polymer electrolyte,
wherein the electrolyte layer, and the positive electrode and the negative electrode are formed such that a surface of the electrolyte layer is in close contact with the surfaces of the positive electrode and the negative electrode along unevennesses,
wherein the surface of the negative electrode facing the positive electrode includes recesses that contain the inorganic solid particles, and
wherein the secondary battery composite electrolyte, an amount of the organic electrolyte is from 0.1 to 20 parts by mass, based on 100 parts by mass of the inorganic compound,
wherein, when an Li ion concentration at a contact interface between the inorganic compound and the organic electrolyte is C Li(surface) , and an Li ion concentration in the organic electrolyte is C Li(organic) , C Li(surface) >C Li(organic) is satisfied, and
wherein, in a complex modulus spectrum in which an imaginary part of a complex modulus represented by the following Equation (1) is plotted against a common logarithm of a measurement frequency, when the peak frequency is ω max , the relationship between ω max-hybrid of the secondary battery composite electrolyte and ω max-organic of the organic electrolyte included in the secondary battery composite electrolyte satisfies ω max-hybrid >ω max-organic :
{circumflex over ( M )}(ω)= iωε 0 {circumflex over (Z)} (ω)/ k (1),
wherein i is a complex number, ω is an angular frequency, ε 0 is a vacuum dielectric constant, Z(ω) is a complex impedance, and k is a cell constant obtained by dividing a thickness of the electrolyte layer by an area.
2. The secondary battery according to claim 1 , wherein a thinnest part of the electrolyte layer is less than 8 μm in thickness.
3. The secondary battery according to claim 1 , wherein the negative electrode comprises a negative electrode active material comprising Ti.
4. The secondary battery according to claim 1 , wherein the secondary battery has a bipolar electrode structure in which, when a structure in which a positive electrode and a negative electrode are alternately laminated with the electrolyte layer interposed therebetween is set as one set, two or more sets are included.
5. A battery pack comprising the secondary battery according to claim 1 .
6. A vehicle comprising the battery pack according to claim 5 .
7. The secondary battery according to claim 1 , wherein the secondary battery composite electrolyte has a half width of a single highest intensity peak 2θ of from 0.05 deg to less than 1.00 deg, measured according to an X-ray diffraction method using a Cu—Kα radiation source.
8. The secondary battery according to claim 1 , wherein an average thickness of the electrolyte layer is from 0.1 μm to less than 8 μm.
9. The secondary battery according to claim 3 , wherein the negative electrode active material particles comprise at least one Ti-containing oxide selected from the group consisting of a Li—Ti oxide, a Ti oxide, a Nb—Ti oxide, and a Li—Na—Nb—Ti oxide.
10. The secondary battery according to claim 3 , wherein the negative electrode active material particles comprise at least one Ti-containing oxide selected from the group consisting of Li 4+x Ti 5 O 12 , wherein x satisfies −1≤x≤3, Li 2+x Ti 3 O 7 , Li 1+x Ti 2 O 4 , Li 1.1+x Ti 1.8 O 4 , Li 1.07+x Ti 1.86 O 4 , Li x TiO 2 , wherein x satisfies 0≤x, Li x TiO 2 , wherein 0≤x, when TiO 2 (B) is a structure before charging, a rutile structure or an anatase structure, when TiO 2 is a structure before charging, and Li a TiM b Nb 2± βO 7±σ , wherein 0≤a≤5, 0≤b≤0.3, 0≤β≤0.3, 0≤σ≤0.3M is at least one element selected from among Fe, V, Mo, and Ta.
11. The secondary battery according to claim 1 , wherein the electrolyte layer further comprises solid metal particles.
12. The secondary battery according to claim 1 , wherein there is substantially no gap between the electrolyte layer and each of the positive electrode and the negative electrode.
13. The secondary battery according to claim 1 , wherein there is no gap between the electrolyte layer and each of the positive electrode and the negative electrode.
14. The secondary battery according to claim 1 , wherein the thickness of the electrolyte layer is from 0.5 μm to 5 μm.
15. The secondary battery according to claim 1 , wherein the inorganic solid particles are completely contained in the recesses of the negative electrode.