Structural and electrochemical study of Li[CrxLi(1−x)/3Mn2(1−x)/3]O2 (0≤x≤0.328) cathode materials

Spectroscopic analyses of 0.5Li[Ni0.8Co0.15Zr0.05]O2–0.5Li[Li1/3Mn2/3]O2 composite cathodes for lithium rechargeable batteries

“…The occurrence of such "disturbed" regions have also been reported in active: inactive based composite cathodes. These regions form nanosize domains in the primary cathode particles and in these nanodomains, it is claimed that lithium ions form super-lattice ordering with the cations in transition metal layers [8]. The measured 'd' spacing (∼ 4.4 Å) in these disturbed regions are smaller as compared to that in regular lattice fringe regions.…”

“…Thus, we have synthesized xLi(Ni 0. 8 [10]. The structure of the pristine cathodes has been characterized in terms of Rietveld structural refinement of the X-ray diffraction pattern in conjunction with Raman scattering measurements.…”

“…Repeated cycling in the voltage range of 4.8-1.45 V, and the accompanied volume change of cathode particle probably disintegrate the bonding between the composite cathode and aluminum electrode which eventually results the observed capacity fading. Deep discharge of these cathodes beyond 2.0 V is therefore not recommended for these cathodes.Based on the analyses presented above, we have constructed a tentative phase diagram that illustrates the lithium ion intercalation behavior of 0.5Li[Ni 0 8. Co 0.15 Zr 0.05 ]O 2 -0.5Li[Li 1/3 Mn 2/3 ]O 2 composite cathode.…”

Nanoscale Surface Modification of Lithium‐Rich Layered‐Oxide Composite Cathodes for Suppressing Voltage Fade

“…[4,5] Ty pically,L i-rich layered oxidesa re composed of mono-clinicL i 2 MnO 3 (C2m)a nd hexagonal a-NaFeO 2 -structured LiMO 2 (R3m), andc an also be writtena sL i 1+x M 1Àx O 2 .T he crystalstructure of lithium-rich layeredLi 2 MO 3 can be related to that of layeredL iMO 2 ,w itht he excess lithiumi ons occupying transitionm etal (TM) ion sites in the TM layer (Supporting Information, Figure S1 B).Therefore,the Li 2 MO 3 component plays avital roleinstoring the excess lithium and securing the highv oltagea nd specific capacity.H owever, ag raduald ecrease of the averagec harge-discharge voltage hasb eeno bservedf or lithium-rich layeredo xides whent hey werec ycled above 4.5 V, which is referred to as "voltage fade". [9] Thecationic doping of Li 1+x M 1Àx O 2 with Al, [12] Ti, [13] Zn, [14] Cr, [15] Y, [16] or Mg [17] is an effective approach that has been extensively studied for stabilizing the crystal structure and minimizing the voltage fade.Meanwhile,coating the surfaces of lithium-rich layered oxides with metal fluorides (AlF 3 ), [18] metal oxides (Al 2 O 3 ,M gO,Z rO 2 ,a nd ZnO), [19][20][21][22] or metal phosphates (AlPO 4 and CoPO 4 ), [23,24] is widely used to prevent them from etching by the electrolytes.B oth surface coating and doping are novel methods for modifying the structure and improving the cycling stability of lithium-rich layered oxides.However,asmost of the cationic dopants and surface-coating layers are electrochemically inactive during the charge/discharge processes,t he advanced structural and cycling stability comes at the cost of reducing the specific capacity and energy density of the cathode.M oreover,a s most of the surface-coating layers have low electronic or lithium-ion conductivity,t hey will block the ion and charge transport channels on the surface of lithium-rich layered oxides and reduce their rate capacities.Recently,Nanda et al reported the use of an anometer-thick lithium-conducting solid electrolyte (lithium phosphorus oxynitride,L iPON) as ac oating for lithium-rich layered oxides, Li 1.2 Mn 0.525 Ni 0.175 Co 0.1 O 2 ;t he resulting cathode exhibited excellent rate performance and capacity retention. [10,11] Meanwhile,lithium-rich layeredoxideshavebeenfound to be unstable in highly lithiated/delithiated statesw ithc harge/ discharge voltages above 4.5V ,l eading to exothermic reactions with electrolytesand accelerated voltage/capacity fade.…”

“…[6][7][8][9] Thec ontinuous voltagef ade resultsi nadramatic decrease of the cathode energy density.T he migrationofTM ionsf romt he TM layer to the lithium layer,w hich is accompanied by local phaset ransformations from hexagonal layeredt oc ubic spinels tructures( Figure S2) caused by frequent (de)intercalation processes,d uring cycling above 4.5Vis thought to be the mainreason for the voltage fade. [9] Thecationic doping of Li 1+x M 1Àx O 2 with Al, [12] Ti, [13] Zn, [14] Cr, [15] Y, [16] or Mg [17] is an effective approach that has been extensively studied for stabilizing the crystal structure and minimizing the voltage fade.Meanwhile,coating the surfaces of lithium-rich layered oxides with metal fluorides (AlF 3 ), [18] metal oxides (Al 2 O 3 ,M gO,Z rO 2 ,a nd ZnO), [19][20][21][22] or metal phosphates (AlPO 4 and CoPO 4 ), [23,24] is widely used to prevent them from etching by the electrolytes.B oth surface coating and doping are novel methods for modifying the structure and improving the cycling stability of lithium-rich layered oxides.However,asmost of the cationic dopants and surface-coating layers are electrochemically inactive during the charge/discharge processes,t he advanced structural and cycling stability comes at the cost of reducing the specific capacity and energy density of the cathode.M oreover,a s most of the surface-coating layers have low electronic or lithium-ion conductivity,t hey will block the ion and charge transport channels on the surface of lithium-rich layered oxides and reduce their rate capacities.Recently,Nanda et al reported the use of an anometer-thick lithium-conducting solid electrolyte (lithium phosphorus oxynitride,L iPON) as ac oating for lithium-rich layered oxides, Li 1.2 Mn 0.525 Ni 0.175 Co 0.1 O 2 ;t he resulting cathode exhibited excellent rate performance and capacity retention. [9] Thecationic doping of Li 1+x M 1Àx O 2 with Al, [12] Ti, [13] Zn, [14] Cr, [15] Y, [16] or Mg [17] is an effective approach that has been extensively studied for stabilizing the crystal structure and minimizing the voltage fade.Meanwhile,coating the surfaces of lithium-rich layered oxides with metal fluorides (AlF 3 ), …”