Battery and battery manufacturing method

1. A battery comprising:

a case including a terminal insertion hole;

an electrode body housed in the case;

an internal terminal attached to the electrode body and mounted inside the case;

an external terminal disposed outside the case; and

at least one insulator disposed between the case and the internal terminal and between the case and the external terminal, wherein

the internal terminal includes

an internal terminal base disposed inside the case, with the insulator interposed between the internal terminal base and the case, and

a shaft extending from the internal terminal base, the shaft being disposed through the terminal insertion hole so that a portion of the shaft is disposed outside the case,

the external terminal includes

an external terminal base disposed outside the case, with the insulator interposed between the external terminal base and the case, and

a boss extending from the external terminal base, the boss receiving the shaft of the internal terminal therethrough, and

the boss is pressure-welded to the portion of the shaft of the internal terminal disposed outside the case, so that the boss is at least partially press-fitted to the shaft of the internal terminal, and atoms of the boss and the shaft are bonded to each other, wherein the boss is a tubular shaped protrusion that extends from the external terminal base in a direction away from the case.

2. The battery according to claim 1 , wherein

the shaft of the internal terminal has a deformation mark of plastic deformation that axially pulls the shaft toward outside of the case.

3. The battery according to claim 1 , wherein

an outer peripheral surface of the shaft is provided with protrusions and recesses.

4. The battery according to claim 1 , wherein

the boss is provided with a slit extending in a circumferential direction of the boss.

5. The battery according to claim 1 , wherein

the external terminal base is provided with a slit extending around the boss.

6. A battery manufacturing method comprising the steps of:

a) preparing a case component including a terminal insertion hole;

b) preparing an internal terminal including an internal terminal base and a shaft extending upward from the internal terminal base, the shaft being insertable through the terminal insertion hole;

c) preparing an external terminal including an external terminal base and a boss extending upward from the external terminal base, the boss being configured to receive the shaft therethrough, wherein the boss is a tubular shaped protrusion that extends from the external terminal base in a direction away from the case component;

d) assembling the internal terminal to the case component such that the shaft is inserted through the terminal insertion hole, with an insulator interposed between the case component and the internal terminal base, and the internal terminal base is disposed inside the case component;

e) assembling the external terminal to the case component and the internal terminal such that the boss is fitted to the shaft inserted through the terminal insertion hole, with the insulator interposed between the external terminal base and the case component, and the external terminal base is disposed outside the case component; and

f) performing pressure welding involving disposing a coil including an electric wire wound around the boss, and passing a current through the coil such that a radially inward force is exerted on the boss so as to deform the boss radially inward and pressure-weld the boss to the shaft of the internal terminal.

7. The battery manufacturing method according to claim 6 , wherein

step f) involves passing the current through the coil, with the shaft pulled upward and the external terminal pressed downward.

8. The battery manufacturing method according to claim 6 , wherein

step f) involves disposing a first restrictor to restrict deformation of the shaft, the first restrictor being disposed above the shaft.

9. The battery manufacturing method according to claim 6 , wherein

step f) involves disposing a second restrictor to restrict deformation of the insulator, the second restrictor being disposed around the insulator.

10. The battery manufacturing method according to claim 6 , wherein

step f) involves disposing a third restrictor to restrict deformation of the external terminal base, the third restrictor being disposed on the external terminal base.