## New multiphase structure cathode exploits lithium deficiency for better performance

##### 28 June 2017

In the ongoing quest to develop high-capacity cathode materials for high-energy batteries, the conventional approach has been to rely on lithium-excess materials to operate the cathode at high voltage. This approach, however, has been dogged by numerous unresolved issues, such as voltage fading and structural failure.

Now, an international team from the US and S. Korea is proposing a different approach to high-capacity cathodes: lithium deficiency as opposed to lithium excess. In a paper published in the journal Advanced Sustainable Systems, they reported on their development of a multiphase structure (MPS) NMC cathode material that exploits the benefit of both spinel and layered structures. The prepared cathode material showed high structural, thermal and electrochemical stability with high cycle life and improved rate performance.

 Concept diagram of multiphase structure cathode materials: Li-deficiency resulted in the formation of an additional spinel phase (top, red) apart from the major layered phase (bottom). Cho et al. Click to enlarge.

To produce the MPS material, they used lithium deficiency in the solid state lithiation of the spray-dried metal hydroxide precursor. Based on a controlled sintering rate to avoid the oxidation of Ni2+, the rapid—and cost effective—lithiation of the precursor with the lithium deficiency acts as a driving force partially to convert the layered material to a spinel phase—yielding a multiphase structure (MPS) cathode material.

The shorter calcination time in the process can also reduce the overall electrical cost of the cathode material by 37%.

Spinel material in a Li-ion battery electrode generally offers better rate capability than a layered oxide material—but this benefit is offset by a lower capacity. This issue, as well as the spinel material’s capacity degradation at elevated temperature, is typically a drawback to the use of spinel material. The MPS addresses this, however.

We have synthesized a multiphase structure cathode material (MPS) where both the layered structure and the spinel structure is present. The structural stability of the defect-spinel structure (Fd-3m) NMC material is significantly outperforming because of the pillaring structure in lithium layer. As such, spinel NMC can sustain up to a very high voltage of 4.5 V and even higher than 4.5 V. Also, the spinel structure contains 3D channels for the Li-ion to transfer during lithiation/delithiation, which eventually improves the rate capability. Spinel NMC thus offers improved cycling stability as well as high rate capability. Yet, comparing to the layered structure, the spinel structure has less number of active sites for Li-ion since transition metal ions stay and act as pillars in the lithium layer. Hence, the specific capacity of Spinel NMC is lower than that of the layered NMC.

In this new concept, we have synthesized a multiphase structure cathode material to exploit the benefit of both the spinel and layered structure, i.e., to gain high structural stability with improved rate performance while keeping the capacity high enough, we have used similar manufacturing process as of current commercial production of NMC layered cathode materials.

—Cho et al.

 Electrochemical Performance of MPS and single-phase layered NMC (SPS). a) formation cycle voltage plot; b) rate capability (up to 8C); c) 1C/1C cycle data at room temperature; and d) at 60 °C. Cho et al. Click to enlarge.

After cycling, the MPS showed significantly reduced phase transition compared to a commercial single-phase layered NMC (SPS). Capacity retention after 250 cycles at room temperature was 75% for MPS, compared to 72% in SPS. MPS also showed high rate capability up to 8C, compared to SPS. At high temperature (60 °C) cycling of 50 cycles, MPS showed high capacity retention of 93.5% compared to 79.1% with SPS.

The researchers attributed the high performance of MPS to the multiphase structure which is structurally more stable at higher voltages.

A patent has been filed on the work (“Multi-phase structured cathode active material for lithium ion battery” (PCT Patent Filing Number/US2015/051426, 2015). The named inventor, Dr. Sung-Jin Cho, is the lead author of the paper, and is an Assistant Professor at North Carolina A&T State University—the applicant on the patent.

Resources

• S.-J. Cho, M.-J. Uddin, P. K. Alaboina, S. S. Han, M. I. Nandasiri, Y. S. Choi, E. Hu, K.-W. Nam, A. M. Schwarz, S. K. Nune, J. S. Cho, K. H. Oh, D. Choi (2017) “Exploring Lithium Deficiency in Layered Oxide Cathode for Li-Ion Battery” Adv. Sustainable Syst. 1700026 doi: /10.1002/adsu.201700026

O es que no me entero o no veo absolutamente ningún avance en este Catodo una retención del 80% después de 250 ciclos a 1C/1C y temperatura ambiente no lleva a ningún sitio, vamos tiene visos mas que nulos para ser comercializado....¿Donde esta la novedad?. Seguimos con estudios de todo tipo donde no conducen a ningún sitio. ¿Llegare algún dia a ver un celda revolucionaria que realmente lo cambie todo?. Cada día tengo menos esperanzas de llegar a verlo espero de todo corazón que generaciones futuras si puedan llegar a verlo.

Another article that prove that actual batteries are not good and there is still no better ones for a long time to come but im sure harvyd is still full of hope. I will never buy a pure ev but im considering a phev instead with a reasonable battery size like the volt or prius plug-in. Also there is the nissan e note and some recently improved hybrid like the 2018 camry le hybrid and ioniq blue.

HarvyD has reason to be full of hope. In spite of your contention that batteries are not improving industry analysts tell us that price performance improved 14% per year from 2010 thru 2014 and 16% per year from 2015 thru 2016. Think about it. In 2010 the only BEV available under 150% of the average new car price cost $30K, had 73 miles of range, a 5 year warranty on the battery, and if you had to pay extra to be able to re-charge at a rate of 50kW. When adjusted for inflation that configuration equates to$35K in 2017 dollars. Today you can an Ioniq with a 124 mile range for $29,500 and it charges at 100kW with a lifetime warranty on the battery. They doubled the charge rate and In constant dollar terms that is a more than double the range/$ and obviously more than doubling the warranty.

Moreover next month for 35K the Tesla M3 will give you triple the range of that 2010 Nissan Leaf and more than double the charge rate. Within 6 months of that Nissan will also triple the range AND triple the charge rate to 150kW. Within six months of that Hyundai will offer the Ioniq with 300+ miles of range and a 150kW charge rate.

gorr can prove it's impossible for a human being to dunk a basketball because he saw a 10 year old little boy who couldn't so now he knows that NOBODY can!

Seriously, gorr...I'm tired of being nice and ignoring your rants. STFU or learn some logic you frigging moron.

Looks like the usual suspect got deleted.

I said to commercialize the gas serial hybrid technology here with exhaust pressure and heat capture and recirculation. Is it clear now ? I knew perfectly since a long time that climate change proponents are leaftist economic scammers.

Is is a fact that rechargeable batteries are progressively improving at 5%/yr to 10%/yr while mass production and automation are reducing cost and improving lifetime.

There are no major technical reasons why small lighter BEVs could not compete with equivalent ICEVs by 2030 or so. Much improved batteries, lighter better designed units, mass produced in China and or in other countries with lower cost labour will produce those units by the millions at much lower cost. Even GORR will want to buy one.

Alternatively and/or concurrently, larger heavier FCEVs will compete against gasoline/diesel powered SUVs, Pick-ups, long range trucks and buses, locomotives and ships etc.

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