STUDY OF HIGH ENERGY CATHODE MATERIALS : LI-RICH MATERIALS

Transcription

1 STUDY OF HIGH ENERGY CATHODE MATERIALS : LI-RICH MATERIALS Jean-François Colin, A. Boulineau, L. Simonin, D. Peralta, C. Bourbon, F. Fabre CEA LITEN DEHT October 28 th, 2014

2 MATERIALS FOR POSITIVE ELECTRODE Li 2 CoPO 4 F LiNiPO 4 Instability of the electrolyte LiCoPO 4 Li 2 CoSiO 4 LiMn 1.5 Ni 0.5 O 4 Li 2 MnSiO4 Voltage LiMn 2 O 4 LiCoO 2 NCA, NMC Market LiFePO 4 Capacity Energy Density above 250 Wh.kg -1 (graphite negative electrode) Li 1+x M 1-x O 2 2

3 Capacity (mah/g) STRATEGY 2 : INCREASE CAPACITY : LI-RICH MATERIALS Interests : Li 1+x M 1-x O 2 (0<x<1/3 ; M = Mn, Ni, ) High specific capacity > 250mAh/g (vs. 180mAh/g for NMC) High energy applications > Wh/kg Low cost materials ,4 % % Charge capacity discharge capacity Potential - 0,3% / cycle - 0,1% / cycle % Potential (V) Main Issues to be solved : Structural mechanism understanding -> O 2 in red-ox reactions? 1 st high irreversible specific capacity Gaz generation issue during 1 st cycles Voltage decay upon cycling Thermal stability & power perfs improvement Cycle number 3.4 3

4 LI-RICH MATERIALS SOLID STATE SYNTHESIS Synthesis from carbonate precursors Optimisation carried on thermal treatment parameters : Capacité spécifique / mah.g nm 400 nm 500 nm 600 nm Optimum found at nm But still suffers from low taped density : d=1.1 g/cm 3 Low energy density Nombre de cycles 4

5 LI-RICH MATERIALS LIQUID SYNTHESIS Multiparameters synthesis : ph, stirring speed, solutions flow, T, duration Use of a Design Of Experiment 5

6 LI-RICH MATERIALS LIQUID SYNTHESIS Enhanced performances : C : 250 mah/g d= 1.6g/cm 3 Spherical particles 6

7 LI-RICH MATERIALS LIQUID SYNTHESIS Pilot scale production : 1kg batch 7

8 Li-rich lamellar oxides : structural study Li 1+x M 1-x O 2 : M : Co, Ni, Mn Li 1.2 Ni Mn O 2 = Li(Li 0.2 Ni Mn )O 2 Can also be seen as 0.5 Li 2 MnO LiMn 0.5 Ni 0.5 O 2 R3m LiMn 0.5 Ni 0.5 O 2 OR Li 1.2 Ni Mn O 2 Li 2 MnO 3 C2/m? 8

9 COMPOSITE OR SOLID SOLUTION? Li 1+x M 1-x O 2 : M : Co, Ni, Mn Li 1.2 Ni Mn O 2 = Li(Li 0.2 Ni Mn )O 2 Can be also seen as 0.5 Li 2 MnO LiMn 0.5 Ni 0.5 O 2 9

10 COMPOSITE OR SOLID SOLUTION? HAADF- STEM Succession of domains separated by stacking faults Same structure in all domains but 3 different orientation (±60 ) Nanobeam electron diffraction 10

11 COMPOSITE OR SOLID SOLUTION? HAADF- STEM Bragg filter Variation of contrast variation of chemical composition : Bright region : TM slabs, Dark region Li 1/3 TM 2/3 Bragg filter on C2/m spots increase the contrast 45% TM / 55% Li 1/3 TM 2/3 COMPOSITE 11

12 Voltage / V vs. Li + /Li Structural evolution of Li-rich lamellar oxides during cycling 1.1 Li could extracted with a reversibility on 0.8Li New electrochemical profil : a plateau at 4.6V vs Li + /Li New phenomenon Classical answer of a lamellar oxide x in Li x Mn 0.61 Ni 0.18 Mg 0.01 O 2 Possible concomitant oxidation of O 2- and Li extraction What impact on structure? In situ XRD and XAS study on first cycle 12

13 Voltage / V vs. Li + /Li EXPERIMENTAL SETUP Measurement in pouch cell X-ray diffraction : First 1.5 cycle BM20 (ESRF) 25keV (0.496Å) Image plate detector Mar min/diffractogramm XAS : First charge BM30B (ESRF) Ni- and Mn-edge EXAFS XANES x in Li x Mn 0.61 Ni 0.18 Mg 0.01 O 2 13

14 X-RAY DIFFRACTION Refinement of cell parameters Space group R-3m : a and b represent layers dimensions c represents the interslab dimension a,b c/3 14

15 Voltage / V vs. Li + /Li a / Angstrom c / Angstrom X-RAY DIFFRACTION 1 st charge For x>0.9 a decreases : M oxidizes decreasing of M-O bond length st charge c increases : decrease of screening effect of Li st charge Solid solution: Classical answer of lamellar oxide For 0.9<x<0.1 No evolution of the cell parameters Biphasic process?? But no new reflexion observable x in Li x Mn 0.61 Ni 0.18 Mg 0.01 O 2 15

16 EXISTENCE OF THE SPINEL PHASE TEM Microscopy study after 1st charge Li column TM column Li and Mn column additional TM column Apparition of a spinel phase at the surface of the particle (111) s =(003) l 16

17 Voltage / V vs. Li + /Li a / Angstrom c / Angstrom X-RAY DIFFRACTION 1 st discharge a comes back to starting value c remains much higher No reversibility with 1st charge st discharge 1st charge 1st discharge 1st charge x in Li x Mn 0.61 Ni 0.18 Mg 0.01 O 2 CEA November, 6th

18 Voltage / V vs. Li + /Li a / Angstrom c / Angstrom X-RAY DIFFRACTION 1 st discharge a comes back to starting value c remains much higher No reversibility with 1 st charge nd charge 1st discharge 1st charge 2nd charge 1st discharge 1st charge 2 nd charge Reversibility of the process occuring during 1 st discharge Creation of a new structure during the first charge that is then reversibly cycled x in Li x Mn 0.61 Ni 0.18 Mg 0.01 O 2 18

19 Capacity (mah/g) VOLTAGE FADING : PROBLEMATIC 4 Energy = Capacity * Potential Voltage decay = Energy fading % Charge capacity discharge capacity Potential % Potential (V) Battery Management System : The potential is not a reflect of the state of charge anymore : impossibility to build a efficient BMS No possible commercialization - 0,3% / cycle 3.6-4,4 % 50-0,1% / cycle Cycle number

20 VOLTAGE FADING STUDY 2 cells are cycled following : - 50 cycles at C/10 (slow rate) - 1 cycles at C/ cycles at C/2 ( high rate) + 1 cycle at C/10 Voltage fading observed for both Disappearing of Li/Mn ordering Less impact for high rate (kinetically limited phenomena) 20

21 VOLTAGE FADING STUDY STEM-EELS experiments - chemical mapping Pristine material 1 C/10 Chemical analysis with atomic column resotultion Homogeneous composition with expected Mn/Ni ratio Apparition of spinel phase without change of composition 21

22 VOLTAGE FADING STUDY 50 C/2 50 C/10 Evolution of composition : Ni Enrichment of surface Stronger evolution for slow rate No growth of spinel domain Voltage decay seems to be linked more to cation migration than spinel growth 22

23 After one charge CATIONIC MIGRATION No TM cation in interslab in the bulk 23

24 After 50 cycles CATIONIC MIGRATION Disorder appears in the bulk with TM cation in the interslab 24

25 VOLTAGE FADING : ELECTROCHEMISTRY Voltage fading : growth of a low potential electrochemical process Is there a link with the other electrochemical processes 25

26 dq/dv(ma.h.g-1.v-1) dq/dv(ma.h.g-1.v-1) dq/dv(ma.h.g-1.v-1) dq/dv(ma.h.g-1.v-1) dq/dv(ma.h.g-1.v-1) dq/dv(ma.h.g-1.v-1) dq/dv (ma.h.g -1.V -1 ) dq/dv (ma.h.g -1.V -1 ) dq/dv (ma.h.g -1.V -1 ) dq/dv(ma.h.g-1.v-1) cycle 2 cycle 3 cycle 4 cycle cycle 2 5 cycle cycle 3 6 cycle cycle 4 7 cycle cycle 5 8 cycle cycle 6 9 cycle cycle 7 10 cycle cycle 8 11 cycle cycle 9 12 cycle cycle cycle 11 cycle 12 cycle 13 Full cycling Full cycling Partial cycling Partial Full cycling 3.55V Partial - cycling 4.8 V Cycles 1CYCLE V Cycles 2.5V Cycles Cycles 3.55V V Cycles 2.5V V 4.8 Cycle V V 4.8 Cycle V V Cycles 1 Cycles Cycle V V Cycles 2-13 Cycle cycle 2 cycle 3 cycle 4 0 cycle cycle 2 5 cycle cycle cycle cycle 4 7 cycle cycle cycle cycle 6 9 cycle cycle 7 10 cycle cycle cycle cycle cycle cycle cycle 11 Partial cycling 1 cycle cycle 13 cycle 12 cycle 13 Cycles 2-13 Cycles CYCLES Cycles Cycles 2 14 Voltage (V) Cycles Cycles Voltage 2 14 Voltage Voltage (V) (V) (V) 4.8 V 3.55 V 4.15 V 2.5 V cycle cycle 3 cycle cycle cycle cycle cycle cycle cycle cycle cycle cycle cycle cycle cycle cycle cycle cycle cycle cycle cycle Partial cycling 1 cycle cycle Cycles cycle cycle Cycles Cycles 14 Voltage (V) V 2.5 Voltage V (V) Partial cycling Voltage (V) Voltage (V) (V) Voltage (V) Voltage (V) (V) cycle 2 cycle 3 cycle 4 cycle 5 cycle 2cycle 6 cycle 3cycle 7 cycle 4cycle 8 cycle 5cycle 9 cycle 6cycle 10 cycle 7cycle 11 cycle 8cycle 12 cycle 9cycle 13 cycle 10 cycle 11 cycle 2 cycle 3 cycle cycle 42 cycle cycle 53 cycle cycle cycle cycle 4cycle 2 cycle cycle cycle cycle 5cycle 3 cycle cycle cycle 42 cycle 2cycle cycle 53 cycle 3cycle cycle 64 cycle 4cycle cycle 75 cycle 5cycle cycle 6cycle cycle 7cycle cycle 8cycle cycle 9cycle cycle cycle cycle cycle cycle cycle cycle cycle Full cycling Full cycling Partial cycling Full Partial cycling Full 2.5V Partial cycling V Partial 3.5 cycling Partial cycling 2 Cycles 14 Cycles CYCLE Cycles Voltage Voltage (V) (V) 4.8 V 2.5 V Cycle 1 cycle 2 cycle 3 cycle 2 cycle 4 cycle 3 cycle 5 cycle 4 cycle 2cycle 6 cycle cycle 2 5 cycle 3cycle 7 cycle cycle 3 6 cycle 4 cycle 4cycle 8 cycle 7 cycle 5 cycle 5cycle 9 cycle 8 cycle 6 cycle 6cycle 10 cycle 9 VOLTAGE FADING cycle 7 cycle 7cycle 11 : ELECTROCHEMISTRY cycle 10 cycle 8 cycle 8cycle 12 cycle 11 cycle 9cycle 13 cycle cycle 9 12 cycle 10 cycle cycle cycle 11 cycle 11 cycle 12 cycle 12 cycle 13 cycle 13 Full Full Full cycling Full cycling Full cycling cycling Full cycling cycle 2 cycle 3 cycle 4 cycle cycle 2 5 cycle cycle 3 6 cycle cycle 4 7 cycle cycle 5 8 cycle cycle 6 9 cycle cycle 7 10 cycle cycle 8 11 cycle cycle 9 12 cycle cycle cycle 11 cycle 12 Full cycling cycle 13 Cycles Cycles 2-13 Cycles Cycles Cycles Cycles V 2.5 cycle V Voltage (V) cycle 3 cycle cycle 42 cycle 2cycle 53 cycle cycle 3 cycle cycle cycle cycle cycle 4 cycle 2 cycle cycle cycle cycle 5 cycle 3 cycle cycle 6 cycle 42 cycle cycle 7 cycle 53 cycle cycle 8 cycle 64 cycle cycle 9 cycle 75 cycle cycle 10 cycle 86 cycle cycle 97 cycle cycle 10 8 cycle cycle 11 9 cycle cycle cycle 12 10cycle cycle cycle cycle cycle cycle cycle Voltage (V) Full cycling Cycles 14 Cycles 14 Cycles 14 Cycles Cycles Cycles V V Voltage (V) Voltage (V) Partial cycling Voltage Voltage (V) (V) Full cycling Voltage 3.5 (V) Voltage Voltage (V) 4.0 (V) Voltage (V) Voltage Voltage (V) (V) (V) (V) Voltage Voltage (V) (V) (V) Voltage (V) Voltage (V) (V) Use of reduced voltage window to deconvolute effect of different electrochemical processes on ageing 26

27 dq/dv(ma.h.g-1.v-1).v -1 ) dq/dv(ma.h.g-1.v-1).v -1 ) VOLTAGE FADING : ELECTROCHEMISTRY Similar ageing as full cycling No ageing 200 a 200 b Full cycling - cycle 2 Full cycling - cycle 14 Cycle 14 after 12 partial cycles (4.8V 3.55V) Voltage (V) Full cycling - cycle 2 Full cycling - cycle 14 Cycle 14 after 12 partial cycles (4.15V 2.5V) Voltage (V) Ageing is due to the high potential electrochemical process Anionic network participation to electrochemistry destabilize the cationic network TM migration 27

28 dq/dv(ma.h.g-1.v-1).v ) VOLTAGE FADING : ELECTROCHEMISTRY 200 cycles 3 to 12 partial cycling 2.5 to 4.15 V cycle 12 full cycling 2.5 to 4.8 V cycles 3 to 12 partial cycling 4.15 to 4.5 V Voltage (V) 28

29 specific capacity (mah/g) potential (V) VOLTAGE FADING : OPTIMISED PROTOCOL a Switch the upper voltage limit from 4.8 V to 4.15 V Partial cycling Full cycling b Partial cycling Full cycling Switch the upper voltage limit from 4.8 V to 4.15 V cycle index cycle index Using a reduced voltage window allow to stabilize potential Few conditionning cycle in full voltage window is necessary to get capacity Still a trade-off between stability and capacity 29

30 Irreversibile capacity (%) Capacity (mah/g) PERSPECTIVES Coating strategies: - Increase the capacity of material - Decrease irreversible capacity - No effect on voltage fading Li1,2Ni0,2Mn0,6O2 Coating A Coating B Coating C Cycle index Doping strategies: - Prevent cationic migration by stabilizing the structure - Negative impact on lithium diffusion? 30

31 CONCLUSIONS Production of Li-Rich materials with high capacities via 2 way of synthesis - Solid state synthesis - Coprecipitation (also at pilot scale) Complex lithiation-delitiation of Li-Rich material have been studied - During first charge : - creation of a spinel phase and irreversible change of layered oxide structure (oxygen oxidation) - During next cycles : - If cycled at high potential : Cationic migration provoked by the destabilisation of the oxygen network : voltage decay - If cycled at low potential : no voltage decay but limited capacity 31

32 THANK YOU! Jean-François Colin DEHT/LITEN Laboratoire des Composants pour Batteries