Research statement 3

November 2, 2015

(This article is based on what was posted from September 16 to October 31, 2015, for Linkedin)

Toru Hara, PhD

Electric vehicle battery

Introduction

Electric vehicles (EVs) seek lighter and cheaper batteries in order to become the next standard vehicles. Pure battery electric vehicles (BEVs) may have to wait for long; however, the time has come for hybrid electric vehicles (HEVs) including plug-in HEVs (PHEVs) to metamorphose from running billboards and/or status symbols to money machines and/or bargains. There are various types of vehicle batteries [1]; however, it is not likely that there is a big cost difference between them. Then, let me assume $500/kWh [2], 150 Wh/kg (cell level) or 130 Wh/kg [3] (module level), and 260 Wh/L [2] (cell level).

Cutting-edge high-capacity cathode materials, high-voltage cathode materials, and high-capacity anode materials are going to be employed. For example, Envia systems has achieved 250 Wh/kg for PHEVs (and 350 Wh/kg for BEVs, and 400 Wh/kg for drones) by using lithium-rich layered oxide, Li2MnO3-Li(Ni,Mn,Co)O2 (Li2MnO3-NMC) that can deliver up to 300 mAh/g [4]: let me assume $450/kWh (based on the assumption that it costs the same as any other co-precipitation processed materials) and < 700 Wh/L. The cost is expected to be further decreased down to $320/kWh [2]. High-capacity anode material, silicon (Si), is also going to be employed: assuming that > 1000 mAh/g is available, > 300 Wh/kg is highly possible. The volumetric energy density may not be changed since Si needs void space etc. in order to accommodate 300% volume change. The cost is also unclear. As such, let me expect < $320/kWh, > 250 Wh/kg [3], >and  700 Wh/L.

There is another high-capacity cathode material, sulfur (S). Sulfur cathode used to adopt lithium (Li) metal as the anode. SION POWER (US) has achieved 350 Wh/kg and 350 Wh/L with its Li/S battery [5]. Oxis (UK) has achieved 400 Wh/kg with its Li/S battery [6]. The volumetric energy density is unclear: it may be using a nano-sized conducting agent to improve the gravimetric capacity that can result in a lower volumetric energy density; however, it is going to further improve the performance with aid from Fraunhofer (they have knowledge and experience not only on S cathode but also on hard carbon and silicon anode), The Technical University of Dresden etc, and it seems around 400 Wh/L is possible. According to the announcement, it can cost $250/kWh. Let me expect $250 kWh, 400 Wh/kg, and 400 Wh/L. Further increasing the volumetric energy density remains as a challenging issue. Because of the insulating nature of sulfur and polysulfides dissolution into electrolyte solutions, sulfur is usually encapsulated into porous carbon, conducting polymer, etc. Thus, increasing sulfur/encapsulating agents ratio in order for increasing volumetric energy density results in a lower rate capability and capacity fade. This can be a futile cat-and-mouse chase. There are some other counter measures such as S-stabilization by inverse vulcanization [7] (the matrix is electronically insulating), S-stabilization with pyrolyzed polyacrylonitrile that forms a cheaper analog to

graphene [8], S-stabilization with Ti2SC [9] etc.; however, polysulfides still dissolve into the solutions. Li anode has a problem, dendrite formation resulting in a short circuit failure. As described earlier, S cathode also has a problem, its reduced form, polysulfides, dissolve into electrolyte solutions resulting in reaching the anode surface (shuttle effect) and depositing insulating spieces and capacity fade in the end. PolyPlus (USA) [10] and Ceramatec (USA) [11] have non-porous ceramic-based separator technologies that suppress the dendrite formation and that inhibit the shuttle effect. Ceramatec has announced that it can cost $125/kWh that completely meets U.S. Department of Energy (DOE) goal [12]. One may expect $125 kWh, 400 Wh/kg, and 400 Wh/L. Battery users may still not want to use Li anode. It is unlikely that all of loaded Li is going to be fully utilized (dissolved into electrolyte solutions) particularly when conventional flat current collectors such as Cu foil and Li foil or Li film are used. When using conventional anode materials such as graphite, anode/cathode capacity ratio is usually set at 1.1: this still is totally unacceptable for Li foil since 1000% volume change is totally unacceptable. Thus, Li mass-loading has to become a large excess amount, or another technology will be required: for instance, polysulfide (Li2S8)-induced solid electrolyte interphase (SEI) @ Li (deposited during lithiation)@three-dimensional graphene framework/S battery [13]. GS Yuasa (Japan) has announced that they have developed Si/S battery [14,15]. Since both Si and S do not have lithium, either Si or S must be pre-doped with Li. Li pre-dope is usually carried out by directly short-circuiting Li foil and the anode in an electrolyte solution. GS Yuasa has a unique Li pre-dope option [16]: soaking the anode into a solution, which is prepared by dissolving 0.25 mol/L naphthalene and metallic lithium into butyl methyl ether (BME) solvent, for 72 h.  This kind of method is often used for organic synthesis. After the pre-dope, assembly must be carried out in an inert atmosphere. The process automation/optimization becomes quite important. Currently commercially available lithium-ion capacitors have employed Li pre-dope process. Li pre-dope can be effective even for conventional lithium-ion batteries since nano-structured anode materials consume a lot of lithium salts when forming solid-electrolyte interphase (SEI) layer, or more concentrated electrolyte solutions should be prepared beforehand. In order to suppress shuttle effect thereby improve the cycle-life, Si anode may need another countermeasure instead of further efforts for S encapsulating cathode or instead of non-porous ceramic-based separator that is used for Li/S by PolyPlus and Ceramatec. Something ductile, such as polymer, is preferable. Note that the battery must work at least up to 1825 - 3650 cycles when assuming 5 - 10 years service life and 1 cycle per day. Fraunhofer has announced 1400 cycles. U. S. Advanced Battery Consortium (USABC) has set a 15-year life target for energy storage system; however, the target life for vehicle has been set a different value. Let me say, $220/kWh, 315 Wh/kg, and 300 Wh/L. It is not for GS Yuasa's Si/S battery: they can probably offer a comparable price and a specification with Oxis ($250 kWh, 400 Wh/kg, and 400 Wh/L). I am using so-called low S mass-loading cathode [8] for simulation. The anode is a cutting-edge Si/SiOx [17]. The merit is, the cathode is LiPF6/carbonate-compatible. There is a relatively new report on this cathode material [18]. The problem is, since sulfur delivers about 1200 mAh/g [cf. Li(Ni0.8Co0.15Al0.05)O2, NCA, and Li(Ni0.5Mn0.3Co0.2)O2, NMC532, 200 mAh/g], Si mass-loading must be increased, not like 1 mg/cm2 [18], then, the volume change accommodation becomes more difficult, or the energy density becomes lower when decreasing the cathode mass-loading and thickness. After solving this anode-side problem, the life-cycle cost will be much better than any other Si/S batteries since the cathode-side durability is relatively good. My first plan (in 2013) was S-conducting polymer (polyaniline, PANI, is less bulky than polypyrrole, PPY) composite encapsulated in polymer-based microcapsule. It is not LiPF6/carbonate compatible and

polysulfides entrapment is not perfect. Carbon coating [19] may be practically difficult since sulfur is volatile.

Car manufacturers may still prefer the combination of Si and NCA or NMC that can somewhat decrease the weight and the volume since currently commercially available batteries for HEVs weigh, e.g., only 182 kg (> 45 L?) (carbon/Li1+xMn2-xO4 type, 240 V, 67 Ah, 16 kWh, LG Chem, for Chevrolet Volt) [20]. The above-mentioned Si/S can be > 51 kg and > 53 L.

Suggestion 1: High-voltage and high-capacity cathode

Lithium-rich Li(Ni,Co,Al)O2 (NCA) with minor titanium doping

Currently, lithium-rich layered manganese oxide is considered a promising candidate for the next generation lithium-ion battery cathode material although the lower actual usable capacity than the theoretical value (or oxygen evolution risk by adopting charging up to a high voltage in order to obtain a high capacity) in addition to a poor cycle life are the pain in the neck.

Since Numata et al. first reported in 1997 on LiMn2O3-LiCoO2 [21], lithium-rich layered transition metal oxide has been attracted attention. Kalyani et al. first reported in 1999 on electrochemical activation of over-lithiated Li2MnO3 by charging it up to 4.5 V [22]: this result accelerated the lithium-rich chemistry research. Lu and Dahn first suggested in 2002 [23] about Li2MnO3-Li(Ni,Co,Mn)O2. It may be noteworthy that Wagemaker et al. have reported in 2002 on a spontaneous phase separation of lithiated TiO2 into lithium-poor (Li0.01TiO2) and lithium-rich (Li0.6TiO2) domains on a scale of several tens of nanometers, and on a continuous flux of lithium ions across the phase boundaries [24]: this may suggest the importance of two-domain rather than solid-solution. Wu et al. have recently (2015) suggested that the surface lithium-rich layer formation can activate its high capacity and improve cycle life [25]. Note that even ball-milled composite [26] or Li2MnO3-NMC core-shell structure [27] delivers a high capacity, > 200 mAh/g. Xiao et al. have reported that titanium substitution for manganese is effective to suppress oxygen loss [28].

Li(Ni0.80Co0.15Al0.05)O2 (NCA) is another candidate for a high-capacity cathode material. By combining it with lithium-rich chemistry and titanium doping, a high-voltage and high-capacity cathode will be possible. Furthermore, its less-manganese nature may contribute to a better cycle-life performance.

Polymer coating on high-voltage cathode materials

In order to suppress catalytic oxidation of electrolyte, so-called high-voltage tolerant electrolytes such as fluorinated ethylene carbonate (F-EC), F2HC-CF2-CH2-O-CF2-CF2H etc. or fluorinated additives such as Al(OCH(CF3)2)3 have been researched. The solvophobic nature and relatively fast solid-electrolyte interphase (SEI) layer formation are the merit of fluorinated chemicals. In addition, polymer coating on high-voltage cathode materials may be another choice in order to decrease the cost (fulorinated chemicals are quite expensive).

In addition to Li2MnO3-NMC and Li2MnO3-NCA, there may be other choices such as partial spinel structure introduction: for instance, Sheargold and Andersen have patented lithium-rich spinel in 1999 [29]. Earlier and contemporary works can be seen in refs. [30-35] etc. Recently, Wang et al. successfully controlled a spinel Li4Mn5O12 component introduction into the lithium-rich layered material [36]: a discharge capacity of 290 mAh/g at 0.1 C, 145 mAh/g at 5 C, and 123 mAh/g at 10 C in addition to an improved cycle life have been reported. The oxygen evolution that starts from around 4.3 V still remains as a serious problem. The high-voltage phospho-olivines such as LiCoPO4 (4.8 V) or a modest/humble LiMnPO4 (4.0 V) or a solid-solution Li(Fe,Mn,Co)O4 can be another choice although only 150 mAh/g is practically available (theoretically around 170 mAh/g). Note that rate capability of olivine is usually much superior to earlier-mentioned lithium-rich layered manganese oxide. The average discharge voltage of lithium-rich layered transition-metal oxide is around 3.5 V that is not high even compared with conventional LiCoO2. The high-voltage cathode materials such as LiNi0.5Mn1.5O4

(LNMO) (4.5 V, 147 mAh/g) have more positive potentials but have some problems: LNMO delivers a much less capacity than lithium-rich layered transition-metal oxide.

Although lithium-rich NCA is the first choice, polymer coating can contribute to any other high-voltage and high-capacity materials.

Suggestion 2: sulfur-compatible Si anode

In order to realize a long service life of Si/S battery, the surface of silicon should be coated with polysulfides-repellent. Any types of sulfur cathodes and silicon anodes [37-39] are fine.

Polysulfides dissolution into electrolyte solutions, reaching the anode surface, resulting in insulating deposit formation and deactivation of the anode, is the cause of capacity fade. In order to further improve the service life, following strategy may be effective: (1) to further stabilize sulfur and suppress polysulfides dissolution, (2) to increase anode surface area with a minimum sacrifice of the total volumetric energy density and without sacrificing current collecting function, and (3) to form Li2S deposition suppressor, which must be lithium-ion-permeable but non-permeable against polysulfides, onto the anode surface. It should be anionic. Regarding (1), there are many counter measures such as inverse vulcanization [40] (I know one company of Japan that its technology has much longer history, though.), nano-structured carbon use such as mesoporous carbon, graphene, cheaper analog to graphene such as pyrolized polyacrylonitrile [8], Ti2SC [41] etc.; however, polysulfides still dissolve into the solutions. Regarding (2) and (3), I already introduced one concept that is based on Prieto Battery's three-dimensional architecture [42], in April, 2014. Materials choice is still at the stage of conceptualistic preliminary trial, though. Mosby&Prieto three-dimensional architecture needs anode electrodeposition onto three-dimensional current collector (Prieto Battery electrodeposits Cu2Sb onto Cu foam) and separator (or can be just a protective layer for the anode) electropolymerization onto the anode. Si anode is, probably, the best choice for conventional slurry-based manufacturing; however, Si electrodeposition by using SiCl4 etc. has a risk. Tin (Sn) or its intermetallic can be relatively easily electrodeposited. Sn-intermetallic with inactive metal has two merits: the inactive component contributes to current collecting function and mitigates mechanical stress resulting from Sn volume change; however, it increases the electrode mass without delivering an

electrochemical capacity. The alloying/dealloying chemistry of Sn is very slow; however, it can be compensated by increasing surface area. Conversion materials can also be electrodeposited; however, their much less negative potentials than graphite, Si, and Sn are not appropriate as the counterpart for any types of sulfur-based cathodes (around 2 V vs. Li+/Li). Conversion materials may be used in the future after the use of high-voltage cathode materials becomes possible, but not for sulfur. As the three-dimensional current collector, graphitized carbon fiber paper can be at least partially disintegrated after continuing charge/discharge (lithium deintercalation/intercalation from/into the graphitized carbon). If the high cost is acceptable, graphene or carbon nanotube can be used for current collecting function without disintegration since those materials are lithium-ion adsorption/desorption system: these nano-structured carbon may not even need Sn deposition but can depend on a required areal capacity. Matsunaga et al. [43] electrodeposited Sn onto Cu/carbon nanotube composite plating film. Metal foam is a less expensive choice; however, its specific surface area is much less greater than carbon fiber paper and nano-sized carbon materials.

References

[1] L. Lu, X. Han, J. Li, J. Hua, M. Ouyang, J. Power Sources 226 (2013) 272-288.

- Nissan Leaf EV (Automotive Energy Supply Corporation, AESC- Nissan & NEC): C (graphite and/or hard carbon) / LiMn2O4 (LMO),

- Chevrolet Volt (Compact Power - LG Chem): C/LMO,

- Renault Fluence (Automotive Energy Supply): C/LMO,

- Tesla Loadster (?): C/NCA,

- Tesla Model S (Panasonic Energy): C/NCA,

- BYD E6 (BYD): C/LiFePO4 (LFP),

- Subaru G4e (Subaru): C/Li3V2(PO4)3 (LVP),

- Honda Fit EV (Toshiba): Li4Ti5O12 (LTO)/Li(Ni,Co,Mn)O2 (NCM).

(cf.) LMO is quite cheap since it is synthesized via solid-phase reaction.

[2] D. L. Wood III, J. Li, C. Daniel, J. Power Sources 275 (2015) 234-242.

Assuming graphite/NMC, 150 Wh/kg, 260 Wh/L, and $502.8/kWh have been estimated. The cost can be expected to be decreased down to $370.3/kWh by (i) eliminating N-methylpyrrolidone (NMP) not only from anode manufacturing process as has already been carried out in Japan and Korea but also from cathode manufacturing process that contributes to

USD38.3/kWh of cost reduction, (ii) doubling electrode thickness from about 50 um (NMC cathode, 10.33 mg/cm2, and 1.39 mAh/cm2; graphite anode, 5.24 mg/cm2 and 1.53 mAh/cm2.) to 100 um for a single-sided coating that contributes to $39.3/kWh of cost reduction, and (iii) reducing anode electrolyte wetting and SEI formation that contributes to $54.9/kWh, totaling $132.5/kWh of cost reduction. According to their current cost breakdown, anode costs 8.1%, separator 26.0%, and cathode 32.7%.

As for sulfur, since the potential of sulfur is much less positive than conventional cathode materials, CMC and/or SBR can be used without an effort; therefore, (i) eliminating NMP is not difficult. Increasing electrode thickness and thereby increasing mass-loading while decreasing electrode preparation procedure (ii) is not difficult for sulfur because of a lot of conducting agent. Regarding (iii) reducing anode electrolyte wetting and SEI formation period, I already introduced anode pre-lithiation (pre-lithiation of carbon-based electrode has been already carried out in a manufacturing scale at least in Japan).

[3] http://www.eco-aesc-lb.com/en/product/liion_ev/

[4] http://www.enviasystems.com/

[5] http://www.sionpower.com/technology.html

[6] http://www.oxisenergy.com/

[7] A. G. Simmonds, J. J. Griebel, J. Park, K. R. Kim, W. J. Chung,V. P. Oleshko, J. Kim, E. T. Kim, R. S. Glass, C. L. Soles, Y. E. Sung, K. Char, J. Pyun, ACS Macro Lett. 3 (2014) 229-232.

[8] J. Wang, J. Yang, J. Xie, N. Xu, Adv. Mater. 14 (2002) 963-965.

[9] M. Q. Zhao, M. Sedran, Z. Ling, M. R. Lukatskaya, O. Mashtalir, M. Ghidiu, B. Dyatkin, D. J. Tallman, T. Djenizian, M. W. Barsoum, Y. Gogotsi, Angew. Chem. Int. Edit. 54 (2015) 4810-4814.

[10] http://www.polyplus.com/

[11] http://www.ceramatec.com/

[12] D. Howell, Fiscal year 2013 Annual Progress Report for Energy Storage R&D, U.S. Department of Energy (DOE), Office of Energy Efficiency and Renewable Energy, Vehicle Technologies Office, 2013, p. 2.

[13] X. B. Cheng, H. J. Peng, J. Q. Huang, R. Zhang, C. Z. Zhao, Q. Zhang, ACS Nano 9 (2015) 6373–6382.

[14] http://www.japantimes.co.jp/news/2014/11/17/business/corporate-business/gs-yuasa-triples-capacity-of-lithium-ion-battery/#.Vi0yCTahc2w

[15] http://www.gs-yuasa.com/us/topics/pdf/20141117e.pdf

[16] https://www.gs-yuasa.com/jp/technic/gsnews/no62_2/pdf/062_2_03.pdf

[17] S. K. Lee, S. M. Oh, E. Park, B. Scrosati, J. Hassoun, M. S. Park, Y. J. Kim, H. Kim, I. Belharouak, Y. K. Sun, Nano Lett. 15 (2015) 2863−2868.

[18] S. Wei, L. Ma, K. E. Hendrickson, Z. Tu, L. A. Archer, J. Am. Chem. Soc. 137 (2015) 12143-12152.

[19] S. Zhang, N. Li, H. Lu, J. Zheng, R. Zang, J. Cao, RSC Adv. 5 (2015) 50983-50988.

[20] https://media.gm.com/content/dam/Media/microsites/product/volt/docs/battery_101.pdf

[21] K. Numata, C. Sakaki, S. Yamanaka, Chem. Lett. 26 (1997) 725-726.

[22] P. Kalyani, S. Chitra, T. Mohan, S. Gopukumar, J. Power Sources 80 (1999)103-106.

[23] Z. H. Lu, J. R. Dahn, J. Electrochem. Soc. 149 (2002) A815-A822.

[24] M. Wagemaker, A. P. M. Kentgens, F. M. Mulder, Nature 418 (2002) 397-399.

[25] Z. Wu, S. Ji, J. Zheng, Z. Hu, S. Xiao, Y. Wei, Z. Zhuo, Y. Lin, W. Yang, K. Xu, K. Amine, F. Pan, Nano Lett. 15 (2015) 5590–5596.

[26] W. C. West, J. Soler, B. V. Ratnakumar, J. Power Sources 204 (2012) 200-204.

[27] J. K. Noh, S. Kim, H. Kim, W. Choi, W. Chang, D. Byun, B. W. Cho, K. Y. Chung, Scientific Report 4 (2014) 4847.

[28] P. Xiao, Z. Q. Deng, A. Manthiram, G. Henkelman, J. Phys. Chem. C 116 (2012) 23201−23204.

[29] W. S. Sheargold, T. N. Andersen (Kerr-McGee Chemical LLC), US005 87405 8A, 1999.

[30] W. I. F. David, M. M. Thackeray, L. A. De Picciotto, J. B. Goodenough, J. Solid State Chem. 67 (1987) 316–323.

[31] A. Yamada, J. Solid State Chem. 122 (1996) 160-165.

[32] Y. Xia, M. Yoshio, J. Electrochem. Soc. 144 (1997) 4186-4194.

[33] X. Q. Yang, X. Sun, S. J. Lee, J. McBreen, S. Mukerjee, M. L. Daroux, X. K. Xing, Electrochem. Solid-State Lett. 2 (1999) A87-A90.

[34] Y. Xia, T. Sakai, T. Fujieda, X. Q. Yang, X. Sun, Z. F. Ma, J. McBreen, M. Yoshio, J. Electrochem. Soc. 148 (2001) A723-A729.

[35] X. Yang, W. Tang, Z. Liu, Y. Makita, K. Ooi, J. Mater. Chem. 12 (2002) 12 489-495.

[36] D. Wang, R. Yu, X. Wang, L. Ge, X. Yang, Scientific Reports 5 (2015) 8403.

[37] http://www.enevate.com/

[38] http://www.nexeon.co.uk/

[39] http://www.amprius.com/

[40] A. G. Simmonds, J. J. Griebel, J. Park, K. R. Kim, W. J. Chung, V. P. Oleshko, J. Kim, E. T. Kim, R. S. Glass, C. L. Soles, Y. E. Sung, K. Char, J. Pyun, ACS Macro Lett. 3 (2014) 229-232.

[41] M. Q. Zhao, M. Sedran, Z. Ling, M. R. Lukatskaya, O. Mashtalir, M. Ghidiu, B. Dyatkin, D. J. Tallman, T. Djenizian, M. W. Barsoum, Y. Gogotsi, Angew. Chem. Int. Edit. 54 (2015) 4810-4814.

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[43] K. Matsunaga, S. Arai, 2015, 228th Electrochemical Society Meeting, Phoenix, USA.

Appendices

Passenger cars sales total (unit: vehicles)

World Wide Car Sales in 2014 (Q1-Q4)

China, 18,368,900; USA, 16,435,300; Europe, 13,006,500; Japan, 4,699,600 ...

World Wide Car Sales in 2015 (Q1-Q3) 

China, 13,702,400; USA, 12,995,900; Europe, 10,776,700; Japan, 3,278,800 ...

Electrified cars sales statistic (unit: vehicles)

Global EV Stock

Global, 665,000+ (represents 0.08% of total passenger cars)

Plug-In Electric Vehicle Sales in 2015 (Q1-Q3)

Global, 284,174 (Jan-Aug)

USA, 82,404 (Jan-Sep)

Top EV Battery Manufacturers (Sales Report) (2014 Q1-Q2 Share)

http://evobsession.com/top-ev-battery-manufacturers-sales-report/

Panasonic 36.4% (39.5% in 2013)

Nissan & NEC 24.1% (30% in 2013)

LG Chem 15.5% (18.9% in 2013)

Mitsubishi & GS Yuasa 7.0% (6.9% in 2013)

BYD 5.8% (2.7% in 2013)

(cf. 3) I have no information on Mitsubishi & GS Yuasa's battery. They have silicon/sulfur (Si/S) battery.

Top 10 EV Battery Manufacturers In Q1 2015

http://evobsession.com/ev-battery-manufacturer-sales-market-share-march-2015/

(2015 Q1 Share)

Panasonic 45% (41% in 2014)

Nissan & NEC 18% (24% in 2014)

BYD 10% (7% in 2014)

Mitsubishi & GS Yuasa 7% (7% in 2014)

LG Chem 6% (13% in 2013)

Typical battery-back specification

Nissan Leaf   (AESC) : 360 V, 67 Ah, 24 kWh, 183 kg.

Chevrolet Volt (LG Chem): 240 V, 67 Ah, 16 kWh, 182 kg.

Tesla Model S (Panasonic): 402 V, 212 Ah, 85 kWh, 544 kg.

BYD e6 (BYD): 60 kW (-> 82 kWh in 2016).

Honda Fit EV (Toshiba): 240 V, 84 Ah, 20 kWh.

Toyota Prius (Panasonic): 240 V, 19 Ah, 4.4 kWh.

Mitsubishi Outlander PHEV   (GS Yuasa) : 300 V, 40 Ah, 12 kWh.

Mitsubishi i MiEV [Lithium Energy Japan - GS Yuasa, Mitsubishi Corporation (MC), and Mitsubishi Motors Corporation (MMC)]: 330 V, 50 Ah, 16 kWh.

Industry trends

Japan electronic giants embrace autos after consumer-goods struggles

April 13, 2015 - 12:01 am ET

The Japanese consumer electronics giant is targeting a new market, Hirai announced -- the mammoth auto industry.

"This growing automotive segment has enormous potential," Hirai told the crowd in January at the International CES in Las Vegas. "We're aiming to take a leading position." ...

Panasonic President Kazuhiro Tsuga aims for automotive sales to account for 20 percent of the company's global revenue in four years. ...

Current technologies for consumer electronics applications

Cathode

(1) LiCoO2 (LCO)

Current standard. 4.2 - 3.0 V, 140 mAh/g. Solid phase synthesis = cheap process.

(2) NCA

Gradually replacing LCO. 4.3  - 3.0 V, 200 mAh/g. Co-precipitation = more costly than solid phase synthesis.

(3) NCM (when Mn is not activated, they call so)

Gradually replacing LCO. 4.3 - 3.0 V, 155 mAh/g. Co-precipitation = more costly than solid phase synthesis.

Anode

(1) Graphite

Current standard. 372 mAh/g.

(2) Hard carbon etc.

 500 - 1000 mA/g. Its volumetric energy density is smaller than graphite.

(3) Si or SiOx

 1000 or 2000 mAh/g. Lithiation potentials are 0.05 and 0.21 V, delithiation potentials are 0.31 and 0.47 V [1-8]. If one accepts the use of only about 50% of its theoretical capacity in order for a longer service life, one should set the full-cell voltage range within 4.1 - 2.5 V.

(4) Sn

 500 mAh/g. Lithiation potentials are 0.4, 0.57, and 0.69 V, delithiation potentials are 0.58, 0.7, and 0.78 V [1,8,9-11]. If one accepts the use of only about 50% of its theoretical capacity in order for a longer service life, one should set the full-cell voltage range within 3.7 - 2.2 V. One company is trying to sell Sn alloy anode: this less negative potential may be the border line; further less negative potentials may not have a chance except when combined with high-voltage cathode materials.  

(5) Conversion materials

They may be able to become alternatives for Li4Ti5O12 for automotive market etc.

Electrolyte

LiPF6/cyclic carbonate, chain carbonate(s)

Recent Progress in high-voltage lithium ion batteries [M. Hu, X. Pang, Z. Zhou, J. Power Sources 237 (2013) 229-242.]

The water-soluble binder carboxymethyl cellulose (CMC) has been considered a promising replacement for poly(vinylidenefluorite) (PVDF) [J. Li, R. Klopsch, S. Nowak, M. Kunze, M. Winter, S. Passerini, J. Power Sources 196 (2011) 7687-7691; J. Xu, S. L. Chou, Q. F. Gu, H. K. Liu, S. X. Dou, J. Power Sources 225 (2013) 172-178.].

SiO2-containing quartz separator significantly improved the capacity retention of LiCoPO4 as an HF scavenger [R. Sharabi, E. Markevich, V. Borgel, G. Salitra, D. Aurbach, G. Semrau, M. A. Schmidt, N. Schall, C. Stinner, Electrochem. Commun. 13 (2011) 800-802.].

Automotive Lithium-Ion Batteries: State of the art and future developments in lithium-ion battery packs for passenger car applications [P. Miller, Johnson Matthey Technol. Rev. 59 (2015) 4.]

http://www.technology.matthey.com/article/59/1/4-13/

According to the article, PHEV needs 300 - 600 V, 60 kW, and 4 - 10 kWh, EV needs 300 - 600 V, 60 kWh, and 15 kWh or more.

There is a comparative study on the performance and the cost of LiCoO2 (LCO), LFP, NMC, LMO, and LTO (Table II).  It says LCO costs about $31 - 46/kWh, LFP $30 - 60/kWh or $40 - 100/kWh, NMC $50 - 90/kWh, and LMO $45 - 55/kWh. Olivine and NMC (or NCA) can become cheaper (e.g., $26 - 52/kWh, then, $22 - 44/kWh by replacing LFP to LMP, then, to LCP, $37.5 - 67.5/kWh, hopefully, $25 - 45/kWh by adopting lithium-rich chemistry.). Although energy density (both gravimetric and volumetric) can be improved, there still is a difficulty in decreasing the cost when aiming at $125/kWh battery.