What are the positive and negative electrodes of a lithium ion battery?

For symbols -- plus is better than minus, long is better than short, so you can remember the battery symbol positive or negative.

For physical batteries, where having a bump is a positive pole. Like some electronic batteries, they write + for the positive pole, - for the negative pole.

The galvanic cell is a complete direct current circuit. The electrodes and electrolytes constitute the internal circuit, which is the chemical power supply. The wires connected on the two electrodes and the ammeter and other loads constitute the external circuit. The battery’s current flows from positive to negative in the outer circuit and from negative to positive in the inner circuit. The positive and negative electrodes can therefore be judged by the direction of the current (electrons in a metal conductor flow in the opposite direction from the current). In fact, that's a definition of positive and negative.

If you do not know the direction of the current, you can observe which pole loses electrons and which pole gains electrons, and then mark the direction of electrons (generally on the external circuit, the carrier on the internal circuit is a free ion rather than a free electron), you can also judge.

Of the two poles of a galvanic cell, the one where the electrons are lost are oxidized is the anode, and the one where the electrons are reduced is the cathode. In general, the anode in the galvanic cell is also a negative pole, and the cathode is a positive pole. However, it should be noted that anode and cathode poles and positive and negative poles are different concepts. The former is less used in galvanic cells and mainly describes the electrolytic cell.

If you don't know which electrode is oxidized and which electrode is reduced, you can try to write the electrode equation to see if there is no contradiction. But this method is generally more complex. Therefore, it can be generally judged as follows:

If the electrode reaction (oxide), then this electrode is negative;

Inert electrode (graphite, platinum, etc.) don't participate in the reaction, is positive;

Fuel cell and some other REDOX reaction, two electrodes are not involved in the reaction, the oxidant (O2) end in response to the electron, is positive.

The current goes from positive to negative, and the physical direction of the current is either the direction of the directional movement of the positive charge or the opposite direction of the directional movement of the negative charge, so the positive pole has to give away electrons (lost electrons, oxidized) and vice versa.

Positive electrode (cathode) is cobalt acid lithium and many ingredients, these substances on the aluminum foil.

lithium cobalt oxide is the main part of the chemical reaction used to produce charge and discharge (and graphite reaction, as described below).

The addition of components is to improve the performance of the battery, such as reducing internal resistance, increasing capacity, improving the performance of anti-collision, anti-explosion and anti-fire and so on. In particular, flame retardant materials were added.

The negative electrode (anode) is graphite (nanoscale toner), which is coated on copper foil.

Reaction equations as follows:

On a positive response for

LiCoO2 = = Li1 - charging xCoO2 + Xli++ Xe (electronic)

Reaction to occur on the cathode

6C+XLi++Xe=====LixC6

Attach:

A qualified lithium ion battery should meet the following conditions in terms of safety performance:

(1) Short circuit: no fire, no explosion

(2) Charging: no fire, no explosion

(3) the hot box test: no fire, no explosion (150 ℃ temperature 10 min)

(4) Needle thorn: no explosion (with 3 mm Ф penetrate cells)

(5) Tablet: no fire, no explosion (10 kg weight from 1 m high at the battery)

(6) Incineration: no explosion (gas flame grill battery)

So far, due to technological improvements, qualified lithium batteries have been very safe.

Lithium ion battery principle and technological process

First, principle

1.0 positive pole construction

LiCoO2 (cobalt acid lithium) + conductive agent (acetylene black) (PVDF) + + adhesive fluid (aluminum foil) positive

2.0 negative pole construction

Graphite + conductive agent (acetylene black) + thickening agent (CMC) + binder (SBR) + fluid (copper foil) negative

3.0 working principle

3.1 charging process

Pictured above a power source to recharge the battery, on the positive electron e running on the cathode through an external circuit is lithium ion Li + "jump" from the positive electrolyte, "climb" diaphragm winding holes, "swimming" arrived at the cathode, and would have run to come over together.

On a positive response for

LiCoO2 = = Li1 - charging xCoO2 + Xli++ Xe (electronic)

Reaction to occur on the cathode

6C+XLi++Xe=====LixC6

3.2 discharging process

Discharge is divided into constant current and constant resistance discharge. Constant current is actually in the external circuit with a variable resistance can change with the change of voltage. The essence of constant resistance discharge is to add a resistor to the anode and cathode of the battery to let electrons pass through. Therefore, as long as the cathode electron can't flow from the cathode to the anode, the battery will not discharge. Electrons and Li+ flow at the same time, in the same direction but in different paths. When discharging, electrons flow from the negative pole through the electronic conductor to the positive pole. Lithium ion Li+ "jumps" into the electrolyte from the negative pole, "climbs" through the small zigzagging holes on the diaphragm, "swims" to the positive pole and combines with electrons that have already come here.

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