At present, new energy vehicle power batteries mainly use new battery technology such as ternary lithium batteries and lithium iron phosphate batteries.
According to the data, in 2021, the installed capacity of ternary lithium batteries in China will be 74.3GWh, accounting for 48.1%, and the installed capacity of lithium iron phosphate will be 79.8GWh, accounting for 51.7%. And the layout of ternary power battery is mature in China. Here is a top 10 ternary power battery manufactureres in China article. The two account for nearly 100% of the power battery market.
The core advantage of ternary batteries is energy density, and the disadvantage is cost and safety performance, while the core advantage of lithium iron phosphate is cost and safety performance, and the disadvantage is energy density.
On this basis, material factories, battery factories, and vehicle manufacturers have continuously introduced new materials and new battery technology in order to achieve a relative balance between battery energy density, cost, and safety.
At present, the positive electrode materials of power battery technology mainly include NCM and LFP. NCM materials are named ternary materials because they contain three elements: Ni, Co, and Mn. The so-called cobalt-free batteries cancel the Co element on the basis of NCM materials. That is, it can be understood as an NMx binary battery technology.
Due to the small amount of Co reserves, the crustal abundance is only 0.0025%, and most of the Co resources are produced in the Congo, which cannot stably support the full electrification process of automobiles in the future, and is expensive.
Therefore, the cost of materials can be reduced by canceling the Co element, and the dependence on the Co element can be avoided. However, the Co element can stabilize the layered structure of the material and reduce the mixing of Li+/Ni2+, thereby improving the cycle and rate performance.
The removal of the Co element will inevitably have adverse effects on the material performance. In order to solve this problem, SVOLT made the following changes to the cobalt-free material.
Doping with unpaired electron spin elements reduces Li+/Ni2+ mixing and improves rate performance. Doping elements with large M-O bond energy stabilizes the octahedral structure of O, slows down the volume change of the unit cell during the Li+ insertion/extraction process, and improves cycle performance.
Different from polycrystalline materials (primary particles are agglomerated into secondary balls), single crystal materials are single dispersed particles with a more stable crystal structure, which can greatly improve the cycle performance and safety performance of the battery technology under high voltage.
Nano network coating
A layer of nano-oxide is coated on the surface of the single crystal particles to reduce the side reaction between the positive electrode material and the electrolyte, thereby effectively improving the cycle stability under high voltage.
NCMA quaternary battery technology means that the material contains four elements: Ni, Co, Mn, and Al, that is, the fourth element is doped in the NCM ternary material, and the Ni content is reduced at the same time to prepare a single crystal material, which can reach the equivalent energy density of NCM811 , and improve the gas production, circulation and safety issues of high-nickel materials.
The addition of the fourth element (Al) can enhance the boundary strength between material grains and reduce the micro-gap that is harmful to the phase transition process, thereby improving cycle performance and safety performance. However, there are too many types of element doping, the preparation process is more complicated, and the consistency of material synthesis is difficult to guarantee.
A blade battery technology refers to a lithium battery that is slender and flat like a blade (such as a typical size of 13.5mm*90mm*960mm). It adopts lamination battery technology inside, and the length of a single pole piece can reach more than 900mm. When the battery pack is directly integrated into the bottom of the battery pack, the module structure is eliminated.
Compared with the traditional battery pack, the space utilization rate of the blade battery technology integration is increased by about 50%, that is to say, more blade batteries can be assembled under the same volume , thereby increasing the driving range of electric vehicles.
The core advantages of the blade battery technology:
The traditional battery pack adopts the assembly scheme of cell-module-battery pack, and the space utilization rate is about 40%. The blade battery technology adopts the assembly scheme of cell-battery pack, and the space utilization rate is about 60%. Due to the cancellation of the module and beam structure , the blade battery not only provides electrical energy as an energy body, but also acts as a structural member for fixing and supporting.
The blade batteries are arranged sideways and plugged in to form a battery cell array. The battery stack is extremely strong, and two high-strength plates are pasted on the upper and lower sides of the battery stack to upgrade the strength of the battery pack.
The lithium iron phosphate material with good thermal stability can pass the most stringent acupuncture safety test, and the battery surface temperature does not exceed 60°C.
Concerns about blade batteries:
Low temperature performance
Lithium iron phosphate material itself has poor low-temperature performance, and electric vehicles equipped with lithium iron phosphate batteries may lead to a rapid decrease in driving range in low temperature weather.
Since the blade battery technology is directly integrated into the bottom of the battery pack, when the battery is damaged and needs to be replaced, the entire battery pack needs to be removed, resulting in high maintenance costs.
4680 electrodeless battery
The 4680 electrodeless battery technology mainly includes battery technology of “4680” and “electrodeless ear”. 4680 represents a cylindrical battery with a diameter of 46mm and a height of 80mm. By increasing the size of a single cell, the proportion of inactive materials can be diluted, reducing fixed costs and BMS difficulty.
No tab refers to no tab, but no tab welded on the current collector in the traditional sense. The shape of the tab is directly cut on the current collector by laser, and then welded to the current collector. Lead the current to the shell to realize the connection of the external circuit.
In the manufacturing process of lithium batteries, the electrode preparation usually adopts a wet process, that is, the dry powder particles that make up the electrode formula are mixed and dispersed with a solvent to form a slurry, which is then coated on the current collector and baked to form an electrode.
The dry electrode does not use any solvent, but directly mixes the dry powder particles that make up the electrode formula at high speed, and the binder PTFE is fibrous through high-speed shearing, and then the mixed powder is hot-rolled to form a self-supporting film, and finally the the self-supporting film is pressed and bonded on the current collector under the action of heat to form an electrode.
Since the dry electrode preparation process does not use any solvent, it is a green process, which is energy-saving and environmentally friendly, and can reduce material costs.
It is also conducive to the preparation of thick electrodes for energy batteries, and its manufacturing process is especially suitable for the next generation of silicon-doped lithium supplementation and solid-state battery technology systems can be said to be a very promising pole piece preparation process.
However, the contact problem between the self-supporting film and the current collector and the contact problem between the dry powder particles will lead to an increase in the impedance of the electrode, and its magnification is relatively poor, and the dry electrode process is difficult, requiring the development of special equipment, which is currently difficult to large-scale application.
In fact, solid-state batteries are a relatively broad concept. Traditional lithium batteries use liquid electrolytes as the carrier for Li+ transmission, and the core of solid-state battery technology is the innovation of electrolytes.
According to the content of liquid components in the electrolyte, it is divided into semi-solid batteries (liquid content ≤ 10%), quasi-solid batteries (liquid content ≤ 5%), and all-solid batteries (liquid content 0%).
The development and application trend of solid-state batteries will be a In the step-by-step infiltration process, the final solid-state battery technology will completely use solid-state electrolyte, and the negative electrode needs to use lithium metal materials to give full play to the advantages of solid-state batteries. The theoretical energy density can reach 400~500Wh/kg or even higher.
The research on solid-state electrolytes mainly includes three categories: polymers, oxides, and sulfides.
The polymer solid electrolyte is composed of a polymer matrix (such as polyester, polymerase, polyamine, etc.) and lithium salts (LiClO4, LiFP6, etc.), Li+ is “dissolved” in the polymer matrix in the form of lithium salt, and the transmission rate is affected by the matrix. The higher the temperature, the higher the ionic conductivity of the polymer.
Oxide solid electrolytes include crystalline (perovskite-type LLTO, NASICON-type, garnet-type LLZO, LISICON-type) and amorphous (LiPON-type, etc.) material structures. The oxide crystalline solid electrolyte has good chemical stability and good cycle performance, but its room temperature conductivity is also low, and the contact between the electrolyte and the electrode particles is poor. The preparation process of LiPON electrolyte is complicated and the cost is high.
The ionic conductivity of sulfide solid electrolyte at room temperature is relatively high, which is close to or even exceeds that of organic electrolyte, and has good thermal stability and safety performance. However, sulfide is sensitive to air and is easy to oxidize. It is easy to produce harmful gases such as hydrogen sulfide when it meets water, and the electrochemical stability is poor.
To sum up, the advantages and disadvantages of solid-state batteries are very clear. It can greatly increase the energy density of the battery and better solve the problem of range anxiety in electric vehicles. Since the solid electrolyte is non-flammable, it has excellent safety and can operate at higher temperatures.
However, the solid-solid contact between the solid-state electrolyte and the electrode is small, the Li+ transmission efficiency is low, and the power performance is poor. In addition, the manufacturing cost of the solid-state battery technology is also high.
Graphene is a new material exfoliated from graphite and closely packed with carbon atoms connected by SP2 hybridization into a single-layer two-dimensional honeycomb lattice structure.
The highest material, used in lithium batteries can greatly reduce the internal resistance of the battery, improve the rate performance, and can improve the heat transfer of the electrode material, and improve the stability and safety performance of the battery.
However, due to the two-dimensional planar structure of graphene, it will produce a “steric hindrance effect”, which greatly hinders the migration of Li+, resulting in the deterioration of battery power performance. The steric hindrance effect of Li+ is negligible.
However, when the diameter of graphene sheets decreases, its excellent electrical and thermal conductivity will not be fully utilized, which greatly weakens the advantages of graphene.
At present, there are two main directions to integrate graphene into the battery technology industry, one is as a conductive additive, and the other is as the main material of the negative electrode.
If the power battery technology uses graphene as a conductive additive, although its cost can be reluctantly accepted, it will not improve the performance of the battery much. If it is used as the main material of the negative electrode, the cost of the battery will be very high, and no one is willing to pay for it.
Silicon doped lithium battery
“Silicon-doped lithium supplementation” is a supporting battery technology for high-energy lithium-ion batteries. With people’s pursuit of higher energy density of batteries, a new Si negative electrode material has been extensively studied.
Compared with conventional graphite negative electrodes, silicon’s The capacity is more than ten times that of graphite, which means that only 10%wt silicon material can be used to achieve the same capacity level of graphite, which can greatly reduce the weight of the battery technology.
However, when silicon and lithium are fully alloyed, their expansion is as high as 300%, which is about 30 times that of conventional graphite. Therefore, a larger area of SEI film will be formed on the surface of silicon during the first charging process of lithium batteries, resulting in more Multi-active lithium loss.
Because the expansion of silicon is too large, it is usually difficult to apply it to lithium batteries alone. Instead, it is mixed with graphite to form a hybrid negative electrode. Even if there is little silicon doped, it will cause a large deterioration in the first efficiency of the negative electrode, which is often not worth the candle.
Therefore, for The lithium-supplementing battery technology of silicon-doped negative electrodes emerged as the times require, which provides an additional lithium source for the electrochemical system to form an SEI film, thereby fully utilizing the high-capacity advantages of silicon materials.
Sodium ion battery
Sodium battery is a revolutionary battery technology for lithium-ion batteries. The main differences include replacing the positive electrode material with a sodium ion system, the negative electrode material with hard carbon or soft carbon, and the current collector copper foil with aluminum foil, but the work of sodium-ion batteries.
The principle is similar to that of lithium-ion batteries. It relies on Na+ intercalation and extraction between the positive and negative electrode materials to achieve charge transfer. It can also be called a “rocking chair battery technology”.
M3P battery technology is a new type of battery technology based on material innovation, but its exact material system is currently unclear. According to some public information, it is judged that the positive electrode material of M3P battery should be completely or partially used with the same olivine structure as lithium iron phosphate (LFP). Modified lithium iron manganese phosphate (LFMP).
The theoretical capacity of both LFMP and LFP is 170mAh/g, and the compacted density is 2.3~2.6g/cm3, but the discharge platform of LFMP (4.1V) is higher than that of LFP (3.4V), so theoretically, the energy density of LFMP is about 20% higher.
Due to the doping of Mn element to replace part of Fe, the synthesis process cost is slightly higher than that of LFP, but still much lower than that of ternary materials. Mn and Fe elements are abundant in reserves and cheap. Therefore, the M3P battery technology is a compromise technical solution between the iron-lithium battery technology and the ternary battery technology.