How to distinguish the positive and negative poles of 18650 batteries

The positive electrode (cathode) is lithium cobaltate and a number of additive components which are applied to the aluminum foil.

Lithium cobaltate is the main part of the chemical reaction used to generate charge and discharge (and graphite reaction, as described below). Adding ingredients is to improve the performance of the battery, such as reducing internal resistance, increasing capacity, and improving performance against impact, explosion, and fire. In particular, flame retardant materials have been added.

The negative electrode (anode) is graphite (nano-sized carbon powder), and these are 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) Burned: no (a gas explosion flame barbecue battery)

So until now, qualified lithium batteries have been safe due to process improvements.

Lithium ion battery principle and technological process

Principle

1.0 The anode structure

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

2.0 The cathode structure

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

3.0 working principle

3.1 The 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 The battery discharge process

Electric discharge has permanently exile and constant resistance discharge, electricity is actually in the external circuit with a constant exile can changes over voltage variable resistance, constant resistance discharge is of the essence of the battery is negative and a resistor through electronic. Therefore, as long as the cathode electron can't run away from the cathode to the anode, the battery will not discharge. Electronic and Li + is action at the same time, in the same direction is different, but the road is discharging, electrons from the cathode through electronic conductor ran to the anode, lithium ion Li + from the cathode "jump" in the electrolyte, "climb" diaphragm winding holes, "swimming" to the anode, and would have run to come over together.

Discriminating method

1. See screen printing: screen printing is screen printing, general is left is right;

2. Look at the shape of the two ends: the end with the bump is positive, the flat bottom is negative;

3. Using multimeter measurement: red and black test pen, in the case of a positive number, the red line is +, black is -, when the negative number is displayed, the red test lead corresponds to the -electrode, and the black corresponds to the + electrode;

4. Look at the shape, change the model battery is generally the original shape, see the insulation at both ends, one end has a concave ring, one end is not, some are positive, not negative;

5. Some manufacturers do not follow the battery standard, logo production, then the actual measurement and consulting manufacturers, request specifications;

In the common sense of life, it is generally seen whether there is a positive or negative sign on the top, or that the usually flat end is negative, and the raised one is positive.

However, a scientific method can be used to install the battery on a circuit with an ammeter. If the ammeter is deflected normally in the positive direction, the positive pole of the terminal is connected to the positive pole of the battery, and the negative pole is connected to the negative pole of the battery. If the ammeter is deflected in the reverse direction, the positive electrode is connected to the negative electrode. Or if you look at the electrolyte solution, the positive and negative phases attract, so the anion collects the positive electrode, and the cation accumulates the negative electrode (it is recommended use colored electrolytes such as potassium permanganate, color after the power supply will be separate, purple side is the anode, the end which is colorless cathode)

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