Secondary battery, battery pack, vehicle, and stationary power supply
摘要
說(shuō)明書(shū)
The specific surface area can be obtained by, for example, the following method. First, the secondary battery is disassembled, and a part of the negative electrode active material-containing layer is extracted. Next, the nitrogen gas adsorption amount (mL/g) of the sample is measured at each pressure P while a nitrogen gas pressure P (mmHg) is gradually increased in nitrogen gas at 77 K (boiling point of nitrogen). Then, an adsorption isotherm is obtained by plotting the adsorption amount of nitrogen gas with respect to each relative pressure P/P0. The relative pressure P/P0 is obtained by dividing the pressure P (mmHg) by a saturated vapor pressure P0 (mmHg) of nitrogen gas. Then, a BET plot is calculated from the nitrogen adsorption isotherm and the BET equation, and a specific surface area is obtained using the BET plot. For the calculation of the BET plot, a BET multipoint method is used.
As the negative electrode active material, a compound whose lithium ion insertion/extraction potential is 1 V (vs. Li/Li+) to 3 V (vs. Li/Li+) as a potential based on metal lithium can be used. That is, the secondary battery according to the first embodiment can maintain the hydrogen generation potential of the negative electrode in a low state after the initial charge, as described above. Hence, a material whose lithium ion insertion/extraction potential has a relatively small lower limit value can be used as the negative electrode active material of the secondary battery. When such a negative electrode active material is used, the energy density of the secondary battery can be raised. For this reason, the secondary battery can implement the same energy density as that of a battery using a nonaqueous electrolyte.
