Can the highest voltage of lithium battery break through 4.2v?

The parameter that describes lithium ion batteries(hereinafter referred to lithium battery) energy storage is energy density. Mathematically equivalent to voltage multiply lithium battery capacity. In order to effectively improve the capacity of lithium-ion batteries, people tend to use way to increase the battery capacity. However, limited to the nature of the raw materials, capacity improvement is always limited, so improving the voltage value of higher lithium battery storage capacity becomes another way. As we all know, lithium battery nominal voltage is 3.6 V or 3.7 V, the highest voltage is 4.2 V. Why can lithium battery voltage get a bigger breakthrough? In the end, this is decided by the lithium battery materials and structural properties.

The lithium battery voltage is determined by the electrode potential. Also known as electric potential difference or voltage potential difference, it is to measure charge in electrostatic field because of potential energy difference generated by the different physical quantities. Electrode potential is about 3 v lithium ion, lithium battery voltage with different materials have change. Such as, generally the rated voltage of 3.7 V lithium-ion batteries, full electric voltage of 4.2 V. while lithium iron phosphate batteries rated voltage of 3.2 V, full electric voltage of 3.65 V. In other words, the utility of lithium battery electric potential difference between the positive and negative can't more than 4.2 V, this is a kind of based on material and using security needs.

If Li/Li + the reference potential was A mu A relative on anode materials for electrochemical potential, mu C relative electrochemical potential as the anode material, Eg for electrolyte potential interval minimum electronic did not possess the energy levels and the highest level difference. So, decided to lithium battery voltage value is highest mu, mu C, Eg these three factors.

Mu A and mu C difference for lithium battery open circuit voltage (maximum voltage value), when the voltage value in Eg interval, can guarantee the normal work of the electrolyte." Work" means: the lithium battery through the electrolyte in the positive and negative electrode movement back and forth, but will not happen with the electrolyte REDOX reaction, thus ensuring the stability of cell structure. The electrochemical potential on anode materials are causing abnormal electrolyte work has two forms:

1, when the cathode electrochemical potential is higher than the electrolyte lowest electronic not possess energy level, the cathode electron will be seized, electrolyte, thus the electrolyte oxidation reaction products in anode materials particles form a solid-liquid interface layer, which can lead to negative may be damaged.

2, When the anode electrochemical potential high electronics has a level below the electrolyte, the electrons in the electrolyte can be the positive, so as to be electrolytic liquid oxygen, and reaction products in the anode material particles form a solid-liquid interface layer, which leads to the positive may be damaged.

However, the possibility of damage to the positive or negative, however, because of the existence of the solid-liquid interface layer and prevent the electron in further movement of the electrolyte and the positive and negative electrode, instead to protect the electrode material, that is, to a lesser degree of solid-liquid interface layer is "protective". The premise is: protective anode electrochemical potential is can a bit more than Eg interval, too much but not beyond. Now, for example, lithium battery cathode materials are mostly use graphite, it is just because of the graphite relative to the electrochemical potential of the Li/Li + electrode is about 0.2 V, slightly beyond the Eg interval (1 V ~ 4.5 V), but because of "protection" of the solid-liquid interface layer, make the electrolyte will not be further reduction, thus to stop the development of polarization reaction.5 v high voltage anode material, however, is beyond the commercial organic electrolyte Eg interval too much now, and therefore vulnerable to oxidation in the process of charging and discharging, as with the increase of number of charging and discharging capacity drops, reduce the service life.

Now see the open circuit voltage of lithium-ion batteries was chosen as 4.2 V, because the existing commercial lithium-ion batteries electrolyte Eg range from 1 V to 4.5 V, if the open circuit voltage is set to 4.5 V may improve lithium battery output power, but also increase the risk of battery charge, and the harm of overcharge has shown considerable data, there is no longer say more.

According to the above principle, people want to by raising the voltage value to improve the energy density of lithium-ion batteries, only two roads, one is found with high voltage anode material that matches the electrolyte, the second is for battery protective surface modification.

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