current position:Home>Charging mobile phones once a week is no longer a dream: Stanford University's "salt" battery has boarded nature, with a power of six times that of lithium battery

Charging mobile phones once a week is no longer a dream: Stanford University's "salt" battery has boarded nature, with a power of six times that of lithium battery

2021-09-01 00:32:31 Heart of machine

sodium chloride , The end of battery technology is such a common substance ?

At present , Lithium ion battery (Lithium-ion batteries, LIB) It is widely used in various applications from electric vehicles to wearable devices .

Before the invention of the second generation lithium ion battery , Researchers at 20 century 70 The first generation of lithium was developed in the s - Thionyl chloride (lithium-thionyl chloride, Li-SOCl_2) The battery , It uses SOCl_2 As cathode electrolyte , Lithium metal (lithium metal) As an anode , Amorphous carbon (amorphous carbon) As a cathode . The battery is reduced to sulfur by lithium oxidation and cathode electrolyte 、 Sulfur dioxide and lithium chloride discharge , Known for its high energy density .

Picture source itdcw.

In a recent study , The Stanford team developed a rechargeable alkali metal - chlorine (alkali metal-chlorine) The battery , The stored power is the common rechargeable lithium ion on the market (lithium-ion) Battery 6 times .

The research related papers were published in 《Nature》, The joint work is a doctoral student in the Department of chemistry at Stanford University Guanzhou Zhu and Xin Tian, The corresponding author is Dai Hongjie, Professor of chemistry at Stanford University (Hongjie Dai).

According to introducing , This alkali metal - Chlorine batteries can accelerate the use of rechargeable batteries , And bring battery researchers closer to achieving the highest goal in this field : Develop a high-performance rechargeable battery , So that the mobile phone can be charged every week instead of every day , The battery car realizes the current electric vehicle when it is charged at one time 6 Times the driving distance .

Address of thesis :

From an implementation perspective , This alkali metal - Chlorine batteries rely on sodium chloride (sodium chloride, Na/Cl_2) Or lithium chloride (lithium chloride, Li/Cl_2) Repeated chemical conversion to chlorine .

An accidental discovery opportunity

So far, no one has developed high-performance rechargeable sodium - Chlorine or lithium - The reason for chlorine batteries is that chlorine is too reactive , It is difficult to efficiently convert back to chloride . In a few cases , Researchers can achieve rechargeability , But the result is that the performance of the battery is too poor .

in fact , Professor Dai Hongjie and Guanzhou Zhu The doctor had no intention of making rechargeable sodium and lithium at all - Chlorine battery , But only to use thionyl chloride to improve the existing battery technology . This chemical is one of the main components of lithium thionyl chloride batteries , Lithium thionyl chloride battery is 1970 A popular disposable battery first invented in the s .

But in one of their early experiments involving chlorine and sodium chloride , Researchers at Stanford University noticed that , The transformation of one chemical substance into another stabilizes in some way , This creates some rechargeability . Professor Dai Hongjie thinks this is impossible , It took them at least a year to realize the importance of this matter .

Over the next few years , The team clarified reversible chemical reactions , And through the test of different materials of battery cathode , Find ways to improve its efficiency . When they use a from National Chung Cheng University Yuan-Yao Li The professor and his students Hung-Chun Tai When the developed advanced porous carbon material forms an electrode , With the support of this technology, a major breakthrough has been made . Carbon materials have nanosphere structure , Filled with many ultra-fine pores . In practice , These hollow balls are like a sponge , Absorbed a large number of sensitive chlorine molecules , And store them , So that it can be converted into salt in micropores later .

When the battery is charged , Chlorine molecules are trapped in the pores of carbon nanospheres and protected ,Zhu explains . then , When the battery needs to be drained or discharged , We can discharge the battery and convert chlorine into NaCl—— The main ingredient of table salt —— This process can be repeated several times . At present, the maximum number of cycles can be 200 Time , But there is still room for improvement .

The result is a brass ring design for the battery —— High energy density has taken a step . up to now , Researchers have achieved Per gram of positive material 1200 mah , At present, the capacity of commercial lithium-ion batteries is... Per gram 200 mah . The battery capacity is at least half that of lithium-ion battery 6 times .

Stanford researchers did not mention voltage . Earlier, the sodium ion battery proposed by Ningde era , Its cell energy density is 160Wh/kg, The capacity of lithium iron phosphate battery commonly used in electric vehicles is 140Wh/kg about .

The researchers imagine that their batteries will one day be used in places that have not been used before , For example, satellites or remote sensors . Many available satellites are now floating in orbit , Unable to work due to battery depletion . future , If the satellite is equipped with a long-life rechargeable battery , Solar charger can be installed , Then the use of satellites will expand many times . For consumer electronics or electric vehicles , In designing the battery structure 、 Increase energy density 、 There is still a lot of work to be done to expand the battery scale and increase the number of cycles .

The mysterious veil of new battery technology

In this paper, the researchers demonstrated the high microporous carbon cathode of the battery , A starting electrolyte , Made from additives containing fluoride SOCl_2 Composition of aluminum chloride in , The negative electrode of the battery consists of sodium or lithium . This research can produce rechargeable Na/Cl_2 or Li/Cl_2 The battery , Mainly through... In carbon micropores Cl_2/Cl^- Redox and on sodium or lithium metals Na/Na^+ or Li/Li^+ Redox formation . Reversible in microporous carbon Cl_2/NaCl or Cl_2/LiCl Rechargeability is provided on the positive side by redox , Thin alkali metal - Fluoride doped alkali metals - Chloride solid electrolyte has stable interface , Both for secondary alkali metals / Cl_2 Batteries are crucial .

For sodium chloride used (Na/Cl_2) The battery , among Amorphous carbon nanospheres (amorphous carbon nanospheres, aCNS) As a cathode , SOCl_2 Aluminum chloride in (AlCl_3) As the main component of the starting electrolyte . The battery is working / The cyclic discharge voltage is 3.5 V, Capacity up to 1,200 mAh g−^1 Working in the case of / Loop over 200 Time , Coulomb efficiency (Coulombic efficiency) And energy efficiency (energy efficiency) Respectively 99% and 90% above .

The figure below 1 Amorphous nanospheres ( about 60nm,1a) And high performance sodium chloride at the first discharge (Na/Cl_2) The battery .

When the battery is recharged after the first discharge ,Na Deposited in Na On electrode ,NaCl Deposited in aCNS The electrode is oxidized ( about 3.83 V)( chart 2a) formation Cl_2, Exist in aCNS A large number of pores in the electrode ( Extended data table 1).

Here's the picture 3 Shown ,Na/Cl_2 The battery reaches the capacity of the first lower discharge platform (1,860 mAh g^-1) Cycle performance at .

The figure below 4 Show the Na/Cl_2 and Li/Cl_2 In the battery , The stability of the SEI For sodium anodes and aCNS The importance of the cathode .

Author's brief introduction

A joint paper Guanzhou Zhu He is a doctoral student in the Department of chemistry at Stanford University , Bachelor degree from UCLA . The research scope includes the development of high capacity and high energy density batteries 、 Synthesis of new electrodes and electrolytes for different battery systems , And using different characterization techniques to analyze the working and fault mechanism of the battery .

Corresponding author Dai Hongjie , Chinese American chemist and applied physicist , Professor of chemistry at Stanford University . He is a leader in nanotube . Graduated from Tsinghua University , He graduated from Columbia University with a master's degree in Applied Science , He graduated from the Department of Applied Physics at Harvard University . After that, he entered Stanford University and served as assistant professor and professor .

2009 He was elected academician of the American Academy of Arts and Sciences ,2011 He was elected a member of the American Association for the advancement of Science ,2016 He was elected academician of the National Academy of Sciences ,2020 year 9 Selected in 2020 year 「 Laureate Award for citation 」.

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