Breaking news! A major breakthrough in solid-state batteries has been achieved. A team from Tsinghua University has overcome a key challenge, and the research has been published in the international top journal "Nature".

Doubling the range of electric vehicles is no longer a dream! The latest research on solid-state batteries from Tsinghua University is out.

According to Che Dongxi on September 28th, recently, the team led by Professor Zhang Qiang from the Department of Chemical Engineering at Tsinghua University has made the latest progress in solid-state battery research. They jointly proposed a new strategy for designing a "fluorine-rich anionic solvation structure" and successfully developed a new type of fluorinated polyether electrolyte.

This material enables solid-state batteries to achieve a gravimetric energy density of up to 604 Wh/kg and a volumetric energy density of 1027 Wh/L, which are almost twice the energy density of today's most advanced commercial lithium-ion batteries.

Currently, this research has been published in the world's top journal Nature.

▲ This paper has been published in Nature

Based on its high energy density, this battery also performs well in terms of lifespan and safety. The battery can maintain a high capacity after more than 500 cycles and has successfully passed the nail penetration test in a fully charged state.

It can be said that this work provides a proven scientific roadmap for manufacturing practical, safe, and ultra-high energy density batteries, which is expected to accelerate the electrification transformation process in transportation and a wider range of fields.

01. Tsinghua University Adopts Innovative Approach to Solve Battery Instability

The research shows that the core innovation of this breakthrough lies in a new type of "in-situ constructed" fluorinated polyether-based polymer electrolyte (FPE-SPE).

By precisely regulating the "solvation structure" around lithium ions, the researchers have successfully solved the key interface instability problem that has long plagued high-capacity lithium-rich manganese-based oxide (LRMO) cathodes.

▲ Schematic diagram of the design of the fluorinated polyether-based polymer electrolyte

LRMO not only relies on the redox reactions of traditional transition metal cations (such as manganese, nickel, and cobalt) to store charge but also utilizes lattice oxygen anions for additional charge compensation.

Therefore, LRMO is an advanced cathode material with extremely high theoretical specific capacity, and its capacity can usually exceed 250 - 300 mAh/g.

However, such high energy output is a double-edged sword.

Using LRMO materials to contribute additional battery capacity also leads to battery instability.

This is because the oxidation of lattice oxygen in LRMO easily becomes irreversible, ultimately resulting in the formation and release of oxygen, causing problems such as structural degradation and voltage decay.

It can be said that this research from Tsinghua University has overcome this problem by stabilizing the anionic redox process itself to break this decay chain, especially by preventing the irreversible final step of oxygen generation.

The paper shows that the researchers used an in-situ polymerization technique, injecting a liquid monomer precursor solution into the battery and then initiating a polymerization reaction by heating to form a solid electrolyte directly on the electrode surface. This method has a key manufacturing advantage: it can form a seamless and tightly bonded interface between the electrolyte and the electrode, eliminating the common porosity and high interface impedance problems in traditional prefabricated solid electrolytes.

02. "Far Ahead" in Energy Density with Guaranteed Safety

After solving the battery's decay problem, battery capacity is the golden indicator for future mass production.

The battery design in this research is highly practical and cutting-edge, using a high-loading LRMO cathode (areal capacity > 8 mAh/cm²), a lean electrolyte design (electrolyte to capacity ratio of 1.2 g/Ah), and an anode-free structure (using copper foil as the anode current collector). These are all key technical elements for achieving high energy density.

The anode-free pouch battery made of this new material has achieved a gravimetric energy density of 604 Wh/kg and a volumetric energy density of 1027 Wh/L.

Its energy density is more than twice that of today's top commercial electric vehicle battery packs (about 255 Wh/kg) and is also highly competitive compared to the established goals of solid-state battery companies such as QuantumScape (800 Wh/L).

▲ Electrochemical and safety performance of PTF-PE-SPE

In battery tests, the battery using FPE-PE-SPE (the new material studied by Tsinghua University) showed excellent long-term stability, maintaining a capacity retention rate of 72.1% after 500 cycles at a 0.5C rate. In contrast, the battery using the traditional PE-SPE electrolyte only retained 80% of its capacity after 50 cycles.

▲ Comparison of thermal runaway temperatures between experimental products and liquid electrolytes (Data source: Tsinghua University)

In terms of safety, the physical form of this electrolyte combined with its unique chemical composition (fluorinated polymer and TMP plasticizer) gives the battery inherent flame-retardant properties.

Experiments show that the PTF-PE/LiTFSI film itself is self-extinguishing, while the final PTF-PE-SPE electrolyte film is completely non-combustible.

In the nail penetration test, the fully charged FPE-SPE pouch battery did not catch fire or explode after being pierced by a steel nail, showing excellent tolerance to internal short circuits.

03. Led by an Ace Professor from Tsinghua University, Deeply Engaged in Battery Material Chemistry

The expert behind this research is Professor Zhang Qiang, a tenured professor and doctoral supervisor at Tsinghua University.

He has won the National Science Fund for Distinguished Young Scholars, the Young Scientists Award of the Ministry of Education, the China Youth Science and Technology Award, the Beijing Youth May 4th Medal, the Newton Advanced Fellowship of the Royal Society, the Liu Bing Award of Tsinghua University, and the Tian Zhaowu Award at the International Electrochemical Conference. He was named a "Highly Cited Researcher" for four consecutive years from 2017 to 2020.

▲ Professor Zhang Qiang, a tenured professor and doctoral supervisor at Tsinghua University (Photo source: Tsinghua University)

In recent years, he has been committed to combining major national needs with basic research. Facing the major needs of energy storage and utilization, he focuses on researching the principles and key energy materials of lithium-sulfur batteries. He proposed the concepts of lithium bond chemistry and ionic solvent composite structure in lithium-sulfur batteries and developed a variety of high-performance energy materials such as composite lithium metal anodes and carbon-sulfur composite cathodes according to the needs of high-energy batteries. He also constructed lithium-sulfur pouch battery devices.

04. Conclusion: One Step Closer to Mass Production of Solid-State Batteries

The research results from Tsinghua University are a perfect combination of ingenious material design, in-depth mechanism understanding, and excellent experimental verification.

By actively designing a polymer electrolyte, the team has fundamentally solved the inherent instability of LRMO cathodes, opening up a new dimension for the performance of lithium batteries.

This research also provides a clear technological path, strongly refuting the view that lithium-ion technology has reached its performance ceiling and bringing solid-state batteries one step closer to mass production.

This article is from the WeChat official account "Che Dongxi". The author is Janson. It is reprinted with permission by 36Kr.