LITHIUM SUPPLEMENT FOR LITHIUM SECONDARY BATTERY, PREPARATION METHOD THEREOF, AND LITHIUM SECONDARY BATTERY, BATTERY MODULE, BATTERY PACK, AND APPARATUS

1 . A lithium supplement for lithium secondary batteries, wherein the lithium supplement comprises a compound L having a molecular formula of Li x Ni a Cu 1-a-b M b O 2 , wherein 1≤x≤2, 0<a<1, and 0≤b<0.1, and M is selected from one or more of Zn, Sn, Mg, Fe, and Mn;

wherein an XRD pattern of the lithium supplement shows a first diffraction peak at a diffraction angle 2θ of 42°-44° and a second diffraction peak at a diffraction angle 2θ of 25°-27°, a diffraction intensity of the first diffraction peak is I 1 , a diffraction intensity of the second diffraction peak is I 2 , and I 1 /I 2 <0.1% holds, and

wherein the first diffraction peak corresponds to a diffraction peak of nickel oxide on a (200) crystal plane, and the second diffraction peak corresponds to a diffraction peak of the compound L on a (100) crystal plane.

2 . The lithium supplement according to claim 1 , wherein based on total weight of the lithium supplement, a percentage of free lithium contained in the lithium supplement is ≤5 wt %.

3 . The lithium supplement according to claim 2 , wherein the free lithium comprises Li 2 CO 3 and LiOH.

4 . The lithium supplement according to claim 1 , wherein pH of the lithium supplement is denoted as pH L , and 11≤pH L ≤13.

5 . The lithium supplement according to claim 1 , wherein a water concentration of the lithium supplement is not higher than 800 ppm.

6 . The lithium supplement according to claim 1 , wherein a median particle size by volume D v 50 of the lithium supplement is 2 μm-10 μm.

7 . The lithium supplement according to claim 1 , wherein, in the molecular formula of the compound L, 0.1≤a≤0.9.

8 . The lithium supplement according to claim 1 , wherein the compound L is one selected from the group consisting of Li 2 Ni 0.1 Cu 0.9 O 2 , Li 2 Ni 0.2 Cu 0.8 O 2 , Li 2 Ni 0.3 Cu 0.7 O 2 , Li 2 Ni 0.4 Cu 0.6 O 2 , Li 2 Ni 0.5 Cu 0.5 O 2 , Li 2 Ni 0.6 Cu 0.4 O 2 , Li 2 Ni 0.7 Cu 0.3 O 2 , Li 2 Ni 0.8 Cu 0.2 O 2 , Li 2 Ni 0.9 Cu 0.1 O 2 , and Li 2 Ni 0.4 Cu 0.55 Mg 0.05 O 2 .

9 . The lithium supplement according to claim 1 , wherein the lithium supplement further comprises a coating material on at least partial surface of the compound L, and the coating material is selected from one or more of metal fluoride, oxide, and phosphate; and

the metal fluoride is selected from AlF 3 ; the oxide is selected from one or more of V 2 O 5 , Al 2 O 3 , ZrO 2 , TiO 2 , ZnO, SiO 2 , and B 2 O 3 ; and the phosphate is selected from one or more of AlPO 4 , FePO 4 , Co 3 (PO 4 ) 2 , and Ni 3 (PO 4 ) 2 .

10 . A preparation method of the lithium supplement for lithium secondary batteries according to claim 1 , the method comprising the following steps:

S1: weighing a lithium source, a nickel source, a copper source, and an M source, and mixing them and then performing ball milling, wherein a molar ratio of Li, Ni, Cu, and M is c:a:(1-a-b):b, 2≤c≤3, 0<a<1, and 0≤b<0.1, and M is selected from one or more of Zn, Sn, Mg, Fe, and Mn; and

S2: sintering the ball-milled mixture to obtain the lithium supplement.

11 . A lithium secondary battery, wherein the lithium secondary battery comprises a positive electrode containing the lithium supplement according to claim 1 ; and

based on a total mass of a positive electrode active substance, a mass percentage of the lithium supplement is 0.1 wt %-10 wt %.

12 . The lithium secondary battery according to claim 11 , wherein the positive electrode active substance comprises at least one of the compounds expressed by formula (I) to formula (III):

Li 1+x1 Ni a1 Co b1 M′ 1-a1-b1 O 2-y1 A y1   (I);

Li 1+x2 Mn a2 M″ 2-a2 O 4-d A′ d   (II); and

LiFe (1-x3-y3) Mn x3 M′″ y3 PO 4   (III),

wherein in the formula (I), −0.1≤x1≤0.2, 0<a1<1, 0≤b1≤1, 0<a1+b1<1, and 0≤y1<0.2, M′ is one or more of Mn, Fe, Cr, Ti, Zn, V, Al, Zr, and Ce, and A comprises one or more of S, N, F, Cl, Br, and I;

wherein in the formula (II), −0.1≤x2≤0.2, 0<a2≤2, and 0≤d<1, M″ comprises one or more of Ni, Fe, Cr, Ti, Zn, V, Al, Mg, Zr, and Ce, and A′ comprises one or more of S, N, F, Cl, Br, and I;

wherein in the formula (III), 0≤x3≤1 and 0≤y3≤0.1, and M′″ is selected from one or more of transition metal elements other than Fe and Mn and non-transition metal elements.

13 . The lithium secondary battery according to claim 12 , wherein when the positive electrode active substance contains the compound expressed by the formula (I), pH of the compound expressed by the formula (I) is denoted as pH c , pH of the lithium supplement is denoted as pH L , and pH c ≤pH L .

14 . A battery module, comprising the lithium secondary battery according to claim 11 .

15 . A battery pack, comprising the battery module according to claim 14 .