The University of Texas atAustinrmanth@(Click here那么掺入多少合适呢？Journal of The(Journal of The Electrochemical Society, 152 9 A1714-A1718 2005)(Ni 1/3Mn 1/3Co 1/3)(OH)2(Li 1−z Ni z )3a [(Ni 1/3−z/0.97Mn 1/3Co 1/3)0.97Li z+0.03]3b (O 2)6chelp indirectly to identify the lithium content limit 1 − x within whichy ythe Li−Ni Mn Co O cathode is chemically or structurally stable1x1/31/31/323.0‐4.3 v3.04.6 v问题：为什么充电截止电压超过4.6 v 时其容量衰减变大？同样我们也要问为什么？1‐x=0.35but theoxygen loss occurs at a much lowerlithium content 0.35 in theLi 1−x Ni 1/3Mn 1/3Co 1/3O 2system 05 in the 0.5Li1−x CoO 2system那么1‐x=0.35与充电截止电压(4.6v)有什么样的关系呢？1‐x=0.35chemical instability plays a critical role in the capacity retention and in controlling the practical capacities of the Li1−x Ni1/3Mn1/3Co1/3O2 system.a qualitative band diagram for the Li 0.35N i1/3Mn 1/3Co 1/3O 2systemO3‐type LiMO2O1‐type MOO3‐type LiMO21 x <0.23a new phase is formed−1-x=0.35Ni1/3Mn 1/3Co 1/3O 2−δ(O1 type)放电曲线d h d fi i due to the oxygen ‐deficientnature of Ni 1/3Mn 1/3Co 1/3O 2− δ s Ni Mn Co O −δ1/31/31/32δ放电之后的XRD 因此，这种不可逆相变会导致容量的急剧衰减。

l h i l d lid Electrochemical and Solid ‐State Letters, 8 (8) C102‐C105 (2005)什么是Irreversible Capacity Loss (IRC)?充电曲线the first cycle放电曲线is the higher irreversible capacity loss in the first cycle 为什么？晶格参数差异不大，离子混杂程度相差也不大。

那么是什么因素导致这种材料具有较大的IRC 呢？900℃800℃600℃IRC的差异呢？LiNi1/3Mn 1/3Co 1/3O 23.0‐4.6v3.0‐4.3v LiCoO 2 3.0‐4.6v 无离子混杂问题：为什么表面积越大，IRC 值越大呢？the parasitic electrochemical reactions such as the oxidation of the electrolyte occurring on the cathode surface may contribute to the IRC of LiNi 1/3Mn 1/3Co 1/3O 2and LiCoO 2cathodesThe anodic peak at around 4.5 V in the first cycle becomes more prominent with decreasing synthesis temperature and disappears almost completely for the second cycle. This observation suggests that IRC is related to the anodic peak at 4.5 V.LiNi1/2Mn 1/4Co 1/4O 2nickel ‐rich the large irreversible anodic peak at around 4.5 Vp can be found only for the manganese ‐rich composition LiNi 1/4Mn 1/4Co 1/2O 2cobalt ‐rich chemical instability overlap of the metal:3d band with the top ofM C the oxygen:2p band lose oxygen from the latticedecreases in the order Co 3+/4+>Ni 3+/4+>Mn 3+/4+.LiNi 1/4Mn 1/2Co 1/4O 2manganese ‐richit is unclear whyonly the manganese ‐rich compositions areshowingthe large irreversible anodic peak at g g p 4.5 V.p yexhibiting a linear relationship with the BET surface area.i i l h i l ia parasitic electrochemical reaction occurring on the surface of the cathode materials may be responsible for the IRC.IRCbe related to an irreversible anodic peak at 4.5 Vpwhich increases with decreasing synthesis temperatureincreasing manganese contentSolid State Ionics 176 (2005) 2251 –2256我们感兴趣的问题是为什么要用Co掺杂？Co掺杂对其电化学性能有什么样的影响？用AAS 测定离子混杂程度也减小。

the top of the O2:2p band)那么2y<0.33 是容量保持度下降是什么因素引起的呢？掺入多少合适？l l i no clear correlationbetween electricald i i d conductivity and ratecapability with Co content.the lithium content (1‐x)increases with decreasing Co content in the region ofd i l0.15<2y<1.0 and remains nearly constant at low Co contents of 0<2y <0.15 indicating a faster lithium extraction rate with increasing Co content 2y.t ith i i C t tbe related to the increasing lithium extraction rate(为什么？)为什么小，锂离子迁移速率越大O O P Ni 0.5Mn 0.5O 2‐δO3O1P3Ni 0.425Mn 0.425Co 0.15O 2‐δM C Ni 0.33Mn 0.33Co 0.33O 2‐δδNi 0.295Mn 0.295Co 0.41O 2‐δA faster lithium extraction CoO 2‐δNi 0.25Mn 0.25Co 0.5O 2‐δresults in the formation of the metastable P3 type phase a moderately slow lithium extraction leads to thestabilization of the thermodynamically morestable O1 phaseCo co te t o033<2y<0.5 exhibit high capacity with good cyclability The rate capabilityp ydecreases with decreasing Co contentgThe decreasing lithium extraction rateto cause a change in the structure of the chemically delithiated phases Ni05Mn05y p0.5‐y0.5‐Co2‐y O2‐δfrom P3 to O1 to O3y667672Journal of Power Sources 162 (2006) 667–672LiNi0.5−y Co0.5−y Mn2y O2for 0≤2y≤0.8LiCo0.5−y Mn0.5−y Ni2y O2for 0≤2y≤1Li2MnOcompositions with 2y > 0.6 in LiNi0.5−y Co0.5−y Mn2y O2 2y < 0.2 in LiCo0.5−Mn0.5−Ni2y O2y y yAdditionally, the Ni-rich compositions encounter a volatilizationvolatilization of lithium at the high synthesis temperature .¾Compositions around 2y = 0.33 are found to be optimum with respect to maximizing the capacity values and retention.。