U.S. patent application number 17/005300 was filed with the patent office on 2020-12-17 for negative electrode of battery.
The applicant listed for this patent is AUO Crystal Corporation. Invention is credited to Chih-Hung CHAN, Rong-Ruey JENG, Han-Tu LIN, Kun-Fung LIN.
Application Number | 20200395601 17/005300 |
Document ID | / |
Family ID | 1000005051902 |
Filed Date | 2020-12-17 |
View All Diagrams
United States Patent
Application |
20200395601 |
Kind Code |
A1 |
LIN; Kun-Fung ; et
al. |
December 17, 2020 |
NEGATIVE ELECTRODE OF BATTERY
Abstract
A method for manufacturing silicon flakes includes steps as
follows. A silicon material is contacted with a machining tool
which includes at least one abrasive particle fixedly disposed
thereon. The silicon material is scraped along a displacement path
with respect to the machining tool to generate the silicon flakes
having various particle sizes.
Inventors: |
LIN; Kun-Fung; (Taipei City,
TW) ; JENG; Rong-Ruey; (Taoyuan City, TW) ;
LIN; Han-Tu; (Hsinchu County, TW) ; CHAN;
Chih-Hung; (Taoyuan City, TW) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
AUO Crystal Corporation |
Taichung City |
|
TW |
|
|
Family ID: |
1000005051902 |
Appl. No.: |
17/005300 |
Filed: |
August 27, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15869061 |
Jan 12, 2018 |
10797307 |
|
|
17005300 |
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|
14303620 |
Jun 13, 2014 |
9905845 |
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15869061 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01M 4/1395 20130101;
H01M 4/387 20130101; H01M 4/134 20130101; H01M 10/0525 20130101;
H01M 4/364 20130101; H01M 4/386 20130101 |
International
Class: |
H01M 4/1395 20060101
H01M004/1395; H01M 4/134 20060101 H01M004/134; H01M 4/36 20060101
H01M004/36; H01M 4/38 20060101 H01M004/38 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 16, 2013 |
TW |
102133528 |
Claims
1. A negative electrode of a battery, comprising: a plurality of
silicon scraps with a flake shape; and an active material, wherein
the silicon scraps are dispersed among the active material, and the
active material comprises silicon carbide.
2. The negative electrode of the battery of claim 1, wherein a
thickness of the silicon scrap is between 50 nm to 200 nm.
3. The negative electrode of the battery of claim 1, wherein a
particle size of the silicon scrap is in a range of 50 nm to 9
.mu.m.
4. The negative electrode of the battery of claim 3, wherein the
particle size of the silicon scrap is in a range of 50 nm to 300
nm.
5. The negative electrode of the battery of claim 1, wherein a
thickness of the silicon scrap is between 50 nm to 200 nm, and a
particle size of the silicon scrap is in a range of 50 nm to 300
nm.
6. The negative electrode of the battery of claim 1, wherein an
amount of the silicon scraps is equal to or greater than 5 parts by
weight based on 100 parts by weight of the negative electrode.
7. The negative electrode of the battery of claim 1, wherein the
active material comprises a carbon material.
8. The negative electrode of the battery of claim 7, wherein the
active material comprises a binder.
9. The negative electrode of the battery of claim 1, wherein the
active material comprises a plurality of kinds of carbon
materials.
10. The negative electrode of the battery of claim 7, wherein the
active material comprises graphite.
11. The negative electrode of the battery of claim 1, wherein the
active material comprises metal.
12. The negative electrode of the battery of claim 11, wherein the
metal is nickel.
13. The negative electrode of the battery of claim 8, wherein the
silicon scrap has a first surface along a long axis direction, and
the first surface of the silicon scrap is bonding with the
binder.
14. The negative electrode of the battery of claim 13, further
comprising a conductive agent mixing with the silicon scraps and
the binder.
15. The negative electrode of the battery of claim 1, wherein the
active material comprises a binder.
16. The negative electrode of the battery of claim 15, wherein the
silicon scrap has a first surface along a long axis direction, and
the first surface of the silicon scrap is bonding with the
binder.
17. The negative electrode of the battery of claim 16, further
comprising a conductive agent mixing with the silicon scraps and
the binder.
18. The negative electrode of the battery of claim 15, wherein the
active material comprises a plurality of kinds of carbon
materials.
19. The negative electrode of the battery of claim 18, wherein the
active material comprises graphite.
20. The negative electrode of the battery of claim 18, wherein the
active material comprises nickel.
Description
RELATED APPLICATIONS
[0001] The present application is a continuation of the application
Ser. No. 15/869,061, filed Jan. 12, 2018, which is a continuation
of the application Ser. No. 14/303,620, filed Jun. 13, 2014, U.S.
Pat. No. 9,905,845 issued on Feb. 27, 2018, which claims priority
to Taiwan Application Serial Number 102133528, filed Sep. 16, 2013,
which are herein incorporated by reference.
BACKGROUND
Technical Field
[0002] The present disclosure relates to a battery material and a
method for manufacturing the same. More particularly, the present
disclosure relates to an electrode material of a lithium ion
battery and a method for manufacturing the same.
Description of Related Art
[0003] In recent years, with the development of 3C electronics,
lightweight, mobile and high-energy batteries have attracted
considerable attention. Among the high-energy batteries, lithium
ion batteries have developed most maturely and been widely applied
to portable electronics. For example, a smart phone evolves not
only toward large size color screen, but also with more and more
complicated functionalities of photo shooting and music playing. As
a result, a demand for lightweight high-energy batteries is
increasing. How to increase a capacity and a cycle life of the
lithium ion batteries has become an important subject.
[0004] In the known technical solutions, a commonly used negative
electrode material of the lithium ion batteries is a graphite-based
material, such as a graphite carbon material. The graphite-based
material has an excellent charge and discharge capacity, and no
dendritic structure is generated, so that the graphite-based
material is safer in performance. However, the structure of the
negative electrode made of graphite-based material is spoiled due
to the reversibly insertion and detachment of lithium ions after a
number of charging and discharging cycles. Accordingly, the cycle
life of the lithium ion batteries is influenced. Furthermore, a
theoretical charge capacity of graphite is only about 372 mAh/g,
and the development of the lithium ion batteries is limited
thereby.
[0005] A lot of researches for improving the negative electrode
material of the lithium ion batteries have been provided. For
example, silicon material is mixed into the negative electrode of
the lithium ion batteries. A theoretical capacity of the silicon
material is about 4200 mAh/g, which is the highest among the
materials applied to the negative electrode of the lithium ion
batteries. However, a phase change is caused by the reversibly
insertion and detachment of lithium ions, and a volume expansion is
generated thereby. The volume expansion is so large that the
cycling stability and irreversibility of the silicon-containing
negative electrode of the lithium ion batteries are seriously
influenced.
[0006] Minimizing the particle sizes of the silicon material is one
of the solutions for controlling the volume expansion. For example,
the particle sizes of the silicon material are minimized to the
range of 10.about.300 nm. Although it is common to control the
volume expansion by minimizing the particle sizes of the silicon
material to the nanoscale. The silicon material in the form of
nanoscale particles is very expensive. Also, a significant
irreversible capacity is caused due to a larger surface area of the
nanoscale particles. Importantly, the nanoscale particles with
similar sizes and shapes tend to aggregate with each other to form
larger particles, and the process of uniformly mixing the materials
to form the negative electrode becomes more difficult.
[0007] A columnar silicon material for reducing the volume
expansion is disclosed. The particle sizes of the columnar silicon
material are in a range of 10 .mu.m to 800 .mu.m. The columnar
silicon material is formed by a chemical method including an
etching step and a nucleating step. However, the formed columnar
silicon material has to be removed from a substrate, such that the
chemical method has a high cost and low manufacturing rate.
Furthermore, the particle sizes of the columnar silicon material
are limited by the chemical method, and the consistency of the
sizes of the columnar silicon material intensifies the aggregation
of the columnar silicon material. Therefore, a subsequent
dispersion process is required for the columnar silicon
material.
[0008] Given the above, how to obtain an environmental friendly
silicon material, which is low cost and the volume expansion
thereof can be well controlled, has become the important subject
for the relevant industry of the lithium ion batteries.
SUMMARY
[0009] According to one aspect of the present disclosure, a method
for manufacturing silicon flakes includes steps as follows. A
silicon material is contacted with a machining tool. The machining
tool includes at least one abrasive particle fixedly disposed
thereon. The silicon material is scraped along a displacement path
with respect to the machining tool to generate a plurality of
silicon flakes having various particle sizes.
[0010] According to another aspect of the present disclosure, a
method for manufacturing a silicon-containing negative electrode of
a lithium ion battery includes steps as follows. A silicon material
is contacted with a machining tool. The machining tool includes at
least one abrasive particle fixedly disposed thereon. The silicon
material is scraped along a displacement path with respect to the
machining tool to generate a plurality of silicon flakes having
various particle sizes. The silicon flakes are consolidated to form
the silicon-containing negative electrode of the lithium ion
battery.
[0011] According to further another aspect of the present
disclosure, a silicon-containing negative electrode of a lithium
ion battery is disclosed. The silicon-containing negative electrode
of the lithium ion battery is manufactured by the aforementioned
method. The silicon-containing negative electrode of the lithium
ion battery includes the silicon flakes and an active material. An
amount of the silicon flakes is equal to or greater than 5 parts by
weight based on 100 parts by weight of the silicon-containing
negative electrode. The silicon flakes have various particle sizes
in a range of 50 nm to 9 .mu.m. The active material is graphite, a
metal element or a metal compound.
[0012] According to yet another aspect of the present disclosure, a
silicon-containing negative electrode of a lithium ion battery is
disclosed. The silicon-containing negative electrode of the lithium
ion battery is manufactured by the aforementioned method. The
silicon-containing negative electrode is substantially composed of
the silicon flakes. The silicon flakes have various particle sizes
in a range of 50 nm to 9 .mu.m.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] The disclosure can be more fully understood by reading the
following detailed description of the embodiment, with reference
made to the accompanying drawings as follows:
[0014] FIG. 1 is a flow diagram showing a method for manufacturing
a silicon-containing negative electrode of a lithium ion battery
according to one embodiment of the present disclosure;
[0015] FIG. 1A is a SEM (scanning electron microscope)
photomicrograph of a surface of a silicon material after constantly
scraped by a machining tool according to the method in FIG. 1 taken
at 20 times magnification;
[0016] FIG. 1B is a SEM photomicrograph of the surface of the
silicon material in FIG. 1A taken at 50 times magnification;
[0017] FIG. 1C is a SEM photomicrograph of the surface of the
silicon material in FIG. 1A taken at 100 times magnification;
[0018] FIG. 2 is a SEM photomicrograph of a plurality of silicon
flakes manufactured by the method in FIG. 1;
[0019] FIG. 3 shows a particle size distribution of the silicon
flakes manufactured by the method in FIG. 1;
[0020] FIG. 4 is a schematic view of a silicon-containing negative
electrode of a lithium ion battery according to one embodiment of
the present disclosure;
[0021] FIG. 5 is a partial enlarged schematic view showing a
microscopic state of FIG. 4;
[0022] FIG. 6A is a SEM photomicrograph of a silicon-containing
negative electrode of a lithium ion battery according to the 1st
example of the present disclosure;
[0023] FIG. 6B shows Coulombic efficiency and charge/discharge
capacity versus cycle number of the lithium ion battery according
to the 1st example;
[0024] FIG. 7A is a SEM photomicrograph of a silicon-containing
negative electrode of a lithium ion battery according to the 2nd
example of the present disclosure;
[0025] FIG. 7B shows voltage versus capacity of the 1st cycle to
the 5th cycle of the lithium ion battery according to the 2nd
example;
[0026] FIG. 7C shows Coulombic efficiency and charge/discharge
capacity versus cycle number of the lithium ion battery according
to the 2nd example;
[0027] FIG. 8 shows Coulombic efficiency and charge/discharge
capacity versus cycle number of the lithium ion battery according
to the 3rd example;
[0028] FIG. 9 shows Coulombic efficiency and charge/discharge
capacity versus cycle number of the lithium ion battery according
to the 4th example; and
[0029] FIG. 10 shows Coulombic efficiency and charge/discharge
capacity versus cycle number of the lithium ion battery according
to the 5th example.
DETAILED DESCRIPTION
[0030] <Method for Manufacturing Silicon Flakes of a
Silicon-Containing Negative Electrode of a Lithium Ion
Battery>
[0031] FIG. 1 is a flow diagram showing a method for manufacturing
a silicon-containing negative electrode 700 of a lithium ion
battery 600 according to one embodiment of the present disclosure.
FIG. 1A-FIG. 1C are SEM photomicrographs of a surface of a silicon
material 400 after constantly scraped by a machining tool according
to the method in FIG. 1, and FIG. 1A-FIG. 1C are taken at 20 times
magnification, 50 times magnification and 100 times magnification
respectively. FIG. 2 is a SEM photomicrograph of a plurality of
silicon flakes 500 manufactured by the method in FIG. 1. FIG. 3
shows a particle size distribution of the silicon flakes 500
manufactured by the method in FIG. 1. FIG. 4 is a schematic view of
the silicon-containing negative electrode 700 of the lithium ion
battery 600 according to one embodiment of the present
disclosure.
[0032] The method for manufacturing the silicon-containing negative
electrode 700 of the lithium ion battery 600 includes steps as
follows.
[0033] In Step 100, the silicon material 400 is contacted with the
machining tool, wherein the machining tool includes a plurality of
abrasive particle fixedly disposed thereon. For examples, the
machining tool can be a wire saw, a band saw or a grinding disc.
The abrasive particles can be natural diamonds, artificial
diamonds, cubic boron nitride, silicon carbide, aluminum oxide or
cerium oxide
[0034] In Step 200, the silicon material 400 is scraped along a
displacement path A (shown in FIG. 1A, FIG. 1B and FIG. 1C) with
respect to the machine tool to generate the silicon flakes 500
having various particle sizes. The displacement path A is a
straight line. As shown in FIG. 1A, FIG. 1B and FIG. 1C, a large
number of the silicon flakes 500 are generated, and the silicon
flakes 500 have various particle sizes. As shown in FIG. 2, a
thickness of each of the silicon flakes 500 along a short axis
thereof is 50 nm to 200 nm. The aforementioned "a short axis" means
that each of the silicon flakes 500 is substantially an oblong
flake and has a thickness, and the short axis is along a thickness
direction of the oblong flake. As shown in FIG. 3, a range of the
particle sizes of the silicon flakes 500 is about 50 nm to 9 .mu.m,
and the particle sizes of the silicon flakes 500 are concentrated
in a range of 300 nm to 2 .mu.m.
[0035] Furthermore, the displacement path A is not limited to a
straight line. In another embodiment, the displacement path A can
be a curve line. When the silicon material 400 is repeatedly
scraped by the machining tool, the machining tool can back and
forth scrape the silicon material 400 along the displacement path,
or the machining tool can scrape the silicon material 400 along the
displacement path in one way.
[0036] In Step 300, the silicon flakes 500 are consolidated to form
the silicon-containing negative electrode 700 of the lithium ion
battery 600. Therefore, the manufacturing costs of the
silicon-containing negative electrode 700 of the lithium ion
battery 600 are reduced via the mechanical method for manufacturing
the silicon flakes 500, and the problem of volume expansion is
preferably resolved via the inconsistencies of the particle sizes
and shapes of the silicon flakes 500. Furthermore, the aggregation
characteristic of the silicon flakes 500 can be reduced due to the
inconsistencies of the particle sizes and shapes of the silicon
flakes 500.
[0037] In Step 300, the silicon flakes 500 are used to form the
silicon-containing negative electrode 700 of the lithium ion
battery 600, which is only one of the applications of the silicon
flakes 500. In other embodiments, the silicon flakes 500 can be
used to manufacture other kinds of batteries.
<Method for Manufacturing a Silicon-Containing Negative
Electrode of A Lithium Ion Battery>
[0038] Please refer to FIG. 4, FIG. 5 and FIG. 6A. FIG. 5 is a
partial enlarged schematic view showing a microscopic state of FIG.
4. FIG. 6A is a SEM photomicrograph of a silicon-containing
negative electrode 700 of a lithium ion battery 600 according to
the 1st example of the present disclosure. In FIG. 4, the lithium
ion battery 600 includes the silicon-containing negative electrode
700, a positive electrode 800 and a separator 900. The
silicon-containing negative electrode 700 is opposite to the
positive electrode 800, and the separator 900 is disposed between
the silicon-containing negative electrode 700 and the positive
electrode 800. The silicon-containing negative electrode 700 is
manufactured by the aforementioned method. Specifically, the
silicon-containing negative electrode 700 includes the silicon
flakes 500, binders 720, conductive agents and active materials
710. The active materials 710 can be graphite, all kinds of carbon
materials, a metal element or a metal compound. The metal element
can be but not limited to tin, nickel, titanium, manganese, copper,
magnesium and a combination thereof. The metal compound can be but
not limited to titanium carbide, silicon carbide or titanate. In
the 1st example, the active materials 710 are graphite. The silicon
flakes 500, binders 720, conductive agents and active materials 710
are mixed in an appropriate proportion so as to form a uniform
mixture, and the uniform mixture is coated on a copper electrode
plate so as to form the silicon-containing negative electrode 700.
The electrolyte used in the lithium ion battery 600 can be but not
limited to LiPF.sub.6. The binders 720 can be CMC (carboxymethyl
cellulose), SBR (styrene-butadiene rubber) or PAA (polyacrylic
acid). The conductive agents can be but not limited to KS-6 or
Super-P.
[0039] Based on 100 parts by weight of the silicon-containing
negative electrode 700, an amount of the silicon flakes 500 is
equal to or greater than 5 parts by weight. Preferably, based on
100 parts by weight of the silicon-containing negative electrode
700, the amount of the silicon flakes 500 is 5 parts by weight to
80 parts by weight. More preferably, based on 100 parts by weight
of the silicon-containing negative electrode 700, the amount of the
silicon flakes 500 is 10 parts by weight to 20 parts by weight.
[0040] In the silicon-containing negative electrode 700, the
silicon flakes 500 are dispersed among the active materials 710.
Although a silicon material has a high theoretical capacity which
is up to 4200 mAh/g. However, the problem of volume expansion
exited in the silicon material endangers the performance of the
silicon material. The problem of volume expansion has been overcome
by the shapes and particle sizes of the silicon flakes 500
according to the present disclosure. The range of the particle
sizes of the silicon flakes 500 according to the present disclosure
is 50 nm to 9 .mu.m, and the thickness of each of the silicon
flakes 500 along the short axis thereof is 50 nm to 200 nm. As a
result, the amount of volume expansion (as the expanding directions
indicated by the arrows shown in FIG. 5) along a long axis
direction is reduced. Furthermore, each of the silicon flakes 500
has a larger surface for bonding with the binder 720. Therefore,
the generation of the cracks of the silicon-containing negative
electrode 700 due to volume expansion is reduced, and the capacity
of the lithium ion battery 600 is increased accordingly. In other
words, the capacity and the lifetime of the lithium ion battery 600
are both increased.
[0041] <Experiment Result of Lithium Ion Battery--1st
Example>
[0042] Please refer to FIG. 6A and FIG. 6B. FIG. 6B shows Coulombic
efficiency and charge/discharge capacity versus cycle number of the
lithium ion battery 600 according to the 1st example.
[0043] In the 1st example, based on 100 parts by weight of the
silicon-containing negative electrode 700, an amount of the silicon
flakes 500 is equal to 12 parts by weight. In FIG. 6B, the capacity
of the lithium ion battery 600 is measured by a battery automation
test system, and the model number of the battery automation test
system is BAT-750B. The charge-discharge tests are conducted for 40
cycles, and the charge-discharge tests are conducted under a fixed
charge/discharge rate of 0.1C and a cut-off voltage of 20
mV.about.1.2 V. The relationships between voltage and time are
recorded by a computer. In FIG. 6B, the QE value of the 1st cycle
is 77.7%. The charge capacity of the 1st cycle is 413.8 mAh/g, the
charge capacity of the 37th cycle is 450.7 mAh/g, and the capacity
retention of the 37th cycle is up to 108.9%.
[0044] <Experiment Result of Lithium Ion Battery--2nd
Example>
[0045] FIG. 7A is a SEM photomicrograph of a silicon-containing
negative electrode 700 of a lithium ion battery 600 according to
the 2nd example of the present disclosure. FIG. 7B shows voltage
versus capacity of the 1st cycle to the 5th cycle of the lithium
ion battery 600 according to the 2nd example. FIG. 7C shows
Coulombic efficiency and charge/discharge capacity versus cycle
number of the lithium ion battery 600 according to the 2nd
example.
[0046] In the 2nd example, based on 100 parts by weight of the
silicon-containing negative electrode 700, an amount of the silicon
flakes 500 is equal to 60 parts by weight. In FIG. 7B and FIG. 7C,
the capacity of the lithium ion battery 600 is measured by a
battery automation test system, and the model number of the battery
automation test system is BAT-750B. In FIG. 7B and FIG. 7C, the
charge-discharge tests are conducted for 5 cycles, and the
charge-discharge tests are conducted under a fixed charge/discharge
rate of 0.1C, and a discharge cut-off voltage of 20 mV, and a
charge cut-off voltage of 1200 mV. The relationships between
voltage and time are recorded by a computer. In FIG. 7C, the QE
value of the 1st cycle is 88%. The discharge capacity of the 1st
cycle is up to 3627 mAh/g, and the charge capacity of the 5th cycle
is still up to 2116 mAh/g.
[0047] <Experiment Result of Lithium Ion Battery--3rd
Example>
[0048] FIG. 8 shows Coulombic efficiency and charge/discharge
capacity versus cycle number of a lithium ion battery 600 according
to the 3rd example. In the 3rd example, based on 100 parts by
weight of the silicon-containing negative electrode 700, an amount
of the silicon flakes 500 is equal to 15 parts by weight.
Specifically, based on 100 parts by weight of the
silicon-containing negative electrode 700, the amount of the
silicon flakes 500 is equal to 15 parts by weight, an amount of an
active material 710 (in the example, the active material 710 is
carbon) is equal to 75 parts by weight, and an amount of a binder
730 is equal to 10 parts by weight. In FIG. 8, the capacity of the
lithium ion battery 600 is measured by a battery automation test
system, and the model number of the battery automation test system
is BAT-750B. In FIG. 8, the charge-discharge tests are conducted
under a fixed charge/discharge rate of 0.1C, and a cut-off voltage
of 20 mV-1.2 V. The relationships between voltage and time are
recorded by a computer. In FIG. 8, the charge capacity of the 1st
cycle is 517 mAh/g, the discharge capacity of the 1st cycle is 634
mAh/g, and the QE value of the 1st cycle is 81.5%. The charge
capacity of the 2nd cycle is 540 mAh/g, the discharge capacity of
the 2nd cycle is 598 mAh/g, and the QE value of the 2nd cycle is
90.3%. Furthermore, the charge capacity and the discharge capacity
of the 21th cycle are all greater than 300 mAh/g. It is obvious
that an excellent capacity can be provided by the lithium ion
battery 600 according to the present disclosure after a number of
cycles.
[0049] <Experiment Result of Lithium Ion Battery--4th
Example>
[0050] FIG. 9 shows Coulombic efficiency and charge/discharge
capacity versus cycle number of a lithium ion battery 600 according
to the 4th example. In the 4th example, based on 100 parts by
weight of the silicon-containing negative electrode 700, an amount
of the silicon flakes 500 is equal to 30 parts by weight.
Specifically, based on 100 parts by weight of the
silicon-containing negative electrode 700, the amount of the
silicon flakes 500 is equal to 30 parts by weight, an amount of an
active material 710 (in the example, the active material 710 is
carbon) is equal to 60 parts by weight, and an amount of a binder
730 is equal to 10 parts by weight. In FIG. 9, the capacity of the
lithium ion battery 600 is measured by a battery automation test
system, and the model number of the battery automation test system
is BAT-750B. In FIG. 9, the charge-discharge tests are conducted
under a fixed charge/discharge rate of 0.1C, and a cut-off voltage
of 20 mV-1.2 V. The relationships between voltage and time are
recorded by a computer. In FIG. 9, the charge capacity of the 1st
cycle is 860 mAh/g, the discharge capacity of the 1st cycle is 1015
mAh/g, and the QE value of the 1st cycle is 84.7%. The charge
capacity of the 2nd cycle is 878 mAh/g, the discharge capacity of
the 2nd cycle is 927 mAh/g, and the QE value of the 2nd cycle is
94.7%. Furthermore, the charge capacity and the discharge capacity
of the 21st cycle are all greater than 500 mAh/g. It is obvious
that an excellent capacity can be provided by the lithium ion
battery 600 according to the present disclosure after a number of
cycles.
[0051] <Experiment Result of Lithium Ion Battery--5th
Example>
[0052] FIG. 10 shows Coulombic efficiency and charge/discharge
capacity versus cycle number of a lithium ion battery 600 according
to the 5th example. In the 5th example, based on 100 parts by
weight of the silicon-containing negative electrode 700, an amount
of the silicon flakes 500 is equal to 60 parts by weight.
Specifically, based on 100 parts by weight of the
silicon-containing negative electrode 700, the amount of the
silicon flakes 500 is equal to 60 parts by weight, an amount of an
active material 710 (in the example, the active material 710 is
carbon) is equal to 30 parts by weight, and an amount of a binder
730 is equal to 10 parts by weight. In FIG. 10, the capacity of the
lithium ion battery 600 is measured by a battery automation test
system, and the model number of the battery automation test system
is BAT-750B. In FIG. 10, the charge-discharge tests are conducted
under a fixed charge/discharge rate of 0.1C, and a cut-off voltage
of 20 mV-1.2 V. The relationships between voltage and time are
recorded by a computer. In FIG. 10, the charge capacity of the 1st
cycle is 1726 mAh/g, the discharge capacity of the 1st cycle is
2086 mAh/g, and the QE value of the 1st cycle is 82.7%. The charge
capacity of the 2nd cycle is 1419 mAh/g, the discharge capacity of
the 2nd cycle is 1699 mAh/g, and the QE value of the 2nd cycle is
83.5%. Furthermore, the charge capacity and the discharge capacity
of the 21st cycle are all greater than 600 mAh/g. It is obvious
that an excellent capacity can be provided by the lithium ion
battery 600 according to the present disclosure after a number of
cycles.
[0053] Please refer to Table 1.
TABLE-US-00001 TABLE 1 Example 3rd 4th 5th amount of the silicon 15
30 60 flakes (wt %) cycle 1st 2nd 1st 2nd 1st 2nd discharge
capacity 634 598 1015 927 2086 1699 (mAh/g) charge capacity (mAh/g)
517 540 860 878 1726 1419 Coulombic efficiency (%) 81.5 90.3 84.7
94.7 82.7 83.5
[0054] As shown in Table 1, the Coulombic efficiency of the 1st
cycle doesn't decrease with the increase of the amount of the
silicon flakes 500. When a negative electrode of a conventional
lithium ion battery is added with spherical silicon powders in
micron scale, the Coulombic efficiency of the 1st cycle decreases
with the increase of the amount of the silicon flakes. It is
obvious that the loss of the Coulombic efficiency of the 1st cycle
can be suppressed by the flake shape and the particle sizes of the
silicon flakes 500 according to the present disclosure. When the
amount of the silicon flakes 500 is high as 60 parts by weight, the
Coulombic efficiency of the 1st cycle can be maintain at the high
value of 82.7%.
[0055] According to the aforementioned examples, the present
disclosure has advantages as follows.
[0056] First, the silicon flakes 500 are manufactured by a
mechanical method, so that the manufacturing costs are reduced, and
an inconsistency of particle sizes of the silicon flakes 500 is
generated accordingly.
[0057] Second, the problem of the volume expansion can be
effectively resolved by the flake shape and the various particle
sizes of the silicon flakes 500.
[0058] Third, the aggregation characteristic of the silicon flakes
500 can be reduced due to the inconsistencies of the particle sizes
and shapes of the silicon flakes 500, so that the capacity and the
life time of the lithium ion battery 600 can be increased
effectively.
[0059] It will be apparent to those skilled in the art that various
modifications and variations can be made to the structure of the
present disclosure without departing from the scope or spirit of
the disclosure. In view of the foregoing, it is intended that the
present disclosure cover modifications and variations of this
disclosure provided they fall within the scope of the following
claims.
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