Lithium-ion Battery Principles and Manufacturing Process I. Principle 1.0 Positive Electrode Structure: LiCoO2 (lithium cobalt oxide) + conductive agent (acetylene black) + binder (PVDF) + current collector (aluminum foil) Positive Electrode 2.0 Negative Electrode Structure: Graphite + conductive agent (acetylene black) + thickener (CMC) + binder (SBR) + current collector (copper foil) Negative Electrode 3.0 Working Principle 3.1 Charging Process: The power supply charges the battery. At this time, electrons e from the positive electrode travel through the external circuit to the negative electrode. Positive lithium ions Li+ "jump" from the positive electrode into the electrolyte, "crawl" through the winding holes in the separator, and "swim" to the negative electrode, where they combine with the electrons that have already traveled there.
Lithium-ion battery principle and process flow
Lithium-ion battery principle and process flow
I. Principle
1.0 Positive Electrode Structure
LiCoO2 (lithium cobalt oxide) + conductive agent (acetylene black) + binder (PVDF) + current collector (aluminum foil) positive electrode
2.0 Negative Electrode Structure
Graphite + conductive agent (acetylene black) + thickener (CMC) + binder (SBR) + current collector (copper foil) negative electrode
3.0 Working Principle
3.1 Charging process
When the power source charges the battery, electrons e on the positive electrode travel through the external circuit to the negative electrode. Positive lithium ions Li+ jump from the positive electrode into the electrolyte, crawl through the winding holes in the separator, and swim to the negative electrode, where they combine with the electrons that have already arrived.
The reaction that occurs at the positive electrode is
LiCoO2 = charging = Li1-xCoO2 + Xli+ + Xe (electrons)
The reaction that occurs at the negative electrode is
6C+XLi++Xe=====LixC6
3.2 Battery Discharge Process
There are two types of discharge: constant current discharge and constant resistance discharge. Constant current discharge involves adding a variable resistor to the external circuit that changes with voltage. Constant resistance discharge essentially involves adding a resistor to the positive and negative terminals of the battery to allow electrons to pass through. Therefore, the battery will not discharge as long as electrons at the negative terminal cannot move to the positive terminal. Electrons and Li+ ions move simultaneously, in the same direction but along different paths. During discharge, electrons travel from the negative terminal through the electron conductor to the positive terminal, while lithium ions (Li+) "jump" into the electrolyte from the negative terminal, "crawl" through the winding holes in the separator, and "swim" to the positive terminal, where they combine with the electrons that have already arrived.
II. Process Flow
III. Battery Defects and Their Causes:
1. Low capacity
Causes:
a. Insufficient material content; b. Significant difference in material content between the two sides of the electrode; c. Electrode breakage;
d. Insufficient electrolyte; e. Low electrolyte conductivity; f. Positive and negative electrode plates not properly matched;
g. Low diaphragm porosity; h. Adhesive aging → material detachment; i. Excessively thick core (not dried or electrolyte not penetrated).
j. Not fully charged during capacity testing; k. Small specific capacity of positive and negative electrode materials.
2. High internal resistance
Causes:
a. Poor soldering between the negative electrode and the tab; b. Poor soldering between the positive electrode and the tab; c. Poor soldering between the positive tab and the cap;
d. Poor soldering between the negative electrode lug and the shell; e. High internal resistance between the rivet and the pressure plate; f. No conductive agent added to the positive electrode;
g. The electrolyte contains no lithium salts; h. The battery has experienced a short circuit; i. The separator paper has low porosity.
3. Low voltage
Causes:
a. Side reactions (electrolyte decomposition; impurities at the positive electrode; presence of water); b. Incomplete formation (SEI film not yet formed for safety);
c. The customer's circuit board is leaking current (referring to the battery cells returned after customer processing); d. The customer did not spot weld the battery cells as required (after customer processing);
e. Burrs; f. Micro-short circuit; g. Dendrite formation at the negative electrode.
4. Extra thick
The reasons for excessive thickness are as follows:
a. Air leakage at the weld; b. Electrolyte decomposition; c. Insufficient moisture removal;
d. Poor sealing of the cap; e. Shell wall too thick; f. Shell too thick;
g. The core is too thick (too much material; the electrode sheet is not compacted; the diaphragm is too thick).
5. The causes are as follows:
a. Incomplete or incomplete SEI film formation; b. Baking temperature too high → binder aging → material release; c. Low specific capacity of negative electrode;
d. There is too much material attached to the positive electrode and too little material attached to the negative electrode; e. The cap leaks air and the weld leaks air; f. The electrolyte decomposes and the conductivity decreases.
6. Explosion
a. The capacity divider is faulty (causing overcharging); b. The diaphragm has poor closure; c. Internal short circuit.
7. Short circuit
a. Dust; b. Tear during packaging; c. Scratching (the diaphragm paper is too small or not properly padded);
d. Uneven winding; e. Not properly wrapped; f. Holes in the diaphragm; g. Burrs
8. Circuit break
a) The tab and rivet are not properly welded, or the effective weld area is small;
b) The connecting piece is broken (the connecting piece is too short or it is welded too low when spot-welded to the electrode).
Lithium-ion battery principle and process flow
Lithium-ion battery principle and process flow
I. Principle
1.0 Positive Electrode Structure
LiCoO2 (lithium cobalt oxide) + conductive agent (acetylene black) + binder (PVDF) + current collector (aluminum foil) positive electrode
2.0 Negative Electrode Structure
Graphite + conductive agent (acetylene black) + thickener (CMC) + binder (SBR) + current collector (copper foil) negative electrode
3.0 Working Principle
3.1 Charging process
When the power source charges the battery, electrons e on the positive electrode travel through the external circuit to the negative electrode. Positive lithium ions Li+ jump from the positive electrode into the electrolyte, crawl through the winding holes in the separator, and swim to the negative electrode, where they combine with the electrons that have already arrived.
The reaction that occurs at the positive electrode is
LiCoO2 = charging = Li1-xCoO2 + Xli+ + Xe (electrons)
The reaction that occurs at the negative electrode is
6C+XLi++Xe=====LixC6
3.2 Battery Discharge Process
There are two types of discharge: constant current discharge and constant resistance discharge. Constant current discharge involves adding a variable resistor to the external circuit that changes with voltage. Constant resistance discharge essentially involves adding a resistor to the positive and negative terminals of the battery to allow electrons to pass through. Therefore, the battery will not discharge as long as electrons at the negative terminal cannot move to the positive terminal. Electrons and Li+ ions move simultaneously, in the same direction but along different paths. During discharge, electrons travel from the negative terminal through the electron conductor to the positive terminal, while lithium ions (Li+) "jump" into the electrolyte from the negative terminal, "crawl" through the winding holes in the separator, and "swim" to the positive terminal, where they combine with the electrons that have already arrived.
II. Process Flow
III. Battery Defects and Their Causes:
1. Low capacity
Causes:
a. Insufficient material content; b. Significant difference in material content between the two sides of the electrode; c. Electrode breakage;
d. Insufficient electrolyte; e. Low electrolyte conductivity; f. Positive and negative electrode plates not properly matched;
g. Low diaphragm porosity; h. Adhesive aging → material detachment; i. Excessively thick core (not dried or electrolyte not penetrated).
j. Not fully charged during capacity testing; k. Small specific capacity of positive and negative electrode materials.
2. High internal resistance
Causes:
a. Poor soldering between the negative electrode and the tab; b. Poor soldering between the positive electrode and the tab; c. Poor soldering between the positive tab and the cap;
d. Poor soldering between the negative electrode lug and the shell; e. High internal resistance between the rivet and the pressure plate; f. No conductive agent added to the positive electrode;
g. The electrolyte contains no lithium salts; h. The battery has experienced a short circuit; i. The separator paper has low porosity.
3. Low voltage
Causes:
a. Side reactions (electrolyte decomposition; impurities at the positive electrode; presence of water); b. Incomplete formation (SEI film not yet formed for safety);
c. The customer's circuit board is leaking current (referring to the battery cells returned after customer processing); d. The customer did not spot weld the battery cells as required (after customer processing);
e. Burrs; f. Micro-short circuit; g. Dendrite formation at the negative electrode.
4. Extra thick
The reasons for excessive thickness are as follows:
a. Air leakage at the weld; b. Electrolyte decomposition; c. Insufficient moisture removal;
d. Poor sealing of the cap; e. Shell wall too thick; f. Shell too thick;
g. The core is too thick (too much material; the electrode sheet is not compacted; the diaphragm is too thick).
5. The causes are as follows:
a. Incomplete or incomplete SEI film formation; b. Baking temperature too high → binder aging → material release; c. Low specific capacity of negative electrode;
d. There is too much material attached to the positive electrode and too little material attached to the negative electrode; e. The cap leaks air and the weld leaks air; f. The electrolyte decomposes and the conductivity decreases.
6. Explosion
a. The capacity divider is faulty (causing overcharging); b. The diaphragm has poor closure; c. Internal short circuit.
7. Short circuit
a. Dust; b. Tear during packaging; c. Scratching (the diaphragm paper is too small or not properly padded);
d. Uneven winding; e. Not properly wrapped; f. Holes in the diaphragm; g. Burrs
8. Circuit break
a) The tab and rivet are not properly welded, or the effective weld area is small;
b) The connecting piece is broken (the connecting piece is too short or it is welded too low when spot-welded to the electrode).
