How to calculate the theoretical capacity of battery material value

C = 26.8 nm/M, n is the number of electronic, M is the active material quality, M is the molecular weight of active substances

The formation of batteries, some use normal temperature, and some use high temperature formation, the advantages and disadvantages of these two formations:

The main difference should be the thickness and density of the SEI film. The SEI formed by the high temperature formation is thick but not dense, and consumes more lithium, and is thinner and denser at normal temperature or low temperature.

Battery formula:

Negative formula: CMS: CMC: SBR: Super - P = 94.5:2.25:2.25:1

The electrolyte: 1 m - LiPF6EC/DMC/EMC

The cathode design specific capacity: 300mah/g

The positive design specific capacity: 140mah/g

Charge and discharge system: 1) the constant current charging (1 c, 4.2 V)

2) Constant voltage charging (4.2 V, 20 ma)

3) Rest (10min)

4) Constant current discharge (1C, 3.0V)

5) Rest (10min)

6) Cycle (350 weeks)

The dissolution of polymer in solvent should follow three principles (polarity similarity principle, the principle of solvation, cohesive energy density similar principles), the three principles of combining the solubility parameter values of the polymer and solvent, is to choose the basis of a good polymer solvent. PVDF polymer/solvent/NMP was a good match, but polar solvent NMP is high, and the water affinity is very good, so easy to moisture absorption, along with the increase of the content of moisture NMP formation of NMP/water mixed solvent solubility parameter, polarity, solvation capacity to drift, and the corresponding values of PVDF and no change, PVDF/NMP adhesive solution with the increase of water content, gradually become unstable, the water content reaches a certain value, PVDF can precipitate from solution, and in the process, the nature of the solution, including viscosity, adhesive performance, etc all make a change. Drops of water in the PVDF/NMP solution, local form bad solvent environment, there will be PVDF precipitation.

Different ingredients technology by combining and the corresponding formula, as well as provides a general formula:

LiCoO2: conductive graphite 92% : 92% conductive agent: PVDF: 2.5% 3.0%

The positive electrode active material was 80%, acetylene black was 10%, and PVDF was 10%.

Enterprise formula:

Cobalt acid lithium 94% conductive agent 1% conductive agent PVDF3%1%

Negative roughly can be thought of as the SEI film on the surface of the organic solvent by reductive decomposition of electrolyte of insoluble product attached on the surface of the electrode, as a result, the different anode materials have some differences, but there are generally considered to be: lithium carbonate, alkyl lithium, lithium hydroxide, etc, of course, there are salt decomposition product, there are some polymer, etc. It is generally considered that for metallic lithium, the negative electrode forms an SEI film when lithium is first implanted, and the formation voltage starts at 1.5 V (relative to metallic lithium), and is formed in a large amount near 0.8 V, and is substantially completed up to about 0.2 V. In addition, the study shows that the first step of SEI film formation during lithium intercalation is the formation of SEI film within 5 weeks, but rarely. In addition of SEI is not fixed, there will be a little change in the process of charging and discharging, mainly is the partial organic reversible change will happen. In addition to different current density, different electrode surface composition of the SEI film formed by the difference.

There are few SEI films on the surface of the positive electrode, and there has been little attention in the past. At present, it seems that the degree of attention is rising. One viewpoint is believed to be the result of the deposition of the oxidation product of the electrolyte, and the other viewpoint is the result of deposition on the surface of the positive electrode after partial dissolution of the SEI film on the surface of the negative electrode. Relatively speaking, there is not much evidence of oxidative deposition of electrolyte on the surface of the positive electrode. Of course, it is not excluded that the current instrument accuracy cannot be achieved due to the small amount.

Why should the cathode with copper foil and the anode aluminum foil to use

1, using both do set fluid because of both good electrical conductivity, the texture is soft (maybe this will be helpful for bonding), also relatively common is cheap, also can form a layer of the surface oxide film.

2, copper surface oxide layer belong to the semiconductor, electronic conductivity, the oxide layer is too thick, impedance; Surface oxidation layer of alumina insulators, and aluminum oxide layer cannot conduct electricity, but because of its very thin, through the tunnel effect to realize electronic conductivity, if the oxide layer thicker, aluminum foil conductive differential, and insulation. General set of best go through surface cleaning fluid before use, wash oil, on the one hand can remove thick oxide layer at the same time.

3, the anode potential, high aluminum thin oxide layer is very dense, can prevent the oxidation of the collection of fluid. And oxidation of copper foil layer is loose, to prevent the oxidation, better potential is low, at the same time, Li harder with Cu form embedded lithium alloy under the low potential, but if a large number of oxide copper surface, under the high potential Li will send should be embedded with copper oxide lithium.AL foil cannot be used as the anode, under low potential LiAl alloying will happen.

4, set fluid composition of pure.AL composition is not pure lead to surface film density and point corrosion, even more so due to disruption of the surface film generated LiAl alloy.

Pole piece weight for active material weight and the substrate (aluminum or copper) weight, weight minus the positive pole piece is designed according to the theory of substrate (copper aluminum density 2.7, 8.9), the weight of the active material weight, active material weight multiplied by 140mAh/g (cobalt acid lithium), how many MAH capacity of design, the cathode capacity is calculated based on 1.05 1.1 times as much as the anode, the method, the cathode calculated at 300-330mAh/g

Formula:

Lithium ion batteries theoretical capacity = (thickness - 2 * wall thickness) * (width to 2 * wall thickness) * (length - 2 * wall thickness)/being negative segregation estimates parameters of film thickness / 100 * coating density of the parameters for the design of the anode * capacity ratio

Among them:

0.0244 is the design of the anode coating density, actually about the same

0.45 is being negative segregation estimates parameters of film thickness

140 capacity ratio

But according to the calculation of the theoretical capacity of 063048, only 555mah (thickness calculated at 6.3), the capacity can only make scrap processing.

(6.3 0.35 * 2) * (30-0.35 * 2) * (48-0.35 * 2) / 0.45/100 * 0.0244 * 140 = 555

In general, natural graphite coated anode, the irreversible capacity is larger. MCMB is better from the result of the experiment. There is another, SEI film of membrane potential is from 1.2 V to 0.8 V (vs Li/Li +), embedded Lithium electricity0.25 ~ 0 v, the potential embedded in the lithium is reversible. If the SEI film can be formed at a higher potential, it can prevent further reduction of the solvent and reduce the irreversible capacity, that is, the polarization of the irreversible capacity in the first charging curve is relatively large, and it is easy to fall to the lithium-plated platform, thus forming the reversible capacity is high. The SEI membrane plays a vital role in the cycle performance of the battery. There is no good SEI membrane, and there is a large irreversible capacity loss per cycle. Such a battery can usually be absorbed from the electrolyte or can be seen when there is crystal water inside the battery.

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