In 2012, Great Wall Motors decided to carry out research and development of lithium-ion batteries and established a battery project team. Then, in order to fulfill its promise of electrification to the world, the power battery division became independent and established Hive Energy. Change and renewal seem to be the principles set by Honeycomb Energy from the beginning. This is not only the result of a battery factory, but also the ambition of a car brand behind it.
On May 18, Honeycomb Energy, a power battery company independent from Great Wall Motors, announced the official launch of cobalt-free batteries. This cobalt-free battery is truly cobalt-free, replacing traditional nickel-cobalt batteries. The cobalt element in the manganese battery is stripped out, and the cathode material is only nickel-manganese, achieving the goal of zero cobalt content.
Honeycomb Energy is not just talking on paper, but putting its ideas into practice. It launched two cobalt-free batteries at the press conference. One has an energy density of 245Wh/kg, a capacity of 115Ah, and a cruising range of Reaching 600km, it will be officially mass-produced before June next year; the other battery has a capacity of 226Ah, an energy density of 240Wh/kg, and a cruising range of 880km, and will also be mass-produced in the second half of next year.
In recent years, battery manufacturers have been committed to the development of cobalt-free batteries, but so far there has been no real commercialization of cobalt-free batteries. So, is cobalt really that important in batteries?
Yes, it is that important. When lithium-ion batteries operate under high current density conditions during charge and discharge cycles, the cathode material becomes more unstable during the battery reaction and the electrolyte circulates. A barrier film will be formed on the surface of the material, which increases the impedance of the battery and also causes the deterioration of the electrode material. The collapse of the structure makes it more difficult for lithium ions to be embedded, thus affecting the current and voltage output by the battery and creating safety hazards.
Simply put, without cobalt, the life and safety of the battery will be reduced.
Then, to extend battery life and improve battery safety, slowing down the formation of barrier films on the material surface and maintaining the structure of the electrode material are key.
Cobalt can play this role.
Taking the most widely used nickel-cobalt lithium NCM battery as an example, the addition of cobalt can stabilize the layered structure of the cathode material and improve the cycle and rate performance of the material.
But Cobalt only plays a role in stabilizing the structure of the battery and does not participate in the charge and discharge reactions. In an electrode of the same quality, an increase in the cobalt content will reduce the lithium content, ultimately leading to a low energy density of the battery.
In addition, the content of cobalt resources is unevenly distributed around the world. The composition of cobalt ore is complex, mining is difficult, and procurement costs remain high. In an environment that is unfriendly, cobalt is likely to become a stranglehold on battery production. The hand of fate affects production capacity and battery development.
In other words, from the perspective of cost and battery capacity, the removal of cobalt from batteries is the general trend.
So, how can cobalt-free batteries solve the lifespan problem mentioned above?
Honeycomb Energy officials stated that there are three core technologies for cobalt-free batteries: cation doping technology, single crystal technology, and nano-network coating.
The current is transmitted inside the battery by lithium ions shuttling between the positive and negative electrodes and reacting to conduct electricity. The role of nickel is to increase the volume energy density of the material. In cobalt-free high-nickel cathode materials, the valence states of the active element nickel are divalent and trivalent. When the manganese content is too high, the divalent ions of nickel will also The more divalent nickel ions and lithium ions have similar ionic radii, some of them will migrate into the Li layer.
In short, divalent nickel ions can easily replace the sites of lithium ions. As a battery reactant, lithium ions have nowhere to go and there is no way to react. Not only will the capacity of the material be reduced, but the impedance of the material will also be increased.
Honeycomb Energy said that it used two more stable elements instead of cobalt to dope the material, establishing a more stable octahedral structure to reduce the mixing of lithium and nickel, and greatly improved the stability of the material, which can be used in 4.3 - Stable operation at 4.35V voltage without significant reduction in energy density.
Studies have proven that doping niobium and zirconium dioxide (yes, the zirconium that can be disguised as diamond) in the cathode material can improve the cycle performance of the battery, and the voltage operating range is basically stable at 4.35 Around V; replacing Co elements with Al and Mg can also obtain a very low lithium-nickel mixing rate.
In other words, Honeycomb has found a substance that can replace cobalt in the electrode, which can improve the safety and cycle life of cobalt-free batteries while ensuring battery capacity density.
However, it should be noted that the relevant research is only tested in the laboratory. If Honeycomb Energy discloses more details in the future, we can have another taste.
During the growth process of a crystal, multiple crystal nuclei are often produced at the same time. If these crystal nuclei grow into grains with the same crystal plane orientation, a single crystal is formed. If these crystal nuclei have different crystal plane orientations during growth, polycrystals will form. You can imagine that every piece of clothing in the wardrobe is neatly arranged or piled up in a mess. This is the difference between single crystal and polycrystalline.
In the electrode manufacturing process, high-intensity roller pressing is required to attach more active substances to the pole piece. Polycrystalline materials will cause reactions between the positive electrode and the electrolyte during the process, and will also cause changes in the material structure. collapse, battery life is reduced, and safety performance is reduced.
Compared with polycrystalline, single crystal has higher strength and better electrical properties, which gives the electrode material a longer working life and higher energy conversion efficiency, so it is speculated that the so-called honeycomb Single crystal technology means that the lithium nickel manganese oxide of the positive electrode uses single crystal material.
In traditional NCM batteries, cobalt can not only stabilize the structure during the reaction, but also improve the instability of polycrystalline materials. However, after the battery was decobalted, Honeycomb Energy chose to replace polycrystalline materials with monocrystalline materials to extend battery life.
However, Honeycomb's cobalt-free batteries are doped with transition metal oxides. This material will decompose to generate oxygen under high oxidation state and high temperature, which will not only cause the battery pack to expand but also support combustion. The characteristics of this material itself cannot be modified through chemical methods for the time being, which means that the battery structure can only be improved to control the spread of battery thermal runaway. In other words, it is necessary to keep up with the thermal management system to delay the escape time of the occupants after an accident.
Judging from the information currently disclosed by Honeycomb, the safety of cobalt-free batteries is definitely not as stable as that of nickel-cobalt-manganese ternary batteries.
During the use of the battery, the electrolyte on the surface of the positive and negative electrodes will undergo oxidative decomposition at high voltages, resulting in an increase in the impedance and capacity decline of the lithium-ion battery.
What Honeycomb Energy does is to wrap a layer of material (nano-oxide) on the positive electrode material to reduce the occurrence of side reactions during the charge and discharge process and improve the cycle performance and rate performance of the material.
However, common oxide or carbon as a coating layer will hinder the diffusion of lithium ions, which will instead reduce the energy of the cathode material. It is speculated that fast ion conductors with a three-dimensional spatial configuration may be used for coating, such as silica and alumina, which are relatively low-cost and relatively stable materials, and are also conducive to the deintercalation and insertion of lithium ions in the positive electrode.
It can be understood as adding a door outside the positive electrode of the battery, and lithium ions can pass in and out. This door can also "suppress the house", allowing the electrolyte to stop useless self-consumption, which is what we call side reactions. , which can not only slow down the decline of battery capacity, but also ensure the cycle stability of the battery.
In general, Honeycomb Energy’s cobalt-free batteries have improved the existing NCM batteries in three aspects: lithium-nickel mixing, cobalt-stabilized cathode material structure, and high-voltage oxidation and decomposition of the electrolyte. The impact on enterprises is that the cost of automobiles has dropped significantly, which is good for both the industry and consumers.
But is this so-called cobalt-free battery really that powerful? I don’t think so.
The battery launched by Honeycomb at this conference is not a black technology or a new technology. In essence, it is a cathode material based on nickel manganese lithium. This type of material has always been one of the hot topics in the research of cathode materials for lithium-ion batteries, but most of these are limited to laboratory research. Cobalt-containing batteries and lithium iron phosphate batteries still occupy the majority of the market share. Compared with common NCM batteries, although the cycle performance is better, the battery energy density will be reduced. This time, Hive has pushed these technologies from the laboratory to the production line, and must have designed a complete and mature production process.
But we still have to applaud Hive Energy. If this cobalt-free battery can really achieve a cruising range of more than 800km after mass production, Hive Energy will be the first in the world to implement this system. Enterprises that have reached the experimental stage of mass production. New breakthroughs in the field of battery technology are a blessing for both the industry and individuals.
Honeycomb Energy also revealed that in theory, the number of cycles of this cobalt-free battery can reach 3,000 times, which means that the vehicle’s full life cycle mileage can reach 1.2 million kilometers. Although this achievement cannot be said to be outstanding Tesla’s million-mile battery, but there is absolutely no problem in taking the battery life of domestic independent brands of pure electric vehicles to a higher level.
There is less than a year until mass production next year. Are you looking forward to this gift from Honeycomb Energy?