Thermal Behavior of Charged Cathode Materials Studied by Synchrotron-Based X-ray Techniques Won-Sub Yoon 1, *, Kyung-Wan Nam 2, Kyung Yoon Chung 3, Mahalingam Balasubramanian 4, Dong-Hyuk Jang 1, Joengbae Yoon 1, Jonathan Hanson 2, Xiao-Qing Yang 2, James McBreen 2 1 Department of Energy Science, Sungkyunkwan University, Suwon 440-746, South Korea 2 Chemistry department, Brookhaven National Laboratory, Upton, NY 11973, USA 3 Korea Institute of Science and Technology (KIST), Seoul 136-791, South Korea 4 Advanced Photon Source, Argonne National Lab. Argonne, IL 60439, USA * email: wsyoon@skku.edu
Gravimetric Energy Density (Wh/kh) Comparison of rechargeable batteries 250 Smaller 200 150 Lighter Rechargeable Lithium Battery 100 50 Lead Acid Battery Ni/Cd Battery Ni/MH Battery 0 0 100 200 300 400 Specific Volumetric Energy Density (Wh/l) Comparison of the gravimetric and volumetric energy densities of rechargeable lithium batteries with those of other systems.
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Introduction Safety of Li rechargeable batteries a major technical barrier for more demanding applications such as EV and HEV related to the exothermic reactions in charged batteries at elevated temperatures that results in thermal runaway and catastrophic failure of the battery thermal runaway: reactions between the charged electrodes and the electrolyte Improving the thermal stability of the electrode materials many approaches: doping, surface coating, particle size, and so on better understanding of thermal behavior of the charged electrode
Literature review Thermal behavior of cathode materials Highly deintercalated Li x CoO 2 is decomposed to layered LiCoO 2 and electrochemically inactive Co 3 O 4 at about 250. The reaction process is shown below as Li x<0.4 CoO 2 [(1-x)/3]Co 3 O 4 + xlicoo 2 + [(1-x)/3]O 2 LiMn 2 O 4 is generally considered a safer compound than either LiCoO 2 and LiNiO 2. It is reported that the oxygen release from -MnO 2 starts at about 400. The reaction process is shown below as λ-mno 2 (1/2)Mn 2 O 3 + (1/4)O 2 The layered Li 0.5 NiO 2 converts to the spinel LiNi 2 O 4 when heated near 200. The transformation is accompanied by no weight loss or heat generation. In contrast at higher degrees of deintercalation than x = 0.5, the conversion to spinel is apparently accompanied by significant oxygen evolution and heat generation. Above 400, all of Li x-y Ni 2-x O 2 undergo the following reaction: Li x-y Ni 2-x O 2 Li x-y Ni 2-x O 2-y + (y/2)o 2 Dahn et al, Solid State Ionics, 265 (1994)
Literature review Temperature-induced structural changes in nickel-based cathodes Li 1-x NiO 2 (2-x)Li (1-x)/(2-x) Ni 1/(2-x) O (Fm3m) + x/2 O 2 at ~ 200 Arai et al, Solid State Ionics, 295 (1998) Li 1-x NiO 2 (1-2x)LiNiO 2 () + xlini 2 O 4 (Fd3m) (x<0.5) [Li 1-x Ni (2x-1)/3 ][Ni (4-2x)/3 ]O (8-4x)/3 (Fd3m) + (2x-1)/3 O 2 (x>0.5) Lee et al, J. Electrochem. Soc., A716 (2001) LiNi 1-x M x O 2 (M = Mn, Co, and Al) The decomposition occurs in two steps: 1 st transition layered to spinel-type phase 2 nd transition pseudo-spinel phase to NiO-type phase through a highly disordered phase Guilmard et al, Chem. Mater., 4484 (2003) Most temperature dependent diffraction studies of the structure of the charged electrodes have been performed in the absence of electrolyte/solvents. Need to investigate the structural changes of the charged cathode materials in the presence of electrolyte using in situ x-ray diffraction
In-situ XRD data: Electrolyte effect Li0.67Ni0.8Co0.15Al0.05O2 with/without electrolyte (50%SOC) Yoon et al., ESSL, 2005 450 C Li 2 CO 3 phase 111 200 220 Fm3m 240 C 25 C 003 002 Graphite 102 101 105 104 107 113 110 108 10 15 20 25 30 35 40 10 15 20 25 30 35 40 without electrolyte with electrolyte Electrolytes accelerate the thermal decomposition and change the decomposition path!!
(220) (200) (111) (113) (110) (108) (107) (105) (104) (102) (101) (003) TR-XRD study on thermal stability of Li 0.33 NiO 2 with electrolyte (as a reference) In situ time-resolved (TR) XRD of charged cathode materials during heating Samples Heating capillary Samples in capillary Average structural information (long range order) during heating Metallic nickel Rock salt structure 450 o C - Li 0.33 NiO 2 A good road map for the structural changes of nickel-based cathode materials during heating. Fm3m Heating up to 450 o C Metallic Ni Disordered spinel structure 210 o C Fd3m Layered structure 25 o C Li 0.33 NiO 2 goes through a whole series of phase transitions (i.e., thermal decomposition) when heated up to 450 o C. 20 30 40 50 60 70 2 ( =1.54 )
(220) (200) (111) (113) (110) (108) (107) (105) (104) (102) (101) (003) Thermal stability of charged Li 0.33 Ni 0.8 Co 0.15 Al 0.05 O 2 (NCA) with electrolyte Heating up to 450 o C Rocksalt 450 o C Fm3m Disordered spinel LiM 2 O 4 type At ~265 C 260 o C 240 o C 200 o C 25 o C Fd3m graphite 20 30 40 50 60 70 2 ( =1.54 ) 8a tetrahedral site : Mostly lithium (220) spinel (440) 10 20 30 40 layered Much better thermal stability than Li 0.33 NiO 2. Narrow temperature range (~20 o C) for the disordered spinel region. (boxed region)
(220) (200) (111) (113) (110) (108) (107) (105) (104) (102) (101) (003) Thermal stability of charged Li 0.33 Ni 1/3 Co 1/3 Mn 1/3 O 2 (NCM) with electrolyte (a) Heating up to 600 o C metalic phase Rocksalt Fm3m Fd3m 600 o C 441 o C 304 o C 236 o C 25 o C 2 types of disordered spinel M 3 O 4 type LiM 2 O 4 type 8a tetrahedral site : Mostly transition metal 8a tetrahedral site : Mostly lithium graphite 20 30 40 50 60 70 2 ( =1.54 ) Much wider temperature range (~140 o C) for the disordered spinel region (boxed region) due to the stabilization of two different spinel-type structures. much better thermal stability!! K. W. Nam et al, Journal of Power Sources, 189 (2009) 515 pp. layered
(220) (200) (111) (220) (200) (111) (220) (200) (111) (113) (110) (108) (107) (105) (104) (102) (101) (003) (113) (110) (108) (107) (105) (104) (102) (101) (003) (113) (110) (108) (107) (105) (104) (102) (101) (003) Comparison of thermal stability of charged layered cathodes with electrolyte metalic phase 600 o C Metallic Ni Fm3m 450 o C 450 o C 441 o C Fm3m Fd3m Fm3m Fd3m 260 o C 304 o C 236 o C 210 o C Fd3m 25 o C 25 o C 25 o C 20 30 40 50 60 70 2 ( =1.54 ) 20 30 40 50 60 70 2 ( =1.54 ) 20 30 40 50 60 70 2 ( =1.54 ) Li 0.33 NiO 2 Li 0.33 Ni 0.8 Co 0.15 Al 0.05 O 2 Li 0.33 Ni 1/3 Co 1/3 Mn 1/3 O 2 NCM cathode shows the best thermal stability due to the large spinel stabilized temperature region. why? Need better understanding of role of each elements during thermal decomposition.
Normalized intensity (a. u.) FT magnitude ( a. u. ) Mn K-edge XANES and EXAFS of charged Li 0.33 Ni 1/3 Co 1/3 Mn 1/3 O 2 (NCM) during heating 1.6 1.2 0.8 0.4 In depth analysis of better thermal stability of NCM cathode using XAS EXAFS : local atomic structure 45 XANES : Oxidation state Mn-O Mn-M NCM NCM (Li 1-x Ni 1/3 Co 1/3 Mn 1/3 O 2 ) 25 o C 100 o C 150 o C 200 o C 250 o C 300 o C 350 o C 400 o C 450 o C 500 o C 40 35 30 25 20 15 10 5 500 o C 450 o C 400 o C 300 o C 200 o C 25 o C Preserving local structure around Mn during heating. 0.0 6535 6540 6545 6550 0 Before charge 6540 6550 6560 6570 Energy ( ev ) No reduction of Mn ions during heating. 30 20 10 NiO CoO Co 3 O 4 0 1 2 3 4 5 6 Interatomic distance ( A ) Excellent thermal stability of Mn 4+ ions in the charged Li 0.33 Ni 1/3 Co 1/3 Mn 1/3 O 2 cathode. likely due to the high preference of octahedral coordination of Mn 4+ ions.
003 In-situ XRD data Comparison of Li0.33Ni1-xCoxO2 with MgO-coated Li0.33Ni1-xCoxO2 102 101 104 105 107 113 110 108 003 102 101 104 105 107 113 110 108 450 o C 111 200 220 Fm3m 450 o C 220 Spinel Ni 2 O 3 240 o C 240 o C 25 o C 002 Graphite 10 15 20 25 30 35 40 25 o C 002 Graphite 10 15 20 25 30 35 40 Uncoated Li 0.33 Ni 1-x Co x O 2 MgO-coated Li 0.33 Ni 1-x Co x O 2 Much slower decomposition!!
Voltage (V) In-situ XRD data: first charging curve Li1.2Ni0.133Co0.133Mn0.533O2 after first charge activation 4.8 4.6 4.4 4.2 4.0 3.8 3.6 : 312 mah/g - C-rate C/C = C/16 C/V = C/80 - Cut off : 4.7V -A.M / Current Activation : 3.7014 mg C/C = 0.0854 ma C/V = 0.0168 ma 3.4 3.2 3.0 0 50 100 150 200 250 300 350 Capacity (mah/g) Li 1.2 Ni 0.133 Co 0.133 Mn 0.533 O 2 = 0.5Li 2 MnO 3-0.5LiNi 0.333 Co 0.333 Mn 0.333 O 2
Intensity (arb. unit) (111) (003) In-situ XRD data Li1.2Ni0.133Co0.133Mn0.533O2 after first charge activation (220) (311) (102) (101) (222) (400) (104) (331) (105) (511) (422) (107) (440) (108) (110) (113) (531) Intensity (arb. unit) (111) (003) (220) (311) (111) (222) (012) (101) (200) (400) (104) (015) (422) (511) (107) (220) (440) (110) (018) (113) (311) no electrolyte with electrolyte Fm3m Metallic Fd3m 600C 600C 466C 379C Fd3m 393C 207C Beam dump 20 30 40 50 60 70 2 ( =1.54) 20 30 40 50 60 70 2 ( =1.54) Li-rich layered cathode shows more complicating decomposition reaction with electrolyte.
Thermal Abuse: In situ XRD Olivine cathode (LiMnPO 4 ) : electrolyte effect Intensity (arb. unit) (2 0 0) (2 0 0) (1 0 1) (2 1 0) (0 0 1) (0 2 0) (2 1 1) (3 0 1) (3 0 1) (3 1 1) Intensity (arb. unit) (2 0 0) (2 0 0) (1 0 1) (2 1 0) (0 1 1) (0 2 0) (2 1 1) (3 0 1) (3 0 1) (3 1 1) LMP pure (100% charge:with electrolyte) LMP pure (100% charge:without electrolyte) 595C 595C 505C 505C 400C 400C 295C 295C 205C 205C (1 1 1)(1 1 1) 16 18 20 22 24 26 28 30 32 34 36 2 ( =1.54) (0 2 0) (2 1 1) 100C 25C (1 1 1)(1 1 1) 16 18 20 22 24 26 28 30 32 34 36 2 ( =1.54) 2MnPO 4 Mn 2 P 2 O 7 +0.5O 2 Olivine cathode shows less sensitivity with electrolyte. ICSD # :047137 : Mn 2 P 2 O 7 (0 2 0) (2 1 1) 100C 25C
Thermal Abuse: In situ XRD Olivine cathode (LiMn 0.88 Mg 0.1 Zr 0.02 PO 4 ) : doping effect Intensity (arb. unit) (2 0 0) (2 0 0) (1 0 1) (2 1 0) (0 0 1) (0 2 0) (2 1 1) (3 0 1) (3 0 1) (3 1 1) Intensity (arb. unit) (2 0 0) (1 0 1) (0 1 1) (1 1 1) (3 0 1) LMP pure (100% charge:with electrolyte) LMP doping (100% charge:with electrolyte) 595C 595C 505C 505C 400C 400C 295C 295C 205C 205C 100C 100C (1 1 1)(1 1 1) 16 18 20 22 24 26 28 30 32 34 36 2 ( =1.54) (0 2 0) (2 1 1) 25C 16 18 20 22 24 26 28 30 32 34 36 2 ( =1.54) 2MnPO 4 Mn 2 P 2 O 7 +0.5O 2 Doped olivine cathode shows better thermal stability with electrolyte. (0 2 0) (2 1 1) 25C ICSD # :047137 : Mn 2 P 2 O 7
Summaries - Synchrotron based X-ray results clearly elucidate the thermal decomposition mechanism of charged cathode materials in the presence of electrolyte. - The electrolyte accelerates the thermal decomposition of the charged cathode materials - The presence of electrolyte alters the paths of the structural changes and lowers the onset temperatures of the reactions. - The electrolyte induced thermal decomposition of nickel containing layered cathode can be successfully suppressed by MgO surface coating. - Li-rich layered compounds show more complicating decomposition reaction compared to other nickel containing layered compounds. - Olivine cathode materials show less sensitivity in the presence of electrolyte. - The thermal XRD study helps design thermally stable and safer cathode materials.
Thank you!!!