As the most critical component of electric vehicles, power batteries will continue to be supported and encouraged by international policies from all walks of life. Industry enterprises and related units will also continue to invest large amounts of capital and resources to actively promote the rapid development of the industry. In general, the power battery industry has the following development trends.
(1) In terms of cathode materials. The positive electrode materials are mainly spinel lithium manganate materials, layered materials represented by nickel cobalt manganese and nickel cobalt aluminum, and olivine structural materials represented by lithium iron phosphate. Battery companies in other countries mainly focus on lithium manganese oxide, nickel cobalt manganese, nickel cobalt aluminum or their mixed materials; China currently uses lithium iron phosphate as the main material, but the room for further improvement of its specific energy is limited. With the substantial increase in the specific energy requirements of power batteries, the trend of conversion to nickel-cobalt-manganese, nickel-cobalt-aluminum or their mixed materials is obvious. As shown in Figure 1.
(2) In terms of negative electrode materials. Graphite materials are still the mainstream choice of anode materials (including artificial graphite, natural graphite and mesocarbon microspheres). With the significant increase in the specific energy requirements of power batteries, alloy materials, especially silicon-carbon composite materials, have become the key direction of industrialization and application at present and in the future; for fast charging power batteries, lithium titanate anode material is still the preferred material, and a mixed material of graphite and soft carbon can also meet the requirements, as shown in Figure 2.
(3) Diaphragm materials. Polyolefin materials are the mainstream choice of diaphragm materials, including two major categories of polypropylene and polyethylene products, mainly single-layer membranes and composite membranes. In order to improve the safety of the power battery, the surface of the diaphragm material has been surface modified, such as coating with inorganic ceramic coating (such as aluminum oxide or silicon dioxide, etc.) or organic coating (such as PVDF, etc.); at the same time, in view of the further improvement of the specific energy of power batteries, the thinning of diaphragm materials is a development trend, and polyethylene materials will be widely used. In addition, some new diaphragm materials, such as polyimide and non-woven fabrics, have also been applied and verified. From the perspective of improving specific energy and safety, surface modification on the basis of thin polyethylene materials and coating with organic or inorganic coatings (such as aluminum oxide or silica inorganic coating, PVDF organic coating, etc.) are the mainstream technology choices at present and in the future.
(4) In terms of electrolyte. Lithium hexafluorophosphate is still the mainstream product in the electrolyte market, and no alternative technologies and products will appear in the future, posing a serious threat to it. At the same time, some new types of lithium salts appeared on the market and got preliminary applications. For example, compared with the traditional lithium hexafluorophosphate electrolyte salt, lithium bisfluorosulfonimide (LiFSl) has higher solubility and conductivity in solvents, a wider operating temperature range and higher safety. However, due to its high price, poor high-temperature storage stability, and difficulty in controlling impurity content, it is currently mainly used as an auxiliary material additive in combination with lithium hexafluorophosphate.
Among them, the power battery product system that can be realized or has been realized in the short and medium term includes:
(Cathode material—negative electrode material—separator material—electrolyte salt—monomer energy density—possibility of realization)
Lithium iron phosphate—graphite—PP mainly, some of which use coating film—lithium hexafluorophosphate, functional additives—110~60W•h/kg—have been commercialized and continue to be used (EV, PHEV, energy storage, etc.)
Cathode material—negative electrode material—separator material—electrolyte salt—monomer energy density—possibility of realization
Nickel, cobalt and manganese (type 333 or 532)—graphite—mainly PE, some of which use coating film—lithium hexafluorophosphate, functional additives—160~200W•h/kg—large-capacity batteries realize small-batch applications, and small-capacity batteries (such as 18650) realize large-scale applications.
Lithium-rich layered lithium manganate—silicon-carbon—PE-based, thinning and coating modification—lithium hexafluorophosphate, functional additives—280-400W•h/kg—under development