A recent article on the Samsung graphene battery is rampant, in fact, this is not the so-called 'graphene' battery for the first time into people's vision, there have been reports on Huawei 'graphene' battery, but in the end have proved that, This is just a speculation by 'graphene', only the capital to attract people's attention.This report is Samsung's 'graphene' battery is also a speculation, or the real sense of 'graphene' battery? To this end We found the original text of Samsung's 'Graphene' battery papers that appeared in the article, for everyone to interpret.
This article from Samsung is published in the famous journal Nature Certificate, the original title of which is shown above. The Chinese translation of the title of the article is "Graphene Ball for Lithium Ion Battery with Fast Charge and High Volume Energy Density" As you can see from the title, this article is a paper on lithium-ion battery materials, and the title "graphene sphere" is actually a kind of graphene based on vacuum decomposition of graphene on the surface of SiOx particles Into a small ball, the 'graphene ball' that can be coated on the surface of high nickel cathode material to inhibit the occurrence of side effects, can also be used as a negative electrode material alone can be seen from the above description, the root mentioned in the original Not a so-called brand new 'graphene' battery, but a graphene-treated battery material.
Although this is not subversive 'graphene battery' in many media outlets, it is naturally no substitute for lithium-ion batteries, but from the introduction, this is still an excellent lithium-ion battery material, especially in improving lithium Fast charge performance of ion batteries, it is a very obvious advantage, so Xiaobian take everyone to understand, such a high-performance lithium-ion battery materials.
The "graphene sphere" (GB) in the article is actually In Hyuk Son which utilizes a vacuum decomposition technique of CVD with CH4 as a carbon source and reacts with SiO 2 with a diameter of 20-30 nm at 1000 ° C and the SiO 2 particles are reduced to SiOx , And the surface of the particles coated with a layer of graphene, the reaction formula is as follows.
One of the first things we think about as a material for such a material is that SiOx is indeed the most successful high-capacity negative electrode material yet, but Samsung scientists have taken the other approach by using 'graphene balls' as the surface coating material for high-nickel cathode materials , Coated on the NCM 613. Samsung has its own theory of doing so: Graphene as a good conductivity of the material is very suitable as a cathode coating material to improve conductivity and inhibit the occurrence of side effects, but because graphene sheets Strong electrostatic force makes it easy to agglomerate, resulting in graphene is difficult to evenly dispersed in the cathode material surface 'Graphene balls' can be a good solution to this problem, even in the 1% content Under the NCM613 can also be well dispersed in the material, the NCM particles form a protective layer on the surface to improve the interfacial stability of the material.
The graph below shows the electrochemical performance of the NCM613 coated with 'graphene balls' and the uncoated material. From the graphs a and b below, we can see that after the 'graphene ball' treatment Of the NCM material discharge capacity at a large magnification was significantly higher than the untreated material, especially when the difference is more obvious at 25 ° C. From Figure c and Figure d we can also note that at 4.3V, 4.4 The cycling performance of the NCM material after coating (solid sphere curve) at V and 4.5V cut-off voltage is significantly better than that of the control group, especially at 60 ℃, which is mainly due to the uniform The graphene coating significantly inhibits the occurrence of interfacial side reactions, thus preventing the NCM material from decaying from 'layered structure' to 'rock salt structure' and improving the cycling performance of NCM materials.
At the same time, thanks to the good conductivity of 'graphene balls', we can reduce the amount of SP used in NCM electrodes and increase the active material ratio from 92% to 97%, which greatly improves the Volumetric capacity, thereby increasing the volumetric energy density of lithium-ion batteries.
In addition to being a coating for NCM materials, 'Graphene Ball' GB can also be used alone as a negative electrode material for use with GB-NCM (Graphene Ball Coated NCM), enabling lithium-ion batteries to be rapidly recharged. As a negative electrode material 'graphene ball' capacity up to 716.2mAh / g (0.1C), in the good conductivity of graphene 'graphene' has excellent rate performance, at a rate of 10C is still Can exhibit a capacity of 240.6 mAh / g, which is 33.6% of the capacity under 0.1 C. 'Graphene balls' not only have excellent rate performance but also excel in cycle performance and cycle 500 times at 5 ° C. at 25 ° C., The rate of up to 88% at 60 ° C, 5C cycle 500 times, the capacity retention rate of up to 86.1% 'Graphene balls' in the whole battery also showed good cycling performance, especially at 60 ° C, did not pass The capacity of the treated NMC / graphite cells declines rapidly, but the GB-NCM / GB cells maintain good cycling performance (Figure e).
Of course, the problem of graphene balls as negative electrode material is that the first coulombic efficiency is low, which is mainly due to the larger specific surface area of graphene, which leads to more side reactions and consume more at low potential In order to solve this problem, In Hyuk Son used "graphene balls" as the anode material, which needs to be pre-lithiated firstly. Under the premise of the current immature lithium pre-lithiation technology, the first efficiency Lower is also a problem we need to seriously consider.
It is not difficult to see from the introduction above that the so-called Samsung 'graphene battery' is only a gimmick for speculation. In fact, it is essentially only a graphene / SiOx composite nanoparticle - 'graphene ball' and this type of 'graphite Ene ball 'is more suitable as a surface coating material of NCM material, to improve the interfacial stability of NCM material and improve the cycle performance; to improve the conductivity of NCM material and to improve the rate performance of NCM while benefiting from good graphene materials Conductivity, can significantly improve the proportion of the positive active material in the electrode, and increase the volume energy density of the lithium ion battery.
Although graphene balls can be used as an anode material and also have excellent rate and cycle performance, because of its low efficiency for the first time, it must be used in conjunction with a lithium replenishment process. Therefore, under the premise that lithium replenishment process is immature at this stage, 'Graphene ball' suitable for lithium-ion battery cathode material is also debatable.
Therefore, in general, this material should be referred to as 'new graphene additive for Li-ion batteries' rather than 'graphene batteries' touted by some media.
