高能量富锂锰基材料

Positive electrode materials xLi2MnO3• (1-x)LiMO2 (M=Mn,Ni,Co…) Jie Wang Materials Science Division Sinopoly Battery Research Center, Shanghai; Oct., 2012 Outline Introduction The strategy of cells for EV/HEV/PHEV and their positive electrode materials The Positive electrode materials xLi2MnO3• (1- x)LiMO2(M=Mn,Ni,Co…) Application problems & Probable solutions Development in industry & lab Conclusion To provide adequate boost in HEV/EV applications Lifetime Safety Cost Power Calendar life: 15 years Cycle life: HEVs micro-cycle lifetime EVs full-cycle lifetime PHEVs both micro-and full-cycle lifetimes catastrophic One of the Largest obstacles to the commercialization of PHEVs and EVs Energy To provide adequate range within weight and space constrains more important for PHEVs and EVs than for HEVs Five Goal Categories of cells for EV/HEV/PHEV 4 Li-ion battery hold more promise for meeting performance criteria than any other cells MN Li1.2Mn0.6Ni0.2O2/graphite LTO LiMn2O4/Li4Ti5O12 MNS LiMn1.5Ni0.5O4/Li4Ti5O12 LMS LiMn2O4/graphite NCM LiNi/3Co1/3Mn1/3O2/graphite NCA LiNi0.85Co0.1Al 0.05O2/graphite LFP LiFePO4/graphite LCO LiCoO2/graphite Capacity is defined to be a composite of energy, power, lifetime and safety characteristics. Cost is not considered in this table. Pb- Acid Li-ion Batteries maturity Source from David Anderson , Rocky Mountain Institute，2008 Li-ion cell chemistry experience Company Attractive positive electrode material Sanyo LiMxCo Saft LiNiMxCo Samsung LiNiMxCo Gaia UHP LiNiMxCo, LiMn2O4+LTO Eone/Molicel LiMn2O4 Toshiba LiMnO+LTO Hitachi LiMnO A123 NanophosphateTM Strategy for cathode Layer or tunnel materials which work as hosts for lithium have merits High reversibility stable structures over a wide compositional range enough interstitial space Small side reaction High power density High energy density Long cycle life …… Cathodes under development Layered materials Co-based, Ni-based, Mn-based Spinel structure LiMn2O4, LiMn1.5Me0.5O4 Olivines LiFePO4, LiMePO4 Differences in lithium ion conduction paths and stability in the delithiated state Mn-based layered cathode In positive electrode, there are few candidates which possess much higher specific capacity. Doping-LiMnO2 Mn3+ LiNi1/3Co1/3Mn1/3O2 LiNi1/2Mn1/2O2 Mn4+ Positive electrode materials xLi2MnO3• (1-x)LiMO2 (M=Mn,Ni,Co…) Layered-Layered xLi2MnO3• (1-x)LiMO2 (M=Co, Ni, Mn) •Li2MnO3 electrochemically inactive; where as LiMO2 is active with respect to Lithium insertion/extraction ; •Strategy: Embed inactive Li2MnO3 component within layered LiMO2 structure to stabilize electrode and reduce oxygen activity at surface of charged particles; Source: Dr. Michael Thackeray, Argonne National Laboratory. Application problems & Probable solutions High specific capacity (>250mAh/g); Integration and interconnection of LiMO2-like (rhombohedra) and Li2MnO3 (monoclinic) structures at atomic level;  Good high-temperature cyclic performance ;  Structure changes during cycling. Advantages:  Li+ migrates through the binder polymer bulk via interaction with the polymer chains; Large irreversible capacity loss during first charge; Voltage and capacity fading during cycle;  Rearrangement of TM ions; High voltage accessible to the decomposition of electrolyte. Issues to be addressed: Approach little irreversible capacity loss good cyclability V2O5-composite xLi2MnO3•yLiMO2 advantage A. Manthiram, et al, Electrochemistry Communications 11 (2009) 84–86 The lithium-free V2O5 serves as an insertion host to accommodate the lithium ions that could not be inserted back into the layered lattice after the first charge. Disadvantage The problem of Oxygen release have not solved More favorite for battery with Li metal as anode MCMB / V2O5 -0.25Li2MnO3·0.75LiNi1/2Mn1/2O2 0.1C charge -discharge Approach 3000 4000 5000 -40 -20 0 20 40 60 80 100 120 2 nd 1 st d Q /d V ( m A h g -1 v -1 ) Voltage(mV)vs.Li/Li + 3000 4000 5000 -40 -20 0 20 40 60 80 100 2 nd 1 st (d Q /d V )( m A h g -1 v -1 ) Voltage(mV) vs. Li/Li + (a) (b) Differential capacities vs. voltage curves of the cells containing 0.25Li2MnO3·0.75LiNi1/2Mn1/2O2 material low irreversible capacity loss Less oxygen release. advantage disadvantage Relatively low capacity Under an extreme synthesis condition-Suppress the appearance of irreversible peak upon the first charge Approach Yuichi. Sato, Journal of power sources. 2008, 183, 344-346 The poor cyclic performance at high voltages could be significantly improved through a pre- cycling treatment in the different voltage ranges. Approach  The preconditioning reaction passivates the whole electrode surface, generates a fluorinated layer that is chemically robust at high potentials;  The surface of the electrode particles may be protected by strong oxyfluoride bonds that lower the oxygen activity of the surface at high potentials;  the reduced oxyfluoride surface imparts some mixed valence to the bonded transition-metal ions, thereby increasing the electronic conductivity at the particle surface. M. M. Thackeray, J. Electrochem. Society, 2008, 155, A275-A275 Approach Kyu-Sung Park,, Journal Materials Chemistry. 2010, 20, 7208-7213 Al2O3 orAlPO4 phase coated on the surface effectively mitigates the key problems associated with oxygen gas evolution and transition metal dissolution. AlF3 coated Pristine Pristine AlF3 coated RT 55oC Coating the cathode with nano-AlF3 film can stabilize the interface and prevent surface reaction at high voltage and high temperature operation. Y. Yang, J. Electrochem. Society, 2008, 155, A775–A782 Approach 0 50 100 150 200 250 300 350 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.0 3.5 4.0 4.5 5.0 AlF 3 -coated V o lt ag e / V Io n cu rr en t / 1 0 -1 1 A /g Time / min O 2 (m/e = 32) 0 50 100 150 200 250 300 350 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.0 3.5 4.0 4.5 5.0 O 2 V o lt ag e / V Io n cu rr en t / 1 0 -1 1 A /g Time / min (m/e = 32) pristine 0 50 100 150 200 250 300 350 0 1 2 3 4 5 3.0 3.5 4.0 4.5 5.0 V o lt ag e / V Io n c u rr en t / 1 0 -1 1 A /g Time / min CO 2 (m/e = 44) AlF3-coated 0 50 100 150 200 250 300 350 0 1 2 3 4 5 3.0 3.5 4.0 4.5 5.0 (m/e = 44) V o lt ag e / V Io n c u rr en t / 1 0 -1 1 A /g Time / min pristineCO 2 1/4 5 times In-situ Electrochemical Mass spectroscopic techniques and Its use in Li-ion batteries AlF3 coating layer provides a buffer layer to make oxygen atoms with high activity combine together to form O2 molecules with low oxidation capability to electrolytes. Approach ALD is a well established method to coat thin films on high-surface area tortuous materials TiO2 coated sample show better cyclic performance Manthiram, J. Mater. Chem., 2009, 19, 4965–4972 Manthiram, J. Mater. Chem., 2009, 19, 4965–4972 TiO2 ALD coating partially suppressed the Ni and Mn reduction at surface  Surface coating partially isolates the surface of the material from the electrolyte, supressing the chemical reduction of Ni4+;  Surface coating may suppress the surface structure change and prevent the dissolution of Mn2+. Approach Manthiram, J. Phys. Chem. C., 2010, 19, 132–138 The suppression of both the oxygen vacancy elimination at the end of the first charge and side reactions with the electrolyte and the decrease in charge transfer polarization by the Al-modification layer. Developments in industry---Envia System The key to achieving the world record energy density is combining Envia’s proprietary high capacity HCMR™ cathode with its proprietary high capacity Si-C anode. Envia’s HCMRTM Cathode Development By engineering the cathode composition, structure, dopants, morphology and nano-coating, Envia is able to precisely control and tune the specific capacity, cycle life, calendar life, rate capability and physical properties of the material to match any application. Envia’s Electrolyte Development Envia’s Anode Development Envia’s Cell Specifications Cell are tested at ℃ Developments in industry- --BASF Development of HE NCM-Low Cobalt, Low Nickel Cathode Material HE NCM shows excellent capacity and represents a potential cost savings due to the reduced nickel and cobalt composition Development of the BASF’S HE-NCM Cathode Material Discharge profiles BASF HE-NCM vs. BASF NCM-111 BASF’S HE-NCM vs. graphite Cycling stability in Swagelok cells  Marked Capacity increase at slightly lower voltage ‘High Energy”;  HE-NCM delivers higher capacity (~200mAh/g) and excellent cycling. TODA AMERICA---R&D on LMNC cathode materials Technical Progress & Accomplishment for Toda Performance of pristine electrode cycled between (4.9-2.5V) Electrolyte: 1.2M LiPF6 in EC:DMC (1:2 wt./wt.) Summary a) 1st cycle irreversible capacity loss (ICL) =18-20%(cycled to 4.9V) b) Rapid drop in capacity after 120-150 cycles c) Continuous voltage plateau drop with cycling d) Clear appearance of low voltage plateau at below 3V GS Yuasa(Lithium Energy Japan) a) The layered Li1.2Co0.1Ni0.15O2 solid solution material with a stable delivered capacity of 250mAh/g(0.1C)； b) Excellent rate cycling，High coulombic efficiency； c) 0.8Ah small prismatic cell; Samsung Yokohama Research Institute Using the modified thermally stable material, Separator & electrolyte(Fluorinated Electrolyte) to fabricate Laminate-type cell (a); The capacity retention is about 87％ after 400 cycle at 25℃ (b); The capacity retention is still 87％after 200 cycles at 45℃ (c). Samsung Yokohama Research Institute Managing ? (reducing heat generation rate) a) PE material: thermally stable material b) PE surface film: composition design c) PE additive: Retardant in electrolytes AIST a) layered Li2MnO3‐LiFeO2 solid solution, The lower discharge voltage; b) Developing the Ni doped Li2MnO3‐LiFeO2 materials system in 2009， increasing the discharge voltage or the reversible capacity; c) The cost is lower than that of the Li2MnO3‐LiMO2 (M=Ni or Co). Complex Synthesis = Complex Structures ANL  Ideal ‘layered-layered’ : No transition metal ions in Li layers  Ideal ‘ layered-layered-spinel’ : 25% transition metal ions in Li layers of spinel domains & vice-versa  Ideal ‘layered-layered-rocksalt’ : No Li layers in rocksalt domains Synthesis: Alternative synthesis are/will be needed to overcome the problems with the LMR-NMC materials. Key to the success of this initiative are materials synthesis and surface treatment techniques that can be employed to mitigate the structural changes present in the LMR-NMC materials. Surface Stabilization by Sonication e.g., TiO2-coated 0.5Li2MnO3•0.5LiNi0.44Co0.25MnO2(NMC)  Sonication: Formation » growth» implosive collapse of bubbles, that locally increases temperature and pressure.  Use high energy process to simultaneously clean surface and coat nanoparticles. Electrochemical Data of Untreated and Sonicated NMC Electrodes (TiO2) at 55℃ Electrochemical Data of Untreated and Sonicated NMC Electrodes (ZrO2) at 55℃ Approach Y. K. Sun, K. Amine, and B. Scrosati, Adv. Mater. 2012, 24, 1192-1196 AF3 is the most promising because an amphoteric Al2O3(or other metal oxides) coating layer has low stability in lithium cell since it can be converted to AlF3 from the exposure to trace of HF in the electrolyte during cycling due to low Gibbs free energy of formation of AlF3 compared to that of Al2O3. In the process, there is a possibility that a part of the Al2O3 coating layer can peel off from the cathode surface, thereby deteriorating the cycling performance and rate capacity. ~1nm AlF3 layer on particle surface Post treatment/system level fixes Addressing the Voltage Fade Issue An alternative to the synthesis “fix” is changes to the material that helps mitigate the voltage fade. These are changes to the LMR-NMC material after it has been prepared, such as coating or physical changes. 0.5Li2MnO3• 0.5LiNi0.44Co0.25Mn0.31O2 Voltage fade is less in treated electrodes but still significant Ion-exchange reaction Layered Na transition metal oxide precursor synthesis 800 - 900 ºC, air 0.5Na2CO3 + 0.1Li2CO3 + Ni0.25Mn0.75CO3 + δO2 »»» Na1.0Li0.2Ni0.25Mn0.75Oy + 2.2 CO2 Large Na cation radii size negates Ni site disorder.  Exposed crystal platelets maintain hexagonal symmetry & can provide fast pathways for Li diffusion.  TEM show layered stacking faults and edge defects  Resultant crystal has small particle size, featuring layered crystal plates that have defects at the surface  Creation of multiple entry points for Li may account for the high-power in the cathode;  Rate –variable; best materials~150mAh/g@10C rate, common is ~200mAh/g @2Crate Li+/Na+ ion-exchange reaction ORNL Improving the Rate Performance of Li-rich MNC Coating a few nanometer layer of Lithium Phosphorus Oxynitride (LIPON)-1 0.6Li2MnO3•0.4Li[Mn0.3Ni0.45Co0.25]O2  Excellent improvement in rate performance by LIPON Coating (~240mAh/g at C/2);  LIPON was coated using RF magnetron sputtering method;  XPS results (not shown) show evidence of LIPON films on surface;  LIPON coating not conformal; can vary from few nanometer to tens of nanometer;  LIPON coated sample demonstrated repeatable cycling 130mAh/g at 15C; Other Company or Research Institutes Dow Energy Materials (DEM), a business unit of The Dow Chemical Company formed in 2010 to focus on the development of advanced battery systems (cathode, anode, electrolyte) presented a poster on its current coated graphite anode and coated NMC cathode and a second poster on its high voltage ethylmethoxyethyl sulfone electrolyte at EVS26 in Los Angeles. Conclusion 1. the ideal composition - Li1+x(MnzNiyCo1-y-z)1-xO2? 2. Impact of Synthesis on atomic order 3. Conductivity xLi2MnO3•yLiMO2 a promising cathode material for EV and PHEV High energy density low $/kWh High structural and thermal stability Consideration Thanks for your attention!