Solid-state batteries (including semi-solid, quasi-solidand all-solid), which is getting closer
Although the current domestic semi-solid-state battery as a breakthrough, and in the short term is expected to become the main route of domestic enterprises. And this will surely bring more opportunities for new materials.
1. Solid electrolyte
In solid-state batteries, the electrolyte replaces the separator by separating the positive and negative electrodes in the form of thin films. At present, there are four main categories, among which the upper limit of polymer properties is low, oxides are currently making rapid progress, sulfides have the greatest potential in the future, and chlorides are developing rapidly. In addition, composite solid-state electrolytes are expected to be an important means to solve the problems of large interface resistance and fragility between solid-state electrolytes and electrodes, which are currently research hotspots.
Oxide electrolytes [1].The mainstream material systems are: garnet type (LLZO) (such as Li7La3Zr2O12), perovskite (LLTO) (such as Li3X La2 3-X TiO3), and Nasicon type (such as Li1+X Alx Ti2-X (PO4)3), among which LLLZO has higher compatibility for lithium anode.
At present, the oxide electrolyte industry chain is basically mature, and the start-up companies are close to the mass production stage, including Weilan, Qingtao, Huineng, Ganfeng Lithium Battery, Tailan, etc., and material companies include Shanghai Xiba, Langu, Tianmu Pilot, etc., and Dangsheng Technology, Sanxiang New Materials, etc.
One of the more important elements in the series is zirconium. PassedZircon sand [2].Deal withZirconium silicate, zirconium chloride, zirconium dioxide and other zirconium materials [3].。In 2022, the global zirconium ore output will be about 1.4 million tons, more than 50% of which will be concentrated in the three overseas giants of ILUKA, Rio Tinto and Teno, and the main domestic zirconium manufacturers include Oriental Zirconium, Sanxiang New Materials, Sinocera New Materials, etc.
Sulfide electrolytes [4].The representative formula is thio-lisicon and li2sip2s12 system, the former chemical formula is li4 xa1 ybys4 (a=ge, si, etc., b= p, al, zn, etc.), although there are problems such as safety and high cost, but sulfide conductivity is the highest, both processing performance, the greatest potential, foreign Toyota, BMW, etc. are more fancy, domestic honeycomb energy, Zhongke Guneng and so on are also in the layout, very worthwhile.
The key materials involved are:Germanium [5].。China is the world's second largest germanium ore storage country and the world's largest germanium producer. At present, the United States, the United Kingdom and other overseas countries will include germanium as a strategic resource, and are more cautious about germanium mining. Domestic key enterprises include Yunnan germanium industry, Chihong zinc germanium, etc.
Another category of critical materials is:Lithium sulfide, lithium chloride and phosphorus pentasulfide [6 7 8].Among them, lithium sulfide accounts for the largest proportion, comparable to "lithium carbonate", and is used for the synthesis of sulfide solid electrolytes and cathode materials for high-energy-density lithium-sulfur batteries. Battery-grade lithium sulfide (99.)99%) is characterized by being expensive, and the smaller the particle size, the higher the purity, and the higher the purity. The foreign representatives are mainly Lorad Chemical, Yabao, AMG Lithium, etc., and the domestic representatives are the lithium mining duo Tianqi Lithium, Ganfeng Lithium, as well as Hubei Xinrunde, Hangzhou Kaiyada, etc.
Polymer electrolytes [, which is formed by the complexation of polar polymers and lithium salts. The former include polysiloxane (PS), polyacrylonitrile (PAN), polymethyl methacrylate (PMMA), polyethylene oxide (PEO), etcAt present, the main suitable material system in the commercial field is PEO, which is mainly ethylene oxide derivatives, which is prepared by heterogeneous catalytic ring-opening polymerization of ethylene oxide. Zhongke Shenlan Huize and other representative battery companies, Oak shares and Del shares have a layout in the PEO material end. Raw materialsEthylene oxide [13].The main production enterprises include Satellite Petrochemical, Sanjiang Chemical, Shanghai Petrochemical, Zhenhai Refining & Chemical, Maoming Petrochemical, Yangzi Petrochemical, Sino-Korea Petrochemical, etc.
Lithium salts mainly include lithium bis-trifluoromethanesulfonimide (litfsi), lithium bisfluorosulfonimide (lifsi) or ionic liquids, among which the commercial ones are mainlylitfsi【14】At present, there are not many companies in the world that can mass produce, such as Solvay and 3M abroad, and related products such as Ruitai New Materials, Shanghai Yuji Sai Fluorine, Jiangsu Guotai Chaowei, Shanghai Xin Fluorine Industry and so on. In addition, it is necessary to add to the polymer electrolyteInert fillers such as TiO2, Al2O3, ZRo2, and SiO2 [15].andPlasticizers [16].
Halide electrolytes [17].The chemical formula is Lia-M-Xb, where X = Br, Cl, F, M are transition metal elements, and there are three common categories: Lia-M-Cl6, Lia-M-Cl4 and Lia-M-Cl8, which are generally synthesized with high cost and the compatibility of lithium anode needs to be improved, which is a material with great potential for development in all-solid-state lithium-ion batteries.
Second, the negative electrode
In solid-state batteries, the anode will be upgraded from graphite to silicon-based anode, lithium-containing anode, and then to metal lithium anode. Among them,Graphite anode [18].There are many enterprises, such as Shanshan, Beiteri, Putailai, Zhongke Electric, Shangtai Technology, Xiangfenghua, etc.
And these faucets are also aiming for the next generation of materialsSilicon-based anodeAccording to incomplete statistics, there are currently more than 40 enterprises in the layout, and have attracted investment from Xiaopeng, Geely and other enterprises, such as Tesla 4680 and CATL Kirin batteries.
However, at present, the silicon-based anode still has the problems of volume expansion and instability of SEI film, and it still needs to be doped with graphitePorous silicon carbon [20].It is expected that porous silicon carbon will be the mainstream direction of silicon-based anode materials in the future. In addition to the above-mentioned anode faucets, there are also Lanxi Zhide, Xiangfenghua, Tianmu Pilot, Solide, etc., and foreign companies such as Group 14, Silanano, Amprius, etc.
Porous) silicon carbon anode development drivenPorous carbon materials [21].The development of representative enterprises such as Yuanli shares. Another important raw material is:Elemental silicon, nanosilicon particles [22, 23]., foreign companies include Teijin, DuPont, Canada Tekna, Germany Hc.Stark, etc., mostly use plasma evaporation condensation method, which has better quality. Domestic enterprises include Boqian New Materials, Zhongning Silicon Industry, Polyfluoride and so on. Further upstream isSilane [24].and other raw materials.
In addition, the first efficiency of silicon-based anode is low, and it must also be matched with pre-lithiation. Among them, the negative electrode lithium supplement method includes blended lithium (Lithium powder, lithium silicide powder, etc. [25].Exposure to lithium supplementation (lithium foil supplementation, etc.), etc., but the process is difficult, the cost is high, and the safety is low, so it has not been applied on a large scale. The cathode lithium supplementation method is mainly divided into lithium-rich compounds (li5feo4, li2nio2, etc. [26].), binary lithium compounds (Li2O, Li2O2, Li3N, Li2S, etc. [27].) and lithium complexes (Li2S CO, LIF CO, et al. [28].), adding lithium supplementation material in the cathode homogenization process is simple and low-cost.
Lithium metal anode [29].It is the choice of the anode of solid-state batteries in the future, which has obvious cost advantages and can greatly improve the energy density of lithium batteries. However, there are still problems such as dendritic crystal growth, which is still in the research stage.
Three, cathode
The positive electrode is the short board of the battery. Solid-state batteries will continue to be used in the short termTernary high-nickel system（li（niacobmnc）o2）, or further increase the voltage by means of monocrystallization, oxide coating, metal doping, etc., so as to improve the energy density of the batteryHigh-voltage high-nickel ternary, ultra-high nickel ternary（linixcoymn1-x-yo2，x≥0.9）Develop. The representative enterprises are Rongbai Technology, Dangsheng Technology, Xiamen Tungsten New Energy, Zhenhua New Materials, Changchang Lithium, etc., among which Weilai 150-degree batteries have Ronbay Technology's ultra-high nickel cathode materialsDangsheng Technology and Xiamen Tungsten New Energy also recently said that ultra-high nickel materials have been introduced to customers in batches.
Lithium-rich manganese-based (Li[LixniymnzCO1-X-Y-Z]O2), high-pressure spinel lithium nickel-manganese oxide [32, 33].etc. are new systems. Among them, the lithium-rich manganese group is a layered oxide composed of two components, Li2Mno3 and Limo2 (M=nickel-cobalt-manganese), which has the potential of high energy density of more than 250mAh g, and of course, there are also problems such as voltage degradation and life decay in cycling. Enterprises such as National Content Bai, Dangsheng, BASF Shanshan, and Ningxia Hanyao have layouts, and the industry is in its infancy.
Four, diaphragm
Semi-solid-state batteries still need to be used in the traditional senseDiaphragm [34]., and wet + diaphragm coating will be the main choice, which can greatly improve the thermal stability and puncture strength of the diaphragm, while not being too thick. The representative companies include Enjie, Sinoma Technology, Hebei Jinli, Xingyuan Materials, etc., as well as third-party Putailai.
The raw materials of the diaphragm base film are currently more classicPolypropylene polyethylene [35]., but in a state of dependence on imports. In addition, to:Polyimide, PTFE, aramid, polyester [36 37 38 39].Separators made of high-temperature resistant materials are also important research directions. Toray has previously reported on aramid separators.
At present, separator coating materials are divided into two categories: inorganic and organic, and the former is mainly divided intoBoehmite and alumina [40 41].It is the main coating material at present, among which Boemu stone has a larger market share, and the representative enterprises are Yishitong, Germany Nabaltec, Chinalco Zhengzhou Research Institute, Sinocera Materials, Jidun New Materials, etc.
Polytetrafluoroethylene (PVDF), polyester (PMMA), aramid [42 43 44].It is the representative of organic coating materials, the first two are currently the mainstream, but aramid is emerging and is replacing the trend in liquid lithium-ion batteries. Japan's Sumitomo in this area of the layout earlier, the domestic representative enterprise is Taihe new materials, the company in cooperation with and Enjie shares, Xingyuan materials, etc., of which Enjie shares recently said that ultra-high heat-resistant aramid coating film has been applied on 46 series large cylinders. At the same time, Taihe New Materials also recently said that the relevant verification of the company's aramid coated separator in the field of semi-solid-state batteries is underway.
Electrolyte composite membrane [45].This involves coating a PP or PE separator with an oxide solid electrolyte, or compounding the oxide with an organic solid electrolyte (i.e., the composite solid electrolyte described above). Xingyuan Materials recently said that the company's newly developed electrolyte composite film is suitable for solid-state and semi-solid-state battery systems, and has been used by customers such as Freyr Battery Norway As.
5. Other important materials
Other materials are similar to liquid lithium batteries. For example:Binders, conductive agents (slurries), dispersants, aluminum-plastic films, current collectors [46 47 48 49 50].Wait.
Traditional binders include polyvinylidene fluoride (PVDF), styrene-butadiene rubber (SBR) emulsions, and carboxymethyl cellulose (CMC), polyacrylic acid (PAA), polyacrylonitrile (PAN), and polyacrylates, among otherspvdf【51】It is mainstream, but it will change in solid-state batteries, such as with the development of silicon carbon anodespaa【52】Gradually, in additionhnbr【52】There are also some research projects to replace PVDF, such as Nippon Reon, and HNBR is expected to be used in solid-state electrolytes. In addition to this, there are many emerging structures that are being studied.
Conductive agents are still todayCarbon black [53].withCarbon nanotubes [54].With the development of solid-state batteries, the amount of carbon nanotubes will increase, especially single-walled carbon nanotubes.
Aluminum-plastic film [49].In terms of pouch cells, pouch batteries are more suitable for solid-state batteries due to their lamination process, higher energy density and more experienced gel packaging technology, which will drive the demand for aluminum-plastic films. There is still a lot of room for development, including the base film.
At present, the composite current collector and semi-solid-state battery technology will continue to use copper foil for the negative electrode and aluminum foil for the positive electrode, and the cost, performance and yield are still competing between the two. The upstream includes base film materials such as PET and PP, as well as raw materials such as additives and targets, among which the base film can be usedpet、pppi【55/56/57】Three materials. At present, the domestic high-end PET film market is mainly dominated by companies such as Toray, Mitsubishi, Toyobo, 3M and SKC.
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