CR1225 battery

It is urgent to develop cutting-edge technologies for large-capacity CR1225 battery

Battery Hundred People's Forum - Battery Network, February 27 (Chen Yuluanshui live text and picture broadcast) Traditional lithium-ion battery systems use liquid electrolytes, which have problems such as easy leakage, easy corrosion, poor safety and low reliability. At the same time, it also greatly limits the development of lithium batteries to high energy density and cannot fully meet the safety requirements of large-scale industrial energy storage.

"All-solid-state lithium-ion batteries use solid electrolytes, which are non-flammable, non-corrosive, non-volatile and leak-proof, and have inherent safety and longer service life." Zhang Weixin, vice dean of the School of Chemistry and Chemical Engineering of Hefei University of Technology, said, "Reasonable planning and layout will help my country seize the opportunity of the rapid development of solid-state batteries, prompt traditional batteries, especially power battery companies to accelerate transformation, and achieve breakthroughs in the new energy vehicle industry."

"In recent years, news of lithium-ion battery combustion and explosion has emerged in an endless stream, and safety issues urgently need attention." Zhang Weixin believes that in order to fundamentally solve the safety problems of lithium batteries and improve their energy density, replacing all flammable and explosive organic electrolytes with solid electrolytes that are non-flammable and have good thermal stability is a very effective solution.

In addition, according to the technical goals set by Made in China 2025, the energy density of lithium batteries will reach 300W·h/kg in 2020, 400W·h/kg in 2025, and 500W·h/kg in 2030. Based on high-nickel ternary + silicon-carbon negative electrode materials, the energy density of lithium batteries in the existing system is difficult to break through 300W·h/kg.

Zhang Weixin said that electrolyte materials are the core of all-solid-state lithium-ion battery technology, and electrolyte materials largely determine the various performance parameters of solid-state lithium batteries, such as power density, cycle stability, safety performance, high and low temperature performance, and service life. Compared with traditional lithium-ion batteries, the most obvious change in all-solid-state lithium-ion batteries is that their electrolytes have changed from the original electrolyte to solid electrolytes, which greatly reduces the battery volume and improves the energy density.

In Zhang Weixin's view, in view of the development needs of high-safety and long-life lithium secondary batteries in the field of new chemical energy storage technology, it is urgent to develop large-capacity all-solid-state lithium battery cutting-edge technology.

At present, solid-state lithium batteries have attracted domestic and foreign energy manufacturers such as France's Bollore, the United States' Sakti3, Toyota, CATL, Qingtao, Guoxuan High-tech, Jiawei Shares, Ganfeng Lithium, and Beijing Weilan to make layouts due to their excellent energy density and safety.

Regarding the research progress of solid-state electrolytes, Zhang Weixin introduced that solid-state electrolytes can be divided into inorganic solid-state electrolytes, polymer solid-state electrolytes, and other solid-state electrolytes.

Polymer solid-state electrolytes are mainly divided into PEO (polyethylene oxide)-based systems, polycarbonate-based systems, polysiloxane-based systems, and polymer lithium single-ion conductor-based systems. Their advantages are good high-temperature performance and the first to achieve commercialization, but the operating temperature is high, requiring a special thermal management system, the cost is high, and there is a phosphate protective layer on the negative electrode surface (extremely high cost). The battery system energy density has no obvious advantage (~130W·h/kg), and the power density is low. The research direction is mainly to blend, copolymerize or cross-link PEO with other polymers, or add inorganic particles to form an organic-inorganic hybrid system to enhance core capabilities. The polymer solid-state battery developed by BatScap under Bollore of France has been put into commercial use with a specification of 30kW·h. At present, there are nearly 4,000 such Bluecars.

Inorganic solid electrolytes include oxide electrolytes and sulfide electrolytes.

Oxide electrolytes are mainly divided into crystalline (LISCON structure, NASICON structure, perovskite structure and garnet structure) and amorphous. Their advantages are good cycle performance, high chemical stability, and suitable for thin film flexible structures. The disadvantage is low room temperature conductivity. The research direction is mainly to improve conductivity by element replacement and heterovalent element doping.

Sulfide electrolytes are mainly divided into binary systems (Li2S and P2S5) and ternary systems (Li2S, P2S5 and MS2, M=Si, Ge, Sn). Their advantage is the highest conductivity, which is the main direction in the future, but the preparation and use environment requirements are harsh, and they are unstable to both metal lithium and oxide positive electrodes. The research direction is mainly to reduce the synthesis cost and introduce multi-element doping.

However, all-solid-state lithium-ion batteries are currently facing challenges, including low ion conductivity, large interface impedance, and high preparation costs.

After the electrolyte is changed from liquid to solid, the lithium battery system transforms from the solid-liquid interface of the electrode material-electrolyte to the solid-solid interface of the electrode material-solid electrolyte. There is no wettability between the solid and the solid, and the interface contact resistance seriously affects the transmission of ions, resulting in a sharp increase in the internal resistance of the all-solid-state lithium-ion battery, poor battery cycle performance, and poor rate performance.

Zhang Weixin said that the main solutions at present are: metal lithium protection, polymer electrolyte modification, and lithium alloys, powder lithium electrodes, and foam lithium electrodes.

Solid-state lithium battery positive electrode materials generally use composite electrodes, which include solid electrolytes and conductive agents in addition to electrode active substances, and play a role in transmitting ions and electrons in the electrode. The ion transmission of polymers is achieved through the segment movement of the amorphous region. In order to improve the activity of the segments, fillers are generally added or copolymerized with other polymer monomers to improve the ionic conductivity of the material.

Currently, negative electrode materials are mainly concentrated in three categories: metallic lithium negative electrode materials, carbon family negative electrode materials and oxide negative electrode materials. Among them, metallic lithium negative electrode materials have become one of the most important negative electrode materials for CR1225 battery due to their advantages of high capacity and low potential.

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