A charging method, charging device and system for all-solid-state battery

Abstract

The present invention provides a charging method, a charging device and a system for an all-solid-state battery, wherein the charging method comprises: dividing the entire charging process into two parts according to the state of charge, wherein the range of the state of charge S1 in the first part is 0≤S1<W, and the range of the state of charge S2 in the second part is W≤S2<100%, where W is 40%-60%; the first part comprises n charging stages, and the charging rate of each charging stage is a n =(An 2 +B)×K, the charging end state of charge S of each charging stage 1n =(En‑F) / 100; the second part includes m charging stages, and the charging rate of each charging stage is b m =(‑Cm 2 + D) × K, the charging end state of charge S of each charging stage 2n =(Xm+Y) / 100; K is the preset initial average charging rate, 0<K≤a max , or 0<K≤b max During the charging process, the carrier concentration is adjusted in a targeted manner to adapt to the changes in internal resistance, which not only evens out the carrier transport and inhibits damage to the negative electrode, but also reduces impedance fluctuations, effectively improving the battery's fast charging capability.

Description

Technical Field

[0001] The present invention belongs to the technical field of all-solid-state batteries and relates to a charging method, a charging device and a system for an all-solid-state battery. Background Art

[0002] Social development has put forward new demands for energy storage systems. It is urgent to develop secondary batteries with high specific energy, high safety and long cycle life. However, on the one hand, the commercial lithium-ion batteries currently in use are close to their limit (260 Wh / kg), and on the other hand, the flammability of the electrolyte has also caused people's safety concerns. Based on this, people have proposed to use intrinsically non-flammable inorganic solid electrolytes instead of organic electrolytes to assemble all-solid-state batteries.

[0003] The core of all-solid-state batteries is solid electrolytes. The current mainstream solid electrolytes include oxide solid electrolytes, sulfide solid electrolytes and polymer solid electrolytes. These solid electrolytes have high ionic conductivity (>10 -4 S / cm) has attracted much attention. After continuous efforts by scientific researchers, although the ionic conductivity of solid electrolytes is comparable to that of liquid electrolytes, there are still many problems. For example, the poor solid-solid interface contact problem of oxide solid electrolytes, the electrochemical stability problem of sulfide solid electrolytes themselves, and the lithium dendrite growth problem of polymer solid electrolytes have all seriously restricted the large-scale application of all-solid-state batteries.

[0004] The charging method of the battery has an important impact on the battery performance. The existing charging methods for all-solid-state batteries often adopt a single constant current charging or constant voltage charging method. These methods often have problems such as poor rate performance and poor cycle stability due to the participation of solid electrolytes in electrochemical reactions and poor solid-solid interfaces during the charging process of all-solid-state batteries. Summary of the invention

[0005] In view of the problems in the prior art that the all-solid-state battery has poor rate performance and cycle stability due to the participation of solid electrolytes in electrochemical reactions and poor solid-solid interfaces during charging, the present invention provides a charging method, a charging device and a system for an all-solid-state battery. The charging method specifically adjusts the carrier concentration during the charging process to adapt to the change in internal resistance, which not only uniformizes the transport of carriers and suppresses damage to the negative electrode, but also reduces impedance fluctuations, effectively improving the fast charging capability of the battery.

[0006] To achieve this object, the present invention adopts the following technical solutions:

[0007] In a first aspect, the present invention provides a charging method for an all-solid-state battery, the charging method comprising:

[0008] The entire charging process is divided into two parts according to the state of charge. The range of the first part of the state of charge S1 is 0≤S1<W, and the range of the second part of the state of charge S2 is W≤S2<100%, where W is 40%-60%;

[0009] The first part includes n charging stages, and the charging rate of each charging stage is a n =(An 2 +B)×K, where A is 0.1-0.5, B is 0.2-0.7, and n≥1;

[0010] The charging end state of charge S of each charging stage 1n =(En-F) / 100, where E is 1-50 and F is 1-40;

[0011] The second part includes m charging stages, and the charging rate of each charging stage is b. m =(-Cm 2 + D) × K, where C is 0.1-0.7, D ​​is 1.5-3.5, and m ≥ 1;

[0012] The charging end state of charge S of each charging stage 2n =(Xm+Y) / 100, where X is 1-50 and Y is 1-90;

[0013] K is the preset initial average charging rate, 0<K≤a max , or 0<K≤b max .

[0014] As a preferred solution of the present invention, a constant current charging method is adopted in each charging stage in the first part, and a constant current charging method is adopted in each charging stage in the second part.

[0015] As a preferred embodiment of the present invention, the charging rate of the entire charging process shows a trend of first increasing and then decreasing.

[0016] As a preferred embodiment of the present invention, the value of n is 1≤n≤20.

[0017] As a preferred solution of the present invention, the value of m is 1≤m≤20.

[0018] In a second aspect, the present invention provides a charging device, the charging device comprising:

[0019] A charging rate determination unit and a charging unit;

[0020] The charging rate determination unit is used to determine the charging rates of the first part and the second part according to the preset initial average charging rate K and the charging method;

[0021] The charging unit is used to charge according to the determined charging rate.

[0022] In a third aspect, the present invention provides a charging system, which includes the aforementioned charging device.

[0023] In a fourth aspect, the present invention provides an all-solid-state battery, which is charged using the aforementioned charging method.

[0024] As a preferred embodiment of the present invention, the all-solid-state battery contains a metal element M, and the metal element M is selected from any one or more of Li, Na, K, Ca, Zn, Al, Mg, Ag, Fe, Sn or In.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] The charging method of the all-solid-state battery provided by the present invention can ensure that the concentration of lithium ions is regulated under fast charging conditions, the solid-solid interface is fully infiltrated, the impedance fluctuation during the cycle is reduced, and the polarization is reduced;

[0027] The charging method of the all-solid-state battery provided by the present invention can improve the cycle performance of the all-solid-state battery while maintaining a charging time similar to that of the current charging time. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The charging rate trend of the entire charging process of the charging method of the present invention;

[0029] Figure 2 It is a schematic diagram of the structure of the all-solid-state battery of the present invention;

[0030] Figure 3 This is a comparison chart of the cycle performance of the sulfide all-solid-state battery of Example 1 of the present invention and Comparative Example 1;

[0031] Among them, 1-positive electrode, 2-solid electrolyte, 3-negative electrode. DETAILED DESCRIPTION

[0032] In order to better illustrate the present invention and facilitate understanding of the technical solution of the present invention, the present invention is further described in detail below. However, the following embodiments are only simple examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention shall be subject to the claims.

[0033] In a first aspect, a specific embodiment of the present invention provides a charging method for an all-solid-state battery, the charging method comprising:

[0034] The entire charging process is divided into two parts according to the state of charge. The range of the state of charge S1 in the first part is 0≤S1<W, and the range of the state of charge S2 in the second part is W≤S2<100%, where W is 40%-60%, such as 40%, 45%, 50%, 55% or 60%, etc., but is not limited to the listed values. Other values ​​not listed in the numerical range are also applicable, preferably 45%-55%;

[0035] The first part includes n charging stages, and the charging rate of each charging stage is a n =(An 2 +B)×K, wherein A is 0.1-0.5, such as 0.1, 0.2, 0.3, 0.4 or 0.5, etc., but not limited to the listed values, other values ​​not listed in the numerical range are also applicable, preferably 0.15-0.45; B is 0.2-0.7, such as 0.2, 0.3, 0.4, 0.5, 0.6 or 0.7, etc., but not limited to the listed values, other values ​​not listed in the numerical range are also applicable, preferably 0.25-0.65; n≥1, such as 2, 3, 4, 5, 6 or 7, etc., but not limited to the listed values, other values ​​not listed in the numerical range are also applicable, preferably 1≤n≤20, and more preferably 2≤n≤15; the charge cut-off state of charge S of each charging stage 1n =(En-F) / 100, wherein E is 1-50, such as 10, 20, 30, 40 or 50, etc., but is not limited to the listed values, and other values ​​not listed in the numerical range are also applicable, preferably 5-45; F is 1-40, such as 10, 20, 30 or 40, etc., but is not limited to the listed values, and other values ​​not listed in the numerical range are also applicable, preferably 5-35;

[0036] The second part includes m charging stages, and the charging rate of each charging stage is b. m =(-Cm 2 +D)×K, wherein C is 0.1-0.7, such as 0.1, 0.2, 0.3, 0.4, 0.5, 0.6 or 0.7, etc., but not limited to the listed values, other values ​​not listed in the numerical range are also applicable, preferably 0.12-0.65; D is 1.5-3.5, such as 1.5, 2, 2.5, 3 or 3.5, etc., but not limited to the listed values, other values ​​not listed in the numerical range are also applicable, preferably 1.6-3.4; m≥1, such as 2, 3, 4, 5, 6 or 7, etc., but not limited to the listed values, other values ​​not listed in the numerical range are also applicable, preferably 1≤m≤20, and more preferably 2≤m≤15; the charge cut-off state of charge S of each charging stage 2n=(Xm+Y) / 100, wherein X is 1-50, such as 10, 20, 30, 40 or 50, etc., but is not limited to the listed values, and other values ​​not listed in the numerical range are also applicable, preferably 5-45; Y is 1-90, such as 10, 30, 50, 70 or 90, etc., but is not limited to the listed values, and other values ​​not listed in the numerical range are also applicable, preferably 5-85;

[0037] K is the preset initial average charging rate, 0<K≤a max , or 0<K≤b max Among them, the setting of K is mainly based on the initial average charging rate preset according to the actual situation of battery charging.

[0038] At present, in order to solve the anxiety about safety and battery life, people have proposed to use intrinsically safe solid electrolytes instead of liquid electrolytes to assemble all-solid-state batteries. However, the decomposition of solid electrolytes and solid-solid interface problems of all-solid-state batteries seriously limit their performance, especially in the case of fast charging. Specifically, it includes poor interfacial wettability at the beginning of charging, accumulation of decomposition byproducts of the electrolyte in the middle stage, and uneven deposition of lithium at the end stage. These problems will aggravate the growth of lithium dendrites and have an adverse effect on the performance of all-solid-state batteries. Based on this, the present invention provides a charging method for an all-solid-state battery, a charging device, and an all-solid-state battery using such a charging method.

[0039] The charging method of the present invention is mainly used to improve the solid-solid interface contact and the self-generated electrochemical decomposition of the solid electrolyte. The low rate in the initial stage is used to wet the interface; after the entire system runs smoothly, it switches to a high rate to ensure the rapid transport of ions; when the lithium ion concentration is low near the cut-off voltage, a low rate is used for uniform lithium plating. The charging method of the present invention specifically adjusts the carrier concentration during the charging process to adapt to the change of internal resistance, which not only uniformizes the transport of carrier ions, suppresses damage to the negative electrode, but also reduces impedance fluctuations, effectively improving the fast charging capability of the battery.

[0040] As a preferred solution of the present invention, a constant current charging method is adopted in each charging stage in the first part, and a constant current charging method is adopted in each charging stage in the second part.

[0041] In the present invention, a constant current charging method is adopted in each stage of charging, but the charging current in each stage is different.

[0042] As a preferred embodiment of the present invention, the charging rate of the entire charging process shows a trend of first increasing and then decreasing. Figure 1 shown.

[0043] In a second aspect, a specific embodiment of the present invention provides a charging device, the charging device comprising:

[0044] A charging rate determination unit and a charging unit;

[0045] The charging rate determination unit is used to determine the charging rates of the first part and the second part based on the aforementioned charging method according to a preset initial average charging rate K;

[0046] The charging unit is used to charge according to the determined charging rate.

[0047] In a third aspect, a specific embodiment of the present invention provides a charging system, which includes the aforementioned charging device.

[0048] In a fourth aspect, a specific embodiment of the present invention provides an all-solid-state battery, which is charged using the aforementioned charging method.

[0049] As a preferred embodiment of the present invention, the all-solid-state battery contains a metal element M, and the metal element M is selected from any one or more of Li, Na, K, Ca, Zn, Al, Mg, Ag, Fe, Sn or In.

[0050] The all-solid-state battery described in the present invention comprises a positive electrode, a negative electrode and a solid electrolyte, and the solid electrolyte is arranged between the positive electrode and the negative electrode.

[0051] The solid electrolyte in the all-solid-state battery described in the present invention includes any one of an oxide solid electrolyte, a sulfide solid electrolyte, a polymer solid electrolyte or a halide solid electrolyte, or a combination of at least two thereof.

[0052] Among them, the oxide solid electrolyte includes garnet-type Li7La3Zr2O 12 , Perovskite-type Li 0.33 La 0.56 TiO3 or NASICON type Li 1.3 Al 0.3 Ti 1.7 Any one or a combination of at least two of (PO4)3.

[0053] The sulfide solid electrolyte includes 70Li2S-P2S5, 75Li2S-P2S5, 80Li2S-P2S5, Li7P3S 11 , Li3PS4, Li6PS5Cl, Li6PS5Br, Li6PS5I, Li 11 Si2PS 12 , Li 10 Sn2PS 12 or Li 10 Ge2PS 12 Any one or a combination of at least two of the following.

[0054] The polymer solid electrolyte includes any one of PEO, PVDF, PVDF-HFP, PTFE, PI, PPC, PAN, PMMA or PDMS, or a combination of at least two thereof.

[0055] The halide solid electrolyte includes Li3InCl6, Li3YCl6, Li3YBr6, Li2ZrCl6, Li2Sr 0.67 Any one of Cl6 or LiAlCl4 or a combination of at least two thereof.

[0056] The positive electrode active material used in the positive electrode of the all-solid-state battery of the present invention includes a layered oxide (LiNi 1-x-y Co x Mn y O2、LiNi 1-x-y Co x Al y O2), polyanions (LiFePO4), lithium-rich oxides (Li2MnO3) or spinel oxides (LiMn2O4, LiNi 0.5 Mn 1.5 O2) any one or a combination of at least two.

[0057] The negative electrode active material used in the negative electrode of the all-solid-state battery described in the present invention includes any one or more of Li, Na, Al, Mg, Si, K, Ga, Fe, Zn, Ag, Y, Sb, In, Ti, Si or C.

[0058] The following are typical but non-limiting embodiments of the present invention:

[0059] The all-solid-state battery structures and preparation methods involved in the following embodiments 1-10 and comparative examples 1-2 of the present invention are as follows:

[0060] The all-solid-state battery comprises an NMC811 positive electrode 1, a Li6PS5Cl solid electrolyte 2 and a lithium metal negative electrode 3, and has a structure as follows Figure 2 shown.

[0061] The preparation method of the all-solid-state battery is as follows:

[0062] (1) NMC811 powder, Li6PS5Cl powder and carbon nanofiber (VGCF) were added into a ball mill at a mass ratio of 75:23:2, ball milled at a speed of 400 r / min for 2 h, and then sieved through a 300-mesh sieve to obtain a positive electrode mixture;

[0063] (2) The Li6PS5Cl powder was sieved with 300 mesh, and the sieved Li6PS5Cl powder was pressurized in a mold at a pressure of 200 MPa to obtain an electrolyte layer with a thickness of 500 μm;

[0064] (3) Placing the positive electrode mixture on one surface of the electrolyte layer, rotating the stainless steel cylindrical surface of the mold to flatten the positive electrode mixture, and applying pressure of 500 MPa to obtain a positive electrode active material layer;

[0065] (4) Place a suitably cut lithium metal negative electrode on the other surface of the electrolyte layer, use the stainless steel cylindrical surface of the mold to bring the lithium metal into close contact with the electrolyte layer, and pressurize at a pressure of 5 MPa to obtain an all-solid-state battery.

[0066] Examples 1-14 and Comparative Examples 1-2 use the aforementioned all-solid-state batteries and are charged using different charging methods. Embodiment 1:

[0067] The prepared all-solid-state battery was charged at 0.1 C for one cycle at 50°C, and then charged and discharged at room temperature. The charging method is as follows:

[0068] The entire charging process is divided into two parts according to the state of charge, the range of the first part of the state of charge S1 is 0≤S1<50%, and the range of the second part of the state of charge S2 is 50%≤S2<100%;

[0069] The first part includes 2 (n=2) charging stages, each of which has a charging rate of a. n =(An 2 +B)×K, where A=0.3, B=0.3; the charge end state of each charging stage S 1n =(En-F) / 100, where E is 30 and F is 10;

[0070] The second part includes 2 (m=2) charging stages, and the charging rate of each charging stage is b m =(-Cm 2 +D)×K, where C=0.4, D=2.1; the charge end state of charge S of each charging stage 2n =(Xm+Y) / 100, where X=20, Y=60;

[0071] The initial average charging rate K is 0.3C. Embodiment 2:

[0072] The charging method described in this embodiment is the same as that in Embodiment 1, except that: A=0.27, B=0.43, C=0.4, and D=2.1. Embodiment 3:

[0073] The charging method described in this embodiment is the same as that in Embodiment 1, except that: A=0.27, B=0.33, C=0.4, and D=2.1. Embodiment 4:

[0074] The charging method described in this embodiment is the same as that in Embodiment 1, except that: A=0.3, B=0.3, C=0.33, and D=1.83. Embodiment 5:

[0075] The charging method described in this embodiment is the same as that in Embodiment 1, except that: A=0.3, B=0.3, C=0.37, and D=2.07. Embodiment 6:

[0076] The charging method described in this embodiment is the same as that in Embodiment 1, except that A=0.23, B=0.47, C=0.4, and D=2.1. Embodiment 7:

[0077] The charging method described in this embodiment is the same as that in Embodiment 1, except that: A=0.3, B=0.3, C=0.4, and D=2.2. Embodiment 8:

[0078] The charging method described in this embodiment is the same as that in Embodiment 1, except that: A=0.3, B=0.2, C=0.33, and D=1.83. Embodiment 9:

[0079] The charging method described in this embodiment is the same as that in Embodiment 1, except that: A=0.3, B=0.2, C=0.3, and D=1.8.

[0080] Embodiment 10:

[0081] The charging method described in this embodiment is the same as that in Embodiment 1, except that: A=0.3, B=0.4, C=0.4, and D=2.2.

[0082] Embodiment 11:

[0083] The charging method described in this embodiment is the same as that in Embodiment 1, except that:

[0084] The first part includes 3 (n=3) charging stages, and the charging rate of each charging stage is a n =(An 2 +B)×K, where A=0.3, B=0.3; the charge end state of each charging stage S 1n =(En-F) / 100, where E is 20 and F is 10;

[0085] The second part includes 2 (m=2) charging stages, and the charging rate of each charging stage is b m =(-Cm 2 +D)×K, where C=0.4, D=2.1; the charge end state of charge S of each charging stage 2n =(Xm+Y) / 100, where X=20, Y=60.

[0086] Embodiment 12:

[0087] The charging method described in this embodiment is the same as that in Embodiment 11, with the only difference being: A=0.27, B=0.43, C=0.4, and D=2.1.

[0088] Embodiment 13: The charging method described in this embodiment is the same as that in Embodiment 1, except that:

[0089] The entire charging process is divided into two parts according to the state of charge, the range of the first part of the state of charge S1 is 0≤S1<40%, and the range of the second part of the state of charge S2 is 40%≤S2<100%;

[0090] The first part includes 2 (n=2) charging stages, each of which has a charging rate of a. n =(An 2 +B)×K, where A=0.3, B=0.3; the charge end state of each charging stage S 1n =(En-F) / 100, where E is 30 and F is 20;

[0091] The second part includes 3 (m=3) charging stages, and the charging rate b in each charging stage is m =(-Cm 2 +D)×K, where C=0.2, D=2; the charge end state of charge S of each charging stage 2n =(Xm+Y) / 100, where X=10, Y=70.

[0092] Embodiment 14:

[0093] The charging method described in this embodiment is the same as that in Embodiment 13, with the only difference being: A=0.27, B=0.43, C=0.2, and D=2.4.

[0094] Comparative Example 1:

[0095] The charging method used in this comparative example is: always charging at a constant current of 0.3 C.

[0096] Comparative Example 2:

[0097] The charging method described in this embodiment is the same as that in Embodiment 1, except that: A=-0.3, B=1.8, C=-0.4, and D=0.1.

[0098] The charging performance of Examples 1-14 and Comparative Examples 1-2 was tested under the following test conditions:

[0099] The test temperature was 25°C, the capacity obtained by the first charge was taken as the initial capacity, and the capacity of each cycle was compared with the initial capacity to obtain the capacity decay curve. The number of cycles at 25°C until the capacity retention rate reached 80% was recorded as the room temperature cycle performance of the all-solid-state battery. The test results are shown in Tables 1, 2 and 3.

[0100] The cycle performance of the all-solid-state battery of Example 1 and Comparative Example 1 is as follows Figure 3 shown.

[0101] Table 1: Charging parameters and performance test table of Examples 1-10 and Comparative Examples 1-2

[0102]

[0103] Table 2: Charging parameters and performance test table of Examples 11-12

[0104]

[0105] Table 3: Charging parameters and performance test table of Examples 13-14

[0106]

[0107] From Table 1 and Figure 3 It can be seen that in comparative example 1, which is a conventional constant current 0.3 C test, the number of cycles with 80% capacity retention is only 53 cycles, and the cycle performance is poor. This is because the current is large at the beginning of charging, the interface is not fully wetted, the side reactions increase, and the lithium ions are unevenly deposited, which seriously affects the cycle performance.

[0108] Comparative Example 2 uses a high rate in the early and final stages, and a low rate in the middle stage. The number of cycles with 80% capacity retention is only 22, and the cycle performance is the worst. This shows that we have successfully predicted the interface characteristics of all-solid-state batteries during the charging process.

[0109] Examples 1-14 are different combinations within the preferred range of the present invention, all of which show enhanced cycle stability. This shows that the charging method of the present invention specifically adjusts the carrier concentration during the charging process to adapt to the change of internal resistance, which not only uniformly transports the carriers, inhibits damage to the negative electrode, but also reduces impedance fluctuations, effectively improving the fast charging capability of the battery.

[0110] The applicant declares that the present invention illustrates the detailed process equipment and process flow of the present invention through the above-mentioned embodiments, but the present invention is not limited to the above-mentioned detailed process equipment and process flow, that is, it does not mean that the present invention must rely on the above-mentioned detailed process equipment and process flow to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of various raw materials of the product of the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A charging method for an all-solid-state battery, characterized in that: The charging method comprises: The entire charging process is divided into two parts according to the state of charge. The range of the state of charge S1 in the first part is 0≤S1<W, and the range of the state of charge S2 in the second part is W≤S2<100%, where W is 40%-60%; The first part includes n charging stages, and the charging rate of each charging stage is a n =(An 2 +B)×K, where A is 0.1-0.5, B is 0.2-0.7, n≥2; the charge end state of each charging stage S 1n =(En-F) / 100, where E is 1-50 and F is 1-40; The second part includes m charging stages, and the charging rate of each charging stage is b. m =(-Cm 2 +D)×K, where C is 0.1-0.7, D ​​is 1.5-3.5, m≥2; the charge end state of each charging stage S 2n =(Xm+Y) / 100, wherein X is 1-50, Y is 1-90; K is the preset initial average charging rate, 0<K≤a max , or 0<K≤b max ; The charging rate of the entire charging process shows a trend of first increasing and then decreasing.

2. The charging method according to claim 1, characterized in that: A constant current charging method is adopted in each charging stage in the first part, and a constant current charging method is adopted in each charging stage in the second part.

3. The charging method according to claim 1, characterized in that: The value of n is 2≤n≤20.

4. The charging method according to claim 1, characterized in that: The value of m is 2≤m≤20.

5. A charging device, characterized in that: The charging device comprises: A charging rate determination unit and a charging unit; The charging rate determination unit is used to determine the charging rates of the first part and the second part according to a preset initial average charging rate K based on the charging method according to any one of claims 1 to 4; The charging unit is used to charge according to the determined charging rate.

6. A charging system, characterized in that: The charging system comprises the charging device according to claim 5.

7. An all-solid-state battery, characterized in that: The all-solid-state battery is an all-solid-state battery obtained by charging using the charging method described in any one of claims 1 to 4.

8. The all-solid-state battery according to claim 7, characterized in that: The all-solid-state battery contains a metal element M, and the metal element M is selected from any one or more of Li, Na, K, Ca, Zn, Al, Mg, Ag, Fe, Sn or In.

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