Analyze lithium-ion batteries from a chemical perspective
Battery overview
Like all chemical batteries, lithium-ion batteries are composed of three parts: positive electrode, negative electrode, and electrolyte. The electrode materials are all lithium ions that can be inserted (inserted)/deintercalated (deintercalated).
Cathode material
Cathode material: There are many available cathode materials, and most mainstream products use lithium iron phosphate. Comparison of different cathode materials:
Cathode material
Average output voltage
Energy Density
LiCoO2
3.7 V
140 mAh/g
Li2MnO3
3.7 V
100 mAh/g
LiFePO4
3.2 V
130 mAh/g
Li2FePO4F
3.6 V
115 mAh/g
Positive electrode reaction: Lithium ions are intercalated during discharge, and lithium ions are deintercalated during charging. When charging: LiFePO4→ Li1-xFePO4 + xLi ++ xe- When discharging: Li1-xFePO4+ xLi ++ xe- →LiFePO4
Anode material
Anode material: graphite is mostly used. New research has found that titanate may be a better material. Negative reaction: Lithium ions are inserted during charging, and lithium ions are deintercalated during discharging. When charging: xLi++ xe-+ 6C → LixC6 When discharging: LixC6→ xLi++ xe-+ 6C
It is roughly divided into the following categories:
The first type is carbon anode materials: the anode materials actually used in lithium-ion batteries are basically carbon materials, such as artificial graphite, natural graphite, mesophase carbon microspheres, petroleum coke, carbon fiber, and pyrolytic resin carbon.
The second type is tin-based anode materials: tin-based anode materials can be divided into tin oxides and tin-based composite oxides. Oxide refers to the oxide of tin metal in various valence states. There are no commercial products.
The third type is a lithium-containing transition metal nitride anode material, which has no commercial products.
The fourth type is alloy anode materials: including tin-based alloys, silicon-based alloys, germanium-based alloys, aluminum-based alloys, antimony-based alloys, magnesium-based alloys and other alloys. There are no commercial products.
The fifth type is nano-scale anode materials: carbon nanotubes, nano-alloy materials.
The sixth type of nano material is nano oxide material: according to the latest trends in the market development of the new energy industry of lithium batteries in 2009, many companies have begun to use nano titanium oxide and nano silicon oxide to add to the previous traditional graphite, tin oxide, nano carbon Inside the tube, the charge and discharge capacity and the number of charge and discharge times of the lithium battery are greatly improved.
Electrolyte
Solute: Lithium salts are often used, such as lithium perchlorate (LiClO4), lithium hexafluorophosphate (LiPF6), and lithium tetrafluoroborate (LiBF4). Solvent: Since the working voltage of the battery is much higher than the decomposition voltage of water, organic solvents are often used in lithium-ion batteries, such as ether, ethylene carbonate, propylene carbonate, and diethyl carbonate. Organic solvents often damage the structure of graphite during charging, causing it to exfoliate, and forming a solid electrolyte interphase (SEI) on its surface to cause electrode passivation. Organic solvents also bring safety problems such as flammability and explosion.
Conductive coating
Battery coated carbon aluminum foil (conductive coating)
Advantages of carbon-coated aluminum foil in lithium-ion battery applications
1. Inhibit battery polarization, reduce thermal effects, and improve rate performance;
2. Reduce the internal resistance of the battery, and significantly reduce the dynamic internal resistance increase during the cycle;
3. Improve consistency and increase the cycle life of the battery;
4. Improve the adhesion between the active material and the current collector, and reduce the manufacturing cost of the pole piece;
5. Protect the current collector from being corroded by the electrolyte;
6. Improve the processing performance of lithium iron phosphate and lithium titanate materials.
Conductive coating
The surface treatment of battery conductive substrates with functional coatings is a breakthrough technological innovation. Carbon-coated aluminum foil/copper foil is to coat dispersed nano-conductive graphite and carbon coated particles evenly and delicately on aluminum foil/ On copper foil. It can provide excellent static electrical conductivity, collect the micro current of the active material, which can greatly reduce the contact resistance between the positive/negative electrode material and the current collector, and can improve the adhesion between the two, which can reduce the adhesion The amount of agent used, in turn, significantly improves the overall performance of the battery. The coating is divided into two types: water-based (aqueous system) and oil-based (organic solvent system).
Performance difference
Performance advantages of carbon-coated aluminum foil/copper foil
1. Significantly improve the consistency of the battery pack and greatly reduce the battery composition cost. like:
Significantly reduce the dynamic internal resistance increase of the battery cell;
Improve the consistency of the pressure difference of the battery pack;
Extend battery life;
Significantly reduce battery cost.
Significantly improve the consistency of battery pack usage
Significantly improve the consistency of battery pack usage
2. Improve the adhesive force of the active material and the current collector, and reduce the manufacturing cost of the pole piece. like:
Improve the adhesion of the positive electrode material and the collector using the water-based system;
Improve the adhesion of nano- or sub-micron cathode materials and collectors;
Improve the adhesion of lithium titanate or other high-capacity anode materials and collectors;
Improve the pass rate of pole pieces and reduce the cost of pole pieces.
Improve the adhesion of active materials and current collectors
Test chart of the adhesion of the battery pole piece of the carbon-coated aluminum foil and the light foil
After using carbon-coated aluminum foil, the adhesion of the pole piece is increased from the original 10gf to 60gf (using 3M tape or 100 grid knife method), and the adhesion is significantly improved.
3. Reduce polarization, increase rate and gram capacity, and improve battery performance. like:
Partially reduce the proportion of binder in the active material and increase the gram capacity;
Improve the electrical contact between the active material and the current collector;
Reduce polarization and improve power performance.
Reduce polarization, increase magnification and gram capacity
Reduce polarization, increase magnification and gram capacity
Battery rate performance graphs of different aluminum foils
Among them, C-AL is carbon-coated aluminum foil, E-AL is etched aluminum foil, and U-AL is light aluminum foil
4. Protect the current collector and prolong the service life of the battery. like:
Prevent corrosion and oxidation of current collector;
Improve the surface tension of the current collector and enhance the easy coating performance of the current collector;
It can replace higher-cost etched foils or replace the original standard foils with thinner foils.
Battery cycle curve diagram of different aluminum foils (200 weeks)
Among them (1) is light aluminum foil, (2) is etched aluminum foil, (3) is carbon-coated aluminum foil
