Nonaqueous electrolyte secondary battery
A nonaqueous electrolyte secondary battery includes a positive electrode, a nonaqueous electrolytic solution, and a negative electrode. The negative electrode includes a negative electrode current collector and a negative electrode active material layer which is formed on the negative electrode current collector. The negative electrode active material layer has a first region and a second region. The first region is a region formed on a surface of the negative electrode current collector and contains lithium titanium composite oxide as a major component. The second region is a region including a surface of the negative electrode active material layer and contains lithium titanium composite oxide as a major component and further contains silicon oxide.
1. A nonaqueous electrolyte secondary battery characterized by comprising:
a positive electrode;
a nonaqueous electrolytic solution; and
a negative electrode, the negative electrode including a negative electrode current collector and a negative electrode active material layer which is formed on the negative electrode current collector,
the negative electrode active material layer having a first region and a second region,
the first region being a region formed on a surface of the negative electrode current collector and contains lithium titanium composite oxide as a major component, and
the second region being a region including a surface of the negative electrode active material layer and contains lithium titanium composite oxide as a major component and further mixes with silicon oxide, wherein
a content of silicon oxide in the first region and M 2 SiO satisfy the following relationship:
M 1 SiO <M 2 SiO
wherein M 1 SiO represents the content of silicon oxide in the first region in terms of mass %, M 2 SiO represents the content of silicon oxide in the second region in terms of mass %.
2. The nonaqueous electrolyte secondary battery according to claim 1 , wherein
a ratio of an average thickness of the second region to an average thickness of the negative electrode active material layer is 1% to 50%.
3. The nonaqueous electrolyte secondary battery according to claim 1 , wherein a content of lithium titanium composite oxide in the second region and a content of silicon oxide in the second region satisfy the following relationship:
1<M 2 SiO /(M 2 LTO +M 2 SiO )×100≤7
wherein M 2 LTO represents the content of lithium titanium composite oxide in the second region in terms of mass %.
4. The nonaqueous electrolyte secondary battery according to claim 1 , wherein
a mass per unit area of the negative electrode active material layer in the first region is 30 mg/cm 2 to 50 mg/cm 2 .
5. The nonaqueous electrolyte secondary battery according to claim 1 , wherein
an overall density of the negative electrode active material layer is 2 g/cm 3 to 3 g/cm 3 .
6. The nonaqueous electrolyte secondary battery according to claim 1 , wherein
the first region contains silicon oxide.
7. The nonaqueous electrolyte secondary battery according to claim 1 , characterized in that
the content of silicon oxide in the first region is zero.